By HUNGURIMANA Dieudonne

January, 2016

Prepared by HUNGURIMANA Dieudonné, 0788473140 i

About the author

HUNGURIMANA Dieudonné teaches biology at ENDP

KARUBANDA. He has a Bachelor’s degree in Biology from the
National University of Rwanda since 2007. He has been teaching
Biology and chemistry in different secondary schools of Rwanda.
He has taught at Complexe Scolaire de la Fraternité, Collège
Saint Fidèle, Groupe Scolaire Notre Dame d’Afrique de Nyundo,
Collège Saint Wenceslas and Petit Seminaire de Nyundo. He has
an experience of teaching Biology of A level of seven years. He
has written four books of biology for A level: Biology for S4,
Biology for S5, Biology for S6 and A review of biology of A level with
questions and answers.

E-mail: hungurimana@yahoo.fr

Phone: +250788473140 / +250728473140

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Table of contents

Part I: The review of chapters with questions .................................................................................... 1

Chapter 1: Classification of livings ................................................................................................... 1
Chapter 2: The kingdom plantae ..................................................................................................... 2
Chapter 3: The kingdom fungi ........................................................................................................ 2
Chapter 4: The kingdom protista ..................................................................................................... 3
Chapter 5: Bacteria and viruses ...................................................................................................... 5
Chapter 6: KINGDOM ANIMALIA ..................................................................................................... 6
Chapter 7: CYTOLOGY ................................................................................................................ 10
Chapter 8: The nucleic acids, protein synthesis and cell divisions............................................................ 15
Chapter 9: Plant histology ........................................................................................................... 21
Chapter 10: Animal histology ....................................................................................................... 24
Chapter 11: Microbiology and hygiene ........................................................................................... 26
Chapter 12: Chemicals of life ....................................................................................................... 29
Chapter 13: Autotrophic nutrition ................................................................................................. 34
Chapter 14: Physiology of the nervous system .................................................................................. 42
Chapter 15: sense organs ............................................................................................................ 46
Chapter 16: Endocrinology .......................................................................................................... 49
Chapter 17: Homeostasis, excretion and thermoregulation .................................................................. 52
Chapter 18: Respiration and gas exchange ....................................................................................... 59
Chapter 19: Transport in animals .................................................................................................. 65
Chapter 20: Heterotrophic nutrition .............................................................................................. 74
Chapter 21: Reproduction and human development ........................................................................... 78
Chapter 22: Support and movement .............................................................................................. 82
Chapter 23: Genetics ................................................................................................................. 86
Chapter 24: Ecology .................................................................................................................. 93
Chapter 25: Evolution ................................................................................................................ 97
Part II: Answers of the questions .................................................................................................. 99
Chapter 1: Classification of livings ................................................................................................. 99
Chapter 2: The kingdom plantae ................................................................................................. 100
Chapter 3: The kingdom fungi .................................................................................................... 103
Chapter 4: The kingdom protista ................................................................................................. 104
Chapter 5: Bacteria and viruses .................................................................................................. 105

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Chapter 6: KINGDOM ANIMALIA ................................................................................................. 107
Chapter 7: CYTOLOGY .............................................................................................................. 110
Chapter 8: The nucleic acids, protein synthesis and cell divisions.......................................................... 115
Chapter 9: Plant histology ......................................................................................................... 120
Chapter 10: Animal histology ..................................................................................................... 123
Chapter 11: Microbiology and hygiene ......................................................................................... 126
Chapter 12: Chemicals of life ..................................................................................................... 130
Chapter 13: Autotrophic nutrition ............................................................................................... 136
Chapter 14: Physiology of the nervous system ................................................................................ 142
Chapter 16: Endocrinology ........................................................................................................ 147
Chapter 17: Homeostasis, excretion and thermoregulation ................................................................ 150
Chapter 18: Respiration and gas exchange ..................................................................................... 156
Chapter 19: Transport in animals ................................................................................................ 162
Chapter 20: Heterotrophic nutrition ............................................................................................ 166
Chapter 21: Reproduction and human development ......................................................................... 169
Chapter 22: Support and movement ............................................................................................ 172
Chapter 23: Genetics ............................................................................................................... 175
Chapter 24: Ecology ................................................................................................................ 182
Chapter 25: Evolution .............................................................................................................. 185
Part III: Overview of the classification of livings ............................................................................. 187

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Part I: The review of chapters with questions

Chapter 1: Classification of livings

1.1. A review of the chapter

 Taxonomy is the science of grouping organisms according to their morphology and evolutionary history.

 Carolus Linnaeus originated a seven-sevel hierarchy system for classifying organisms according to their
morphology. Moving from the most general to the most specific, the levels are called kingdom, phylum,
class, order, family, genus and species.

 A species name consists of the genus name together with a species identifier.

 Many modern taxonomists use the six-kingdom system of classification, which recognizes the unique nature
of the archaebacteria.

 A species (the smallest taxon) is a group of organisms which have numerous detailed features in common
and are able to interbreed (sexual reproduction) and do not normally breed with other species.

 Binomial nomenclature is a two-term naming system used for classifying organisms and was also introduced
by Linnaeus. Each organism is given a two word Latin name. The first name is a generic name which
describes the genus to which an organism belongs followed by the specific name which is the name of
species to which an organism belongs.
 The six kingdoms are classified into three domains which are: domain archae: takes the kingdom
archaebacteria, domain bacteria: takes the kingdom eubacteria, domain Eukarya: consists of protists,
fungi, plants and animals. All have true nuclei and membrane bound organelles.

1.2. Exercices

1. Explain the binomial system of nomenclature.

2. What is the meaning of the term species?
3. How did Aristotle classify organisms, and why did his method prove inadequate?
4. What criterion did Linnaeus use to classify organisms?
5. What are the seven levels of organization that Linnaeus used to categorize organisms?
6. What are two reasons that species names are more precise than common names?
7. State the six kingdoms of life, one characteristic and an example for each.
8. Define the following branches of biology
a) Botany d) Cytology
b) Entomology e) Histology
c) Ornithology f) Anatomy
9. What are the three domains of life?
10. Why do protists, fungi, plants, and animals share a domain in the six-kingdom system?
11. What criterion do modern taxonomists use to classify organisms?
12. Which eukaryotic kingdoms contain:
a) Autotrophic organisms
b) Heterotrophic organisms
c) Make a table to compare the features of the four kingdoms of eukaryotes.

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Chapter 2: The kingdom plantae

2.1. A review of the chapter

 Plants have a life cycle called alternation of generations, in which a multicellular haploid gametophyte stage
alternates with a multicellular diploid sporophyte stage.

 Mosses and most ferns are homosporous (produce only one type of spores).

 In the moss life cycle, a spore develops into a leafy green gametophyte that produces eggs in archegonia and
swimming sperm in antheridia. A moss sporophyte grows from a gametophyte and is dependent on it for
nourishment.

 In the fern life cycle, a spore develops into a small flat gametophyte that produces eggs in archegonia and
swimming sperm in antheridia. A sporophyte grows from a gametophyte but later crushes it and is not
dependent on it for nourishment.

 Gymnosperms have no flowers; their seeds are formed inside the cones.

 Flowers are reproductive structures of angiosperms. Most familiar flowers consist of four whorls of parts:
protective sepals, colorful petals, pollen-producing stamens and egg-containing carpels.

 Many flowering plants have flowers adapted for animal pollination or for wind pollination.

 Double fertilization is a unique feature of angiosperms. Two sperm reach the embryo through the pollen tube.
One sperm combines with the egg to form a zygote. A second sperm combines with two polar nuclei to form
a triploid nutritive tissue, the endosperm.

 Angiosperm seeds are enclosed by fruits, which protect seeds and aid in dispersion.

 Seeds need water, oxygen, suitable temperatures, and sometimes light to germinate.

2.2. Exercices
1. Define the following:
a) Phyllotaxis c) Zoochory
b) Anemogamy d) Inflorescence
2. What are two important differences between the life cycle of a typical fern and that of a seed plant?
3. State two differences between the sporophyte and gametophyte generation.
4. How does the process of fertilization in conifers differ from the process of fertilization in flowering plants?
5. Explain the process of double fertilization in flowering plants.
6. Draw a flower and show its main parts.
7. Following the self-pollination of some plants, the pollen tubes die before reaching ovules. What is the
significance of this event?
8. List three types of seed dispersal, and give an example of each.
9. Compare asexual reproduction with sexual reproduction in terms of their advantages and disadvantages.
10. List four factors that promote successful wind pollination.
11. State four differences between monocots and dicots.
12. What are the main differences between gymnosperms and angiosperms?
13. Explain the life cycle of ferns.
14. Compare the life cycle of a fern with that of a moss.
15. Draw a mature ovule and show its main parts.

Chapter 3: The kingdom fungi

3.1. A review of the chapter

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  Fungi are eukaryotic, non photosynthetic organisms that can be unicellular or multicellular.

 Fungi are among the most important decomposers of organic matter in the soil. Fungi secrete extracellular
enzymes that digest material and absorb simple organic molecules from the environment.

 Hyphae are tangled masses of fungal filamants. Some species have partitions called septa in their hyphae that
separate the individual cells.

 The phylum Basidiomycota includes mushrooms. Mushrooms or basidiocarps, are sexual reproductive
structures.

 The phylum Zygomycota includes the molds and Penicillium species.

 The phylum Ascomycota includes the yeasts. These fungi are called sac fungi. Yeast are unicellular
Ascomycota. They reproduce asexually by budding. Yeast are used for brewing, baking, and genetic
engineering.

 Mycorrhizae are symbiotic relationships between plant roots and fungi. Fungi provide nutrients to the plant and
derive nutrients from the plant.

 Lichens represent symbiotic relationships between fungi and cyanobacteria, or green algae. Fungi dissolve
nutrients from rock. Algae and cyanobacteria provide fungi with carbohydrates. Lichens are highly sensitive
to environmental changes.

 Fungi cause diseases such as athlete’s foot, ringworm, and jock itch, and these diseases are easily spread.

 Some fungi are edible while others are poisonous.

 In industry, fungi produce antibiotics, fuels, and foods. Yeasts are also valuable genetic engineering research
tools.

3.2. Exercices

1. State 2 advantages and 2 disadvantages of fungi.

2. Define the following:
a) Lichen
b) Mycorrhiza
c) Mycelium
3. State three differences between plants and fungi.
4. Explain how fungi compete with humans for nutrients.
5. List three types of foods that are derived from fungi.
6. Which fungi cause athlete’s foot and vaginal yeast infection?
7. Explain why lichens are important in environment?
8. Explain the benefits plants and fungi derive from a mycorrhizal relationship.
9. How do fungi obtain nutrients?
10. What characteristic makes fungi an important resource recycler?
11. Long before antibiotics were discovered, it was common practice to place a piece of moldy bread on wounds.
Explain why this practice might have helped the wounds heal.
12. What is the ecological importance of fungi?
13. Fungi are classified in their own kingdom. Into which phyla is the fungi kingdom divided? Into which of
those phyla are mushrooms classified?

Chapter 4: The kingdom protista

4.1. A review of the chapter

 The kingdom Protista includes algae, protozoa, slime molds and water molds.

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  Algae are mostly aquatic organisms that contain chlorophyll. Algae include microscopic single cells and giant
marine kelps.

 Algae produce large amounts of organic matter, which serves as nutrients for other organisms. Algae also add
an enormous amount of oxygen to the atmosphere.

 Algae can be classified into seven phyla, based on color, type of chlorophyll, and form of food-storage
substances.

 Protozoa are unicellular eukaryotic organisms classified in the kingdom Protista. They are found in moist
habitats, and they include free-living and parasitic forms. Most species of protozoa are heterotrophic
organisms that obtain nutrients by the process of phagocytosis.

 Many species of protozoa have adaptations for responding to changes in the environment. Such adaptations
include eyespots and cyst formation.

 Protozoa are placed into four groups or phyla according to the type of locomotion they display. The sarcodines
move by means of pseudopodia, the ciliates move by means of cilia, the zooflagellates move by means of
flagella, and the sporozoans are unable to move in the adult form.

 The phylum Ciliophora consists of protozoa that move by means of cilia. Ciliates include the well-studied
Paramecium. Paramecia have a complex array of organelles, including a macronucleus, a micronucleus, an
oral groove, and an anal pore.

 The phylum zoomastigina consists of protozoa that move by means of flagella. Zooflagellates include
Trypanosoma, a species that cause African sleeping sickness.

 The phylum Sporozoa is made up of protozoa that have complex life cycles in which they develop a spore.
Virtually all species of sporozoans are parasites in humans and other animals.

 The sporozoan Plasmodium causes the disease malaria. Plasmodium has a complex life cycle. The Anophele
mosquito transmits the parasite, which causes extensive damage to the red blood cells in the victim.

4.2. Questions
1. Which are the groups of living beings that form the protist kingdom?
2. In what ways do algae differ from protozoa?
3. How are algae similar to plants? How are they different?
4. What are the characteristics of protozoa that make them resemble animals?
5. What characteristics are used to classify algae into seven phyla?
6. What is a diatom? What useful commercial products do the shells of these algae yield?
7. Why are euglenoids described as both plant-like and animal-like organisms? Explain how euglenoids can be
both hetrotrophic and autotrophic?
8. What is the commercial importance of algae?
9. What is a cyst? Under what conditions might certain protozoa form cysts?
10. What is conjugation? How is this process advantageous for ciliates, such as Paramecium?
11. Describe the life cycle of Plasmodium, the sporozoan that causes malaria.
12. How does a ciliate, such as Paramecium, capture and digest food.
13. Draw a simplified life cycle of Plasmodium, showing the protozoan activity in both the mosquito and the
human hosts.
14. What are the respective functions of the macronucleus and of the micronucleus in the paramecium?

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Chapter 5: Bacteria and viruses

5.1. A review of the chapter

 Bacteria are single-celled organisms. They occur in several variations of three basic shapes: rods or bacilli,
spheres or cocci and spirals.

 Bacteria are classified in two kingdoms: Archaebacteria, which includes ancient forms of life, and Eubacteria,
which includes most bacteria.

 The archaebacteria include the methanogens, which produce methane gas; the extreme halophiles, which live
in very salty environments; and the thermoacidophiles, which live in extremely acidic environments at
extremely high temperatures.

 The gram stain is used to group bacteria into two groups: Gram-positive and Gram-negative bacteria.

 Many bacteria are pathogens. Diseases may result from toxins produced by bacteria, from the destruction of
body tissues, or from bacterial enzymes interfering with normal body processes.

 Antibiotics inhibit the growth of bacteria. Antibiotic-resistant bacteria destroy antibiotics, or prevent entry of
the antibiotic into the cytoplasm.

 Helpful bacteria are used to convert sewage into simpler organic compounds, to produce and process food, to
produce industrial chemicals, to mine for minerals, to produce insecticides, and to clean up chemicals and oil
spills.

 Viruses are biological particles composed of nucleic acid and a protein coat. Enveloped viruses also have a
membrane enclosing them.

 Viruses are not usually considered living organisms because they lack most of the characteristics of living
things.

 Replications of viruses occur by either the lytic or the lysogenic cycle.

 During the lytic cycle, the viral genome is released into the host cell, and replication of the virus follows
immediately. Cellular components are used to make new viruses. A viral enzyme then causes host cell lysis
and death.

 HIV infects specific white blood cells and remains in them as proviruses. As the immune system begins to fail,
opportunistic infections occur; this condition is called AIDS.

 In the lysogenic cycle, the nucleic acid of the virus becomes part of the host cell’s chromosome and remains
with the cell in this form for many generations. HIV follows this pattern.

5.2. Questions

1. What are bacteria?

2. Are bacteria the only prokaryotic beings?
3. What are the main ecological roles of bacteria?
4. What are some examples of human diseases caused by bacteria?
5. What are some industrial processes that use bacteria?
6. In which environments do bacteria live?
7. What is the main constituent of the cell wall of bacteria?
8. What are plasmids? What is the importance of plasmids for the recombinant DNA technology? Explain how
the terms bacteria, eubacteria and archaebacteria relate to one another.
9. Distinguish between Gram-positive and gram-negative bacteria.
10. What is the basic structure of a virus?

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 11. Are there non-parasitic viruses?
12. What is the genetic material of a virus? How does that material act in viral reproduction?
13. What is the typical reproduction cycle of a DNA virus?
14. What are retroviruses? How do they reproduce and what is the role of the enzyme reverse transcriptase?
15. What is the basic structure of the HIV virus? What is the function of the glycoproteins of its envelope?
16. What are the main human diseases caused by virus?
17. Discuss the activities of a virus during the lytic cycle?

Chapter 6: KINGDOM ANIMALIA

6.1. A review of the chapter

 Animals are multicellular and heterotrophic, and their cells lack walls. Most animals reproduce sexually and
can move.

 Animals have cells that are specialized for different functions.

 Invertebrates have no body symmetry or are radially symmetrical or bilaterally symmetrical; vertebrates are
bilaterally symmetrical.

 Some invertebrates have an exoskeleton. All vertebrates have an endoskeleton.

 The simplest invertebrates have no circulatory system. Arthropods and some mollusks have an open circulatory
system. Other mollusks, annelids, and vertebrates have a closed circulatory system.

 Sponges digest food within individual cells. Cnidarians digest food in a central chamber. Other invertebrates
and all vertebrates have a gut.

 Most invertebrates and vertebrates are capable of some form of sexual reproduction, and some invertebrates
can also reproduce asexually.

 During the first cell divisions in the zygote, called cleavage, cells divide repeatedly.

 The mass of cells produced by cleavage continues to divide, producing the blastula.

 During gastrula formation, the germ layers: the ectoderm, the mesoderm and in most phyla, the mesoderm are
defined.

 In protostomes, the first opening of the gastrula develops into the mouth while in deuterostomes it develops
into the anus.

 Acoelomates have no body cavity, Pseadocoelomates have a body cavity partially lined with mesoderm, and
coelomates have a coelom.

6.2. Exercices
1. How are sponges different to cnidarians?
2. What are the three classes of fishes and an example for each?
3. Classify the following organisms into their phyla and classes:
a) Mouse e) Snail
b) Bee f) Earthworm
c) Frog g) hydra
d) Snake
4. The Latin name for a house cat is Felis domesticus. Using this information and your knowledge of
classification, fill in the gaps in the table below.

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 Kingdom
Phylum
Class Mammalia
Order Carnivora
Family Canidae
Canis
Domesticus

5. State the characteristics common to all chordates.

6. Give an example of an invertebrate chordate.
7. Look carefully the specimen below:

a) Make a dichotomous key for these animal specimen

b) Which of these specimens are triploblastic coelomate animals?
8. Complete the table below about the classification of livings:
Livings Class Phylum Kingdom
Goat
Squid
Planarian
Cockroach
Paramecium -
Saccharomyces -
cerevisiae
Escherchia coli - -
9. State two advantages of the coelom.
10. What are the main differences between flatworms and annelids?
11. What is the difference between flatworms and roundworms?
12. What is the advantage of the exoskeleton of insects? What are its disadvantages?
13. What are the three subclasses of the class mammalia?
14. What is the name of the order that contain egg-laying mammals?
15. The following is a list of organisms belonging to various kingdoms and phyla.
a) Lobster
b) Housefly (Musca domestica)
c) Zea mays (maize)
d) Bread mold (Rhizopus)
e) Tilapia zillii
f) Frog (Rana spp.)
g) Zebra
h) Tilapia variabilis
i) Bat
j) Eagle
i. Classify these organisms into their kingdoms and phyla.
ii. Name the two organisms that are most closely related. Give a reason.
iii. What does the name mays represent?

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 16. How are some leeches adapted to a parasitic lifestyle?
17. Are there aquatic and flying mammals?
18. How do placental mammals reproduce?
19. Look at the following sets of organisms and for each set circle the organism that is the odd one out and
write the phylum to which the organism you circle belongs.

20. The following diagram shows some of the parasites of humans.

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 a. Define the term parasite.
b. From the parasites shown in the diagram name:
i. ONE flatworm
ii. ONE segmented worm (annelid)
iii. ONE insect
c. Explain why all viruses are considered as parasitic.

21. The following diagram shows organisms from different kingdoms.

a) The moss, the fern, the buttercup and grass all belong to the plant kingdom.
Name
i. ONE characteristic of the fern
ii. The phylum to which both the buttercup and the grass belong.
b) From the diagram list ONE organism belonging to the
i. Phylum Coelenterates
ii. Phylum Molluscs.
c) Name the other TWO kingdoms (besides the plant and animal kingdoms) that are represented by the
organisms shown in the diagram.
d) Explain the importance of the
i. Swimbladder in fish
ii. Streamlined shape in birds
iii. Pseudopodia in Ameoba
iv. Tentacles with stinging cells in Hydra.

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 e) Generally fish carry out external fertilization while birds have internal fertilization. Distinguish between
external and internal fertilization.
f) Explain why the wasp, the crab and the spider are all classified as arthropods.
g) List ONE structural difference between the spider and the wasp.

Chapter 7: CYTOLOGY

7.1. Overview of the chapter

 Cell membrane—the selectively permeable boundary of the cell.
• Phospholipids permit diffusion of lipid-soluble materials.
• Cholesterol provides stability.
• Proteins form channels, transporters, “self” antigens, and receptor sites for hormones or other signaling
molecules.
 Nucleus—the control center of the cell; has adouble-layer membrane.
• Nucleolus—forms ribosomal RNA.
• Chromosomes—made of DNA and protein;
DNA is the genetic code for the structure and functioning of the cell. A gene is a segment of DNA that is
the code for one protein. Human cells have 46 chromosomes, and their genetic information is called the
genome.
Cytoplasm—a watery solution of minerals, gases, and organic molecules; contains the cell organelles;
site for many chemical reactions.
 Cell organelles—intracellular structures with specific functions.

Organelle Function

Endoplasmic • Passageway for transport of materials within the cell

reticulum (ER) • Synthesis of lipids
Ribosomes • Site of protein synthesis
Golgi apparatus • Synthesis of carbohydrates
• Packaging of materials for secretion from the cell
Mitochondria • Site of aerobic cell respiration—ATP production
Lysosomes • Contain enzymes to digest ingested material or damaged tissue
Centrioles • Organize the spindle fibers during cell division
Cilia • Sweep materials across the cell surface
Flagellum • Enables a cell to move
Microvilli • Increase a cell’s surface area for absorption
Chloroplasts Site of photosynthesis

 Diffusion—movement of molecules from an area of greater concentration to an area of lesser

concentration; occurs because molecules have free energy: They are constantly in motion. Oxygen and
carbon dioxide are exchanged by diffusion in the lungs and tissues.
 Facilitated diffusion—transporters (carrier enzymes) that are part of the cell membrane permit cells to
take in materials that would not diffuse by themselves. Most cells take in glucose by facilitated diffusion.
 Active transport—a cell uses ATP to move substances from an area of lesser concentration to an area of
greater concentration. Nerve cells and muscle cells have sodium pumps to return Na +ions to the exterior
of the cells; this prevents spontaneous impulses. Cells of the small intestine absorb glucose and amino
acids from digested food by active transport.
 Phagocytosis—(a form of endocytosis) a moving cell engulfs something; white blood cells phagocytize
bacteria to destroy them.

7.2. Questions
1. What are the two big groups into which cells are classified?
2. What are the chemical substances that compose the plasma membrane?

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 3. What is the difference between plasma membrane and cell wall?
4. What are the main respective constituents of cell walls in bacteria, protists, fungi and plants?
5. Do membranes form only the outer wrapping of cells?
6. Of what substances is the nucleolus made? Is there a membrane around the nucleolus?
7. Where in the cell can ribosomes be found? What is the main biological function of ribosomes?
8. State the functions of the organic molecules of cell membranes: cholesterol, proteins, and phospholipids.
9. What is the relationship between concentration gradient and active and passive transport?
10. What are the three main types of passive transport?
11. What do facilitated diffusion and active transport have in common? What are the differences between
them?
12. How do the rough endoplasmic reticulum and the Golgi apparatus act in the production and releasing of
proteins?
13. What are some biological examples in which lysosomic enzymes play a fundamental role?
14. What are homologous chromosomes? Which are the human cells that do not have homologous
chromosomes?
15. How many chromosomes does a human normal haploid cell have? How many chromosomes does a
human normal diploid cell have? How many are the sex chromosomes within each of them?
16. Describe the function of each of these cell organelles: mitochondria, lysosomes, Golgi apparatus,
ribosomes, and endoplasmic reticulum.
17. Define osmosis, and describe one way this process is important within the body.
18. Draw a mitochondrion and show its main parts.
19. The figure below shows a chloroplast. What are the parts represented by the letter A, B, C, D, E and F?

20. Give the functions of the following:

a) Parenchyma cell
b) Companion cell
c) Root cap
d) Meristematic tissue
e) Ground tissue
21. Analyze the following figure and answer to the following question:

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 a) Is it an animal or plant cell? Explain.
b) What are the organelles represented by the letters from A to L?
c) State the functions of the organelles C, D and K.

22. The figure below represents a beaker containing two solutions separated by a semi permeable membrane.
Solution A has a water potential of – 200 MPa and solution B has a water potential of – 400 MPa. Which
of the two solutions has a higher water potential? In which direction will water molecules move?

23. The diagram below represents the plasma membrane of eukaryotic cells

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 i. Name the molecules A, B, C and D.
ii. State a reason for the orientation of molecules C.
iii. State the functions of A, B and D.
24. The figure below shows a section in an animal cell

a) What are the organelles represented by the letters A, B, C and D?

b) What is the functional relationship between the organelles B, C and D?
c) Which process is taking place at E?
d) In which organelle is DNA located in the cell?
25. The following are functions of cell structures or organelles. Identify the correct word that corresponds to
the definitions below.
a. The membrane bound organelle that contains DNA; found in eukaryotic cells.
b. The physical boundary between the inside of the cell (intracellular) and its outside environment
c. Structure that carries out specific functions inside the cell.
d. The organelles on which proteins are made (synthesized).
e. Contains the genetic information needed for building structures such as proteins.
f. The smallest unit that can carry out the processes of life; the basic unit of all living things.
g. The general term for all of the material inside the cell, between the cell membrane and the
nucleus.
26. State three differences between an active transport and a passive transport.
27. The rate of diffusion of a molecule across a membrane depends on the relative concentration of the
molecules on either side of the membrane, the membrane thickness and its surface area.

a) For a maximum diffusion to take place, which factor should:

I. Be as large as possible
II. Be as small as possible
b) Use the equation to explain how the following are adapted for efficient gas exchange.
I. Single celled amoeba.
II. The human lungs.
28.
a) What does membrane-bound organelles and non membrane-bound organelles mean?
b) State 2 examples of organelles surrounded by two membranes.
c) State 2 examples of organelles surrounded by a single membrane.
d) State 2 examples of organelles not surrounded by a membrane.
29. What does the fluid mosaic model describe?

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 30. What is the difference between cytoplasm and cytosol?
31. Identify two functions of plastids in plant cells.
32. If muscle cells become more active than they usually are, they will grow more mitochondria. Explain
why this happens.
33. How does osmosis differ from diffusion?
34. Are vesicles involved in passive transport? Explain.
35. Copy the table below and place a tick or cross in each box as appropriate.

Process Uses energy in the Uses proteins Specific Controllable by

form of ATP cell
Diffusion
Osmosis
Facilitated diffusion
Active transport
Endocytosis and
exoctosis

36. Copy and complete the table below to compare cell walls and cell membranes.
Feature Cell wall Cell membrane
Is the thickness normally measured in nm or µm?
Location
Chemical composition
Permeability
Function
Fluid or rigid

37. The electron micrograph shown below shows part of a secretory cell from the pancreas. The secretory
vesicles are Golgi vesicles and appear as dark round structures. The magnification is X8000.
a) Copy and complete the table. Use a ruler to help you find the actual sizes of the structures. Give your
answers in micrometers.
Structure Observed diameter (measured Actual size
with a ruler)
Maximum diameter of a Golgi vesicle
Maximum diameter of nucleus
Maximum length of the labeled
mitochondrion
b) The mitochondria in pancreatic cells are mostly sausage-shaped in three dimensions. Explain why
some of the mitochondria in the electron micrograph below appear roughly circular.

c) The figure below shows a diagram based on an electron micrograph of a secretory cell from the
pancreas. This type of cell is specialized for secreting (exporting) proteins. Some of the proteins are
digestive enzymes of the pancreatic juice. The cell is very active, requiring a lot of energy. The arrows
show the route taken by the protein molecules.

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 i. Describe what is happening at each of the stages A, B, C and D.
ii. Name one molecule or structure which leaves the nucleus by route E.
iii. Through which structure must the molecule or structure you named in ii pass to get through
the nuclear envelope?
iv. Name the molecule which leaves the mitochondrion in order to provide energy for this cell.

Chapter 8: The nucleic acids, protein synthesis and cell divisions

8.1. A review of the chapter

 DNA and the genetic code
• DNA is a double helix with complementary base pairing: A–T and G–C.
• The sequence of bases in the DNA is the genetic code for proteins.
• The triplet code: three bases (a codon) is the code for one amino acid.
• A gene consists of all the triplets that code for a single protein.
 RNA and protein synthesis
• Transcription—mRNA is formed as a complementary copy of the sequence of bases in a gene (DNA).
• mRNA moves from the nucleus to the ribosomes in the cytoplasm.
• tRNA molecules (in the cytoplasm) have anticodons for the triplets on the mRNA.
• Translation—tRNA molecules bring amino acids to their proper triplets on the mRNA.
• Ribosomes contain enzymes to form peptide bonds between the amino acids.
 Expression of the genetic code
• DNA → RNA → proteins (structural proteins and enzymes that catalyze reactions) → hereditary
characteristics.
• A genetic disease is a “mistake” in the DNA, which is copied by mRNA and results in a malfunctioning
protein.
 Mitosis—one cell with the diploid number of chromosomes divides once to form two cells, each with the
diploid number of chromosomes (46 for humans).
• DNA replication forms two sets of chromosomes during interphase.
• Stages of mitosis: prophase, metaphase, anaphase, and telophase.
Cytokinesis is the division of the cytoplasm following telophase.
• Mitosis is essential for growth and for repair and replacement of damaged cells.
• Most adult nerve and muscle cells seem unable to divide; their loss may involve permanent loss of
function.
 Meiosis—one cell with the diploid number of chromosomes divides twice to form four cells, each with
the haploid number of chromosomes (23 for humans).
• Oogenesis in the ovaries forms egg cells.
• Spermatogenesis in the testes forms sperm cells.
• Fertilization of an egg by a sperm restores the diploid number in the fertilized egg.

8.2. Questions
1. State the types of RNA and their functions.
2. How many chromosomes does a human cell have? What are these chromosomes made of?

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 3. Name the stage of mitosis in which each of the following takes place:
a. The two sets of chromosomes are pulled toward opposite poles of the cell
b. The chromosomes become visible as short rods
c. A nuclear membrane re-forms around each complete set of chromosomes
d. The pairs of chromatids line up along the equator of the cell
e. The centrioles organize the spindle fibers
f. Cytokinesis takes place after this stage

4. Explain what happens in each stage of mitosis

5. Describe two specific ways mitosis is important within the body. Explain why meiosis is important.
6. The figure below summarizes the events of the protein synthesis

a) What structures are represented by the letters A, B, C and D?

b) Name the process y.
c) Name the process x.
d) A tRNA molecule has two attachment sites; what is each for?

7. Compare mitosis and meiosis in terms of:

a. Number of divisions
b. Number of cells formed
c. Chromosome number of the cells formed

8. Explain the triplet code of DNA. Name the molecule that copies the triplet code of DNA. Name the
organelle that is the site of protein synthesis.
9. Analyze the following figure and answer to the questions:

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 a) What does the figure represent?
b) What are the elements represented by the letters A, B, C and D?

10. How many chromatids can you find in a human cell

a) In the G1 phase of interphase
b) In prophase of mitosis
c) In G2 phase of interphase
d) In telophase of mitosis
11. Explain the process of translation.
12. State a difference and a similarity between mitosis and meiosis II.
13. The photograph below shows cell division of a eukaryotic cell with 6 chromosomes. Try to identify the
phase of the cell cycle represented. (interphase, mitosis or meiosis and the phase)

14. State four differences between DNA and RNA.

15. One of the properties of DNA is its ability to replicate.
a) What does DNA replication mean?
b) In which phase of the cell cycle does this process occur?
c) Explain how DNA undergoes semi conservative replication.
d) State a difference between DNA replication and transcription.
e) The genetic code is said to be degenerate. What does this mean?

16. The following is an RNA sequence carried by transfer RNAs.

ACAGAGCCACUUCCAAAGACU
a. Is this a sequence of codons or anticodons?
b. What is the sequence on mRNA?
c. How many aminoacids will be added in the translation of this sequence?
d. Write the sequence of aminoacids by using the genetic code in mRNA from the table below

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 17. What are some examples of organs and tissues where mitosis is more frequent, less frequent or practically
absent?
18. Is cell division happening during the entire cell cycle? What is interphase?
19. What are the three periods into which interphase is divided?
20. During mitotic anaphase is there separation of homologous chromosomes or separation of identical
chromatids?

21. How does the quantity of genetic material vary within the cell during the sequential phases of the cell
cycle?
22. What is crossing over? In which period of meiosis does this event occur?

23. What are the respective functions of the separation of homologous chromosomes and of the separation of
identical chromatids in meiosis?
24. Answer the question below about the nucleic acids.
a) Define the term antiparallel.
b) A DNA strand has the base sequence ATTAGGCTAT. Write down the complementary strand
sequence.
c) A DNA molecule is 20 % Thymine (T). What percentage of each of the other types of base would it
contain?
d) What type of diseases can result from DNA copying wrong?
25. What are the three components of a nucleotide? Which component varies from one nucleotide to another?
26. What would be the minimum length (approximate number of bases) of a mRNA that coded for a protein
300 amino acids long?
27. What is mRNA splicing?
28. Define introns and exons.
29. Describe the role of the Genetic Code in translation.
30. What is a reading frame?
31. Discuss what is meant by the universal genetic code.
32.
Match the terms with their most suitable descriptions
(a) Messenger RNA (i) A length of a single DNA strand which codes for a
particular polypeptide chain.
(b) Ribosomal RNA (ii) A part of the molecule complementary to the specific
amino acid that the tRNA carries.
(c) Transfer RNA (iii) A molecule that carries base anticodon complementary to
codon on mRNA.
(d) Gene (iv) Structural component of ribosomes.
(e) Codon (v) Carries codons that code for the synthesis of polypeptide
chains.
(f) Anticodon (vi) A part of the mRNA molecule that has a sequence of base
coding for an amino acid.

33. The flowchart below shows the codons on mRNA and the amino acids that are coded.

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 a) State four features of the genetic code.
b) A section of a DNA strand is represented below:
TACGTACATTCGCCAGGA
i) How many hydrogen bonds are broken in the DNA molecule to expose this sequence of
bases?
ii) Write the sequence of mRNA codons for this section.
iii) What is the start codon in this mRNA strand?
iv) With reference to the table, use the standard abbreviations to write out the sequence of
amino acids coded by this section of the gene.
34. How could the uniform 2 nm diameter of DNA be affected if two purines or two pyrimidines could pair
with each other?
35. In the mitotic cell cycle of a human cell:
a) How many chromatids are present as the cell enters mitosis?
b) How many DNA molecules are present?
c) How many kinetochores are present?
d) How many chromatids are present in the nucleus of each daughter cell after mitosis and cell division?
e) How many chromatids are present in the nucleus of a cell after replication of DNA?
36. There are 20 different amino acids which cells use for making proteins.
a) How many different amino acids could be coded for by the triplet code? (Remember that there are 4
possible bases, and that the code is always read in just one direction on the DNA strand.)
b) Suggest how the ̔spare̕ triplets might be used.
c) Explain why the code could not be a two-letter code.
37. Copy and complete the following table to distinguish between the processes of transcription and
translation.
Transcription Translation

Site in cell where process occurs

Molecule used as a template in process

Molecule produced by the process

Component molecule (monomers) used in

process
One other molecule that is essential for the
process to occur

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 38. The drawing shows a polyribosome

a) Name X, Y and Z.
b) In which direction are the ribosomes moving? Explain how you were able to decide on their direction
of movement.

39. In the 1940s, Chargaff and his co-workers analyzed the base composition of the DNA of various
organisms. The relative numbers of the bases adenine (A), cytosine (C), guanine (G) and thymine (T) of
three of these organisms are shown in the table.
Relative numbers of bases

A C G T

Ox (spleen) 27.9 20.8 22.7 27.3

Ox (thymus) 28.2 21.2 21.5 27.8

Yeast 31.3 17.1 18.7 32.9

Virus with single-stranded DNA 24.3 18.2 24.5 32.3

Explain why:
a. The relative numbers of each base in ox spleen and thymus are the same, within experimental error.
b. The relative numbers of each base in yeast are different from those in ox spleen or thymus.
c. The relative numbers of each base A and T, or C and G, are similar in ox and yeast.
d. In the virus, the relative numbers of each base A and T, or C and G, are not similar.
40. Diagram 1 shows the chromosomes in the nucleus of a diploid cell.

a) Draw the nucleus of a gamete produced from this cell.

b) What type of nuclear division would be used in the production of the gamete?
c) Draw a diagram to show what the nucleus would look like in anaphase of mitosis.
Diagram 2 and 3 below show the same diploid nucleus as in diagram 1. However, the chromosomes
have been shaded.

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 d) State what the different types of shading represent in each nucleus.

Chapter 9: Plant histology

9.1. A review of the chapter

 Plants consist of three types of cells: parenchyma, collenchymas and sclerenchyma.

 Plants have four types of tissues: the dermal tissue, the ground tissue, the vacular tissue and the
meristematic tissue.
 The dermal tissue consists of the epidermis, or the outermost layer of cells; it functions in absorption and
protection in the roots and in gas exchange and protection in stems and leaves.
 The bulk of leaves, nonwoody stems, and nonwoody roots is ground tissue, which functions in storage,
metabolism and support.
 Vascular tissue consists of xylem, which carries water and mineral nutrients, and phloem, which
transports organic compounds and some mineral nutrients.
 An increase in length, called primary growth occurs mainly at the tips of stems and roots in the apical
meristems.
 In secondary growth, the stem and roots increase in diameter in the lateral meristems.
 Roots anchor the plant and store and absorb water and mineral nutrients from the soil.
 Young roots produce root hairs, which are extensions of epidermal cells that increase the surface area for
absorption.
 The root endodermis prevents substances from entering or leaving the root vascular tissue without passing
through a cell membrane.
 In dicots roots, the xylem forms a central star- shaped mass with phloem cells between the rays of the
star. Monocots roots have strands of xylem that alternate with strands of phloem. There is usually a central
core of parenchyma cells in the monocot that is called the pith.
 In most dicot stems, the vascular tissue consists of vascular bundles arranged in a ring. The xylem in each
vascular bundle is adjacent to the pith, and the phloem in each bundle is adjacent to the cortex. In most
monocot stems, the vascular bundles are scattered throughout the ground tissue, rather than forming a
ring.
 Secondary growth consists primarily of secondary xylem, called wood.
 In non-tropical areas, secondary xylem in stems forms one annual ring each year.
 Photosynthesis occurs mostly in the palisade mesophyll, which consists of rows of closely packed cells,
and the loosely packed spongy mesophyll.
 Gas exchange in leaves is controlled by stomata, or small openings in the leaf.
 Two guard cells surround each stoma. When the guard cells gain water, the stoma opens. When the guard
cells lose water, the stoma closes.

9.2. Questions
1. Which are the growth tissues of plants? How do they classify and where can they be found?
2. What are apical meristems? Which type of plant growth does this meristem promote?

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 3. What are the main features of the meristematic cells? Why do these cells need to have a high mitotic rate?
4. Which are the plant tissues responsible for the supporting of the plant?
5. Where in the leaves is the photosynthetic tissue often located?
6. Which are the specialized conductive tissues of the plants?
7. What are the cell types that form the xylem? What are the main features of those cells?
8. What are the cell types that form the phloem? What are the main features of those cells?
9. What is the vascular cambium? What is its function?
10. What are the plant tissues that constitute the functional structures of the leaf veins?
11. Which are the plant tissues specialized in covering?
12. What are the plant root hairs? Where can they be found and what is their functions?
13. Which are the plant tissues that form the plant roots?
14. What is the root cap?
15. What kinds of meristems do monocots and dicots have in common? What kinds do they not share?
16. The figure below shows a cross section through the organ X?

a) What is the organ represented by the figure above?

b) Which parts are labeled by A, B, C, D and E?
c) What are the functions of D and E?

17. Analyze the following figure

a) What does it represent?

b) What is represented by the letters A, B, C, D and E?
c) What are the features of D that help to perform its function?

18. State the types of meristems, their locations and their functions.
19. What is the difference between the internal structure of a dicot stem and that of a monocot stem?
20. Describe the basic function of each of the three leaf tissues and their structure.
21. The following is the internal structure of a leaf

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 a) State the names of the parts represented by the letters A, B, C, D, E and F.
b) In which part of the leaf most photosynthesis occurs?
c) Explain the process of opening and closing of stomata.

22. What causes a plant stem or root to grow in diameter?

23. Explain the difference between primary growth and secondary growth.
24. The figure below shows phloem tissue in a plant.

a) Identify the sieve tube cell, sieve plate and the companion cell.
b) What is the role of the sieve tube cell?
c) What is the role of the companion cell?
d) There are many theories to explain how materials are moved along the sieve tube cell. The most
likely is the mass flow or pressure flow hypothesis. Explain this theory.
25. Match the terms with their most suitable descriptions
a) Meristem i) Cells are impregnated with suberin to form a casparian strip.
b) Parenchyma ii) Translocation of organic solutes.
c) Collenchyma iii) Supporting tissue with thick lignified cell walls and tapering ends.
d) Sclerenchyma iv) Thickening of cellulose and pectin occur at corners of cell walls.
e) Xylem vessel v) Transportation of water; only found in angiosperms.
f) Tracheid vi) Transportation of water in ferns and conifers.

g) Sieve tube vii) Only present in phloem tissue of angiosperms; associated with
sieve tubes.

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 h) Companion cell viii) Major component of ground tissue.
i) Endodermis ix) Tissue which retain the ability to divide by mitosis.
j) Mesophyll x) Secretes a layer of waxy cuticle on its outer surfaces.
k) Aerenchyma xi) Contains chloroplasts to carry out photosynthesis.
l) Epidermis xii) Found in hydrophytes.

Chapter 10: Animal histology

10.1. A review of the chapter

A tissue is a group of cells with similar structure and function. The four main groups of tissues are epithelial,
connective, muscle, and nerve.

Epithelial Tissue—found on surfaces; have no capillaries; some are capable of secretion; classified as to
shape of cells and number of layers of cells

 Simple squamous—one layer of flat cells; thin and smooth. Sites: alveoli (to permit diffusion of gases);
capillaries (to permit exchanges between blood and tissues).
 Stratified squamous—many layers of mostly flat cells; mitosis takes place in lowest layer. Sites:
epidermis, where surface cells are dead (a barrier to pathogens); lining of mouth; esophagus; and vagina
(a barrier to pathogens).

Connective Tissue—all have a non-living intercellular matrix and specialized cells

 Blood—the matrix is plasma, mostly water; transports materials in the blood. Red blood cells carry
oxygen; white blood cells destroy pathogens and provide immunity; platelets prevent blood loss, as in
clotting. Blood cells are made in red bone marrow.
 Areolar (loose)—cells are fibroblasts, which produce protein fibers: collagen is strong, elastin is elastic;
the matrix is collagen, elastin, and tissue fluid. White blood cells and mast cells are also present. Sites:
below the dermis and below the epithelium of tracts that open to the environment (to destroy pathogens
that enter the body).
 Adipose—cells are adipocytes that store fat; little matrix. Sites: between the skin and muscles (to store
energy); around the eyes and kidneys (to cushion). Also involved in appetite, use of insulin, and
inflammation.
 Fibrous—mostly matrix, strong collagen fibers; cells are fibroblasts. Regular fibrous sites: tendons (to
connect muscle to bone); ligaments (to connect bone to bone); poor blood supply, slow healing
 Bone—cells are osteocytes; matrix is calcium salts and collagen, strong and not flexible; good blood
supply, rapid healing. Sites: bones of the skeleton (to support the body and protect internal organs from
mechanical injury).
 Cartilage—cells are chondrocytes; protein matrix is firm yet flexible; no capillaries in matrix, very slow
healing. Sites: joint surfaces of bones (to prevent friction); tip of nose and external ear (to support); wall
of trachea (to keep air passage open); discs between vertebrae (to absorb shock).

Muscle Tissue—specialized to contract and bring about movement

 Skeletal—also called striated or voluntary muscle. Cells are cylindrical, have several nuclei, and have
striations. Each cell has a motor nerve ending; nerve impulses are essential to cause contraction. Site:
skeletal muscles attached to bones (to move the skeleton and produce heat).
 Smooth—also called visceral or involuntary muscle. Cells have tapered ends, one nucleus each, and no
striations. Contraction is not under voluntary control. Sites: stomach and intestines (peristalsis); walls of
arteries and veins (to maintain blood pressure); iris (to constrict or dilate pupil).
 Cardiac—cells are branched, have one nucleus each, and faint striations. Site: walls of the four chambers
of the heart (to pump blood; nerve impulses regulate the rate of contraction).

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Nerve Tissue—neurons are specialized to generate and transmit impulses

 Cell body contains the nucleus; axon carries impulses away from the cell body; dendrites carry impulses
toward the cell body.
 A synapse is the space between two neurons; a neurotransmitter carries the impulse across a synapse.
 Specialized cells in nerve tissue are neuroglia in the CNS and Schwann cells in the PNS.
 Sites: brain; spinal cord; and peripheral nerves (to provide sensation, movement, regulation of body
functions, learning, and memory).

10.2. Questions
1. What are the main types of animal tissue?
2. What are epithelial tissues? What are their general functions and how is that function associated to the
features of the tissue?

3. Which cells is the nervous tissue constituted? How is the generic function of this tissue related to the
characteristics of the main cell type that forms it?
4. What are muscle tissues? How is the function of this tissue related to the typical characteristics of its
cells?
5. What are the general functions of the connective tissues?
6. What are the three types of protein fibers of the connective tissue?
7. What is the function of the collagen fibers of the connective tissue?
8. State the types of connective tissue, their structure, their locations and their functions.
9. Is the epithelium vascularized? How do nutrients and oxygen reach the epithelium? Why is this feature
an important evolutionary acquisition?
10. How are the epithelial tissues classified?
11. What is the function of keratin in the epidermis?
12. What are some functions of the cartilages in the human body?
13. What are the three main cell types that form the osseous tissue? What are their functions?
14. What are the types of muscle tissues? What are the morphological features that differentiate those types?
15. How is the striped pattern of the striated muscle cells formed?
16. What are the main proteins that constitute the sarcomere? What is the function of those molecules in the
muscle cells?
17. What are the positions of actin and myosin molecules in the sarcomere before and during the muscle
contraction?
18. The cells of all animals except sponges are organized into tissues.
a) What is a tissue?
b) Give the types of the following epithelial tissues.

A B C

19. Name two organs made primarily of nerve tissue, and state the general functions of nerve tissue.
20. The blood is a type of connective tissue consisting of a several kinds of cells suspended in a liquid matrix
called plasma.
a) What are the functions of red blood cells, white blood cells and platelets?
b) What are the adaptations of red blood cells to carry out their functions?
c) Explain the process of blood clotting.

21. The figure below shows the bone tissue

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 a) Label the parts A, B, C and D.
b) What is the functional unit of the bone?
c) What is the purpose of the blood vessels in bone tissue?
22. What are five functions of bones?
23. Give the names and functions of blood cells represented below:

24. Why is the heart muscle described as myogenic?

25. Compare and contrast the three types of muscles.
26. State the types of white blood cells and their functions.

Chapter 11: Microbiology and hygiene

12.1. A review of the chapter

Classification of Microorganisms and other livings that can cause or transmit a disease

 Bacteria—unicellular; some are pathogens.

 Viruses—not cells; all are parasites.
 Protozoa—unicellular protists; some are pathogens.
 Fungi—unicellular (yeasts) or multicellular (molds); most are decomposers.
 Worms—multicellular animals; a few are parasites.
 Arthropods—insects, ticks, or mites that are vectors of disease or cause infestations.

Infectious Disease

 Caused by microorganisms or their toxins.

 Clinical infections are characterized by symptoms; in a subclinical infection, the person shows no
symptoms.

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Methods of Control of Microbes

 Antiseptics—chemicals that destroy or inhibit bacteria on a living being.

 Disinfectants—chemicals that destroy or inhibit bacteria on inanimate objects.
 Sterilization—a process that destroys all living organisms.
 Public health measures include laws and regulations to ensure safe food and water.

Bacteria

 Shapes: coccus, bacillus, and spirillum.

 Flagella provide motility for some bacilli and spirilla.
 Aerobes require oxygen; anaerobes are inhibited by oxygen; facultative anaerobes grow in the presence
or absence of oxygen.
 The gram reaction (positive or negative) is based on the chemistry of the cell wall. The Gram stain is a
laboratory procedure used in the identification of bacteria.
 Capsules inhibit phagocytosis by white blood cells.
 Spores are dormant forms that are resistant to environmental extremes.
 Toxins are chemicals produced by bacteria that are poisonous to host cells.

Fungi

 Most are saprophytes, decomposers of dead organic matter. May be unicellular yeasts or multicellular
molds.
 Mycoses may be superficial, involving the skin or mucous membranes, or systemic, involving internal
organs such as the lungs or meninges.
Viruses

 Not cells; a virus consists of either DNA or RNA surrounded by a protein coat.
 Must be inside living cells to reproduce, which causes death of the host cell.
 Severity of disease depends on the types of cells infected; some viruses may cross the placenta and infect
a fetus.
 Antiviral medications must interfere with viral reproduction without harming host cells.

Protozoa

 Unicellular protists; some are pathogens.

 Some are spread by vectors, others by fecal contamination of food or water.
 Effective medications are available for most diseases.

Worms

 Simple multicellular animals; the parasites are flukes, tapeworms, and some roundworms.
 May have life cycles that involve other animal hosts as well as people.
 Effective medications are available for most worm infestations.

Body defenses

 The skin is a non specific defense that helps keep pathogens out of the body.
 A break in the skin will trigger another non specific defense called the inflammatory response,
characterized by swelling, redness, raised temperature, and pain.
 Neutrophils and macrophages are phagocytes that engulf and destroy pathogens and cellular debris.
Natural killer cells destroy infected cells.
 The immune system consists of the spleen, tonsils, adenoids, lymph nodes, thymus, bone marrow, and
white blood cells called lymphocytes.
 An antigen is any substance that can stimulate a response from the immune system. Lymphocytes have
receptor proteins on their cell membrane that allow them to recognize antigens.

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 12.2. Questions
1. State three beneficial effects of microorganisms and three disadvantages of microorganisms.
2. Define the following:
a) Antibody d) Immunity
b) Antigen e) Interferon
c) Vaccine
3. What role does increased permeability of capillaries play in inflammatory response?
4. The figure below represents HIV virus.

a) What is the function of reverse transcriptase?

b) Why are viruses considered as obligate intracellular parasites?
c) State a difference between HIV and a bacteriophage.

5. Distinguish active immunity and passive immunity.

6. What chemical defenses does the skin use against pathogens?
7. State the types of immunities represented in the examples below:
State whether they are natural or artificial and active or passive
a) a mom nursing a baby
b) a person being vaccinated
c) a sick person
d) someone receiving antibodies

8. Name these parts of bacterial cell:

a) Inhibits phagocytosis by white blood cells
b) Provides motility
c) The basis for the gram reaction or Gram stain
d) A form resistant to heat and drying
e) Chemicals produced that are poisonous to host cells
9. a) What is vaccination?
b) What is the difference between natural passive immunity and natural active immunity?
c) Explain why there is no vaccine for HIV?
d) State a disease caused by a bacterium, a disease caused by a virus, a disease caused by a protozoan
and their pathogens.
10. State and explain the three lines of defense of our body.
11. What is tuberculosis? How is the disease transmitted? Is there treatment for tuberculosis?
12. What is the etiological agent and the main manifestations of cholera?
13. What is the incubation period of an infection?
14. What are the human tissues affected by malaria? What are the main clinical manifestations of the disease?
15. How is HIV transmitted? What is the disease caused by this virus?
16. Which type of virus is the HIV? What is the enzyme reverse transcriptase present in HIV?
17. What are CD4 lymphocytes? What is the relationship between these cells and HIV? How does HIV
replicate?
18. What is the cause of the immunodeficiency presented by AIDS patients?
19. How do taenias obtain food and make gas exchange?
20. What are the segments that form the body of the tapeworm called? What is their function?
21. What is the life cycle of a tapeworm?

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 22. What is the life cycle of ascaris?
23. What is a prion?
24. What is cancer?
25. Describe the process of phagocytosis.
26. How does the inflammatory response help fight infections?
27. Describe the roles of leukocytes in the body’s second line of defense.
28. What are antigens and how do lymphocytes “recognize” them?
29. Explain how immunization prevents a disease such as measles.
30.
a) Name the causative agent of tuberculosis.
b) Explain how tuberculosis is transmitted.
c) State the regions of the world with the highest number of cases of tuberculosis.
d) Suggest reasons for the high number of tuberculosis in some parts of the world.

31. The table shows the number of cases of cholera and deaths from the disease for the five countries with
the greatest outbreaks as reported to the WHO in 2010.
Country Region Total number of Number of Case fatality
cases deaths rate %

Haiti Caribbean 179 379 3 990

Cameroon West Africa 10 759 657 6.10

Nigeria 44 455 1 712 3.85

Democratic Republic 13 884 182 1.31

of Congo
Papua New Guinea Australasia 8 997 95 1.06

Total All regions of the 317 534 7 543 2.38

world
a) Describe how cholera is transmitted.
b) With reference to the table:
i. Calculate the case fatality rate for Haiti in 2010.
ii. Suggest why the case of fatality rate varies between countries.
iii. Explain why it is important that the WHO collects data on outbreaks of cholera.
c) Explain why there no epidemics of cholera in highly economically developed countries such as
Australia, Malaysia and USA.
32. Explain the difference between artificial active immunization (vaccination) and artificial passive
immunization.
33. Explain the difference between natural immunity and artificial immunity.
34. Explain the meaning of the term autoimmune disease.

Chapter 12: Chemicals of life

12.1. A review of the chapter

Organic Compounds of Importance

Carbohydrates

 Monosaccharides are simple sugars. Glucose, a hexose sugar (C6H12O6), is the primary energy source for
cell respiration. Pentose sugars are part of the nucleic acids DNA and RNA.
 Disaccharides are made of two hexose sugars. Sucrose, lactose, and maltose are digested to
monosaccharides and used for cell respiration.

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  Polysaccharides are made of thousands of glucose molecules.
 Starches are plant products broken down in digestion to glucose. Glycogen is the form in which glucose
is stored in the liver and muscles. Cellulose, the fiber portion of plant cells, cannot be digested but
promotes efficient peristalsis in the colon.

Lipids

 True fats are made of fatty acids and glycerol; triglycerides are a storage form for potential energy in
adipose tissue.
 Phospholipids are diglycerides such as lecithin that are part of cell membranes. Myelin is a phospholipid
that provides electrical insulation for nerve cells.
 Steroids consist of four rings of carbon and hydrogen. Cholesterol, produced by the liver and consumed
in food, is the basic steroid from which the body manufactures others: steroid hormones, vitamin D, and
bile salts.

Proteins

 Amino acids are the subunits of proteins; 20 amino acids make up human proteins. Peptide bonds join
amino acids to one another.
 A protein consists of from 50 to thousands of amino acids in a specific sequence (primary structure) that
is folded into a specific shape (secondary and tertiary structures). Some proteins are made of two or more
amino acid chains; some proteins contain trace elements.
 Enzymes are catalysts, which speed up reactions without additional energy. The active site theory is based
on the shapes of the enzyme and the substrate molecules: These must “fit”.
 The enzyme remains unchanged after the product of the reaction is released. Each enzyme is specific for
one type of reaction. The functioning of enzymes may be disrupted by changes in pH or body temperature
or by the presence of a poison, which changes the shape of the active sites of enzymes.

Nucleic acids

 Nucleotides are the subunits of nucleic acids. A nucleotide consists of a pentose sugar, a phosphate group,
and a nitrogenous base.
 DNA is a double strand of nucleotides, coiled into a double helix, with complementary base pairing: A–
T and G–C. DNA makes up the chromosomes of cells and is the genetic code for the synthesis of proteins.
 RNA is a single strand of nucleotides, synthesized from DNA, with U in place of T. RNA functions in
protein synthesis.
 ATP is a nucleotide that is specialized to trap and release energy. Energy released from food in cell
respiration is used to synthesize ATP from ADP + P. When cells need energy, ATP is broken down to
ADP + P and the energy is released for cell processes.

Water

Water—makes up 60% to 75% of the body.

 Solvent—for transport of nutrients in the blood and excretion of wastes in urine.
 Lubricant—mucus in the digestive tract.
 Changes temperature slowly, and prevents sudden changes in body temperature; absorbs body heat in
evaporation of sweat.
 Water compartments—the locations of water within the body: Intracellular—within cells; 65% of total
body water. Extracellular—35% of total body water (Plasma—in blood vessels, Lymph—in lymphatic
vessels, Tissue fluid—in tissue spaces between cells).

12.2. Exercices
1. What are the main biological functions of water?
2. What are the main biological processes in which calcium participates?
3. Why is iodine important for human beings?

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 4. What are pentoses? What are the roles of pentoses in DNA and RNA molecules?
5. What are the main biological functions of the polysaccharides?
6. What are the main types of lipids?
7. How are triglycerides made?
8. What are phospholipids?
9. What are steroids? What are some examples of steroids with a biological function?
10. What is meant by saturation or unsaturation of oils and fats?
11. What is the constitutional unit of proteins?
12. What is the primary structure of a protein? What is the importance of the primary structure?

13. What is the secondary structure of a protein?

14. What is the tertiary structure of a protein? What are the main types of tertiary structure?
15. What is the quaternary structure of a protein? Do all proteins have quaternary structure?
16. What is protein denaturation? Is there any change in the primary structure when a protein is denatured?
17. What are some factors that can lead to protein denaturation?
18. What is meant by substrates of enzymatic reactions?
19. What are the main theoretical models that try to explain the formation of the enzyme-substrate complex?
20. How does the substrate concentration affect the speed of enzymatic reactions?
21. What are enzyme cofactors?
22. Name the organic molecule with each of the following functions:
a) The genetic code in chromosomes
b) “Self” antigens in our cell membranes
c) The storage form for glucose in the liver
d) The storage form for excess food in adipose tissue
e) The precursor molecule for the steroid hormones
f) The undigested part of food that promotes peristalsis
g) The sugars that are part of the nucleic acids
23.
a) What is meant by the term lock and key in the activity of enzymes?
b) How is this theory different to the induced fit hypothesis?
c) Describe what is meant by the activation energy?
d) What are coenzymes? State also one example of a coenzyme.
e) What is the effect of increasing the substrate concentration on non competitive inhibitors?
24. The following question is about enzymes
a. Which kinds of inhibitors are represented on the figure below?

b. State 2 factors that can affect the rate of enzymes.

c. What is the optimum temperature of the following enzymatic reaction with the following graph?

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 25. What are the differences between fibrous and globular proteins?
26. Name the subunit (smaller molecules) of which each of the following is made: DNA, glycogen, a true fat,
and a protein.
27. Answer the following questions on proteins.
a) Complete the chemical formula between the two aminocids:

b) What is the name of the bond formed between the two aminoacids?
28. The figure below shows the structure of a triglyceride

A triglyceride
a) What are the constituents of this macromolecule?
b) What type of bond links the unit together?
c) What is the difference between this molecule and a phospholipid?
d) State 2 functions of lipids in living organisms?
29. The results of food tests on an unknown sample are shown below. Copy and complete the table to show
the conclusions which could be drawn from these results.

Food test Result Conclusion

Sample mixed with iodine in potassium Blue black colour

iodide
Sample boiled with Benedict’s solution Blue colour

Sample treated with dilute acid, Red precipitate

neutralized and then tested with
Benedict’s solution
Sample tested using Biuret’s solution Blue ring at surface and on
shaking lilac-purple solution

30. Distinguish between:

a) Alpha (α)glucose and (β) beta glucose
b) Glycogen and cellulose

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 c) Amylopectin and amylose
31. Match the terms on the list on the left with the properties in the list on the right.

1) Competitive inhibitor a) Modifies R groups at the active site

2) Noncompetitive inhibitor b) Prevents the conversion of the inactive form of the

enzyme to the active form

3) Irreversible inhibitor c) Resembles the substrate in shape

4) Allosteric inhibitor d) Functions at a location on the enzyme molecule

distant from the active site

32. State the property of water that allows each of the following to take place and, in each case, explain its
importance.
a) The cooling of skin during sweating
b) The transport of glucose and ions in a mammal
c) Much smaller temperature fluctuations in lakes and oceans than in terrestrial (land-based) habitats.
33. The diagram below shows a dissacharide called lactose. The carbon atoms are numbered. You are not
expected to have seen this structure before. Lactose is a reducing sugar found in milk. It is made from a
reaction between glucose and galactose.

a) Suggest two functions that lactose could have.

b) What is the name given to the reaction referred to above that results in the formation of lactose?
c) Identify the bond X in the diagram.
d) Draw diagrams to show the structures of separate molecules of glucose and galactose.
e) Using information in the diagram, is the alpha or beta form of glucose used to make lactose? Explain
your answer.
f) Like lactose, sucrose is a disaccharide. If you were given a solution of lactose and a solution of
sucrose, state briefly how you could distinguish between them.

34. The diagram below shows the structures of three amino acids

a) Draw a diagram to show the structure of the tripeptide with the following sequence: Alanine-glycine-
serine
b) What is the name given to the sequence of amino acids in a protein?
c) What substance, apart from the tripeptide, would be formed when the three amino acids combine?

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 d) Draw a ring around an atom or group of atoms making up an R group that could hydrogen bond with
a neighbouring R group.
e) Draw a ring around and label the peptide bond (s) you have drawn in the diagram.
35. Copy and complete the table below, which summarizes some of the functional categories into which
proteins can be placed.
Category Example

Structural

Enzyme

Insulin

Hemoglobin and myoglobin

Defensive

Actin and myosin

Storage

36. The diagram below shows an enzyme and two inhibitors of the enzyme, X and Y. Which of the following
describes the two inhibitors?

X and Y are competitive inhibitors.

X and Y are non-competitive inhibitors.
X is a competitive inhibitor and Y is a non-competitive inhibitor.
X is a non-competitive inhibitor and Y is a competitive inhibitor.
37. List five ways in which the molecular structure of glycogen and amylopectin are similar.
38. Make a table to show three ways in which the molecular structure of amylose and cellulose differ.

Chapter 13: Autotrophic nutrition

13.1. A review of the chapter

 Autotrophs make their own carbohydrate foods, transforming sunlight in photosynthesis or transferring
chemical energy from inorganic molecules in chemosynthesis.
 Heterotrophs consume organic molecules originally made by autotrophs.
 All life depends absolutely upon autotrophs to make food molecules.
 The process of photosynthesis produces more than 99% of all food for life, forming the foundation of
most food chains.
 Only three groups of organisms – plants, algae, and some bacteria – carry out the process of
photosynthesis.
 All organisms use similar energy-carrying molecules for food and to carry out life processes.
 Glucose (C6H12O6,) is a nearly universal fuel delivered to cells, and the primary product of
photosynthesis.

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  ATP molecules store smaller amounts of energy and are used within cells to do work.
 Chlorophyll and NADPH molecules hold energy temporarily during the process of photosynthesis.
 Chloroplasts are the organelles within plant and algal cells that organize enzymes and pigments so that
the chemical reactions proceed efficiently.

 Photosynthesis consists of two groups of chemical reactions: the Light Reactions and the Calvin Cycle.
 Light Reactions transform energy from sunlight into chemical energy, and produce and release oxygen
gas.
 When light strikes pigment molecules, electrons absorb its energy and are excited.
 Light also provides energy to split water molecules into electrons, hydrogen ions, and oxygen gas.
 The oxygen gas is released as “waste”, but it is the source of the oxygen in Earth’s atmosphere.
 Two pathways capture the energy from excited electrons as chemical energy stored in the bonds of
molecules; both pathways involve electron transport chains.
 One produces NADPH molecules, which store energy and “hot hydrogen”.
 A second pumps hydrogen ions into the thylakoids, forming an electrochemical gradient whose energy
builds ATP molecules. This is “chemiosmosis”.
 The Calvin Cycle uses the NADPH and ATP from the Light Reactions to “fix” carbon and produce
glucose.
 Carbon dioxide enters the Calvin Cycle when an enzyme nicknamed “Rubisco” attaches it to a 5-carbon
sugar. The unstable 6-carbon compound immediately breaks into two 3-carbon compounds, which
continue the cycle.
 Most plants fix CO2 directly with this pathway, so they are called C-3 plants.
 Some plants have evolved preliminary fixation pathways, which help them conserve water in hot, dry
habitats, but eventually the carbon enters the cycle along the “Rubisco” pathway.
 C-4 plants such as corn use a 3-carbon carrier to compartmentalize initial carbon fixation in order to
concentrate CO2 before sending it on to Rubisco.
 CAM plants such as jade plants and some cacti open their stomata for preliminary CO 2 fixation only at
night.
 In the Calvin Cycle, the fixed CO2 moves through a series of chemical reactions, gaining a small amount
of energy (or “hot hydrogens”) from ATP or NADPH at each step.
 Six turns of the cycle process 6 molecules of carbon dioxide and 12 “hot hydrogens” to produce a single
molecule of glucose.
 The cycle begins and ends with the same 5-carbon molecule, but the process stores chemical energy in
food for nearly all life.
 The figure below shows a review of photosynthesis

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  The compensation point is when the rate of photosynthesis equals the rate of respiration and there is no
net gain or loss of gases.

13.2. Questions

1. How is light from the sun transformed into chemical energy to be used by the living beings on earth?
2. Which are the living beings that carry out photosynthesis? Which is the cell organelle responsible for the
absorption of light for the photosynthesis process in plants and algae?
3. What is ADP phosphorylation? What respectively are photophosphorylation and oxidative
phosphorylation?
4. What are the chemical substances produced by water photolysis? What is the destination of each of those
substances?
5. Discuss the importance of photosynthesis to humans in terms of food, fuel, and atmosphere. In what ways
could you affect the process of photosynthesis to conserve these benefits?
6. Name and describe the two types of food making found among autotrophs, and give an example of each.
Which is quantitatively more important to life on earth?
7. Explain how the structure of a chloroplast – its membranes and thylakoids – makes its function – the
chemical reactions of photosynthesis – more efficient.
8. a) What is transpiration?
b) What are the types of transpiration? Explain also.
c) State 2 advantages of transpiration and 1 disadvantage of transpiration.
d) State 3 xeromorphic adaptations of plants and explain how these adaptations act.

9. Name the two stages (sets of reactions) which make up the process of photosynthesis.

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 10. Answer the question below on the Calvin cycle and photosynthesis in general.
a) What is the enzyme required for the fixation of carbon dioxide?
b) What is the stable product produced after the fixation of carbon dioxide?
c) What is the carbohydrate produced directly from the Calvin cycle?
d) How many times the cycle turn for the net synthesis of that carbohydrate?
e) How many ATP and NADPH are consumed for the net synthesis of that carbohydrate?
11. The figure below shows a section of a xerophytic leaf. Describe three features which indicate that this
plant lives in a dry climate. For each feature, explain how it helps the plant to survive in this environment.

12. The figure below is a simple potometer used to investigate the rate of transpiration under different
conditions

What do you think would happen to the rate of transpiration under?

a) High temperature
b) High humidity
c) High wind
d) High light intensity

13. Students investigated the effect of removing leaves from a plant shoot on the rate of water uptake. Each
student set up a potometer with a shoot that had eight leaves. All the shoots came from the same plant.
The potometer they used is shown in the diagram.

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 a) Describe how students would have returned the air bubble to the start of the capillary tube in this
investigation.
b) Give two precautions the students should have taken when setting up the potometer to obtain reliable
measurements of water uptake by the plant shoot.
c) Calculate the volume of the water lost by transpiration given that the capillary tube has a diameter of
3.6 cm and the air bubble has moved a distance of 8cm.
14. The figure below summarizes the movement of materials into and out of a chloroplast. Identify the
substances moved, indicated by labels A, B, C, D, E and F.

15. Match the major events with the stage of photosynthesis in which they occur.
Stages
Light Reactions
Calvin Cycle
Major Events
A. Carbon dioxide is fixed.
B. Electrons in chlorophyll jump to higher energy levels.
C. Glucose is produced.
D. NADPH and ATP are produced.
E. NADPH and ATP are used.
F. Oxygen gas is released.
G. Water is split.
16. Use your understanding of pigments to explain why the living world appears green. Then think a little
further and offer a hypothesis to explain why the world is not black!
17. Explain the value of cycles of chemical reactions, such as the Calvin Cycle.
18. Explain how their various methods of carbon fixation adapt C-3, C-4, and CAM plants to different
habitats.

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 19. The figure below shows the sequence of events that take place in the light dependent reactions

a) Identify the points labeled A and B.

b) What process is taking place at C?
c) What are the products of the light dependent reactions? (They are indicated by ‘? ’ on the diagram).
20. We humans depend on photosynthesis, and our actions in turn affect photosynthesis.
Explain how humans depend on photosynthesis for:
a) food
b) building materials for furniture and homes
c) fuel for vehicles, heat, and electricity
d) breathable air
Explain how the following actions would affect photosynthesis:
i. We may clear-cut a forest for timber and parking lot space
ii. When we burn fossil fuels for transportation or heat, we release CO 2 into the atmosphere
iii. When we dam up and overuse water in a certain area, the area water table drops

21. State the types of movement represented below:

a) Euglena moving in the direction of light.
b) Roots growing towards air.
c) Pollen tube growing towards the ovary.
d) Pitcher plants catching insects.
e) The folding of Mimosa pudica when touched.
22. State the main plant hormones, where they are produced and their functions.
23. Explain the process of non cyclic photophosphorylation.
24. State three differences between cyclic and non cyclic photophosphorylation.
25. What are the major differences between C3 and C4 plants?
26. An experiment was set up as shown below to investigate a certain process.

The set-up was left in bright sunlight for several hours.

a) State the aim of the experiment.
b) Name X and Y.

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 c) Other than sunlight, name three factors that would affect the experiment.
d) State how the identity of X could be confirmed.
e) Write a chemical equation for this process.

27. In an experiment, a leaf from a plant which had been kept in the dark overnight was boiled in water for a
minute, boiled in alcohol and washed in water. Iodine solution was then added onto the leaf.
a) Why was the leaf boiled in:
i. Water?
ii. Ethanol?
b) What observation was made after adding iodine to the leaf?
c) Give a reason for this observation?
d) State the aim of the experiment.
28. State the pathways that water takes while moving from cel to cell in plants.
29. Demonstrate your understanding of the Calvin cycle by answering the following questions:
a) Which compound is the initial carbon dioxide acceptor?
b) How many times must the cycle operate to form one molecule of glucose from CO 2?
c) The reaction in which 3PGA is reduced to a 3-carbon sugar phosphate (PGAL) is driven by energy
from what compounds?
d) What is the source of the compound(s) in question 29 (c)?
e) C4 plants have an enzyme which has a higher affinity for CO2 than the analogous enzyme in C3
plants. Name the enzymes and the compounds produced as a result of the action of the enzymes.
30. Trace the path of an electron through the reactions of photophosphorylation by rearranging the following
steps into their correct sequence. You may find it necessary to use certain steps more than once.
a) Chlorophyll electron moved to higher orbital by absorption of light.
b) ATP generated in highly exergonic redox reactions.
c) Electron passed through series of redox reactions.
d) Electron transferred to NADP+.
e) Electron removed from H2O molecule.
31. Match each stage in photosynthesis with its correct description
(a) Photolysis of water (i) ATP and NADPH are produced.
(b) Non-cyclic (ii) Only Photosystem I is involved.
photophosphorylation
(c) Cyclic photophosphorylation (iii) Mechanism to generate ATP.
(d) Carbon dioxide fixation (iv) Protons, electrons and oxygen formed.
(e) chemiosmosis (v) RuBP required, PGAL formed.
32. The diagram below shows five coleoptiles (small shoots) receiving unidirectional light.

a) Name the type of response shown by shoot A.

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 b) Use your biological knowledge to explain why shoot C grows upwards but shoot D bends
towards light.
c) A biology student remarked that shoot B whose tip was cut and removed will start growing after
two weeks. Discuss whether you agree with the student’s remark. Give a reason for your answer.
33. Arrange the following in order of water potential. Use the symbol ˃ to mean ̔greater than̕ . Dry atmospheric
air; mesophyll cell; root hair cell; soil solution; xylem vessel contents.
34. The graph below shows the relationship between the rate of transpiration and the rate of water uptake for
a particular plant.

a) Define the term transpiration.

b) State two environmental factors which are most likely to be responsible for the changes in
transpiration rate shown in the graph above.
c) Describe the relationship between the rate of transpiration and the rate of water uptake shown in the
graph above.
d) Explain the relationship.
35. Translocation of organic solutes takes place between sources and sinks.
a) Briefly explain under what circumstances:
i. A seed could be a sink
ii. A seed could be a source
iii. A leaf could be a sink
iv. A leaf could be a source
v. A storage organ could be a sink
vi. A storage organ could be a source
b) Suggest two possible roles for glucose in each of the following sinks:
i. A storage organ
ii. A growing bud.
36.
a) Explain what is meant by a limiting factor.
b) List four factors that may be rate-limiting in photosynthesis.
c) At low light intensities, increasing the temperature has little effect on the rate of photosynthesis. At
high light intensities, increasing the temperature increases the rate of photosynthesis. Explain these
observations.
37. State the main differences between tropic and nastic movements.
38. List any three differences between the light dependent reactions and the light independent reactions of
photosynthesis.

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Chapter 14: Physiology of the nervous system

14.1. A review of the chapter

Functions of the Nervous System

 Detect changes and feel sensations.

 Initiate responses to changes.
 Organize and store information.

Nervous System Divisions

 Central nervous system (CNS): brain and spinal cord.

 Peripheral nervous system (PNS): 12 pairs of cranial nerves and 31 pairs of spinal nerves.

Nerve Tissue—neurons (nerve fibers) and specialized cells (Schwann, neuroglia)

 Neuron cell body contains the nucleus; cell bodies are in the CNS or in the trunk and are protected by
bone.
 Axon carries impulses away from the cell body; dendrites carry impulses toward the cell body.
 Schwann cells in PNS: Layers of cell membrane form the myelin sheath to electrically insulate neurons;
nodes of Ranvier are spaces between adjacent Schwann cells. Nuclei and cytoplasm of Schwann cells
form the neurolemma, which is essential for regeneration of damaged axons or dendrites.
 Oligodendrocytes in CNS form the myelin sheaths; microglia phagocytize pathogens and damaged cells;
astrocytes contribute to the blood–brain barrier.
 Synapse: the space between the axon of one neuron and the dendrites or cell body of the next neuron. A
neurotransmitter carries the impulse across a synapse and is then destroyed by a chemical inactivator.
Synapses make impulse transmission one way in the living person.

Types of Neurons—nerve fibers

 Sensory: carry impulses from receptors to the CNS; may be somatic (from skin, skeletal muscles, and
joints) or visceral (from internal organs).
 Motor: carry impulses from the CNS to effectors; may be somatic (to skeletal muscle) or visceral (to
smooth muscle, cardiac muscle, or glands). Visceral motor neurons make up the autonomic nervous
system.
 Interneurons: entirely within the CNS.

The Nerve Impulse

 Polarization—neuron membrane has a (+) charge outside and a (+) charge inside.
 Depolarization—entry of Na ions and reversal of charges on either side of the membrane.
 Impulse transmission is rapid, often several meters per second.
 Saltatory conduction—in a myelinated neuron only the nodes of Ranvier depolarize; increases speed of
impulses.

The Spinal Cord

 Functions: transmits impulses to and from the brain, and integrates the spinal cord reflexes.
 Location: within the vertebral canal; extends from the foramen magnum to the disc between the 1 st and
2nd lumbar vertebrae.
 Cross-section: internal H-shaped gray matter contains cell bodies of motor neurons and interneurons;
external white matter is the myelinated axons and dendrites of interneurons.
 Ascending tracts carry sensory impulses to the brain; descending tracts carry motor impulses away from
the brain.

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  Central canal contains cerebrospinal fluid and is continuous with the ventricles of the brain.

Spinal Cord Reflexes—do not depend directly on the brain

 A reflex is an involuntary response to a stimulus.

 Reflex arc—the pathway of nerve impulses during a reflex: (1) receptors, (2) sensory neurons, (3) CNS
with one or more synapses, (4) motor neurons, (5) effector that responds.

Meninges and Cerebrospinal Fluid (CSF)

 Three meningeal layers made of connective tissue: outer—dura mater; middle—arachnoid membrane;
inner—pia mater; all three enclose the brain and spinal cord.
 Subarachnoid space contains CSF, the tissue fluid of the CNS.

The Autonomic Nervous System (ANS)

 Has two divisions: sympathetic and parasympathetic; their functioning is integrated by the hypothalamus.
 Sympathetic division—dominates during stress situations; responses prepare the body to meet physical
demands.
 Parasympathetic division—dominates in relaxed situations to permit normal functioning.

14.2. Questions
1. Which are the structures that are part of the nervous system?
2. Which are the main cells of the nervous system?
3. What are the functional differences between neurons and glial cells?
4. What are the three main parts into which a neuron can be divided? What are their respective functions?
5. What are synapses?
6. According to the function of the transmitted neural impulse which are the types of neurons? How different
are the concepts of afference and efference of the neural impulse transmission?
7. What are nerves?
8. What are ganglia?
9. What is meant by the peripheral nervous system (PNS)?
10. What is the function of the myelin sheath? Do all axons present a myelin sheath?
11. What are the cells that produce the myelin sheath? Of which substance is the myelin sheath formed?
12. What are meninges and cerebrospinal fluid?
13. What is the difference between brain and cerebrum? What are the main parts of these structures?
14. How is the cerebrum anatomically divided?
15. Draw a neuron and show its main parts.
16. What are the two main ions that participate in the electrical impulse transmission in neurons?
17. Which is the normal sign of the electric charge between the two sides of the neuron plasma membrane?
What is the potential difference (voltage) generated between these two sides? What is that voltage called?
18. What is the excitation threshold of a neuron? How does this threshold relate to the “all-or-nothing” rule
of the neural transmission?
19. How different are the concepts of action potential, resting potential and excitation threshold concerning
neurons?
20. What are some important neurotransmitters?
21. Since neurotransmitters are not consumed in the synaptic process, what are the mechanisms to reduce
their concentrations in the synaptic cleft after they have been used?
22. What is the neuromuscular synapse?
23. The figure below shows the event that takes place in a chemical synapse:

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 a) What are the elements represented by the letters A to E?
b) What is the role of Ca2+ in the process?
c) What is the difference between an electrical synapse and a chemical synapse?

24. Define reflex, and name the five parts of a reflex arc.
25. Identify the four lobes of the brain represented on the figure below by the letters A, B, C and D.

26. State 3 differences between the nervous and hormonal communication

27. State the number of pairs of spinal and cranial nerves nerves.
28. The figure below shows a cross section through a spinal cord of a mammal.

a) Identify the structures labeled A, B, C, D, E and F.

b) Copy the figure and draw and label three neurons (simple lines only) to show a reflex arc. Indicate
by means of arrows the direction in which the impulse will travel along the three neurons.

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 29. The figure below shows the structure of a human brain. Identify the structures A, B, C and D and the
function of each.

30. The figure below shows the change in membrane potential during the passage of a nerve impulse.

a) What is the resting potential of this neuron?

b) How is the resting potential maintained in the neuron?
c) Explain how ion movements bring about the change in membrane potential between points A and B
on the graph?
d) How is the resting potential restored?
e) What is the refractory period?
f) How does the length of the refractory period limit the number of impulses which can pass along the
axon?
g) Account for the blip at point X on the graph?
31. Use this image of an action potential to answer the following questions.

a) What is the membrane potential at the peak (after 2 milliseconds)? Is it positive or negative?
b) What happens to the membrane potential after 5 ms?
c) At the peak point when the membrane potential is 40mV, does the cell have an overall negative charge or
positive charge?
d) Hyperpolarization, which means the cell becomes more negatively charged than it is at resting potential
(more negative than -70 mV), can happen as a result of the binding of an inhibitory neurotransmitter to
its receptor. Propose what happens to sodium and potassium ions during hyperpolarization.
e) How does voltage relate to the membrane potential?

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 f) What would happen to a cell if its sodium and potassium pumps failed to work at the end of an action
potential?
g) The backflow of a nerve impulse is prevented by the fact that at a chemical synapse, the axon terminal
does not have neurotransmitter receptors and dendrites cannot secrete neurotransmitter chemicals. What
does this statement tell you about the direction of nerve impulses in neurons?

32. The figure below shows the changes in potential difference across the membrane of a neuron over a period
of time. The membrane was stimulated at time A and time B with stimuli of different intensities.

a) Stimulus b resulted in an action potential. Describe what is occurring at C, D and E.

b) Suggest why stimulus A did not result in an action potential being produced whereas stimulus b did.

Chapter 15: sense organs

15.1. Overview of the chapter

Purpose of Sensations—to detect changes in the external or internal environment to enable the body to
respond appropriately to maintain homeostasis

 Receptors: detect a change (usually very specific) and generate impulses.

 Sensory neurons: transmit impulses from receptors to the CNS.
 Sensory area: most is in the cerebral cortex; feels and interprets the sensation.
 Motor neurons: transmit impulses from the CNS to the effectors.

The Eye

 Eyelids and eyelashes keep dust out of eyes; conjunctivae line the eyelids and cover white of eye.
 Lacrimal glands produce tears, which flow across the eyeball to two lacrimal ducts, to lacrimal sac to
nasolacrimal duct to nasal cavity. Tears wash the anterior eyeball and contain lysozyme to inhibit bacterial
growth.
 Sclera: outermost layer of the eyeball, made of fibrous connective tissue; anterior portion is the
transparent cornea, the first light-refracting structure.
 Choroid layer: middle layer of eyeball; dark blue pigment absorbs light to prevent glare within the
eyeball.
 Ciliary body (muscle) and suspensory ligaments— change shape of lens, which is made of a transparent,
elastic protein and which refracts light.
 Iris: two sets of smooth muscle fibers regulate diameter of pupil, that is, how much light strikes the retina.
 Retina: innermost layer of eyeball; contains rods and cones. Rods—detect light; abundant toward
periphery of retina. Cones—detect color; abundant in center of retina.
 Fovea: in the center of the macula lutea; contains only cones; area of best color vision.

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  Optic disc: no rods or cones; optic nerve passes through eyeball.
 Posterior cavity contains vitreous humor (semisolid) that keeps the retina in place.
 Anterior cavity contains aqueous humor that nourishes the lens and cornea; made by capillaries of the
ciliary body, flows through pupil, is reabsorbed to blood at the canal of Schlemm.

The Ear

 Outer ear—auricle or pinna has no real function for people; ear canal curves forward and down into
temporal bone.
 Middle ear—eardrum at end of ear canal vibrates when sound waves strike it. Auditory bones: malleus,
incus, stapes; transmit vibrations to inner ear at oval window.
 Eustachian tube—extends from middle ear to nasopharynx; allows air in and out of middle ear to permit
eardrum to vibrate; air pressure in middle ear should equal atmospheric pressure.
 Inner ear—bony labyrinth in temporal bone, lined with membranous labyrinth. Perilymph is fluid
between bone and membrane; endolymph is fluid within membrane. Membranous structures are the
cochlea, utricle and saccule, and semicircular canals.
 Cochlea—snail-shell shaped; three internal canals; cochlear duct contains receptors for hearing: hair cells
in the organ of Corti; these cells contain endings of the cochlear branch of the 8th cranial nerve.
 Physiologies of hearing— sound waves stimulate vibration of eardrum, malleus, incus, stapes, oval
window of inner ear, perilymph and endolymph of cochlea, and hair cells of organ of Corti. When hair
cells bend, impulses are generated and carried by the 8th cranial nerve to the auditory areas in the temporal
lobes. Round window prevents pressure damage to the hair cells.
 Utricle and saccule—membranous sacs in the vestibule; each contains hair cells that are affected by
gravity. When position of the head changes, otoliths bend the hair cells, which generate impulses along
the vestibular branch of the 8th cranial nerve to the cerebellum, midbrain, and cerebrum. Impulses are
interpreted as position of the head at rest.

Sense of Taste

 Chemoreceptors are in taste buds on the tongue; detect chemicals (foods) in solution (saliva) in the mouth.
 Five basic tastes: sweet, sour, salty, bitter, and savory; foods stimulate combinations of receptors.
 Pathway: facial and glossopharyngeal nerves to taste areas in parietal-temporal lobes.

Sense of Smell

 Chemoreceptors are in upper nasal cavities; several hundred different ones; detect vaporized chemicals
(many combinations possible).
 Pathway: olfactory nerves to olfactory bulbs to olfactory areas in the temporal lobes.
 Smell contributes greatly to what we call taste.

Cutaneous Senses—provide information about the external environment and the skin itself

 The dermis has free nerve endings that are receptors for pain, heat, and cold, and encapsulated nerve
endings that are receptors for touch and pressure

15.2. Questions

1. What are the main structures of the human eye?

2. What is the function of the iris and of the pupil?
3. Which is the part of the human visual system where the receptors that sense light, i.e., the photoreceptor
cells, are located? How do those cells work?
4. Since the visual images are projected in an inverted manner on the retina why don't we see things upside
down?
5. What is visual accommodation?
6. How can the visual deficiencies known as myopia and hypermetropia be optically explained?
7. What is the tympanum? In which part of the ear is it located and what is its function?

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 8. What are the elements that form the middle ear? What are the names of the three middle ear ossicles that
participate in the phonosensitivity?
9. Distinguish between rods and cones.
10. Why are taste and smell called the “two chemical senses”?
11. Outline how the ear is important to the sense of body balance.
12. What role does skin have in detecting external stimuli?

13. State the two general functions of receptors.

14. The figure below shows the human eye. Name the parts represented by the letters A to G.

15. Name the part of the eye with each of the following functions:
a) Changes the shape of the lens
b) Contains the rods and cones
c) Forms the white of the eye
d) Forms the optic nerve
e) Keep dust out of eye
f) Changes the size of the pupil
g) Produce tears
h) Absorbs light within the eyeball to prevent glare
i) Makes the aqueous humor
16. With respect to vision:
a) Name the structures and substances that refract light rays (in order)
b) State what cones detect and what rods detect. What happens within these receptors when light
strikes them?
c) Name the cranial nerve for vision and the lobe of the cerebrum that contains the visual area
17. With respect to the ear:
a) Name the parts of the ear that transmit the vibrations of sound waves (in order)
b) State the location of the receptors for hearing
c) State the location of the receptors that respond to gravity
d) State the location of the receptors that respond to motion
e) State the two functions of the 8th cranial nerve
f) Name the lobe of the cerebrum concerned with hearing
g) Name the two parts of the brain concerned with maintaining balance and equilibrium

18. The figure below shows the structure of the ear. Label the parts represented by the letters A, B, C, D, E
and F.

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 19. The figure below shows a section through the skin.
a) State two functions of the skin
b) Identify the parts labeled by the letters from A to I.

Chapter 16: Endocrinology

16.1. A review of the chapter

Endocrine glands are ductless glands that secrete hormones into the blood. Hormones exert their effects on
target organs or tissues.

Regulation of Hormone Secretion

 Hormones are secreted when there is a need for their effects. Each hormone has a specific stimulus for
secretion.
 The secretion of most hormones is regulated by negative feedback mechanisms: As the hormone exerts
its effects, the stimulus for secretion is reversed, and secretion of the hormone decreases.

Pituitary Gland (Hypophysis)—hangs from hypothalamus by the infundibulum

 Posterior Pituitary (Neurohypophysis)—stores hormones produced by the hypothalamus

 ADH—increases water reabsorption by the kidneys, decreases sweating, in large amounts causes
vasoconstriction. Result: decreases urinary output and increases blood volume; increases BP. Stimulus:
nerve impulses from hypothalamus when body water decreases.

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  Oxytocin—stimulates contraction of myometrium of uterus during labor and release of milk from
mammary glands. Stimulus: nerve impulses from hypothalamus as cervix is stretched or as infant sucks
on nipple.
 Anterior Pituitary (Adenohypophysis)—secretions are regulated by releasing hormones from the
hypothalamus.
 GH— GH increases amino acid transport into cells and increases protein synthesis; increases rate of
mitosis; increases use of fats for energy. Stimulus: GHRH from the hypothalamus.
 TSH—increases secretion of thyroxine and T3 by the thyroid. Stimulus: TRH from the hypothalamus.
 ACTH—increases secretion of cortisol by the adrenal cortex. Stimulus: CRH from the hypothalamus.
 Prolactin—initiates and maintains milk production by the mammary glands. Stimulus: PRH from the
hypothalamus.
 FSH—In women: initiates development of ova in ovarian follicles and secretion of estrogen by follicle
cells.
 In men: initiates sperm development in the testes. Stimulus: GnRH from the hypothalamus.
 LH—In women: stimulates ovulation, transforms mature follicle into corpus luteum and stimulates
secretion of progesterone.
 In men: stimulates secretion of testosterone by the testes. Stimulus: GnRH from the hypothalamus.

Thyroid Gland—on front and sides of trachea below the larynx

 Thyroxine (T4) and T3. Increase use of all food types for energy and increase protein synthesis. Necessary
for normal physical, mental, and sexual development. Stimulus: TSH from the anterior pituitary.
 Calcitonin—produced by parafollicular cells. Decreases reabsorption of calcium from bones and lowers
blood calcium level. Stimulus: hypercalcemia.

Parathyroid Glands—four; two on posterior of each lobe of thyroid

 PTH—increases reabsorption of calcium and phosphate from bones to the blood; increases absorption of
calcium and phosphate by the small intestine; increases reabsorption of calcium and excretion of
phosphate by the kidneys, and activates vitamin D. Result: raises blood calcium and lowers blood
phosphate levels. Stimulus: hypocalcemia. Inhibitor: hypercalcemia.

Pancreas—extends from curve of duodenum to the spleen. Islets of Langerhans contain alpha cells and beta
cells

 Glucagon—secreted by alpha cells. Stimulates liver to change glycogen to glucose; increases use of fats
and amino acids for energy. Result: raises blood glucose level. Stimulus: hypoglycemia.
 Insulin—secreted by beta cells. Increases use of glucose by cells to produce energy; stimulates liver and
muscles to change glucose to glycogen; increases cellular intake of fatty acids and amino acids to use for
synthesis of lipids and proteins. Result: lowers blood glucose level. Stimulus: hyperglycemia.

Adrenal Glands—one on top of each kidney; each has an inner adrenal medulla and an outer adrenal cortex

Ovaries—in pelvic cavity on either side of uterus

Testes—in scrotum between the upperthighs

Other Hormones

• Melatonin—secreted by the pineal gland during darkness; brings on sleep.

• Prostaglandins—synthesized by cells from the phospholipids of their cell membranes; exert their effects locally.
Are involved in inflammation and pain, reproduction, nutrient metabolism, changes in blood vessels, blood
clotting.

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Mechanisms of Hormone Action

 A hormone affects cells that have receptors for it. Receptors are proteins that may be part of the cell
membrane, or within the cytoplasm or nucleus of the target cell.
 The two-messenger mechanism: a protein hormone (1st messenger) bonds to a membrane receptor;
stimulates formation of cyclic AMP (2nd messenger), which activates the cell’s enzymes to bring about
the cell’s characteristic response to the hormone.
 Steroid hormones diffuse easily through cell membranes and bond to cytoplasmic receptors. Steroid-
protein complex enters the nucleus and activates certain genes, which initiate protein synthesis.

16.2. Questions
1. What is the constitution of the endocrine system?
2. Why the endocrine system is considered one of the integrative systems of the body? What is the other
physiological system that also has this function?
3. What are hormones?
4. What are target organs of the hormones?

5. How does the circulatory system participate in the functioning of the endocrine system?
6. Are hormones only proteins?
7. What are the main divisions of the hypophysis? What are their functions?
8. What is the relation between the hypothalamus and the hypophysis?
9. What are some diseases caused by abnormal GH secretion by the hypophysis?
10. What are the target tissues and target organs of each adenohypophyseal hormone?
11. What are the three main signs of diabetes?

12. What is the difference between diabetes mellitus and diabetes insipidus? What are the characteristic signs
of diabetes insipidus?

13. Why does the urinary volume increase when alcoholic beverages are ingested?
14. What is the difference between type I diabetes mellitus and type II diabetes mellitus?
15. State three differences between endocrine and exocrine glands.
16. Give the names of the endocrine glands represented by the letters A to J.

17. State the main properties of hormones.

18. Use the following to describe a negative feedback mechanism: TSH, TRH, decreased metabolic rate,
thyroxine and T3.
19. Answer the question below on endocrinology

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 a) Define the term below
i. Tropic hormone
ii. Exocrine gland

b) Complete the table below:

Hormone Endocrine gland Target cell / organ

ADH

Prolactin

Epinephrine

Calcitonin

c) What will be the effects if the following hormones are produced in high amount: GH and epinephrine?

20. Describe the antagonistic effects of PTH and calcitonin on bones and on blood calcium level. State the
other functions of PTH.
21. Describe the antagonistic effects of insulin and glucagon on the liver and on blood glucose level.
22. State what prostaglandins are made from? State three functions of prostaglandins.
23. State the effect of aldosterone on the kidneys. Describe the results of this effect on the composition of the
blood.
24. Name the hormone involved in the functions described below and the name of the gland which produces
it:
a) Controls reabsorption of Na+ in the kidney.
b) Increases the permeability of convoluted distal tubule and collecting duct.
c) Increases heart rate.
d) Increases blood glucose level.
e) Decreases blood glucose level.
f) Repair and growth of the endometrium.
g) Stimulates the anterior pituitary gland to release FSH.
h) Stimulates contraction of the uterus.
i) Stimulates the mammary glands to secrete milk.

Chapter 17: Homeostasis, excretion and thermoregulation

17.1. Overview of the chapter

Functions of the Lymphatic System

 To return tissue fluid to the blood to maintain blood volume.

 To protect the body against pathogens and other foreign material.

Parts of the Lymphatic System

 Lymph and lymph vessels.

 Lymphatic tissue: lymph nodes and nodules, spleen, and thymus; lymphocytes mature and proliferate.

Lymph—the tissue fluid that enters lymph capillaries

 Similar to plasma, but more WBCs are present, and has less protein.
 Must be returned to the blood to maintain blood volume and blood pressure.

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The urinary system consists of two kidneys, two ureters, the urinary bladder, and the urethra.

 The kidneys form urine to excrete waste products and to regulate the volume, electrolytes, and pH of blood
and tissue fluid.
 The other organs of the system are concerned with elimination of urine.

The Nephron—the functional unit of the kidney; 1 million per kidney

 Renal corpuscle—consists of a glomerulus surrounded by a Bowman’s capsule.

Glomerulus—a capillary network between an afferent arteriole and an efferent arteriole.
Bowman’s capsule—the expanded end of a renal tubule that encloses the glomerulus; inner layer is made
of podocytes, has pores, and is very permeable; contains renal filtrate (potential urine).
 Renal tubule—consists of the proximal convoluted tubule, loop of Henle, distal convoluted tubule, and
collecting tubule. Collecting tubules unite to form papillary ducts that empty urine into the calyces of the
renal pelvis.
 Peritubular capillaries—arise from the efferent arteriole and surround all parts of the renal tubule.

Formation of Urine

 Glomerular filtration—takes place from the glomerulus to Bowman’s capsule. High blood pressure in the
glomerulus forces plasma, dissolved materials, and small proteins out of the blood and into Bowman’s
capsule. The fluid is now called filtrate. Filtration is selective only in terms of size; blood cells and large
proteins remain in the blood.
 Tubular reabsorption—takes place from the filtrate in the renal tubule to the blood in the peritubular
capillaries; 99% of the filtrate is reabsorbed; only 1% becomes urine.
o Active transport—reabsorption of glucose, amino acids, vitamins, and positive ions; threshold level is
a limit to the quantity that can be reabsorbed.
o Passive transport—most negative ions follow thereabsorption of positive ions.
o Osmosis—water follows the reabsorption of minerals, especially sodium.
o Pinocytosis—small proteins are engulfed by proximal tubule cells.
 Tubular secretion—takes place from the blood in the peritubular capillaries to the filtrate in the renal tubule;
creatinine and other waste products may be secreted into the filtrate to be excreted in urine; secretion of H+
ions helps maintain pH of blood.
 Hormones that affect reabsorption—aldosterone, antidiuretic hormone, and parathyroid hormone.

Body Temperature

 Normal range is 96.5° to 99.5°F (36° to 38°C), with an average of 98.6°F (37°C).
 Normal fluctuation in 24 hours is 1° to 2°F.
 Temperature regulation in infants and the elderly is not as precise as it is at other ages.

Heat Loss

 Most heat is lost through the skin.

 Blood flow through the dermis determines the amount of heat that is lost by radiation, conduction, and
convection.
 Vasodilation in the dermis increases blood flow and heat loss; radiation and conduction are effective only if
the environment is cooler than the body.
 Vasoconstriction in the dermis decreases blood flow and conserves heat in the core of the body.
 Sweating is a very effective heat loss mechanism; excess body heat evaporates sweat on the skin surface;
sweating is most effective when the atmospheric humidity is low.
 Sweating also has a disadvantage in that water is lost and must be replaced to prevent serious dehydration.
 Heat is lost from the respiratory tract by the evaporation of water from the warm respiratory mucosa; water
vapor is part of exhaled air.

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  A very small amount of heat is lost as urine and feces are excreted at body temperature.

Regulation of Heat Loss

 The hypothalamus is the thermostat of the body and regulates body temperature by balancing heat production
and heat loss.
 The hypothalamus receives information from its own neurons (blood temperature) and from the temperature
receptors in the dermis.
 Mechanisms to increase heat loss are vasodilation in the dermis and increased sweating. Decreased muscle
tone will decrease heat production.
 Mechanisms to conserve heat are vasoconstriction in the dermis and decreased sweating. Increased muscle
tone (shivering) will increase heat production.

17.2. Questions

1. How do antagonistic mechanisms manage homeostatic regulation?

2. What is an example of negative feeback of the homeostatic regulation?

3. What is an example of positive feedback of the homeostatic regulation?
4. What is excretion?
5. What are the three main types of nitrogen wastes excreted by living beings?
6. What is the main nitrogen waste of humans?
7. How is urea formed in the human body?
8. What is the functional unity of the kidneys?
9. Draw a nephron and show its main parts.
10. What are the three main renal processes that combined produce urine?
11. What is the main transformation presented by the glomerular filtrate in comparison to the blood?
12. What is proteinuria? Why is proteinuria a sign of glomerular renal injury?

13. Where does most of the water resorbed after glomerular filtration go? What are the other substances resorbed
by the nephron tubules?
14. Why do cells of the nephron tubules present a great amount of mitochondria?
15. What is tubular secretion? What are some examples of substances secreted through the renal tubules?

16. Which are the three hormones that participate in the regulation of the renal function?

17. What is the function of the antidiuretic hormone? Where is it made and which are the stimuli that increase or
reduce its secretion?
18. How does aldosterone act and where is it produced?

19. What is hemodialysis?

20. Excretion is one process that is used to maintain homeostasis.
a) What is excretion?
b) What are the nitrogenous wastes of a fish and an insect?

c) What is the significance of the difference in diameter between the afferent and efferent arteriole?
d) The diagram below represents a part of the nephron. Use it to answer the question below:

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 i. Name the parts labeled A, B and C.
ii. Name the fluids found in A and C.
iii. Name the process by which the fluid found in A is formed.
iv. Give tho differences in the composition of the fluids in A and B.
21.
a) Define the following terms:
i. Homeostasis
ii. Interstitial fluid
b) State 2 differences between blood and tissue fluid.
c) State 2 functions of the lymphatic system.
d) State 2 organs of the lymphatic system.
e) Explain how the liver makes the regulation of amino acids.
22. Explain the importance of tubular secretion
23. State the mechanism of tubular reabsorption of each of the following:
a) Water
b) Glucose
c) Small proteins
d) Positive ions
e) Negative ions
f) Amino acids
g) Vitamins
24. Describe the pathway of blood flow through the kidney from the abdominal aorta to the inferior vena cava.
25. Name the hormone that has each of these effects on the kidneys:
a) Promotes reabsorption of Na+ ions
b) Promotes direct reabsorption of water
c) Promotes reabsorption of Ca2+ ions
d) Promotes excretion of K+ ions
26.
a) Why do many desert animals have a long loop of Henle?
b) Desert animals often rely on metabolic water. Explain this term.
c) How can desert animals modify their behavior to conserve water?
27. The table below shows the quantity of substances which are filtered, reabsorbed or secreted in the kidney.

Substance Quantity filtered Quantity Quantity % of filtered

into nephron each reabsorbed per excreted per day which is
day day reabsorbed
Water 180 litres 178.5 1.5
Glucose 800 mEq 799.5 0.5
Urea 56 g 28 28
Sodium ions 25,200 mEq 25,050 150
Chloride ions 18,000 mEq 17,850 150
Potassium ions 720 mEq 620 100
a) Complete the last column by calculating the percentage of the filtered quantity which is reabsorbed.

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 b) Why is nearly all of the glucose reabsorbed?
c) What disease is characterized by quantities of glucose in urine?
d) Urea is a nitrogenous waste product. Why is half of it reabsorbed?

28. In what circumstances will the kidneys excrete H + ions? What ions will be returned to the blood? How will
this affect the pH of blood?
29. In what circumstances do the kidneys secrete renin, and what is its purpose?
30. In what circumstances do the kidneys secrete erythropoietin, and what is its purpose?
31. Name the part of the brain that regulates body temperature, and explain what is meant by a thermostat.
32. Describe the responses by the body of an endotherm to a warm environment and to a cold environment.
33.
a) Define the following
i. Ectothermy
ii. Hibernation
iii. Estivation
iv. Endothermy
b) State and explain the adaptations of animals to living in cold climates.

34. The figure shows the detailed structure of a cell of the proximal/first convoluted tubule and the adjacent
capillary.

a) How is the structure of these cells adapted to absorb materials from the tubule?
b) Describe the way in which glucose and water are moved from the filtrate into the capillary?

35. All hormones work on a similar principle. The flowchart below shows the sequence of events leading to the
production of thyroxine.

a) How does the level of thyroxine affect the action of the hypothalamus and the pituitary gland?
b) What is the name of this control mechanism?

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 c) Thyroxine affects both the hypothalamus and the pituitary gland. Is there any advantage in affecting
both, rather than one or the other?
d) How does the thyroid stimulating hormone reach the thyroid gland?
36. How does ADH control the amount of water in urine? How is this an example of negative feedback?
37. Summarize the processes and structures involved in excretion by the kidneys.
38. Contrast the effects on the kidneys of diabetes insipidus and diabetes mellitus.
39. List three parts of the lymphatic system and their functions.
40. The table below shows the percentage of various components in the blood plasma in the part labeled A, the
fluid in the part labeled B and in the urine of a human.
Components of blood % in plasma in A % in fluid in B % in urine in bladder

Protein 7 0 0

Glucose 0.2 0.02 0.05

Urea 0.03 0.03 2.0

Sodium ions 0.32 0.32 0.35

Chloride ions 0.37 0.37 0.6

Water 92 98 96

i.Give a reason why there is no protein in urine.

ii.Which component of urine shows the greatest percentage increase in concentration compared
to the fluid in B?
iii. Give a reason why the component you have named in (ii) above has the greatest increase in
concentration in urine.
iv. Suggest with a reason the health condition of the person from whom the figures were obtained.
41. The diagram shows the formation of urea from an amino acid

a) Name the compound X which is removed from the amino acid.

b) Name the chemical process which results in formation of X.
c) Name the cycle of chemical reactions Y which results in the formation of urea.
d) Name the organ which is responsible for the formation of urea.
e) Name the organ which is responsible for the excretion of urea.
f) Name the nitrogenous excretory compound produced by insects.
g) Explain why this is a safer excretory compound for terrestrial animals than the ammonia produced by
many marine invertebrates.

42. The following diagram shows the nephron.

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 a) From the diagram above write the number that represents the:
i. Collecting duct
ii. Bowman’s Capsule
b) On the diagram above label the loop of Henle.
c) Name structure X.
d) Compare the blood pressure in the afferent and efferent arterioles and explain the cause of this difference.
e) Proteins are not present in the glomerular filtrate but amino acids are. Explain.
f) Compare the urea concentration in the renal artery with that in the renal vein.
g) Name TWO organs that excrete urea.

43. The control of blood glucose concentration involves a negative feedback mechanism.
a) What are the stimuli, receptors and effectors in this control mechanism?
b) Explain how negative feedback is involved in this homeostatic mechanism.

44. The control of the water content of the blood is an example of homeostasis.
a) Name the part of the body that monitors the water potential of the blood.
In an investigation of the factors that influence urine production, a person drank one liter of water. The
person’s urine was collected at half-hourly intervals for four hours after drinking. The results are shown
as line A on the figure. On the following day, the same person drank one liter of a dilute salt solution
and the urine was collected in the same way (line B). Dilute salt solution has about the same water
potential as blood plasma.

b) Calculate how much urine was produced in the two hours after drinking the liter of water.
c) Explain why the person produced so much urine after drinking the liter of water.
d) Suggest why the results during the second day were so different from those on the first day.

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 e) Explain why negative feedback, and not positive feedback, is involved in homeostatic mechanisms.

45. An investigation was carried out to determine the response of pancreatic cells to an increase in the glucose
concentration of the blood. A person who had been told not to eat or drink anything other than water for 12
hours then took a drink of a glucose solution. Blood samples were taken from the person at one hour intervals
for five hours, and the concentration of glucose, insulin and glucagon in the blood were determined. The
results are shown in the graph below:

a) Explain why the person was told not to eat or drink anything other than water for 12 hours before having
the glucose drink.
b) Use the information in the figure to describe the response of the pancreatic cells to an increase in the
glucose concentration.
c) Outline the role of insulin when the glucose concentration in the blood increases.
d) Suggest how the results will change if the investigation continued longer than five hours without the
person taking any food.
e) Outline the sequence of events that follows the binding of glucagon to its membrane receptor on a liver
cell.

Chapter 18: Respiration and gas exchange

18.1. Overview of the chapter

The respiratory system moves air into and out of the lungs, which are the site of exchange for O 2 and CO2
between the air and the blood. The functioning of the respiratory system depends directly on the proper
functioning of the circulatory system.

 The upper respiratory tract consists of those parts outside the chest cavity.
 The lower respiratory tract consists of those parts within the chest cavity.

Alveoli—the sites of gas exchange in the lungs

 Made of alveolar type I cells, simple squamous epithelium; thin to permit diffusion of gases.
 Surrounded by pulmonary capillaries, which are also made of simple squamous epithelium
 Elastic connective tissue between alveoli is important for normal exhalation.
 A thin layer of tissue fluid lines each alveolus; essential to permit diffusion of gases.

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  Alveolar type II cells produce pulmonary surfactant that mixes with the tissue fluid lining to decrease surface
tension to permit inflation of the alveoli.
 Surfactant decreases the surface tension in the fluid lining the alveoli. Reduced surface tension prevents
smaller alveoli from collapsing and also makes it easier to inflate lungs. The surfactants decrease the work
of breathing.

Pulmonary Volumes

 Tidal volume—the amount of air in one normal inhalation and exhalation.

 Minute respiratory volume—the amount of air inhaled and exhaled in 1 minute.
 Inspiratory reserve volume—the amount of air beyond tidal in a maximal inhalation.
 Expiratory reserve volume—the amount of air beyond tidal in the most forceful exhalation.
 Vital capacity—the sum of tidal volume, inspiratory and expiratory reserves.
 Residual volume—the amount of air that remains in the lungs after the most forceful exhalation; provides for
continuous exchange of gases.
 Alveolar ventilation—air that reaches the alveoli for gas exchange; depends on normal thoracic and lung
compliance.
 Anatomic dead space—air still in the respiratory passages at the end of inhalation (is normal).

Transport of Gases in the Blood

 Oxygen is carried by the iron of hemoglobin (Hb) in the RBCs. The O2–Hb bond is formed in the lungs where
the PO2 is high.
 In tissues, Hb releases much of its O2; the important factors are low PO2 in tissues, high PCO2 in tissues, and
a high temperature in tissues.
 Oxygen saturation of hemoglobin is 95% to 97% in systemic arteries and averages 70% to 75% in systemic
veins.
 Most CO2 is carried as HCO3- ions in blood plasma. CO2 enters the RBCs and reacts with H2O to form
carbonic acid (H2CO3). Carbonic anhydrase is the enzyme that catalyzes this reaction.
 H2CO3 dissociates to H+ ions and HCO3– ions.
 The HCO3– ions leave the RBCs and enter the plasma; Hb buffers the H+ ions that remain in the RBCs. Cl–
ions from the plasma enter the RBCs to maintain ionic equilibrium (the chloride shift).
 When blood reaches the lungs, CO2 is re-formed, diffuses into the alveoli, and is exhaled.

Cell Respiration—the breakdown of food molecules to release their potential energy and synthesize ATP

 Glucose + oxygen yields CO2+ H2O + 38ATP + heat.

 The breakdown of glucose involves three stages: glycolysis, the Krebs cycle, and the cytochrome (electron)
transport system.
 The oxygen necessary comes from breathing.
 The water formed becomes part of intracellular fluid; CO2 is exhaled; ATP is used for energy requiring
reactions; heat provides a body temperature.
 The process of cellular respiration can be summarized as below:

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Proteins and Fats—as energy sources

 Excess amino acids are deaminated in the liver and converted to pyruvic acid or acetyl groups to enter the
Krebs cycle. Amino acids may also be converted to glucose to supply the brain
 Glycerol is converted to pyruvic acid to enter the Krebs cycle.
 Fatty acids, in the process of beta-oxidation in the liver, are split into acetyl groups to enter the Krebs cycle;
ketones are formed for transport to other cells.

18.2. Questions

1. What is the difference between cellular respiration and gas exchange?

2. Describe four common features of respiratory surfaces found in animals.
3.
a) Describe the mechanism by which a fish moves water through its gills.
b) Mammals extract about 25 % of the available oxygen from the air in the lungs. Many fish extract up to
80 % of the dissolved oxygen in the air. Explain how the countercurrent flow in the gills increases the
uptake of oxygen into the blood.

4. The table below shows the percentage composition of inspired, alveolar and expired air.
Gas Inspired air % Alveolar air % Expired air %

Nitrogen 79.0 80.7 79.6

Oxygen 21.0 13.2 16.4

Carbon dioxide 0.004 5.5 4.0

Water Variable saturated saturated

Explain why:

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 a) The percentage of nitrogen gas in expired air is virtually the same as in inspired air.
b) The percentage of oxygen is lower in alveolar air than in expired air,
c) Expired air is saturated with water vapour.

5. What are the different types of gas exchange that occur in animals?
6. Oxygen comes from the environment and carbon dioxide in the end returns to the environment. How do small
animals solve the problem of taking away and bringing these molecules from/to their cells? Why isn't that
solution possible for larger animals?
7. Which animals make tracheal respiration? Is there a blood-like fluid that participates in this process?
8. What is the difference between respiration by diffusion and cutaneous respiration? Does blood participate in
cutaneous respiration?
9. Which animals make cutaneous respiration?
10. What are branchiae (gills)? What are examples of animals that “breath” through branchiae?
11. What are respiratory pigments? What are some respiratory pigments and in which animal groups can each of
them be found?

12. What is the anatomical reason for the left bronchus to be more elevated than the right bronchus? Why in most
cases of aspiration of foreign material by children is the object found in the right bronchus?
13. How are inhalation and expiration carried out?
14. What is the physical process through which gas exchange is accomplished in the pulmonary alveoli?
15. What is the chemical equation of the formation of bicarbonate from carbon dioxide and water? What is the
enzyme that catalyzes this reaction?
16. How do cells obtain energy for their functioning?
17. Under which conditions do aerobic cells carry out fermentation?

18. In general what are the reagents and products of fermentation?

19. How can the knowledge about fermentation explain the origin of muscle cramps and pains after intense
physical exertion?
20. How many ATP molecules are produced for each glucose molecule used in fermentation? How many ATP
molecules are produced for each glucose molecule used in aerobic respiration?

21. What are the three phases into which the cell respiration is divided?
22. What is glycolysis? What are the products of this process?
23. Does glycolysis occur within the mitochondria?
24. What happens during aerobic respiration to the pyruvic acid molecules made by glycolysis? What is the
sequence of reactions that then follows?
25. How many carbon dioxide molecules are liberated after each cycle of the Krebs cycle? For a single glucose
how many carbon dioxide molecules were already liberated by the aerobic respiration at that point?
26. Where in mitochondria does the process called respiratory chain occur? Which are the products of the Krebs
cycle used in that final phase of the aerobic respiration?
27. Until the Krebs cycle, aerobic respiration can be described without mentioning oxygen, the chemical element
after which the reaction gets its name. Where in the process does this chemical element take part? What is its
importance?
28. What are the major differences between cellular respiration and photosynthesis?
29. Compare aerobic repiration with anaerobic respiration or photosynthesis.
30. The following flowchart summarises the reactions that take place in glycolysis
Glucose → 2 × glyceraldehydes 3-phoshate → 2 × pyruvate
a) How many carbon atoms are there in glucose, glyceraldehydes 3-phoshate and pyruvate?
b) What is the net gain of ATP in glycolysis?
c) Why is ATP needed for glycolysis?
d) Hydrogen carriers are also involved in glycolysis. Name the hydrogen carrier and describe its role.
e) Where does glycolysis occur in the cell?
f) What would happen to the pyruvate when:
i) There is plentiful supply of oxygen?
ii) There is no oxygen?
31. The figure below shows the oxygen dissociation curve for adult hemoglobin.

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 a) Explain why the curve has a S shape.
b) Copy the graph and draw another curve to show:
i. The oxygen dissociation curve under conditions of higher carbon dioxide concentration,
ii. The oxygen dissociation curve of fetal hemoglobin.
c) Explain your reasons for the shape and position of your curves.

32. The figure below shows pulmonary volumes

Which volumes make up the vital capacity? Which volume cannot be measured with a spirometer?
33. Describe the function of the electron transport chain. Where is it located in the mitochondrion?
34. What does the term oxidative phosphorylation mean?
35. A student set up an experiment using germinating seeds and boiled seeds as shown in the diagram below:

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 a) State the objective of this experiment and the observation made after 24 hours?
b) Account for the observation made in (a) above?
c) Suggest why vacuum flasks were used in the experiment?
d) What was the purpose of the set-up B?

36. The figure below shows an experiment set up to investigate the exchange of gases in living organisms.

After every ten minutes each test tube was gently shaken.
a) State the changes expected in three boiling tubes.
b) Account for these changes.
37. Complete the table below:
Input(s) Output(s) Location in
cell/organelle
Glycolysis
Fermentation
Citric acid cycle
Respiratory chain

38. Match the terms in the left-hand column with the appropriate statement from the right-hand column.

1) Mitochondrial matrix a) End product may be lactic acid or ethanol

2) Glycolysis b) Location of most citric cycle enzymes

3) Citric acid cycle c) Pigments of the electron transport system

4) Cristae d) Accompanied via the chemiosmotic mechanism

5) Oxidative phosphorylation e) Net energy yield is 2 ATP

6) AcetylcoA f) Combines with oxaloacetate to form citrate

7) Pyruvate g) Two molecules are produced for each molecule of

glucose

8) Cytochromes h) Points for attachment for respiratory pigments

9) Fermentation i) AcetylcoA oxidized to carbon dioxide

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 39. Match the terms with their most suitable descriptions

(a) Erythropoietin (i) Release of oxygen from oxyhaemoglobin

(b) Myoglobin (ii) An increased partial pressure of carbon dioxide and
decreased PH cause hemoglobin to have a lower affinity for
oxygen.
(c) Hemoglobin (iii) A term used instead of concentration when comparing the
proportions of gases in a mixture.
(d) Surfactant (iv) The amount of air moved in and out with each normal
breath.
(e) Dissociation (v) A continuous flow of air into and out of the lungs.
(f) Bohr effect (vi) Controls production of red blood cells in the red bone
marrow.
(g) Partial pressure (vii) Respiratory pigment in red blood cells.
(h) ventilatiom (viii) Acts as a store of oxygen in resting skeletal muscles.
(i) Tidal volume (ix) Reduces surface tension so that gaseous exchange by
diffusion can take place efficiently.
40. The diagram below shows exchange taking place between a red blood cell (RBC) and the fluid
surrounding active muscle tissue.

a) Name X.
b) Name an organ of the body where this pattern of exchange would not occur.
c) Explain fully how the release of oxygen is brought about.
d) Suggest a reason for the movement of chloride ions shown in the diagram.
41. Use the dissociation curve on the figure below to answer these questions.

a) The partial pressure of oxygen in the alveoli of the lungs is about 12 KPa. What is the percentage
saturation of hemoglobin in the capillaries in the lungs?
b) If 1g of fully saturated hemoglobin is combined with 1.3 cm 3 of oxygen, how much oxygen will 1g of
hemoglobin in the capillaries in the lungs combine with?
c) The partial pressure of oxygen in an actively respiring muscle is about 2kpa. What is the percentage
saturation of hemoglobin in the capillaries of such a muscle?

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 d) How much oxygen will 1g of hemoglobin in the capillaries of this muscle be combined with?
42. In a healthy adult human, the amount of hemoglobin in 1dm3 of blood is about 150g.
a) Given that 1g of pure hemoglobin can combine with 1.3 cm3 of oxygen at body temperature, how much
oxygen can be carried in 1 dm3 of blood?
b) At body temperature, the solubility of oxygen in water is approximately 0.025 cm3 of oxygen per cm3 of
water. Assuming that blood is mostly water, how much oxygen could be carried in 1 dm 3 of blood if
there if there was no hemoglobin?
43. The figure shows photomicrographs of alveoli from 1 a non smoker (x200) and 2 a smoker (x50).

a) Use the photomicrographs to describe how the lungs of this smoker differ from the lungs of the non-
smoker
b) Smokers whose lungs contain alveoli similar to those shown in photomicrograph 2 have poor health.
i. Describe the symptoms that these people may have.
ii. Explain how the structure of the lungs is responsible for this poor health.
44. The diagram below shows two cells from the lining of the trachea.

a) Name the cells P and R.

b) The structures S, T, U and W
c) Explain why cell P contains many of the structures labeled T
d) Explain the role of structure U in cell R.
e) Calculate the actual length of cell P. Show your working.
f) Describe the roles of cell P and cell R in the gas exchange system.

45. The composition of alveolar air remains fairly constant even though gases are exchanged with the blood in
the capillaries that surround the alveoli.
a) Describe the process of exchange between alveolar air and blood.
b) Explain why the composition of alveolar air remains fairly constant.

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 c) Suggest three ways in which the gas exchange system responds to the demands of oxygen.
46. Cigarette smoke contains tar, nicotine and carbon monoxide. Tar contains carcinogens.
a) Describe the effect of tar on the lining of the bronchi in the lungs.
b) Describe the effects of nicotine and carbon monoxide on the cardiovascular system.
47. Copy and complete the table below to show how much ATP is used and produced for each molecule of
glucose respired in the various stages of respiration.
ATP used ATP produced Net gain in ATP
Glycolysis
Link reaction
Krebs cycle
Oxidative phosphorylation
Total
48.
a) Explain why the energy value of lipid is more than twice that of carbohydrate.
b) Explain what is meant by respiratory quotient (RQ).
c) Copy and complete the table to show the respiratory substrates with each of the given RQs.
Respiratory substrate RQ
1.0
0.7
0.9

d) Measurements of oxygen uptake and carbon dioxide production by germinating seeds in a respirometer
showed that 25cm3 of oxygen was used and 17.5cm3 of carbon dioxide was produced over the same time
period.
i. Calculate the RQ for these seeds.
ii. Identify the respiratory substrate used by the seeds.
49. The diagram summarizes how glucose can be used to produce ATP, without the use of oxygen

Which compounds are represented by the letters X, Y and Z?

50. Distinguish between:
a) Cyclic and non cyclic photophosphorylation
b) Photophosphorylation and oxidative phosphorylation
c) The roles of NAD and NADP in a plant.

Chapter 19: Transport in animals

19.1. Overview of the chapter

Cardiac Cycle—the sequence of events in one heartbeat

 The atria continually receive blood from the veins; as pressure within the atria increases, the AV valves are
opened.
 Two-thirds of the atrial blood flows passively into the ventricles; atrial contraction pumps the remaining
blood into the ventricles; the atria then relax.
 The ventricles contract, which closes the AV valves and opens the aortic and pulmonary semilunar valves.
 Ventricular contraction pumps all blood into the arteries. The ventricles then relax. Meanwhile, blood is
filling the atria, and the cycle begins again.

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  Systole means contraction; diastole means relaxation. In the cardiac cycle, atrial systole is followed by
ventricular systole. When the ventricles are in systole, the atria are in diastole.
 The mechanical events of the cardiac cycle keep blood moving from the veins through the heart and into the
arteries.

Heart Sounds—two sounds per heartbeat: lub-dup

 The first sound is created by closure of the AV valves during ventricular systole.
 The second sound is created by closure of the aortic and pulmonary semilunar valves.
 Improper closing of a valve results in a heart murmur.

The pathway of impulses during the cardiac cycle

 The SA node in the wall of the right atrium initiates each heartbeat; the cells of the SA node are more
permeable to Na+ ions and depolarize more rapidly than any other part of the myocardium.
 The AV node is in the lower interatrial septum. Depolarization of the SA node spreads to the AV node and
to the atrial myocardium and brings about atrial systole.
 The AV bundle (bundle of His) is in the upper interventricular septum; the first part of the ventricles to
depolarize.
 The right and left bundle branches in the interventricular septum transmit impulses to the Purkinje fibers in
the ventricular myocardium, which complete ventricular systole.

Capillaries

 Carry blood from arterioles to venules.

 Walls are one cell thick (simple squamous epithelial tissue) to permit exchanges between blood and tissue
fluid.
 Oxygen and carbon dioxide are exchanged by diffusion.

Pathways of Circulation

 Pulmonary: Right ventricle →pulmonary artery →pulmonary capillaries (exchange of gases) → pulmonary
veins → left atrium.
 Systemic: left ventricle → aorta → capillaries in body tissues → superior and inferior caval veins → right
atrium
 Hepatic portal circulation: The blood from the digestive organs and spleen flows through the portal vein to
the liver before returning to the heart. Purpose: the liver stores some nutrients or regulates their blood levels
and detoxifies potential poisons before blood enters the rest of peripheral circulation.

19.2. Exercices

1. What is the alternative means for transport of substances in animals without a circulatory system? Why is
blood important for larger animals?
2. What are the two types of circulatory systems?
3. What is an open circulatory system?
4. What is a closed circulatory system?
5. What are the advantages of the closed circulatory system over the open circulatory system?
6. Why, even though they have an open circulatory system, can flying insects like flies beat their wings with
great speed?
7. What is the difference between systole and diastole?
8. What are the valves of the venous system? What is their function?
9. Concerning the thickness of their walls how different are the heart chambers?
10. What is vena cava? Which type of blood circulates within the vena cava?

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 11. Of which type of tissue is the heart made? How is this tissue oxygenated and nutrified?
12. Why is carbon monoxide toxic for humans?
13. What is the difference between double closed circulation and simple closed circulation?
14. Why is the fish circulation classified as a simple and complete circulation?
15. How is heart contraction triggered?
16. Name the following blood vessels A, B, C, and D.

17. The figure below shows a cross section through the human heart

a) Label the structures A-E

b) What are the functions of the structures B and C?

18. Cardiac muscle is described as being myogenic. What does this mean?
19. Begin at the right ventricle and describe the pathway of pulmonary circulation. Explain the purpose of this
pathway.

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 20. Describe the pathway of blood flow in hepatic portal circulation. Use a specific example to explain the
purpose of portal circulation.
21. Explain why the heart is considered a double pump. Trace the path of blood from the right atrium back to the
right atrium, naming the chambers of the heart and their vessels through which the blood passes.
22. The figure below shows pressure changes to the left side of the heart and the aorta during the cardiac cycle.

a) State what is happening at points A-D on the graph. Explain your answer.
b) If the time taken for one complete cardiac cycle is 0.8 seconds, how many cardiac cycles are there in one
minute?
23. The following are the stages in a cardiac cycle. List the correct order in which these stages occur.
A. Depolarization/excitation of sinoatrial node.
B. Ventricular systole.
C. Excitatory wave of depolarization spreads across the two atria.
D. Electrical impulses conducted by bundle of Hiss.
E. Diastole of atria and ventricles.
F. Closure of semilunar valves.
G. Sodium ions enter into the cells of SA node.
H. Activation of atrioventricular node.
I. Closure of atrioventricular node.
J. Atrial systole.
K. Electrical impulses conducted by Purkinje fibres.

24. Aneurysm is a localized blood-filled balloon-like bulge in the wall of a blood vessel. Aneurysms commonly
occur in arteries at the base of the brain and an aortic aneurysm occurs in the main artery. When the size of
an aneurysm increases there is a high risk of a rupture resulting in internal bleeding.
a) Name the:
i. main artery
ii. main vein
b) List TWO differences of the blood flow in arteries and veins.
c) Describe the type of blood received in the left ventricle.
d) The left ventricle pumps blood at higher pressure than the right ventricle. Explain how the structure
of the wall of the left ventricle is different from the wall of the right ventricle.
e) The heart keeps the blood flowing in one direction. Name the TWO types of valves that prevent the
backflow of blood.
f) Capillary beds are adapted for their function of exchange of substances. List TWO adaptations of
capillaries that facilitate exchange of substances.
25. Newly published research shows that eating egg yolks accelerates atherosclerosis in a manner similar to
smoking cigarettes. Atherosclerosis, also called coronary artery disease, is a disorder of the arteries.
a) List TWO structural features of arteries.
b) Describe the direction of blood flow in all arteries.

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 c) Coronary arteries supply blood to the heart muscle. Compare the blood supply of the renal and hepatic
arteries.
d) Name the artery which has a high carbon dioxide concentration.
e) Arteries have a pulse but veins do not have a pulse. Explain.
f) Eggs are high in cholesterol but they are still important in the diet of a body builder. Explain.
26. The figure below shows the general layout of the circulatory system of a fish.

a) How does this differ from the circulatory system of a mammal?

b) Suggest the possible advantages of the design of the mammalian circulatory system over that of a fish.
27. Which of the following could, or could not, be carried out by a red blood cell? In each case, briefly justify
your answer.
a) Protein synthesis
b) Lipid synthesis
c) Cell division
d) Active transport
28.
a) We have seen that capillary walls are not very permeable to plasma proteins. Suggest where the protein
in tissue fluid has come from.
b) The disease kwashiorkor is caused by a diet which is very low in protein. The concentration of proteins
in blood plasma becomes much lower than usual. One of the symptoms of kwashiorkor is edema. Suggest
why this is so.

29. Mount Everest is nearly 9000 m high. The partial pressure of oxygen in the alveoli at this height is only about
2.5 KPa. Explain what effect this would have on the supply of oxygen to body cells if a person climbs to the
top of Mount Everest without a supplementary oxygen supply.
30. Explain how an increase in the number of red blood cells can help to compensate for the lack of oxygen in
the air at high altitude.
31. Athletes often prepare themselves for important competitions by spending several months training at high
altitude. Explain how this could improve their performance.
32. Carbon dioxide is transported in the blood in various forms.
a) Describe how carbon dioxide molecules reach blood cells from respiring cells. The diagram below shows
part of a capillary network and some cells of the surrounding tissue.

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 b) State three ways in which the blood at Y differs from the blood at X other than in the concentration of
carbon dioxide.
c) An enzyme in red blood cells catalyzes the reaction between carbon dioxide and water as blood flows
through respiring tissues.
𝐶𝑂2 + 𝐻2 𝑂 → 𝐻2 𝐶𝑂3 → 𝐻 + + 𝐻𝐶𝑂3−
i. Name the enzyme that catalyzes this reaction.
ii. Explain the significance of this reaction in the transport of carbon dioxide.
d) The graph below shows the effect of increasing the carbon dioxide concentration on the oxygen
dissociation curve for hemoglobin.

i. State the percentage saturation of hemoglobin with oxygen at a partial pressure of 5 kpa when
the partial pressure of carbon dioxide is 1.0 kpa.
ii. The percentage saturation of hemoglobin with oxygen decreases as the partial pressure of
carbon dioxide increases. Explain how this happens.
iii. Name the effect of increasing carbon dioxide concentration on the oxygen dissociation curve.
iv. Explain the importance of the effect of carbon dioxide on hemoglobin as shown in the graph
above.
33. Mammals have a closed, double circulation.
a) State what is meant by the term double circulation.
The figure below shows part of the circulation in a mammalian tissue. The central part is enlarged to
show a capillary, a cell supplied by the capillary, and vessel Z.

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 b) Explain why the wall of the artery is thicker than the wall of a vein.
c) Suggest one role for the pre-capillary sphincter muscle shown in the figure.
d) With reference to the figure, describe the role of capillaries in forming tissue fluid.
e) Describe three ways in which plasma differs from tissue fluid.
f) Name the fluid in vessel Z.

34. The figure below shows the pressure changes in the left atrium, left ventricle and aorta throughout two cardiac
cycles.

a) How long does one heart beat (one cardiac cycle) last?
b) What is the heart rate represented on this graph, in beats per minute?
c) The contraction of muscles in the ventricle wall causes the pressure inside the ventricle to rise. When
the muscles relax, the pressure drops again. Make a copy of the diagram and mark the following periods.
i. The time when the ventricle is contracting (ventricular systole)
ii. The time when the ventricle is relaxing (ventricular diastole).
d) The contraction of muscles in the wall of the atrium raises the pressure inside it. This pressure is also
raised when blood flows into the atrium from the veins, while the atrial walls are relaxed. On your copy
of the diagram, mark the following periods:
i. The time when the atrium is contracting (atrial systole)
ii. The time when the atrium is relaxing (atrial diastole)
e) The atrioventricular valves open when the pressure of the blood in the atria is greater than in the
ventricles. They snup shut when the pressure of the blood in the ventricles is greater than in the atria. On
your diagram, mark the points at which these valves will open and close.
f) The opening and closing of the semilunar valves in the aorta depends in a similar way on the relative
pressures in the aorta and ventricles. On your diagram, mark the points at which these valves will open
and close.
g) The right ventricle has much less muscle in its walls than the left ventricle, and only develops about one-
quarter of the pressure developed on the left side of the heart. On your diagram, draw a line to represent
the probable pressure inside the right ventricle over the 1.3 seconds shown.

35. The diagram below shows a cross-section of the heart at the level of the valves.

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 a) Copy and complete the following flowchart to show the pathway of blood through the heart.

b) Explain how the valves P and Q ensure one-way flow of blood through the heart.

Chapter 20: Heterotrophic nutrition

20.1. Overview of the chapter

Function of the Digestive System—to break down food into simple chemicals that can be absorbed into the
blood and lymph and utilized by cells

Divisions of the Digestive System

 Alimentary tube—oral cavity, pharynx, esophagus, stomach, small intestine, large intestine. Digestion takes
place in the oral cavity, stomach, and small intestine.
 Accessory organs —salivary glands, teeth, tongue, liver, gallbladder, and pancreas. Each contributes to
digestion.

Types of Digestion

 Mechanical—breaks food into smaller pieces to increase the surface area for the action of enzymes.
 Chemical—enzymes break down complex organics into simpler organics and inorganics; each enzyme is
specific for the food it will digest.

End Products of Digestion

 Carbohydrates are digested to monosaccharides.

 Fats are digested to fatty acids and glycerol.
 Proteins are digested to amino acids.
 Other end products are vitamins, minerals, and water.

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Oral Cavity—food enters by way of the mouth

 Teeth and tongue break up food and mix it with saliva.

 Tooth structure —enamel covers the crown and provides a hard chewing surface; dentin is within the enamel
and forms the roots; the pulp cavity contains blood vessels and endings of the trigeminal nerve; the
periodontal membrane produces cement to anchor the tooth in the jawbone.
 The tongue is skeletal muscle innervated by the hypoglossal nerves. Papillae on the upper surface contain
taste buds (facial and glossopharyngeal nerves). Functions: taste, keeps food between the teeth when
chewing, elevates to push food backward for swallowing.
 Salivary glands—parotid, submandibular, and sublingual; ducts take saliva to the oral cavity.
 Saliva—amylase digests starch to maltose; water dissolves food for tasting and moistens food for swallowing;
lysozyme inhibits the growth of bacteria.
 The food is moved in the digestive system by peristalsis.

Small Intestine—coiled within the center of the abdominal cavity; extends from stomach to colon

 Enzymes secreted by the intestinal glands complete digestion. Surface area for absorption is increased by
plica circulares, villi, and microvilli; microvilli are the brush border.
 The villi contain capillary networks for the absorption of water-soluble nutrients: monosaccharides, amino
acids, vitamin C and the B vitamins, minerals, and water. Blood from the small intestine goes to the liver
first by way of portal circulation.
 The villi contain lacteals (lymph capillaries) for the absorption of fat-soluble nutrients: vitamins A, D, E, and
K, fatty acids, and glycerol, which are combined to form chylomicrons. Lymph from the small intestine is
carried back to the blood in the left subclavian vein.

Large Intestine (colon)—extends from the small intestine to the anus

 Colon—parts: cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal
canal.
 Ileocecal valve—at the junction of the cecum and ileum; prevents backup of fecal material into the small
intestine.
 Colon—functions: absorption of water, minerals, vitamins; elimination of undigestible material.
 Normal flora—the bacteria of the colon; produce vitamins, especially vitamin K, and inhibit the growth of
pathogens.

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The figure below shows an overview of digestion in a human being

20.2. Questions
1. What is digestion?
2. How different are intracellular and extracellular digestion? What is the evolutionary advantage of
extracellular digestion?
3. How is extracellular digestion related to cellular and tissue specialization?
4. What is the differencebetween a complete digestive system and an incomplete digestive system? How are
these types of digestive tubes associated or not to extracellular digestion?
5. What is the salivary digestive enzyme? Which type of food does it digest and into which smaller molecules
does it transform the food?
6. Why doesn't the food enter the trachea instead of going to the esophagus?

7. What is the pH inside the stomach? Why is there a need to keep that pH level? How is it maintained? Which
are the cells that produce that pH?
8. How is thegastricmucosa protected from the acid pH of the stomach?
9. Which are the three parts of the small intestine?
10. What is the substance produced in the liver that acts in the small intestine during digestion? How does that
substance act in the digestive process?
11. What are the digestive functions of the pancreas?
12. How does the pancreatic juice participate in the digestion of proteins? What are the involved enzymes?
13. What are the digestive functions of the liver?
14. Coming from the acid pH of the stomach which pH level does the chyme find when it enters the duodenum?
Why is it necessary to maintain that pH level in the small intestine? What are the organs responsible for that
pH level and how is it kept?

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 15. What are the five human digestive secretions? Which of them is the only one that does not contain digestive
enzymes?
16. Why do protease-supplying cells of the stomach and of the pancreas make only precursors of the active
proteolytic enzymes?

17. After digestion the next step is absorption done by cells of the mucous membrane of the intestine. For this
task a large absorption surface is an advantage. How is it possible in the small internal space of the body of
a pluricellular organism to present a large intestinal surface?
18. In which part of the digestive tube is water chiefly absorbed? What about the mineral ions and vitamins?
19. From the intestinal lumen through to the tissues - what is the route of nutrients after digestion?
20. What is the special route that lipids follow during digestion? What are chylomicrons?
21. Why does the ingestion of vegetable fibers improve the bowel habit in people that suffer from hard stools?
22. What are the main functions of the bacterial flora within the human gut?
23. The releasing of digestive secretions is controlled by hormones. What are the hormones that participate in
this regulation?
24. What is the function of gastrin in the digestive process and how is it produced?

25. What is the function of secretin in the digestive process and where is it produced?
26. What is the function of cholecystokin in the digestive process and how is it produced?
27. Cows swallow their food once and then this food goes back to the mouth to be chewed again. How can this
phenomenon be explained?

28. Explain the purpose of mechanical digestion, and give two examples. Explain the purpose of chemical
digestion, and give two examples.
29. The diagram below is a cross section through a part of the epithelium of the human ileum

a) Name the parts labeled A, B, and C.

b) Name the functions of B and C.
c) How is the villus specialized for the uptake of digested foods from the ileum?
30. Answer the question below on digestion
a) Explain why the protein digesting enzymes to not digest the tissues that produce them.
b) Two groups of enzymes digest proteins. They are called endopeptidases and exopeptidases. Explain
what these two groups of enzymes do. Which group is secreted first and why?
c) Complete the table below shows about the enzymes which involved in digestion.
Enzyme Site of Site of action Substrate product
production
Rennin
Trypsin
Lipases

31. The figure below represents the epithelial cells of the ileum

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 What are the adaptations of these cells that help them to perfom their functions?

32. What is the advantage of the hepatic portal circulation?

33. The diagram shows the main blood vessels going to and coming from the liver.

a) In a healthy person the blood glucose level in the hepatic vein fluctuates much less than in the hepatic
portal vein. Explain why this is so.
b) Blood sugar level is more or less constant even if a person has not eaten for several days. How does
gluconeogenesis help to maintain this constant blood sugar level?
c) Suggest why people suffering from diabetes are advised to eat their carbohydrates in the form of starch
rather than as sugars?

34. A patient was diagnosed with Esophageal Stricture. This involves narrowing or tightening of the esophagus.
a) Name the process that pushes food along the esophagus.
b) Describe the structure of the esophagus.
c) Name the flap that prevents food passing through the trachea during feeding.
d) Gastric dumping syndrome is a condition where ingested foods bypass the stomach too fast and enter
the small intestine largely undigested.
i. List TWO secretions of the stomach.
ii. Explain why the digestion of carbohydrates stops in the stomach.
iii. Name the first part of the small intestine.
e) Maltase and lactase are two enzymes found in intestinal juice secreted by the ileum.
i. Name the substrate of the enzyme lactase.
ii. Describe the enzymatic change brought about by the enzyme maltase.

Chapter 21: Reproduction and human development

21.1. Overview of the chapter

Reproductive Systems—purpose is to produce gametes (egg and sperm), to ensure fertilization, and in women
to provide a site for the embryo-fetus

Meiosis—the cell division process that produces gametes

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  One cell with the diploid number of chromosomes (46) divides twice to form four cells, each with the haploid
number of chromosomes (23).
 Spermatogenesis takes place in the testes; a continuous process from puberty throughout life; each primary
spermatocyte produces four functional sperm. FSH and testosterone are directly necessary.
 Oogenesis takes place in the ovaries; the process is cyclical (every 28 days) from puberty until menopause;
each primary oocyte produces one functional ovum and three non-functional polar bodies. FSH, LH, and
estrogen are necessary.
 Male Reproductive System—consists of the testes and the ducts and glands that contribute to the formation
of semen
 Female Reproductive System—consists of the ovaries, fallopian tubes, uterus, vagina, and external genitals.

The Menstrual Cycle—average is 28 days; includes the hormones FSH, LH, estrogen, and progesterone, and
changes in the ovaries and endometrium

 Menstrual phase—loss of the endometrium.

 Follicular phase—several ovarian follicles develop; ovulation is the rupture of a mature follicle; blood vessels
grow in the endometrium.
 Luteal phase—the ruptured follicle becomes the corpus luteum; the endometrium continues to develop.
 If fertilization does not occur, decreased progesterone results in the loss of the endometrium in menstruation.

Human Development—growth of a fertilized egg into a human individual

Fertilization—the union of the nuclei of egg and sperm; usually takes place in the fallopian tube

 Sperm undergo final maturation (capacitation) within the female reproductive tract; the acrosome contains
enzymes to digest the membrane of the ovum.
 The 23 chromosomes of the sperm join with the 23 chromosomes of the egg to restore the diploid number of
46 in the zygote.
 A zygote has 22 pairs of autosomes and one pair of sex chromosomes; XX in females, XY in males.

Implantation —5 to 8 days after fertilization

 Within the fallopian tube, the zygote begins mitotic divisions called cleavage to form two-cell, four-cell,
eight-cell stages, and so on.
 A morula is a solid sphere of cells that divides further to form a hollow sphere called a blastocyst.
 A blastocyst consists of an outer layer of cells called the trophoblast and an inner cell mass that contains the
potential embryo; the cells are stem cells, not yet specialized. The trophoblast secretes enzymes to form a
crater in the endometrium into which the blastocyst sinks.

Embryonic Membranes

 The yolk sac forms the first blood cells and the cells that become spermatogonia or oogonia. The yolk sac
degenerates early in human development.
 The allantois becomes part of the umbilical cord that links the embryo to the mother.
 The amnion surrounds the fetus and contains amniotic fluid; this fluid absorbs shock around the fetus.
 The chorion develops chorionic villi that will contain blood vessels that form the fetal portion of the placenta.

Placenta and Umbilical Cord

 The placenta secretes several hormones that prevent menstruation: HCG, estrogen and progesterone.
 The placenta is formed by the chorion of the embryo and the endometrium of the uterus; the umbilical cord
connects the fetus to the placenta.

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  Fetal blood does not mix with maternal blood; fetal capillaries are within maternal blood sinuses; this is the
site of exchanges between maternal and fetal blood.
 Two umbilical arteries carry blood from the fetus to the placenta; fetal CO2 and waste products diffuse into
maternal blood; oxygen and nutrients enter fetal blood.
 Umbilical vein returns blood from placenta to fetus.
 The placenta is delivered after the baby and is called the afterbirth.

Parturition and Labor

 Gestation period ranges from 37 to 42 weeks; the average is 40 weeks.

 Labor: first stage—dilation of the cervix; uterine contractions force the amniotic sac into the cervix;
amniotic sac ruptures and fluid escapes.
 Labor: second stage—delivery of the infant; oxytocin causes more powerful contractions of the
myometrium. If a vaginal delivery is not possible, a cesarean section may be performed.
 Labor: third stage—delivery of the placenta; the uterus continues to contract to expel the placenta, then
contracts further, decreases in size, and compresses endometrial blood vessels.

The Infant at Birth

 Umbilical cord is clamped and severed; increased CO2 stimulates breathing, and lungs are inflated.
 Foramen ovale closes, and ductus arteriosus constricts; ductus venosus constricts; normal circulatory
pathways are established.
 Jaundice may be present if the infant’s immature liver cannot rapidly excrete bilirubin.

21.2. Questions
1. What are gametes?
2. What is the type of cell division that allows sexual reproduction? What is gametogenesis?
3. What is the name of the cells capable of making gametes? What is the ploidy of these gamete-forming cells?
4. What are gonads? What are the male and the female gonads in humans?
5. What is the acrosome of the sperm cell? How is it formed?
6. Draw a sperm cell and show its main parts.
7. What is the function of the flagellum of the sperm cell? How is it formed?

8. What are the main differences between spermatogenesis and oogenesis?

9. What is the relationship between the menstrual cycle and ovulation?
10. How does the male gamete penetrate the egg cell? How does the female gamete protect itself from the
entrance of more gametes after the entrance of the first sperm cell?
11. Concerning their size and basic morphology how and why do the male and the female gametes differentiate
from each other?
12. What is the function of the secretions of the prostate, seminal vesicle and bulbourethral glands in
reproduction?
13. What are the endocrine glands that regulate sexual activity in males? How does this regulation work and what
are the involved hormones?
14. What are the endocrine glands involved in the menstrual cycle? What are the hormones in action?
15. What event marks the beginning of the menstrual cycle? What is the blood concentration of FSH, LH,
estrogen and progesterone in this phase of the cycle?
16. What is the hormone secreted by the growing ovarian follicles? What is the action of that hormone upon the
uterus?
17. What is the structure into which the follicle is transformed after ovulation? What is the importance of that
structure in the menstrual cycle?
18. Which are the phases of the menstrual cycle?
19. In general what is the phase of the menstrual cycle when copulation may lead to fecundation?
20. What is the endocrine function of the placenta?

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 21. What is parthenogenesis?
22. What is gastrulation? How during gastrulation are the first two germ layers formed? What are these germ
layers?
23. What are twins? Genetically what are the two types of twins that can be generated?
24. Study the diagram of the male reproductive system below

a) Label A to F.
b) Explain the functions of B and E.
c) Why is E located on the outside of the body?

25. Name all the ducts, in order, that sperm travel through from the testes to the urethra.
26. Which female hormones have the following functions in menstrual cycles
a) Maintains the endometrium
b) Brings about ovulation
c) Brings about the formation of the corpus luteum.
d) Secreted from the pituitary.
e) Stimulates the development of a follicle.
27. Answer the question below on the reproductive system.
a) What features of the placenta aid in the transfer of materials between the mother and the fetus?
b) Why does maternal blood never come into direct contact with fetal blood?
c) Name two substances that enter the umbilical vein and two substances that leave the umbilical artery.
d) What is the role of the amniotic fluid?

28. Study the following diagram on hormonal levels during the menstrual cycle and answer the questions that
follow

a) In which period is menstruation taking place?

b) What gland produces LH and FSH?
c) What is the effect of the rise in LH?

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 d) Which hormones stimulate the thickening of the uterine wall?
e) In which day is ovulation likely and why?
29. Identify three events that occur as a fetus grows and develops.
30. Why is an embryo generally more susceptible than a fetus to damage by toxins in the mother’s blood?
31. Why is the umbilical cord cut before a newborn has started to breathe on its own?
32. The figure below shows, in outline, the process of fertilization. Identify the cells labeled A-E. For each cell
indicate whether it is diploid (2n) or haploid (n).

33. Copy and complete the table to show, for each hormone, the precise site of its secretion, and its effects on
the ovary or on the endometrium of the uterus.
Hormone Site of secretion Effect(s) of hormone

Ovary Endometrium

FSH None

LH None

Estrogens None

Progesterone None

Chapter 22: Support and movement

22.1. Overview of the chapter

The skeleton is made of bone and cartilage and has these functions:

 Is a framework for support, connected by ligaments, moved by muscles.

 Protects internal organs from mechanical injury.
 Contains and protects red bone marrow.
 Stores excess calcium; important to regulate blood calcium level.

Bone Tissue

 Osteocytes (cells) are found in the matrix of calcium phosphate, calcium carbonate, and collagen.
 Compact bone—haversian systems are present.
 Spongy bone— no haversian systems; red bonemarrow present.

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  Articular cartilage— smooth, on joint surfaces.
 Periosteum—fibrous connective tissue membrane; anchors tendons and ligaments; has blood vessels that
enter the bone.

The Skeleton—206 bones; bones are connected by ligaments

 Axial— skull, vertebrae, rib cage.

 Appendicular— bones of the arms and legs and the shoulder and pelvic girdles.

Joints—Articulations

Classification based on amount of movement:

 Synarthrosis—immovable.
 Amphiarthrosis—slightly movable.
 Diarthrosis—freely movable

Synovial joints—all diarthroses have similar structure

 Articular cartilage— smooth on joint surfaces.

 Joint capsule—strong fibrous connective tissue sheath that encloses the joint.
 Synovial membrane—lines the joint capsule; secretes synovial fluid that prevents friction.
 Bursae—sacs of synovial fluid that permit tendons to slide easily across joints.

Muscle Fiber—microscopic structure

 Neuromuscular junction: axon terminal and sarcolemma; the synaptic cleft is the space between. The axon
terminal contains acetylcholine (a neurotransmitter), and the sarcolemma contains cholinesterase
 Sarcomeres are the contracting units of a muscle fiber. Myosin and actin filaments are the contracting proteins
of sarcomeres. Troponin and tropomyosin are proteins that inhibit the sliding of myosin and actin when the
muscle fiber is relaxed.
 The sarcoplasmic reticulum surrounds the sarcomeres and is a reservoir for calcium ions.

Contraction—the sliding filament mechanism

 Depolarization stimulates a sequence of events that enables myosin filaments to pull the actin filaments to
the center of the sarcomere, which shortens.
 All of the sarcomeres in a muscle fiber contract in response to a nerve impulse; the entire cell contracts.
 Tetanus is a sustained contraction brought about by continuous nerve impulses; all our movements involve
tetanus.
 Paralysis may be the result of nerve damage, spinal cord damage, or brain damage.

22.2. Exercices

1. Identify an example of a cell, a tissue, and an organ of the skeletal system.

2. Identify the main bones of the appendicular skeleton.
3. List four functions of bones and the skeleton.
4. Name the three main types of joints, and identify a location in the body that is an example of that type of
joint.
5. Identify the three types of muscle in the body, and give an example of where each type is found.
6. Which type of muscle cell is multinucleated?
7. Which type of muscle cell metabolism results in the greater production of ATP, aerobic or anaerobic? Give
a reason for your answer.
8. Describe the components of a sacromere.

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 9. What are the main proteins that constitute the sarcomere? What is the function of those molecules in the
muscle cells?
10. How do calcium ions participate in muscle contraction? Why do both muscle contraction and muscle
relaxation spend energy?
11. What is myoglobin? What is the function of this molecule in the muscle tissue?
12. What happens when the oxygen supply is insufficient to maintain aerobic cellular respiration during muscle
exercise?
13. Explain the differences between compact bone and spongy bone, and state where each type is found.
14. State the locations of red bone marrow, and name the blood cells it produces.
15. Name the part of a synovial joint with each of the following functions:
a) Fluid within the joint cavity that prevents friction
b) Encloses the joint in a strong sheath
c) Provides a smooth surface on bone surfaces
d) Lines the joint capsule and secretes synovial fluid
16. Name the two sources of oxygen for muscle fibers. State what the two proteins have in common.
17. The figure below shows tha anterior view of the rib cage

With what bones do all of the ribs articulate?

18. Name these parts of the neuromuscular junction:
a) The membrane of the muscle fiber
b) The end of the motor neuron
c) The space between neuron and muscle cell
19. Where is the sarcoplasmic reticulum located and what does it contain?
20. State the function of tendons. Name the part of a muscle and a bone to which a tendon is attached.
21. State the term for:
a) Muscles with the same function
b) Muscles with opposite functions
22. With the help of a drawing, show the structure of a synovial joint.
23. The diagram below shows an electron micrograph of a longitudinal section of myofibril in striated muscle.

a) Name the regions A, B, C, D and E.

b)
i) State the name of the protein present in the thick filament.
ii) State the name of the protein which forms the main component of the thin filament and name
the two accessory proteins.
c) State the role of the following in skeletal muscle contraction:

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 i) ATP
ii) Calcium ions in sarcoplasm.
d) State how the following will change during muscle contraction.
i) Sarcomere
ii) A bands
iii) I bands
iv) H zone

24. The electron micrograph shows parts of some myofibrils in a striated muscle that is in a relaxed state.

a) Name the parts labeled K, L and M.

b) How many myofibrils are visible in the electron micrograph?
c) There are many glycogen granules and mitochondria visible in the electron micrograph. Explain why
there are both there.
d) Describe how you can tell that this electron micrograph is from a relaxed muscle and not a contracted
muscle.
e) The electron micrograph is magnified 20,000 times. Calculate the actual length of the sarcomere which
includes the region labeled K. Give your answer in micrometers (µm).

25. A biopsy was taken from a leg muscle of a healthy racehorse. The muscle fibers were teased apart and cross-
sections were taken from one of the muscle fibers. These cross-sections were examined with a transmission
electron microscope. The figure below shows drawings made from three different cross-sections of a
myofibril from the muscle fiber.

a) Explain the difference from the sections X, Y and Z. You may draw a labelled diagram to illustrate your
answer.

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 b) The sections were taken from a relaxed muscle fiber. Suggest how the sections would appear if taken
from a fiber that had contracted to its maximum extent. Explain your answer.
c) Muscle weakness in racehorses may sometimes be related to a deficiency of calcium. Outline the roles
of calcium ions in the coordination of muscle contraction.

Chapter 23: Genetics

23.1. Overview of the chapter

 Genetics: The branch of biology that focuses on heredity in organisms.

 Allele: Different versions of a gene.
 Genotype: An organism’s genetic makeup.
 Heredity: The passing of characteristics from parent to offspring.
 Heterozygous: Organisms that have two different alleles for a gene.
 Homozygous: An organism that has an identical pair of alleles for a trait.
 Phenotype: An organism’s physical traits.
 Recessive: The allele that is expressed only in the absence of a dominant allele.
 Trait: A heritable variant of a characteristic, such as purple or white flower color.
 True-breeding: A plant that will always produce offspring with the parental trait when they self-pollinate.
 Modern genetics is based on Mendel’s explanation of how traits are passed from generation to generation.
 Mendel’s use of mathematics in his pea plant studies was important to the confidence he had in his results.
 Mendel carried out his first experiments with true-breeding plants and continued them over a span of three
generations.
 For each of the seven characteristics Mendel studied, he observed a similar ratio in the inheritance of
dominant to recessive traits (3:1) in the F2 generation.
 Mendel developed a theory that explained simple patterns of inheritance in which two alleles are inherited to
result in one of several traits in offspring.
 The law of segregation states that a pair of alleles is segregated during the formation of gametes and that each
gamete has an equal chance of getting either one of the allele.
 The law of independent assortment states that the inheritance of one trait will not affect the inheritance of
another. That is, genes are inherited independently of each other.
 Linked genes are genes that are close together on the same chromosome. Linked genes are inherited together.
 Mendelian inheritance patterns can be seen in humans. Albinism is a genetic disorder that is inherited as a
simple Mendelian trait.
 Genotype determines phenotype. A homozygous dominant or a heterozygous genotype will always show a
dominant phenotype. A homozygous recessive genotype can only show a recessive phenotype.
 A Punnett square shows all the possible genotypes that can result from a given cross.
 A testcross examines the genotype of an organism that shows the dominant phenotype for a given trait.
 The heterozygous organism is crossed with an organism that is homozygous recessive for the same trait.
 A dihybrid cross-examines the inheritance of two traits at the same time.
 A pedigree can help geneticists discover if a trait is sex-linked, if it is dominant or recessive, and if the person
(or people) who have the trait are homozygous or heterozygous for that trait.
 Carrier: A person who is heterozygous for a recessive allele of a trait.
 Codominance: Occurs when both traits appear in a heterozygous individual.
 Incomplete dominance: Occurs when the phenotype of the offspring is somewhere in between the
phenotypes of both parents; a completely dominant allele does not occur.
 Mendelian trait: A trait that is controlled by a single gene that has two alleles.
 Multiple alleles: When three or more alleles determine a trait, such as with the human ABO blood group.
 Polygenic traits: Traits that are affected by more than one gene.
 Punnett square: A diagram that helps predict the probable inheritance of alleles in different crosses.
 Sex chromosome: A chromosome that determines the sex of an organism.

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  Sex-linked trait: A trait whose allele is found on a sex chromosome.
 Testcross: A cross used to determine an unknown genotype.

23.2. Questions
1. What is a gene?
2. How is the concept of chromosome related to the concept of the gene?
3. What is meant by “gene locus”?
4. What are alleles of a gene?
5. What is a phenotype?
6. Summarize the law of segregation.
7. Summarize the law of independent assortment.
8. Why can’t you always identify the genotype of an organism from its phenotype?

9. How do the Punnett squares for a monohybrid cross and a dihybrid cross differ?
10. Mendel carried out a dihybrid cross to examine the inheritance of the characteristics for seed color and seed
shape. The dominant allele for yellow seed color is Y, and the recessive allele for green color is y. The
dominant allele for round seeds is R, and the recessive allele for a wrinkled shape is r. The two plants that
were crossed were F1 dihybrids RrYy. Identify the ratios of traits that Mendel observed in the F2 generation,
and explain in terms of genotype what each number means. Create a Punnett square to help you answer the
question.
11. Draw a pedigree that illustrates the passing of the dominant cleft chin trait through three generations. A
person who has two recessive alleles does not have a cleft chin. Let us say that C is the dominant allele, c is
the recessive allele.
12. A classmate tells you that a person can have type AO blood. Do you agree? Explain.
13. Mendelian inheritance does not apply to the inheritance of alleles that result in incomplete dominance and
codominance. Explain why this is so.
14. The house mouse has 40 chromosomes in its somatic cells. It has a sex determining system similar to humans.
a) How many chromosomes does the mouse receive from its mother?
b) How many sex chromosomes are present in its gamete?
c) How many autosomes will a mouse receive from its father?

15. A mule is produced when a donkey mates with a horse. Horses have a diploid number of 64 and donkeys, a
diploid number of 62.
a) What would you expect the diploid number of a mule to be?
b) Would you expect the mule to be fertile or not. Explain.

16.
a) Contrast linked genes and sex linked genes.
b) The deposition of starch in pollen grains in maize is controlled by the presence of one allele of a certain
gene. The other allele of that gene results in no starch being deposited. Explain in terms of meiosis why
half the pollen grains produced by a heterozygous maize plant contain starch.
c) Calculate the number of different combinations of chromosomes in the pollen grains of the crocus
(Crocus balansae) which has a diploid number of 6.
d) Distinguish continuous and discontinuous variation.
e) What are mutagens? Give also one example of a mutagen.
17.
a) What do you understand by the rhesus factor?
b) How does the Rhesus factor influence blood transfusion?
c) A woman with negative Rhesus marries a man who is positive Rhesus. What is the likely fate of the
offspring?
18. A homozygous purple-flowered short-stemmed plant was crossed with a homozygous red-flowered long-
stemmed plant and the F1 phenotypes had purple flowers and short stems. When the F1 generation was test
crossed with a double homozygous recessive plant, the following progeny were produced.
- 52 purple flower, short stem
- 47 purple flower, long stem

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 - 49 red flower, short stem
- 45 red flower, long stem
Explain these results fully.

19. In an experiment, a homozygous tomato plant with a purple hairy stem was crossed with a homozygous
tomato with a green, hairless stem. Both purple and hairy are dominant. The F1 plants were allowed to self
pollinate to produce an F2. The F2 seeds were planted and the resulting phenotypes are shown below:
Purple, hairy stem 150
Purple, hairless stem 48
Green, hairy stem 15
Green, hairless stem 15
a. What is the ratio of phenotypes in the F2?
b. What was the expected ratio of phenotypes? Why?
c. Why do you think there is a difference between the observed and expected results?
d. What could be the results if the two genes were linked?
20. Answer the following question on genetics
a) Define the words below
i. Allele
ii. Locus
iii. Autosome
iv. Homologous chromosome
b) State and explain the laws of Mendel.
c) Some coat colours in cats are sex linked. Black coat colour is codominant to ginger. A cat that has one
allele for black and one for ginger is tortoiseshell. The gene for this coat colour is carried on the X
chromosome. Describe the genotype and phenotype of the offspring of a cross between a pure breeding
black female cat and a ginger male cat.
21. Homozygous purple-stemmed tomatoes were crossed with green-stemmed plants. The F1 were all purple-
stemmed. When the F1 plants were allowed to self-pollinate the resulting F2 produced 310 purple-stemmed
plants and 120 green-stemmed plants.
a) Which is the dominant allele?
b) Draw a genetic diagram to show the F1 and F2 crosses.
c) The F1 plants were back-crosses to a green-stemmed plant. The F2 were 47 purple-stemmed plants and
55 green-stemmed plants. Draw a genetic diagram to show this back cross.
22. Homozygous tall, white flowered plants were crossed with homozygous short, red-flowered plants. Tall and
white are dominant to short and red.
a) What are the genotypes of the parent plant?
b) What is the genotype and phenotype of the F1?
c) By means of a genetic diagram, show what happens when the F1 plants are back-crossed to a recessive
plant.
d) Give the genotypes and the ratios of the phenotypes of the F 2.
23. In dogs, dark coat colour (D) is dominant to albino (d), and short hair (H) is dominant to long hair (h). These
two genes are not linked. A pure-breeding, dark, short-haired dog is crossed with a pure-breeding albino
long-haired dog.
a) What is the genotype and phenotype of the F1 puppies?
b) Two of the F1 dogs are crossed and an F2 produced. Draw a punnet square to show the parental gametes
and the genotypes and phenotypes of the offspring. What is the F 2 ratio of phenotypes?
24. When red-flowered petunia plants are crossed with white-flowered plants, all the resulting F1 plants have
pink flowers.
a) Explain how this is possible using genetic diagrams.
b) The F1 plants are crossed to produce an F2. Draw a genetic cross to show the genotypes and phenotypes
of the F2 plants.
25. The pedigree below traces the inheritance of a very rare biochemical disorder. Affected individuals are
indicated by filled-in circles and squares. Is the allele for this disorder dominant or recessive? What genotypes
are possible for the individuals marked 1, 2 and 3?

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 26. Red-color blindness is a sex-linked recessive condition. The gene for colour blindness is carried on the X
chromosome. The figure below shows a family tree. Work out the genotype of the individual labeled A-E.

27.
a) Explain what is meant by linkage.
b) If you were investigating the inheritance of two genes and you started with two pure-breeding parents,
what ratio of phenotypes would you expect in the F2 if the genes were linked? Why? What would be the
expected ratio if the genes were unlinked?
28. The pedigree below traces the inheritance of alcaptonuria, a biochemical disorder. Affected individuals,
indicated here by the filled-in circles and squares, are unable to break down a substance called alkapton,
which colors the urine and stains body tissues. Does alkaptonuria appear to be caused by a dominant or
recessive allele? Fill in the genotypes of individuals whose genotypes you know. What genotypes are possible
for each of the other individuals?

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 29. In the guinea pig (cavia), there are two alleles for hair colour, black and white, and two alleles for hair length,
short and long. In a breeding experiment all the F1 phenotypes produced from a cross between pure-breeding,
short black-haired and pure-breeding, long white-haired parents had short black hair. Explain
a) Which alleles are dominant, and
b) The expected proportions of the F2 phenotypes.

30. Flower colour in sweat pea plants is determined by two allelomorphic pairs of genes (R,r and S,s). If at least
one dominant allele from each allelomorphic pair is present the flowers are purple. All the other genotypes
are white.
If two purple plants, each having the genotype RrSs are crossed, what will be the phenotypic ratio of
offspring?

31. In chickens, the shape of the comb is determined by two genes. There are four shapes of comb: pea, rose,
walnut and single.
A pea-shaped comb is produced when there is at least one dominant allele for the pea shape (P) and recessive
alleles for the rose comb.
A rose comb is produced in the presence of at least one dominant allele for rose shape (R) and recessive
alleles for pea.
A walnut comb is produced when there are dominant alleles for both pea and rose.
A single comb is a double recessive genotype.
Two pure breeding chickens are crossed, one with a pea shape (P) and the other with a rose comb (R).
a) What are the parental genotypes?
b) What is the genotype and phenotype of the F1?
c) The F1 chickens are crossed to produce an F2. Draw a punnet square, showing the gametes of the parents,
the genotypes and phenotypic ratios of the offspring.

32. A man with blood group B marries a woman with blood group AB. Indicate the type of blood group that their
children will not have. Show your working.
33. Describe how crossing-over, independent assortment, and random fertilization lead to genetic variation.
34. Coat color in rabbits is inherited as a series of multiple alleles. This means that there can be more than just
two alleles for a single gene. In the case of coat color in rabbits, there are four alleles, and each one is
expressed with a different phenotype. Examine the table below and use the information in it to answer the
questions. Remember, each rabbit can have only two alleles for coat color.

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 Table: coat color in rabbits

Phenotype Allele Pattern of inheritance

Dark gray coat C Dominant to all other alleles

Chinchilla cch Dominant to Himalayan and to white

Himalayan ch Dominant to white

White c Recessive

a) List all possible genotypes for a

i. Dark gray-coated rabbit (there are 4).
ii. Chinchilla rabbit (there are 3).
iii. Himalayan rabbit (there are 2).
iv. White rabbit (there is 1).
b) Predict the phenotype from the crossing between a rabbit with a c chch and that with a Cch genotype.
c) Would it be possible to obtain white rabbits if one parent is white and the other is chinchilla? Explain your
answer.
d) Would it be possible to obtain chinchilla rabbits if one parent is himalayan and the other is white? Explain.
e) A chinchilla rabbit is mated with a Himalayan. Some offspring are white. What are the parents’ genotypes?

35. Rett syndrome is a neurodevelopmental disorder of the grey matter of the brain. Rett syndrome is a sex-
linked dominant condition (represented by R) and the disease-causing gene is located on the X chromosome.
a) The grey matter in the brain includes regions involved in muscle control and sensory perceptions such
as seeing and hearing.
i. Name the part of the brain responsible for co-ordination of movement.
ii. Name the endocrine gland present within the brain.
iii. Describe ONE structural feature that protects the brain.
b) The following diagram shows the pattern of inheritance of the Rett syndrome in a family.

Draw a genetic diagram to explain why all four children (Silvio, Miriam, Helga and Sheryl) are not affected
by the Rett Syndrome. In your answer indicate clearly the genotype of the son (Silvio) and the genotype of
the daughters (Miriam, Helga and Sheryl).
c) Explain why the sons of a father affected with Rett syndrome will not be affected by the disorder.

36. In sweet-pea plants, the gene A/a controls flower colour. The dominant allele gives purple flowers and the
recessive allele red flowers. A second gen, B/b, controls the shape of pollen grains. The dominant allele gives
elongated grains and the recesive allele spherical grains. A plant with the genotype AaBb was test-crossed

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 by interbreeding it with a plant with red flowers and spherical pollen grains. With a Punnet square, show the
expected ratio of phenotypes of the offspring of this cross.
37. In peas, the allele for colored seed (C) is dominant over the allele for colorless seed (c). The allele for starchy
endosperm (W) is dominant over the allele for waxy endosperm (w). Pure breeding plants with colored seeds
and starchy endosperm were crossed with pure breeding plants with colorless seeds and waxy endosperm.
a) State the genotype and the phenotype of the F1 individuals as a result of this cross.
b) The F1 plants were crossed with plants that had the genotype ccww. Calculate the expected ratio of
phenotypes in the F2 generation, assuming that there is independent assortment.
c) The observed percentages of phenotypes in the F2 generation are shown below:
Colored starchy 37 % Colorless starchy 14 %
Colored waxy 16 % Colorless waxy 33%
Explain the reasons for the observed results of the cross differing significantly from the expected
results.
38. Using the CR and CW alleles for codominance in snapdragon flower color, show how two plants could
have some white flowered offspring, some pink-flowered offspring and some red-flowered offspring
within one generation.
39. The diagram below shows the pedigree of a family with red-green color blindness, a sex linked condition.

a) Define the term sex linkage.

b) Deduce, with a reason, whether the allele producing the condition is dominant or recessive.
c) Determine all the possible genotypes of the individual (2 nd generation-1) using appropriate symbols.
d) Determine all the possible genotypes of the individual (3 rd generation-4) using appropriate symbols.

40. In most people, the first amino acids in their β-globin polypeptide chains are:

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 The DNA triplet for the sixth amino acid (Glu) in most people is CTT. In some people this DNA triplet
is CAT.
a) What type of mutation is the change from CTT to CAT?
b) Use the genetic code above to identify the amino acid in the β-globin polypeptide chains of people
with this mutation.
c) State the consequences for a person of having two copies of the mutated gene.

41. Suggest why:

a) A mutation in which one nucleotide of a triplet code is altered often makes no difference to the protein
molecule coded by the DNA.
b) The addition or deletion of three nucleotides in the DNA sequence of a gene often has less effect on
the encoded protein than the addition or deletion of a single nucleotide.

Chapter 24: Ecology

24.1. Overview of the chapter

 Ecology is the scientific study of living things and their relationships with the environment. Levels of
organization in ecology include the biosphere, population, community, and ecosystem.
 An ecosystem is a natural unit consisting of all the living organisms in an area functioning together with
all the non-living physical factors of the environment. Each species has a unique role in an ecosystem,
called its niche. The physical environment where a species lives is its habitat.
 Niche: The role of a species in its ecosystem; includes all the ways species’ members interact with the
abiotic and biotic components of the ecosystem.
 Organism: A life form consisting of one or more cells.
 Population: Organisms of the same species that live in the same area and interact with one another.
 Abiotic components: The non-living physical aspects of the environment; includes sunlight, soil,
temperature, wind, water, and air; also known as abiotic factors.
 Biosphere: The areas of Earth where all organisms live; extends from about 11,000 meters below sea
level to 15,000 meters above sea level.
 Biotic components: The living organisms in the environment; also known as biotic factors.
 Carrying capacity: The maximum population size that a particular environment can support without
habitat degradation.

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  Community: Populations of different species that live in the same area and interact with one another.
 Competitive exclusion principle: States that two different species cannot occupy the same niche in the
same geographic area for very long.
 Habitat: The physical environment to which an organism has become adapted and in which it can survive.
 Producers in ecosystems are autotrophs. They use energy from sunlight or chemical compounds to
synthesize organic molecules from carbon dioxide and other simple inorganic molecules.
 Consumers in ecosystems are heterotrophs, or organisms that consume other organisms for food.
Consumers include herbivores such as deer, carnivores such as lions, and omnivores such as humans.
 Decomposers break down dead organisms and other organic wastes in ecosystems. They resupply
producers with the elements they need to synthesize organic compounds.
 Food chains and food webs model feeding relationships in ecosystems. They show how energy and
materials are transferred between trophic level when consumers eat producers or other organisms.
 Density dependent factors include resource limitations, such shortages of food or nesting sites, and are
triggered by increasing population density.
 Density-independent factors, such as weather, floods and fire, reduce the population by the same
proportion, regardless of the population’s size. For example, if a forest fire destroys a population of lions,
it does not matter if the population of lions is 1 or 100.
 Detritivores: Organisms that consume the remains of dead plants (detritus).
 Detritus: Dead leaves and other plant remains that accumulate on the ground or at the bottom of a body
of water.
 Food chain: A simple linear pathway through which energy and materials are transferred from one
species to another in an ecosystem.
 Food web: A diagram of feeding relationships that includes multiple intersecting food chains.
 Herbivores: Organisms that consume only producers such as plants or algae; form a necessary link
between producers and other consumers.
 Heterotrophs: Organisms that depend on producers or other types of organisms for food; also called
consumers.
 Omnivores: Organisms that eat both plants and animals as primary food sources.
 Photosynthesis: The process by which carbon dioxide and water are converted to glucose and oxygen,
using sunlight for energy.
 Phytoplankton: All the tiny photoautotrophs found on or near the surface of a body of water; usually is
the primary producer in aquatic ecosystems; includes both cyanobacteria and algae.
 Plankton: Large communities of producers and herbivores; made up of phytoplankton and zooplankton.
 Producers: Organisms that produce organic compounds from energy and simple inorganic molecules.
 Symbiosis: Literally, "living together". Many cases of symbiosis are mutual, in which both organisms
rely on each other for survival. Other types of symbiosis include parasitism, in which one organism
benefits at its host's expense, and commensalisms, in which one partner benefits and the other is neither
benefitted nor harmed.
 Biogeochemical cycles are closed loops through which chemical elements or water move through
ecosystems. Examples of biogeochemical cycles include the water cycle, carbon cycle, and nitrogen cycle.
 The water cycle recycles water through ecosystems. Processes by which water changes state in the water
cycle include evaporation, sublimation, transpiration, and condensation.
 The organic pathway of the carbon cycle moves carbon from the atmosphere, through producers and other
organisms in ecosystems, and back to the atmosphere. The geological pathway moves carbon from the
atmosphere, through the ocean to rocks and the mantle, and back to the atmosphere.
 The nitrogen cycle moves nitrogen gas from the atmosphere into soil or water, where nitrogen-fixing
bacteria convert it to a form that producers can use. Nitrifying bacteria help nitrogen cycle through
ecosystems. Denitrifying bacteria return nitrogen gas back to the atmosphere.

24.2. Questions
1. What is a species?
2. What is a population?
3. What is the difference between an ecological niche and a habitat?
4. What are biotic factors?
5. What are abiotic factors?

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 6. What is an ecosystem?
7. What is a biosphere?
8. What are autotrophic beings? What are heterotrophic beings?
9. What are the phytoplankton and the zooplankton?
10. What is the group of aquatic beings composed of a large number of photosynthetic beings?
11. How is energy transferred along a food chain?
12. What is the difference between the concepts of food chain and food web?

13. What are the three main types of trophic pyramids studied in Ecology?
14. In a numeric pyramid is it possible for the base to be smaller than the other levels?
15. What do biomass pyramids represent?
16. What do energy pyramids represent?
17. Define three different types of consumers, and name an example of each.
18. How do decomposers resupply elements to producers?
19. How is energy transferred between trophic levels in a food chain?
20. If one million kilocalories of energy are stored in producers in an ecosystem, how many kilocalories can
be transferred to tertiary consumers in the ecosystem? Show the calculations that support your answer.
21. Draw a terrestrial food chain that includes four trophic levels.

22.
a) Define the following ecological terms
i. Eutrophication
ii. Carrying capacity
iii. Climax community
b) What is the difference between density dependent factors and density independent factors?
c) Analyze the following food webs and answer to the questions below:

i) Identify a producer and a tertiary consumer.

ii) Explain the meaning of primary and secondary production of an ecosystem.
iii) Explain why there are no food chains with more than five trophic levels in this food web.
23. Analyze the pyramid of energy below

i. There are no units on this pyramid. Suggest suitable units which could have been used to record
energy.
ii. Calculate the percentage energy transfer between the secondary and tertiary consumers.

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 iii. Give two reasons why the percentage transfer of energy between trophic levels is low.
iv. Why are pyramids of energy more informative than pyramids of numbers and pyramids of
biomass?
24. The bottom of the pyramid of biomass for the English Channel is often inverted as shown below. Suggest
a reason for this inversion.

25. What is the difference between gross and net primary productivity?
26. The diagram below shows the flow of energy through the organisms at different levels in a habitat.

a) What percentage of the solar energy falling on the habitat is trapped by the producers?
b) Study the diagram and then calculate the missing energy values A and B.
i. A .........................
ii. B ..........................
c) In this habitat the 1st consumers are small invertebrates such as snails, earthworms and insects. The
3rd consumers are foxes and hawks.
i. Examine the proportion of their total energy intake used in respiration by the 1 st and 3rd
consumers. Which uses the greater proportion? Show your working.
ii. Suggest the explanation for the difference in these proportions considered in c (i) above?
iii. There are only five feeding levels in this habitat. Suggest why we can not have a sixth
feeding level?
27. Distinguish between renewable and nonrenewable resources, and relate these concepts to the Laws of
Energy.
28. Classify the following resources as renewable or nonrenewable: coal, copper, iron, natural gas, nuclear
power, oxygen, sunlight, water, wood, wool. Briefly explain your reasoning for each resource.
29. The diagram below shows the quantity of energy flowing through a food chain in a terrestrial
ecosystem. The figures given are in KJm-2yr-1.

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 a) Calculate the percentage of the incident energy which becomes available as the net primary
production (NPP) of green plants. Show your working.
b) Give two reasons why not all the energy of the incident sunlight is incorporated into biomass of
green plants.
c) Using information shown in the diagram, explain why the biomass of insectivorous birds is usually
very much less than the biomass of caterpillars.

30. The following diagram shows the feeding relationships between the organisms living in the Antarctic.

a) Write the term that describes the feeding relationships between the organisms shown in the
diagram.
b) From the diagram write a food chain that includes the crustacean krill and has five trophic levels.
c) Explain how a drop in the krill population affects the population of penguins.
d) Phytoplankton are microscopic organisms that inhabit the upper sun-lit layer of oceans. Explain
why phytoplankton live in the well-lit surface layer of oceans.
e) Explain how the amount of energy changes along a food chain.

Chapter 25: Evolution

25.1. Overview of the chapter

 The Theory of Evolution has changed how we see ourselves and how we relate to our world.
 The theory has two basic ideas: the common ancestry of all life, and natural selection.
 Darwin studied medicine and theology, but he first worked as ship’s naturalist on the HMS Beagle.
 During the 5-year voyage, Darwin spent over 3 years on land exploring new rocks, fossils, and species.
 Like all scientific theories, Darwin’s was a product of both his own work and the work of other scientists.
 Before Darwin, most people believed that all species were created and unchanging about 6000 years ago.
 Jean-Baptiste Lamarck proposed that acquired characteristics could be inherited. Evidence did not support
his mechanism for change, but Darwin shared his ideas of change in species.
 The two general ideas of Darwin’s Theory are evolution and natural selection.

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  The concept of natural selection includes these observations and conclusions:
 By chance, heritable variations exist within a species.
 Species produce more offspring than can survive.
 Offspring with favorable variations are more likely to survive to reproduce.
 Gradually, individuals with favorable variations make up more of the population.
 Variation among individuals within species ensures that some will survive environmental change.
 Because some variations help survival in a specific habitat more than others, individuals having those
variations are more likely to survive and reproduce.
 This differential survival and reproduction results in a population which is adapted to its environment.
 The result of natural selection is gradual change in species, and when enough changes have accumulated,
new species form. This is “descent with modification.”
 The idea that natural selection has led to the origin of all species, together with evidence from the fossil
record, means that all existing species are related by “common ancestry.”
 Evolution by natural selection explains the history of life as recorded in the fossil record.
 Common ancestry explains the similarities, and natural selection in the face of environmental change
explains the differences among present-day species.

25.2. Questions
1. What is the spontaneous generation hypothesis?
2. What was the experiment of Stanley Miller (1953) on the origin of life?
3. Historically what were the two main evolutionary theories?
4. What is lamarckism?
5. Who was Charles Darwin?
6. What is the mechanism described by Darwin that eliminates species less adapted to environmental
conditions?
7. How did Darwin reach the principle of natural selection from the observation of differences among
individuals of the same species?
8. What are the fundamental similarities and differences between lamarckism and darwinism?
9. State 3 of the 5 ideas Darwin developed during the Voyage of the Beagle. For each idea, give and example
of a specific observation he made which supports the idea.
10. What does the expression “standing on the shoulders of giants” say about Darwin and his Theory of
Evolution? Support your interpretation with at least three specific examples.
11. Summarize in your own words the two basic ideas which make up Darwin’s Theory of Evolution.
12. Compare and contrast Lamarck’s and Darwin’s ideas using the evolution of the human brain as an
example.
13. Why is it not correct to say that evolution means “we came from monkeys?”
14. Distinguish between:
a) Convergent and divergent evolution
b) Analgous and homologous structure.
15. Explain the meaning of each of the following mechanisms of evolution:
a) struggle for existence
b) Survival of the fittest.

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Part II: Answers of the questions

Chapter 1: Classification of livings

1. Binomial nomenclature is a two-term naming system used for classifying organisms and was also
introduced by Linnaeus. Each organism is given a two word Latin name. The first name is a generic
name which describes the genus to which an organism belongs followed by the specific name which is
the name of species to which an organism belongs.

2. A species is a group of organisms which have numerous detailed features in common and are able to
interbreed (sexual reproduction) and do not normally breed with other species.

3. He classified all livings known at that time into two major groups: plants and animals. Plants were
classified as herbs, shrubs, or trees depending on their size and structure. Animals were classified
according to where they lived on land, in the air, or in the water. Later observations convinced scientists
that Aristotle’s system did not work. They observed that some animals such as frogs live both on land and
in the water. Scientists also realized that Aristotle’s classification system did not show natural relationship
among organisms.

4. Linnaeus used an organism’s morphology, that is, its form and structure to categorize it.
5. The seven levels are called kingdom, phylum, class, order, family, genus and species.
6. Two reasons that show that species names are more precise than common names:
a) They are used worldwide.
b) Have the merit that everyone knows exactly which organism is being referred to.

7. The six kingdoms of life, one characteristic and an example for each.
KINGDOM One charactristic Example

Archaebacteria Prokaryotic cell, unicellular Methanogens

Eubacteria Prokaryotic cell, unicellular Bacillus subtilis, Escherichia coli
Protista Eukaryotic, unicellular or multicellular Paramecium, Amoeba
Fungi Eukaryotic, multicellular Molds, yeasts, mushrooms

Plantae Eukaryotic, multicellular Lemons, cypress, maize tree

Animalia Eukaryotic, multicellular Humans, worms

8.
a) Botany is the study of plants
b) Entomology: is the study of insects.
c) Ornithology: is the study of birds.
d) Cytology: is the study of the cell.
e) Histology: is the study of tissues.
f) Anatomy: is the study of internal biological structures of an organism.

9. The three domains of life are: domain archae, domain bacteria and the domain eukarya.

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 10. Because they are all composed of eukaryotic cells.

11. To classify organisms, modern taxonomists consider the phylogeny or evolutionary history of the
organism.

12.
a) Protoctista and Plantae
b) Protoctista, Fungi and Animalia
c)

Chapter 2: The kingdom plantae

1.

a) Phyllotaxis: is the arrangement of leaves on a plant stem

b) Anemogamy: pollination with the help of wind.

c) Zoochory: seed dispersal by animals

d) Inflorescence: The collective cluster of flowers on an axis.

2. In the life cycle of a fern, there is production of one kind of spores (homosporous) whereas the life cycle
of a seed plant involves the formation of two kinds of spores (heterosporous). Also in the life cycle of a
fern, the spores form the prothallus after germination while in the life cycle of a seed plant the microspores
produce the sperm that will fertilize the egg formed by the megaspores.
3. The gametophyte generation of a plant is responsible for the development of gametes. All cells of the
gametophyte including the gametes are haploid (n). The sporophyte generation is responsible for the
production of spores. All cells of the sporophyte are diploid (2n) and are produced by mitosis. The spores
are produced in the sporophyte plant body and are therefore haploid (n).
4. In conifers there is no double fertilization as in flowering plants.
5. When a ripe pollen grain lands to the stigma of its species, it germinates. The nucleus of its tube cell forms
a pollen tube that grows through the stigma and style toward the ovary. As the pollen tube grows, its
generative cell divides mitotically to form two haploid sperm. The pollen tube grows to an ovule within
the ovary and enters it through the micropyle. After the pollen tube penetrates the ovule’s embryo sac, the

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 sperm can reach the egg through the passageway that has been formed. One of the two sperm fuses with
with the egg cell forming a diploid zygote. The zygote eventually develops into an embryo. The second
sperm fuses with the two polar nuclei, producing a triploid nucleus. This nucleus develops into a tissue
called endosperm. The endosperm provides nourishment to the embryo. As you can see, two types of cell
fusion occur in the embryo sac; one that produces the zygote and the other that produces the endosperm.
This process which is called double fertilization is unique to angiosperms.
6. The flower and its main parts is shown below:

7. This event has an advantage of preventing the self pollination but favors the cross pollination.
8. Dispersal by birds eg: tomatoes
Dispersal by humans eg: lemons
Dispersal by water eg: water lily

9. Advantages of asexual reproduction

 It produces relatively more offsprings than sexual reproduction. This facilitates faster propagation of the
species.
 Large numbers of organisms mean that species may survive when conditions or the number of predators
change.
 Energy is not required to find a mate because it requires only one parent.
 It results in the maintenance of favorable characters because the offsprings are genetically identical.
 It does not depend on external agents like pollinators dispersal agents in plants and mates in animals,
because every species is self sufficient.
 It facilitates the establishment of polyploids particularly those with odd numbers of sets of chromosomes.

The advantages of sexual reproduction

 The biggest advantage of sexual reproduction is that it allows for diversity among the offspring. If all
organisms are not exactly alike, then they might have little variations that help them survive when the
environment changes. So variation is a survival mechanism.
 It produces relatively fewer offsprings than in asexual reproduction and it does not normally result in
overcrowding around the parent.

10. Characteristics of wind-pollinated flowers

 The pollen is light and smooth and is often produced in stamens with long filaments which swing
easily in the wind.
 The flowers are not brightly colored and the perianth is usually small.
 They do not secrete nectar.
 They produce large quantities of pollen grains, much of them never reach the stigmas.

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  The stigmas are usually large and feathery and the styles long, so that the stigmas project from
the flower and catch any pollen floating in the air.

11. Differences between monocots and dicots

Characteristics Monocotyledonous plants Dicotyledonous plants

Number of cotyledons in the One Two

seed
Floral parts (eg: petals, Arranged in three or multiple of Arranged in four or five or
sepals) three multiple of four or five
Venation Parallel vein Net vein
Root system Fibrous root system Tap root system

12. Gymnosperms do not produce flowers while angiosperms have flowers. Another difference is that the
seeds of gymnosperms are not protected by the fruit (naked seeds) while the seeds of angiosperms are
protected by the fruit.
13. The life cycle of a fern is shown below:

 A sporangium bursts to release haploid spores which may be dispersed by wind.

 A spore germinates to form a distinctively heart-shaped gametophyte called a prothallus. A prothallus
produces both archegonia and antheridia. Short multicellular rhizoids grow from the underside of the
prothallus.
 During sexual reproduction the sperm swim through a film of water on the body of the prothallus to reach
the archegonium where the egg is fertilized.
 After fertilization, the diploid zygote develops into the sporophyte.
 As the sporophyte matures, the prothallus disappears and roots grow out of the developing rhizome.
 When environmental conditions are appropriate, sori develop within each sporangium and the spores are
produced by meiosis.

14. In the life cycle of a fern the sporophyte generation is dominant while in the life cycle of mosses, it is the
gametophyte generation which is dominant.

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 In the life cycle of a fern the spores give the prothallus after germination while in that of mosses the spores
give male or female gametophytes.
In the life cycle of a fern the sporophyte generation is not dependent on the gametophyte while in the life
cycle of mosses the sporophyte generation is dependent on the gametophyte generation.

15. The structure of a mature ovule

Chapter 3: The kingdom fungi

1. Advantages of fungi
 Some fungi are eaten
 Some fungi are used in the production of antibiotics
 Some fungi are important in recycling of matter…

Disadvantages of fungi

 Some fungi cause diseases

 Some fungi are toxic
 Some fungi cause the spoilage of food…
2.
a) Lichen: The lichens represent symbiotic relationship between a fungus and a photosynthetic
partner (usually a cyanobacterium or green algae)
b) Mycorrhiza: A mycorrhiza is a symbiotic association between a fungus and plant roots.
c) Mycelium: is a mat of hyphae visible to the unaided eye.
3. Plants have cell walls made of cellulose while the cell walls of fungi are made of chitin.
Plants are autotrophic while fungi are heterotrophic.
Plants are multicellular while some fungi are unicellular, others multicellular.

4. Fungi compete with humans for nutrients because they cause the destruction of important food crops.

5. Cheese, beer and wine, breads,

6. Athlete’s foot is caused by Trichophyton species (ascomycete) or epidermophyton species

Vaginal yeast infection is caused by Candida species.

7.
 Lichens are common food for insects and slugs. In the arctic tundra, reindeer and caribou rely
on lichens during the winter, when no other food is available. Several species of lichens that
sprout up through the snow are called reindeer mosses.
 Lichens are used as living indicators of environmental problems because of their sensitivity to
atmospheric pollution. Despite their hardness in severe conditions, many lichens are damaged
by the chemicals found in polluted air and by acid rain produced from the combustion of coal,

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 oil, and gasoline, and other industrial processes. Comparisons of lichen damage burning from
industrialized and nonindustrialized areas provide an index of air pollution.
 Lichen antibiotics have been used to treat tuberculosis and some skin diseases.
8. The partners exchange minerals accumulated from the soil by the fungus to organic substances
synthesized by the plant.
9. Fungi secrete enzymes on the substrate and absorb the digested nutrients through their cell wall (they use
extracellular digestion).
10. The fact that fungi are saprophytic, that is they live on organic compounds that they absorb from dead
organisms in the environment.
11. Some fungi produce antibiotics that can inhibit the growth of microorganisms. The process has helped
because some microorganisms were prevented to grow on wounds.
12. Fungi are heterotrophs and decomposers (they break down dead beings) and they actively participate in
the recycling of organic material in ecosystems. Some fungi keep mutualist ecological interaction with
algae or cyanobacteria, forming lichen, and with plant roots, forming mycorrhizae.
13. The kingdom fungi is divided into three phyla: ascomycetes, basidiomycetes, and zygomycetes.
Mushrooms are basidiomycetes.

Chapter 4: The kingdom protista

1. The kingdom Protista includes algae, protozoa, slime molds and water molds.

2. Algae are autotrophic while protozoa are heterotrophic.

Algal cells have cell walls while protozoa cells have no cell walls.
Algae can be unicellular or multicellular while all protozoa are unicellular.
3. Algae are autotrophic as plants
Algal cells have cell walls made of cellulose as plants.
Algae differ from plants by the fact that they have no tissue differentiation (no true roots, stems or leaves).
4. Protozoa are mobile like animals; they have no cell walls and they are heterotrophic like animals.
5. Algae are classified into seven phyla, based on their colour, type of chlorophyll, form of food storage and
cell wall composition.
6. Diatoms are an abundant component of phytoplankton and are important producers in fresh water and
marine food webs. They are an essential source of nutrients for microscopic heterotrophs. In addition,
they release an abundant quantity of oxygen.
7. They are plantlike in that many have chlorophyll and are photosynthetic. They are animal like in that they
lack a cell wall and are highly motile.
8. Many algae have high nutritional value and are commercialized and consumed as human food, they are
very popular food in the oriental world. Jelly compounds are extracted from some algae, like glues and
pastes for industrial and commercial use. The agar-agar, used as a medium for biological culture in
laboratories and in medicines, and the substance known as carrageenin, a component of tooth pastes,
cosmetics, paint and hygienic products, are extracted from rhodophyte algae. Diatom algae deposited on
the bottom of the sea form diatomites, used in the production of filters, refractories, thermal isolation and
cement. Some algae are used as agricultural fertilizers.
9. A cyst is a dormant form characterized by a hardened, external covering in which metabolic activity has
ceased. Many species of protozoa form cysts in response to changes in the environment such as nutrient
deficiency, drought, decreased oxygen concentration or PH or temperature changes.
10. Conjugation is the exchange of genetic material between two paramecia. Because genetic material is
exchanged between the two original paramecia, the four offsprings paramecia are different from either
original paramecium.
11. When an infected mosquito bites a person, Plasmodium sporozoites enter the bloodstream and travel to
liver cells, where they divide repeatedly.
New spores called merozoites emerge and infect red blood cells, where they reproduce asexually. At
regular intervals, the merozoites burst out of the red blood cells and the release of toxins in the blood
cause fever, anemia and other symptoms of malaria. The merozoites infect other red blood cells and again
reproduce asexually. This asexual reproduction can happen many times over a long period of time.
Merozoites of some species remain in the liver and do not come out for months or years. Thus, an infected

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 person could take antimalaria drugs and cure the infection in the blood, only to become ill again when the
merozoites leave the liver cells.
Some of the merozoites in the blood develop into specialized cells called gametocytes. When a female
anopheles bites the infected person, it ingests these gametocytes. In the mosquito’s digestive system, the
sperm and eggs combine to form a zygote. The nucleus of the zygote divides repeatedly to form more
sporozoites. When the zygote bursts, the sporozoites migrate to the body cavity and salivary glands of the
mosquito. When the insect bites another person, the life cycle begins again.
12. When a sarcodine feeds, it surrounds the food with its pseudopodia. A portion of the cell membrane then
pinches together and surrounds the food in a food vacuole, in a process called endocytosis. Enzymes from
the cytoplasm then enter the vacuole and digest the food. Undigested food leaves the cell in a reverse
process called exocytosis.
13. The life cycle of Plasmodium is shown below:

14. The macronucleus is properly the cell nucleus; it has DNA and RNA and acts as the center of the cellular
control and regulation. The micronucleus has reproductive functions and it is related to the conjugation
process (sexual reproduction).

Chapter 5: Bacteria and viruses

1. Bacteria are prokaryotic and unicellular beings. Bacteria have simple organization, they present an external
cell wall, plasma membrane, circular DNA within the cytoplasm and ribosomes for protein synthesis.
Some bacteria are encapsulated, i.e., they have a polysaccharide capsule outside the cell wall.
2. Prokaryotic beings are classified into two big groups or kingdoms: archaebacteria and eubacteria.
Compared to eubacteria, archaebacteria have basic differences, like the chemical compositions of their
plasma membrane and cell wall and different enzymes related to DNA and RNA metabolism.

3. Bacteria are responsible for the decomposition process at the end of food chains and food webs; in this
process, they also liberate utile gases and nutrients for other living beings. Bacteria that live within the
digestive tube of ruminants and of some insects digest cellulose for these animals. Some bacteria also
participate in the nitrogen cycle, making fixation of nitrogen, nitrification and denitrification, almost
always in mutualist ecological interaction with plants. Bacteria present within living beings, for example,
some that live inside the bowels, compete with other pathogenic bacteria so controlling the population of
noxious agents. There are also bacteria that cause diseases and bacteria used in the production of medical
drugs.
4. Some human diseases caused by bacteria are tuberculosis, diphtheria, bacterial meningitis, gonorrhea,
syphilis, cholera, typhoid fever, tetanus and anthrax.
5. Bacteria are used by industry in various ways. There are vaccines made of attenuated pathogenic bacteria
or of antigens present in bacteria. One of the most ancient uses of bacteria is the fermentation of milk to

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 produce yogurt, cheese and curd (even before the knowledge of the existence of bacteria these
microorganisms were already used in the making of those products). Some methods of antibiotic
production involve bacteria. The recombinant DNA technology (genetic engineering) allows the
industrial production and commercialization of human proteins, like insulin for diabetics, synthesized by
mutant bacteria. Some bacteria can produce fuel, like methane gas.
6. Bacteria can be found in various environments throughout the planet. There are bacteria in the air, in fresh
water, on the surface, in the intermediate depth and on the bottom of the sea, in soils, in our skin and
practically in all terrestrial environments through which air circulates freely. Some bacteria can be found
in volcanic craters under extremely high temperatures.
7. The bacterial cell wall is made of peptidoglycans.
8. Plasmids are circular fragments of DNA that are accessories to the main bacterial DNA. Plasmids are
important for genetic engineering because genes from other organisms are inserted into them to produce
recombinant beings, for example, mutant bacteria. These bacteria are made, for example, to produce utile
proteins for humans on an industrial scale.
9. Gram-positive bacteria have a thicker layer of peptidoglycan in their cell wall than gram-negative bacteria
Gram-positive bacteria appear purple under the gram stain while gram-negative bacteria will appear pink.
10. Viruses are constituted of genetic material (DNA or RNA) covered by a protein capsule also known as a
capsid. Some viruses, like HIV, have in addition an external envelope derived from the plasma membrane
of the host cell from which it came.
11. All viruses are obligate intracellular parasites, i.e., they depend on the host cell to complete their life
cycle. A virus does not have its own metabolism.
12. There are DNA viruses (double strand or single strand DNA) and RNA viruses (double strand or single
strand RNA too). Viruses inoculate their DNA or RNA molecules into cells and these cells (by means of
transcription or reverse transcription and translation) synthesize proteins for the assembling of a new
virus. This synthesis is commanded by the viral DNA or RNA molecules.
13. A typical virus has proteins on its capsid that bind to the outer membrane of the host cell. In the place
where the virus adhered viral proteins act to break the cell membrane and then the virus injects its DNA
molecules into the host cell. Within the host cell the viral DNA is transcripted and thus messenger RNA
is produced. Viral mRNA then is translated and viral proteins are made. Viral polypeptides made within
the host cell are cut by enzymes called proteases and then copies of the virus are assembled with the newly
formed proteins. When the assemblage of new viruses is completed the cell membrane breaks and the
viruses are released to the outside. One sole infected cell can produce hundreds of viruses.
14. Retroviruses are viruses whose genetic material is RNA. HIV and the virus of SARS (severe acute
respiratory syndrome) are examples of retrovirus. These viruses inoculate their RNA into the host cell
and within the cell the viral RNA is reversely transcripted into DNA. DNA made from the viral RNA then
commands the synthesis of viral proteins for the assemblage of new viruses and the breaking of the host
cell to liberate them outside. The enzyme reverse transcriptase is the catalyst of the reverse transcription
of RNA into DNA. The enzyme is part of the virus and it is also inoculated into the host cell.
15. HIV is an RNA virus. In its core there are two strands of RNA and reverse transcriptase molecules. The
core is covered by a capsid, a layer of proteins. The capsid then is covered by an envelope having
glycoproteins and lipids. The glycoproteins of the HIV envelope are located on the outer surface of the
virus and they are responsible for the recognition of the cells to be infected (the HIV host cell is the CD4
lymphocyte) and for the adhesion of the virus to the cell membrane. (CD4 is a receptor glycoprotein of
the outer membrane of some lymphocytes).

16. Among diseases caused by virus are common cold, flu, mumps, variola (considered eradicated nowadays),
rubella, measles, AIDS, the viral hepatitis, human papillomatosis (HPV infection), rabies, yellow fever,
poliomyelitis (an almost eradicated disease in developed countries), hemorrhagic fever from Ebola virus,
SARS (severe acute respiratory syndrome).
17. During the lytic cycle, a virus (example a bacteriophage) invades a host cell, produces new viruses,
destroys the host cell, and releases newly formed viruses. Viruses that undergo the lytic cycle are called
virulent because they cause disease. The lytic cycle consists of five phases:
- The bacteriophage first attaches to susceptible bacterium by attaching its tail fibers to a receptor
site. Receptor sites are specific sites that viruses recognize and attach to on the host cell’s surface.
If the Bacteriophage doesn’t find a receptor site, it cannot infect the cell. This specificity is true
for many viruses.

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 - Next the bacteriophage releases an enzyme that weakens a spot in the cell wall of the host. Then
the phage presses its sheath against the cell and injects its DNA into the host cell through the
weak spot in the cell wall. The bacteriophage leaves its capsid outside.
- The virus then takes control of the host’s protein synthesizing mechanisms, transcribing mRNA
from the viral DNA. The resulting Bacteriophage DNA is translated by ribosomes and enzymes
that form Bacteriophage capsids. So the viral DNA is also replicated during this phase.
- The replicated viral genes are enclosed in the newly created virus capsids. The assembly of new
virus particles usually occurs in the cytoplasm, but it also may take place in a eukaryotic cell’s
nucleus.
- During the last phase of the lytic cycle, one of the enzymes that is produced by the Bacteriophage
genome causes the host cell to disintegrate, releasing new Bacteriophage. The cell disintegration
is called lysis. The enveloped viruses, the newly formed viruses move to the cell surface and
force their way through the cell membrane.

Chapter 6: KINGDOM ANIMALIA

1. Sponges have a porous body plan while cnidarians have no pores on their body.
The mouth of cnidarians is surrounded by tentacles while the sponges have no tentacles.
Sponges have intracellular digestion while cnidarians have extracellular digestion.
Cnidarians have one opening that acts as mouth ads anus whereas in sponges, the food enters by the pores
and wastes leave by the osculum.

2. CLASS AGNATHA ex: lampreys, hagfishes

CLASS CHONDRICHTHYES ex: sharks, rays, skates
CLASS OSTEICHTHYES or BONY FISHES: most familiar fishes such as salmon, bass…

3. Classification of organisms into classes and phyla

Organisms Class Phylum

Mouse Mammalia Chordata

Bee Insecta Arthropoda

Frog Amphibia Chordata

Snake Reptilia Chordata

Snail Gastropoda Mollusca

Earthworm Oligochaeta Annelida

Hydra Hydroids Cnidaria

4. The Latin name for a house cat is Felis domesticus. Using this information and your knowledge of
classification, fill in the gaps in the table below.

Kingdom Animalia

Phylum Chordata

Class Mammalia

Order Carnivora

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 Family Canidae

Genus Canis

Species Domesticus

5. All chordates have a notochord, as well as a dorsal nerve cord, pharyngeal pouches and a post anal tail.
6. Lancelet, tunicate.
7.
a) The dichotomous key

b) The animals that are triploblastic coelomate are the specimen A, D and E.

8. Complete the table below about the classification of livings:

Livings Class Phylum Kingdom

Goat Mammalia Chordata Animalia

Squid Cephalopoda Mollusca Animalia

Planarian Turbellaria Flatworm Animalia

Cockroach Insecta Arthropoda Animalia

Paramecium - Ciliophora Protista

Saccharomyces - Zygomycota Fungi

cerevisiae
Escherchia coli - - Eubacteria

9. Protection of internal organs.

The coelom also provides a cavity in which organs can grow, develop and function independently of other
organs.
The coelom performs an additional specialized function in annelids. Here it acts as a hydrostatic skeleton,
in other words a fluid skeleton
10. Flatworms are acoelomate animals while annelids are coelomate animals.
The digestive system of flatworms when present is incomplete while annelids have a complete digestive
system.
Flatworms have no circulatory system while annelids have a closed circulatory system.

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 11. Flatworms are acoelomate animals while roundworms are pseudocoelomate animals.
Roundworms have a true alimentary canal with a mouth and anus while for flatworms, when present the
digestive system is incomplete.
12. The exoskeleton of insects prevents the water loss and adapts the insect to live in many areas. It also
protects them against predators. The disadvantage is that it is heavy so big insects cannot fly for a long
time. Another disadvantage is that it doesn’t allow growth so it must be shed periodically during molting.
During this time, the animal is extremely vulnerable to predators and in the case of terrestrial arthropods,
susceptible to dessication. For these reasons, arthropods usually remain in hiding from the time they begin
to molt until their new exoskeleton has hardened.

13. The subclass monotremes, the subclass marsupials and the subclass of placental mammals.
14. The order monotremata.
15.
i)
Organisms Phylum / Division Kingdom

Lobster Arthropoda Animalia

Housefly (Musca domestica) Arthropoda Animalia

Zea mays (maize) Magnoliophyta or angiosperms Plantae

Bread mold (Rhizopus) Zygomycota Fungi

Tilapia zillii Chordata Animalia

Frog (Rana spp.) Chordata Animalia

Zebra Chordata Animalia

Tilapia variabilis Chordata Animalia

Bat Chordata Animalia

Eagle Chordata Animalia

ii) Tilapia zillii and Tilapia variabilis. Because they belong to the same genus.
iii) It represents the species of maize.

16. Their mouths are circular, without jaws, and equipped with a pistonlike tongue that creates suction when
the mouth is placed against an object and the tongue is drawn back. The inner margin of the mouth and
the edges of the tongue are equipped with numerous small, horny teeth with which the lamprey pierces
the flesh of fishes.
17. Cetaceans (whales, dolphins) and sirenians (dugongs, manatees) are aquatic mammals. Chiropterans
(bats) are flying mammals.
18. Placental mammals reproduce sexually, they have internal fertilization and they are viviparous, i.e., their
embryo develops within the mother’s body and from her it gets the nutrients through the placenta.

19. For set A the odd one is the earthworm. It belongs to the phylum ANNELIDA. For set B, it is the tapeworm
which belongs to the phylum FLATWORMS. For the set c it is the sea urchin which belongs to the phylum
ECHINODERMATA and for set d it is the starfish which also belongs to the phylum
ECHINODERMATA.
20.
a) Parasite: a plant or animal which lives on or inside another organism, the host, and derives its
nourishment and other needs from it.

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 b)
I. Tapeworm
II. Leech
III. Flea or mosquito or bed bug or scabies mite.
c) They cannot live on their own.
21.
a)
i. Ferns are flowerless plants; ferns are vascular plants; their spores are produced on the lower
side of their leaves.
ii. Division magnoliophyta or anthophyta or angiosperms.
b)
i. Hydra
ii. Snail
c) The kingdom fungi and the kingdom protista.
d)
i. To regulate the density of the fish in water as the fish swims to different depths.
ii. To reduce the resistance to the flow of air during flight.
iii. To feed and to move.
iv. To catch the prey.
e) In external fertilization the eggs are fertilized outside the body while in internal fertilization the eggs
are fertilized inside the body of the body.
f) They all have an exoskeleton made of chitin, a segmented body and jointed appendages.
g) The spider has four pairs of legs whereas the wasp has three pairs of legs; the spider has no antennae
while they are present on the wasp head.

Chapter 7: CYTOLOGY

1. Cells can be classified as eukaryotic or prokaryotic. Prokaryotic cell is that without a delimited nucleus.
Eukaryotic cells are those with nucleus delimited by membrane.
2. The main constituents of the plasma membrane are phospholipids, proteins and carbohydrates. The
phospholipds, amphipathic molecules, are regularly organized in the membrane according to their
polarity: two layers of phospholipids form the lipid bilayer with the polar part of the phospholipids
pointing to the exterior of the layer and the non-polar phospholipid chains in the interior. Proteins can be
found embedded in the lipid bilayer and there are also some carbohydrates bound to proteins and to
phospholipids in the outer face of the membrane.
3. Plasma membrane and cell wall are not the same thing. Plasma membrane, also called cell membrane, is
the outer membrane common to all living cells and it is made of a phospholipid bilayer, embedded proteins
and some appended carbohydrates. Because cell membranes are fragile, in some types of cells there are
even outer structures that support and protect the membrane, like the cellulose wall of plant cells and the
chitin wall of some fungi cells. Most bacteria also present an outer cell wall made of peptidoglycans and
other organic substances.
4. In bacteria the cell wall is made of peptidoglycans; among protists algae have cell walls made of cellulose;
in fungi, the cell wall is made of chitin (the same substance that makes the exoskeleton of arthropods); in
plants, the cell wall is made of cellulose too.
5. Lipid membranes do not form only the outer cover of cells. Cell organelles, such as the Golgi complex,
mitochondria, chloroplasts, lysosomes, the endoplasmic reticula and the nucleus, are delimited by
membranes too.
6. Nucleolus is a region within the nucleus made of ribosomal RNA (rRNA) and proteins. It is not delimited
by membrane.
7. Ribosomes can be found free in the cytoplasm, adhered to the outer side of the nuclear membrane or
associated to the endoplasmic reticulum membrane defining the rough endoplasmic reticulum. Ribosomes
are the structures where protein synthesis takes place.
8. Phospholipids permit lipid-soluble materials to easily enter or leave the cell by diffusion through the cell
membrane. The presence of cholesterol decreases the fluidity of the membrane, thus making it more
stable. The proteins have several functions: Some form channels or pores to permit passage of materials
such as water or ions; others are carrier enzymes or transporters that also help substances enter the cell.

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 Still other proteins are antigens, markers that identify the cells of an individual as “self.” Yet another
group of proteins serves as receptor sites for hormones.
9. Passive transport is the movement of substances across membranes in favor of their concentration
gradient, i.e., from a more concentrated region to a less concentrated region. Active transport, on the other
hand, is the transport of substances across membranes against their concentration gradient, from a less
concentrated to a more concentrated region. In passive transport, because it is spontaneous, there is no
energy spent; the active transport however requires energy (work) to occur. Active transport works to
maintain or increase the concentration gradient of a substance between two regions while passive transport
acts in a manner to reduce the concentration gradient.
10. The three main types of passive transport are simple diffusion, osmosis and facilitated diffusion.
11. Facilitated diffusion can be confused with active transport because in both processes there is participation
of membrane proteins.

In active transport however the transported substance moves against its concentration gradient and with
energy spent. Facilitated diffusion is a passive transport in favor of the concentration gradient and it does
not require energy.

12. The rough endoplasmic reticulum has in its outer membrane numerous ribosomes, structures where
translation of messenger RNA and protein synthesis occur. These proteins are stored in the rough
endoplasmic reticulum and later they go to the Golgi apparatus. Within the Golgi apparatus proteins are
chemically transformed and when ready they are put inside vesicles that detach from the organelle. These
vesicles fuse with the plasma membrane (exocytosis) in the right place and its content is liberated outside
the cell.

13. The remodelation of the osseous tissue, the function of acrosomes in sperm cells and the elimination of
the tadpole tail are examples of biological processes in which lysosomic enzymes are key factors.

The bone is a tissue made of osteoblast-containing matrix (osteoblasts are the secretory cells of the
osseous matrix), osteocytes (mature bone cells) and osteoclasts (the remodeling cells). Osteoclasts are
responsible for the continual renovation of the osseous tissue since their lysosomic enzymes digest the
osseous matrix.

The sperm acrosome, for carrying digestive enzymes within, is responsible for the perfuration of the egg
cell membrane in the fertilization process. The acrosome, located in the anterior end of the sperm cell, is
a specialized region of the Golgi apparatus that accumulates a great amount of digestive enzymes.

In tadpoles the tail regresses while the organism develops into an adult frog. This tissue destruction is a
digestion of the tail's own cells and extracellular materials and it is made by lysosomes and their enzymes.
The complete digestion of a cell by its own mechanisms is called autolysis, a type of apoptosis (cell
suicide).

14. Chromosomes contain genes (genetic information in the form of nucleotide sequences) that command the
protein synthesis thus regulating and controlling the activities of the cell. In the nucleus of somatic cells
of diploid beings every chromosome has its correspondent homologous chromosome, both containing
alleles of the same genes related to same functions. This occurs because one chromosome of one pair
comes from the father and the other comes from the mother of the individual. The chromosomes that form
a pair with alleles of the same genes are called homologous chromosomes. In humans, there are 22 pairs
of homologous chromosomes plus the pair of sex chromosomes (the sex chromosomes are partially
homologous).

The only human cells that do not have homologous chromosomes are the gametes since during meiosis
the homologous chromosomes are separated.

15. The human haploid cell is the gamete (egg cell and sperm cell). The human gamete has 22 autosomes and
1 allosome (sex chromosome), i.e., 23 chromosomes. The diploid cell is the somatic cell and it has 44

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 autosomes and 2 allosomes, i.e., 46 chromosomes. Gametes have one sex chromosome and somatic cells
have two sex chromosomes.
16.

Organelle Function

Endoplasmic • Passageway for transport of materials within the cell

reticulum (ER) • Synthesis of lipids

Ribosomes • Site of protein synthesis

Golgi apparatus • Synthesis of carbohydrates

• Packaging of materials for secretion from the cell

Mitochondria • Site of aerobic cell respiration—ATP production

Lysosomes • Contain enzymes to digest ingested material or damaged tissue

17. Osmosis is the movement of water from a medium of higher water potential to a medium of lower water
potential through a semi permeable membrane. This process is important in the absorption of water in the
small intestines and in the reabsorption of water in the kidneys.
18.

19. A is the granum; B is the stroma; C is the outer membrane, D is the inner membrane, E is the intergranum
and F is the thylakoid.
20. Give the functions of the following:
a. Parenchyma cell: storage and photosynthesis
b. Companion cell: help in the transport of food
c. Root cap: protect the apical meristems of the root as it grows downward.
d. Meristematic tissue: growth of the plant.
e. Ground tissue: storage of food

21.

a) It is a plant cell. Because it has a cell wall, a big vacuole and chloroplasts.

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 b) A is the vacuole; B is the cell wall; C is the chloroplast, D is the cell membrane, E are the
plasmodesmata; F is the Golgi apparatus; G is the smooth endoplasmic reticulum; H are the
ribosomes, rough endoplasmic reticulum; I is the rough endoplasmic reticulum, J is the nucleus; K is
the mitochondrion and L is the cytoskeleton.
c) The function of C is photosynthesis; the function of D is the exchange of substances between the
inside of the cell and the outside, the function of J is the control of all cellular activities.

22. Solution A has higher water potential than solution B. Water will move from solution A to solution B.
23.

i) A is a carbohydrate; B is a protein; C is a polar head of the phospholipid and D is the cholesterol.

ii) Molecules C are so oriented because the inside of the cell contains water; so it is the polar part that
can face water which is also polar. The non polar tails are hydrophobic, cannot be in contact with
water which is hydrophilic. Non polar tails face inwards and polar heads point outwards forming the
lipid bilayer.
iii) The molecule A can act in holding two adjacent cells together; recognition; sites where viruses bind
to enter their host cells; receptor for chemical messengers...
The molecule B can act as channel proteins that allow facilitated diffusion; carrier proteins for active
transport of molecules in/out of the cell; receptor molecules for hormones....
The molecule D regulates membrane fluidity; mechanical stability; reduces leakage of polar ions by
diffusion...
24.
a) A: Nucleus B: Endoplasmic reticulum C: vesicle D: Golgi apparatus
b) The endoplasmic reticulum (rough) contains ribosomes that make the proteins. Those proteins
are packaged into the vesicles to the Golgi apparatus for their maturation. They can be packaged
again in vesicles to be sent to other destinations.
c) Exocytosis
d) Nucleus

25.

a) Nucleus
b) Plasma membrane
c) Organelle
d) Ribosomes
e) DNA
f) Cell
g) Cytoplasm

26.

Active transport Passive transport

against a concentration gradient Down a concentration gradient

Energy required in the process Energy not required
Substances moved by the help of carrier proteins. Substances move on their own or with the help of
carrier proteins in facilitated diffusion
27.
a)
I. Surface area; difference in concentration
II. Thickness of membrane
b)
I. It has a large surface area for efficient gas exchange

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 II. The lungs have a large surface area due to the numerous alveoli and those alveoli have a
very thin membrane.

28.

a) Some organelles are surrounded by one or two layers of unit membrane and are therefore referred to
as membranous organelles or membrane-bound organelles. These are the nucleus, mitochondria,
lysosomes, peroxisomes, endoplasmic reticulum and Golgi complex. Organelles that are not
surrounded by membranes include the ribosomes and centrioles. They are called non-membrane
bound organelles.
b) Mitochondria, nucleus and chloroplasts
c) Golgi apparatus, vacuole, lysosomes, endoplasmic reticulum
d) Ribosomes, centrioles, microtubules

29. The fluid mosaic model describes the structure of the plasma membrane.
30. Cytosol is the jelly-like substance that is found between the organelles in the cell. Cytoplasm includes
the cytosol and the organelles.
31. Plastids such as chloroplasts are the locations of photosynthesis, and leucoplasts store nutrients such as
starch.
32. The energy needs of the muscle cells have increased, so the number of mitochondria will increase to
supply the extra energy (ATP) to the cell.
33. Osmosis is the passage of water molecules across a semipermiable membrane. The water molecules
move down the concentration gradient, from an area of high concentration to an area of lower
concentration. The water molecules can move into or out of a cell, depending on the concentration of
the solute. Diffusion refers to the general movement of any molecule down a concentration gradient of
that particular molecule. Osmosis refers only to the diffusion of water molecules.
34. No, vesicles are not involved in passive transport because vesicle transport uses up energy. Therefore,
vesicles are involved in active transport.
35.

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 36.
Feature Cell wall Cell membrane

Is the thickness normally μm nm

measured in nm or µm?
Location surround some cells / not animal cells / surround all cells / may be found
only outside / surrounding cells inside cells

Chemical composition contains cellulose in plants, phospholipids, protein,

peptidoglycans / murein in prokaryotes,
(chitin in fungi) / contains a strengthening (sometimes) cholesterol
material / contains a polysaccharide

Permeability freely permeable Partially permeable

Function Mechanical strength Selective barrier

Fluid or rigid rigid fluid

37.
a) 1 mark for each accurately measured ‘observed size’ (to within ±2 mm) and 1 mark for each accurately
calculated ‘actual size’; 1 mark for applying the formula; 1 mark for measuring in mm and converting
mm to μm for each calculation; 1 mark for rounding up actual size to no more than one decimal place.
b) mitochondria will appear circular if they are cut, in transverse section / across (the long axis);
c)
i. A protein made on the ribosome is moving into the rough ER; B rough ER buds off small
vesicles; vesicles fuse to form the Golgi body; (therefore) protein moves into Golgi body; protein
may be modified / processed inside Golgi body; C Golgi body buds off Golgi vesicles; D Golgi
vesicles travel to cell surface membrane; Golgi vesicle(s) fuses with cell surface membrane;
protein / enzyme leaves cell; exocytosis / secretion.
ii. Ribosome / messenger RNA.
iii. Nuclear pore.
iv. ATP.

Chapter 8: The protein synthesis and cell divisions

1.

TYPES OF RNA FUNCTION

Messenger RNA (mRNA) Is built on a strand of DNA in the nucleus and

transcribes the nucleotide code; moves to cytoplasm and
attaches to a ribosome.

Ribosomal RNA (rRNA) With protein makes up the ribososomes, the sites of
protein synthesis in the cytoplasm; involved in the
process of translating the genetic message into a protein.

Transfer RNA (tRNA) Works with other forms of RNA to translate the genetic
code into protein; each molecule of tRNA carries an
amino acid that can be used to build a protein at the
ribosome.

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 2. 46 chromosomes. Chromosomes are made of DNA bound to proteins called histones.
3.

a) Anaphase
b) Prophase
c) Telophase
d) Metaphase
e) Prophase
f) Telophase

4.

Stage Events

Prophase  The chromosomes coil up and become visible as short rods. Each
chromosome is really two chromatids (original DNA plus its copy) still
attached at a region called the centromere.
 The nuclear membrane disappears.
 The centrioles move toward opposite poles of the cell and organize the
spindle fibers, which extend across the equator of the cell.
Metaphase  The pairs of chromatids line up along the equator of the cell. The centromere
of each pair is attached to a spindle fiber.
 The centromeres now divide.
Anaphase  Each chromatid is now considered a separate chromosome; there are two
complete and separate sets.
 The spindle fibers contract and pull the chromosomes, one set toward each
pole of the cell.
Telophase  The sets of chromosomes reach the poles of the cell and become indistinct as
their DNA uncoils to form chromatin.
 A nuclear membrane re-forms around each set of chromosomes.
Cytokinesis  The cytoplasm divides; new cell membrane is formed.

5. Advantages of mitosis

 Genetic stability: Mitosis produces two nuclei which have the same number of chromosomes as the
parent cell. Since these chromosomes were derived from parental chromosomes by the exact replication
of their DNA, they will carry the same hereditary information in their genes. Daughter cells are genetically
identical to the parent cell and no variation in genetic information can therefore be introduced during
mitosis. This results in genetic stability within populations of cells derived from the same parental cells.
 Growth: The number of cells within an organism increases and this is the basis of growth in multicellular
organisms.
 Cell replacement: Replacement of cells and tissues also involves mitosis. Cells are constantly dying and
being replaced, an obvious example being in the skin.
 Regeneration: Some animals are able to regenerate whole parts of the body, such as legs in crustacean
and arms in starfish. Production of the new cells involves mitosis.
 Asexual reproduction: Mitosis is the basis of asexual reproduction, the production of new individuals
of a species by one parent organism. Many species undergo asexual reproduction.

Advantages of meiosis

 Sexual reproduction: Meiosis occurs in all organisms carrying out sexual reproduction. During
fertilization, the nuclei of the two gamete cells fuse. Each cell has one set of chromosomes (is haploid,
n). The product of fusion is a zygote which has two sets of chromosomes (the diploid condition, 2n). If

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 meiosis did not occur, the fusion off gametes would result in a doubling of the chromosomes for each
sexually reproduced generation.
 Genetic variation: Meiosis also provides opportunities for new combinations of genes to occur in the
gametes. This leads to genetic variation in the offspring produced by fusion of the gametes. Meiosis does
this in two ways, namely independent assortment of chromosomes and crossing over in meiosis I.
6.
a) A is the molecule of DNA; B is the growing polypeptide; C is a tRNA and D is mRNA.
b) Transcription
c) Translation
d) One is the anticodon which attaches on codons of messenger RNA and another for the attachment of
amino acids.
7.
Mitosis Meiosis

Number of divisions One Two

Number of cells formed One cell produces two cells One cell produces four cells

Chromosome number of the 46 chromosomes in humans 23 chromosomes in humans

cells formed

8. The triplet code: three bases (a codon) is the code for one amino acid. The molecule that copies the triplet
code of DNA is mRNA.
The organelle that is the site of protein synthesis is the ribosome.
9.
a) It represents a DNA molecule.
b) A is the nitrogen base, B is the sugar, C is the phosphate group and D is the hydrogen bond.
10.
a) 46
b) 92
c) 92
d) 92 (46 at the end of telophase)

11. In eukaryotes, mRNA travels out of the nucleus into the cell cytoplasm to attach to a ribosome. In both
eukaryotes and prokaryotes, the ribosome acts like a workbench and clamp that holds the mRNA strand
and coordinates the activity of enzymes and other molecules essential to translation.

Another form of RNA called transfer RNA (tRNA) is found in the cytoplasm of the cell. There are many
different types of tRNA, and each type binds with one of the 20 amino acids used in protein formation.
One end of a tRNA binds with a specific amino acid. The other end carries three bases, known as an
anticodon. The tRNA with an amino acid attached travels to the ribosome where the mRNA is stationed.
The anticodon of the tRNA undergoes complementary base pairing with a series of three bases on the
mRNA, known as the codon. The mRNA codon codes for the type of amino acid carried by the tRNA.

A second tRNA bonds with the next codon on the mRNA. The resident tRNA transfers its amino acid to
the amino acid of the incoming tRNA and then leaves the ribosome. This process continues repeatedly,
with new tRNA receiving the growing chain of amino acids, known as a polypeptide chain, from a resident
tRNA. The ribosome moves the mRNA strand one codon at a time, making new codons available to bind
with tRNAs. The process ends when the entire sequence of mRNA has been translated. The polypeptide
chain falls away from the ribosome as a newly formed protein, ready to go to work in the cell.

12. In mitosis and meiosis II, there is separation of sister chromatids. The difference is that in mitosis the
sister chromatids are identical while in meiosis the sister chromatids are different.
13.
A: Telophase of mitosis
B: Anaphase of meiosis I
C: Metaphase of meiosis II

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 D: Anaphase of mitosis

14. Differences between DNA and RNA

RNA DNA

Strands Single stranded Double stranded

Sugar Ribose Deoxyribose
Size Relatively small Big
Location Moves to cytoplasm Stays in the nucleus
Types 3 types: mRNA, tRNA and One type
rRNA
Specific base Contains uracil Contains Thymine

15.

a) DNA replication is the process in which a cell’s entire DNA is copied, or replicated.
b) This process occurs during the Synthesis (S) phase of the eukaryotic cell cycle.
c) In the semi-conservative model, the two parental strands separate and each makes a copy of
itself. After one round of replication, the two daughter molecules, each comprises one old and
one new strand.
d) In DNA replication 2 daughter DNA are formed whereas in transcription mRNA is formed.
e) A given amino acid may be coded for by more than one codon.
16.
a) It is a sequence of anticodons.
b) UGUCUCGGUGAAGGUUUCUGA
c) 6 amino acids
d) Cys-Leu-Gly-Glu-Gly-Phe

17. Generally in vertebrates mitosis is more frequent in tissues that require intense renewing due to their
functions, like epithelial tissues and the bone marrow. In plants the meristem tissue has numerous cells
undergoing mitosis.

Mitosis take place with low frequency in tissues of slow renovation, like the bones in adults and the
connective tissues.

In some adult tissues mitosis is almost absent, like the nervous tissue and the striated muscle tissue
(skeletal and cardiac). The nervous tissue develops from stimulus by development of new electrical
networks between cells and the striated muscle tissue grows by cellular hypertrophy.
18. Cell division properly occurs during the mitotic phase of the cell cycle. During interphase processes that
are a preparation to cell division take place, like the duplication of DNA and centrioles. Interphase is the
preceding phase and the mitotic is the following phase.
19. Interphase is the preceding phase to the mitotic division. It is divided into three periods, G1, S and G2
(the letter G comes from “gap”, meaning interval or breach, and the letter S comes from “synthesis”,
indicating the period in which DNA replicates). In fact, “gap” is not totally appropriate for the periods
immediately before and after the DNA synthesis. The idea of “growth” would be more adequate since in
those periods (G1 and G2) the cell is growing to divide later in mitosis.
20. In the anaphase of mitosis the identical chromatids separate and complete pairs of homologous
chromosomes continue to exist in each daughter cell. The separation of the homologous chromosomes
occurs in the anaphase of the cell division by meiosis.
21. The first period of the first phase (interphase) of the cell cycle is the G1, followed by S and G2 and then
by the mitotic phase. In G1 the ploidy (the quantity of DNA molecules in the cell) can be represented by
the formula 2n (n is the number of DNA molecules in a gamete cell of a given species). In S DNA
duplicates and the quantity of genetic material increases from 2n to 4n. In G2 that quantity is constant:
4n. After the mitotic phase the quantity of genetic material decreases to 2n in each daughter cell.

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 22. Crossing over is the eventual exchange of chromosomal fragments between homologous chromosomes.
The phenomenon occurs in prophase I when homologous chromosomes are paired. Crossing over is of
great importance for evolution and biodiversity since it provides recombination of alleles (of different
genes) linked in the same chromosome during cell divison by meiosis.

23. The separation of homologous chromosomes in meiosis I has two main functions: to reduce to a half the
total number of chromosomes, generating haploid daughter cells at the end of the process, and to make
possible genetic recombination since the separation is aleatory, i.e., each pair of daughter cells can be
different from the other pair relating chromosomal combination from paternal and maternal origins. (And
if crossing over is considered each of the four resulting cells can be different from the others.)

The separation of identical chromatids in meiosis II has the same function it has in mitosis: to separate
the chromosomes already duplicated to the daughter cells.
24.
a) The term antiparallel is used because the strands run in opposite direction to each other. The sugars
are pointing in opposite directions.
b) TAATCCGATA
c) 20% A, 30% C, 30% G
d) When the copying error occurs during mitosis for growth/replacement of cells, cancers may occur.
When a mutation happens when gametes are formed, any genetic disease involving point mutation
can occur (e.g. haemophilia, phenylketonuria).
25. The three components of a nucleotide are: a nitrogen base, a sugar and a phosphate group. The component
which varies from one nucleotide to another is the nitrogen base.
26. 900.
27. Splicing is the process by which introns are removed from pre-mRNA.
28. An exon is the region of a gene that contains the code for producing a protein. A gene's exons are often
separated by long regions of DNA that have no identified function. These long regions are called introns,
and they must be removed prior to translation.
29. The Genetic Code is the code in which the language of nucleotides is used to create the language of amino
acids. The Genetic Code is how A, C, G, and U can carry information for 20 different amino acids. Codons
are the three bases of RNA that code for one amino acid. In the Genetic Code, there are 64 different
codons, including 1 start codon and 3 stop codons. The others code for amino acids.
30. A reading frame is the groups of three bases in which the mRNA is read. Interrupting the reading frame
may have severe consequences on the resulting protein.
31. The universality of the Genetic Code means that the same code is utilized by the simplest prokaryotic
organism and the most complex eukaryotic organisms.
32. (a) – ( v); (b) – (iv); (c) – (iii); (d) – (i); (e) – (vi); (f) – (ii).
33.
(a)
i) DNA contains a triplet code, three bases (triplet) in DNA code for one amino acid.
ii) The code is universal, the same codes for the same amino acids in all organisms.
iii) The code is degenerate. There are 64 triplet codes coding for 20 amino acids.
iv) The code is non-overlapping.
(b)
i) 45 hydrogen bonds.
ii) AUGCAUGUAAGCGGUCCU
iii) AUG
iv) Met-His-Val-Ser-Gly-Pro.
34. The helix would bulge outward wherever two purines were paired and cave inward wherever two
pyrimidines were paired, so the diameter of DNA would not be uniform.
35.
a) 92 chromatids
b) 92 DNA molecules (each chromatid contains one DNA molecule)
c) 92 kinetochores
d) 46 chromatids
e) 92 chromatids
36.
a) 64

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 b) For ‘punctuation marks’ – that is, for starting or stopping the synthesis of a polypeptide chain.
Also, some amino acids could be coded for by two or three different base triplets.
c) A two-letter code could only code for 16 amino acids.
37.
Transcription Translation

Site in cell where process occurs nucleus ribosome (in cytoplasm)

Molecule used as a template in process DNA (in cytoplasm) Molecule used as a template
in the process is mRNA

Molecule produced by the process mRNA polypeptide / protein

Component molecule (monomers) used in RNA Amino acids

process
nucleotides
One other molecule that is essential for the RNA polymerase tRNAs / enzymes / ribosomal RNA (rRNA) /
process to occur ribosomal protein

38.
a) X is mRNA; Y is the ribosome; Z is the (poly)peptide chain / chain of amino acids.
b) From left to right; increasing length of polypeptide chain.
39.
a) The DNA in the spleen and thymus of the same organism is the same; the same genes are present
in both organs;
b) The DNA in different species is different; different genes are present;
c) DNA has double helix / is double stranded; the numbers of A and T, and of C and G, are similar
because A pairs with T and C pairs with G.
d) The DNA is single stranded; no base pairing occurs.
40.
a) One long, one short and one hooked chromosome present inside a circle (nucleus).
b) Meiosis
c) Six chromatids about half-way between equator and each pole (12 chromatids in all); two long, two short,
two hooked in each direction; centromere leading for each chromatid.
d) In diagram 2, shading represent sets of chromosomes / one type of shading represents set of chromosomes
from mother, other type of shading represents set of chromosomes from father; in diagram 3, shading
represent homologous pairs of chromosomes / differently numbered chromosomes.

Chapter 9: Plant histology

1. The growth tissues of the plants are the meristems. Meristems are the tissues that produce the plant growth
giving birth to all other tissues; they are formed of undifferentiated cells having intense cell division rate.
Meristems classify as primary meristems and as secondary meristems.

Primary meristems or apical meristems are found in the apex of the stem, in the lateral buds of the stem,
in the basis and tips of the shoots and within the root cap. Primary meristems are responsible for the
primary growth (lengthening) of the plant.

Secondary meristems or lateral meristems are those that make the plant grow in thickness (secondary
growth) and they are formed by tissues that thicken the stem: vascular cambium and cork cambium.
2. Apical meristems are those primary meristems found in the apex of the stem and in the tips of shoots and
roots. The apical meristems are responsible for the primary growth of the plants.
3. Meristematic cells have very thin cell walls, small vacuoles, a well-centralized nucleus and they are
constantly undergoing mitosis. Meristematic cells need a high mitotic rate because they are responsible
for the plant growth.

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 4. The plant supporting tissues are the collenchyma and the sclerenchyma. The collenchyma is made of
living and elongated cells that accumulate cellulose and pectin in some regions of the cell wall making
them unequally thick and thus providing flexibility. The sclerenchyma is made mostly of dead cells killed
by lignin deposition (lignin is an impermeable biopolymer) forming elongated, rigid and impermeable
fibers. The sclerenchyma is a plant tissue widely used in the textile industry.
5. The main photosynthetic tissue is the photosynthetic parenchyma (also known as chlorenchyma, do not
confuse with collenchyma) often located between the superior and the inferior epidermis of the leaves.
6. The vascular tissues of the plants are the xylem and the phloem. Xylem is the plant tissue that forms the
vessels that conduct water and mineral salts absorbed from the soil to the plant cells. Phloem is the plant
tissue that forms the vessels that conduct dissolved sugar from the leaves (where they are produced by
photosynthesis) to other plant cells.
7. The main cells of the xylem are the tracheids and the vessel elements (these only in angiosperms). The
tracheids and the vessel elements are dead cells that have lost their cytoplasm and only their cell wall
impregnated with lignin (an impermeable biopolymer) remained. The tracheids form tubes that
communicate with neighboring tubes through pores; the vessel elements do not present pores but instead
they communicate with the successive vessel element through perforations in their extremities.
8. The main cells that form the phloem are the sieve elements and the companion cells. The sieve elements
form the vessel walls; they are living enucleated cells positioned in series forming the sieve tubes.
Between successive vessel elements there are communicating pores. The companion cells are located
outside and alongside the sieve tubes and they help in the absorption of the material to be transported.
9. Vascular cambium is the secondary meristematic tissue that in roots and in the stem forms the vascular
tissues (xylem and phloem) of the plant. Usually the outer side of the vascular cambium produces a layer
of phloem and the inner (more central) side of the tissue produces a layer of xylem.
10. Leaf veins are made of vascular tissues. They are constituted by xylem and phloem that respectively
conduct water and mineral nutrients (xylem) and sugar (phloem).
11. The covering tissues, or dermal tissues, of the plants are the epidermis (that covers the leaves and the
young stems and shoots) and the periderm (a tissue that substitutes the epidermis in stems, shoots and
roots). The periderm is made of phelloderm, phellogen and suber (cork).
12. The root hairs are external elongated projections of the root epidermis. Their role is to increase the
absorption of water by the root.
13. The roots have a central portion called medulla made of vascular tissue (inner xylem and outer phloem).
The medulla is surrounded by the medullary parenchyma and delimited by pericycle, a meristem that
originates the secondary roots (ramifications). Externally to the medulla lies the cortical portion formed
of endodermis (that surrounds the pericycle) and cortical parenchyma. The covering of the roots is
epidermis (with root hairs) later substituted by suberized (corky) periderm.
14. The root cap is a protective structure located in the tip of the growing root. It protects the meristematic
tissue of the root forming a cap that surrounds the tip. The cover is necessary since during the growth of
the root the meristem otherwise would be injured by the friction with the soil.
15. Tissues that monocots and dicots have in common are apical meristems. The meristematic tissue which
is present ony in dicots is the vascular cambium.
16.
a) Dicot root
b) A is the endodermis; B is the pericycle; C is cylem; D is phloem and E is the cortex.
c) D is involved in the transport of food. E has a function in the storage of substances.
17.
a) It represents the stoma.
b) A is the epidermal cell; B is the inner thick wall of the guard cell; C is the stoma; D is the guard cell;
E is the chloroplast.
c) It has chloroplasts; it has also a kidney shape; uneven thick wall.

18.
TYPE LOCATION FUNCTION
Apical meristem Tips of stems and roots Growth, increase in length

Intercalary meristem Between the tip and base of Growth, increase length
stems and leaves between nodes
Lateral meristem Sides of stems and roots Growth, increase
in diameter

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 19. In most dicot stems, the vascular tissue consists of vascular bundles arranged in a ring. The xylem in each
vascular bundle is adjacent to the pith, and the phloem in each bundle is adjacent to the cortex. In most
monocot stems, the vascular bundles are scattered throughout the ground tissue, rather than forming a
ring.

20.
Tissue Structure Function

Upper and lower epidermis One cell thick, flattened cells Protective
lacking chloroplast
Stomata are sites of gezeous
Contains stomata which are exchange with the environment.
normally confined to, as more Their size is regulated by guard
numerous in the lower epidermis. cells, special epidermal, cells
Each stoma is surrounded by a pair containing chloroplasts.
of guard cells
Column shaped, cells with Main photosynthetic tissue.
numerous chloroplasts in a thin Chloroplasts may move toward
Palisade mesophyll light.
layer of cytoplasm

Irregularly shaped cells fitting Photosynthetic, but fewer

together loosely to leave large air chloroplasts than palisade cells.
spaces.
Gaseous exchange can occur
Spongy mesophyll
through the large air spaces via
stomata.

Store starch

Conduct water and mineral salts

Extensive finely branching removes products of
network through the leaf. photosynthesis.

Vascular tissue

21.
a) A is the upper epidermis; B is the palisade mesophyll; C is the spongy mesophyll; D is the lower
epidermis; E is the guard cell and F is the stoma.
b) Palisade mesophyll.
c) One popular theory is that in the presence of light, the guard cells carry out photosynthesis using their
chloroplasts. The accumulation of sugars in their cytoplasm raises the osmotic potential, and so water
enters the guard cells by osmosis. This leads to an increase in turgidity of guard cells which then
curve more due to their uneven thickness, and cause the stomatal pore to open. During darkness, the
guard cells cease to photosynthesize. Their osmotic pressure is lowered as their sugars are transported
out, and so water leaves the guard cells which then become flaccid causing their pore to close.

22. The vascular cambium and cork cambium.

23. The increase in length is due to the production of cells by the apical meristem, which lies at the top of a
stem. This is the primary growth. The secondary growth or the increase in diameter is caused by the
production of cells by the vascular cambium or lateral meristem.
24.
a)

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 b) Transport of soluble products of photosynthesis/sucrose/organic molecules.
c) To provide energy/enzymes/proteins for sieve tube cell; act as transfer cells/move solutes into and
out of the sieve tube cell.
d) Phloem sap flows from source to sink at rates as great as 1 m per hour, which is much too fast to be
accounted for by either diffusion of cytoplasmic streaming. Phloem sap moves by bulk flow, which
is driven by pressure. Thus the synonym pressure flow. Phloem loading results in a high concentration
at the source end of a sieve tube, which lowers the water potential and causes water to flow into the
tube and the pressure is greatest at the source end of the tube. At the sink end, the pressure is relieved
by the loss of water owing to water potential being lowered outside the sieve tube by the exodus of
sucrose. The building pressure at the end of the tube (source) and reduction of that pressure at the
opposite end (sink) cause water to flow from source to sink, carrying sugar along. Water is recycled
back from sink to source by xylem vessels.
25. (a) – (ix); (b) – (viii); (c) – (iv); (d) – (iii); (e) – (v); (f) – (vi); (g) – (ii); (h) – (vii); (i) – (i); (j) – (xi);
(k) – (xii); (l) – (x).

Chapter 10: Animal histology

1. The main animal tissues are the epithelial tissue, the nervous tissue, the muscle tissue and the connective
tissue.
2. Epithelial tissues, also called epithelia, are tissues specialized in the covering of external and internal
surfaces of the body. The general function of the epithelium is to provide protection and impermeability
(or selective permeability) to the covered structure. This justifies the epithelium's typical features: the
cellular juxtaposition forming layers of very proximate cells with diminished or none intercellular space
between each two neighbor cells.

3. The nervous tissue is formed of neurons and glial cells. The function of the nervous tissue is to receive
and to transmit neural impulses (reception and transmission of information). This function justifies the
characteristic morphology of neurons, with membrane projections (dendrites) to get information and an
elongated membrane projection (axon, or nerve fiber) to transmit information at distance. In their turn,
the glial cells support the neurons and facilitate their work (sometimes acting as insulators).

4. Muscle tissues are tissues made of cells able to perform contractions and thus to generate movement. The
function of the muscle tissue is to pull bones (skeletal striated muscle), to contract and move viscera and
vessels (smooth muscle) and to make the heart to beat (cardiac striated muscle). The muscle cells have
internal structures called sarcomeres where there are myosin and actin molecules disposed to create
contraction and distension (movement).
5. The main functions of the connective tissues are: supporting and filling of spaces; cellular nutrition;
energetic storage (fats); hematopoiesis (formation of blood, blood cells and blood components); immune
defense (specialized cells).
6. The matrix of the connective tissue is made of collagen fibers, elastic fibers and reticular fibers.
7. There are different collagen types. The main function of these proteins is to keep the shape and the
structural rigidity of the tissue. (Collagen is the most abundant protein of the human body.)
8.

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 Type Structure Location and Function

Blood Plasma (matrix) and red Within blood vessels

blood cells, white blood • Plasma—transports materials
cells, and platelets • RBCs—carry oxygen
• WBCs—destroy pathogens
• Platelets—prevent blood loss
Areolar Fibroblasts and a matrix Subcutaneous
(loose) of tissue fluid, collagen, • Connects skin to muscles; WBCs destroy pathogens
and elastin fibers Mucous membranes (digestive, respiratory, urinary,
reproductive tracts)
• WBCs destroy pathogens
Adipose Adipocytes that store Subcutaneous
fat (little matrix) • Stores excess energy
• Produces chemicals that influence appetite, use of
nutrients, and inflammation
Around eyes and Kidneys
Fibrous Mostly collagen fibers • Cushions tendons and ligaments (regular)
(matrix) with • Strong to withstand forces of movement of joints
few fibroblasts • The strong inner layer of the skin
Bone Osteocytes in a matrix Bones
of calcium salts and • Support the body
collagen • Protect internal organs from mechanical injury
• Store excess calcium
• Contain and protect red bone marrow
Cartilage Chondrocytes in a Wall of trachea
flexible protein matrix • Keeps airway open
On joint surfaces of bones
• Smooth to prevent friction
Tip of nose and outer ear
• Support
Between vertebrae
• Absorb shock

9. Epithelia are not vascularized (capillaries do not directly reach their cells). The epithelium exchanges
substances by diffusion with the connective tissue situated under it. Since the epithelia are not
vascularized minuscule skin injuries or scratches that happen all the time do not trigger bleeding and do
not expose the blood to contamination from external agents. This is an important protective strategy
discovered by evolution.
10. The epithelial tissues are classified according to the shape of the cells that form it (epithelial cells may be
cuboidal, columnar, or squamous) and according to the number of layers in which those cells are placed
in the tissue (into simple or stratified). The main types of epithelial tissues are simple cuboidal, simple
columnar, simple squamous, stratified squamous and pseudostratified columnar (resembling more than
one layer but actually having only one). There are also stratified cuboidal and stratified columnar epithelia
(rare).
11. The epidermis is the outer layer of the skin made of epithelial tissue. In the epidermis there are keratin-
secreting cells (keratinocytes). Keratin is an insoluble protein that impregnates the surface of the skin
providing protection and impermeability. In mammals keratin also forms the hairs. The keratinized cells
of the skin surface form the corneal layer. These cells die and are continuously replaced by others.
12. Cartilages are responsible for the structural support of the nose and ears. The trachea and the bronchi are
also organs with cartilaginous structures that prevent the closing of these tubes. In joints there are
cartilages that cover the bones providing a smooth surface to reduce the friction of the joint movement.
In the formation of bones the cartilages act as a mold and they are gradually substituted by the osseous
tissue.
13. The three main cell types of the osseous tissue are the osteoblasts, the osteocytes and the osteoclasts.
Osteoblasts are known as bone-forming cells since they are the cells that secrete the proteinaceous part of

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 the bone matrix (collagen, glycoproteins and proteoglycans). The bone matrix is the intercellular space
where the mineral substances of the bones are deposited. Osteocytes are differentiated mature osteoblasts
formed after these cells are completely surrounded by the bone matrix. Osteocytes have the function of
supporting the tissue. Osteoclasts are the giant multinucleate cells that remodelate the osseous tissue. They
are originated from monocytes and they contain many lisosomes. Osteoclasts secrete enzymes that digest
the osseous matrix creating canals throughout the tissue.
14. There are three types of muscle tissue: the skeletal striated muscle tissue, the cardiac striated muscle tissue
and the smooth muscle tissue. The striated muscles present under microscopic view transversal stripes
and their fibers (cells) are multinucleate (in the skeletal) or may have more than one nucleus (in the
cardiac). The smooth muscle does not present transversal stripes and it has spindle-shaped fibers each
with only one nucleus.

15. The functional units of the muscle fibers are the sarcomeres. Within the sarcomeres blocks of actin and
myosin molecules are posed in organized manner. The sarcomeres align in sequence forming myofibrils
that are longitudinally placed in the cytoplasm of the muscle fibers (cells). The grouping of consecutive
blocks of actin and myosin in parallel filaments creates the striped pattern of the striated muscle tissue
seen under the microscope.
16. In the sarcomere there are organized actin and myosin blocks. Troponin and tropomyosin also appear
associated to actin. The actin molecules when activated by calcium ions liberated in the proximities of the
sarcomere are pulled by myosin molecules. This interaction between actin and myosin shortens the
myofibrils originating the phenomenon of muscle contraction.
17. Schematically actin filaments attached perpendicularly to both sarcomere extremities (longitudinal sides)
make contact with myosin filaments positioned in the middle of the sarcomere and in parallel to the actin
filaments. Before the contraction the sarcomeres are extended (relaxed) since the contact between actin
and myosin filaments is only made by their extremities. During contraction actin filaments slide along the
myosin filaments and the sarcomeres shorten.
18.
a) A tissue is a group of cells with similar structure and function.
b) A: pseudostratified ciliated epithelium; B: simple cuboidal epithelium; C: stratified squamous
epithelium.
19. Brain and spinal cord. Nerve Tissue—neurons are specialized to generate and transmit impulses.
20.
a) Red blood cells transport oxygen; white blood cells help in the body defense and platelets are
involved in the process of blood clotting.
b) Red blood cells have no nuclei, have biconcave shape, have no mitochondria, contain hemoglobin.
c) Clotting is started almost immediately when an injury damages the endothelium of a blood vessel.
Platelets clump together, forming a plug at the site of injury. Then, proteins in the plasma called
coagulation factors, respond in a series of chemical reactions that form a tough protein called fibrin.
The fibrin strands form a web across the platelet plug, trapping red blood cells before they can leave
through the wound site. This mass of platelets, fibrin, and red blood cells forms a clot that hardens
into a scab. Certain nutrients are needed for the proper functioning of the clotting mechanism. Two
of these are calcium and vitamin K.
21.
a) A is the central canal containing blood vessels; B are the lamellae; C is the periosteum; D is the
osteocyte.
b) The functional unit of the bone is the Haversian system.
c) To bring nutrients to the bone cells and to remove metabolic wastes from the bone.
22.
 Structural Support of the Body: The skeleton supports the body against the pull of gravity.
The large bones of the lower limbs support the trunk when standing.
 Protection of Internal Organs: The skeleton provides a rigid frame work that supports and
protects the soft organs of the body. The fused bones of the cranium surround the brain to make
it less vulnerable to injury. Vertebrae surround and protect the spinal cord and bones of the rib
cage help protect the heart and lungs.
 Attachment of the Muscles: The skeleton provides attachment surfaces for muscles and tendons
which together enable movement of the body.

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  Movement of the Body: Bones work together with muscles as simple mechanical lever systems
to produce body movement.
 Production of Blood Cells: The formation of blood cells takes place mostly in the interior
(marrow) of certain types of bones.
23. A is the monocyte; B are red blood cells, C is the eosinophil, D is the neutrophil and E is the basophil.
24. Because the contractions are generated from the heart muscle itself.

25.
Features Skeletal Muscle Cardiac Muscle Smooth Muscle

Cell shape Very long, cylindrical cells Cylindrical cells that Spindle-shaped cells (15–200
(1–40 mm in length and branch (100–500 μm in μm in length; 5–10 μm in
may extend the entire length; 100–200 μm in diameter)
length of the muscle; 10– diameter)
100 μm in diameter)

Nucleus Multinucleated, Single, centrally located Single, centrally located

peripherally located

Striations Yes Yes No

Control Voluntary Involuntary Involuntary

Nervous Under the control of the Myogenic (the contractions Under the control of the
control nervous system are generated from the nervous system
muscle itself)

Function Body movement Contraction provides the Movement of food through the
major force for moving digestive tract, emptying of the
blood through the blood urinary bladder…
vessels

26.

Types of white blood cells Functions

Neutrophils  Phagocytosis of bacteria

 Release of antimicrobial chemicals
Eosinophils  Phagocytosis of antigen-antibody complexes, allergens
 Release enzymes that weaken or destroy parasites such as worms
(attack parasites too large to phagocytize)
Basophils  Secrete histamine (a vasodilator), which increases blood flow to a
tissue
 Secrete heparin (an anticoagulant), which promotes mobility of other
white blood cells by preventing clotting
Monocytes  Differentiate into macrophages (large phagocytic cells of the tissues)
 Phagocytize pathogens, dead neutrophils, and debris of dead cells
Lymphocytes  Secrete antibodies
 Serve in immune memory
 Destroy cancer cells, cells infected with viruses, and foreign cells

Chapter 11: Microbiology and hygiene

1. Beneficial effects of microorganisms: recycling of matter, production of vitamins, production of beer and
cheese, digestion of cellulose in ruminants...
Disadvantages of microorganisms: cause diseases; cause food spoilage, some are toxic...

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 2.
a) Antibody: Protein molecules released by the immune system in response to an antigen, which are
capable of neutralizing the effects of the antigen.
b) Antigen: A foreign molecule that elicits an immune response by lymphocytes.
c) Vaccine: A preparation of antigens given to provide artificial immunity.
d) Immunity: The state of being protected from an infectious disease, usually by having been exposed
to the infectious agent or a vaccine.
e) Interferon: A chemical produced by T cells or by cells infected with viruses; is part of innate
immunity and prevents the reproduction of viruses.
3. The increased permeability helps to attract phagocytic cells and lymphocytes. When phagocytes arrive at
the site of injury, they consume pathogens and cell debris, and the tissue heals.
4.
a) Reverse transcriptase is an enzyme that makes a copy of DNA from viral RNA.
b) Because they are not able to live outside of the host cell.
c) HIV is an RNA virus while a bacteriophage is a DNA virus.
HIV infects human while bacteriophages infect bacteria.
5. In active immunity, the body makes its own antibody against a pathogen whereas in passive immunity the
body acquires antibodies produced by another person or an animal.
6. Intact skin is a barrier that cannot normally be penetrated by bacteria or viruses, even minute abrasions
may allow their passage. Likewise, the mucous membranes that line the digestive, respiratory, and
genitourinary tracts bar the entry of potentially harmful microbes. Beyond their role as a physical barrier,
the skin and mucous membranes counter pathogens with chemical defenses. For example, secretions from
sebaceous and skin glands give the skin a PH ranging from 3 to 5, which is acidic to prevent colonization
by many microbes; the tears contain lyzozyme, an antimicrobial enzyme also present in saliva and mucous
secretions.

7.
a) Natural passive immunity
b) Artificial active immunity
c) Natural active immunity
d) Artificial passive immunity
8.
a) Capsule
b) Flagellun
c) Cell wall
d) Endospore
e) Toxins
9.
a) Vaccines include inactivated bacterial toxins, killed microbes, and viable but weakened microbes.
These agents can no longer cause disease, but they retain the ability to act as antigens, stimulating an
immune response, and more importantly, immunological memory. A vaccinated person who
encounters the actual pathogen will have the same quick secondary response based on memory cells
as a person who has had that disease.
b) Natural active immunity: This is the production of one’s own antibodies as a result of infection or
other natural exposure to an antigen. Natural passive immunity: this is a temporary immunity that
results from acquiring antibodies produced by another individual. The only natural way for this to
happen is for a fetus to acquire antibodies from the mother through the placenta before birth or for a
baby to acquire it through the colostrums or breast milk after birth.
c) There is no vaccine for HIV because HIV mutates after each replication.
d) A disease caused by a protozoan: malaria caused by Plasmodium falciparum.
A disease caused by a virus: AIDS caused by HIV virus.
A disease caused by a bacterium: tuberculosis caused by Mycobacterium tuberculosis.
10. Three cooperative lines of defense that counter these threats have evolved. Two of these are non specific;
that is they do not distinguish one infectious agent from another.
The first line of non specific defense is external consisting of epithelial tissues that cover and line our
bodies (skin and mucous membranes) and the secretions they produce.
The second line of non specific defense is internal: it is triggered by chemical signals and involves
phagocytic cells and antimicrobial proteins that indiscriminately attack invaders that penetrate the

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 body’s outer barriers. The appearance of inflammation is a sign that this second line of defense has been
deployed.
The third line is the immune system. The immune system comes into play simultaneously with the
second line of defense, but it responds in a specific way to particular micro organisms, aberrant body
cells, toxins, and other substances marked by foreign molecules.

11. Tuberculosis is a disease caused by the Mycobacterium tuberculosis, bacteria which attack other organs
of the body but mainly the lungs leading to respiratory insufficiency. Before 1940, tuberculosis had
already been one of the main causes of death in the USA and Europe. The disease can remain latent,
without manifestation for several years and even throughout the life. Tuberculosis is highly contagious,
transmitted by air route through sneezes and coughs from a person with the active disease. Transmission
is common between members of the same family or even in work environments. The disease today has
treatment with efficient antibiotics. Generally, the patient receives three different drugs for several months
until healing is complete. There is however some strains of multiresistant TB bacteria that emerged by
mutation and natural selection due to the intense use of antibiotic drugs mainly in hospitals and treatment
facilities; in these cases the treatment is more difficult.
12. Cholera is a bacterial disease caused by the Vibrio cholerae. The disease is transmitted by fecal-oral route
and the main mode of transmission is ingestion of contaminated water or food. It is most prevalent in
places that lack adequate sanitary conditions. Inside the human gut the cholera vibrion releases toxins
called enterotoxins. The infection can cause intense diarrhea, vomiting, dehydration and even death in
more severe case.
13. Incubation period is the time interval between the infection by an agent that causes disease and the first
signs or symptoms of the disease.

14. The Plasmodium infects the human blood causing destruction of red blood cells and it also affects the
liver. Malaria characterizes by periodical episodes of fever, chills and sweating that can be accompanied
by headache, nausea, vomiting and jaundice. The destruction of red blood cells may lead to anemia and
hypoxemia. The infection by Plasmodium falciparum if not treated can cause other complications and
even death.
15. HIV (human immunodeficiency virus) is supposed to be transmitted through blood, semen, vaginal
secretions and maternal milk. HIV is the virus that causes AIDS (acquired immune deficiency syndrome),
a disease characterized by destruction of cells of the immune system making the body susceptible to many
opportunistic and severe diseases.

16. HIV is a retrovirus, i.e., an RNA viral (its genetic material is RNA and not DNA). Reverse transcriptase
is a specific enzyme of the retrovirus responsible for the transcription of the viral RNA into DNA within
the infected (host) cell. This DNA then commands the production of viral proteins and the viral
replication.
17. CD4 lymphocytes are T helper lymphocytes that present in their plasma membrane receptor proteins
called CD4. CD4 lymphocytes are the cells that HIV infects and within which the virus replicates. HIV
has proteins in its capsule that bind to the CD4 receptors of lymphocytes. Through that bond the virus
fuses with the cell membrane and its content (RNA, reverse transcriptase, protease, etc.) penetrates into
the cytoplasm and the viral replication process begins. HIV RNA is then converted into DNA by the
reverse transcriptase. The new DNA is inserted into the genetic material of the lymphocyte with the aid
of enzymes called integrases. By transcription and translation this DNA commands the synthesis of
proteins necessary for the assemblage of new viruses. Long polypeptides are thus produced and then
fragmented into proteins and viral enzymes by the enzyme protease. So new HIV viruses are assembled
and break the cell membrane to gain the circulation.

18. The cause of the immunodeficiency presented by AIDS patients is the destruction of CD4 T helper
lymphocytes by the HIV. With this destruction the immune system becomes impaired and the body cannot
defend itself against many diseases that normally do not develop in immunocompetent people.

19. Tapeworms have hooks and sucking structures on their heads (scolex) that fixate the parasite in the gut
wall; these structures often do not injure the host tissue. The parasite obtains food and makes gas exchange
through absorption and diffusion across its skin; since it is a platyhelminth it does not have a digestive
system or a circulatory system.

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 20. The body of the tapeworm is made of segments called proglottids. The proglottids are reproductive
structures of the taenia and contain the organs that produce male and female gametes. As the proglottids
become distant from the scolex (head) they mature. Mature proglottids can fecundate themselves or
neighboring ones and the eggs formed are stored inside them. Proglottids called pregnant proglottids, full
of eggs, detach from the body of the worm and are eliminated with the human feces.

21. Pregnant proglottids with taenia eggs are released together with human feces. If ingested by the
intermediate hosts, swine or bovine, the eggs break inside their intestines and the larva trespass the mucosa
and gains the circulation to settle on muscles, heart, brain and other organs of these animals and then
differentiate into cystic larvae called cysticerci. Humans become infected when eating raw or badly
cooked swine or bovine meat contaminated by cysticerci. In the human intestines the cysticerci develop
into adult worms and the cycle goes on.

22. Adult ascaris that live within the human intestine can release up to 200 thousand eggs a day. The eggs are
eliminated with human feces and mature in the environment under some heat and moisture conditions.
Humans may ingest mature eggs through food contaminated by human feces or through bad hygienic
habits. The eggs again inside the human intestine release larvae that cross the enteric mucosa and gain the
circulation reaching the lungs. In the lungs the larva mature and go to the airway and to the pharynx when
they are then swallowed. Within the gut the larvae develop into adult worms.

23. A prion is an infectious (transmissible) protein able to replicate by transforming other proteins into a copy
of the prion. The mechanism of copying is not yet understood by science. The hypothesis come out from
research about a nervous system disease known as Creutzfeldt-Jacob disease, epidemiologically
associated to a bovine disease called bovine spongiform encephalitis (the mad cow disease). Research
discovered that the infectious agent that causes those diseases, suprisingly, was a protein capable of
copying itself and of being transmitted by ingestion (the reason why meat from contaminated animals
cannot be consumed).

24. Cancers are abnormal and uncontrolled proliferation of cells that can disseminate to other sites of the
body. Cancer dissemination at distance usually occurs through blood or lymphatic vessels.

25. In phagocytosis, white blood cells engulf and break down pathogens and other unwanted substances in
the body.
26. The inflammatory response causes changes that help remove the cause of tissue damage and start the
healing process. For example, nearby blood vessels dilate and change in other ways, allowing more blood
to flow to the area and blood components to leak into the damaged tissues.
27. Two major components of the second line of defense are the inflammatory response and phagocytosis.
Leukocytes include monocytes, macrophages, and neutrophils that go to sites of inflammation and destroy
pathogens and other unwanted substances through phagocytosis. Monocytes and macrophages also
produce cytokines and other chemicals that cause inflammation and fever.
28. Antigens are protein molecules that the immune system recognizes as nonself. Lymphocytes
“recognize” them with their surface receptor molecules, which bind only to specific antigen molecules.
29. Immunization causes an unexposed person to have an immune response to a particular pathogen, such
as the pathogen that causes measles. This leaves the person with memory cells for the pathogen. The
memory cells prevent future infections by the pathogen, so the person does not develop the disease.
30.
a) Mycobacterium tuberculosis; accept Mycobacterium bovis.
b) Infected person, coughs / sneezes / spits; aerosol / droplets, containing bacteria, breathed in by uninfected
person.
c) Sub-Saharan Africa; South-East Asia; countries of India / Pakistan / Afghanistan; South America /
Bolivia; Papua New Guinea.
d) TB linked with HIV infection; HIV weakens immune system; TB is an opportunistic disease; as many
people are infected although show no symptoms; transmission where there is, overcrowding / poor
housing; poverty; poor ventilation of housing; poor nutrition; poor access to health care; poorly organized
treatment for people with TB.

31.
a) Bacteria pass out in feces of infected person; carried in, water / food, consumed by uninfected person.

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 b)
i. 2.22
ii. Treatment for cholera involves supply of oral rehydration therapy (ORT); and provision of safe
drinking water; better response to emergencies (in some countries); effectiveness of response may
depend on number of cases; ref to very high number of cases in Haiti; may depend on remoteness of
regions affected by cholera; or ways in which, emergency supplies / personnel, can reach affected
areas; ref to high case fatality rates in, Nigeria / Cameroon; use of data to compare case fatality rates
in individual country with global rate.
iii. Cholera is a serious disease; death can occur very quickly after infection; spreads quickly in
population (especially after a disaster); deaths are avoidable; if ORT is available immediately; data
is useful to predict, situations / places, where cholera may occur; WHO can coordinate responses to
outbreaks.
c) Water supply is not contaminated with (human), sewage / feces; piped water / water supply is treated to
kill bacteria; V. cholera destroyed in sewage treatment.

32. Artificial active: antigens are introduced into the body by injection or by mouth, and stimulate an immune
response by B and T cells. This provides long-term immunity but is not immediate, as the immune
response takes several weeks to become effective. Artificial passive: antibodies are injected into the body
to give immediate protection against a pathogen or toxin. Antibodies are soon removed from circulation
and no immune response has occurred, so this is a temporary form of immunity.
33. Natural immunity is immunity gained by being infected (active) or by receiving antibodies from the
mother across the placenta or in breast milk (passive). Artificial immunity is gained either by vaccination
(active) or by injecting an immune serum containing antibodies (passive).
34. Autoimmune diseases are caused by the immune system producing antibodies against self antigens.

Chapter 12: Chemicals of life

1. Water is the fundamental solvent for chemical reactions of living beings; it is the main means of substance
transportation in the cell and between cells and tissues and it is responsible for the maintenance of
adequate temperature for the functioning of the organism. Water is also the reagent or the product of many
biochemical reactions, like photosynthesis, cellular respiration, peptide bond for protein formation, etc.

2. Calcium is present in almost all cells and has several functions. Calcium has an important role in muscular
contraction, in the blood coagulation process, in the structure of bone tissue, in teeth, in the motility of
the sperm cell flagellum and in the nervous transmission.

3. Iodine is a fundamental chemical element for the proper functioning of the thyroid since it is part of the
hormones produced by this gland. Iodine deficiency creates a kind of hypothyroidism, a disease known
as endemic goiter.

4. Pentoses are carbohydrates made of five carbons. The DNA molecule is made of a sequence of molecules
called nucleotides. Each nucleotide is formed by the association of one pentose called deoxyribose with
a phosphoric acid and a nitrogen-containing base (A, T, C or G). RNA is also formed by a sequence of
nucleotides. The RNA nucleotides are made by association of one ribose (a pentose) with one phosphoric
acid and one nitrogen-containing base (A, U, C or G). So pentoses are fundamental components of DNA
and RNA.

5. Polysaccharides have an energy storage function and a structural function. Polysaccharides incorporated
by living beings along the food chain are important sources of carbohydrates for the energetic metabolism
of organisms of the next trophic levels.

Starch is the polysaccharide used for energy store by plants. Glycogen is a macromolecule responsible
for the storage of glucose in the liver and muscles. Chitin is a polysaccharide with structural functions
that constitutes the exoskeleton of the arthropods and the cell wall in fungi.

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 6. The main types of lipids are triglycerides (fats and oils), phospholipids, waxes and steroids.

7. Triglycerides, fats or oils, are made of three molecules of fatty acids bound to one molecule of glycerol.
Hydroxyls of each one of the three fatty acids and each hydrogen of the hydroxyls of the glycerol bind to
form three molecules of water that are liberated.

The reaction between glycerol and a fatty acid is shown below:

8. Phospholipids are molecules made of glycerol bound to two long molecules of fatty acids and to one
phosphate group. Therefore, phospholipids are amphipathic molecules, i.e., they have a non-polar portion,
due to the long fatty acid chains, and a polar portion, due to the group phosphate. Phospholipids are the
main component of cell membranes. Sphingomyelin, the substance that forms the myelin sheath of axons
in the nervous system, is a phospholipid too. A phospholipid is shown below:

9. Steroids are lipids based in an angular combination of four carbon rings, three of them made of six carbons
and one ring made of five carbons in the extremity. The union of each ring to the adjacent ring is made
by the sharing of two adjacent carbons belonging to both rings. Bile salts, cholesterol, the sexual hormones
estrogen, progesterone and testosterone, the corticosteroids and the pro-vitamin D are examples of
steroids.

10. When it is said that a triglyceride is saturated it means that in its molecule the carbon chain is bound in
its maximum capacity to hydrogens, i.e., there are no double or triple bonds between carbons. These
saturated molecules are generally solid fats at normal temperature. Unsaturated triglyceride molecules are
those in which there are double or triple bonds between carbons and so they do not accomplish their
maximum capacity of hydrogenation. These unsaturated molecules in general are oils, liquid at normal

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 temperature. The terms saturated or unsaturated refer then to the saturation of the carbonic chain by
hydrogen atoms.

11. The constitutional units of proteins are the amino acids.

12. The primary protein structure is the linear sequence of amino acids that form the molecule. The primary
structure is the basis of the protein identity. Modification of only one amino acid of the primary structure
creates a different protein. This different protein can be inactive or can even have other biological
functions.

13. The secondary protein structure is generated by the manner its amino acids interact through the
intermolecular bond. These interactions create a spatial conformation of the polypeptide filament. The
two most studied secondary conformations of proteins are the alpha-helix and the beta-sheet.

14. The tertiary protein structure is a spatial conformation additional to the secondary structure in which the
alpha-helix or the beta-sheet folds itself up. The forces that keep the tertiary structure generally are
interactions between the –R groups of the amino acids and between other parts of the protein and water
molecules of the solution. The main types of tertiary structure of proteins are the globular proteins and
the fibrous proteins.

15. The quaternary protein structure is the spatial conformation due to interactions among polypeptide chains
that form the protein. Only those proteins made of two or more polypeptide chains have quaternary
structure. Insulin (two chains), hemoglobin (four chains) and the immunoglobulins (antibodies, four
chains) are some examples of protein having quaternary structure.

16. Secondary, tertiary and quaternary structures of proteins are spatial structures. Denaturation is
modification in any of these spatial structures that makes the protein deficient or biologically inactive.
After denaturation the primary protein structure is not affected.

17. Protein denaturation can be caused by temperature variation, pH change, changes in the concentration of
surrounding solutes and by other processes. Most proteins denature after certain elevation of temperature
or when in very acid or very basic solutions. This is one of the main reasons that it is necessary for the
organisms to keep stable temperature and pH.

18. Substrates are reagent molecules upon which enzymes act. The enzyme has spatial binding sites for the
attachment of its substrate. These sites are called activation centers of the enzyme. Substrates bind to
these centers forming the enzyme-substrate complex.

19. There are two main models that explain the formation of the enzyme-substrate complex: the lock and key
model and the induced fit model. In the lock and key model the enzyme has a region with specific spatial
conformation for the binding of the substrate. In the induced fit model the binding of the substrate induces
a change in the spatial configuration of the enzyme for the substrate to fit.

20. Initially as substrate concentration increases, the speed of the reaction increases; this happens because
free activation centers of the enzyme bind to free substrates. Once all activation centers of the available
enzymes become bound to their substrates new increments of the substrate concentration will have no
effect on the speed of the reaction.

21. Some enzymes need other associated molecules to work. These molecules are called enzyme cofactors
and they can be, for example, organic ions like mineral salts, or organic molecules. Inactive enzymes
which are not bound to their cofactors are called apoenzymes. Active enzymes bound to their cofactors
are called holoenzymes.

22.

a) DNA

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 b) Carbohydrate
c) Glycogen
d) Fats
e) Cholesterol
f) Fibers
g) Pentoses (ribose and deoxyribose)

23.
a) LOCK-AND-KEY HYPOTHESIS: The theory of enzyme action in which the enzyme active site
is complementary to the substrate molecules, like a lock and a key.
b) INDUCED FIT (hypothesis): The theory of enzyme action in which the enzyme molecule
changes shape to fit the substrate molecule more closely as it binds to it.
c) The activation energy is the energy necessary for a reaction to get started.
d) COENZYME: An organic non-protein molecule that binds temporarily with substrate to an
enzyme active site. It is essential on the enzyme activity. Example: NADH, FADH, NADPH.
e) Increasing the substrate concentration has no effect on non competitive inhibitor because they
do not compete for the active site.
24.
a) A is a competitive inhibitor; B is a non competitive inhibitor.
b) pH, temperature
c) 38°C
25.
Protein type 3D feature Solubility in Role Examples
water
Globular Roll up to form Usually soluble Usually have Enzymes found in all
balls metabolic organisms. Plasma
functions proteins and
antibodies
Fibrous Form fibres Usually insoluble Usually have Collagen found in
structural bone and cartilage,
functions Keratin found in hair,
nail
26. The sub unit of DNA is the nucleotide.
The sub unit of glycogen is α-glucose.
The sub unit of a fat is glycerol and fatty acids.
The sub unit of a protein is the amino acid.
27.
a)

b) Peptide bond.
28.
a) Glycerol and fatty acids.
b) Ester bond
c) This molecule has three fatty acids bonded to glycerol while in phospholipids one fatty acid is
replaced by a phosphate group.
d) Insulation, production of energy, energy storage, protection, biological membranes are made of
lipids, ...

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 29.
Food test Result Conclusion

Sample mixed with iodine in potassium Blue black colour Starch present
iodide
Sample boiled with Benedict’s solution Blue colour Reducing sugars absent

Sample treated with dilute acid, Red precipitate Non reducing sugars
neutralized and then tested with present, for example
Benedict’s solution sucrose

Sample tested using Biuret’s solution Blue ring at surface and on Proteins present
shaking lilac-purple solution
30.
a) In Alpha (α) glucose, the OH on carbon 1 is below the ring, in beta (β) glucose the -OH group
is above the ring.

b) Glycogen is a polymer of (α) glucose, there are 1,4 and 1,6 glycosidic bonds; branched chain; found
in liver/muscle/animal cells; cellulose is a polymer of beta (β) glucose; 1,4 glycosidic bonds only;
unbranched chains; found in plants.
c) Amylose forms a straight chain; 1,4 glycosidic bonds; amylopectin has branched structure; 1,4 and
1,6 glycosidic bonds.
31. 1 → c; 2 → a; 3 → b; 4 → d.
32.
Property Importance

a) Cooling of skin Water requires a relatively large Heat energy which is transferred to water
during sweating. amount of heat energy to molecules in sweat allows them to evaporate from
evaporate – that is, water has a the skin, which cools down, helping to prevent the
high latent heat of vaporization. body from overheating. A relatively large amount
of heat can be lost with minimal loss of water
from the body.

b) The transport of Water is a good solvent. Needed for transport by diffusion or active
glucose and ions transport into, out of and within cells. Also for
in a mammal. circulation in blood so that nutrients can reach the
sites where they are needed. Chemical reactions
take place in aqueous solution.

c) Much smaller Water has a high (specific) heat A more constant environment results, protecting
fluctuations in capacity. organisms from extremes of temperature which
lakes and oceans could be harmful.
than in terrestrial
habitats.

33.
a) Lactose could be a source of energy; it could be digested to, monosaccharides / glucose and galactose,
which could then be used as building blocks for larger molecules;
b) Condensation
c) Glycosidic bond

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 d) Glucose correctly drawn; galactose correctly drawn; Carbon atoms need not be numbered. Note that
galactose will probably be drawn ‘upside down’ as in the disaccharide – the conventional way of drawing
it is also shown in the diagram above. The form used to make the disaccharide is the beta form of
galactose, but students will not need to know this, other than for interest.

e) Alpha glucose / α-glucose; the –OH group on carbon atom 1 is below the ring
f) Carry out a Benedict’s test on both solutions; lactose would give a brick-red / brown precipitate, sucrose
would not; accept positive result for lactose, negative result for sucrose.
34.
a)

b) Primary structure
c) Water
d) Ring drawn around –OH or whole R group (–CH2OH) of serine
e) Rings drawn around two peptide bonds and bonds labeled appropriately.
35.
Category Example

Structural Collagen; keratin; elastin

Enzyme Amylase, catalase…

Hormone Insulin

Transport of respiratory gases Hemoglobin and myoglobin

Defensive Antibodies, fibrinogen

Contractile Actin and myosin

Storage casein / ovalbumin

36. X and Y are non-competitive inhibitors.

37.
 Macromolecules/polymers
 Polysaccharides
 Made from α-glucose
 Glucose units held together by 1,4 links (glycosidic bonds formed by condensation)
 Branches formed by 1,6 links.
38.

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Chapter 13: Autotrophic nutrition

1. Light from the sun is transformed into chemical energy contained in organic material by the
photosynthesis process. In photosynthesis light, water and carbon dioxide react and highly energetic
glucose molecules and molecular oxygen are made.
2. There are many beings (including all animals) that do not carry out photosynthesis. There are also
autotrophic beings that do not perform photosynthesis but they perform chemosynthesis. Plants, algae and
cyanobacteria are photosynthetic beings. In plants and algae, light is absorbed by chlorophyll, a molecule
present in cytoplasmic organelles called chloroplasts.
3. ADP phosphorylation is the addition of one inorganic phosphate in the molecule of adenosine diphosphate
thus creating ATP (adenosine triphosphate) and incorporating energy. The phosphorylation is oxidative
when the energy incorporated comes from the breaking of organic molecules having oxygen as reagent,
as in aerobic cellular respiration. The reaction is called photophosphorylation when the energy source is
light, as in photosynthesis. The energy incorporated into ATP is disposable (liberated) to other cellular
reactions when ATP hydrolyzes and ADP is formed again.
4. Free electrons, hydrogen ions and molecular oxygen are liberated, after the water photolysis. The
electrons will replace those electrons lost by chlorophyll molecules in photophosphorylation. The
hydrogen ions will be incorporated into hydrogen acceptor molecules (NADP) and later will be used in
the synthesis of glucose during the chemical stage. Molecular oxygen is liberated to the atmosphere.
5. All of our food, whether plant, algae, animal, or fungus, depends initially on photosynthesis to convert
sunlight into chemical energy. Most fuels we use – coal, oil, natural gas, and wood – are concentrated
products of ancient photosynthesis, which took hundreds of millions of years to form. All of the oxygen
in our atmosphere came from photosynthesis, and levels of carbon dioxide are determined at least in part
by the amount of photosynthesis. We can conserve or at least best use food resources by eating more
producers and fewer consumers, because less energy has been lost as heat at that level. We can slow the
depletion of limited fossil fuel resources by limiting their use in transportation, electricity, and heating –
or by substituting alternative sources of energy, such as solar, wind, or geothermal. We can maintain
Earth’s atmosphere by planting trees to take in more CO 2 and release more O2.

6. Photosynthesis makes food using sunlight energy, whereas chemosynthesis uses chemical energy stored
in inorganic molecules. Blue-green bacteria are photosynthetic autotrophs. Symbiotic bacteria living in
giant tubeworms at deep ocean vents are chemosynthetic autotrophs. Photosynthesis is quantitatively
more important, because it produces more than 99% of food for all life.

7. The membranes, including the membranes of the thylakoids, contain embedded pigments, enzymes, and
electron carriers in organized patterns. The pigments are arranged in photosystems, which efficiently
absorb light energy. The enzymes are ordered to carry out sequential chemical reactions. And the electron
carrier molecules are arranged in electron transport chains, which transfer small amounts of energy so
that it can be stored or used to do work. Thylakoids are flattened sacs that can accumulate ions to form
electrochemical gradients like water behind a dam; the gradient energy like water in a mill to build ATP.

8.
a) Transpiration is the loss of water in the gas state.

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 b)
 Stomata (stomatal transpiration): by evaporation of water from cells and diffusion of the water
vapour through stomata, the pores found in the epidermis of leaves and green stems.
 Cuticle (cuticular transpiration): by evaporation of water from the outer walls of epidermal cells
through the waxy cuticle covering the epidermis of leaves and stems.
 Lenticels (lenticular transpiration): by evaporation of water through lenticels. These are small slits
in the stems and bark of trees for gas exchange.
c) Advantages: cooling of the plant, transport of water and mineral salts.
Disadvantages: loss of the mechanical support of the plant, death of the plant in the case of excessive
transpiration.
d)
 Smaller leaves, particularly leaves shaped like needles. This reduces the total surface area of the
leaves. The total leaf surface area is also reduced, so that less water is lost by transpiration.
 A thicker waxy cuticle reduces evaporation.
 Closing the stomata when water availability is low.
 Rolling the leaves so that the lower epidermis is not exposed to the atmosphere.
 Some plants have a low water potential inside their leaf cells. This is achieved by maintaining a high
salt concentration inside their cells.
 Hairs on the surface of leaf trap a layer of air close to the surface. This air can become saturated
with moisture and will reduce the diffusion of water vapour out through the stomata.
 Having tissues tolerant to water loss (dessication).
 Some plants manage to live in dry places by having extremely deep roots which absorb water from
deep the soil.
 Some plants store water in large parenchyma cells contained within swollen stems and leaves.
 Many plants survive dry periods as seeds or spores, a method of evading drought.
9. Light dependent reactions and light independent reactions.
10.
a) Rubisco.
b) Phosphoglyceric acid (PGA).
c) Phosphoglyceraldehyde (PGAL).
d) 3 times
e) 9 ATP and 6 NADPH.
11. It has a thick cuticle. This reduces the amount of water lost through it.
It has rolled leaves. Rolling of the leaves prevents the lower epidermis to be exposed to the atmosphere
directly.
It has hairs on the surface of the leaf. Hairs on the surface of leaf trap a layer of air close to the surface.
This air can become saturated with moisture and will reduce the diffusion of water vapour out through
the stomata.
12. The effect of each factor can be seen in the table below:

13.
a) Use the tap.

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 b) Make sure the tap is closed; the point at which the plant shoot is inserted in the potometer should be
airtight; the plant stem should be inserted into the apparatus with everything submerged in water.
c) Diameter = 3.6 cm; radius = 1.8 cm.
Volume of water lost by transpiration = πr2h = 3.14 x (1.8cm)2 x 8 cm = 81.4 cm3
14. A is water; B is oxygen; C is carbon dioxide; D is the sugar; E and F are ATP and NADPH.
15. Light Reactions: B, D, F, G; Calvin Cycle: A, C, E.
16. Plants are mostly green because the primary pigment for photosynthesis is chlorophyll. Chlorophyll is
green because it absorbs violet-blue and red wavelengths of light and reflects or transmits green light.
Although accessory pigments such as xanthophylls and carotene absorb other wavelengths of light, (as
you realize in fall after chlorophyll is broken down!), chlorophyll dominates in most plants and algae and
even bacteria, so the living world – at least the producers – appear green. It might seem that black plants
would be even better because they would absorb all wavelengths of sunlight, but black plants would also
absorb more heat. The chemical reactions of life have optimal temperatures – too much heat denatures
enzymes and would significantly decrease the rate of photosynthesis.
17. Cycles allow small, controlled amounts of energy to be gained and stored at each step. The Calvin Cycle
begins and ends with the same “framework” molecule, but the process stores chemical energy in food
molecules such as glucose.
18. C-3 plants fix CO2 directly into the Calvin Cycle, which works well in habitats where moisture is abundant
and temperatures and not too high. C-4 and CAM plants have evolved preliminary fixation pathways,
which help them conserve water in hot, dry habitats. C-4 plants such as corn compartmentalize initial
carbon fixation in order to concentrate CO2 before sending it in to the Calvin Cycle. CAM plants such
some cacti open their stomata for preliminary CO2 fixation only at night, temporally isolating carbon
fixation from the Calvin Cycle.
19.
a) A is the photosystem 2, B is the photosystem 1.
b) Photolysis/splitting of water
c) Oxygen, NADPH and ATP.
20. Humans depend on photosynthesis for:
a) Eggs are produced by chickens using the energy and materials from food they receive from grains, which
make food by photosynthesis
b) Wood for furniture and homes is made by trees using the energy and materials from food they produce
by photosynthesis
c) Gasoline from oil, heat from oil, natural gas, or wood, and electricity from coal all derive their energy and
hydrocarbons from ancient photosynthesis by plants which lived hundreds of millions of years ago.
d) Breathable air contains about 20% oxygen gas; all the oxygen gas in the air is a product of photosynthesis.
The following human actions would affect photosynthesis:
i. Clear-cutting reduces plant uptake of CO2 and the increased CO2 concentration holds heat in the
atmosphere, resulting in global warming.
ii. Additional CO2 from burning fossil fuels adds to problems with global warming, and may raise
temperatures beyond the physiologically optimal range for plants. If temperatures are not raised, increased
CO2 could potentially increase photosynthesis – if we don’t cut down too many trees!
iii. If the water table drops, less water is available to plants. Those which are not adapted to extremely low
water levels – and even some that are – may not have sufficient water for photosynthesis.
21.
a) Phototactic movement
b) Aerotropic movement (a kind of chemotropic movement)
c) chemotropic movement
d) chemonastic movement
e) thigmonastic movement

22.
Hormone Where produced or found in plant Major functions

Auxin (IAA) Shoot apical meristems and young leaves are the Stimulates stem elongation (low concentration
primary sites of auxin synthesis. Root apical only); promotes the formation of lateral and

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 meristems also produce auxin, although the root adventitious roots; enhances apical dominance;
depends on the shoot for much of its auxin. functions in phototropism and gravitropism;
retards abscission
Cytokinins These are synthesized primarily in roots and Regulate cell division in shoots and roots;
transported to other organs, although there are minor modify apical dominance and promote lateral
sites of production as well. bud growth; stimulate seed germination, retards
leaf abscission.
Giberellins Meristems of apical buds and roots, young leaves, Stimulates stem elongation, seed development
and developing seeds are the primary sites of and germination
production.
Ethylene This gaseous hormone can be produces by almost all Promotes ripening of fruits, leaf abscission;
the parts of the plant. It is produced in high promotes root and root hair formation
concentrations during senescence, leaf abscission
and the ripening of fruits
Abscissic acid Almost all plant cells have the ability to synthesize Inhibits growth; promotes stomatal closure
(ABA) abscissic acid, and its presence has been detected in during drought stress; promotes seed dormancy
every major organ and living tissue; may be and inhibits early germination, promotes leaf
transportes in the phloem or xylem. senescence.

23. The process of non cyclic photophosphorylation

When photosystem II absorbs light, an electron is excited to a higher energy level in the reaction center
where it is captured by the primary electron acceptor.
An enzyme extracts electrons from water replacing each electron that the chlorophyll molecule lost when
it absorbs light energy. This reaction splits a water molecule into two hydrogen ions and an oxygen atom
which immediately combines with another to form oxygen. This is the water-splitting step of
photosynthesis that releases oxygen.
Each photoexcited electron passes from the primary electron acceptor of photosystem II to photosystem
I via an electron transport chain.
As the electrons cascade down the chain, their exergonic fall to a lower energy level is harnessed by the
thylakoid membrane to produce ATP. This ATP synthesis is called photophosphorylation because it is
driven by energy. Specifacally, ATP synthesis during non cyclic electron flow is called non cyclic
photophosphorylation. This ATP generated by the light reactions will provide chemical energy for the
synthesis of sugar during the Calvin cycle, the second major stage of photosynthesis.
The primary electron acceptor of photosystem I passes the photoexcited electrons to a second electron
transpory chain. An enzyme called NADP+ reductase then transfers the electrons together with H + to
NADP+. This is the redox reaction that stores the high energy electrons in NADPH, the molecule that will
provide reducing power for the synthesis of sugar in the Calvin cycle.

24.
CYCLIC NON CYCLIC

Pathways of electrons Cyclic Non cyclic

First electron donor Photosystem I Water
(Source of electrons)
Last electron acceptor Photosystem I NADP+
(destination of electrons)
Products ATP only ATP, NADPH AND O2
Photosystem involved I only I and II
25.
C3 PLANTS C4 PLANTS

Perform the Calvin cycle Yes Yes

Primary CO2 acceptor RUBP PEP
First product of CO2 fixation PGA Oxaloacetate
CO2 fixing enzyme Rubisco PEP carboxylase
Affinity of carboxylase for CO2 Moderate High
Photorespiration Extensive Minimal
Classes of chloroplasts One Two
Leaf anatomy: photosynthetic cells Mesophyll Mesophyll and bundle sheath

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 26.
a) To investigate a gas given out during photosynthesis.
b) X is oxygen; Y is a water plant such as Elodea.
c) Amount of carbon dioxide in the water; amount of chlorophyll in the leaves and the temperature.
d) Oxygen relights a growing splint.

e)

27.
a) i. To kill the protoplasm.
ii. To remove the green pigment (chlorophyll).
b) Brown colour (colour of iodine).
c) It had been destarched as it was kept in the dark.
d) To show that light is necessary for photosynthesis.

28. The three pathways which water follows are the apoplast pathway (cell walls), the symplast pathway
(cytoplasm and plasmodesmata) and the vacuolar pathway (from vacuole to vacuole).

o THE APOPLAST PATHWAY

The apoplast pathway is the system of adjacent cell walls which is the continuous throughout the plant.
Up to 50% of cellulose cell wall may be free space which can be occupied by water. As water evaporates
from the mesophyll cell walls into the intercellular air spaces, tension develops in the continuous stream
of water in the apoplast, and water is drawn through the walls in a mass flow by the cohesion of water
molecules. Water in the apoplast is supplied from the xylem.

o THE SYMPLAST PATHWAY

The symplast is the system of interconnected protoplasts in the plant. The cytoplasm of neighbouring
protoplasts is linked by plasmodesmata, the cytoplasmic strands which extend through pores in adjacent
cell walls. Once water, and solutes it contain, is taken into the cytoplasm of one cell it can move through
the symplast without having to cross further membranes. Movement might be aided by cytoplasmic
streaming. The symplast pathway is a more important pathway of water movement than the vacuolar
pathway.

o THE VACUOLAR PATHWAY

In the vacuolar pathway water moves from vacuole to vacuole through neighbouring cell, crossing the
symplast and apoplast in the process and moving through membranes and tonoplasts by osmosis.

29.
a) Rubisco
b) 6 times
c) ATP and NADPH
d) From the light dependent reactions
e) The enzyme is PEP carboxylase; the product is oxaloacetate.
30.
a) Chlorophyll electron moved to higher orbital by absorption of light.
b) Electron passed through series of redox reactions.
c) ATP generated in highly exergonic redox reactions.
d) Electron removed from H2O molecule.
e) Chlorophyll electron moved to higher orbital by absorption of light.
f) Electron passed through series of redox reactions.
g) Electron transferred to NADP+.
31. (a) – (iv); (b) – (i); (c) – (ii); (d) – (v); (e) – (iii).
32.

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 a) Phototropism
b) Shoot C is covered by an opaque cap for which reason the light doesn’t reach the shoot and the shoot
tip grows upwards. The shoot D is covered by a transparent cap through which light passes easily to
cause the shoot tip to bend in the direction of light.
c) Yes. The removal of the shoot tip removes the apical dominance causing the growth of lateral buds.

33. Soil solution > root hair cell > xylem vessel contents > mesophyll cell > dry atmospheric air.
34.
a) The loss of water vapor from the leaves / from the surface of a plant.
b) Light intensity; temperature.
c) Rate of water uptake shows the same pattern as rate of transpiration; but there is a time delay, with
changes in rate of transpiration occurring before changes in water uptake.
d) Transpiration causes water uptake; loss of water (by transpiration) sets up a water potential gradient
in the plant; water potential in roots is lower than water potential in soil; therefore water enters plant
through roots; time delay between rate of transpiration and rate of water uptake is due to time taken
for effect of transpiration to be transmitted through the plant.
35.
a)
i. When seed is forming / just after fertilization.
ii. Germination.
iii. Young immature leaf / leaf that is still growing.
iv. Mature photosynthesising leaf;
v. When food is being accumulated / when storage organ is growing (in size) / developing / end of
plant’s growing season / just before winter.
vi. When plant starts to grow (using food from the storage organ).
b)
i. To make starch; respiration;
ii. To make cellulose; respiration.
36.
a) Limiting factor: one factor, of many affecting a process, that is nearest its lowest value and hence is
rate-limiting.
b) Light intensity; light wavelength; concentration of carbon dioxide; temperature.
c) Shows that there are two sets of reactions in photosynthesis; a light dependent photochemical stage; a
light independent temperature-dependent stage; photochemical reactions are not affected by
temperature; at low light intensities, light intensity is the rate-limiting factor; at high light intensities
and low temperatures, temperature is the rate limiting factor.

37. Difference between tropic and nastic movement

Tropic movement Nastic movement

Dependent on the direction of the stimulus Independent of the direction of the stimulus

Involves growth Does not involve growth

Irreversible Reversible

Takes a short time (seconds) Takes a long time (days)

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 38.

Light dependent reactions Light independent reactions

Occur in the thylakoid membrane of the Occur in the stroma of the chloroplast
chloroplast
Use light energy to form ATP and NADPH Use ATP and NADPH to form the sugar

Splits water in photolysis to provide replacement Return ADP, inorganic phosphate and NADP to
of electrons and to release oxygen in the the light dependent reactions.
atmosphere.
Include two electron transport chains and Involves the Calvin cycle
photosystem I and II.

Chapter 14: Physiology of the nervous system

1. The structures that form the nervous system can be divided into the central nervous system (CNS) and the
peripheral nervous system (PNS). The organs of the CNS are the brain (cerebrum, brainstem and
cerebellum) and spinal cord. The PNS is made of nerves and neural ganglia. Besides these organs the
meninges (dura-mater, arachnoid and pia-mater) are part of the nervous system too since they cover and
protect the encephalon and the spinal cord.
2. The main cells of the nervous system are the neurons. Besides the neurons the nervous system is also
constituted of glial cells.
3. Glial cells and neurons are the cells that form the nervous system. Neurons are cells that have the function
of receiving and transmitting the neural impulses and glial cells (astrocytes, microgliacytes, ependymal
cells and oligodendrocytes) are the cells that support, feed and insulate (electrically) the neurons. The
Schwann cells that produce the myelin sheath of the peripheral nervous system can also be considered
glial cells.
4. The three mains parts into which a neuron can be didactically divided are: dendrites, cell body and axon.
Dendrites are projections of the plasma membrane that receive the neural impulse from other neurons.
The cell body is where the nucleus and the main cellular organelles are located. Axon is the long
membrane projection that transmits the neural impulse at distance to other neurons, to muscle cells and
to other effector cells.
5. Synapses are the structures that transmit the neural impulse between two neurons. When the electric
impulse arrives the presynaptic membrane of the axon releases neurotransmitters that bind to postsynaptic
receptors of the dendrites of the next cell. The activated state of these receptors alters the permeability of
the dendritic membrane and the electric depolarization propagates along the neuron plasma membrane to
its axon.
6. There are three types of neurons: afferent neurons, efferent neurons and interneurons. Afferent neurons
are those that only transmit sensory information from the tissues to neural nuclei and ganglia (where they
make connection with interneurons or effector neurons). Efferent neurons are those that transmit
commands to tasks performed in several parts of the body. Interneurons, also known as association
neurons or relay neurons, serve as connection between two other neurons. Afference is the conduction of
sensory impulses and efference is the conduction of effector impulses (impulses that command some body
action).
7. Axons extend throughout the body inside nerves. Nerves are axon-containing structures presenting many
axons and covered by connective tissue. The nerves connect neural nuclei and ganglia with the tissues.
Nerves may contain only sensory axons (sensory nerves), only motor axons (motor neurons) or both types
of axons (mixed nerves).

8. Ganglia (singular ganglion), or neural ganglia, are structures located outside the central nervous system
(for example, beside the spinal column or near viscera) made of concentration of neuron bodies. Examples
of neural ganglia are the ganglia that concentrate cell bodies of sensory neurons in the dorsal roots of the
spinal cord and the ganglia of the myenteric plexus responsible for the peristaltic movements of the
digestive tube. In the central nervous system (CNS) the concentrations of neuron bodies are called nuclei
and not ganglia.
9. The peripheral nervous system comprehends the nerves and ganglia of the body.

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 10. The function of the myelin sheath is to improve the safety and speed of the neural impulse transmission
along the axon. The myelin sheath serves as an electrical insulator preventing the dispersion of the impulse
to other adjacent structures. Since the myelin sheath has gaps called Ranviers’ nodes in its length, the
neural impulse “jumps” from one node to another thus increasing the speed of the neural transmission.
Not all neurons have a myelin sheath. There are myelinated axonal fibers and unmyelinated ones.
11. In the central nervous system (CNS) the myelin sheath is made by apposition of oligodendrocyte
membranes. Each oligodendrocyte can cover portions of axons of several different neurons. In the
peripheral nervous system (PNS) the myelin sheath is made by consecutive Schwann cell membranes
covering segments of a single axon. The Ranviers’ nodes appear in the intercellular space between these
cells. The myelin sheath is rich in lipids but it also contains proteins.

12. Meninges are the membranes that enclose and protect the central nervous system (CNS). Cerebrospinal
fluid is the fluid that separates the three layers that form the meninges and it has the functions of nutrient
transport, defense and mechanical protection for the CNS. The cerebrospinal fluid fills and protects
cavities of the brain and the spinal cord.
13. The concept of brain, or encephalon, comprehends the cerebrum (mostly referred to as the hemispheres,
but actually the concept also includes the thalamus and the hypothalamus), the brainstem (midbrain, pons
and medulla) and the cerebellum. Brain and spinal cord form the central nervous system (CNS).

14. The cerebrum is divided into two cerebral hemispheres, the right and the left. Each hemisphere is made
of four cerebral lobes: frontal lobe, parietal lobe, temporal lobe and occipital lobe.Each cerebral lobe
contains the gray matter and the white matter. The gray matter is the outer portion and it is made of neuron
bodies; the gray matter is also known as the cerebral cortex. The white matter is the inner portion and it
is white because it is in the region where axons of the cortical neurons pass.
15.

16. The two main ions that participate in the electrical impulse transmission in neurons are the sodium cation
(Na+) and the potassium cation (K+).
17. As in most cells the region just outside the surface of the neuron plasma membrane presents a positive
electrical charge in relation to the region just inside that thus is negative. The normal (at rest) potential
difference across the neuron membrane is about –70 mV (millivolts). This voltage is called the resting
potential of the neuron.
18. The excitation threshold of a neuron is the depolarization level that must be caused by a stimulus to be
transmitted as a neural impulse. This value is about –50 mV. The transmission of the neural impulse along
the neuronal membrane obeys an all-or-nothing rule: or it happens with maximum intensity or nothing
happens. Always and only when the excitation threshold is reached the depolarization continues and the
membrane reaches its maximum possible positive polarization, about +35 mV. If the excitation threshold
is not reached nothing happens.
19. Action potential is the maximum positive voltage level achieved by the neuron in the process of neuronal
activation, around + 35 mV. The action potential triggers the depolarization of the neighboring regions of
the plasma membrane and thus the propagation of the impulse along the neuron. Resting potential is the

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 membrane voltage when the cell is not excited, about –70 mV. Excitation threshold is the voltage level,
about –50 mV, that the initial depolarization must reach for the action potential to be attained.
20. The following are some neurotransmitters: adrenaline (epinephrine), noradrenaline (norepinephrine),
acetylcholine, dopamine, serotonin, histamine, gaba (gamma aminobutyric acid), glycine, aspartate, nitric
oxide.
21. Since the binding of neurotransmitters to the postsynaptic receptors is reversible, after these
neurochemicals perform their role they must be eliminated from the synaptic cleft. Neurotransmitters can
then bind to specific proteins that carry them back to the axon they came from in a process called
neurotransmitter re-uptake. They can also be destroyed by specific enzymes, like acetylcholinesterase, an
enzyme that destroys acetylcholine. Or they can simply diffuse out of the synaptic cleft.
22. Neuromuscular synapse is the structure through which the neural impulse passes from the axon of a motor
neuron to the muscle cell. This structure is also known as neuromuscular junction, or motor end plate. As
in the nervous synapse, the axonal terminal membrane releases the neurotransmitter acetylcholine in the
cleft between the two cells. Acetylcholine binds to specific receptors of the muscle membrane, dependent
sodium channels then open and the depolarization of the muscle membrane begins. The impulse is then
transmitted to the sarcoplasmic reticulum that releases calcium ions into the sarcomeres of the myofibrils
thus triggering contraction.
23.
a) A is the synaptic cleft; B is the vesicle containing neurotransmitters, C is the pre synaptic membrane;
D is the neurotransmitter, E is the ion channel of the post synaptic membrane; F is the post synaptic
membrane.
b) When the nerve impulse arrives at the pre synaptic membrane; the calcium ions are actively
transported in the pre synaptic neuron and make the release of neurotransmitters in the synaptic cleft.
c) Synapses are of two types: electrical synapses and chemical synapses. Electrical synapses: An
electrical synapse allows action potentials to spread directly from the presynaptic cell to the
postsynaptic cell. The cells are connected by gap junctions, intercellular channels that allow the local
ion currents of an action potential to flow between neurons. These make it possible for impulses to
travel from neuron to neuron without delay and with no loss of signal strength. However, chemical
synapses are much more common than electrical synapses in vertebrates and most invertebrates.
Chemical synapses: At a chemical synapse, a narrow gap, or synaptic cleft, separates the presynaptic
the presynaptic cell from the post synaptic cell. Because of the cleft, the cells are not electrically
coupled, and an action potential occurring in the presynaptic cell cannot be transmitted directly to the
membrane of the post synaptic cell. Instead, a series of events converts the electrical signal of the
actionpotential arriving at the synaptic terminal into a chemical signal that travels across the synapse,
where it is converted back into an electrical signal in the post synaptic cell.

24. A reflex is an automatic (involuntary) action caused by a defined stimulus and carried out through a reflex
arc. For example, a person stepping on a sharp object would start the reflex action through the creation of
a stimulus, (pain) within specialized pain receptors located in the skin tissue of the foot. The resulting
stimulus would be passed along sensory neurons to the spinal cord. This stimulus is usually processed
by an interneuron to create an immediate response to pain by initiating a motor response in the muscles
of the leg which pull the foot (effector) away from the object.

25. A is the parietal lobe; B is the frontal lobe; C is the temporal lobe and D is the occipital lobe.
26. Differences between the nervous and hormonal communication.

Nervous control Hormonal control

Involves nervous impulses (electrical) Involves hormones (chemical substance)

Impulses transmitted by neurons Hormones transported by blood
Quick response Usually a slow response
Response short-lived Response may be short-lived or long term
May be voluntary or involuntary Always involuntary
Usually localized May affect more than one target organ

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 27. There are 31 pairs of spinal nerves and 12 pairs of cranial nerves.
28.
a) A is the dorsal root ganglion; B is the dorsal root of spinal nerve; C is the central canal; D is the
ventral root of spinal root; E is the grey matter of spinal cord; F is the white matter of spinal cord.
b) The reflex arc is shown below

29. A is the cerebrum; B is the cerebellum; C is the brain stem and D is the spinal ord.
 The cerebrum has various functions such as vision, hearing, speech, emotions, language, and
other aspects of perceiving, thinking, and remembering.
 The cerebellum coordinates body movements.
 The brain stem is responsible for sustaining the basic functions of life, such as breathing and
blood pressure.
 The spinal cord functions in the transmission of ascending impulses to the brain and of
descending impulses from the brain to the cord.
30.
a) – 70 mV
b) Differences in ion concentration either side of the membrane; due to differential permeability of the
membrane; membrane permeable to potassium due to protein channels/gates, so potassium
accumulates inside axon; no channels for negative charged ions which are trapped inside, low
permeability to sodium ions, so they remain outside.
c) Permeability to sodium increases/sodium gates open; sodium ions flow into the axon.
d) Permeability to sodium decreases/sodium gates close; sodium ions pumped out of axon; increased
permeability to potassium; potassium ions flow into axon.
e) Period during which the resting potential is restored.
f) The longer the refractory period the fewer the number of impulses.
g) Too many potassium enter the membrane/potassium gates remain open; overshoot the resting
potential.
31.
a) It is +40 mV, which is positive.
b) It moves back to the resting potential of -70 mV.
c) The cell has an overall positive charge. The positive membrane potential indicates that the cell has
an overall positive charge at that point.
d) Initially it is the excess pumping of K+ from the cell that causes hyperpolarization. However, accept
reasonable answers that indicate the students understand that the efflux of cations (K + and Na+) can
cause the overall charge of the cell to become more negative.
e) Voltage is the potential energy across the membrane (the membrane potential).
f) The cell would remain hyperpolarized and unable to start another action potential.
g) Nerve impulses are conducted only in one direction.
32.
a) C: sodium ions, diffuse in / enter (the neurone); either depolarisation / described as the inside of the
membrane becoming more positive or less negative; D: potassium ions, diffuse out (from the neurone);
either repolarisation / described as the inside of the membrane becoming more negative or less positive;
E: refractory period; hyperpolarisation occurs / inside of the membrane is more negative than resting
potential.

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 b) The generator (or receptor) potential in A was not above the threshold (potential); in B it was above the
threshold (potential).

Chapter 15: sense organs

1. The main structures of the human eye are the cornea, the iris, the pupil, the ciliary muscles, the crystalline
lens and the retina (the space between the crystalline lens and the retina within the eyeball is filled with
vitreous humor).
2. The iris works like the diaphragm of a photographic camera since it has muscles that contract or relax
varying the pupil diameter. When the luminous intensity heightens the parasympathetic nervous system
commands the contraction of the pupil; when there is shortage of light the sympathetic nervous system
stimulates the dilation of the pupils. These movements depend upon the muscles of the iris.
3. The photoreceptor cells form the retina, a lamina that covers the internal posterior region of the eyeball.
The photosensitive cells of the retina are divided into two types: the cone cells and the rod cells. These
cells have pigments that sense specific light wave ranges (frequencies) and trigger action potentials
conducted by the optical nerves to the visual area of the brain.
4. Since the crystalline lens is a convex spherical lens it forms inverted images on the retina (every
converging lens forms inverted images). The inverted information follows through the optical nerves until
the occipital cerebral cortex that contains the visual area of the brain. In the brain the interpretation of the
image takes place and the inverted information is reverted.

5. Visual accommodation is the phenomenon of varying the curvature of the crystalline lens to make possible
the variation of its refractivity to adjust the images of objects exactly onto the retina. The visual
accommodation is accomplished by the action of the ciliary muscles.
6. Myopia is the visual condition in which the images are formed before (in front of) the retina.
Hypermetropia is the visual condition in which the point of image formation is beyond (behind) the retina.
Actually myopia is due to an increase in the distance between the retina and the crystalline lens, mainly
caused by a slight flattening of the eyeball. In hypermetropia the retina is too close to the crystalline lens
due to slight shortening of the eyeball. In myopia the near point and the far point of vision come closer
(the refractivity of the crystalline lens that corresponds to the maximum distension capacity of the ciliary
muscles is not enough to provide visual accommodation). In hypermetropia the ciliary muscles are not
able to contract more to compensate the inadequate position of the retina, i.e., the near point becomes
more distant.
7. The tympanum (or ear drum) is a membrane located in the middle ear just after the auditory canal and so
it separates the middle ear from the external ear. The function of the tympanum is to vibrate with the same
frequency of the sound waves that reach it.

8. The middle ear is formed by the tympanum, the ossicular chain and the oval window. The functional
ossicles of the middle ear are the hammer (malleus), the incus and the stapes.
9. Rod cells are highly sensitive to light which allows them to respond in dim light and dark conditions, but,
they cannot detect color. These are the cells which allow humans and other animals to see by moonlight,
or with very little available light (as in a dimly-lit room). This is why the darker conditions become, the
less color objects seem to have. Cone cells respond to different wavelengths of bright light to initiate a
nerve impulse, this is how we perceive color. They are also responsible for the sharpness of images. Cones
do not respond in poor light conditions.
10. Both senses depend on chemoreceptors that are found in the mouth and nose.
11. Each semicircular canal is filled with fluid called endolymph and motion sensors with little hairs line each
canal. Movement of the head and body cause the endolymph in the canals to move about. The hair cells
sense the strength and direction of the fluid’s movement and send electrical signals to the cerebellum
which interprets the information and responds to help keep the body’s sense of balance.
12. The sense of touch is the sense of pressure perception, which is generally felt in the skin. There are a
variety of receptors in the skin that respond to pressure, tension, and pain.
13. Receptors detect changes (stimuli) and generate impulses.
14. A is the sclera; B is the choroid; C is the retina; D are the blood vessels; E is the lens; F is the pupil; G is
the vitrous humour.
15. Name the part of the eye with each of the following functions:

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 a. Ciliary muscle and suspensory ligaments
b. Retina
c. Sclera
d. Neurons: Ganglion cells, bipolar cells and amacrine cells
e. Eyelid
f. Iris
g. Tear glands or lacrimal glands
h. Choroid
i. Ciliary body
16.
a) The cornea, aqueous humor, lens, and vitreous humor
b) The cone-shaped cells of the retina are individually connected to other nerve fibers, so that stimuli
to each individual cell are reproduced and, as a result, fine details can be distinguished. The rod-
shaped cells, on the other hand, are connected in groups so that they respond to stimuli over a general
area. Rods are affected by light of low intensities and unable to distinguish color whereas cones are
affected by light of high intensities and are able to distinguish the colors.
c) The optic nerve. The visual areas are in the occipital lobes of the cerebral cortex.

17.
a) When sound waves enter the ear canal, vibrations are transmitted by the following sequence of structures:
eardrum, malleus, incus, stapes, oval window of the inner ear, and perilymph and endolymph within the
cochlea.
b) The organ of Corti in the cochlea.
c) The utricle and saccule
d) The semi circular canals
e) Transmits to the brain the nerve impulses about hearing and equilibrium
f) The auditory areas are in the temporal lobes of the cerebral cortex.
g) The cerebellum, and the temporal lobes of the cerebrum

18. A is the pinna; B is the auditory canal; C is the eardrum; D is the semi circular canals; E is the Eustachian
tube; F is the cochlea.
19.
a) Protection, thermoregulation, sensation, synthesis of vitamin D.
b) A is the epidermis; B is the dermis; C is the layer of fat; D is the blood vessel; E is the sweet gland;
F is the hair follicle; G is the muscle; H is the nerve ending; I is the sweet pore.

Chapter 16: Endocrinology

1. The endocrine system is constituted by the endocrine glands and the hormones they secrete.
2. The endocrine system is said to have integrative character since the hormones produced by the endocrine
glands are substances that act at a distance and many of them act in different organs of the body. So the
endocrine glands receive information from some regions of the body and they can produce effects in other
regions providing functional integration for the body. Besides the endocrine system, the other organ
system that also has integrative function is the nervous system. The nervous system integrates the body
through a network of nerves connected to central and peripheral neurons. The endocrine system integrates
the body through hormones that travel through the circulation and are produced by the endocrine glands.
3. Hormones are substances secreted by the endocrine glands and collected by the circulation that act to
produce effects upon specific organs and tissues.
4. Target organs, target tissues and target cells are those specific organs, tissues and cells upon which each
hormone acts and produces its effects. Hormones selectively act upon their targets due to specific receptor
proteins present in these targets.
5. The circulatory system is fundamental for the functioning of the endocrine system. The blood collects the
hormones made by the endocrine glands and through the circulation these hormones reach their targets.
Without the circulatory system the 'action at distance' characteristic of the endocrine system would not be
possible.

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 6. Some hormones are proteins, like insulin, glucagon and ADH, others are derived from proteins (modified
amino acids), like adrenaline and noradrenaline, other are steroids, like the corticosteroids and estrogen.
7. The hypophysis is divided into two portions: the adenohypophysis, or anterior hypophysis, and the
neurohypophysis, or posterior hypophysis. In the adenohypophysis two hormones that act directly, the
growth hormone (GH) and the prolactin, and four tropic hormones, i.e., hormones that regulate other
endocrine glands, the adrenocorticotropic hormone (ACTH), the thyroid-stimulating hormone (TSH), the
luteinizing hormone (LH) and the follicle-stimulating hormone (FSH) are produced. The neurohypohysis
stores and releases two hormones produced in the hypothalamus, oxytocin and the antidiuretic hormone
(ADH, or vasopressin).
8. The hypothalamus is a part of the brain situated just above the hypophysis. The hypothalamus gets
peripheral and central neural impulses that trigger response of its neurosecretory cells. The axons of these
cells go down to the adenohypophysis to regulate the hipophyseal secretions by means of negative
feedback. When the plasma levels of adenohypophyseal hormones are too high the hypothalamus detects
this information and commands the interruption of the production of the hormone. When the blood level
of an adenohypophyseal hormone is low the hypothalamus stimulates the secretion of the hormone. The
hypothalamic cells produce the hormones released by the neurohypophysis. These hormones are
transported by their axons to the hypophysis and then released in the circulation.
9. In childhood deficient GH secretion may lead to delayed growth and in severe cases to nanism (dwarfism).
Excessive production of GH in children may cause exaggerated osseous growth and gigantism. In adults
GH excess (for example, in hypophiseal cancer or in people that wrongly ingest GH as a nutritional
supplement) may lead to acromegaly, excessive and disproportional growth of the bone extremities, like
the skull, the maxillaries, the hands and the feet.
10. GH: bones, cartilages and muscles. Prolactin: mammary glands. ACTH: the cortical portion of the
adrenals. TSH: thyroid gland. FSH and LH: ovaries and testicles.

11. The three main signs of diabetes mellitus are known as the diabetic triad: polyuria, polydipsia and
polyphagia. Polyuria is the excessive elimination of urine; in diabetes it is caused by reduced water
reabsorption in the renal tubules due to increased osmolarity of the glomerular filtrate (caused by
excessive glucose). Polydipsia is the exaggerated ingestion of water; the thirst is due to the excessive
water loss in the urine. Polyphagia is the exaggerated ingestion of food caused by deficiency in energy
generation by glucose-lacking cells.

12. Diabetes mellitus is the disease caused by deficient insulin secretion by the pancreas or by impaired
capturing of this hormone by the cells. Diabetes insipidus is the disease caused by deficient ADH secretion
by the pituitary (hypophysis) or also by impaired sensitivity of the kidneys to this hormone. In diabetes
insipidus the blood lacks ADH and so tubular reabsorption of water in the kidneys is reduced and a great
volume of urine is produced. The patient urinates a lot and many times a day, a sign also accompanied by
polydipsia (increased thirst and exaggerated ingestion of water) and sometimes by dehydration.
13. Alcohol inhibits the ADH (antidiuretic hormone) secretion by the hypophysis. Low ADH reduces the
tubular reabsorption of water in the kidneys and thus the urinary volume increases.
14. Type I diabetes, also known as juvenile diabetes, or insulin-dependent diabetes (this name is not adequate
as type II diabetes may become insulin-dependent), is the impaired production of insulin by the pancreas
believed to be caused by destruction of cells of the islets of Langerhans by autoantibodies (autoimmunity).
Type II diabetes occurs in the adult individual and it is often diagnosed in people of more advanced age.
In type II diabetes there is normal or low secretion of insulin by the pancreas but the main cause of the
high glycemia is the peripheral resistance of the cells to the action of the hormone.
15.
ENDOCRINE GLAND EXOCRINE GLAND

Are ductless glands Are ducted glands

Their products are released directly into the Their products are released into the lumen or
blood the outside of the body

Produce hormones Do not make hormones

They have target organs on which they act No target organs

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 Their products are mainly proteins in nature They produce various types of substances

They have internal secretion They have external secretion

16. A is the pineal gland; B is the hypothalamus; C is the pituitary gland; D is the thyroid gland; E are the
parathyroid glands; F is the thymus; G are the adrenal glands; H is the pancreas; I is the ovary and J is the
testis.
17. A hormone is a chemical messenger. It has the following properties:
 It travels in the blood;
 It has its effect at a site different from the site where it is made, called the target, hence the term
messenger;
 It fits precisely into receptor molecules in the target like a key in a lock. It is therefore specific
for a particular target;
 It is a small soluble molecule;
 It is effective in low concentrations.

18. Most hormones use negative feedback, in which release of an initial hormone stimulates release of
production of other hormones or substances that subsequently inhibit further release of initial hormone.
The example is the production of the thyroid hormone thyroxin. For the case of production of thyroxin,
the hypothalamus secretes TRH (TSH releasing hormone), which stimulates the anterior pituitary to
secrete TSH (thyroid stimulating hormone). When TSH binds to specific receptors in the thyroid gland,
this gland synthesizes thyroxin hormone. The system is balanced by negative feedback loops. High levels
of thyroxin and TSH in the blood inhibit TRH secretion by the hypothalamus. There is also evidence that
additional feedback loops are involved; for example high levels of TSH may inhibit TRH secretion by the
hypothalamus.
19.

a) i. A tropic hormone is an hormone that has another endocrine gland as its target.
ii. An exocrine gland is a gland that has a duct and releases its product on the outside of the body or
in a body cavity.
b)
Hormone Endocrine gland Target cell / organ
ADH Produced by the Hypothalamus; stored Kidney
and released by the posterior pituitary
Prolactin Anterior pituitary Mammary glands
Epinephrine Adrenal medulla Liver, heart, muscles
Calcitonin Thyroid Bones, kidney, intestines

c) Hypersecretion of GH causes gigantism in children and acromegaly (abnormal growth of bones in

the hands, feet and head) in adults; hyposecretion in children causes pituitary dwarfism.
Hypersecretion of epinephrine causes the increase of blood pressure.

20. The four parathyroid glands, embedded in the surface of the thyroid gland, function in the homeostasis of
calcium ions. They secrete parathyroid hormone (PTH) which raises blood levels of calcium and thus has
an effect opposite to that of the thyroid hormone calcitonin. Parathyroid hormone elevates blood calcium
by stimulating calcium reabsorption in the kidneys and by inducing specialized bone cells called
osteoclasts to decompose the bone and release calcium in the blood. It also increases calcium uptake in
the small intestines. Calcitonin has just the opposite effects on the kidney and bone, thus decreasing blood
calcium.
21. In fact, as soon as the concentration of glucose exceeds the normal range, excess glucose is cleared from
the blood by the action of insulin. It is then stored into glycogen. When the level of glucose drops below
the set point, glucagon signals the liver cells to increase glycogen hydrolysis, convert amino acids to sugar
and start slowly releasing glucose back to the circulation. The antagonistic effects of glucagon and insulin
are vital to glucose homeostasis, a mechanism that precisely manages both fuel storage and fuel used by
body cells.

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 22. Prostaglandins are hormone like substances synthesized by cells from the phospholipids of their cell
membranes; exert their effects locally. They are involved in inflammation and pain, reproduction, nutrient
metabolism, changes in blood vessels, blood clotting.
23. Aldosterone increases reabsorption of sodium and excretion of potassium by the kidneys. Results:
hydrogen ions are excreted in exchange for sodium; chloride and bicarbonate ions and water follow
sodium back to the blood; maintains normal blood pH, blood volume, and blood pressure.
24.

Gland Hormone Action

Adrenal cortex Aldosterone Controls reabsorption of Na+ in the
kidney.
Produced in the ADH Increases the permeability of convoluted
hypothalamus, stored in the distal tubule and collecting duct.
posterior pituitary
Adrenal medulla Adrenaline Increases heart rate.
(epinephrine)
Alpha cells in pancreas Glucagon Increases blood glucose level.
Beta cells in the pancreas Insulin Decreases blood glucose level.
Ovary Oestrogen Repair and growth of the endometrium.
Hypothalamus Releasing hormone Stimulates the anterior pituitary gland to
release FSH.
Produced in the Oxytocin Stimulates contraction of the uterus.
hypothalamus, stored in the
posterior pituitary
Anterior pituitary Prolactin Stimulates the mammary glands to secrete
milk.

Chapter 17: Homeostasis, excretion and thermoregulation

1. The homeostatic maintenance of the body mostly occurs by means of alternating antagonistic compensatory
mechanisms. There are regulators that lower the pH and others that increase it, there are effectors whose
function is to increase the body temperature and others that lower it, hormones exist that, e.g., reduce the
level of glucose in the blood and others that increase the glycemic level. The use of antagonistic mechanisms
is a strategy found by evolution to solve the problem of the maintenance of the body equilibrium.
2. Negative feedback happens when the response to a given action generates an effect that inhibits that action.
For example, when the carbon dioxide concentration in blood is high the pulmonary respiration is stimulated
for the CO2 excess to be expelled through expiration. Hyperventilation, however, lowers the carbon dioxide
concentration in blood too much generating a negative feedback that commands the reduction of the
respiratory frequency. Negative feedback is the main mechanism of homeostasis and it occurs in a variety of
processes, such as in blood pressure control, glycemic control, regulation of body temperature, etc.
3. In positive feedback the effect caused by an action stimulates the action even more. This is a rarer mechanism
of the homeostatic regulation. An example of positive is the release of oxytocin to intensify the contractions
that take place during childbirth. Another example of a positive feedback mechanism is milk production
by a mother for her baby. As the baby suckles, nerve messages from the mammary glands cause the hormone
prolactin, to be secreted by the mother’s pituitary gland. The more the baby suckles, the more prolactin is
released, which stimulates further milk production by the mother’s mammary glands. In this case, a negative
feedback loop would be unhelpful because the more the baby nursed, the less milk would be produced.
4. Excretion in Physiology is the process of elimination of metabolic wastes and other toxic substances from
the body.
5. The main nitrogen wastes excreted by living beings are ammonia, uric acid and urea. Living beings that
secrete ammonia are known as ammoniotelic. Creatures that secrete uric acid are known as uricotelic.
Organisms that secrete urea are called ureotelic.
6. Human beings excrete mainly urea eliminated with the urine.
7. Urea is a product of the degradation of amino acids. In the process amino acids lose their amine group which
is then transformed into ammonia. In the liver ammonia reacts with carbon dioxide to form urea and water,

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 a process called ureogenesis. In the intermediary reactions of the ureogenesis a molecule of ornithine is
consumed and another is produced. For this reason ureogenesis is also known as the ornithine cycle.
8. The functional (filtering) unity of the kidneys is the nephron. A nephron is made of afferent arteriole, efferent
arteriole, glomerulus, Bowman's capsule, proximal tubule, loop of Henle, distal tubule and collecting duct.
In each kidney there are about one million nephrons.
9.

10. Urine is made by the occurrence of three processes in the nephron: glomerular filtration, tubular
reabsorption and tubular secretion. In the nephron the blood carried by the afferent arteriole enters the
glomerular capillary network where it is filtered. The filtration implies that part of the blood returns to the
circulation through the efferent arteriole and the other part, known as the glomerular filtrate, enters the
proximal tubule of the nephron. In the nephron tubules (also known as convoluted tubules) substances of the
glomerular filtrate like water, ions and small organic molecules are reabsorbed by the cells of the tubule wall
and gain again the circulation. These cells also secrete other substances inside the tubules. The urine is formed
of not reabsorbed filtered substances and of secreted (by the tubules) substances. Urine is drained by the
collecting ducts to the ureter of each kidney, then it enters the bladder and later it is discharged through the
urethra. The nephron tubules are surrounded by an extensive capillary network that collects resorbed
substances and provides others to be secreted.
11. Glomerular filtrate is the name given to the plasma after it has passed the glomerulus and entered the
Bowman’s capsule. The glomerular filtrate has a different composition compared to urine since the fluid has
not yet undergone tubular reabsorption and secretion. The main difference between the blood and the
glomerular filtrate is that in the latter the amount of proteins is at a minimum and there are no cells or blood
platelets.
12. Proteinuria means losing of proteins through urine. Under normal conditions proteins are too big to be filtered
by the glomerulus and they are practically absent in the urine (the few filtered proteins may also be resorbed
in the nephron tubules). Proteinuria is an indication that a more thanexpectedamount of proteins is passing
the glomerulus suggesting glomerular disease, e.g., in diabetic nephropathy. The glomerulus also blocks the
passage of blood cells and platelets (hematuria is often a sign of urinary disease although less specific of
kidneys since the blood may come from the lower parts of the excretory tract).
13. Only 0.5 to 1% of the glomerular filtrate is eliminated as urine. The remaining volume, containing mainly
metabolic ions, glucose, amino acids and water, is reabsorbed through the nephron tubules (by means of
active or passive transport) and gains the blood circulation again. The convolute tubules of the nephron are
responsible for the reabsorption of substances.

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 14. The cells of the tubule wall have high number of mitochondria because many substances are reabsorbed or
secreted through them by means of active transport (a process that spends energy). Therefore many
mitochondria are necessary for the energetic supply (ATP supply) of this type of transport.
15. Tubular secretion is the passage of substances from the blood capillaries that surround the nephron tubules
to the tubular lumen for these substances to be excreted with urine. Ammonia, uric acid, potassium,
bicarbonate and hydrogen ions, metabolic acids and bases, various ingested drugs (medicines) and other
substances are secreted by the nephron tubules.
16. Antidiuretic hormone (or ADH, or vasopressin), aldosterone and atrial natriuretic peptide (or ANP) are
hormones that participate in the regulation of the excretory system.
17. The antidiuretic hormone is secreted by the hypophysis (also known as pituitary) and it acts in the nephron
tubules increasing the reabsorption of water. When the body needs to retain water, for example, in cases of
blood loss and abrupt blood pressure lowering or in cases of abnormally high blood osmolarity, there is
stimulus for ADH secretion. When the body has an excess of water, as in cases of excessive ingestion or in
abnormally low blood osmolarity, the secretion of ADH is blocked and the diuresis increases. ADH is also
known as vasopressin since it increases the blood volume and thus heightens the blood pressure.
18. Aldosterone is a hormone that acts upon the nephron tubules stimulating the reabsorption of sodium.
Therefore it contributes to the increase of the blood osmolarity and consequently to the increase of the blood
pressure. Aldosterone is made by the adrenals, glands located over the superior portion of the kidneys.
19. Hemodialysis is the artificial blood filtration made by specific machines in substitution of the kidneys.
Hemodialysis may be necessary in patients suffering from diseases that cause renal failure, like diabetic renal
complications, lupic renal complications and others. During hemodialysis the blood of the patient is deviated
to the filtering machine and after the filtration it returns to the body.
20.

a) Excretion is the process of elimination of metabolic wastes and other toxic substances from the body.
b) The nitrogenous waste product of a fish is ammonia while that of an insect is uric acid.
c) Narrower diameter increases pressure inside capillary and forces plasma out of the blood into the
Bowman’s capsule.
d) i. A is the Bowman’s capsule; B is the glomerulus and C is the afferent arteriole.

ii. The fluid found in A is the filtrate; the fluid found in B is the blood.

iii. Ultrafiltration

iv. The fluid in B contains blood cells and big proteins while in A they are not present.

21.

a)
i.
HOMEOSTASIS is the maintenance of steady internal environment.
ii.
Interstitial fluid (or tissue fluid) is a solution that bathes and surrounds the cells of multicellular
animals.
b) The blood contains red blood cells and platelets whereas they are not present in the tissue fluid.
c) Fluid recovery; absorption of lipids and immunity.
d) Thymus, spleen, lymph nodes, tonsils…
e) The body is unable to store proteins or amino acids, and any surplus is destroyed in the liver. Excess amino
acids, brought to the liver by the hepatic portal vein, are deaminated by the liver cells. In this process the
amino (NH2) group is removed from the amino acid, with the formation of ammonia. The amino acid residue
is then fed into carbohydrate metabolism and oxidized with the release of energy. Meanwhile the ammonia
must not be allowed to accumulate because it is highly toxic even in small quantities. Under the influence of
specific enzymes in the liver cells, the ammonia enters a cyclical series of reactions (the ornithine cycle) in
which it reacts with carbon dioxide to form the less toxic nitrogenous compound urea. The urea is then shed
from the liver into the bloodstream, and taken to the kidney which eliminates it from the body.

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 22. Tubular secretion takes place from the blood in the peritubular capillaries to the filtrate in the renal tubule;
creatinine and other waste products are secreted into the filtrate to be excreted in urine; secretion of H + ions
helps maintain pH of blood.
23.

a) Osmosis e) Passive transport

b) Active transport f) Active transport
c) Pinocytosis g) Active transport
d) Active transport
24. Abdominal aorta → renal artery → small arteries in the kidney → afferent arterioles → glomeruli → efferent
arterioles → peritubular capillaries → small veins in the kidney → renal vein → inferior vena cava.
25.

a) Aldosterone
b) ADH
c) Parathyroid hormone
d) Aldosterone

26.
a) To produce a concentrated filtrate / to absorb as much water as possible.
b) Water released by metabolism mainly the metabolism of fats.
c) Active at night when cooler; stay in burrow during day; burrows are cool and sheltered so less water is
lost.
27. The table below shows the quantity of substances which are filtered, reabsorbed or secreted in the kidney.
Substance Quantity filtered into Quantity Quantity excreted % of filtered
nephron each day reabsorbed per day per day which is
reabsorbed

Water 180 litres 178.5 1.5 99.2

Glucose 800 mEq 799.5 0.5 99.9

Urea 56 g 28 28 50

Sodium ions 25,200 mEq 25,050 150 99.4

Chloride ions 18,000 mEq 17,850 150 99.2

Potassium ions 720 mEq 620 100 86.1

a. The last column in the table. (Note: divide the quantity reabsorbed by the quantity filtered and multiply
by 100, e.g. 178.5/180×100)
b. Glucose is required for body respiration; it is too valuable to be excreted.
c. Diabetes
d. Concentration of urea higher in filtrate; so diffuses into blood / diffuses down concentration gradient

28. If body fluids are becoming too acidic, the kidneys will secrete more H+ ions into the renal filtrate and will
return more HCO3- ions to the blood. This will help raise the pH of the blood back to normal.
29. The kidneys secrete rennin when blood pressure decreases. When blood pressure decreases, the
juxtaglomerular (juxta means “next to”) cells in the walls of the afferent arterioles secrete the enzyme renin.
Renin then initiates the renin-angiotensin mechanism to raise blood pressure. The end product of this
mechanism is angiotensin II, which causes vasoconstriction and increases the secretion of aldosterone, both
of which help raise blood pressure.
30. This hormone is secreted whenever the blood oxygen level decreases (a state of hypoxia). Erythropoietin
stimulates the red bone marrow to increase the rate of RBC production. With more RBCs in circulation, the
oxygen-carrying capacity of the blood is greater, and the hypoxic state may be corrected.

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 31. The hypothalamus is the thermostat of the body and regulates body temperature by balancing heat production
and heat loss.

32. In hot conditions

a. Sweat glands under the skin secrete sweat (a fluid containing mostly water with some dissolved ions) which
travels up the sweat duct, through the sweat pore and onto the surface of the skin. This causes heat loss via
evaporative cooling; however, a lot of essential water is lost.
b. The hairs on the skin lie flat, preventing heat from being trapped by the layer of still air between the hairs.
c. Vasodilation occurs; this is the process of relaxation of smooth muscle in arteriole walls allowing increased
blood flow through the artery. This redirects blood into the superficial capillaries in the skin increasing heat
loss by convection and conduction.

In cold conditions

a) Sweat stops being produced.

b) The minute muscles under the surface of the skin called arrector pili muscles (attached to an individual hair
follicle) contract (piloerection), lifting the hair follicle upright.
c) Arterioles carrying blood to superficial capillaries under the surface of the skin can shrink (constrict), thereby
rerouting blood away from the skin and towards the warmer core of the body.
d) Muscles can also receive messages from the thermo-regulatory center of the brain (the hypothalamus) to
cause shivering. This increases heat production as respiration is an exothermic reaction in muscle cells.
e) Mitochondria can convert fat directly into heat energy, increasing the temperature of all cells in the body.
Brown fat is specialized for this purpose, and is abundant in newborns and animals that hibernate.

33.
a. Define the following
i) Ectothermy: Body temperature fluctuates with environmental temperature; body temperature changes;
body temperature controlled by behavior.
ii) Hibernation: the process of sleeping through the worst of the winter conditions.
iii) Aestivation: A physiological state characterized by slow metabolism and inactivity, which permits
survival during long periods of elevated temperature and diminished water supplies.
iv) Endothermy: the body temperature independent of environmental temperatures; heat source is
metabolism; regulation by physiological mechanism.
b. The adaptations of animals to living in cold climates

 Insulation. This is an effective way of reducing heat loss from the body. Insulation may be achieved by
trappimg a layer of air within fur, or a thick layer of subcutaneous fat. The colder is the climate, the
thicker the fur, and mammals living in very cold climates often have a very dense layer of fine fur next
to their bodies.
 Small surface area to volume ratio. Animals in colder climates tend to be more compact than those in
warmer climates, with smaller extremities such as ears and legs. This reduces the surface area over which
heat can be lost.
 Behavioural mechanisms. In colder regions, animals are often active during the day and when it is
warmer. Living in burrows under the snow means that mammals do not experience the extremely low
temperatures found on the snow surface. Huddling in groups, like penguins, also reduces heat loss.
 Hibernation. During periods of extreme cold, when food is relatively scarse or difficult to find because
of deep snow, animals such as bears may undergo a period of hibernation. This reduces the metabolic
rate 20-100 times below normal, reducing both food and oxygen consumption. The body temperature
falls, breathing and heart rate are reduced, and the animal seems to go into a deep sleep. During
hibernation, which may last several months, the animal uses up fat reserves laid down under the skin.
During the warmer part of the year, it has to eat huge amounts of food to build up new fat reserves to
use during the next cold period.

34.

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 a. Brush border/microvilli/highly folded to increase surface area; numerous mitochondria to release
energy for the active transport; Closeness of blood capillaries.
b. Glucose moved by active transport from filtrate into cell; diffuses through cell; movement of solutes
out of the tubule creates osmotic gradient; water moves by osmosis.

35.
a) If there is too much thyroxin, it inhibits/suppresses the action of the hypothalamus and the pituitary
gland; so less thyroxin is produced; if there is too little, the hypothalamus and the pituitary are not
suppressed; and thyroxin is produced.
b) Negative feedback.
c) When it affects two, it gives greater control/sensitivity.
d) In the bloodstream.

36. ADH makes the collecting ducts more permeable to water, allowing more water to be reabsorbed from tubular
fluid. When there is too little water in the blood, more ADH is secreted, leading to less water in the urine and
more water in the blood. This is an example of negative feedback because it reverses the direction of change
and brings conditions back to normal.
37. The millions of nephrons in the two kidneys each carry out the processes of filtration, reabsorption, and
secretion. In each nephron, filtration occurs in the glomerulus, as substances in blood are forced through
capillary walls and into Bowman’s capsule. From here, the substances, called filtrate, pass through the renal
tubule, where most reabsorption and secretion take place. These processes remove useful substances from
the tubular fluid and add other substances to the tubular fluid. Tubular fluid from the nephrons drains into
collecting ducts of the kidneys. In the collecting ducts, more water is reabsorbed to form the more
concentrated fluid called urine.
38. Diabetes insipidus and diabetes mellitus affect the kidneys in different ways. In diabetes insipidus, a
deficiency of ADH or a lack of response by the kidneys to ADH affects the kidneys’ ability to concentrate
urine. A person with the disease produces large quantities of very dilute urine. In diabetes mellitus, there is
too much glucose in the blood. The kidneys try to remove the excess glucose from the blood and excrete it
through more frequent urination. If glucose levels remain high, capillaries in the glomerulus can be damaged.
This may eventually lead to kidney failure.
39. Students can list and describe the functions of any three of the following parts of the lymphatic system: red
bone marrow, thymus, spleen, tonsils, lymphatic vessels, lymph, and/or lymph nodes. Sample answer: Red
bone marrow produces leukocytes; the thymus stores and matures T cells; lymph nodes filter out and
destroy pathogens in lymph.
40.
a. The proteins are too big to pass through the gromerulus.
b. Urea.
c. Because it is a metabolic waste that must be removed from the body. Urea is toxic when in high
concentration.
d. Diabetes mellitus. Because glucose is present in urine.
41.
a) Ammonia
b) Deamination
c) Ornithine cycle
d) Liver
e) Kidney
f) Uric acid
g) Uric acid is insoluble and requires little water to eliminate it from the body, whereas ammonia is
soluble and very toxic. It must be diluted many times but this is not a problem in a watery habitat.
42.

a)
i. 4
ii. 1
b) The U shaped part.
c) Glomerulus.
d) The pressure is higher in the efferent vessel than in the afferent vessel. This is because the afferent vessel
has wide lumen while that of the efferent vessel is narrow.

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 e) Proteins are too big to pass through the wall of the gromerulus. Amino acids are able to pass because
they are small.
f) The renal artery has a higher concentration of urea than the renal vein.
g) Kidneys and the liver.
43.
a) Stimuli: changes in concentration of blood glucose above and below the set point; receptors: the α and β
cells in the islets of Langerhans in the pancreas; effectors: the cells that change the glucose concentration
in the blood by absorbing it from the blood or release it into the blood; these are liver and muscle cells.
b) The blood glucose concentration fluctuates about a set point. In negative feedback, a change stimulates
a response that brings things back to normal. In the homeostatic control of blood glucose, an increase in
the concentration stimulates mechanisms that reduce the concentration, and a decrease in the
concentration stimulates mechanisms that increase it. These corrective actions restore the blood glucose
concentration to its set point.
44.
a) Hypothalamus
b) 1555 cm3 (or any answer within the range 1150 to 1160 cm3 or equivalent in dm3).
c) Any four from: water was absorbed into the blood; water increases the water potential of the plasma; any
effect of an increase in water potential of the plasma on, cells / tissues, e.g. water enters cells by osmosis /
cells will swell / decreases efficiency of reactions inside cells / cells may burst; osmoreceptors detect increase
in water potential; do not, secrete / release, ADH; collecting ducts remain impermeable to water; excess
water lost in urine; until water potential returns to, normal / set point.
d) (after absorption of dilute salt solution) no change in water potential of blood plasma; water and salt are not
lost in the urine, so must remain in the body; giving an increase in volume, of blood or body fluids; body
tolerates changes in blood volume, but not its water potential.
e) Homeostasis is the maintenance of, (near) constant internal conditions / internal conditions within narrow
limits. Negative feedback: a deviation from the set point; is detected by a receptor; a control centre instructs
effector to carry out a corrective action; to reverse the change / return factor to set point. Positive feedback:
any (small) deviation in a factor leads to an increase in the change (not a reversal).
45.
a) Glucose concentration may already be high; if person had eaten within 12 hours; effect of sudden increase
would not be seen / so there was a sudden increase; may already be a high concentration of insulin.
b) β cells secrete insulin; concentration of insulin increases over first hour after taking the glucose solution;
insulin concentration increases from 60 to 300 pmol dm−3; α cells do not secrete glucagon; glucagon
concentration, remains constant / decreases; from 42 to 36 pmol dm−3;
c) Insulin: stimulates, liver / muscle, cells; increase in uptake of glucose from the blood; more glucose
transporter molecules insert into the cell surface membrane of muscle cells (not liver cells); stimulates
enzymes; to increase conversion of glucose to glycogen; brings about a decrease in the blood glucose
concentration.
d) Blood glucose concentration decreases (below 4 mmol dm–3); insulin concentration, remains constant (at 60
pmol dm–3) / decreases (below 60 pmol dm–3); glucagon concentration increases (above 60 pmol dm–3);
glucose concentration then increases.
e) Membrane receptor activates the conversion of ATP to cyclic AMP; cyclic AMP activates glycogen
phosphorylase enzymes; glycogen phosphorylase catalyses the breakdown of glycogen to glucose; glucose
diffuses out of the (liver) cell into the blood.

Chapter 18: Respiration and gas exchange

1. Gas exchange is the process in which an organism absorbs from the environment gases necessary for its
cellular metabolism and expels gases that are products of this metabolism. Cellular respiration (aerobic or
anaerobic) is the chemical reaction in which organic molecules are degraded to make ATP molecules, the
main energy source for the metabolism.
2. All gas exchange surfaces have the following properties:
 A large surface area relative to the volume of the body. If human lungs were laid out flat they
would cover an area of between 50-100 m2, almost the size of a volley ball court. Your skin has an
area of about 2m2.

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  They are permeable to carbon dioxide and oxygen. This also makes them permeable to water,
which makes them moist.
 They are thin. In case of the gas exchange surface in human lungs, the distance gases have to diffuse
from the air to the blood is less than 15µm.
 They often have a ventilation mechanism to ensure a continuous supply of air or water to the gas
exchange surface.
 Larger animals have a circulation system to transport gases to and from the gas exchange surfaces.

3.
a) Floor of mouth lowered; pressure in the mouth decreases; water drawn in; operculum/gill cover closed;
gill cavity increases; floor of mouth raised; water drawn over the gills; mouth closes; operculum opens;
water forced out through operculum/gill cover.
b) Blood flows in opposite direction to water; diffusion gradient between oxygen in water and oxygen in
blood always present; more opportunity for oxygen to diffuse into blood.
4.
d) Nitrogen gas is not exchanged in the lungs.
e) Oxygen in alveolar air has been taken up into blood capillaries by diffusion; during expiration,
oxygen depleted air mixes with air which has not been in contact with the alveoli.
f) Water evaporates from the surfaces of the lungs.
5. In beings from the kingdom Animalia the gas exchange may occur either by diffusion, tracheal respiration,
cutaneous respiration, branchial respiration and pulmonary respiration.
6. Small animals whose tissues make direct contact or are very close to the environment, like cnidarians and
poriferans, make gas exchange by diffusion. Larger animals with cells without direct contact with the
environment or far from it need special gas transportation systems. In these animals the respiratory and the
circulatory systems play this role.
7. Insects and arachnids are the arthropod animals that make tracheal respiration. In the body surface of these
animals there are many orifices called spiracles that communicate with small tubules, the tracheae, through
which air penetrates and carbon dioxide is expelled. The tracheae ramify into tracheoles that reach all
tissues of the animal. In the circulatory system of insects the blood only transports nutrients; gases are
independently transported by the tracheal system.
8. Cutaneous respiration is not as simple as diffusion. In diffusion the gases diffuse directly between the
external environment and the cells. In cutaneous respiration molecular oxygen penetrates through the skin
and it is collected by the blood circulation that then distributes the gas to the tissues. Carbon dioxide is also
collected from the tissues by the blood and taken to the skin to be eliminated to the environment. So there
is important participation of blood in cutaneous respiration.
9. Terrestrial annelids and adult amphibians make cutaneous respiration (in amphibians there is also
pulmonary respiration). The thin skin and the need for living in moist surrounds are typical features of
these animals are.
10. Branchiae, also known as gills, are small portions of richly vascularized tissues internal or external to the
body and in direct contact with the surrounding water. The gills are organs that make gas exchange in
aquatic annelids, crustaceans, fishes and amphibian larvae (e.g., tadpoles).
11. Respiratory pigments are molecules present in the blood that bind to oxygen transporting it to the tissues.
In vertebrates the respiratory pigment is hemoglobin, reddish due to the iron of its composition. In
crustacean and arachnid arthropods and in some molluscs the respiratory pigment is hemocyanin, blue due
to the copper of its composition. Annelids have hemoglobin, hemorythrin and chlorocruorin as respiratory
pigments.
12. The left bronchus is more elevated than the right bronchus because of the position of the heart in the left
side of the chest, anterior and inferior to the left bronchus. Accidentally aspired objects are frequently
found in the right bronchus because the inferior angle between the trachea and this bronchus is lower than
the inferior angle between the trachea and the left bronchus since the left bronchus is more horizontalized.
Therefore aspired objects tend to fall in the right side (bronchus) and not in the left.
13. The diaphragm (exclusive of mammals) and the intercostal muscles can contract or relax varying the
volume of the thorax (the compartment where the lungs are located). The changing of the thorax volume
forces inhalation or expiration. When the thorax volume is increased an internal pressure lower than the
atmospheric pressure (external) is created and gases naturally enter the lungs. When the thorax volume is
lowered the internal pressure rises above the external pressure and the air is expelled from the lungs.
14. The gas exchange (entry of oxygen and exit of carbon dioxide) in the pulmonary alveoli occurs by simple
diffusion in favor of the partial pressure gradient. When the oxygen partial pressure in the inhaled air is

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 higher than the oxygen partial pressure of the capillaries of the alveoli the air diffuses to the circulatory
system. If the oxygen partial pressure in the air is lower (a rare situation since the blood that reaches the
alveoli is venous blood) the oxygen exits the circulatory system. The same is true for carbon dioxide.
15. The chemical equation of the chemical equilibrium of the formation of bicarbonate having as reagents
carbon dioxide and water is as follows: CO2 + H2O → H2CO3- → H+ + HCO3-. The reaction is catalyzed by
the enzyme carbonic anhydrase present in red blood cells.

16. Cells obtain energy for their metabolic reactions from the breaking of organic molecules with high
energetic content. This energy is mostly stored as ATP molecules.The process of obtaining energy in order
to produce ATP molecules is named cellular respiration.
17. Some cells that usually obtain energy from aerobic cellular respiration can carry out fermentation when
oxygen is not available. There are bacteria and fungi that under absence of oxygen use their anaerobic
metabolic capability for energetic supply. Muscle cells carry out fermentation too when oxygen is scarce.
18. In fermentation glucose (sugar) is degraded into pyruvic acid (each glucose molecule forms two pyruvic
acid molecules). In this process two molecules of ATP are produced. According to the type of fermentation,
pyruvic acid can produce ethanol and carbon dioxide (in alcoholic fermentation) or lactic acid (in lactic
fermentation). There are other varieties of fermentation in which pyruvic acid can generate acetic acid
(acetic fermentation)...
19. A typical fermentation process due to oxygen scarcity happens in the muscle tissue. Under intense use
muscles demand too much energy (ATP) and consume much more oxygen to produce that energy. High
consumption leads to oxygen scarcity and the muscle cells begin to make lactic fermentation trying to
satisfy their energetic needs. In this situation muscle pain, cramps and fatigue are due to the lactic acid
released by fermentation.
20. In fermentation from one glucose molecule two ATP molecules are produced. In aerobic respiration, a
much more productive process, from one glucose molecule 36 ATP molecules are made.
21. The three phases of aerobic cell respiration are glycolysis, Krebs cycle and respiratory chain (also known
as the electron transport chain).
22. Glycolysis, the first stage of the aerobic cell respiration, is a process in which glucose is degraded (broken)
to form two pyruvic acid molecules along with the formation of two ATP and two NADH. Glycolysis is a
complex reaction implying the formation of several intermediate molecules until pyruvic acid molecules
are made. Although two ATP molecules are consumed in the reaction, there is also production of four
molecules of ATP, thus a positive balance of two ATP molecules is obtained. Two NADH molecules are
also produced. In glycolysis the 6-carbon structure of glucose is broken and two organic chains of three
carbons each are made; these chains give birth to two pyruvic acid molecules.
23. Glycolysis happens in the cytosol and not within the mitochondria. Pyruvic acid molecules later enter
mitochondria to participate in the next phase of the aerobic cell respiration.

24. The pyruvic acid molecules made in cytosol by glycolysis enter into the mitochondria. Within the
mitochondria each pyruvic acid molecule is converted into one molecule of acetyl-CoA (acetyl coenzyme
A) with liberation of one carbon dioxide. The Krebs cycle (also known as citric acid cycle), the second
stage of aerobic respiration, then begins.
25. Each round of the Krebs cycle liberates two carbon dioxide molecules. At the end of the cycle all carbon
atoms from the original glucose molecule degraded in glycolysis are already liberated incorporated into
carbon dioxide molecules. That occurs because for each glucose two pyruvic acid molecules were made
by glycolysis. Each of these two pyruvic acids then is converted into acetyl CoA with liberation of one
carbon dioxide molecule (two in total). Since each of the two produced acetyl CoA cycles the Krebs cycle
once, from the initial glucose two rounds of the Krebs cycle is generated and so four other carbon dioxide
molecules are made. All of the six carbons of the glucose molecule are then incorporated into six carbon
dioxide molecules (two made during acetyl CoA formation and four during the two cycles of the Krebs
cycle).
26. Respiratory chain, or the electron transport chain, is performed by protein systems located in the inner
membrane of the mitochondria. Energized electrons of hydrogen atoms transported by NADH and FADH2
are the products of the preceding phases used in the respiratory chain.
27. Oxygen enters the aerobic respiration in its final phase, the respiratory chain. Oxygen serves as the final
acceptor of electrons. By accepting electrons from the last molecule in the electron transport chain,
oxygen allows additional electrons to pass along the chain. As a result, ATP can continue to be synthesized.
Oxygen also accepts the protons that were once part of the hydrogen atoms supplied by NADH and FAD 2.
By combining with both electrons and protons, oxygen forms water as shown in the following equation.

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 28.

Photosynthesis Cellular Respiration

Overall reaction 6CO2 +12H2O + sunlight→C6H12O6 + 6O2 + C6H12O6 + 6O2 → 6CO2 + 6H2O + 36ATP
6H2O
Reactants Carbon dioxide, water, sunlight Glucose, oxygen
Products Glucose Energy
By-products Oxygen Carbon dioxide and water
Cellular location Chloroplasts Cytoplasm, mitochondria
Energetics Requires energy Releases energy as ATP (exothermic
(endothermic reaction) reaction)
Time during During the day (in presence of sunlight During the day and night
which it takes energy) (all the time)
place
Chemical Light reactions and Calvin Cycle Glycolysis, Krebs Cycle, and Electron
pathways Transport System
Summary Sugar synthesized using the energy of the Energy released from the breakdown of sugar
sun (anabolic reaction) (catabolic reaction)
29. Fermentation and cellular respiration compared

ANAEROBIC RESPIRATION OR FERMENTATION AEROBIC RESPIRATION

C6H12O6 2CH3CH2OH+2CO2+ 2ATP C6H12O6+6O6 6H2O+6CO2+38 ATP

C6H12O6 2CH3CH(OH)CHOOH+ 2 ATP

-Doesn’t require oxygen -Requires oxygen.

-Produce a low quantity of energy (2ATP produced per glucose -Produces a big quantity of energy (38ATP
molecule). produced per glucose molecule).

-Incomplete oxidation of glucose. -complete oxidation of glucose.

-Uses the coenzyme NAD as electron acceptor in different redox -Uses the coenzyme NAD and FAD as electron
reaction of its stage. acceptor in different redox reaction of its stages.

- Consists of one stage in cytosol (glycolysis). - Consists of three stages: glycolysis in the cytosol
and the Krebs cycle and the electron transport chain
in mitochondrion.

-Last electron acceptor is pyruvic acid in lactic acid and -Last electron acceptor is an oxygen molecule.
acetaldehyde in alcoholic fermentation.

30.
a) 6 in glucose; 3 in glyceraldehydes 3-phosphate; 3 in pyruvate.
b) 2 ATP
c) To activate the glucose/to make the glucose more reactive/prevents the glucose from leaving the cell
since the membrane is impermeable to glucose-6-phosphate.
d) NAD; NAD+ picks up H+ and 2 electrons to form reduced NAD/NADH (may also be written as
NADH+H); reduced NAD carries hydrogen and electrons into mitochondrion.
e) Cytoplasm
f) i. taken into mitochondrion for Krebs cycle
ii. Stays in the cytoplasm and undergoes anaerobic respiration.
31.
a) Hemoglobin carries more oxygen than would be expected due to its high affinity; in condition of high
oxygen partial pressure, the hemoglobin picks up oxygen; oxygen is only released when the oxygen partial
pressure levels fall to a relatively low value.
b)

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 c) The presence of carbon dioxide causes the curve to shift to the right; reduces the affinity of hemoglobin for
oxygen; allows oxygen to be released easily; fetal hemoglobin has a higher affinity for oxygen than normal
hemoglobin; the curve shifts to the left; so the fetal hemoglobin can obtain oxygen from the maternal
hemoglobin.
32. The vital capacity is the volume E. The volume that cannot be measured by a spirometer is the volume D
also called the residual volume.
33. To generate ATP; re-oxidation of the reduced electron/hydrogen carriers; to oxidize hydrogen to form water;
on the inner membrane.
34. Formation of ATP from ADP and P; by a process of oxidation/oxidation of hydrogen and electron carriers;
forming water.
35.
a) Objective: to investigate energy (heat) production by respiring tissue/germinating seeds.
Observation: Flask A – rise in temperature; flask B- temperature remained the same.
b) Flask A – soaked seeds became active and started germinating, respiration took place and some heat
energy was produced. Flask B – dried seeds lacked moisture therefore no germination took place.
c) They prevent heat loss or heat gain.
d) As a control experiment.
36.
a) Boiling tube A – no colour change. Boiling tube B and C – colour changes from orange to purple.
b) The germinating bean seeds and the insect are respiring using oxygen and producing carbon dioxide.
The carbon dioxide changed the indicator colour to purple.
37.
Input(s) Output(s) Location in cell/organelle
Glycolysis Glucose, ADP, Pi, Pyruvate, ATP, NADH Cytoplasm
NAD+
Fermentation Pyruvate, NADH NAD+, ethanol and CO2 Cytoplasm
or lactic acid
Citric acid cycle AcetylcoA, NAD+, NADH, CO2, ATP, Mitochondrial matrix
ADP, Pi FADH
Respiratory chain NADH, FADH, O2 ATP, NAD+, FAD+, Inner mitochondrial
H2O membrane
38. 1→ b; 2 → e; 3 → i; 4 → h, 5 → d; 6 → f; 7 → g ; 8 → c; 9 → a.
39. (a) – (vi); (b) – (viii); (c) – (vii); (d) – (ix); (e) – (i); (f) – (ii); (g) – (iii); (h) – (v); (i) – (iv).
40.
a) Carbon dioxide.
b) The lungs.
c) Oxygen is carried in the RBC as oxyhemoglobin. In the tissues, carbon dioxide combines with water to
form carbonic acid. This ionizes to hydrogen carbonate ions and hydrogen ions. The raised hydrogen
ion concentration (increased acidity) causes decomposition of oxyhemoglobin to release oxygen.
d) The movement of chloride ions preserves the electrical charge on either side of the membrane/replaces
the negative hydrogen carbonate ions diffusing out.
41.
a) 96.5%
b) 1.25 cm3
c) 24.0%

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 d) 0.31 cm3
42.
a) 195 cm3
b) 25 cm3
43.
a) Fewer alveoli; larger air spaces; fewer capillaries; scar tissue in, bronchioles / bronchi; few / no, cilia; few /
no, goblet cells; enlarged mucous glands; enlarged smooth muscle; may be pre-cancerous / cancerous cells;
tumor / bronchial carcinoma;
b)
i. Difficulty breathing / breathlessness; wheezing; tiredness; not able to do (much) exercise.
ii. Small(er) surface area for gas exchange; less oxygen absorbed; poor oxygenation of the blood; bronchi
/ bronchioles / airways, blocked by mucus; increased resistance to flow of air.
44.
a) P – ciliated epithelial cell; R – goblet cell.
b) S – Cilium / cilia; T – mitochondrion; U – Golgi body; W – nucleolus.
c) T / mitochondria, provide, energy / ATP; for movement of cilia;
d) U / Golgi apparatus, packages proteins into vesicles; for secretion.
e) Award 2 marks for the correct answer. If answer is incorrect, award 1 mark for the correct working.
Length of cell P on page = 73 mm = 73 000 μm
f) Magnification = ×750
g) Actual length = 73 000 ÷ 750 = 97 μm
h) Cell P – cilia beat / move back and forth; move mucus; upwards / towards throat; cell R – secretes
mucus; mucus traps, dust / bacteria / viruses / pollen; prevents entry to, alveoli / gas exchange
surface.
45.
a) Oxygen diffuses down its concentration gradient; from alveolar air into red blood cells; carbon dioxide
diffuses down its concentration gradient; from, red blood cells / plasma, to alveolar air; across epithelial cells
of alveolus and endothelium of capillary;
b) Breathing / ventilation; introduces, fresh air / atmospheric air; removes, stale air / air rich in carbon dioxide;
c) Increase depth of breathing; rate of breathing; expansion of alveoli to give a larger surface area; diameter of
airways.
46.
a) Tar stimulates, goblet cells / mucous glands, to secrete more mucus; paralyses / destroys, cilia; mucus not
moved up the, bronchioles / bronchi / trachea / airways; mucus accumulates in the airways; bacteria multiply
within the airways; (leads to) chronic bronchitis; tar contains, carcinogens / named carcinogen; e.g.
benzpyrene (tar) settles on bronchial, epithelial cells / epithelium; mutation(s) / change to DNA; growth of
tumor; bronchial carcinoma / lung cancer;
b) Nicotine: increases heart rate; increases blood pressure; increases chance of blood clotting / promotes
thrombosis; decreased flow of blood to, extremities / fingers / toes.
Carbon monoxide: combines (irreversibly) with hemoglobin; forms carboxyhemoglobin; reduces oxygen
carrying capacity of, hemoglobin / blood; damages lining of arteries; promotes atherosclerosis.

47.
ATP used ATP produced Net gain in ATP
Glycolysis -2 +4 +2
Link reaction 0 0 0
Krebs cycle 0 +2 +2
Oxidative phosphorylation 0 +34 +34
Total -2 +40 +38
48.
a) Lipid has more hydrogen atoms per molecule than does a carbohydrate; most energy liberated in aerobic
respiration comes from the oxidation of hydrogen to water.

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 49. X is pyruvate; Y is lactate and Z is ethanol (or ethyl alcohol).
50.
a) Cyclic photophosphorylation: electron emitted by chlorophyll of photosystem I returns to chlorophyll
by a series of carriers;
Non cyclic photophosphorylation: electron emitted by chlorophyll of photosystem II does not return to
that chlorophyll (but is absorbed by photosystem I and electron emitted by photosystem I is absorbed by
NADP). The electron lost by chlorophyll is replaced by the electron from the photolysis of water.
b) Photophosphorylation: synthesis of ATP using light energy in photosynthesis in a chloroplast; oxidative
phosphorylation: synthesis of ATP using energy released from the electron transport chain in aerobic
respiration in a mitochondrion.
c) NAD: hydrogen carrier in respiration; NADP: hydrogen carrier in photosynthesis.

Chapter 19: Transport in animals

1. In animals that do not present the circulatory system the transport of substances occurs by cell to cell by
diffusion. The blood is a fundamental means of substance transport for larger animals since in these animals
there are tissues distant from each other and from the environment thus making diffusion impossible.
2. The circulatory systems can be classified into open circulatory system and closed circulatory system.
3. Open circulatory system is the one in which blood does not circulate only inside blood vessels but it also falls
in cavities that irrigate tissues. In the open circulatory system the blood pressure is low and generally the
blood (called hemolymph) has low cellularity. Arthropods, molluscs (the cephalopods are exception) and
protochordates have open circulatory system.
4. A closed circulatory system is one in which blood circulates only inside blood vessels. For this reason the
blood pressure is higher in animals with closed circulatory system. The cellularity of the blood is also higher
with many specific blood cells. The closed circulatory system is a feature of annelids, cephalopod molluscs
and vertebrates.
5. The closed circulatory system is more efficient. Since blood circulates only inside blood vessels it can do it
with more pressure reaching farther distances between the organs where hematosis happens and the
peripheral tissues. In addition the circulatory speed also heightens making possible more oxygen supply to
great consuming tissues, like the muscle tissues that then can perform faster movements. Animals with an
open circulatory system (with the exception of insects that do gas exchange independently from the
circulation) are generally slower and have a low metabolic rate.

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 6. In insects the circulatory system is open but this system does not participate in the gas exchange process and
in oxygen supply to the tissues. Gases go in and out through the independent tracheal system that allows
direct contact of cells with the ambient air. Therefore an insect can supply the great oxygen demand of its
fast-beating wing muscles even having open circulatory system.
7. Systole and diastole are the two stages into which the cardiac cycle is divided. Systole is the stage when the
contraction of ventricular muscle fibers occurs and the ventricles are emptied. Diastole is the stage of the
cardiac cycle when the ventricular muscle fibers distend and the ventricles are filled with blood.
8. The valves of the venous system are structures inside the veins that permit blood to flow only in the normal
way (from the tissues to the heart) and forbid it to return in the reverse way in favor of gravity. The valves
close when the pressure of the fluid column above (after, regarding normal flux) is higher than the fluid
pressure before them. Valves are thus fundamental for the returning of blood to the heart.
9. The ventricle walls are thicker than the atrium walls since ventricles are structures responsible for the
pumping of the blood to the lungs or tissues. The muscular work of the ventricles is harder and their muscle
fibers develop more. The left ventricle is more muscular than the right ventricle because pumping blood to
the lungs (the right ventricle task) is easier (needs less pressure) than pumping blood to the other tissues of
the body (the left ventricle task).
10. The vena cava are either of two large veins that debouch into the right atrium. The superior vena cava drains
all blood that comes from the head, the superior limbs, the neck and the superior portion of the trunk. The
inferior vena cava carries blood drained from the inferior portion of the trunk and the inferior limbs.
11. The heart is made of striated cardiac muscle tissue. The heart muscle is called the myocardium and it is
oxygenated and nutrified by the coronary arteries. The coronary arteries come from the base of the aorta and
ramify around the heart penetrating the myocardium.
12. Hemoglobin “likes” carbon monoxide (CO) much more than it likes oxygen. When there is carbon monoxide
in the inhaled air it binds to hemoglobin forming carboxyhemoglobin by occupying the binding site where
oxygen would bind. Due to the higher hemoglobin affinity for carbon monoxide thus (e.g., in intoxication
from car exhausts) there is no oxygen transport and the individual undergoes hypoxia, loses conscience,
inhales more carbon monoxide and may even die. Intoxication by carbon monoxide is an important cause of
death in fires and in closed garages.
13. Double closed circulation is that in which the blood circulates through two associated and parallel vascular
systems: one that carries blood to and takes blood from the peripheral tissues (the systemic circulation) and
the other that carries blood to and takes blood from the tissues that perform gas exchange with the
environment, e.g, the lungs (pulmonary circulation). Double circulation occurs in amphibians, reptiles, birds
and mammals. Simple closed circulation, or simple circulation, is the one in which the tissues that perform
gas exchange are associated in series with the systemic circulation, as in fishes.
14. Complete circulation is that in which there is no mixture of venous blood and arterial blood. Simple
circulation is that in which the blood circulates only in one circuit (as opposed to the double circulation that
have two circuits, the systemic circulation and the pulmonary circulation). In fishes the circulatory system is
simple and complete.
15. Heart contraction is independent from neuronal stimulus (although it can be modulated by the autonomous
nervous system). In the heart there are pacemaker cells that trigger by themselves the action potentials that
begin the muscle contraction. These cells are concentrated at two special points of the heart: the sinoatrial
node (SA node) located in the superior portion of the right atrium and the atrioventricular node (AV node)
located near the interatrial septum. The action potentials generated by depolarization of the SA node cells
propagate cell to cell throughout the atria producing the atrial contraction. The atrial depolarization also
propagates to the AV node that then transmits the electric impulse to the ventricles through specialized
conduction bundles of the interventricular septum (the bundle of His) and then to the Purkinje fibers of the
ventricle walls causing ventricular contraction. (The atrial contraction precedes the ventricular contraction
for blood to fill the ventricles before the ventricular contraction.) The repolarization of the SA node makes
the atria relax and then the ventricles relax too.
16. A is the pulmonary vein; B is the aorta; C is the inferior vena cava; D is the hepatic portal vein.
17.

a) A is the aorta; B is the semi lunar valve or pulmonary valve; C is the atrioventricular valve or mitral
valve; D is right ventricle; D is the posterior vena cava.
b) To prevent the backflow of blood.

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 18. Cardiac muscle is self exciting/has its own internal rhythm of excitation and contraction; does not require
stimulus by nerves.
19. Right ventricle →pulmonary artery →pulmonary capillaries (exchange of gases) → pulmonary veins → left
atrium. The purpose of this pathway is to exchange the carbon dioxide with oxygen. Oxygen is taken in the
circulation while carbon dioxide diffuses to the outside.
20. The blood from the digestive organs and spleen flows through the portal vein to the liver before returning to
the heart. Purpose: the liver stores some nutrients or regulates their blood levels and detoxifies potential
poisons before blood enters the rest of peripheral circulation.
21. The heart is a double pump: The right side of the heart receives deoxygenated blood from the body and pumps
it to the lungs; the left side of the heart receives oxygenated blood from the lungs and pumps it to the body.
Both sides of the heart work simultaneously. The right atrium → right ventricle → pulmonary arteries →
lungs → pulmonary veins → left atrium → left ventricle → aorta → different parts of the body → vena cavae
→the right atrium.
22.
a) A - Atrio-ventricular valve closes when pressure in ventricle rises above pressure in the atrium; B –
semi-lunar/aortic valve opens when pressure in the ventricle exceeds pressure in the aorta/artery; C –
semi-lunar/aortic valve closes when pressure in aorta exceeds pressure in the ventricle; D – atrio-
ventricular valves open when ventricular pressure falls below that of the atrium.
b) 60/0.8=75 beats per minute.
23. G – A – C – J– H–D–K–B– I – E– F.
24.

i. Aorta
ii. Vena cava
a) The blood in veins flows towards the heart whereas in arteries blood flows away of the heart. In arteries the
blood flows under high pressure whereas in veins it under low pressure.
b) Oxygenated blood.
c) The wall of the left ventricle is thicker than that of the right ventricle.
d) AV valves and semilunar valves.
e) Capillaries are one cell thick; capillaries are permeable.
25.
a) Arteries have a thick layer of smooth muscle; arteries have a narrow lumen.
b) The blood in arteries flows away of the heart.
c) Kidneys receive more blood from the renal artery than the liver which receives the blood from the hepatic
artery. The kidneys are involved in the removing metabolic wastes from the blood.
d) Pulmonary arteries.
e) Because arteries take the blood which is pumped directly from the heart and this blood is under higher
pressure. The blood in veins is under lower pressure after it has passed in capillaries.
f) Eggs contain all the nutrients required for the growth of an organism and the cholesterol it contains is
necessary in the making of cell membranes and in the formation of steroid hormones which are also essential
in the normal development of a human.

26.

a) The fish has a single circulatory system, whereas the mammal has a double circulatory system. In
the fish, blood leaves the heart and travels to the gills, where it picks up oxygen, before continuing
around the body. In the mammal, the blood returns to the heart after picking up oxygen at the lungs,
and is then pumped around the body.
b) Oxygenated blood can be pumped around the body at a higher pressure, and therefore faster, in a
mammal than in a fish, because pressure is lost in the capillaries in the gills. This can provide a more
efficient oxygen supply to mammalian cells than to fish cells.

27.

a) Protein synthesis – no. There is no DNA, so no mRNA can be transcribed.

b) Cell division – no. There are no chromosomes, so mitosis cannot occur, nor are there centrosomes
for spindle formation.

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 c) Lipid synthesis – no. This occurs on the smooth endoplasmic reticulum, and there is none.
d) Active transport – yes. This occurs across the cell surface membrane, and can be fuelled by ATP
produced by anaerobic respiration.
28.
a) Protein in tissue fluid comes from the cells making up the tissues, many of which secrete proteins.
b) If plasma protein concentrations are low, water will not be drawn back into capillaries from tissue
fluid. Albumin in the blood plasma raises its solute concentration (lowers its water potential), thus
helping to draw water back from the tissue fluid into capillaries. If albumin could diffuse out of
capillaries into tissue fluid, more water would accumulate in the tissue fluid. (This is called oedema.)
29. Less oxygen would enter the blood by diffusion, and therefore less oxygen would be carried to the body cells.
The percentage saturation of hemoglobin will be only about 30%.
30. At high altitude, the percentage saturation of the hemoglobin is relatively low. If the number of red blood
cells is increased, then the number of hemoglobin molecules is also increased. Even though the percentage
saturation of the hemoglobin is low, the fact that there is more of it can increase the actual quantity of oxygen
carried in the blood.
31. Spending a length of time at high altitude stimulates the body to produce more red blood cells. When the
athlete returns to sea level, these ‘extra’ red blood cells remain in the body for some time and can supply
extra oxygen to muscles, enabling them to work harder and for longer than they would otherwise be able to
do.
32.
a) Reference to diffusion; down concentration gradient; through the wall of a capillary.
b) Lower pressure; lower concentration of oxygen; lower concentration of glucose; lower water potential; lower
concentration of proteins / amino acids / fatty acids / other named nutrient; higher concentration of urea.
c)
i. Carbonic anhydrase.
ii. Hydrogencarbonate ions diffuse out of red blood cells; (hydrogencarbonate ions) are transported in
solution in blood plasma; conversion of CO2 to hydrogencarbonate reduces concentration of CO2 in
the blood; which maintains diffusion gradient for CO2 to diffuse into the blood from respiring
tissues.
d)
i. 73%, 62%.
ii. Presence of carbon dioxide causes affinity of hemoglobin for oxygen to decrease; hydrogen ions
(from the dissociation of H2CO3) bind with hemoglobin; cause change in shape of Hb molecule.
iii. Bohr effect
iv. Causes more release of oxygen (than if this effect did not occur); in respiring tissues; where demand
for oxygen is high / where production of carbon dioxide is high.
33.
a) Blood goes through the heart twice on one complete circuit of the body.
b) Has more smooth muscle / elastic tissue; to withstand higher (blood) pressure; to withstand fluctuating
(blood) pressure;
c) To prevent blood flowing into the capillary bed / to divert blood to other capillary beds;
d) Permeable walls / reference to pores in walls; allow water / dissolved ions / dissolved substances (from
plasma) to pass out; do not allow large protein molecules / cells to pass out; reference to greater
hydrostatic pressure inside capillary than in tissue fluid.
e) (plasma contains) more proteins; has lower water potential; has lower, carbon dioxide / HCO3-
concentration; has greater glucose concentration; has greater oxygen concentration.
f) Lymph.

34.

a) About 0.75 seconds;

b) 60 ÷ 0.75 = 80 beats per minute
c) For c, d, e, f and g, see figure below.

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 35.
a) Right ventricle; pulmonary vein
b) They open to allow blood to flow from atria to ventricles; they close during ventricular systole /
when ventricles contract; reference to closure being caused by differences in pressure in atria and
ventricles.

Chapter 20: Heterotrophic nutrition

1. Digestion is the breaking down of larger organic molecules obtained from the diet, e.g. carbohydrates, fats,
proteins, into smaller ones, like glucose, fatty acids, glycerol and amino acids.
2. Intracellular digestion is that in which the breaking down of macromolecules takes place within the cell.
Extracellular digestion is that in which macromolecules are broken down in places outside the cell (in the
extracellular space, in the surrounds, in the lumen of digestive tubes, etc.). The advent of extracellular
digestion in evolution allowed organisms to benefit from a greater variety of food. The breaking down of
larger molecules into smaller ones outside the cell permitted the use of other foods than those that, due the
size of their molecules, could not be interiorized by diffusion, phagocytosis or pinocytosis.
3. A variety of specialized cells and tissues appeared with extracellular digestion to provide enzymes and special
structures for the breaking down of dietary macromolecules. This phenomenon allowed other cells to be
liberated for other tasks and differentiations while benefiting from nutrients distributed through the
circulation
4. Animals with an incomplete digestive system are those in which the digestive tube has only one opening
(cnidarians, platyhelminthes). Animals with a complete digestive system are those in which the digestive
tube has two openings, mouth and anus (all other animal phyla, with the exception of poriferans, that do not
have any digestive tube).In a nimals with incomplete digestive tubes the digestion is mixed, it begins in the
extracellular space and finishes in the intracellular space. In animals with complete digestive systems
extracellular digestion within the digestive tube predominates.
5. The salivary hydrolase is known as salivary amylase, or ptyalin. Ptyalin digests carbohydrates breaking starch
and glycogen, glucose polymers, into maltose (a glucose disaccharide) and dextrin.

6. When food is swallowed the swallow reflex is activated and the larynx elevates and closes to avoid portions
of the food bolus entering the trachea causing aspiration of strange material to the bronchi.
7. The normal pH of the gastric juice is around 2. So it is an acid pH. It is necessary for the gastric pH to be
kept acid for the activation of pepsinogen (a proenzyme secreted by the gastric chief cells) into pepsin, the
digestive enzyme that acts only under low pH. This pH level is attained by the secretion of hydrochloric acid
(HCl) by the parietal cells.
8. The gastric epithelium is mucus secretory, i.e., it produces mucus. The mucus covers the stomach wall
preventing corrosion by the gastric juice.
9. The small intestine is divided into three portions: duodenum, jejunum and ileum.
10. Bile, an emulsifier liquid, is made by the liver and later stored within the gallbladder and released in the
duodenum. Bile is composed of bile salts, cholesterol and bile pigments. Bile salts are detergents, amphiphilic

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 molecules, i.e., molecules with a polar water-soluble portion and a non-polar fat-soluble portion. This feature
allows bile salts to enclose fats inside water-soluble micelles in a process called emulsification for them to
be in contact with intestinal lipases, enzymes that break fats into simpler fatty acids and glycerol.
11. This organ makes digestive enzymes that digest proteins (proteases), lipids (lipases) and carbohydrates
(pancreatic amylases). Other digestive enzymes, like carboxipeptidase, ribonuclease and deoxyribonuclease
are also secreted by the pancreas.
12. The pancreas secretes trypsinogen that, undergoing action of the enzyme enterokinase secreted by the
duodenum, is transformed into trypsin. Trypsin in its turn catalyzes the activation of pancreatic
chymotrypsinogen into chymotrypsin. Trypsin and chymotrypsin are proteases that break proteins into
smaller peptides. The smaller peptides are then broken into amino acids by the enzyme carboxipeptidase
(also secreted by the pancreas in a zymogen form and activated by trypsin) helped by the enzyme
aminopeptidase made in the intestinal mucous membrane.
13. Besides making bile for release in the duodenum, the liver has other digestive functions. The venous network
that absorbs nutrients from the guts, called mesenteric circulation, drains its blood content almost entirely to
the hepatic portal vein. This vein irrigates the liver with absorbed material from the digestion. So the liver
has the functions of storing, processing and inactivating nutrients. Glucose is polymerized into glycogen in
the liver; this organ also stores many vitamins and the iron absorbed in the intestine. Some important
metabolic molecules, like albumin and clotting factors, are made in the liver from amino acids of the diet. In
the liver ingested toxic substances, like alcohol and drugs, are inactivated too.
14. Entering the duodenum the chyme meets the pancreatic juice under a pH of approximately 8.5. The
neutralization of the chyme acidity is necessary to keep adequate pH level for the functioning of the digestive
enzymes that act in the duodenum. Without the neutralization of the chyme acidity the mucous membrane of
the intestine would be injured. When stimulated by the chyme acidity the duodenum makes a hormone called
secretin. Secretin stimulates the pancreas to release the pancreatic juice and also the gallbladder to expel bile
in the duodenum. The pancreatic secretion, rich in bicarbonate ions, is released in the duodenum and
neutralizes the chyme acidity; this acidity is also neutralized by the secretion of bile in the duodenal lumen.
15. The human digestive secretions are: saliva, gastric juice, bile, pancreatic juice and enteric juice. Among these
secretions only the bile does not contain digestive enzymes.
16. The stomach and the pancreas make zymogens of the proteases pepsin, chymotrypsin and trypsin and these
zymogens are released into the gastric or duodenal lumen for activation. This happens to prevent the digestion
of these organs' (stomach and pancreas) own cells and tissues by the active form of the enzymes. So the
production of zymogens is a protective strategy against the natural effects of the proteolytic enzymes.
17. Evolution tried to solve this problem in two ways. The simplest is the long and tubular shape of the bowels
(approximately eight meters in extension), making possible that numerous small intestine loops fold closely.
More efficient solutions are the intestinal villi and the microvilli of the mucosal membrane cells. The
intestinal wall is not smooth. The mucous membrane, together with its submucosa, projects inside the gut
lumen like glove fingers forming invaginations and villi that multiply the available surface for absorption. In
addition the epithelial cells that cover these villi have themselves numerous hairlike projections called
microvilli on the external face (lumen face) of their plasma membrane. The absorptive area of the intestines
is thus increased hundreds of times with these solutions. In the jejunum and ileum there are folds that have
the function of increasing the absorption surface too.
18. Most part of water, vitamins and mineral ions are absorbed by the small intestine. The large intestine,
however, is responsible for the reabsorption of nearly 10% of the ingested water, an important amount that
gives consistency to feces.
19. Monosaccharides, amino acids, mineral salts and water are absorbed by the intestinal epithelium and
collected by capillary vessels of the intestinal villi. From the capillaries, nutrients go to the mesenteric
circulation, a system of vessels that drains the intestinal loops. The blood of the mesenteric circulation is
drained to the portal hepatic vein and some nutrients are processed by the liver. From the liver, nutrients are
gathered by the hepatic veins that discharge its blood content into the inferior vena cava. Blood from the
inferior vena cava then gains the right chambers of the heart and is pumped to the lungs for oxygenation.
From the lungs the blood then returns to the heart where it is pumped to the tissues distributing nutrients and
oxygen.
20. Triglycerides emulsified by the bile within micelles suffer the action of lipases that break them into fatty
acids and glycerol. Fatty acids, glycerol and cholesterol are absorbed by the intestinal mucosa. In the interior
of the mucosal cells fatty acids and glycerol form again triglycerides that together with cholesterol and
phospholipids are packed in small vesicles covered by proteins and called chylomicrons. The chylomicrons
are released in minuscule lymphatic vessels not in blood vessels and they gain the lymphatic circulation. So

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 the lymphatic system plays an important role in the absorption of lipids. The lymphatic circulation drains its
content to the venous blood circulation.
21. Some types of plant fibers are not absorbed by the intestine but play an important role in the functioning of
the organ. They retain water inside the bowels and thus contribute to the softening of the fecal bolus. A softer
fecal bolus is easier to be eliminated during defecation. People that eat less dietary fiber may suffer from hard
stools and constipation.
22. Bacteria that live inside the gut have great importance in digestion. Some polysaccharides like cellulose,
hemicellulose and pectin are not digested by the digestive enzymes secreted by the body; instead, they are
broken by enzymes released by bacteria of the gastrointestinal tract. The intestinal bacterial flora also makes
vital substances for the functioning of the bowels facilitating or blocking the absorption of nutrients and
stimulating or reducing peristalsis. Some gut bacteria are the main source of vitamin K for the body and so
they are essential for the blood clotting process. In the intestinal flora there are utile but also potentially
harmful bacteria. It is estimated that more than 100 trillion bacteria live in a human gut. Some bacteria are
useful too because they compete with other species preventing excessive proliferation of these bacteria.
23. The hormones that participate in the regulation of digestion are gastrin, secretin, cholecystokin and
enterogastrone.
24. The presence of food in the stomach stimulates the secretion of gastrin that in its turn triggers the releasing
of the gastric juice.
25. Secretin is made in the duodenum. The chyme acidity causes the duodenum to release this hormone that in
its turn stimulates the secretion of the pancreatic juice.

26. The fat level of the chyme detected in the duodenum stimulates the secretion of cholecystokin (CCK). CCK
acts by stimulating the secretion of the pancreatic juice also, and the releasing of bile by the gallbladder.
27. The food ingested by cows and other ruminant animals passes first within two compartments of the digestive
tube called the rumen and the reticulum. Within them the food suffers the action of digestive enzymes
released by microorganisms that live there in mutualist ecological interaction. In the reticulum the food is
divided in some food bolus too. After passing the reticulum the food (cud) is regurgitated to the mouth to be
again chewed and swallowed in a process called rumination. The digesting food then enters the omasum
where it is mechanically mixed. After that the food goes to the abomasum, the organ where the chemical
digestion takes place. After leaving the abomasum (the true stomach) the food bolus gains the intestine.

28. The purpose of mechanical digestion is to break food into smaller pieces to increase the surface area for the
action of enzymes. Examples: The teeth break down the food; the stomach churns the food…
The purpose of chemical digestion is to break down complex organics into simpler organics and inorganics.
This is done with the help of enzymes and each enzyme is specific for the food it will digest. Examples:
Salivary amylase converts starch into maltose; lipases convert fats into glycerol and fatty acids…

29.

a) A is the epithelial cell of the ileum ; B is the lacteal and C is the blood vessel,
b) B is involved in the absorption of fats; C is involved in the absorption of other nutrients other than fats
(glucose, aminoacids, water, vitamins, and mineral salts).
c) Has a large surface area; microvilli to increase surface area further; network of capillaries carries away
digested foods; lacteals transport fats; blood supply maintains steep concentration gradient to maximise
diffusion; thin epithelium reduces distance for diffusion.

30.

a) All the protein-digesting enzymes are produced in inactive form.

b) Endopeptidase hydrolyses peptide bonds within the protein; produces shorter of polypeptides;
exopeptidases break off terminal amino acids; releases amino acids;

Endopeptidases released first to break the protein into shorter lengths; producing more terminal amino
acids for exopeptidases to work on.

c)

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 Enzyme Site of Site of action Substrate product
production
Rennin Stomach stomach Caseinogen Casein

Trypsin Pancreas Small intestine Proteins Small peptides

Lipases Pancreas Small intestine Fats Glycerol and

fatty acids

31. The presence of microvilli that increase their surface area and a big number of mitochondria that are necessary
to produce the energy required for the active transport of substances.
32. This arrangement has two advantages: the hepatic portal system gives the liver “first claim” to these nutrients
before the blood is distributed to the rest of the body (regulation of nutrients). Secondly, it also allows the
blood to be cleansed of bacteria and toxins picked up from the intestines (detoxification). From the liver, the
blood reaches the inferior vena cava by the hepatic vein and then goes to the heart to be distributed in other
parts of our body.
33.
a) The blood glucose in the hepatic portal vein increases after a meal/varying amounts are absorbed from
the gut.
The excess glucose is converted to glycogen in the liver (or if there is insufficient blood glucose; then
stores of glycogen in the liver are broken down).
b) Glucose is produced from molecules other than glycogen such as lipids/proteins/aminoacids.
c) The starch has to be digested; therefore there is a slower uptake of sugar/no rapid rise in the blood
sugar

34.
a. Peristalsis
b. The esophagus is a muscular tube that takes food from mouth to the stomach.
c. Epiglottis
d.
i. Pepsin and HCl.
ii. There is no amylase in the stomach or amylase from the mouth is deactivated by the acidic
environment of the stomach. Amylase works at basic pH.
e. Duodenum
i. Lactose
ii. Maltase converts maltose into glucose.

Chapter 21: Reproduction and human development

1. Gametes are cells specialized in sexual reproduction. They contain half of the maximum number of
chromosomes of the species and unite with another gamete giving birth to a zygote with double of the
number of chromosomes of the gametic cells. In humans gametes are formed by meiosis; the male gametes
are the sperm cells and the female gametes are the egg cells.
2. Meiosis is the type of cell division that allows sexual reproduction since it reduces to a half the number
of chromosomes of the species making possible the combination of two gametes to form a new individual.
3. The cells that form gametes are the germ cells as opposed to the somatic cells. The ploidy (number of
chromosomes) of the germ cells is the same as the somatic cells (only during the formation of gametes
meiosis occurs and the number of chromosomes is reduced to half).
4. Gonads are the organs that produce gametes. They contain the germ cells that undergo division and
generate gametes. In males the gonads are the testicles. In females the gonads are the ovaries.
5. The acrosome is a structure that contains a great number of digestive enzymes, it is located in the anterior
end of the sperm cell and it is formed by the union of Golgi apparatus vesicles. The function of the
acrosome is to release its enzymes when the sperm cell meets the egg cell to break the external covering
of the female gamete thus making fecundation possible.

6.

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 7. The flagellum of the sperm cell is made by the centrioles that migrate to the region posterior to the nucleus.
Its function is to promote locomotion towards the egg cell.
8. The main differences between spermatogenesis and oogenesis.
Spermatogenesis Oogenesis

Each primary spermatocyte develops into 4 Each primary oocyte develops into only one ovum
spermatozoa.
There is no formation of polar bodies There is formation of up to 3 bodies
Takes a relatively shorter time to complete Takes a longer time to complete
It is a continuous process Stops during menopause
All spermatogonia develop into primary Only few oogonia develop into primary oocytes
spermatocytes. and others degenerate.

9. Ovulation is the releasing of the female gamete from the ovary. Ovulation is a periodical event that
occurs during each menstrual cycle. Considering as the first day of the menstrual cycle the day when
menses begins, the ovulation occurs around the 14th day when the concentrations of the hormones LH
and FSH reach high levels.
10. The sperm cell that reaches the egg cell triggers the acrosome reaction, a process in which hydrolytic
enzymes of the acrosome are released on the external surface of the zona pellucida (the protective layer
that surrounds the egg cell). A portion of this layer is digested by the acrosomal enzymes allowing the
sperm cell to reach the plasma membrane of the egg cell carrying out fecundation. At the moment that
the sperm cell makes contact with the egg cell membrane a chemical alteration of this membrane occurs.
Enzymes secreted by exocytosis (cortical reaction) make the zona pellucida unable to bind to other sperm
cells (zonal reaction) and other male gametes cannot enter the egg cell.
11. The female gametes are big cells full of vitellus (nutritive material). The male gametes are small, mobile
and agile flagellate cells. Those features are related to their respective biological functions. While the
female gametes have the basic functions of receiving the sperm cell nucleus and of storing nutrients for
the zygote, the male gametes have the function of active movement towards the egg cell.
12. These secretions along with sperm cells from the testicles form the semen. The secretions have the
function of nourishing the sperm cells and serving them as a fluid means of propagation. The basic pH
of the seminal fluid also neutralizes the acid secretions of the vagina allowing the survival of sperm cells
in the vaginal environment after copulation.

13. In males the sexual activity is regulated by the endocrine glands hypophysis (pituitary), adrenals and
gonads (testicles). The FSH (follicle-stimulating hormone) secreted by the adenohypophysis acts upon
the testicles stimulating the spermatogenesis. The LH (luteinizing hormone), another adenohypophyseal
hormone, stimulates the production of testosterone by the testicles too. Testosterone, whose production
intensifies after the beginning of puberty, acts in several organs of the body and it is responsible for the
appearing of the male secondary sex characteristics (beard, body hair, deep voice, increase of the muscle
and osseous mass, maturation of genitalia, etc.) Testosterone also stimulates spermatogenesis.

14. The endocrine glands that secrete hormones involved in the menstrual cycle are the hypophysis
(pituitary) and the ovaries. The hormones from adenohypophysis are FSH (follicle-stimulating hormone)
and LH (luteinizing hormone) and the hormones from the ovaries are estrogen and progesterone.

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 15. By convention the menstrual cycle begins at the day that menses begins. (Menses is the endometrial
hemorrhage excreted through the vaginal canal.) At these days the hormones FSH, LH, estrogens and
progesterone are in low concentration.
16. The follicles that are growing after menses secrete estrogen. These hormones act upon the uterus
stimulating the thickening of the endometrium (the internal mucosa of the uterus).
17. The follicle that released the ovum suffers the action of LH and is transformed into the corpus luteum.
The corpus luteum is very important because it secretes estrogen and progesterone. These hormones
prepare the uterine mucosa, also known as endometrium, for nidation (implantation of the zygote in the
uterine wall) and embryonic development since they stimulate the thickening of the mucous tissue,
increase its vascularity and make the appearing of uterine glycogen-producing glands.
18. The menstrual cycle is divided into two main phases: the follicular (or menstrual) phase and the luteal
(or secretory) phase. The menstrual phase begins at the first day of menses and lasts until ovulation
(around the 14th day). The luteal phase begins after ovulation and ends when menses begins (around the
28th day).

19. Although this is not a rule, to be effective fecundation in general must occur within about 24 hours after
ovulation (that occurs around the 14th day of the menstrual cycle). Fecundation may occur even if
copulation took place up to 3 days before ovulation since the male gametes remain viable for about 72
hours within the female reproductive system. The fertile period of the women however is considered the
period from 3 days before ovulation to 2 days after ovulation.
20. The placenta besides being the organ through which the exchange of substances between the mother and
the fetus is done also has the function of secreting estrogen and progesterone to keep a high level of these
hormones during pregnancy. (The placenta still secretes other hormones like human placental lactogen
that act similarly to the hypophyseal hormones that regulate reproduction, and HCG, human chorionic
gonadotropin.)
21. Parthenogenesis is the reproduction or formation of a new individual from the egg cell but without
fecundation by the male gamete. According to the species, individuals born by parthenogenesis may be
male or female, or of any sex. In bees the drone (the single male bee) is haploid and born by
parthenogenesis while the females (queen and workers) are diploid.
22. Gastrulation is the process through which a portion of the blastula wall undergoes invagination inside
the blastocele, forming a tube called archenteron (primitive intestine). The cells of the inner side of the
tube form the endoderm (germ layer) and the cells of the outer side form the ectoderm (another germ
layer). It is the beginning of the tissue differentiation in embryonic development.
23. Twins are simultaneously generated (within the mother’s uterus) offspring. Twins classify according to
zygosity as monozygotic or as dizygotic twins. Monozygotic twins, also known as identical twins, are
those originated from one single fertilized ovum (therefore from one single zygote); monozygotic twins
are genetically identical, i.e., they have identical genotypes and are necessarily of the same sex.
Dizygotic twins, also known as fraternal twins, are those generated from two different ova fecundated
by two different sperm cells; so they are not genetically identical and they are not necessarily of the same
sex.
24.
a) A: Seminal glands B: Prostate C: Boulblourethral glands (Cowper’s glands) D: Vas deferens E:Testis
E: Penis
b) B: Makes some secretions that make the semen. E: produces the sperm and male hormones.
c) Sperm production best at 35°C; so held outside body where it is cooler; (remember body temperature is
37°C).

25. Testis, epidydimis, vas deferens, ejaculatory duct, urethra.

26.
a) Oestrogens and progesterone
b) LH
c) LH
d) FSH and LH
e) FSH
27.

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 a) Provides large surface area for exchange; maternal blood flows close to the fetal blood; provides a
minimal barrier for the diffusion and active transport of substances.
b) Blood pressure is higher; this would damage foetal blood vessels.
c) Entering: water, oxygen; glucose, amino acids, lipids, mineral salts, vitamins, antibodies, hormones.
Leaving: urea, metabolic waste, carbon dioxide
d) Forms a cushion to protect foetus from knocks/bumps; keeps temperature constant; allows the foetus
to move.
28.
a) Between day 1 and day 5.
b) Pituitary gland.
c) Release of the egg from the ovary.
d) Estrogens and progesterone.
e) Day 14. Because of the increasing level of LH.
29. Reproductive organs develop along either male or female lines; lungs develop the ability to exchange gas;
overall body size increases.

30. An embryo is generally more susceptible than a fetus to damage by toxins in the mother’s blood because
the embryo is undergoing organogenesis. Any disruption of normal development is likely to have a greater
impact on the organism at this stage than later in pregnancy, when the organs are already formed.
31. The umbilical cord is cut before a newborn has started to breath on its own because this helps to trigger
the infant’s first breath. After the cord is cut, carbon dioxide quickly builds up in the baby’s blood. This
stimulates the brain to trigger breathing.
32. A: Spermatogonium, 2n; B: primary spermatocyte, 2n; C: secondary spermatocyte, n; D: spermatid, n; E:
spermatozoan, n.
33.

Chapter 22: Support and movement

1. Cell: osteoblast; Tissue: compact bone; Organ: Femur.

2. The appendicular skeleton is made up of the arm and leg bones, the scapula, the clavicle, and the pelvic
bones.

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 3. Any four of the following: Structural Support of the Body, Protection of Internal Organs, Attachment of the
Muscles, Movement of the Body, Production of Blood Cells, Storage of Minerals.
4. There are three types of joints: immovable (cranial bones), partly movable (between the vertebrae), and
synovial (knee, elbow, hip).
5. Skeletal muscle: attached to the skeleton; Cardiac muscle: in the heart; Smooth muscle: internal organs such
as urinary bladder and intestines
6. Skeletal muscle
7. Aerobic metabolism produces more ATP molecules than anaerobic metabolism. About 36 ATP molecules
are produced from every molecule of glucose in aerobic metabolism, but only two molecules of ATP are
produced in anaerobic metabolism.
8. A sacromere is made up of overlapping filaments of actin and myosin. Actin filaments are attached to
structures called Z lines.
9. In the sarcomere there are organized actin and myosin blocks. Troponin and tropomyosin also appear
associated to actin. The actin molecules when activated by calcium ions liberated in the proximities of the
sarcomere are pulled by myosin molecules. This interaction between actin and myosin shortens the myofibrils
originating the phenomenon of muscle contraction.
10. In the muscle cells calcium ions are stored within the sarcoplasmic reticulum. When a motor neuron emits
stimulus for the muscle contraction neurotransmitters called acetylcholine are released in the neuromuscular
junction and the sarcolemma is excited. The excitation is conduced to the sarcoplasmic reticulum that then
realeases calcium ions into the sarcomeres. In the sarcomeres the calcium ions bind to troponin molecules
associated to actin activating myosin binding sites of actin. The myosin, then able to bind to actin, pulls this
protein and the sarcomere shortens. The summation of simultaneous contraction of sarcomeres and myofibrils
constitutes the muscle contraction. During muscle relaxation the calcium ions return back to the sarcoplasmic
reticulum. For myosin to bind to actin, and thus for the contraction to occur, hydrolysis of one ATP molecule
is necessary. During relaxation the return of calcium ions to the sarcoplasmic reticulum is an active process
that spends ATP too. So both muscle contraction and relaxation are energy-spending processes.
11. Myoglobin is a pigment similar to hemoglobin and present in muscle fibers. Myoglobin has a great affinity
for oxygen. It keeps oxygen bound and releases the gas under strenuous muscle work. So myoglobin acts as
an oxygen reserve for the muscle cell.

12. If oxygen from hemoglobin or myoglobin is not enough for the energy supply of the muscle cell the cell then
begins to do lactic fermentation in an attempt to compensate the deficiency. The lactic fermentation releases
lactic acid and this substance causes muscle fatigue and predisposes the muscles to cramps.
13. In the compact bone haversian systems are present while in the spongy bone, no haversian system are present
and also contains the red bone marrow present.
14. In the cavities in spongy bone of some bones like the ribs and vertebrae. The red bone marrow produces
red blood cells, platelets, and the five kinds of white blood cells.
15.

a) Synovial fluid
b) Joint capsule
c) Articular cartilage
d) Synovial membrane

16. Hemoglobin and myoglobin. They have an affinity for oxygen; they are respiratory pigments.
17. The breastbone.
18.
a. Sarcolemma
b. Motor end plate or axon terminal
c. Synaptic cleft
19. The sarcoplasmic reticulum or the endoplasmic reticulum of muscle cells surrounds the sarcomere. The
sarcoplasmic reticulum is a reservoir for calcium ions (Ca2+), which are essential for the contraction process.
20. Tendons attach muscles to bone. A tendon merges with the fascia of a muscle and the periosteum of a bone;
all are made of fibrous connective tissue.
21.
a. Synergistic muscles
b. Antagonistic muscles

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 22.

23.
a) A: H zone; B: A band; C: sarcomere; D: I band; E: Z line.
b)
i. Myosin.
ii. Main component: Actin; accessory proteins: tropomyosin and troponin.
c) (i) ATP binds to the myosin head causes a conformational change of the myosin head. This allows the
myosin head to bind to actin binding site forming actomyosin cross-bridge.
(ii) The calcium ions bind to troponin, moving troponin and tropomyosin to one side, exposing the myosin
binding site in the actin filament.
e) (i) Sarcomere shortens. (ii) A bands do not change in length. (iii) I bands shorten. (iv) H zone
shortens.
24.
a) K: A band; L: I band; M: Z line / disc.
b) 5; the myofibrils are separated from each other by mitochondria.
c) Glycogen granules are broken down to provide glucose for respiration; mitochondria, carry out aerobic
respiration / provide much ATP (for muscle contraction).
d) There is a very wide I band; in the I band there is no overlap between thick and thin filaments; in contracted
muscle the thin filaments would be closer together giving a thin I band.
e) Distance = 54 mm (accept 53 mm) = 54,000 µm
𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑜𝑛 𝑡ℎ𝑒 𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑛 𝑚𝑖𝑐𝑟𝑜𝑔𝑟𝑎𝑝ℎ 54000
𝐿𝑒𝑛𝑔𝑡ℎ = = = 2.7µ𝑚
𝑚𝑎𝑔𝑛𝑖𝑓𝑖𝑐𝑎𝑡𝑖𝑜𝑛 20000
25.
a) The diagram shows (TS) of sarcomere / myofibril / thick and thin filaments; X shows, actin / thin filaments
alone; see diagram below. Y shows myosin / thick filaments alone; see diagram below. Z is overlap between
thick and thin filaments; see diagram below. X is I band; Z is (overlap region of) A band; Y is H zone; each
thick filament is surrounded by six thin filaments. The thick filaments form crossbridges with all of them.

b) If contracted muscle, then, no / little, I band and H zone; so there would be no section like X and no section
like Y; thin filaments are brought closer together by action of myosin heads; thick and thin filaments slide
over each other during contraction.
c) Role of calcium ions at the end of a motor neurone: at, neuromuscular junction / motor end plate; voltage-
gated channel proteins for calcium ions open when impulse arrives; calcium ions enter / AW, when action
potential arrives; stimulates vesicles to move towards / fuse with pre-synaptic membrane; role of calcium
ions in muscle: impulse / action potential in sarcolemma / T-tubules, stimulates release of calcium ions from
sarcoplasmic reticulum; calcium ions bind to troponin; stimulates movement of tropomyosin; myosin

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 binding sites on thin filaments exposed; cross-bridges form; when no action potential calcium ions pumped
back into sarcoplasmic reticulum.

Chapter 23: Genetics

Note on genetic problems:

 Sometimes genetics questions tell you which letters to use. If they do not, make sure you start off with a key
to the meaning of the letters used in your answer. Always write down all the stages, including parents,
gametes and resulting offspring. If the question refers to genotype, it requires you to work out the genetic
composition of the offspring. If the question asks for phenotype, you must indicate the appearance of the
individual based on their genotype. Often you are asked to work out the ratio of phenotypes. This is a figure
as 3:1. Always make it clear to which phenotype the ratios refer, for example 3 purple-stemmed: 1 green-
stemmed.
 It is important when filling in a Punnet square with the full 16 combinations that you write down the parental
gametes in the correct order. Start with the two dominant alleles, then one dominant and one recessive and
finally two recessive alleles, like AB, Ab, aB, ab. If you get the correct order, you can check your workings
out easily. Looking on a well filled Punnet square, you see that the bottom right hand corner always has the
one double recessive genotype. It is surrounded by the three dominant/recessive combinations. All the rest
are the 9 dominant genotypes.
 For pedigree problems, use the tips below to determine what kind of trait is involved.
 If parents without the trait have offspring with the trait, the trait must be recessive and the parents both
carriers.
 If the trait is seen in every generation, it is most likely dominant (see the next possibility, though).
 If both parents have the trait, then in order for it to be recessive, all offspring must show the trait. If
some offspring do not show the trait, it is caused by a dominant allele.
 To determine the likely genotype of a certain individual in a pedigree, first label the genotypes of all the
family members you can. Even if some of the genotypes are incomplete, label what you do know. For
example, if an individual has the dominant phenotype, the genotype must be AA or Aa. Try different
possibilities to see which fits the results.

1. A gene is a sequence of DNA nucleotides that codifies the production of a protein.

2. A chromosome is a DNA molecule. A chromosome may contain several different genes and also DNA
portions that are not genes.
3. Gene locus (locus means place) is the location of a gene in a chromosome, i.e., the position of the gene in a
DNA molecule.
4. Diploid individuals have paired chromosomes. For example in humans there are 23 pairs of chromosomes
totaling 46 chromosomes. Each pair comprehends homologous chromosomes, one chromosome from the
father and another from the mother, both of them containing information related to the production of the same
proteins (with the exception of the sex chromosomes, which are partially heterologous). So in the diploid
individual it is said that each gene has two alleles, one in each chromosome of the homologous pair.
5. A phenotype is every observable characteristic of a living being conditioned by its genes.
6. The law of segregation states that a pair of alleles is randomly segregated during the formation of gametes.
During meiosis, homologous chromosomes move apart and are randomly separated into different gametes.
Therefore, each gamete has an equal chance of receiving any one of the alleles.
7. The law of independent assortment states that the inheritance of one trait will not affect the inheritance of
another. Mendel concluded that different traits are inherited independently of each other, so there is no
relation, for example, between seed color and seed shape.
8. A heterozygote and homozygote for the dominant allele of a trait will appear to have the same phenotype.
An organism exhibiting the recessive phenotype will always be homozygous recessive.
9. The Punnett square for a dihybrid cross is twice as large as that for a monohybrid cross because the alleles
for two characteristics are tracked, instead of one.
10. Mendel observed a ratio of 9:3:3:1. Nine of 16 had round, yellow seeds and had the following genotypes:
RRYY, RrYy, RRYy, RrYY. Three of 16 had round green seeds (genotypes RRyy, Rryy). Three of 16 had

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 wrinkled yellow seeds (genotypes rrYy, rrYY), and one of 16 was homozygous recessive with green wrinkled
seeds (genotype rryy).
The Punnet square is represented below:

11. Students should indicate males by squares and females by circles within the pedigree. The pedigree should
be three generations in length and the symbol of the individuals with a cleft chin should be shaded.

12. Sample answer: I do not agree. Type AO blood does not exist. The i allele is recessive, not codominant, as is
the case in type AB blood. The A and B allele are codominant. The ii alleles are expressed only when
homozygous.
13. Mendelian inheritance does not apply to more complex forms of inheritance. In the cases of incomplete
dominance and codominance, there is not one allele that is entirely dominant or an allele that is entirely
recessive as is described by Mendelian inheritance.
14.
a) 20
b) 1
c) 19
15.
a) 63
b) The gametes cannot be formed because there is an odd number of chromosomes. They cannot be
separated in meiosis I during the separation of homologous chromosomes.
16.
a) Linked genes are genes located on the same chromosome whereas sex linked genes are genes located on
sex chromosomes.
b) The two alleles segregate during Anaphase I.
c) The number of different combinations of chromosomes in the pollen gamete cells is calculated using the
formula 2n, where n is the haploid number of chromosomes. In Crocus, since 2n = 6, n = 3. Therefore
the number of combinations = 23 = 8.
d)

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 e) Mutagens are substances which cause mutations. Examples: UV rays, asbestos, some chemicals such as
colchicines…..
17.
a) The Rhesus factor is a kind of antigen present on the red blood cells of some people.
b) People without the Rhesus are not able to receive the blood containing the Rhesus factor. These people
will produce antibodies against the Rhesus factor and those antibodies will agglutinate the antigens.
c) The child will suffer from the haemolytic disease of the newborn.
18. The F1 phenotypes show that purple flower and short stem are dormant and red flower and long stem are recessive.
The approximate ratio of 1:1:1:1 in a dihybrid cross suggests that the two genes controlling the characteristics of flower color
and stem length are not linked and the four alleles are situated on different pairs of chromosomes.

Let P represents purple flower

p represents red flower
S represents short stem
s represents long stem
Since the parental stocks were both homozygous for both characters, the F1 genotypes must be PpSs
Test cross: PpSs x ppss

Gametes PS Ps pS ps

ps PpSs Ppss ppSs ppss

Offspring genotype: PpSs, Ppss, ppSs and ppss.

Offspring phenotvpe: 1 purple flower short stem, 1 purple flower long stem, 1 red flower short stem and one red flower long
stem
19.
a) 10 purple/hairly: 3.2 purple/hairless: 1 green/hairly: 1green/hairless.
b) 9:3:3:1; as it is a dihybrid cross/two genes are involved.
c) Too few plants; some of the seeds did not germinate; some plants died before their characteristics become
apparent; incorrect interpretation of results; some plants did not express their characteristics.
d) 3 purple hairly and 1 green hairless.
20.
a)
i. ALLELES: different forms of the same gene.
ii. LOCUS: position of a gene on a chromosome.
iii. AUTOSOME: Any chromosome except the sex chromosomes. Genes on the autosomes are
inherited without regard to the sex of the individual.
b) Mendel’s first law: the law of segregation: the characteristics of a diploid organism are controlled by
alleles occurring in pairs of such alleles. Only one can be carried in a single gamete.
Mendel’s second law: the law of independent assortment: anyone of a pair of characteristics may
combine with either one of another pair.
c) Key: B is black and G is ginger
XBXB × XGY
Gametes XB × XG or Y
F1 cats XBXG, XBY;

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 Phenotypes tortoiseshell female and black male
21.
a) Purple stems
b) Key: P represents purple-stemmed and p represents green-stemmed
Parents PP x pp
Gametes Pxp
F1 Pp all purple stemmed
F1 parents Pp x Pp
Gametes P or p x P or p
F2 PP, Pp, Pp, pp
Phenotypic ratio 3 purple: 1 green
22.
a) Key: T is tall, t is short, W is white and w is red.
Parental genotypes: TTWW x ttww
b) TtWw; tall and white
c) Parents: TtWw x ttww
Gametes: TW, Tw, tW, tw and tw

Gametes TW Tw tW tw

tw TtWw Ttww ttWw Ttww

Tall/white Tall/red Short/white Short/red

Ratio: 1 Tall/white: 1 tall/red: 1 short/white: 1 short/red

d) F2: TtWw x TtWw
Gametes: TW, Tw, tW, tw
Punnet square
Gametes TW Tw tW tw

TW TTWW TTWw TtWW TtWw

Tall/white Tall/white Tall/white Tall/white
Tw TTWw TTww TtWw Ttww
Tall/white Tall/red Tall/white Tall/red
tW TtWW TtWw ttWW ttWw
Tall/white Tall/white Short/white Short/white
Tw TtWw Ttww ttWw ttww
Tall/white Tall/red Short/white Short/red
Ratio of phenotypes: 9 Tall/White: 3 Tall/Red: 3 Short White: 1 short/Red
Genotypes: 1 TTWW: 2 TTWw: 1 TTww: 2 TtWW: 4 TtWw: 2Ttww: 1 ttWW:
2 ttWw: 1 ttww
Note: The genotypes can be seen in specific locations as seen below in this table where every genotype
has a specific colour.
Gametes TW Tw tW tw

TW TTWW TTWw TtWW TtWw

Tall/white Tall/white Tall/white Tall/white
Tw TTWw TTww TtWw Ttww
Tall/white Tall/red Tall/white Tall/red
tW TtWW TtWw ttWW ttWw
Tall/white Tall/white Short/white Short/white
Tw TtWw Ttww ttWw ttww
Tall/white Tall/red Short/white Short/red
23.
a) DdHh; dark and short-haired.
b)

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 Gametes DH Dh dH dh

DH DDHH DDHh DdHH DdHh

Dark/short Dark/short Dark/short Dark/short
Dh DDHh DDhh DdHh Ddhh
Dark/short Dark/long Dark/short Dark/long
dH DdHH DdHh ddHH ddHh
Dark/short Dark/short Albino/short Albino/short
dh DdHh Ddhh ddHh ddhh
Dark/short Dark/long Albino/short albino/long
Phenotypic ratio: 9 dark/short: 3 dark/long: 3 albino/short: 1 albino/long.
24.
a) Key: R is red flower, r is white
Parents RR x rr
Gametes R x r
F1 Rr all pink
b) F1 parents Rr x Rr
Gametes R or r and R or r
F2 genotypes: RR, Rr, Rr, rr
Phenotypes 1 red: 2 pink: 1 white

25. The allele for this disorder is dominant. Individuals 1 and 2 are heterozygous, and individual 3 is homozygous
for the recessive (normal) allele.
26. A: XCXc; B: XCXc; C: XCXc; D: XcXc; E:XcY
27.
a) Genes found on the same chromosome; inherited together; may be separated by crossing-over/chiasmata.
b) 3:1; because the two genes would be inherited as one/inheritance the same as for a monohybrid cross;
9:3:3:1; because the genes would be inherited separately/would be a normal dihybrid cross.
28. Recessive; George = Aa; Arlene = aa; Sandra = AA or Aa; Tom = aa; Sam = Aa; Wilma = aa; Ann = Aa;
Michael = Aa; Daniel = Aa; Alan = aa; Tina = AA or Aa, Carla = aa; Christopher = AA or Aa.
29.
a) If short black hair appeared in the F1 phenotypes, then short hair must be dominant to long hair and
black hair must be dominant to white.
b) Let B represents black hair
b represents white hair.
S represents short hair
s represents long hair
F1 phenotypes short black hair
F1 genotypes SsBb
F2 SsBb x SsBb
Gametes: SB, Sb, sB, sb
Gametes SB Sb sB sb

SB SSBB SSBb SsBB SsBb

Short/Black Short/Black Short/Black Short/Black
Sb SSBb SSbb SsBB Ssbb
Short/Black Short/White Short/Black Short/White
sB SsBB SsBb ssBB ssBb
Short/Black Short/Black Long/Black Long/Black
sb SsBb Ssbb ssBb Ssbb
Short/Black Short/White Long/Black Long/White
F2 phenotypes: 9 short/black hair: 3 short/white hair: 3 long/black hair: 1 long/white hair.
The F2 genotypes are shown in the Punnet square.
30. Let R,r and S,s represent two allelomorphic pairs of genes controlling flower colour
Parental phenotypes Purple x purple
Parental genotypes RrSs x RrSs
Gametes RS, Rs, rS, rs

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 Gametes RS Rs rS rs

RS RRSS RRSs RrSS RrSs

Purple Purple Purple Purple
Rs RRSs RRss RrSs Rrss
Purple White Purple White
rS RrSS RrSs rrSS rrSs
Purple Purple White White
rs RrSs Rrss rrSs Rrss
Purple White White White
Offspring phenotypic ratio = 9 purple: 7 white

31.
a) Parental genotype: PPrr x ppRR
b) F1 PpRr; all walnut
c) Parental genotypes PpRr x PpRr

Gametes PR Pr pR pr

PR PPRR PPRr PpRR PpRr

Walnut Walnut Walnut Walnut
Pr PPRr PPrr PpRR Pprr
Walnut Pea Walnut Pea
pR PpRR PpRr ppRR ppRr
Walnut Walnut Rose Rose
pr PpRr Pprr ppRr pprr
Walnut Pea Rose single
Phenotypic ratio 9 walnut: 3 pea: 3 rose: 1 single
32. The man has blood group B so he can have 2 genotypes: BB or BO
The woman of blood group AB has only one genotype AB
Possible crossings
First case: Parents BO x AB
Gametes B, O and A, B
Offsprings
Gametes A B
B AB BB
O AO BO
The possible groups of their offspring are A, B and AB
Second case: Parents BB x AB
Gametes B and A, B
Offsprings
Gametes A B
B AB BB
B AB BB
The possible groups of their offspring are AB and B
The blood group their children will not have is blood group O.
33. These three processes create unique combinations of genes. Independent assortment is the process of random
segregation and assortment of chromosomes during meiosis to produce a gamete with a mixture of the
organism's maternal and paternal chromosomes. Crossing-over is the process by which two nonhomologous
chromosomes exchange some portion of their DNA during meiosis. As crossing-over occurs between every
nonhomologous pair of chromosomes, it is not possible to have two resulting gametes with the same
combination of chromosomes. Random fertilization refers to the fact that a zygote forms between two random
gametes, greatly increasing the number of possible genetic outcomes.
34.
a) Possible genotypes
i. CC, Ccch, Cch, Cc.
ii. cchcch, cchch, cchc.
iii. chch, chc.
iv. cc.

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 b)
cch ch

C C cch C ch

ch cch ch ch ch

Genotypes: 25 % C cch, 25 % C ch, 25 % cch ch and 25 % ch ch.

Phenotypes: 50 % Dark gray-coated rabbits, 25 % Chinchilla rabbits and 25 % Himalayan rabbits.

c) Yes. For example if the chinchilla rabbit has this genotype c chc and the white rabbit has a single
genotype which is cc. From this crossing 50 % of the offspring will be white.
d) It is not possible because chinchilla is dominant to himalayan and to white. Every genotype that has the
allele for chinchilla in presence of another for Himalayan or white will be chinchilla.
e) cchc and chc.

35.
a)
i. The cerebellum.
ii. The pituitary gland, the hypothalamus and the pineal gland.
iii. The meninges
b) Let R be the allele of the disorder and r be the normal allele
The genotypes of the parents are: XrXR and XrY
Xr Y
r
X Xr X r X rY
R r R
X XX XRY
The genotype of the son Silvio is XrY and that of the daughters (Miriam, Helga and Sheryl) is X r Xr.
c) Because the sons get only the Y chromosome from their fathers while the X chromosome comes from their
mothers. The allele of the disorder is located on the X chromosome which comes from their mothers.
36. Parental genotypes: AaBb and aabb
Gametes: AB, Ab, aB, ab and ab
Punnet square

37.
a) CcWw; all are colored starchy.
b) Gametes are CW, Cw, cW, cw and cw.
Gametes CW Cw cW cw

cw CcWw Ccww ccWw ccww

Genotypes are CcWw, Ccww, ccWw and ccww; 1 colored starchy: 1 colored waxy: 1 colorless starchy:
1 colorless waxy.

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 c) Linkage / genes are on the same chromosome / genes do not assort independently; colored starchy and
colorless waxy are parentals.
38. CRCW x CRCW
Punnet square
CR CW
R R
C R
C C CRCW
R W
C W
C C CWCW
Phenotypes: 25 % white-flowered plants; 25 % red-flowered plants and 50 % pink-flowered plants.

39.
a) A gene / trait / allele carried on a sex chromosome / X or Y.
b) Recessive. Evidence from the pedigree (e.g. 2nd generation-2 and -3 do not have the condition but have
one child who does).
c) XaY (where a = condition)
d) XAXa or XAXA where A = normal and a = condition.

40.
a) gene mutation / substitution
b) Val / valine;
c) Sickle cell anaemia.

41.
a) Many amino acids have more than one triplet code; so sequence of amino acids is unchanged;
b) adding or deleting three nucleotides may add or remove the coding for one amino acid; this may not
affect the final shape of the protein; adding or deleting one nucleotide affects the arrangement of all
subsequent triplets; this ‘frameshift’ may alter the coding of all amino acids following the addition or
deletion; a triplet may be altered to a stop signal.

Chapter 24: Ecology

1. A species is a set of living beings able to cross among themselves generating fertile offspring.
2. A population is a set of individuals of the same species found in a given place in a given time.
3. An ecological niche is a set of peculiar activities, resources and strategies that a species explores to survive
and reproduce. An habitat is the place where the species lives to explore its ecological niche. In other words
it can be said that the habitat is the “address” of the species and the ecological niche is the “profession” of
the species.
4. Biotic factors are living beings (plants, animals and microorganisms) that are part of a given environment.
5. Abiotic factors are the nonliving elements that constitute a given environment, like light, temperature,
minerals, water, gases, atmospheric pressure, etc.
6. An ecosystem is a system composed of biotic and abiotic factors in interaction.
7. A biosphere is a set of all of the ecosystems of the planet.
8. Autotrophic beings are those that can produce their own food, i.e., that make organic material from inorganic
compounds. Heterotrophic beings are those that need to incorporate organic material to nourish them.
Therefore heterotrophs depend on the production of the autotrophs.
9. Phytoplankton and zooplankton are divisions of the plankton. The phytoplankton comprises the autotrophic
floating beings: algae and cyanobacteria. The zooplankton is formed by the heterotrophic planktonic beings:
protozoans, small crustaceans, cnidarians, larvae, etc.
10. A large number of photosynthetic beings is found in the plankton, i.e., in the surface of aquatic ecosystems.
This is because light is abundant on the surface.
11. The energy flux along a food chain is always unidirectional, from the producers to the decomposers.
12. The chain concept is a theoretical model to study the energy flux in ecosystems. Actually in an ecosystem
the organisms are part of several interconnected food chains, forming a food web. Therefore the chain is a
theoretical linear sequence and the web is a more realistic representation of nature in which the food chains
interconnect forming a web.
13. The three types of trophic pyramids studied in Ecology are the numeric pyramid, the biomass pyramid and
the energy pyramid. Generally the variable dimension of the pyramid is the width, and the height is always

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 the same for each represented strata of living beings. The width therefore represents the number of
individuals, or the total mass of these individuals or the available energy in each trophic level.

14. Since the numeric pyramid represents the quantity of individuals in each trophic level of the food chain,
inferior trophic levels with less individuals than the superior trophic levels may exist. For example, a single
tree can serve as food to millions of insects.
15. Biomass pyramids represent the sum of the masses of the individuals that participate in each trophic level of
a food chain.
16. Energy pyramids represent the amount of available energy in each trophic level of the food chain.
17. Three different types of consumers are herbivores, carnivores, and omnivores. Herbivores, such as cows, eat
producers such as plants. Carnivores, such as lions, eat animals. Omnivores, such as humans, eat both plants
and animals.
18. Decomposers break down dead organisms and other organic wastes. They convert the organic remains to
carbon dioxide and elements needed by living organisms.
19. Energy is transferred between trophic levels in a food chain when producers take in energy to make organic
compounds, consumers eat producers or other consumers, and decomposers break down dead organisms and
other organic wastes. However, only about 10 percent of the energy is transferred from one trophic level to
the next higher level.
20. Only 10 percent of the kilocalories at each trophic level are transferred to the next higher trophic level. So,
of the 1,000,000 kcal in producers, just 1,000 kcal can be transferred all the way up the food chain to tertiary
consumers. This is supported by the following calculations: 1,000,000 kcal × 0.1 = 100,000 kcal (primary
consumers); 100,000 kcal × 0.1 = 10,000 kcal (secondary consumers); and 10,000 kcal × 0.1 = 1,000 kcal
(tertiary consumers).
21. Food chains should include, in the following sequence: plant (producer) → herbivore (primary consumer) →
carnivore (secondary consumer) → carnivore (tertiary consumer). Sample answer: grass → grasshopper →
rat → snake.
22.
a) i) EUTROPHICATION: An increase in nutrient levels in a body of water, often followed by an
increase in plant or algae production.
ii) CARRYING CAPACITY: the maximum population of an organism that can be supported by
the environment.
iii) CLIMAX COMMUNITY: the final and most productive group of organisms an environment
can support.
b) Density-dependent factor: Factor which has the potential to control population size because its effects
are proportional to population density. Density-independent factor: Factor which may affect
population size or density but cannot control it.
c) i) Producer: Grasses. Tertiary consumer: Toads, snakes and birds.
ii) The amount of light energy converted to chemical energy (organic compounds) by autotrophs during
a given time period is an ecosystem’s primary production. The amount of chemical energy in
consumer’s food that is converted to their own biomass during a given time period is called the
secondary production of the ecosystem.
iii. The amount of energy transferred from one trophic level to the next is low; some parts of the
organisms are not eaten or are not digested.
23.

24. The reproductive rate of the plant plankton is greater than the animal plankton; this is sufficient to support a
much greater biomass of animal plankton.

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 25. Gross is total quantity of energy captured by plant in photosynthesis/rate at which photosynthetic products
build up;
Net is quantity of energy available to the primary consumers/net gain of dry mass stored in plant after
respiration;
Net = gross productivity – losses due to respiration.

26. The diagram below shows the flow of energy through the organisms at different levels in a habitat.
a) The percentage of solar energy falling on the habitat and is trapped by the producers is

b) The energy value A = 120 units – 96 units = 24 units.

B = 300 units + 120 units + 180 units = 600 units
c) In this habitat the primary consumers are small invertebrates such as snails, earthworms and insects. The
3rd consumers are foxes and hawks.
j. The proportion of total energy consumption used in respiration by the first consumers is

The proportion of total energy consumption used in respiration by the third consumers is

Consumers who use the greatest proportion of energy are the third consumers.
ii. What explains the difference in the calculated proportions; for primary consumers they have a
low metabolic rate. These animals are ectothermic which means that they do not produce the
heat from their bodies; they rely on the heat from the surrounding. For the tertiary consumers,
these animals have a high metabolic rate and are endothermic which means that they spend a
lot of energy. The energy is also lost when these animals are hunting in order to find their food.
iii. There are only 5 feeding levels in this habitat. There can’t be a sixth feeding level because the energy transfer
between trophic levels is low. The available energy in the fifth trophic level cannot support another trophic
level.
27. Renewable resources are replenished by natural processes as fast as (or faster than) humans consume them,
while nonrenewable resources are not regenerated or restored on a time scale comparative to consumption.
The Laws of Energy state that energy flows downhill and gets used up (is not renewable) whereas matter is
conserved (is renewable) under most conditions on Earth. Our view of resources is skewed toward our own
rate of use relative to supply, rather than these natural laws.
28.
Renewable Reasoning

Copper Can be recycled

Iron Can be recycled

Oxygen Recycled by ecosystems

Sunlight Infinite amount relative to use

F r e s h water Hydrologic cycle recycles

Wood Reforestation can grow new trees

Wool Sheep can produce new coats

Nonrenewable Reasoning

Coal Limited resource

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 Natural Gas Limited resource

Nuclear Power Nuclear fuel is limited (depending on use)

Fresh Water Pollution and overdrafting can exhaust resources

29.
a) The percentage of the incident energy which becomes available as the net primary production (NPP) of
green plants is

b) Two of:
 Light is reflected/not absorbed by the plant leaf.
 Energy is used to evaporate water /heat the plant.
 Energy is released by the respiration of the plant.
 Light energy is transmitted.
 Photosynthesis/biochemical processes are inefficient.
c) 1800 KJ is transferred to caterpillars but only 100 KJ is transferred to birds/ there is 5.6 % of the
energy transferred to birds.
There is a loss of energy/biomass due to respiration/excretion/movement.

30.
a) Food web.
b) Phytoplankton Krill Birds Leopard seal Smaller toothed whales or
Phytoplankton Krill Penguins Leopard seal Smaller toothed whales
c) The population of penguins will decrease.
d) Phytoplanktons are photosynthetic which means that they need sun light energy for photosynthesis.
e) The energy transfer from one food chain to the next is 10%.

Chapter 25: Evolution

1. The spontaneous generation hypothesis, or abiogenesis, asserts that life on earth has come from nonliving
material. For example, the fact that with time rats appeared around waste was considered in the past a
confirmation of this hypothesis. Some supporters of spontaneous generation associated it with the existence
of an active principle (the vital elan) that would be the source of life, a theory known as vitalism.
2. In 1953 Stanley Miller arranged an experimental apparatus that simulated the atmospheric conditions of the
primitive earth. The experiment contained a mixture of methane, ammonia, hydrogen and circulating water
that when heated was transformed into vapor. He submitted the mixture to continuous bombardment of
electrical discharge and after days obtained a liquid residual within which he discovered organic molecules
and among them surprisingly the amino acids glycine and alanine, the most abundant constituents of proteins.
Other researchers reproduced the Miller experiment and noted also the formation of other organic molecules
such as lipids, carbohydrates and nucleotides.
3. The two main evolutionary theories were lamarckism and darwinism.

4. Lamarckism is the theory that unites the law of use and disuse with the law of the transmission of acquired
characteristics, i.e., that asserted that acquired characteristics, for example, the muscular mass, could be
transmitted from a parent to its offspring. The theory was proposed by the French naturalist Lamarck in the
beginning of the 19th century. At that time the idea was not so absurd since nobody knew how the
transmission of hereditary characteristics occurred. (Lamarck had great merit in introducing an evolutionary
theory based in natural law at a time dominated by fixism.)
5. Charles Darwin was an English naturalist born in 1809 and considered the father of the theory of evolution.
At the end of the year 1831, before turning 23 years of age, Darwin embarked as volunteer scientist on the
ship the Beagle for a five year expedition to the South American coast and the Pacific. During the voyage,
whose most famous passage was the stop in the Galapagos Islands, Darwin collected data that he used to
write his masterpiece “The Origin of Species” (1859).

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 6. The mentioned mechanism is the natural selection.

7. Darwin recognized that in a same species there were individuals with different characteristics. He also
realized that those differences could lead to different survival and reproduction chances for each individual.
Therefore he discovered the importance of the environment acting upon organisms and preserving those
having more advantageous characteristics for survival and more able to generate offspring and so he
described the basis of the principle of natural selection.
8. Both lamarckism and darwinism are evolutionary theories as opposed to fixism, both admit the existence of
processes that caused changes in the characteristics of the living beings in the past. They have however
different explanations for those changes. Lamarckism combines the law of use and disuse with the law of the
transmission of acquired characteristics to explain the changes. Darwinism defends the action of the natural
selection.
9. (1) An earthquake’s lifting of a mussel bed 9 feet above the water supported his idea that continents and
oceans had changed dramatically. (2) The diversity of tropical rain forests and unusual animals such as
boobies and marine iguanas encouraged Darwin to reconsider the source of the vast diversity of life. (3)
Native cultures like the Maoris in New Zealand raised questions about the relationship between humans and
animals and suggested to Darwin that civilizations might also evolve. (4) Sedimentary rocks such as those
which housed Megatherium fossils implied gradual changes in landforms as opposed to catastrophic floods.
(5) The patterns of variation in tortoises and birds on the Galapagos Islands led Darwin to doubt the
immutability of species.

10. Like all scientific theories, Darwin’s was a product of both his own work and the work of other scientists.
Lamarck’s ideas about in species, Lyell’s ideas about present forms arising from the past, Malthus’ principles
of population growth, and even the work of animal breeders all influenced Darwin’s thinking.
11. Evolution refers to the idea that all living species are related through common ancestry. All of today’s species
descended, with gradual changes, from very different species of the past. Ultimately, all life is related to a
single universal common ancestor which lived long ago. Natural selection is a process of environmentally-
determined differential survival and reproduction of chance variations – which explains how evolution
happens.
12. Both Lamarck and Darwin would agree that the human brain has probably changed through time. However,
Lamarck would say that early humans who used their brains a great deal thereby enlarged their brains, and
that their offspring inherited these well-used, bigger brains. Darwin would say that some early humans had
smaller brains, and some had bigger brains. Bigger brains allowed more creativity, which helped survival, so
those with bigger brains had a better chance of surviving and reproducing, passing their big brains on to their
offspring. Those with smaller brains more often died before reproducing. Gradually, bigger brains made up
more of the population. This undoubtedly took many, many steps and long, long periods of time!
13. This statement is incorrect in two important ways. We did not come from monkeys. Instead, we and monkeys
share common ancestors. We are very distant cousins, not descendants, of monkeys. A much more important
problem with this statement is that it is too narrow. We share common ancestors with all life – not just with
monkeys.
14.
a) Convergent evolution shows that structures from different embryologic origins evolve to perform the same
function, such as the wings of birds and those of insects. Divergent evolution shows that structures from the
same embryonic origin evolve to perform different functions such as the pentadactyl limbs modified to
perform different functions in different vertebrates.
b) Analogous structures perform the same function but have developed from different embryonic origins;
evidence of convergent evolution. Homologous structures perform different functions but are from the same
embryonic origin. They are evidence of divergent evolution.
15.
a) Struggle for existence: As members of a species continue to increase, it leads to overcrowding and hence
competition for food and space.Organisms have to continuously cope with harsh environmental
conditions such as high or low temperature. They also have to avoid predators hence struggle for
existence.
b) Survival of the fittest: Members of a species show great variations from one another. The result is that
some members can exploit their environment better than the rest. The offspring with favourable
characteristics survive to reproductive maturity and reproduce. Those with unfavorable characteristics
die young leaving no offspring. In that struggle, onlt the fit survive.

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Part III: Overview of the classification of livings

Table 1.1: The six kingdoms of life and their characteristics

MAJOR PLANT DIVISIONS AND CLASSES

TYPE OF PLANT DIVISION CLASSES COMMON NUMBER OF
NAME SPECIES
Non vascular plants Bryophyta BRYOPSIDA Mosses 10,000
Vascular Pteridophyta PTEROPSIDA Ferns 12,000
Seedless
Plants
Vascular Cycadophyta CYCADOPSIDA Cycads 100
Seed plant without flowers Ex : Cycas
(gymnosperms) revoluta
The seeds are formed in Gingkophyta GINGKOPSIDA Gingkoes 1
cones and are naked. Ex : Gingko
biloba

Coniferophyta CONIFEROPSIDA Conifers, cypress 550

Gnetophyta GNETOPSIDA Gnetophytes 70

FLOWERI ANGIOSPERMS Anthophyta or MAGNOLIOPSIDA DICOTS 140,000

NG Vascular seed plants with Magnoliophyta Ex : beans
PLANTS flowers LILIOPSIDA MONOCOTS 70,000
Ex : maize

Table 1.2: The major divisions of the kingdom plantae

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Table 1.3: Major animal phyla and classes
PHYLUM CHARACTERISTICS CLASSES EXEMPLES

PHYLUM PORIFERA porous body plan with spicules _ Sponges

of calcium carbonate
PHYLUM CNIDARIA Tentacles with cnidoblasts - Hydra, sea anemone
PHYLUM flattened body TURBELLARIA planarian
PLATYHELMINTHES without body cavity TREMATODA Blood flukes
CESTODA Tapeworms (Taenia)
PHYLUM NEMATODA Unsegmented round worms, _ Ascaris
muscles only longitudinal
PHYLUM ANNELIDA segmented body with a body OLIGOCHAETA Earthworm
cavity POLYCHAETA Nereis
HIRUDINEA Leeches
PHYLUM MOLLUSCA head, foot, and fleshy mantle GASTROPODA Snails, slugs
CEPHALOPODA Squids, octopus
BIVALVIA Clams
Jointed appendages, segmented INSECTA Bees, housefly
body and exoskeleton made of ARACHNIDA Scorpions, spiders
PHYLUM ARTHROPODA chitin CRUSTACEA Lobster, crayfish
DIPLOPODA millipedes
CHILOPODA centipedes
PHYLUM pentamerous radial symmetry, _
ECHINODERMATA water vascular system, Starfish, Sea urchin
notochord AGNATHA Lampreys
pharyngeal gill silts, CHONDRICHTYES Sharks
dorsal, hollow nerve cord and a OSTEICHTYES Tilapia
post anal tail AMPHIBIA Frogs, toads
PHYLUM CHORDATA
REPTILIA Lizards, snakes
BIRDS Doves, hens, eagles
MAMMALIA Humans, cats, mice

Table 1.4: A comparative summary of the vertebrate classes

CLASS CLASS CLASS CLASS CLASS AVES CLASS MAMMALIA
CHONDRICHT OSTEICHTYES AMPHIBIA REPTILIA (BIRDS) (MAMMALS)
YES (BONY (AMPHIBIAN (REPTILES)
(CARTILAGIN FISHES) S)
OUS FISHES)
Body covered by Body covered by Soft moist skin Dry scaly skin Skin bears Skin bears hair with two
scales scales can be used for with horny scales feathers, legs types of glands, sebaceous
gaseous have scales and sweet
exchange to
supplement
lungs
Cartilaginous Bony skeleton Bony skeleton Bony skeleton Bony skeleton Bony skeleton
skeleton
Paired, fleshy Paired pectoral Two pairs Two pairs Two pairs Two pairs pentadactyl
pectoral and and pelvic fins pentadactyl pentadactyl limbs pentadactyl limbs
pelvic fins. supported by limbs usually present limbs, front
Asymetrical tail bony rays, giving pair form
fin prevent greater wings
sinking (no air manoeuvrability.

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 bladder or swim Symetrical tail
bladder for fin.
buoyancy)
No No Metamorphosis No metamorphosis No No metamorphosis
metamorphosis metamorphosis from larva to metamorphosis
adult in life
cycle
No external ear No external ear No external ear No external ear No external ear External ear (in addition to
middle and inner ear)
Respiration by Respiration by Respiration by Respiration by Respiration by Respiration by lungs
gills gills gills (tadpoles), lungs lungs
lungs and skin
(adults)
Eggs produced, Eggs produced, Eggs produced, Fertilized yolk As reptiles but Only two genera lay eggs,
internal external external eggs laid on land eggs in the spiny anteater and the
fertilization fertilization fertilization. or eggs retained calcacerous duck-billed platypus.
Adults must until hatching. shells, internal Embryo develops in
return to water Eggs have a fertilization. mother. Mother has
for reproduction leathery skin. mammary glands which
Internal produce milk for the
fertilization newborn. Internal
fertilization.
Ectothermic Ectothermic Ectothermic Ectothermic Endothermic Endothermic

e.g. sharks, skates e.g. Tilapia, e.g. Frogs, toads e.g. Snakes, e.g. Eagle, e.g. Human, dogs, lions
and rays herring crocodiles, doves,
tortoises chickens

Table 1.5: The main orders of the vertebrate classes

CLASSES ORDERS EXAMPLES

AMPHIBIA ORDER ANURA (amphibians without tails ; hind limbs are adapted for Frogs and toads
jumping)

ORDER URODELA (amphibians with tails in adults) Salamanders

ORDER APODA (amphibians without legs) Caecilians

REPTILIA ORDER CHELONIA (reptiles with a body covered by a shell) Tortoises

ORDER CROCODILIA (large, heavy bodied aquatic reptiles) Crocodiles

ORDER SQUAMATA (reptiles with an upper jaw that is loosely joined Lizards and snakes
to the skull)

ORDER RHYNCOCEPHALIA (reptiles with a conspicuous spiny crest Tuataras

that runs down the animal’s back)

AVES ORDER GALLIFORMES (These terrestrial birds are usually plump- Grouse, pheasants, turkeys,
bodied and have limited flying ability) quails, hen
ORDER FALCONIFORMES (the members of this order have a sharp, Sparows, Eagles
curved beak and sharp talons. They are also called raptors)

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 ORDER PASSERIFORMES (perching and song birds. In most birds, Perching birds (over 70 families),
three toes point forward and one point backward. Passerines feed on a including crows, thrushes,
variety of foods including nectar, seeds, fruits and insects) sparrows, swallows, wrens,
warblers
ORDER CICONIIFORMES (long-necked, long-legged birds) Herons, storks, ibis

ORDER COLUMBIFORMES (These birds usually have relatively Pigeons, doves, sandgrouse
small heads, short necks and short slender bills)
ORDER STRUTHIONIFORMES (high-speed runners without flying Ostriches
ability)

Table 1.6: Overview of major orders of the class MAMMALIA

SUB CLASS ORDER MAIN CHARACTERISTICS EXAMPLES

MONOTREMES MONOTREMATA Lays eggs; have no nipples, suck milk from fur of mother Platypus,
echidnas
MARSUPIAL MARSUPIALIA Embryonic development completed in marsupial pouch Kangaroos,
MAMMALS koalas
ARTIODACTYLA Possess hooves with an even number of toes on each foot; Sheep, pigs,
herbivorous cattle, deer,
PLECENTAL giraffes
CARNIVORA Carnivorous; possess sharp, pointed canine teeth and Dogs, wolves,
molars for sheering lions, seals
CETACEA Marine forms with fish-shaped bodies, paddle like Whales, dolphins,
MAMMALS forelimbs and no hind limbs, thick layer of insulating porpoises
blubber
(EUTHERIAN CHIROPTERA Adapted for flying, possess a broad skinfold that extends Bats
from elongated fingers to body and legs
MAMMALS) EDENTATA Have reduced or no teeth Sloths, anteaters,
armadillos
INSECTIVORA Insect-eating mammals Moles, shrews,
hedgehogs
LAGOMORPHA Possess chisel-like incisors, hind legs longer than forelegs Rabbits, hares,
and adapted for running and jumping pikas
PERISSODACTYLA Possess hooves with an odd number of toes on each foot; Horses, zebras,
herbivorous tapirs, rhinoceros
PRIMATES Opposable thumb; forward-facing eyes; well-developed Lemurs,
cerebral cortex; omnivorous monkeys, apes,
humans
PROBOSCIDEA Have a long, muscular trunk; thick, loose skin; upper Elephants
incisors elongated as trunks
RODENTIA Possess chisel-like, continuously growing incisor teeth Rats, squirrels,
beavers, mice,
porcupines
SIRENIA Aquatic herbivores; possess finlike forelimbs and no hind Sea cows
limbs (manatees)

Table 1.6 : The phyla of the fungi kingdom and their structure
PHYLUM Structure Exemple

PHYLUM ZYGOMYCOTA Coenocytic hyphae Molds

PHYLUM BASIDIOMYCOTA Septate hyphae Mushrooms

PHYUM ASCOMYCOTA Septate hyphae or unicellular hyphae Yeasts, Penicillium

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Table 1.7: The main phyla of the kingdom protista and their characteristics
PHYLUM Characteristics Examples

Photosynthetic pigments
Some unicellular, others Euglenophyta Chlorophylls a and c, Euglena
multicellular without tissues. carotenoids, xanthophylls.
Algae are plant like; have cell Baccilariophyta Chlorophylls a and c, diatoms
walls made of cellulose and carotenoids, xanthophylls.
are able to make Chlorophyta Chlorophylls a and b, Green algae
carotenoids
photosynthesis.
Rhodophyta Chlorophylls a and b, Red algae
carotenoids
LOCOMOTION
SARCODINA Pseudopodia Amoeba

CILIOPHORA Cilia Paramecium

Unicellular and animal like ZOOMASTIGINA Flagella Trypanosoma

because they are
heterotrophic, they are able SPOROZOA None in adult Plasmodium
to make movement and have
no cell walls.

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