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CHAPTER 1: INTRODUCTION TO BIOLOGY

1.1 WHAT IS BIOLOGY?

Biology is the scientific study of life and living explores the structure, function, growth,
organisms. The word "biology" comes from evolution, distribution, and taxonomy of all
the Greek words "bios" (meaning "life") and living things, from the simplest bacteria to
"logos" (meaning "study"). This field of study complex ecosystems.

1.2 A BRIEF HISTORY OF BIOLOGY - Carl Linnaeus (1707-1778), who

developed the system of binomial
The study of biology dates back to ancient nomenclature
civilizations, with philosophers such as Aristotle
(384-322 BCE) and Epicurus (341-270 BCE) exploring - Charles Darwin (1809-1882), who
the natural world. However, it wasn't until the 19th proposed the theory of evolution through
century that biology emerged as a distinct scientific natural selection
discipline.
- Gregor Mendel (1822-1884), who
Key scientists who contributed significantly to the discovered the fundamental laws of inheritance
development of biology include:

- Antonie van Leeuwenhoek (1632-1723), known as

the "Father of Microbiology"

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Importance of reproduction to living organisms

➢ it leads to increase in number of organisms
➢ it ensures continuity of organisms
3. Excretion
Is the removal of waste products of
metabolism from organisms

Importance of excretion to living

organisms
➢ it prevents accumulation of wastes
which could be harmful to organisms
➢ it maintains the PH of body fluids of
organisms
4. Respiration
Is the breakdown of food to release energy
Importance of respiration to living
1.3 LIFE PROCESSES OF LIVING organisms
THINGS.
➢ it releases energy which is used for
Living organisms exhibit several fundamental life
other processes like movement, cell
processes, including:
division
These can also be called characteristics of ➢ It produces heat thus enables warm
living things. There are 7 characteristics blooded animals to stay warm even
in cold environments.
common to all living things i.e. growth,
5. Movement
reproduction, excretion, movement,
respiration, sensibility and nutrition. Is an action by an organism or part of an
organism causing a change in position or
1. Growth
place.
Is the permanent increase in the size of an
Importance of movement to organisms
organism by increasing in cell number, cell size or
both. ➢ Enables organisms to search for food
and water
Importance of growth to living organisms ➢ Enables organisms to run away from
➢ it enables organisms successfully survive to their enemies
reproduce 6. Sensibility (irritability)
2. Reproduction Is the ability of organisms to detect and
Is the process where new individuals are produced respond to stimuli
from their parents

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1.4 CAREERS IN BIOLOGY

Biology is a diverse field with numerous career opportunities, including:

- Research scientist - Medical doctor - Biotechnologist

- Conservation biologist - Veterinarian - Ecologist

- Environmental scientist - Science teacher

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List all the occupations shown in the photos above.

………………………………………………………………………………………………………
………………………………………………………………………………………….…………..
………………………………………………………………………………………………………
Explain to the class how biology knowledge is applied in three occupations of your choice.
………………………………………………………………………………………………………
………………………………………………………………………………………………………
………………………………………………………………………………………………………

Referring to the photos above, expplain to students of Gombe Junior school why biology must be a
compulsory subject in secondary schools.

1.5 IMPORTANCE OF BIOLOGY IN SOCIETY ➢ Increasing food production through

agricultural biotechnology
Biology plays a vital role in addressing various ➢ Understanding and mitigating the impact of
societal challenges, such as: climate change

➢ Improving human health through medical 1.6 RELATIONSHIP BETWEEN BIOLOGY

research
AND OTHER SCIENCES
➢ Developing sustainable solutions for
environmental conservation Biology is closely related to other scientific
disciplines, including:

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➢ Chemistry: the study of the chemical

processes that occur within living organisms
➢ Physics: the study of the physical principles
that govern the behavior of living systems
➢ Earth sciences: the study of the natural world
and the impact of human activities on the
environment
➢ Mathematics: the use of mathematical models
and statistical analysis in biology

1.7 BRANCHES OF BIOLOGY

Biology is a diverse field that encompasses numerous branches, including:

1. Anatomy: the study of the structure and organization of living organisms

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2. Biochemistry: the study of the chemical processes that occur within living organisms

3. Biophysics: the application of physical principles to the study of living systems

4. Botany: the study of plants and their interactions with the environment

5. Cell biology: the study of the structure and function of cells

6. Ecology: the study of the relationships between living organisms and their environment

7. Embryology: the study of the development of living organisms from fertilization to birth

8. Entomology: the study of insects and their interactions with the environment

9. Environmental the study of the natural world and the impact of human activities on the
science: environment

10. Genetics: the study of heredity and variation

11. Histology: the study of the structure and organization of tissues

12. Immunology: the study of the immune system and its responses to disease

Student activities:

AELMORTCAEHLO

ITCELLSRTAESUT

TERMSOFBIOLOGY

LOGOSBIOSPHEREC

ECOSYSTEMSUPPOR

TAXONOMYCELLSDI

VERSITYOFLIFEON

Find and shade the following words from the table above.

- biology - logos - organism - taxonomy

- bios - cell - ecosystem - diversity

Life Processes Matching Game

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Match each life process with its definition:

Life Processes: Definitions:

1. Respiration A. The process by which organisms obtain and utilize nutrients.

2. Excretion B. The ability of an organism to detect and respond to stimuli.

3. Nutrition C. The process by which organisms remove waste products from their bodies.

4. Growth D. The process by which organisms increase in size and complexity.

5. Sensitivity E. The process by which organisms move from one place to another.

6. Movement F. The process by which organisms exchange oxygen and carbon dioxide.

The following are examples of biology-related careers

1. Research Scientist 3. Medical Doctor 5. Environmental Scientist

2. Conservation Biologist 4. Veterinarian

Research information below for each career:

- Job description

- Required education and training

- Potential work environments

Present your findings to the class, highlighting the diversity of career opportunities in biology.

CLASS EXERCISES:

Exercise 1: Biology Terminology Matching

Task: Match the biology terms with their definitions:

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Terms: Definitions:
1. Cell A. A group of similar cells that work
2. Tissue together
3. Organ B. A living thing that can function on its
4. Organism own
5. Ecosystem C. A structure composed of two or more
tissues
D. The basic unit of life
E. A community of living and non-living
things interacting

Exercise 3: Biology Word Scramble

Unscramble the following biology words:

1. TIENR

2. OTSGIN

3. RETAHW

4. ELCOSYS

5. DNA

Exercise 4: Biology True or False_

Identify the following statements as true or false:

All living things are made up of cells. True False

Plants are the only organisms that undergo True False

photosynthesis.

The human body is composed of over 60% water. True False

DNA is found only in the nucleus of eukaryotic cells. True False

Mitosis is the process of cellular respiration. True False

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Exercise 5: Biology Fill-in-the-Blanks

Fill in the blanks with the correct biology terms:

1. The process by which plants convert sunlight into energy is called _______________________.

2. The largest living structure on Earth is the _______________________.

3. The scientific study of the structure, behavior, and evolution of the universe is called
_______________________.

4. The process by which water moves through a plant, from the roots to the leaves, is called
_______________________.

5. The smallest unit of life is the _______________________.

Activities:

Activity 1: Life Processes and Biology Careers

Instructions:

1. Divide into groups of 3-4 students.

2. Each group will be assigned a biology-related career (see below).

3. Research the career and its responsibilities.

4. Identify the life processes that are relevant to the career.

5. Create a poster or presentation that illustrates the connections between the life processes and the
biology career.

2. Biology Careers:

Group 1: Research Scientist

Group 2: Conservation Biologist

Group 3: Medical Doctor

Group 4: Veterinarian

Activity 3: Biology Terminology and Life Processes Sequencing

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Instructions:

1. Match the biology terminology with the correct life process.

2. Sequence the life processes in the correct order.

3. Explain the connections between the biology terminology and the life processes.

Biology Terminology: Life Processes:

1. Cell 1. Respiration

2. Tissue 2. Nutrition

3. Organ 3. Excretion

4. Organism 4. Growth

5. Ecosystem 5. Movement

Living Things and Non-Living Things

2.1 Introduction

The world around us is composed of living and the other hand, do not possess these
non-living things. Living things, also known as characteristics. In this chapter, we will explore
organisms, are characterized by their ability to the differences between living and non-living
grow, reproduce, respond to stimuli, and things, with a focus on life processes.
maintain homeostasis. Non-living things, on

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2.2 CHARACTERISTICS OF LIVING THINGS 3. Homeostasis: Living things maintain a stable

internal environment despite changes in the
Living things exhibit several key characteristics, external environment.
including:
4. Growth and Development: Living things
1. Organization: Living things are composed of grow and develop according to specific
cells, which are the basic units of life. instructions coded in their DNA.
2. Metabolism: Living things carry out a series of 5. Reproduction: Living things produce
chemical reactions that allow them to grow, offspring, either sexually or asexually.
maintain themselves, and respond to their
environment. 6. Response to Stimuli: Living things
respond to changes in their environment,
such as light, temperature, and touch.

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7. Evolution: Living things evolve over time from the waste

through the process of natural selection. body products
Growth Increase in Do not
size and grow or
complexity change
over time
Sensitivity Respond to Do not
2.3 CHARACTERISTICS OF NON-LIVING THINGS changes in respond to
the stimuli
Non-living things, on the other hand, do not exhibit environment
these characteristics. Instead, they are typically: Movement Move from Do not
one place to move
1. Inorganic: Non-living things are not composed another
of cells or organic molecules. Reproduction Produce Do not
offspring reproduce
2. Inert: Non-living things do not respond to
stimuli or changes in their environment.
2.5 Examples of Living and Non-Living
3. Unchanging: Non-living things do not grow, Things
develop, or evolve over time.
Here are some examples of living and non-
2.4 Comparison of Living and Non-Living living things:
Things Based on Life Processes
Living Things: Non-Living Things:
Here's a comparison of living and non-living - Plants - Rocks
things based on life processes: - Animals - Minerals
- Fungi - Air
- Bacteria - Water
- Protists - Metals
Life Process Living Non-Living
Things Things
Respiration Carry out Do not
In conclusion, living things are characterized
cellular carry out
respiration to respiration by their ability to grow, reproduce, respond to
generate stimuli, and maintain homeostasis. Non-living
energy things, on the other hand, do not exhibit these
Nutrition Obtain Do not characteristics. Understanding the differences
nutrients obtain between living and non-living things is
from the nutrients essential for understanding the natural world
environment
and our place within it.
Excretion Remove Do not
waste remove
products

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Class Work Exercises:

1. Complete the following table by indicating whether each characteristic is typical of living things or
non-living things:

Characteristic Living Things Non-Living Things

Organization

Metabolism

Homeostasis

Growth and Development

Reproduction

Response to Stimuli

Evolution

2. Identify the following as living or non-living things (with at least two reasons)

A chair ……………………………………………………………………………………………………………………………………………….

A tree………………………………………………………………………………………………………………………………………………….

A car……………………………………………………………………………………………………………………………………………………

A human being……………………………………………………………………………………………………………………………………

A rock…………………………………………………………………………………………………………………………………………………

3. You are required to write a simple summary on whether a car is a living or a non- living thing using the
one provided in the picture. Read the statement below provided on the features of a Lamborghini,
brainstorm on them as a group and use them to write the report required. “The picture below shows
Lamborghini Avanzado. It moves at a speed of 220 miles per hour. It consumes petrol which it burns to
produce energy and then exhausts fumes and spits fire as the waste products. It has sensors which
automatically control the levels of oil, temperature and pressure.”

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QN. Write a simplified summary on how you would classify a Lamborghini car; either as a living
thing or a non-living thing.
Your summary should include;
1. Characteristics of living things possessed by a Lamborghini
2. How a Lamborghini carries out the characteristics of living things
3. Characteristics of living things a Lamborghini lacks
4. How you would classify a Lamborghini (is it a living thing or not).
5. Reason why you classify it as a living or non-living thing.

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STUDENTS’ ACTIVITIES:

1. Create a Poster: SHORT PROJECTS.

Create a poster that illustrates the characteristics of 1. Create a Concept Map:

living things. Include examples and diagrams to
support your points. Create a concept map that illustrates the
relationships between living things, non-
2. Living and Non-Living Things Sorting Game: living things, and the characteristics of life.

The post cards distributed to you include living things 2. Write a Short Story:
and nonliving things. Let the group leader shuffle
them then as a group sort them into two categories. Write a short story that incorporates the
One box insert living things and the other non-living characteristics of living things. The story
things. Present your work to the class. should include examples of organization,
metabolism, homeostasis, growth and
3. Debate: development, reproduction, response to
stimuli, and evolution
As a class, organize a debate on the following motions.
3. Design an Experiment:
✓ All living things are capable of movement.
✓ Non-living things can respond to stimuli. Design an experiment to test the effect of a
✓ Living things are always composed of cells. specific variable on a living thing. For
example, students might investigate the
effect of light on plant growth or the effect of
Research your topic and prepare arguments for or temperature on the metabolism of a small
against the statement. Hold a class debate, animal.
allowing students to present their arguments and
respond to counterarguments.

Chapter 3: Plants and Animals - The Major

Groups of Living Things
3.1 Introduction
Living things can be broadly classified into two features of each group. In this chapter, we will
major groups: plants and animals. This explore the characteristics of plants and animals,
classification is based on the characteristics and and learn how to distinguish between them.

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3.2 Characteristics of Plants ✓ They reproduce by producing seeds or spores

Plants are living things that are capable of making their

own food through a process called photosynthesis.
They have the following characteristics:

✓ They are autotrophic, meaning they produce

their own food
✓ They have chloroplasts, which contain the
pigment chlorophyll
✓ They have cell walls made of cellulose
✓ They have roots, stems, and leaves

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3.3 Characteristics of Animals

Here is a comparison of the characteristics of
Animals are living things that are not capable of plants and animals:
making their own food. They have the following
characteristics:
Characteristic Plants Animals
✓ They are heterotrophic, meaning they obtain
their food from other sources Autotrophic Heterotrophic
✓ They do not have chloroplasts or chlorophyll Autotrophy/
✓ They have cell walls made of chitin or collagen Heterotrophy
✓ They have sensory organs and a nervous
system Present Absent
✓ They reproduce by laying eggs or giving birth Chloroplasts/
to live young Chlorophyll

3.4 Comparison of Plants and Animals Cell Walls Cellulose Chitin/Collagen

Roots/Stems/ Present Absent

Leaves

Sensory Absent Present

Organs/Nerv
ous System

Reproduction Seeds/Spores Eggs/Live Young

3.5 Classification of Plants and Animals Plants and animals can be further classified into
smaller groups based on their characteristics. Here is

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a brief overview of the classification of plants and - Fish cold-blooded, aquatic

animals: animals

- Plants:

In conclusion, plants and animals are the two major

groups of living things. Plants are autotrophic, have
chloroplasts, and reproduce by producing seeds or
spores. Animals are heterotrophic, do not have
chloroplasts, and reproduce by laying eggs or giving
birth to live young. Understanding the
moss Coral Fern dolphin Bacteria cat characteristics and classification of plants and
animals is essential for understanding the diversity
of life on Earth.
Algae simple, aquatic plants

Bryophytes mosses and liverworts

Simple exercises:
Pteridophytes ferns and horsetails
1. Describe the main differences between plants and
Gymnosperms conifers and cycads animals.

Angiosperms flowering plants 2. complete the table below by writing whether the
organism is a plant or animal.
- Animals:

- animals without
Invertebrates backbones 3. Create a diagram that illustrates the characteristics
of plants and animals. Include examples and labels to
- Vertebrates animals with backbones support your points.
- Mammals warm-blooded, hairy 4. Organize the class into two groups, then research
animals your topic and prepare arguments for or against the
statement. Hold a class debate, allowing you to
- Birds warm-blooded, feathered
present their arguments and respond to
animals counterarguments.

- Reptiles cold-blooded, scaly Motions you may consider to choose from

animals
"Plants are more important than animals for the
- Amphibians cold-blooded, moist- survival of humans."
skinned animals
"Animals are more intelligent than plants."

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"Plants and animals have equal importance in Write a short story that incorporates the
the ecosystem." characteristics of plants and animals. The story
should include examples of how plants and
Simple mini projects: animals interact and depend on each other.
1. Create a Food Web: 3. Design an Ecosystem:
Create a food web that illustrates the Design an ecosystem that includes both plants
relationships between plants and animals in an and animals. The ecosystem should include
ecosystem. Include examples of producers, examples of producers, consumers, and
consumers, and decomposers. decomposers, and should illustrate the
2. Write a Short Story: relationships between the different components.

CELLS
Cells are the basic structural and functional Imagine a tiny, self-contained world, where
units of living organisms. They are the intricate processes unfold with precision and
building blocks of life, and all living things are purpose. This is the realm of the cell, the
composed of one or more cells. fundamental unit of life. But before we delve
into the fascinating world of cells, let's
The Cellular Universe explore some interesting comparisons.

The Cell: A Universe unto Itself

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A cell is often compared to a dry cell, a Similarly, a cell is a confined space that
battery that powers our daily devices. Just as contains the genetic material, organelles, and
a dry cell generates energy, a living cell is the cytoplasm necessary for life.
power source of life, converting energy and
nutrients into the building blocks of life. However, unlike a prison cell, a living cell is a
dynamic, thriving entity that is connected to
Another comparison can be made to a prison and interacts with its surroundings.
cell, a confined space that holds its occupants.

The Cell: A Hub of Life Processes Types of Cells

So, how is a cell related to life processes? The There are many different types of cells, each
answer lies in its incredible complexity and with its own unique structure and function.
organization. A cell is like a tiny factory, Some examples include:
where raw materials are converted into
energy, proteins, and other essential • Prokaryotic Cells: Cells without a
molecules. true nucleus, such as bacteria.

Basic Unit of Life • Eukaryotic Cells: Cells with a true

nucleus, such as plants and animals.
All living organisms are composed of one or
more cells. A cell is the smallest unit of life • Stem Cells: Cells that have the ability
that can replicate independently, and it is the to differentiate into different cell
basic building block of all living things. types.

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STRUCTURE AND FUNCTIONS OF TYPICAL ANIMAL AND PLANT CELLS

If a very thin slice of a plant stem is cut from the tip of a plant shoot and
and studied under a microscope, the stem photographed through a microscope. It is
appears to consist of thousands of tiny, 60 times larger than life, so a cell which
box-like structures. These structures are appears to be 2 mm long in the picture is
called cells. Figure 1.1 is a thin slice taken only 0.03 mm long in reality.

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Itis possible to make a drawing, like that The liquid part of cytoplasm is about
in Figure 1.4, to show the features that 90%
are present in most cells. All cells have a water, with molecules of salts and sugars
cell membrane, which is a thin dissolved in it. Suspended in this
boundary enclosing the cytoplasm. solution there are larger molecules of
Most cells have a nucleus. lipids (fats and oils) and proteins (see
Cytoplasm Chapter 4). Lipids and proteins may be
Under the ordinary microscope (light used to build up the cell structures, like
microscope), cytoplasm looks like a thick the membranes. Some of the proteins are
liquid with particles in it. In plant cells it enzymes (see Chapter 5). Enzymes
may be seen to be flowing about. The control the rate and type of chemical
particles may be food reserves like oil reactions that take place in the cells.
droplets Some enzymes are attached to the
or granules (small particles) of starch. membrane systems of the cell, while
Other particles are structures known as others float freely in the liquid part of
organelles, which have special functions the cytoplasm.
in the cytoplasm. In the cytoplasm, large Cell membrane
numbers of chemical reactions are
This is a thin layer of cytoplasm around
taking place, which keep the cell alive by
the outside of the cell. It stops the cell
providing energy and making substances
contents from escaping and controls
that the cell needs.
which substances can enter and leave the
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cell. In general, oxygen, food and water cytoplasm because, in prepared

are allowed to enter; waste products are sections, it takes up certain stains more
allowed to leave; and harmful substances strongly than the cytoplasm. The
are kept out. In this way the cell function of the nucleus is to control the
membrane maintains the structure and type and quantity of enzymes produced
chemical reactions of the cytoplasm. by the cytoplasm. In this way it
regulates the chemical changes that
Nucleus (plural: nuclei)
take place in the cell. As a result, the
Most cells contain one nucleus, which is
nucleus controls what the cell will be, for
usually seen as a rounded structure
example, a blood cell,
covered by a membrane and fixed in the
cytoplasm. In drawings of cells, the
nucleus may be shown darker than the

Typical Animal Cell

A typical animal cell consists of the following ➢ Mitochondria: The powerhouses of

components: the cell where energy is produced.

➢ Plasma Membrane: A thin, semi- ➢ Endoplasmic Reticulum: A network

permeable membrane that surrounds of membranous tubules and sacs
the cell and regulates the movement involved in protein synthesis and
of materials in and out. transport.

➢ Cytoplasm: A jelly-like substance ➢ Ribosomes: Small organelles found

inside the cell membrane where many throughout the cytoplasm where
metabolic processes take place. protein synthesis occurs.

➢ Nucleus: The control center of the ➢ Lysosomes: Membrane-bound sacs

cell where DNA is stored. containing digestive enzymes that
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break down and recycle cellular waste of cilia, flagella, and the spindle fibers
and foreign substances. that separate chromosomes during
cell division.
➢ Centrioles: Small, cylindrical
organelles involved in the formation

PLANT CELLS:

A few generalized animal cells are shown in compounds. It is non- living and allows
Figure while Figure 1.6 is a drawing of two water and dissolved substances to pass
palisade cells from a plant leaf. through it. The cell wall is not selective like
the cell membrane.
Plant cells differ from animal cells in (Note: Plant cells do have a cell
several ways because they have extra membrane, but it is not easy to see or
structures: a cell wall, chloroplasts and draw because it is pressed against the
sap vacuoles. inside of the cell wall)
Under the microscope, plant cells are quite
Cell wall distinct and easy to see because of their cell
The cell wall, which is outside the walls. In Figure 1.1 it is only the cell walls
membrane, contains cellulose and other (and in some cases the nuclei) that can be
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seen. Each plant cell has its own cell wall but the green substance chlorophyll
the boundary between two cells side by side
does not usually show up clearly. So, cells
next to each other appear to be sharing the CASE STUDY:
same cell wall.
A patient has been diagnosed with a genetic
Vacuole
disorder that affects the functioning of their
Most mature plant cells have a large, fluid-
mitochondria. The patient's cells are unable to
filled space called a vacuole. The vacuole
contains cell sap, a watery solution of produce enough energy to support their
sugars, salts and sometimes pigments. bodily functions.
This large, central vacuole pushes the
cytoplasm outwards so that it forms just Questions:
a thin lining inside the cell wall. It is the
1. What are the implications of mitochondrial
outward pressure of the vacuole on the
cytoplasm and dysfunction on cellular energy production?
cell wall that makes plant cells and their
tissues firm (see ‘Osmosis’ in Chapter 3). 2. How might the patient's symptoms be
Animal cells may sometimes have small related to their mitochondrial dysfunction?
vacuoles in their cytoplasm, but they are
usually produced to do a special job and 3. What are some potential treatments for the
are not permanent. patient's condition?

Chloroplasts
Chloroplasts are organelles that contain

Name of part Description Where found Function

cytoplasm jelly-like with particles enclosed by the contains the cell organelles, e.g.
and organelles in cell membrane mitochondria and nucleus
site of chemical reactions
cell membrane a partially permeable layer around the cytoplasm prevents cell contents
Animal and plant cells

that forms a boundar y around from escaping

the cytoplasm
controls what substances
enter and leave the cell
nucleus a circular or oval structure inside the cytoplasm controls cell division
containing DNA in the form
controls cell
of chromosomes
development
mitochondria circular, oval or slipper- inside the cytoplasm responsible
controls cell for aerobic
activities
shaped organelles respiration
ribosomes small, circular structures inside the cytoplasm protein synthesis
attached to membranes or lying
free
cell wall a tough, non-living layer made around the outside prevents plant cells from
Plant cells

of cellulose surrounding the of plant cells bursting

cell membrane
allows water and salts to
only

pass through (freely

vacuole a fluid-filled space surrounded by inside the cytoplasm contains salts and sugars
permeable)
a membrane of plant cells
helps to keep plant cells firm

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chloroplast an organelle containing inside the cytoplasm traps light energy for
chlorophyll of some plant cells photosynthesis

SPECIALIZATION OF CELLS:

When cells have completed the process of cell 2. Develop a distinct shape.
division, they become specialized.
3. Special kinds of chemical changes
Specialized cells are cells that have adapted to take place in their cytoplasm.
perform one specific function. These cells
have distinct structures that enable them to The specialization of cells to carry out
special functions in an organism is
carry out their specialized roles.
sometimes called ‘division of labor’ within
Such cells: the organism. Similarly, the special
functions of mitochondria and other cell
1. Do one special job organelles maybe called division of labor
within the cell.

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EXAMPLES OF SPECIALIZED CELLS IN ANIMALS:

➢ Nerve Cells (Neurons): Long, thin cells ➢

with extensions called axons and
dendrites that transmit and receive nerve ➢ White Blood Cells: Cells that play a
impulses. crucial role in the immune system,

➢ Muscle Cells: Elongated cells with ➢ defending the body against infections and
contractile proteins that enable diseases.
movement and contraction. ➢ Sensory Cells: Specialized cells that
➢ Red Blood Cells: Flexible, disk-shaped detect and respond to stimuli, such as
cells that carry oxygen throughout the light, sound, touch, taste, and smell.
body.

EXAMPLES OF SPECIALIZED CELLS IN PLANTS:

➢ Palisade Cells: Elongated cells in plant protect against herbivores, and attract
leaves that contain many chloroplasts for pollinators.
photosynthesis.
➢ Xylem Cells: Specialized cells that transport
➢ Guard Cells: Specialized cells that regulate water and minerals from the roots to the
gas exchange and water loss through the leaves of plants.
stomata (small openings) on plant leaves.
➢ Phloem Cells: Cells that transport sugars,
➢ Trichome Cells: Hair-like cells on plant amino acids, and other organic compounds
surfaces that help to reduce water loss, produced by photosynthesis from the leaves
to the rest of the plant.

These specialized cells work together to maintain the overall health and function of the organism.
Understanding the structure and function of specialized cells can provide valuable insights into the
intricate and fascinating world of life.

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LEVELS OF ORGANIZATION IN ORGANISMS

Some microscopic organisms are made of A tissue, like bone, nerve or muscle in
one cell only (see ‘Features of organisms’ animals, and epidermis, xylem or pith in
in Chapter 2). These can carry out all the plants, is made up of large numbers of
processes needed to keep them alive. The cells. These are often just a single type.
cells of the larger plants and animals The cells of each type have a similar
cannot survive on their own. A muscle cell structure and function so that the tissue
could not obtain its own food and oxygen. itself has a special function. For example,
Other specialized cells provide the food muscles contract to cause movement,
and oxygen needed for the muscle cell to xylem carries water in plants. Figure 1.17
live. Unless these cells are grouped shows how some cells are arranged to
together in large numbers and made to form simple tissues. Some forms of tissues
work together, they cannot stay alive. are epithelium,
tubes, sheets and glands
Tissues
Key definitions

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A tissue is a group of cells with similar structures working together to perform a shared function.

Organs
Organs are made of several tissues heart, lungs, intestines, brain
grouped together to make a structure and eyes are further examples of organs
with a special job. For example, the in animals. In flowering plants, the root,
stomach is an organ that contains tissues stem and leaves are the organs. Some of
made from epithelial cells, gland cells and the tissues of the leaf are epidermis,
muscle cells. These cells are supplied with palisade tissue, spongy tissue, xylem and
food and oxygen brought by blood vessels. phloem (see Chapter 6).
The stomach also has a nerve supply. The

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Key definitions
An organ is a structure made up of a group of tissues working together to perform a specific function.

Organ systems
An organ system usually describes a group of organs with closely related functions. For
example, the
heart and blood vessels make up the circulatory system; the brain, spinal cord and
nerves make up the nervous system (Figure 1.18). In a flowering plant, the stem, leaves
and buds make up a system called the shoot (Figure 7.5 on page 103).
Key definitions
An organ system is a group of organs with
related functions working together to
perform a body function.

Therefore, living organisms are composed of several levels of organization, each with
distinct structures and functions:

Cell: The basic unit of life, where metabolic processes take place.

Tissue: A group of similar cells that perform a specific function, such as

muscle tissue or epithelial tissue.

Organ: A structure composed of two or more types of tissues that

perform a specific function, such as the heart or lungs.

System: A group of organs that work together to perform a specific

function, such as the circulatory system or digestive system.

Organism: A living being composed of one or more cells, with the ability to
grow, reproduce, respond to stimuli, and maintain homeostasis.

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CASE STUDY 5. What are some potential long-term effects of

mitochondrial dysfunction on the patient's
A patient has been diagnosed with a genetic overall health?
disorder that affects the functioning of their
mitochondria. The patient's cells are unable to 6. How might the patient's genetic disorder be
produce enough energy to support their inherited, and what are the implications for
bodily functions. their family members?

Questions: 7. What are some potential alternative

therapies or supplements that might help
alleviate the patient's symptoms?
1. What are the implications of mitochondrial 8. How might the patient's mitochondrial
dysfunction on cellular energy production? dysfunction impact their ability to exercise or
2. How might the patient's symptoms be engage in physical activity?
related to their mitochondrial dysfunction? 9. What are some potential complications or
3. What are some potential treatments for the comorbidities that might arise from the
patient's condition? patient's mitochondrial dysfunction?

4. How might the patient's diet and lifestyle 10. How might advances in genetic
impact their mitochondrial function? engineering or gene therapy potentially
impact the treatment of the patient's
condition?

CHAPTER 2: CLASSIFICATION OF LIVING THINGS

2.1 INTRODUCTION

Classification is the process of grouping living There are millions of different organisms
things into categories based on their shared living on the Earth. Biologists sort them into a
characteristics. This helps us to better meaningful order, they classify them. There
understand the diversity of life on Earth and to are many possible ways of classifying
identify relationships between different organisms. You could group all aquatic
organisms. organisms together or put all black and white
creatures into the same group. However, these

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do not make very meaningful groups; a features that are shared by as large a group as
seaweed and a porpoise are both aquatic possible. In some cases, it is easy. Birds all
organisms, a magpie and a zebra are both have wings, beaks and feathers; there is rarely
black and white. Neither of these pairs has any doubt about whether an animal is a bird or
much in common apart from being living not. In other cases, it is not so easy. As a result,
organisms and the magpie and zebra being biologists change their ideas from time to time
animals. These would be artificial systems of about how living things should be grouped.
classification. Biologists look for a natural New groupings are suggested and old ones
system of classification using important abandoned

CAROLUS LINNAEUS AND BINOMIAL NOMENCLATURE

Carolus Linnaeus (1707-1778) was a Swedish botanist, physician, and zoologist who is considered
the father of taxonomy. Linnaeus developed the system of binomial nomenclature, which uses a two-
part name consisting of the genus and species names to identify each species.

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CONTRIBUTIONS OF CAROLUS LINNAEUS more northern populations are more brown

than black). Males also have a white flash across
Linnaeus' contributions to classification their shoulder. The female has completely
include: brown upper feathers and grey–brown
➢ Development of the binomial underparts. Its scientific name is Copsychus
nomenclature system fulicatus and the adult is about 17cm long (see
Figure 2.1). However, someone living in Britain
➢ Classification of over 13,000 plant and would describe a robin very differently. It has
animal species the species name Erithacus rubecula, and is
very distinctive. It has a round body with a
➢ Publication of the book "Systema bright orange–red breast, a white belly and
Naturae" (1735), which laid the olive–brown upper feathers. It is only 14cm
foundation for modern taxonomy long (see Figure 2.2). A British scientist could
get very confused talking to an Indian scientist
Binomial nomenclature Species must be named
about a robin! Again, the use of the scientific
in such a way that the name is recognized all
over the world. ‘Money Plant’ and ‘Devil’s Ivy’ name avoids any confusion.
are two common names for the same wild plant. THE BINOMIAL SYSTEM OF NAMING
If you are not aware that these are alternative SPECIES
names this could lead to confusion. If the
botanical name, Epipremnum aureum, is used
there is no chance of error.

The Latin form of the name allows it to be

used in all the countries of the world regardless
of language barriers. People living in the Indian
subcontinent are familiar with the appearance
of a robin. The male is mainly black, with some
red–brown bottom feathers (although some

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2. Genus name: The genus name is always

capitalized and is often derived from the Greek
or Latin name of the organism.

3. Species name: The species name is not

capitalized and is often derived from the
characteristics of the organism.

4. Unique name: Each organism has a unique

binomial nomenclature name that distinguishes
it from other organisms.

IMPORTANCE OF BINOMIAL
NOMENCLATURE

1. Universal language: Binomial

nomenclature provides a universal
language for scientists to communicate
about different organisms.

2. Universal identification: It provides a

unique way to identify each organism

3. The system helps to organize the vast

The binomial system of naming species is an
diversity of living organisms into one
internationally agreed system in which the
unique logical system.
scientific name of an organism is made up of
two parts, showing the genus and the species. Often, the specific name is descriptive, for
Binomial means ‘two names’; the first name example, edulis means ‘edible’, aquatilis
gives the genus and the second gives the means ‘living in water’, bulbosus means
species. For example, the Egyptian mongoose ‘having a bulb’, serratus means ‘having a
and Indian grey mongoose are both in the genus
Herpestes but they are different species; the
Egyptian mongoose is Herpestes ichneumon
and the Indian grey mongoose is Herpestes
edwardsii. The name of the genus (the generic
name) is always given a capital letter and the
name of the species (the specific name) always
starts with a lowercase letter

CHARACTERISTICS OF BINOMIAL
NOMENCLATURE

1.Two-part name: Each organism is given a

unique two-part name consisting of the genus
name and the species name.
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jagged (serrated) edge’ Figure 2.3 shows an example of a dichotomous

key that could be used to place an unknown
vertebrate in the correct class. Item 1 gives you
a choice between two alternatives. If the animal
is cold-blooded, you move to item 2 and make a
further choice. If it is warm-blooded, you move
to item 4 for your next choice. The same
technique may be used for assigning an
organism to its class, genus or species.
However, the important features may not
always be easy to see, so you must make use of
less basic characteristics.

DICHOTOMOUS KEYS

Dichotomous keys We use dichotomous keys to

identify unfamiliar organisms. Keys simplify the
process of identification. Each key is made up of
pairs of contrasting features

Dichotomous means two branches), starting

with quite general 9781398310582.indb 20
15/09/21 10:53 PM 21 Classification
systems characteristics and moving on to
more specific ones.

When we follow the key and make suitable

choices it is possible to identify the organism
correctly.

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You need to be able to develop the skills to make simple dichotomous keys, based on easily identifiable
features. If you know the main characteristics of a group, it is possible to draw up a logical plan for
identifying an unfamiliar organism. One such plan is shown in Figure 2.5.

The first question should be based on a feature that will split the group into two. The question is going
to give a ‘yes’ or ‘no’ answer. For each of the two subgroups formed, a further question based on the
features of some of that sub-group should then be written. Figure 2.7 shows one possible solution.

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2.4 IMPORTANCE OF CLASSIFICATION

Classification is important for several reasons:

1. Understanding relationships:
Classification helps us to understand the
relationships between different organisms and
how they have evolved over time.

2. Communication: Classification provides a

common language for scientists to
communicate about different organisms.

3. Identification: Classification helps us to

identify different organisms and to distinguish
between them.

EXAMPLES OF BINOMIAL NOMENCLATURE

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2.5 EXAMPLES OF DISORGANIZED PLACES

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HOW THINGS ARE ORGANIZED BY SORTING

Basing on the photographs above, explain why it is necessary to sort and classify items. (15marks)

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1. Kingdom 4. Order 7. Species

2. Phylum 5. Family

3. Class 6. Genus

Each level of classification provides more specific information about the characteristics of an organism
and its relationships to other organisms.

Such organization is similar to the organization of administration in our country

1. Kingdom: Country or Nation: Just as a 4. Order: Neighborhood or District: Just as a

country or nation is divided into smaller neighborhood or district is a smaller
administrative units, a kingdom is divided into administrative unit within a city or town, an
smaller taxa. order is a smaller taxon within a class.

2. Phylum: State or Province: Just as a state 5. Family: Family Unit: Just as a family unit is
or province is a smaller administrative unit a small group of related individuals, a family is
within a country or nation, a phylum is a a small group of related organisms within an
smaller taxon within a kingdom. order.

3. Class: City or Town: Just as a city or town is 6. Genus: Extended Family: Just as an
a smaller administrative unit within a state or extended family is a larger group of related
province, a class is a smaller taxon within a individuals, a genus is a larger group of related
phylum. organisms within a family.

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7. Species: Individual: Just as an individual is

a unique person within a family or community,
a species is a unique group of

organisms within a genus.

THE SEVEN KINGDOMS OF

LIVING THINGS The seven kingdoms of living things are a way
of classifying all living organisms into broad
categories based on their characteristics. The
seven kingdoms are:

1. Monera

2. Protista

3. Fungi

4. Plantae

5. Animalia

6. Chromista

7. Archaea
THE CRITERIA FOR CLASSIFICATION INTO 5. Body The level of complexity of the
KINGDOMS INCLUDE: organization: body organization, such as
unicellular or multicellular.
1. Cell The type of cell structure, such
structure: as prokaryotic or eukaryotic.

2. Cell wall: The presence or absence of a

cell wall, and its composition.

3. Mode of The way in which the organism

CHARACTERISTICS OF MEMBERS OF EACH
nutrition: obtains its nutrients, such as
autotrophy or heterotrophy. KINGDOM

The five-kingdom scheme: The kingdom is

4. The method of reproduction,
the largest group of organisms recognised by
Reproduction: such as sexual or asexual.

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created a sixth kingdom. The domains are: 1

Archaea: containing ancient prokaryotic
biologists. But how many kingdoms should organisms which do not have a nucleus
there be? Most biologists used to opt for the use surrounded by a membrane. They have an
of two kingdoms: Plant and Animal. This, independent evolutionary history to other
however, caused problems in trying to classify bacteria and their biochemistry is very different
fungi, bacteria and single-celled organisms, to other forms of life. 2 Eubacteria: prokaryotic
which do not fit obviously into either kingdom. organisms that do not have a nucleus
Many biologists now favour the five-kingdom surrounded by a membrane. 3 Eukarya:
scheme. This is a scheme that consists of organisms that have a membranebound
Animal, Plant, Fungus, Prokaryote and nucleus. This domain is subdivided into the
Protoctist. It is still not easy to fit all organisms kingdoms Protoctist, Fungus, Plant and Animal.
into the five-kingdom scheme. For example,
many Protoctista with chlorophyll (the
protophyta) show important similarities to
some members of the algae, but the algae are
classified into the plant kingdom. Viruses are
not included in any kingdom – they are not
considered to be living organisms because they
do not have cell membranes (made of protein
and lipid), cytoplasm and ribosomes, and do not
demonstrate the characteristics of living things:
they do not feed, respire, excrete or grow.
Although viruses do reproduce, this only
happens inside the cells of living organisms,
using materials provided by the host cell. This
kind of problem will always occur when we try
to come up with rigid classification schemes
with clear boundaries between groups. The
process of evolution cannot be expected to
result in a tidy scheme of classification for
biologists to use.

The three-domain scheme: As scientists learn

more about organisms, classification systems THE PLANT KINGDOM
change. Genetic sequencing has provided
scientists with a different way of studying
relationships between organisms. The three-
domain scheme was introduced by Carl Woese
in 1978 and involves grouping organisms using
differences in ribosomal RNA structure. Under
this system, organisms are classified into three
domains and six kingdoms, rather than five.
Splitting the Prokaryote kingdom into two has
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ferns vary from one species to another (see

Figures 2.27 and 2.28), but they are all several
cells thick.

Most of them have an upper and lower

epidermis, a layer of palisade cells and a spongy
mesophyll, like the leaves of a flowering plant
Ferns produce gametes but no seeds. The
zygote gives rise to the fern plant, which then
produces single-celled spores from many
sporangia (spore capsules) on its leaves. The
sporangia are formed on the lower side of the
leaf, but their position depends on the species of
fern. The sporangia are usually arranged in
compact groups (see Figure 2.29)

Plants are made up of many cells – they are

multicellular. Plant cells have an outside wall
made of cellulose. Many of the cells in plant
leaves and stems contain chloroplasts with
photosynthetic pigments (e.g. chlorophyll).
Plants make their food by photosynthesis. The
syllabus only requires knowledge of two groups
– ferns and flowering plants.

Ferns
Ferns are land plants with well-developed
structures. Their stems, leaves and roots are
very similar to those of the flowering plants.
The stem is usually completely below ground. In
bracken, the stem grows horizontally below
ground, sending up leaves at intervals. Roots
grow directly from the stem. The stem and
leaves have sieve tubes and water conducting
cells like those in the xylem and phloem of a
flowering plant (see Chapter 7). The leaves of
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all, monocots also have long, narrow leaves (e.g.

grasses, daffodils, bluebells) with parallel leaf
veins (see Figure 2.30(a)). The dicotyledons
(dicots for short) have two cotyledons in their
seeds. Their leaves are usually broad, and the
leaf veins form a branching network (see Figure
2.30(b)).

The Fungi kingdom Most fungi are made up of

Flowering plants Flowering plants reproduce
thread-like hyphae (see Figure 2.31), rather
by seeds that are formed in flowers. The seeds
than cells, and there are many nuclei scattered
are enclosed in an ovary. The general structure
throughout the cytoplasm in their hyphae (see
of flowering plants is described in Chapter 7.
Figure 2.32)
Examples are shown in Figure 2.26 on page 34.
Flowering plants are divided into two The fungi include organisms such as
subclasses: monocotyledons and dicotyledons. mushrooms, toadstools, puffballs and the
Monocotyledons (monocots for short) are bracket fungi that grow on tree trunks (Figure
flowering plants that have only one cotyledon in 2.33). There are also the less obvious, but very
their seeds. A cotyledon is an embryonic leaf important, mould fungi, which grow on stale
which often contains food stores. Most, but not bread, cheese, fruit or other food. Many of the

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mould fungi live in the soil or in dead wood. The celled (unicellular) organisms which have their
yeasts are single-celled fungi that have some chromosomes enclosed in a nuclear membrane
features similar to moulds. Some fungal species to form a nucleus. Some examples are shown in
are parasites, as is the bracket fungus shown in Figure 2.35. Some of the Protoctista (e.g.
Figure 2.33. A parasite is an organism living on Euglena) have chloroplasts and make their food
another organism (the host), gaining food and by photosynthesis. These Protoctista are often
shelter from it. It is a very one-sided referred to as unicellular. Organisms like
relationship. Fungal parasites live in other Amoeba and Paramecium take in and digest
organisms, particularly plants, where they solid food and so are animal-like in their
cause diseases that can affect crop plants, such feeding. They may be called
as the mildew on wheat. unicellular ‘animals. Amoeba is a protozoan
that moves by a flowing movement of its
cytoplasm. It feeds by picking up bacteria and
other microscopic organisms as it moves.
Vorticella has a stalk that can contract and feeds
by making a current of water with its cilia (tiny
hair-like organelles which project from the cell
surface). The current brings particles of food to
the cell. Euglena and Chlamydomonas have
chloroplasts in their cells and feed, like plants,
by photosynthesis.

Viruses There are many different types of virus

and they vary in their shape and structure. All
The Prokaryote kingdom These are the bacteria viruses, however, have a central core of RNA or
and the blue-green algae. They consist of single DNA (see Chapter 17) surrounded by a protein
cells but are different from other single-celled coat. Viruses have no nucleus, cytoplasm, cell
organisms because their chromosomes are not organelles or cell membrane, though some
organised into a nucleus. The structure of forms have a membrane outside their protein
bacterial cells is described in Chapter 1, pages coats. So, virus particles are not cells. They do
6–7. The Protoctist kingdom These are single- not feed, respire, excrete or grow, and it is
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arguable whether they can be classed as living generalized virus particle is shown in
organisms. Viruses do reproduce, but only Figure 2.36. The nucleic acid core is a coiled
inside the cells of living organisms, using single strand of RNA with a protein coat. The
materials provided by the host cell. A protein coat is called a capsid.

The animal kingdom Animals are multicellular organisms whose cells have no cell walls or
chloroplasts. Most animals ingest solid food and digest it internally.

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Reproduction Asexual or sexual

MONERA
Cell structure Prokaryotic Body organization Unicellular or
multicellular
Cell wall Present, composed of Examples Protozoa, algae, slime molds
peptidoglycan
Mode of Autotrophic or
nutrition: heterotrophic
Reproduction Asexual, by binary fission

Body Unicellular
organization FUNGI
Examples Bacteria, cyanobacteria Cell structure Eukaryotic
Cell wall Present, composed of chitin
Mode of decomposition or parasitism
nutrition
Reproduction Sexual or asexual, by spores.
Body Multicellular
organization
PROTISTA Examples_: Mushrooms, molds,
yeasts
Cell structure Eukaryotic

Cell wall Absent or present,

PLANTAE
composed of cellulose or
chitin
Mode of nutrition Autotrophic or Cell structure Eukaryotic
heterotrophic

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Cell wall Present, composed of Examples Brown algae, diatoms,

cellulose dinoflagellates

Mode of Autotrophic, by
nutrition photosynthesis ARCHAEA
Reproduction Sexual, by seeds or spores Cell structure Prokaryotic
Cell wall Present, composed of
Body Multicellular pseudopeptidoglycan
organization Mode of Autotrophic or
Examples ferns, Flowering plants, conifers, nutrition heterotrophic
Reproduction Asexual, by binary fission
ANIMALIA
Body organization Unicellular

Examples: Methanogens, thermophiles,

Cell structure Eukaryotic halophiles
Cell wall Absent
Mode of Heterotrophic, by
nutrition ingestion or
absorption
Reproduction Sexual, by gametes
Body Multicellular
organization
Examples Mammals, birds, reptiles,
amphibians, fish

CHROMISTA
Exercises:
Cell structure Eukaryotic
1. What is the main criterion for classifying
Cell wall Present, composed
of cellulose or living things into different kingdoms?
chitin
...............................................................................................
Mode of Autotrophic or
nutrition heterotrophic ...............................................................................................
...............................................................................................
Reproduction Sexual or asexual, ...............................................................................................
by spores or
gametes 2. Which kingdom includes bacteria and
Body Multicellular cyanobacteria?
organization

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............................................................................................... 3. Discuss the importance of classification in

............................................................................................... biology. How does classification help us
............................................................................................... understand the diversity of life on Earth?
.............................................................................................. (150-200 words)

4. What is the primary mode of nutrition 4. Choose one kingdom of living things and
for organisms in the kingdom Plantae? describe the characteristics that define it.
Provide examples of organisms that belong to
............................................................................................... this kingdom. (150-200 words)
...............................................................................................
............................................................................................... 5. Explain the concept of a dichotomous key
.............................................................................................. and how it is used in the classification of living
things. Provide an example of a dichotomous
5. Which kingdom includes mushrooms key used to classify a set of organisms. (150-
and molds? 200 words)
...............................................................................................
...............................................................................................
............................................................................................... Essay Questions
..............................................................................................
1. Discuss the evolution of the classification
5. What is the characteristic that distinguishes system of living things. How have our
prokaryotic cells from eukaryotic cells? understanding and classification of living
organisms changed over time?
...............................................................................................
............................................................................................... 2. Choose one of the six kingdoms of living
............................................................................................... things and discuss its significance in the
.............................................................................................. ecosystem. How do organisms in this kingdom
interact with their environment and other
organisms?

3. Compare and contrast the characteristics of

two different kingdoms of living things. How
do these differences reflect the unique
Long Response Questions adaptations and environments of organisms in
each kingdom?
1. Describe the characteristics that distinguish
the six kingdoms of living things (Animalia, Fill-in-the-Blank Questions
Plantae, Fungi, Protista, Chromista, and
Monera). (150-200 words) 1. The kingdom _______________________ includes
organisms that are capable of photosynthesis.
2. Compare and contrast the characteristics of
prokaryotic and eukaryotic cells. How do 2. The characteristic that distinguishes
these differences impact the classification of prokaryotic cells from eukaryotic cells is the
living things? (150-200 words) presence or absence of a _______________________.

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3. The kingdom _______________________ includes Cell wall made of

organisms that obtain their nutrients by cellulose
decomposing organic matter.
Ability to move and
4. The classification system of living things is respond to stimuli
based on the concept of _______________________.
Presence of chloroplasts
5. The kingdom _______________________ includes
Decomposition of
organisms that are capable of moving and
organic matter
responding to stimuli.
Presence of a nucleus
True or False Questions

1. True or False: All prokaryotic cells are

capable of photosynthesis.
Kingdom Sorting Puzzle
2. True or False: The kingdom Plantae
Sort the following organisms into their correct
includes only flowering plants.
kingdoms:
3. True or False: The characteristic that
Organism kingdom
distinguishes eukaryotic cells from
prokaryotic cells is the presence of a cell wall. Lion
4. True or False: The classification system of Mushroom
living things is based on the concept of
evolution. Oak tree

5. True or False: The kingdom Animalia Bacterium

includes only vertebrates.
Human

Fungus

Algae

Insect

Classification Table

Complete the table below by writing the

correct kingdom for each characteristic: Critical Thinking Questions

1. What are the implications of classifying an

organism into a particular kingdom? How
Characteristic Kingdom might this impact our understanding of its
biology and ecology?

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2. How do the characteristics of an organism rainforest. The organism is a multicellular

influence its classification into a particular eukaryote with a cell wall made of cellulose. It
kingdom? Provide examples to support your is capable of photosynthesis and has a unique
answer. characteristic: it can move slowly using
flagella.
3. What are the limitations of the current
system of classification? How might it be Questions:
improved?
1. Which kingdom would you classify this
4. How do the different kingdoms of living organism into? Why?
things interact and depend on each other?
Provide examples to illustrate your answer. 2. What characteristics of the organism
support your classification?
5. What are the potential consequences of
misclassifying an organism into the wrong 3. How might the discovery of this new species
kingdom? Provide examples to support your impact our understanding of the diversity of
answer. life on Earth?

SCENARIO BASED QUESTIONS 4. What are some potential implications of

classifying this organism into a particular
A new species of organism has been kingdom?
discovered in a remote region of the Amazon
rainforest. The organism is a photosynthetic, 5. How might the classification of this
multicellular eukaryote with a cell wall made organism be used to inform conservation
of cellulose. It is capable of moving slowly and efforts or management of ecosystems?
responding to stimuli.

Questions:

1. Which kingdom would you classify this

organism into? Why?

2. What characteristics of the organism

support your classification?

3. How might the discovery of this new species

impact our understanding of the diversity of
life on Earth?

Classification of a Newly Discovered

Organism
CASE STUDY:
A team of scientists has discovered a new Classification of a Fossilized Organism
organism in a remote region of the Amazon

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A fossilized organism has been discovered in a

layer of rock dating back to the Cambrian INSECTS
period. The fossil shows evidence of a
bilaterally symmetrical body plan and a
notochord.

Questions:

1. Which phylum would you classify this

fossilized organism into? Why?

2. What characteristics of the fossil support

your classification?

3. How might the discovery of this fossil

impact our understanding of the evolution of
life on Earth?

4. What are some potential implications of

4.1 COCKROACHES
classifying this fossilized organism into a
particular phylum?

5. How might the classification of this fossil be

used to inform our understanding of the
history of life on Earth?

I. External Structure

Body Flat, oval-shaped body

divided into three main
parts: head, thorax, and
abdomen
Head: Small, triangular head with
two large compound eyes
and two antennae
Thorax: Middle segment of the body,
bears six legs and two
wings

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Antennae Two long, thin

antennae used for
sensing the Abdomen: Long, segmented abdomen
environment with a distinctive rounded
Compound Two large compound tip
Eyes eyes made up of
thousands of
individual lenses
Simple Eyes Two smaller simple
eyes that detect light Wings:
and dark
Antennae Used to detect smells, Two pairs of wings, with the hindwings
sounds, and vibrations being much smaller than the forewings
Legs: Six jointed legs, each with a claw at the end

IV. Sensory Organs 4.1.2 Dangers

SPECIAL FEATURES

1. Spread diseases such as dysentery, 1. Can cause skin irritation and allergic
gastroenteritis, and salmonellosis reactions

2. Trigger allergies and asthma attacks 2. Can spread tapeworms and other parasites

3. Contaminate food and surfaces with their 3. Can contaminate water sources
saliva and feces
4. Can cause respiratory problems
4. Damage books, papers, and other cellulose-
based materials 5. Can spread E. coli and other bacteria

5. Can cause anemia and other nutritional

deficiencies

Some features on a cockroach that These features, combined with their ability to
enable it to carry out dangers: thrive in a wide range of environments, make
cockroaches a significant public health
concern.

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1. Strong Mandibles: Cockroaches have 6. Antennae: Cockroaches have antennae

strong, sharp mandibles that allow them to that help them detect food, navigate their
chew and tear through food, as well as other environment, and avoid predators. However,
materials like paper, cloth, and even leather. these antennae can also detect and respond
to pheromones, allowing them to
2. Hair-like Appendages: Cockroaches have communicate and coordinate with other
hair-like appendages on their legs and body cockroaches.
that allow them to pick up and carry disease-
causing bacteria, viruses, and other 7. Hard Exoskeleton: Cockroaches have a
microorganisms. hard exoskeleton that protects them from
predators and environmental stressors.
3. Flat, Oval-shaped Body: Cockroaches' flat However, this exoskeleton also makes them
bodies allow them to squeeze into tight resistant to many insecticides and other
spaces and hide in dark, moist areas, making control measures.
them difficult to detect and eliminate.
8. Ability to Survive without Water:
4. Six Legs: Cockroaches have six legs that Cockroaches can survive for weeks without
enable them to move quickly and easily, water, allowing them to thrive in
allowing them to spread diseases and environments with limited moisture. This
contaminate food and surfaces. ability also makes them more difficult to
eliminate, as

they can survive in areas with limited access

to water.

4.1.3 Importance
1. Food source for other animals
2. Decompose organic matter
3. Help to break down cellulose-based
materials 4.1.4 Control Measures
4. Can be used as a source of protein for
animal feed 1. Keep a clean and hygienic environment
5. Can be used in medical research
2. Store food in sealed containers

3. Eliminate standing water

4. Use traps and insecticides

5. Seal entry points

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4.2 HOUSEFLIES

I. External Structure

Body Small, grayish-black body

divided into three main
parts: head, thorax, and
abdomen
Head Small, rounded head with
two large compound eyes
and two antennae
Thorax Middle segment of the
body, bears six legs and
two wings
Abdomen Long, segmented abdomen
with a distinctive rounded
tip SPPECIAL FEATURES ON A HOUSEFLY

Legs Six jointed legs, each with a

III. Appendages claw at the end

Wings Two pairs of wings, with the

hindwings being much
smaller than the forewings

Antennae Two long, thin antennae used

for sensing the environment

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Compound Two large compound eyes Tarsal Specialized claws on the feet
Eyes made up of thousands of Claws that help the fly to grip
individual lenses surfaces

Simple Two smaller simple eyes that Halteres Small, club-shaped organs
Eyes detect light and dark that help the fly to balance
and navigate during flight.
Antennae Used to detect smells, sounds,
and vibrations

Proboscis A long, flexible tube that the

fly uses to suck up liquids

4.2.2 DANGERS OF HOUSE FLIES

1. Spread diseases such as typhoid, cholera, 6. Can contaminate water sources

and tuberculosis
7. Can spread tapeworms and other parasites
2. Contaminate food and surfaces with their
saliva and feces 8. Can cause anemia and other nutritional
deficiencies
3. Can spread E. coli and other bacteria
9. Can cause skin irritation and allergic
4. Can cause respiratory problems reactions

5. Can trigger allergies and asthma attacks 10. Can spread anthrax and other diseases

Houseflies are vectors for many diseases,

including:

- Typhoid - E. coli

- Cholera - Anthrax

- Tuberculosis

SOME FEATURES OF A HOUSEFLY THAT

ENABLE IT TO CAUSE DANGER:

1. Hair-like Appendages: Houseflies have 2. Salivary Glands: Houseflies have salivary

hair-like appendages on their legs and body glands that produce saliva containing
that allow them to pick up and carry disease- enzymes that break down food. However,
causing bacteria, viruses, and other these enzymes can also contaminate food and
microorganisms. surfaces, spreading diseases.

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3. Proboscis: Houseflies have a long, flexible up to 150 eggs at a time. This allows them to
proboscis that they use to suck up liquids. quickly colonize new areas and spread
This proboscis can also be used to regurgitate diseases.
and contaminate food and surfaces.
8. Ability to Survive in a Wide Range of
4. Tarsal Claws: Houseflies have specialized Environments: Houseflies can survive in a
tarsal claws on their feet that allow them to wide range of environments, from tropical to
grip surfaces and pick up disease-causing temperate climates. This allows them to
microorganisms. thrive in many different parts of the world
and spread diseases.
5. Compound Eyes: Houseflies have large
compound eyes that allow them to detect 9. Ability to Feed on a Wide Range of
movement and changes in their environment. Substances: Houseflies can feed on a wide
This helps them to locate and feed on range of substances, including decaying
decaying matter, which can spread diseases. matter, garbage, and human waste. This
allows them to pick up and spread disease-
6. Antennae: Houseflies have antennae that causing microorganisms.
help them to detect smells, sounds, and
vibrations. This allows them to locate and 10. Resistance to Insecticides: Houseflies
feed on food sources, which can spread have developed resistance to many
diseases. insecticides, making them difficult to control.
This allows them to continue to spread
7. Rapid Breeding Cycle: Houseflies have a diseases and cause harm to humans and
rapid breeding cycle, with females able to lay
animals.

IMPORTANCE
CONTROL MEASURES
1. Pollinate plants
1. Keep a clean and hygienic
2. Decompose organic matter environment

3. Help to break down cellulose-based materials 2. Store food in sealed containers

4. Can be used as a source of protein for animal 3. Eliminate standing water

feed
4. Use traps and insecticides
5. Can be used in medical research
5. Seal entry points

4.3 Termites

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mandibles and two

small antennae

Thorax Middle segment of the

body, bears six legs

Abdomen Long, segmented

abdomen with a
distinctive rounded tip

SPECIAL FEATURES:

Legs Six jointed legs, each

with a claw at the end

Antennae Two small antennae

used for sensing the
environment

Mandibles Two large mandibles

used for chewing and
manipulating food

Compound Two small compound

Eyes eyes made up of
thousands of individual
lenses

Simple Two smaller simple

EXTERNAL STRUCTURE Eyes eyes that detect light
and dark
Body Long, narrow body
divided into three main Antennae Used to detect smells,
parts: head, thorax, and sounds, and vibrations
abdomen

Head Small, rectangular head

with two large
Dangers 3. Can spread diseases such as histoplasmosis

1. Can cause significant damage to buildings 4. Can cause respiratory problems

and infrastructure
5. Can trigger allergies and asthma attacks
2. Can contaminate food and surfaces with
their saliva and feces 6. Can contaminate water sources

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7. Can spread tapeworms and other parasites 9. Can cause skin irritation and allergic
reactions
8. Can cause anemia and other nutritional
deficiencies 10. Can spread diseases such as
cryptococcosis

4.3.3 IMPORTANCE 4.3.4 CONTROL MEASURES

1. Decompose organic matter 1. Use termite-resistant materials for

construction
2. Help to break down cellulose-based
materials 2. Keep a clean and hygienic environment

3. Can be used as a source of protein for 3. Eliminate standing water

animal feed
4. Use traps and insecticides
4. Can be used in medical research
5. Seal entry points
5. Play a role in soil turnover and aeration

4.4 BEES

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Appendages

Body Small, hairy body

divided into three
main parts: head,
thorax, and abdomen

Head Small, triangular

head with two large
compound eyes and
two small antennae

Thorax Middle segment of

the body, bears six
legs and two wings

Abdomen Long, segmented

abdomen with a
distinctive rounded
tip

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4.4.4 Control Measures

1. Wear protective clothing when

working with bees

2. Use smoke to calm bees

SPECIAL FEATURES
3. Avoid disturbing bee nests
Legs Six jointed legs, each with a
claw at the end 4. Use bee HELMENTS

Antennae Two small antennae used

for sensing the
environment 4.4.3 Importance

Wings fore wings Two pairs of wings, with 1. Pollinate plants

the hindwings being much
2. Produce honey and beeswax
smaller than the
3. Can be used as a source of protein for
Stinger A modified ovipositor used
animal feed
for defense
4. Can be used in medical research
Compound Eyes Two large compound eyes
made up of thousands of 5. Play a role in maintaining ecosystem
individual lenses health

Simple Eyes Two smaller simple eyes

that detect light and dark

Antennae Used to detect smells,

sounds, and vibrations MOSQUITO

External Structure

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Body Small, slender body divided into Legs Six jointed legs, each with a claw at
three main parts: head, thorax, and the end
abdomen
Antennae Two small antennae used for sensing
Head Small, rounded head with two large the environment
compound eyes and two small
antennae Wings Two pairs of wings, with the
hindwings being much smaller than
Thorax Middle segment of the body, bears the forewings
six legs and two wings

Abdomen Long, segmented abdomen with a

distinctive rounded tip TYPES OF MOSQUITOES:

➢ Aedes Mosquitoes: These ➢ Culex Mosquitoes: These mosquitoes

mosquitoes are responsible for are responsible for spreading diseases
spreading diseases such as dengue such as West Nile virus, Japanese
fever, yellow fever, and Zika virus. encephalitis, and filariasis.

➢ Anopheles Mosquitoes: These ➢ Mansonia Mosquitoes: These

mosquitoes are responsible for mosquitoes are responsible for
spreading malaria. spreading diseases such as
chikungunya and Rift Valley fever.

DISEASES SPREAD BY MOSQUITOES:

1. Malaria: Spread by Anopheles mosquitoes, 4. Zika Virus: Spread by Aedes mosquitoes,

malaria is a serious and sometimes life- Zika virus is a viral disease that can cause
threatening disease. birth defects and other serious health
problems.
2. Dengue Fever: Spread by Aedes
mosquitoes, dengue fever is a viral disease 5. West Nile Virus: Spread by Culex
that can cause severe flu-like symptoms. mosquitoes, West Nile virus is a viral disease
that can cause severe symptoms, including
3. Yellow Fever: Spread by Aedes fever, headache, and encephalitis.
mosquitoes, yellow fever is a viral disease
that can cause severe symptoms, including
fever, chills, and bleeding.

DANGERS OF MOSQUITOES:

1. Malaria: Mosquitoes transmit malaria, a 2. Dengue Fever: Mosquitoes transmit dengue

serious and sometimes life-threatening fever, a viral disease that can cause severe flu-
disease. like symptoms.

3. Yellow Fever: Mosquitoes transmit yellow

fever, a viral disease that can cause severe
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symptoms, including fever, chills, and 6. Filariasis: Mosquitoes transmit filariasis, a

bleeding. parasitic disease that can cause severe
symptoms, including swelling, pain, and
4. Zika Virus: Mosquitoes transmit Zika virus, disability.
a viral disease that can cause birth defects
and other serious health problems. 7. Chikungunya: Mosquitoes transmit
chikungunya, a viral disease that can cause
5. West Nile Virus: Mosquitoes transmit West severe symptoms, including fever, joint pain,
Nile virus, a viral disease that can cause and swelling
severe symptoms, including fever, headache,
and encephalitis.

CONTROL MEASURES:

1. Eliminate Breeding Sites: Eliminate and chemical controls to manage mosquito

standing water around homes and public populations.
areas to prevent mosquito breeding.
Biological Control Measures:
2. Use Insecticides: Use insecticides to kill
mosquitoes and their larvae. 1. Mosquito Fish: Introduce mosquito fish,
such as Gambusia affinis, to ponds and lakes
3. Wear Protective Clothing: Wear protective to control mosquito larvae.
clothing, including long sleeves and pants, to
prevent mosquito bites. 2. Dragonflies: Encourage dragonflies, which
feed on mosquitoes, to inhabit areas around
4. Use Mosquito Nets: Use mosquito nets to homes and public areas.
prevent mosquito bites while sleeping.
3. Mosquito-Repellent Plants: Plant mosquito-
5. Install Window and Door Screens: Install repellent plants, such as citronella,
window and door screens to prevent lemongrass, and basil, around homes and
mosquitoes from entering homes and public public areas.
areas.
Chemical Control Measures:
6. Use Mosquito Repellents: Use mosquito
repellents, such as DEET, picaridin, and oil of 1. Insecticides: Use insecticides, such as
lemon eucalyptus, to prevent mosquito bites. pyrethroids, organophosphates, and
carbamates, to kill mosquitoes and their
7. Implement Integrated Pest Management larvae.
(IPM) Strategies: Implement IPM strategies
that combine physical, cultural, biological,

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2. Larvicides: Use larvicides, such as Bacillus 3. Adulticides: Use adulticides, such as

thuringiensis israelensis (Bti), to kill permethrin, to kill adult mosquitoes.
mosquito larvae.

parts: head, thorax, and

abdomen

Head: Small, triangular head

with two large compound
eyes and two small
antennae

Thorax: Middle segment of the

body, bears six legs and
two wings

Abdomen: Long, segmented

abdomen with a
BUTTER FLIES
distinctive rounded tip

Wings: Two pairs of wings, with

the hindwings being
much smaller than the
forewings

Legs: Six jointed legs, each with

a claw at the end

Antennae: Two small antennae used

for sensing the
environment

IMPORTANCE

Body: Small, slender body

divided into three main

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Pollination: Butterflies are important Ecosystem Engineers: Some butterflies, such

pollinators of flowers, transferring pollen as the monarch butterfly, play a crucial role in
from one plant to another maintaining ecosystem health by pollinating
plants and dispersing seeds
Food Source: Butterflies are an important
food source for other animals, such as birds, Biological Control: Some butterflies, such as
bats, and spiders the cabbage white butterfly, are used as
biological control agents to control pest
population.

DESTRUCTIVE STAGE pppppppppppppppp

Caterpillar Stage: The caterpillar stage of a

butterfly's life cycle can be destructive to
plants, as they feed on leaves and other plant
material

Pupa Stage: The pupa stage of a butterfly's

life cycle can also be destructive to plants, as
they can damage plant tissue and cause
disease

ppppppppppppppppppppppppppppppppppp
ppppppppppppppppppppppppppppppppppp
ppppppppppppppppppppppppppppppppppp
ppppppppppppppppppppppppppppppppppp
ppppppppppppppppppppppppppppppppppp
ppppppppppppppppppppppppppppppppppp
CONTROL MEASURES

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Biological Control: Use natural enemies, Physical Control: Use physical barriers, such
such as parasites and predators, to control as fine-mesh screens, to prevent butterflies
butterfly populations from reaching

Cultural Control: Modify cultural practices, Resistant Varieties: Plant resistant varieties
such as pruning and irrigation, to reduce the of crops to reduce damage from butterflies
attractiveness of plants to butterflies
Traps: Use traps, such as sticky traps and bait
Chemical Control: Use insecticides, such as traps, to capture and remove butterflies from
pyrethroids and organophosphates, to control the area.
butterfly

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A TABLE SUMMARIZING THE IMPORTANCE

AND DANGERS OF THE ABOVE INSECTS:

Insect Import Useful Role Dangerous Dangers

ant Stage
Stage

Cockroach Adult Decomposition All stages Disease transmission

food source Contamination

allergies

Housefly Adult Pollination All stages Disease transmission,

decomposition contamination,

allergies

Termite Worker Decomposition All stages Property damage

ecosystem engineering economic loss

Mosquito Adult Pollination Adult Disease transmission

(malaria, dengue,
food source Zika)

Bee Adult Pollination Adult Stings

(defensive)
honey production allergic reactions

Butterfly Adult Pollination Caterpillar Plant damage,

ecosystem engineering economic loss

Grasshopper Adult Food source Nymph Plant damage

ecosystem engineering Adult economic loss

Ant Worker Ecosystem engineering All stages Property damage

food source economic loss

stings

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ROOTS

A root is a descending portion of the axis of the

plant and develops from the radical of the
embryo during germination.

KINDS OF ROOTS
FLOWERING PLANTS There are 3 main kinds of roots;

➢ Primary roots

These are the first roots to grow out of a seed as

an extension of the radicle.

➢ Secondary roots

These grow laterally from the primary roots

➢ Adventitious roots

These are roots that grow from the stems or

leaves and not as branches from either primary
or secondary roots. They are almost of the same
size.

TYPES OF ROOTS

1. Tap root system

These are plants that bear flowers. A typical This consists of a main root growing straight
flowering plant is composed of 2 systems: down wards from the radicle. It gives rise to side
roots called lateral roots. Tap root system is a
• Root system
characteristic of dicotyledonous plants.
• Shoot system

The two systems are made up of two categories

of organs i.e.

Reproductive organs: these produce fruits and

seeds. They are directly involved in the
reproduction of the plant.

Vegetative organs: these are not directly

involved in the reproduction. They include roots,
stems and leaves.

Structure of a flowering plant

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v) Some roots are modified for breathing e.g.

white mangrove.

MODIFIED ROOTS

1. Storage roots

These are thick fleshly and succulent fruits. They

contain stored food like sugar and starch. The
roots are modified as root tubers e.g. carrots,
cassava and sweet potato roots.

2. Fibrous root system

This is the root system without a main root and

all roots arise from the same point of the base
of the stem. The roots are almost of the same size
and a characteristic of monocotyledonous plants.
2. Breathing roots

These are found on some plants growing in

swampy areas e.g. white mangrove. Its roots
grow up through the mud to the air. The root
parts above the mud are spongy and absorb air
from the atmosphere. The main root of such
plants bears branch roots.

Functions of roots

i) They anchor the plant firmly in the soil.

ii) They absorb water and mineral salts from
the ground to the plant.
iii) They conduct the absorbed water and
mineral salts up to the stems and leaves.
iv) In some plants, roots are modified into
root tubers which store food e.g. cassava. 3. Stilt roots
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These roots develop from the main system from They provide extra support to the plant by
certain plants such as red mangrove which grow anchoring it firmly in the soil.
in muddy areas. Stilt roots provide additional
support to the plant.

6. Clasping roots

These are roots growing from the nodes of

climbing stems such as figs (mituba trees),
vanilla and orchids. They secret a sticky
substance which dries up in air. This helps such
plants to cling on to other plants for support.
4. Prop roots

These are found growing on plants such as maize,

sorghum and sugar canes. They develop from
the nodes of the stem close to the soil surface.
They provide extra support by holding the
plant firmly to the soil surface.

7. Epiphytic roots

These grow on certain plants called epiphytes.

5. Buttress roots Epiphytes are plants which grow and get support
from other plants. These roots hang freely in the
These are large thick roots growing from the base
atmosphere. They absorb moisture from the
of certain stems e.g. Mvule trees, silk cotton, etc.
atmosphere.
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i) They hold leaves in the best position for

receiving enough sun light needed in the
process of photosynthesis.
ii) They conduct water and mineral salts from
roots to leaves and manufactured food from
leaves to other parts.
iii) They hold flowers and fruits in good position
so that they can be easily pollinated or
dispersed.
iv) When stems are young, they carry out
photosynthesis thus making food for the
plant.
v) Stems have lenticels (pores) that facilitate
gaseous exchange.
8. Sucking roots b) Secondary functions
i) Some stems may specialize in storing
These are roots found growing on certain food and water e.g. stem tubers like
parasitic plants e.g. figs (mituba). They grow corms, Irish potatoes, rhizomes and sugar
from the stem and penetrate the host plant. cane.
These roots absorb water, mineral salts and ii) Protect a plant against browsers by
organic food compounds from the host plant. forming thorns, spines or prickles.
iii) Vegetative reproduction or propagation
through the stem cuttings e.g. cassava and
sweet potatoes.
iv) They support the plant by climbing stem
STEMS tendrils e.g. pisum pea (wild pea).
This is the ascending portion of the plant axis that
develops from the plumule of the embryo. It has
the following characteristic features;
TYPES OF STEMS
➢ It bears leaves at the nodes. 1. Erect stems
➢ It has nodes and internodes.
These can support themselves in an upright
➢ It has buds in the axills called axillary buds.
position. They may be woody or herbaceous.
➢ It has flowers or fruits.
➢ Its terminal bud is located at the tip of the 2. Weak stems
stem.
These can’t support themselves upright but
NB: the axill is the angle between the leaf and the either creep or climb for support.
stem.
3. Underground stems
FUNCTIONS OF STEMS
These are modified stems which remain
a) Primary functions permanently underground. They are often
swollen and serve as food storage organs.
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Woody stems stems. They may be modified at axillary buds e.g.

in passion fruit plants or terminal buds.
These have a high content of lignin and are hard.
They are found in shrubs and trees. 3. Creeping stems (creepers)

Herbaceous stems These are long thin stems which grow along the
surface of the ground, giving off roots at certain
These contain no or less woody materials e.g. intervals of the nodes. Four types of creeping
tomatoes, rice. The herbs are shorter than grass. stems are;
NB: a) Runners
This is a slender trailing stem lying flat on the
• Annual herbs only live for one year
ground possessing long internodes. A runner
• Bi – annual herbs live for two years
arises as an axillary bud and creeps some
• Perennial herbs live for many years
distance away from the mother plant and
MODIFICATION OF STEMS grow into another plant e.g. oxalis.
b) Offset stems
Weak stems
This is a horizontal thickened short stem. It
1. Twinning stems (twinners) originates from the axile of the leaf and grows flat
on the ground. It produces many leaves above
These are stems that grow ascending spirally
and a cluster of roots below e.g. water hyancith
around a support. They are usually long and
and water lettuce.
slender e.g. Dutch man’s pipe and lianas.
4. Sucker

A sucker is a creeping stem that grows obliquely

upwards, directly giving rise to a leafy shoot. E.g.
banana, pineapple, sisal plant, etc.

Underground stems

There are four types of underground stems

namely:

• Rhizome
• Corm
• Stem tuber
• Bulb
1. Rhizomes

This is a horizontal thick underground stem

2. Climbing stems having adventitious roots growing from the
These are stems that grow clinging to the support lower side of the nodes. It has terminal buds
of other plants by means of tendrils. Tendrils are which develop into aerial shoots. It bears buds in
thin wire-like spirally coiled branches of certain
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axils of the reduced brown leaves called scale and somehow flattened from the top to bottom. It
leaves. has a terminal bud lying at the top of the stem and
has scale leaves a rising from the nodes. Its roots
Rhizomes store a lot food for the plant. Some also grow randomly from the stem. Examples of
act as organs for vegetative propagation e.g corms are cocoyams crocus and yams.
ginger, canalily, couch grass and Solomon’s seal.

2. Stem tubers

This is a short, fleshy underground stem swollen

with large amounts of stored food. It has scale
leaves and axillary buds which form the “eyes” e.g
Irish potato, yams.

3. Bulb

A bulb is short conical-shaped underground stem

comprising of thick fleshy leaves arranged in
concentric circles. The thick fleshy leaves store
food for the plant and are protected by outer dry
brown leaves called scale leaves.

A terminal bud lies at the top of the stem and give

rise to the aerial shoot. Axillary buds are situated LEAVES
between the leaf bases. Onions, garlic, tuberose,
etc. are bulbs.

Structure of an onion

4. Corm

A corm is a swollen fleshy underground stem that

grows in a vertical direction. It is round-shaped

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External structure of a leaf

A leaf is a thin flattened structure which grows

from the nodes of a stem or its branches and has
a bud in its axil. Leaves are generally green
although some are red or brown. The leaf is made Texture of lamina; the lamina may be hairy or
up of 3 main parts; smooth. It may be hard or soft.
Petiole; the leaf stalk is a characteristic of dicots
Leaf base; this is the part which attaches the leaf while a leaf sheath is found in monocots. The leaf
to the stem. stalk/sheath can be hairy or smooth.

Petiole; this is the part which connects the leaf VENATION

base to the leaf blade. Leaves with a petiole are
called petiolate and those without are called The arrangement of veins in the lamina of a leaf is
sessile. called venation. Two broad types of venation are;

Lamina; this is the expanded and flattened 1. Network venation or reticulate

portion of the leaf consisting of veins and midrib. 2. Parallel venation
➢ Network venation
Functions of leaves to plants
In network venation, the veins in the lamina
a) Primary functions branch while intersecting to form a network. It’s
• The major function is to manufacture food for a characteristic of dicots.
the plant during photosynthesis.
• Leaves have stomata which allow exchange of
gases i.e. O2 and CO2.
• Leaves facilitate transpiration which
sometimes helps the removal of excess water
within the plant.
b) Modified or secondary functions
➢ They store food and water for the plant e.g.
the thick fleshy leaves of onions.
➢ Some plant leaves are useful in vegetative
reproduction e.g. bryophytes. ➢ Parallel venation
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In this venation, the veins run side by side

without branching. This is a characteristic of
monocotyledonous plants. CLASSIFICATION OF LEAVES

Leaves can be classified according to whether the

leaf lamina is completely divided or not divided.
ARRANGEMENT OF LEAVES ON A STEM Two broad types are:

Arrangement is the insertion of leaves on the • Simple leaves

stem. Leaves develop at the nodes in the stem and • Compound leaves
are arranged in different ways.
Simple leaves
1. Alternate
A simple leaf has a single lamina which isn’t
This is when one leaf only arises from each node divided up into leaflets e.g. Avocado, mango,
and the nodes are at different levels and the orange, hibiscus, pawpaw, cassava, etc.
successive nodes are at different nodes.
Cassava and pawpaw leaves are partly divided.
The lobes are not considered to be leaflets
because the divisions do not reach down the
midrib. They are simple digitate i.e.

Simple leaf of a mango

2. Opposite

This is when two leaves arise from nodes that are

opposite each other and are at the same level.

Simple leaf of cassava

3. Whorls

This is where more than 2 leaves arise from each

node.

A swelling at the base of the leaf stalk is called

pulvinus e.g. beans and cassava. Some leaves
have it while others do not have it.

Compound leaves
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A compound leaf has a lamina which is 3. Compound digitate leaves

completely divided into leaflets. They resemble
leaves but are not leaves because the axillary These are compound leaves with leaflets
buds are absent in the axis of leaflets e.g. beans, radicating out from the end of the petiole-like
oxalis, cassia, etc. fingers of the hand.

Types of compound leaves 4. Compound trifoliate leaves

1. Compound pinnate leaves These are compound leaves with only 3 leaflets.
They include soya beans, oxalis and straw berry.
These are compound leaves with leaflets
arranged either in pairs opposite one another or NB: stipules (foliar appendages) are attached to
alternately along the midrib called rachis of the the leaf base or petiole e.g. in beans, hibiscus and
leaf. If the terminal leaflet is present, the leaf is cassia.
said to be imparipinnate and if the terminal TYPES OF LEAF MARGINS
leaflet is absent, the leaf is said to be paripinnate.
Leaves can be classified according to the leaf
Imparipinnate margins.

6. Entire margin
The margin is smooth and without
indentation of any kind. E.g. mango leaves.
7. Serrate margin
The margin is with indentations pointing
towards the apex.
8. Dentate margin
The margin has indentations pointing
towards the petiole.
9. Crenate margin
The margin has round indentations.

10. Lobed margin

The margin has relatively few and shallow
indentations.

2. Compound bipinnate leaves

TYPES OF LEAF SHAPES
These are compound leaves with 2 orders of
leaflets. Leaflets are further divided up to form
leaf-like structures called pinnules e.g. jacaranda.
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4. Insectivorous leaves

These are modified leaves whose function is to

capture and digest insects. Such plants are called
insectivorous plants. Pitcher plants grow in soil
with a deficiency of nitrogen/nitrates. They
obtain nitrogen from insects. E.g. Venus fly trap,
butter wort, sundew, bladder wort, nepenthes,
and the pitcher.

5. Bryophyllum leaves

Leaves have series of buds at the end of vein.

These buds grow into new plants (plantlet) when
the leaf is mature.

MODIFICATION OF LEAVES

Leaves of some plants have become modified to

perform other functions other than
photosynthesis.

1. Leaf tendrils

These are slender wire like coil structures used

as climbing organs in climbers for support. The
leaf may be partly modified into a tendril.

2. Leaf spines

These are sharp pointed structures of certain

plants modified for defense.

3. Scale leaves

These are thin, dry membranous structures

usually brown in colour and sometimes
colourless. Their main function is to protect the
axillary bud from mechanical injury and drying THE FLOWER
out. They are commonly found on underground
stems. E.g. scale leaves of onions, rhizome and
garlic.

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contain pollen grains which develop to form

male reproductive cells called gamates.

N.B: an infertile or sterile stamen is called

staminode.

Gynoecium (pistile) is made up of female

reproductive parts called carpels. The pistil
occupies a central position in the flower. Each
carpel is made up of;

✓ Ovary which contains ovules or

female gamets.
✓ Style which connects the ovary to the
stigma
✓ Stigma which receives the pollen
Parts of a flower grains
The floral parts are arranged in rings, spirals or The wall of the ovary develops into the pericarp
whorls with short internodes. The end of a flower of the fruit. Nectaries are swellings often at the
stalk may be expanded to form a receptacle. The base of the ovary or on the receptacle which
stalk of the flower where floral parts grow is produce a sugary solution called nectar.
called pedicel.
POLLINATION
The four floral whorls are
Pollination is the transfer of pollen grains from
➢ Calyx the anther to the stigma of a flower. There are two
➢ Corolla types of pollination.
➢ Gynoecium
➢ Androecium 1. Self-pollination. This is the transfer of
pollen grains from the anther to the
The calyx is the outer most floral whorls of stigma of the same flower or between two
the flower made up of sepals. The calyx flowers on the same plant.
protects the inner whorls of a flower during 2. Cross-pollination. This is the transfer of
the bad stage. pollen grains from the anthers of one
flower to the stigma of another flower on
The corolla is the second floral whorl of a
a different plant but of the same species.
flower made up of petals. Most flowers have
scented petals to attract insects for
Agents of pollination
pollination e.g. hibiscus, crotalaria, coffee,
These are things that aid the process of
morning glory, etc. the calyx and corolla are
pollination. The agents of pollination include.
collectively known as perianth.
Animals, Water, Wind and Artificial pollination
Androecium is the male part of the flower
consisting of stamen. Each stamen is made up There are however two major agents that is wind
of filament and head called anther. Anthers and insects. Pollination can therefore be

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described as wind pollination and insect Produce nectar from Produce no nectar
pollination. nectarines

Characteristics of insect pollinated flowers. Have large petals Have small petals

1. They have brightly coloured petals to Produce few pollen Produce a lot of pollen
attract insects. grains grains
2. They have a scent to attract insects
3. They have large conspicuous petals, Have sticky stigmas Have feathery stigmas
which act as landing sites for insects.
Produce heavy pollen Produce light pollen
4. They have sticky pollen grains, which
grains grains
stick to the insects body.
5. They have sticky stigmas, which hold Have short pistils Have long pistils
pollen grains.
6. They produce few sticky pollen grains. Have short stamens Have long stamens
7. They produce heavy pollen grains.
8. They produce nectar from nectarines to
attract insects. Characteristics of flowers pollinated by
Characteristics of wind pollinated flowers. nocturnal insects
1. They have dull coloured petals. Nocturnal insects are those insects, which are
2. They have small petals. active at night. Flowers pollinated by such insects
3. They produce light pollen grains, which have the following characteristics.
can easily be carried by wind.
4. They do not produce nectar 1. They have light coloured petals mainly white
5. They have feathery stigmas to trap pollen and pink.
grains carried by wind. 2. They produce a strong scent.
6. They produce a lot of pollen grains. 3. They open their petals at night and close
7. They have no scent them during daytime.
8. They have long stamens and pistils
hanging outside the petals to release and
receive respectively pollen grains easily. Modifications of flowers to prevent self-
pollination

Differences between insect and wind 1. Protandry. This is a situation where stamens
pollinated flowers. ripen before the stigma such that when
pollination occurs, the pollen grains cannot
Insect pollinated Wind pollinated germinate on the immature stigma.
flower flower 2. Protogyny. This is a condition where the
stigma ripens before the anthers.
Have brightly Have dull coloured 3. Dioecious condition. This is a condition
coloured petals petals where a plant bears either pistilate or
staminate flowers but not both.
Have a scent Have no scent

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4. Self-incompatibility. This is where pollen

grains from the same flower fail to fertilize
the stigma of that flower.
5. Structure of the flower. Sometimes the
carpel is taller than the stamens of the same
flower and in some flowers the corolla covers
the stamens preventing self-pollination.

Longitudinal section through a bean seed

SEEDS

A seed is a fertilized mature ovule. It has one scar

called hilium which is a spot where it was
attached to the pod inside a fruit.

Types of seeds

Monocotyledonous seeds

These contain only one seed leaf or cotyledon. E.g.

cereals like maize.

Structure of a maize grain Testa

It is a protective -covering of the embryo of the

seed formed from the integuments. It is usually
hard and dry. It protects it from fungi, bacteria
and insects.

Tegmen

It is the inner membrane of the seed coat and its

also used for protection.

Micropyle
Dicotyledonous seeds
It is a narrow opening into the seed through
These contain 2 cotyledons e.g. legumes like which water, mineral salts and oxygen enter
beans, peas and G. nuts. during germination.

Structure of a bean seed Radicle

It is a seed root (embryo root) which develops

into primary root of the plant. A developing root
has a root cap which bores through the soil
particles and protects the newly formed cells at
the root tip from mechanical damage.

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Hilium True fruits: develop only from the ovaries of a

flower e.g. beans, tomatoes, etc.
It’s a scar of attachment left by the stalk of the
ovule to the ovary wall. False fruits: develop from the association of
ovaries and other floral parts such as receptacle.
Endosperm Examples include; pineapples and apples.
Stores food especially starch for the embryo. Classification of fruits
Scutellum or cotyledon There are 3 groups of fruits namely;
Digests and absorbs food stored in the ❖ Simple fruits
endosperm. It provides food to the whole seed. ❖ Aggregate fruits
Coleorhiza ❖ Multiple fruits

It is the radicle sheath that offers protection to Simple fruits

the radicle. These are formed from one flower in which the
Coleoptile pistil consists of either one carpel (monocarpic)
or of several fused together (syncarpous) e.g.
It is the plumule sheath that offers protection to legumes, g, nuts, peas, tomatoes, mango, beans,
the plumule. etc.

Cotyledon Aggregate fruits

These contain stored food like starch, proteins These are formed from one flower in which the
and liquids for the initial growth of the embryo pistil consists of several free carpels
during germination. (apocarpous) e.g. apples and rose.

FRUITS Multiple fruits

A fruit is a fully grown fertilized ovary containing These are formed from several flowers and the
one or more seeds. A fruit has 2 scars, one where ovaries become fused after fertilization e.g.
it was attached to the receptacle and the other, jackfruit and pineapple.
the remains of the style or stigma.
SIMPLE FRUITS
During a fruit formation, the wall of the ovary
becomes a fruit wall called pericarp. In some There are either dry or succulent according to
fruits such as banana and pine apple, the fruits whether the pericarp becomes dry or juicy as the
develop without fertilization. Such fruit are said fruit ripens.
to be parthenocarpic fruits. Therefore, Types of simple fruits
parthenocarpy is the development of fruits
without fertilization. Simple fruits are further divided into three
categories.
Classes of fruits
1. Dry indehiscent fruits
2. Dry dehiscent fruits
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3. Succulent fruits. grasses and

Dry indehiscent fruits maize.

These are fruits with a dry pericarp that does not Cypsela This is a fruit Cypsela of
split up (dehisce) to release seeds. This category similar to an tridax.
contains five types of fruits. These are Achene, achene in which
Nut, Caryopsis, Cypsela and Samara. the inferior ovary
has a pappus of
THE TABLE BELOW SHOW THE DIFFERENT TYPES
persistent calyx.
OF DRY INDEHISCENT FRUITS.
It is common in
composite fruits,
e.g. tridax and
Type of dry Description Illustrative bidens pilosa
indehiscent diagram
fruit Samara. This is a fruit Samara of
similar to an jacaranda.
Achene This is a one An achene achene in which
seeded fruit of the pericarp is
covered by a dry sunflower. extended to form
pericarp, which one or more
does not split wings, e.g. in
open, e.g. jacaranda and
sunflower. The African rose
achene is the wood.
simplest fruit.

Nut. This is similar to Section

an achene but the through a Dry dehiscent fruits
pericarp is hard cashew
and tough, e.g. nut These are fruits with a dry pericarp that splits
(dehisces) to release seeds. The fruits split at
cashew nut.
particular lines of weakness known as sutures.
Note; coconuts These fruits are categorized into the following
and groundnuts different groups depending on the number of
are biologically splits that occur on the pericarp. These fruits
not nuts. include, Follicles, Legume, Capsule and
Schizocarp.
Caryopsis. This is an achene- Caryopsis
like fruit in which of maize. THE TABLE BELOW SHOWS THE DIFFERENT TYPES
OF DRY DEHISCENT FRUITS.
the testa and
pericarp are
fused. These are
mainly found in
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Type of Description Illustrative sweet hearts

dehiscent diagram and some cassia.
fruit

Follicle This is a dry fruit Sodom

with many seeds apple.Split/sutur
and splits open e in fruit Seeds
along one wall
suture, e.g. Succulent fruits
Sodom apple These are fleshy fruits. They are either entirely
fleshy or have part of it fleshy. They are further
divided into 2 types.

Legume. This is a dry fruit Legume of a 1. Drupes.

with many seeds bean These are fruits with only one seed and only part
and splits open of it fleshy (epicarp and mesocarp). The endocarp
along two is fibrous and hard, e.g. mango and avocado.
sutures, e.g.
beans, peas, Longitudinal section through a mango.
flamboyant and
Barbados pride.

Capsule This is a dry fruit

with many seeds
and splits open
2. Berry.
along many
This is a fruit with many seeds and the whole of it
vertical slits. It is
fleshy, e.g. tomatoes, guavas, oranges, bananas
formed from an
etc.
apocarpous
flower, e.g. A berry of an orange (T.S).
Dutchman’s
pipe, balsam,
cotton, e.t.c.

Schizocarp. This is a dry Schizocarp

several seeded of
fruit, which desmodium.
breaks up into

separate parts
each containing
one seed, e.g.
desmodium,

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PLACENTATION the
projection
This is the distribution of the placentae in the from the
ovary or the arrangement of the seeds on the base of a
placenta within the ovary. one
There are five types of placentation as shown in chambered
the table below. fruit

Type of Description Example Basal Ovule found Mango,

Placentation on a avocado.
placenta
Marginal Ovules are Beans, that arises
situated at peas, from the
or near the cassia base of the
margin of ovary, fruit
the ovary usually
single
Axile Ovules Orange
seeded
centrally and
located in tomato
the ovary
with ovary
divided into
FRUIT/SEED DISPERSAL
many
chambers. This is the scattering or spreading/displacement
of fruits and seeds from their parent plants. In
Central Ovary is one Soap
some plants, only seeds are dispersed while in
chambered wort,
others, fruits are dispersed with seeds.
and ovules
centrally Importance of dispersal
located
i) It helps to prevent overcrowding among
Parietal Placenta is Passion plants of the same species.
found on fruits ii) It reduces competition between member
the inner pawpaw, plants of the same species.
wall of the cocoa iii) It helps to minimize the spread of
fruit and the epidemic diseases especially in seedlings
ovules are if they are crowded.
attached on iv) It helps plants to colonize new areas
the inner which may even be better for the species
wall survival.
v) It enhances the chances of survival and
Free central Ovules Green
continuity of the plant species.
located on pepper
Agents of dispersal

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They include; ii) Some fruits when ripe are scented e.g.
1) Water, jack fruit. This helps to lure/attract
2) Wind animals.
3) Animals iii) Some usually possess edible parts
4) Self-dispersal/ explosive mechanism which are succulent / juicy and the only
part of the fruit that is eaten and the
Fruits and seeds possess specialized structure to rest containing the seeds is thrown
aid their dispersal and are adopted to specific away e.g. mango and avocado.
mode of dispersal. iv) In some fruits, such as guavas,
Characteristics of fruits/seeds dispersed by tomatoes, pepper and pawpaw. The
wind whole fruit is eaten and the seed passed
out in the faeces because of their
➢ They are usually small, light and dry which resistance to digesting i.e. are
enables them to easily be carried or flown indigestible.
by wind. v) Some fruits e.g. Biden pilosa and
➢ Some fruits like elm and tecoma have wing desmodium possess hooks and sticks in
like structures that increase their surface the hair of passing animals. They stick
area. This helps in delaying the fall of seeds in the fur of animals or on clothing of
and fruits and increases chances of being people.
blown away.
➢ Some fruits like tridax and clancletion have
parachute-like hairs called pappus which
enables them to fleet and fly by wind.
➢ Some seeds like silk cotton possess thread-
like structures called floss which increase
surface area enabling the seeds to float in
air.

Characteristics of fruits/seeds dispersed by

water

i) They are usually light and contain air

space inside which reduces their
relative density and enable them float
on water easily like the coconut.
ii)

Characteristics of fruits/seeds
dispersed by animals

i) Some fruits such as tomatoes, oranges

and mangoes are usually large and
brightly coloured especially when ripe.
This helps to attract animals.

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