BIOLOGY

Grade 1 Secondary

Student Book

2013 / 2014
Book cover

Expresses the human blood cells

 BIOLOGY
Grade 1 Secondary

Student Book

Authors

Dr.Nawal Mohamed Shalaby Mr: Hassan Alsayed Moharram

Dr.Hany Nady Youssef

Supervision
Mr. Mohamed Reda Aly Ibrahim

2013 / 2014

Center For Curriculum & Instructional Materials Development

 Introduction
Dear Student:
Biology is one of the natural sciences. It concerns with studying the life and its evolution.
It also aims at developing our understanding of all living organisms. It deals with the study
of organisms in terms of their structures, functions, evolution, vital processes, interactions
between organisms with each other, and between organisms and the environment where they
live. Biology is an experimental science follows the processes of science and based on accurate
experimental and scientific results and observations.
According to the nature of biology and using its processes, this book and the accompanied
activity notebook introduce you a number of main topics which allow you to understand the
organisms in terms of their structures, properties, classification and evolution. These topics
also provide you with several and various opportunities to do the practical experiments and
activities that help you discover the basic principles as well as develop the skills in research
and investigation.
Student›s Book and activity notebook include five main chapters. Each of them contains
a number of lessons starting with the chemical basis of life which allows you to understand
and interpret the structures of organisms and the reactions performed in them according to the
chemical basis. Then the accurate ultrastructure of the cell to give you the cellular theory. You
identify the ultrastructure the cell organelles. The next chapter discusses the (heredity) genetics
to discover some basic genetic concepts which allow you to explain some of the daily life
phenomena. The fourth chapter helps you classify the organisms according to the properties
which these organisms have. Finally, this book introduces you the evolution and diversity of
organisms where you recognize the different mechanisms of evolution and their evidences to
help you adopt the explanatory points of views based on scientific knowledge.
Each chapter ends in modern biotechnological applications related to biology. These
applications allow you to identify the relationship between science and technology in this field.
There are fundamental considerations that must be regarded as you study this curriculum.
These considerations are that the student›s book and activity notebook are complement to each
other. Each of them has an essential role in developing your knowledge, skills and scientific
values. The student›s book is not the only source for knowledge, as a result, you should refer
to other sources such as specialized scientific books and magazines, and Internet to get more
knowledge.
As we introduce this book, we hope it to be helpful for success, excel, and for more
research and study to achieve the objectives.

God ggone success

Authors
 Contents

Unit One : Chemical basis of life

Chapter 1 : Chemical Structure of Living Organism’s
Bodies (Carbohydrates and lipids) 2

Chapter 2 : Chemical Structure of Living Organism`s

Bodies (Proteins and Nucleic acids) 9

Chapter 3: Water 15

Chapter 4 : Chemical Reactions in Organisms’ Bodies 20

Unit Two: Cell: structure and function

Chapter 1 :Cell theory 30

Chapter 2 :Cell ultrastructure 35

Chapter 3 :Differentiation of cells and diversity of

plant and animal tissues 47

Chapter 4 :Cell Processes 52

 Unit Three :Inheritance of Traits
Chapter 1:Chromosomes and genetic information 62

Chapter 2: Genes interaction 70

Chapter 3: Genetic inheritance and genetic diseases 79

Unit Four : Classification of living organisms

Chapter 1:Principles of living organisms classification 94

Chapter 2: Modern classification of living organisms 98

Chapter 3: Kingdom Animalia 106

Unit Five: Biological evolution

Chapter 1:Origin of living organisms and mechanisms of

their evolution 128

Chapter 2: Evidence of evolution occurrence 136

 Unit One

Chemical basis of life

Biology is closely related to chemistry. Chemistry explains the chemical structure

of living organisms and the reactions taking place inside their cells.
There are four basic types of organic molecules necessary to the life of living
organisms. These molecules are carbohydrates, proteins, lipids, and nucleic acids.
All living organisms are made up of these four molecules. These four molecules are
called the biological macromolecules.
In this unit, you will identify the molecular structure, functions and importance
of these molecules to the living organisms. Furthermore, you will identify the
chemical processes related to the functions of life.
In this unit, you will practise some practical and applied activities that help you
to understand the nature , structure and functions of the biological macromolecules
and the chemical reactions which occur inside the cells. These activities improve
some of your skills such as observations, experimentation, measurement, conclusion,
interpretation, controlling the variables and so on.
.

For m net.
ore inf
ormatio l og in the
na bout the topic of chemical basis of life,
 Time management
To achieve the maximum benefit of this unit, you need to:
• Manage your time among practical and theoretical study, research and the
expansion of information resources.
• Carefully, record the results of your practical study because they are the ideal
way to support your learning.

Learning outcomes:
By the end of this unit, the student should be able to:
• Determine the substances from which the living • Describe the structure of the water molecule.
organism’s body are made up of. • Determine the properties of water on which living
• Describe the molecular structure of carbohydrates, organisms depend.
lipids, proteins, and nucleic acids. • Determine what is meant by metabolism in living
• Determine the functions of carbohydrates, lipids, organisms (catabolism and anabolism).
proteins, and nucleic acids. • Determine what is meant by enzymes and mechanisms
• Explain the role of monosaccharides in the processes of and principles of their functions.
transferring energy inside the cells of living organisms. • Identify the pH of some solutions.
• Explain the relationship among the sequence of amino • Explore the effect of the pH on the enzymes activity.
acids in the polypeptide chains, and the structure and • Clarify the effect of temperature on the enzyme activity
variation of the proteins. practically.
• Identify the primary, secondary, tertiary and quaternary • Appreciate the grandeur of Allah for the accurate
structure of proteins. structure of living organisms’ bodies.
• Identify carbohydrates, lipids, and proteins practically.

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 Unit One
Chapter 1
Chemical Structure of Living Organism’s Bodies

(Carbohydrates and lipids)

By the end of this chapter, you

should be able to: You know that the structure of living organisms
• Determine the substances from which comes in gradual levels. These levels begin with the
the living organism’s body is made up of.
• Describe the molecular structure of systems, organs, tissues, cells and finally come the
carbohydrates and lipids. organelles.
• Determine the functions of carbohydrates
and lipids. If we follow up this structural sequence of living
• Explain the role of monosaccharides in
the processes of transferring the energy
organisms, we will find that the cells of any living
inside the cells of living organisms. organism are made up of organic and inorganic
• Identify carbohydrates and lipids
practically.
molecules and each of these molecules is made up of
• Propose scientific hypotheses and do atoms as well.
experiments to verify their validity.
Inorganic molecules in living organisms such as
water and salts often do not contain carbon atoms.
While organic molecules such as carbohydrates,
lipids, proteins, and nucleic acids are large molecules
containing carbon and hydrogen, and called biological
macromolecules.
Terms:
• Carbohydrates
• Monosaccharides
• Disaccharidase
• Polysaccharides
• Lipids

.
Figure 1: Sucrose molecule is one of the biological macromolecules.

Use the colour key attached to figure 2 to identify the cell orga-
nelles that made up of:

(Carbohydrates-lipids - proteins -and nucleic acids).

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 Carbohydrates

Proteins

Lipids

DNA

RNA

Figure 2

Observe figure 3 to see that carbohydrates, lipids, proteins , and nucleic acids
are made up of units. Each unit is made up of smaller units. Identify the units from
which all the four biological macromolecules (carbohydrates, proteins, lipids, and
nucleic acids) are made up of.

Starch
Monosaccharide Chloroplast Amino acid Polypeptide Protein fibre

Fatty acid Fats

Fat cells DNA
Nucleotide Chromosome

Figure 3: The units from which the four biological macromolecules are made up of.

Biological macromolecules
Biological macromolecules are large-sized organic compounds made up of
smaller molecules. All these compounds contain the carbon element and they
are extremely necessary for the life of living
organisms.
Enrichment
Most biological macromolecules are
Biochemistry: is the science
called polymers. Polymers are made up of
concerning with studying the
the combination of smaller molecules called chemistry of living organisms. .
monomers throughout a process called
polymerization.

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 Biological macromolecules are divided into four groups according to their
molecular structures and the functions they perform.

Carbohydrates
Carbohydrates are biological macromolecules made up of smaller molecules
called monomers. Carbohydrates include sugars, starches and fibres. They are
symbolised by the formula (CH2O)n. According to this formula, carbohydrates are
made up of carbon (C), hydrogen (H) and oxygen (O) atoms in the ratio 1:2:1.

Importance of Carbohydrates:
✲ Carbohydrates and obtaining energy: Carbohydrates are considered the fast
and basic resources for obtaining the energy.
✲ Carbohydrates and storing energy: Carbohydrates are used for storing energy
in living organisms’ bodies until they require it. Plants store carbohydrates in the
form of starches. On the other hand, the carbohydrates are stored in the human
body and animal’s body in the form of glycogen in the liver and muscles.
✲ Carbohydrates and building the cells: Carbohydrates are a basic component
for some parts of the cell such as cellulose in the root of plant cells. Additionally,
carbohydrates are also found in cell membranes and in the protoplasm of the
cell.

Molecular structure of carbohydrates:

There are several ways to classify carbohydrates. Some of these classifications
are based on the molecular structure of these carbohydrates. They can be divided
into:
➠ Simple sugars:
✲ It’s chemical composition is made up of either one of sugar
CH2OH
molecules and called monosaccharides or made up of two
H C O H
molecules of monosaccharides linked together to form a
H
molecule of disaccharidase . C C
OH H
✲ Monosaccharides HO C C OH
Monosaccharides are the simplest type of sugars. They are H OH
made only up of one molecule. This molecule is made up of
Figure (4): Glucose is one
a chain of carbon atoms. Each carbon atom is connected to of the monosaccharides.
oxygen and hydrogen atoms in a certain way. The number of
carbon atoms in monosaccharides ranges from 3-6 atoms.
• Examples for monosaccharides are glucose (fig.4), fructose, galactose, and
ribose.

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✲ Disaccharidase
✲ Two monosaccharides molecules are linked to each other to form a
disaccharide molecule. Examples for disaccharidase are sucrose, which is made
up of a glucose molecule linked to a fructose molecule, lactose which is made
up of a glucose molecule and a galactose molecule and maltose which is made
up of two glucose molecules.

CH2OH Glucose Fructose

H C O H HOCH2 O H
H
C OH H C C H HO C
OH C C O C C CH2OH
H OH OH H

Figure 5: Sucrose is one of disaccharides

In general, simple sugars are soluble in water, have a low molecular weight and
have a sweet taste.
✲ Role of monosaccharides in the processes of transferring energy inside the
cells of living organisms.
Living organisms obtain energy stored in carbohydrates when the glucose
molecules are oxidised inside the cells (mitochondria) and the energy stored in its
chemical bonds released in the form of a compound called adenosine triphosphate
(ATP). This compound is transferred into other places in the cell to use the stored
energy in it for all the vital processes inside the cell.
Second: Complex sugars
Complex sugars are polysaccharides made up of monosaccharides such as
starch, cellulose and glycogen. Each of them is made up of glucose molecules
combined with each other. Complex sugars are insoluble in water, have high
molecular weight, and do not have sweet taste.

CH2OH
C O
H H
H
C H C
OH
OH OH
C C
H OH
Monosaccharide
Figure 6: Complex sugars are made up of several monosaccharides

Be interconnected with the activities and exercises book: Practical activity: Detecting sugar - Applied
activity: combating obesity

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 Lipids
Lipids are biological macromolecules made up of carbon, hydrogen and oxygen
atoms. Lipids are also made up of a large group of heterogeneous compounds such
as fats, oils, waxes, phospholipids and the derived lipids such as steroids. All these
compounds are insoluble in water, but they dissolve in the nonpolar solvents such
as benzene and carbon tetrachloride.

Molecular structure of lipids:

Observe figure 7 to see that the lipids are
Fatty acid 1
made up of fatty acids, and glycerol. Glycerol is
an alcohol containing three hydroxyl groups (OH).

Importance of lipids Fatty acid 2

✲ Lipids and obtaining energy:

However, carbohydrates are a rapid resource
Fatty acid 3
of energy, the energy obtained from lipids is more
than the energy obtained from the same amount of
Figure 7: A diagram illustrating the
carbohydrates. The body does not begin to get the molecular structure of lipids
energy from the fats stored in it, only in case of the
absence of carbohydrates.
✲ Lipids and building the cells
Lipids represent about 5% of the organic
materials involved in the composition of the
living cell. Lipids also have an important role in
the structure of cell membranes.
Furthermore, lipids work as a thermal insulator
in animals and humans. Due to the favour of
lipids, organisms can maintain their temperatures Figure 8: Lipids form an isolating layers
under the skin
in severe cold regions. Besides, lipids can work as
a protective cover for the surfaces of several plants and animals, and some of them
can work as hormones as steroids.

Classification of lipids:
According to the chemical structure, lipids are classified into:
Simple lipids
Simple lipids are formed by the reaction of fatty acids with alcohols. According
to the saturation degree of the fatty acids and the type of alcohol, simple lipids are
divided into:

6
 A Oils:
Oils are liquid fats formed by the reaction of
unsaturated fatty acids with glycerol and called
triglycerides. Examples for simple lipids are the
liquid fats covering the feathers of water birds to
prevent water penetration into their bodies, figure 9.
Figure 9: Feathers of water birds

B Fats:
Fats differ from oils in the aspect of being solid Enrichment
substances. Fats are formed by the reaction of
Risks of the takeaway food
the saturated fatty acids with glycerol and also
Ready meals, fried food, and many
called glycerides.
bakeries and sweets contain a type
of fat called trans fat that produced
by hydrogenation of vegetable oils.
C Waxes Frequently eating of these fats leads to
elevation of cholesterol concentration in
Waxes are made up by the reaction of fatty acids
blood.
of high molecular weight with monohydric
alcohols. For example, the waxes covering the
desert plant leaves to reduce water loss during the transpiration.

Figure 10: The wax covering the plant leaves.

✲ Complex lipids
Hydrogen, carbon and oxygen are involved in the structure of complex lipids,
in addition to phosphorus and sulphur as in phospholipids.

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 Phospholipids :
They are present in cell membranes of animals and plants. They are similar to fat
__
molecules in the structure except for the phosphate group PO4 which replaces the
third fatty acid (figure 11).
✲ Derivative lipids:
They are lipids derived from both the simple and complex lipids by hydrolysis
such as cholesterol and some hormones.

3
H C O Fatty acid 1
Phosphate group

H C O Fatty acid 2
CH3 H H O
+
H3 C N C C O P O C H
-
CH3 H H O H

Figure 11: Phospholipids

Be interconnected with the activities and exercises book: Practical activity: Detecting lipids - Applied
activity: Building models - Assessment activity.

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 Unit One Chemical Structure of Living Organism`s
Chapter 2
Bodies (Proteins and Nucleic acids)

By the end of this chapter, you

should be able to: Proteins
• Describe the molecular structure for Proteins represent the structural composition
both proteins and nucleic acids. of all living organisms. All living organisms from the
• Determine the functions of both proteins hugest animal to the extremely microscopic one are
and nucleic acids mainly made up of proteins. Proteins contribute to the
• Explain the relationship between biochemical processes preserving the life.
the sequence of amino acids in the
polypeptide chains and the composition Importance of proteins
of proteins and their variation. Proteins are involved in the structure and functions
• Identify the primary, secondary, tertiary of the living cells. They are one of the basic components
and quaternary structure of proteins. of cellular membranes. In addition, proteins form the
• Identify proteins practically. muscles, ligaments, tendons, organs, glands, nails,
• Propose scientific hypotheses and do hair and a lot of the vital fluids of the body such as
experiments to verify their validity. blood and the lymph. They are necessary for bone
growth. Furthermore, enzymes and hormones which
stimulate and regulate all the vital processes in the
body are proteins. Proteins are a basic component of
Terms chromosomes.
• Protein
• Amino acids
• Polypeptide
• Primary structure
• Secondary structure
• Tertiary structure
• Quaternary structure
• Nucleic acids
• Nucleotides

Figure 12: Spider’s net, hoves, and horns of animals are basically made
up of proteins.

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 Molecular structure of proteins
Proteins are complex macromolecules (polymers). They have high molecular
weight and made up of structural units (monomers) which are amino acids.

A model of protein models of amino acids

Figure 13: A model illustrating the composition of proteins and amino acids
Amino acids
Amino acids are the proteins building units. They are organic compounds made
up of hydrogen, oxygen,carbon and nitrogen atoms. Observe figure 14 to see
that amino acids are made up of a basic group- the amino group NH2 , an acidic
group- carboxyl group COOH (Those two groups are the functional groups in
the amino acid), a hydrogen atom and a terminal group R which differs from an
amino acid to another.
H

NH2 C COOH
basic acidic

group R group

Figure 14: General formula of an amino acid

Amino acids and building of protein

Proteins are made up of repeated units of amino acids which link with each
other by peptide bonds. Observe figure 15. You can observe that these bonds are
present between the carboxyl group of an amino acid with an amino group of
another amino acid, with the removal of water due to this combination.

H H

H O H O
H H
N C C N C C
H H
R O R O
Amino acid 1
Amino acid 2
H

Peptide bond
H O
H

H
N C C H
H
R O O
N C C H
H
R O
Water molecule

Figure 15:Amino acids are linked together by peptide bonds

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 The combination of two amino acids is called dipeptide compound and the
protein chain formed of several amino acids is called polypeptide. When protein
is being formed, it is not conditional for the combination to occur among similar
amino acids. This gives extensively wide and various possibilities to form proteins
depending on types, order and number of amino acids in the chain. About 20
amino acids participate in building the proteins such as
Research and expand
glycine, alanine and valine.
Log in the internet to
To clarify the idea of forming the proteins chains, identify the rest of amino
we take the amino acids : glycine, alanine, and valine acids involved in building
as examples and observe some possibilities of their the proteins. Observe and
determine the type of R
combination: group in each amino acid.

Possibility 1 Gly-Ala-Val-Gly-Ala-Val-Gly-Ala-Val-Gly Check your understanding

Do you expect that the type

Possibility 2 Gly-Val-Ala-Gly-Val-Ala-Gly-Val-Ala-Gly and properties of the protein
are the same in each of the
previous cases? Why?.
Possibility 3 Gly-Gly-Val-Ala-Gly-Gly-Val-Ala-Gly-Gly
Form other possibilities to
build a protein chain.
Possibility 4 Val-Val-Ala-Ala-Gly-Gly-Val-Val-Ala-Ala

Classification of proteins Enrichment

Proteins are classified according to the substances
The lack of albumin in the
involved in their structure into: body leads at an imbalance
in osmotic pressure of the
Simple proteins cell. Also, the body retains a
Simple proteins are made up of the basic units large amount of fluids which
of building protein, i.e of amino acids only such as causes swelling especially
in the feet and face because
albumin present in the leaves and roots of plants and albumin prevents the leaking
in blood plasma of humans. of fluids from blood vessels
into the tissues. So, albumin
maintains the osmotic
pressure inside the cell.

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 Conjngated proteins
Conjugated proteins are made up of amino acids associated with other elements
such as phosphorus, iodine and iron. Besides, the nucleic proteins associated with
the nucleic acids and phosphoproteins such as casein-the milk protein- which
contains phosphorus. The thyroid protein (thyroxine) which contains iodine, while
the haemoglobin necessary for transferring the oxygen during the respiration process
contains iron.

Levels of protein structure:

(a) Primary structure (b) Secondary structure (c)Tertiary structure (d) Quaternary structure

Figure (16) Levels of protein structure

* Primary structure
The primary structure of protein describes the sequence of the amino acids
in the polypeptide chain for a certain protein, (figure 16 a). This structural level
determines the type and number of amino acids and also the sequence of these
acids in the structure of this protein.

* Secondary structure
This level describes the way of twisting of the polypeptide chain due to the
presence of hydrogen bonds between the carboxyl group COOH and the amino
group NH2 in the amino acids near each others, (figure 16 b).

* Tertiary structure
This level describes the three dimensions shape of the protein resulted from
the bonds between the lateral groups R of amino acids which result in bending
the different polypeptide chains in several spatial levels giving each protein its
distinctive shape, (figure 16 c).

* Quaternary structure
This level describes the proteins formed of two polypeptide chains or more. It
results from the linking of polypeptide chains with each others, (figure 16 d).

Be interconnected with the activities and exercises book: Practical activity: Detecting proteins.

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Nucleic acids
Nucleic acids are biological macromolecules containing oxygen, hydrogen,
carbon, nitrogen and phosphorus . There are two types of nucleic acids: Ribonucleic
acid (RNA) and Deoxyribonucleic acid (DNA). Nucleic acids are made up of
basic units called nucleotides which bind together by covalent bonds to form a
polynucleotide or the nucleic acid.

Nucleotides
Nucleotides are the basic units forming the nucleic acid. Each of them is
composed of three units illustrated in figure 17.
✲ A pentose sugar molecule: There are two PO4 Phosphate group
basic types of sugar in nucleic a cids:
5
C
O
A First type: Deoxyribose sugar involved Nitrogenous
C
in the composition of DNA. 4
Pentose sugar
C
1 base

B Second type: Ribose sugar involved in C C2

3
the composition of RNA.
Figure 17: Composition of a nucleotide
✲ A phosphate group
It is connected to the carbon atom number 5 of the sugar molecule.
✲ A nitrogenous base
Nitrogenous bases are: adenine, guanine, cytosine, uracil, and thymine. Each
base is connected to the carbon atom number 1 of the sugar molecule. Nucleic
acids differs with respect to the difference of the nitrogenous bases forming them.

Check your skills:

Observe figure 18 and compare the nitrogenous bases of both DNA and RNA.

Cytosine
C C Cytosine

Guanine G G Guanine

Adenine A A Adenine

Uracil U T Thymine

RNA DNA
Figure 18: The molecular structure of DNA and RNA.

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 Importance of nucleic acids Enrichment
Nucleic acids are carried on the chromosomes Bio computer
inside the cell nucleus. They are responsible for In field of nanotechnology,
passing on the genetic traits from a generation to scientists arrived to that
another when cells divide. DNA carries the genetic DNA can be used to make
information responsible for appearing the distinctive biochips and using them to
make computers much faster
characteristics of the living organism and organize than current devices that
all the vital activities of the cell. rely on silicon chips. Also,
their storage capacity will be
On the other hand, RNA is transcribed from
millions of times greater than
the nucleic acid DNA, then it transfers into the current devices.
cytoplasm to be used by the cell to synthesize the
proteins responsible for appearing the genetic traits,
and those responsible for organizing the vital activities.

Be interconnected with the activities and exercises book: Practical activity: Assessment activity.

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 Unit One
Chapter 3
Water

By the end of this chapter, you

should be able to: Water widely spread out all over the Earth in
• Determine the properties of water on different forms: liquid, solid and gas. Water covers
which living organisms depend.
• Conclude the importance of water. about 70% of Earth’s surface. The percentage of water
• Identify the molecular structure of water. in living cells ranges from 65% to 90% of the cells’
• Propose scientific hypotheses and do
experiments to verify their validity.
weight. Furthermore, water forms two-thirds of the
human body. Eventually, water is the basis of life on the
Earth.

Terms
• Polar molecule

Figure 19: Water covers 70% of Earth’s surface

Research and expand

Importance of water Log in the internet
• Water plays a vital Identify more information
role in all vital processes about the importance of water
occurring inside the living for living organisms. Share
organism. your classmates and teacher
in what you have obtained.

15
 The molecular structure of water
Water molecule H2O is made up of the combination of an oxygen atom (O)
with two hydrogen atoms (H), via two single covalent bonds, figure 20. These bonds
are so strong and it is so difficult to break them down.
Observe figure 20 to see that hydrogen atoms
in the water molecule are found on one side of the History of science
molecule (pole), while the oxygen atom present at
the second pole. Oxygen has an electrical negative
charge, whereas hydrogen has an electrical positive
charge. As a result, water molecule has two
different poles; a negative pole and a positive pole.
So, the water molecule is called polar molecule. In 1860, the Italian scientist
Stanisalo Cannizzarro was the first
Each water molecule attracts with the adjacent mol- to discover the chemical structure
ecules to it throughout an electrical attraction result- of water.
ed from the difference of the electrical charges. Each
hydrogen atom (positive) in the water molecule attracts with the adjacent oxygen atom
(negative) in the adjacent molecule by a type of an electrical attraction. As a result,
hydrogen bonds are formed, figure 21. Both water polarity and hydrogen bond give the
water its unique properties.
Single
covalent
- O - Hydrogen bond
bond O H+
H
+
+ +
H
+
H H O
H+
Figure 20: Water is a chemical compound
made up of two hydrogen atoms and an
Figure 21: hydrogen bonds between water molecules
oxygen atom and called hydrogen oxide.

Water properties

1 Water is a universal solvent :

Of all the solvents, water is considered the best. It is called the universal solvent due
to the polarity of water molecules:
For example: Sodium chloride NaCl is made up of the combination of Na+ and
Cl-. As sodium chloride is added to water, hydrogen of water(positively charged)
attracts chlorine (negatively charged) towards it, while oxygen of water (negatively
charged) attracts sodium (positively charged) towards it. Since the attraction force
of the tow poles of water are stronger than the attraction forces between the two
atoms of sodium and chlorine. This means that it is possible to dissolve a lot of salts

16
and substances in water. In order to any substance be dissolved in water, it must
contain free ions. In other words, this substance is polar. This property is much
important for living organisms, because all the necessary substances which the
living cell needs to perform its function such as glucose, amino acids, vitamins, and
respiratory gases are transferred inside the body in the form of solutions, i.e. They
are soluble in water. Similarly, the reaction occurring inside the living cells such as
metabolism and the digestion reactions done by the enzymes are performed in the
form of solutions. In other words, the reacting molecules are dissolved in water

2 Water has an ability to ionize different molecules necessary to the life:

Water has the ability to dissociate the molecules into positive ions and negative
ions. This is related to the nature of the polarity of water molecules. It is a necessary
condition for chemical reactions to occur between the different substances. For
example, sodium bicarbonate secreted by pancreas gets
ionized in the presence of water into sodium ions Na+ Integration with physics
and bicarbonate ions HCO-3. This makes the medium
Sea breeze phenomenon: It is a
alkaline and suitable for the enzyme to work.
natural phenomenon takes place
in areas near to beach due to
3 Specific heat of water is high: the unequal heating which often
Hydrogen bonds between water molecules are occurs on land that is next to a
responsible for the unique thermal properties of water. large body of water. As the sun
heats Earth’s surface during the
Water does not only have high specific heat, but
day, the land warms up faster
also has the highest specific heat of all elements and than the water because the
compounds on the Earth. Specific heat is the amount of specific heat of water is much
energy needed to raise the temperature of the mass unit higher than that of land. So,
of water by 1 C°. As a result, we need great amount of the air over the land becomes
energy to raise the temperature of water and vice versa- warmer than the air over the
water loses great amount of energy when its temperature water. The warm air expands and
rises up, creating a low -pressure
is decreased.
area. Cool air blows inland from
This property is much necessary for all living the water and moves underneath
organisms. Living organisms are in need to remain the warm air. A wind that blows
their bodies temperature constant at a certain degree from the sea is known as a sea
breeze.
to perform their different vital processes. The large
water content of cells and tissues help to maintain
their temperatures constant. Furthermore, when living organisms lose the water
in the form of sweat or transpiration, their bodies temperature decreases when it
evaporates.
On the other hand, the high specific heat of water has provided the living
organisms with the suitable temperatures to survive on the Earth. If water would not

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 have existed in such great amounts on the Earth, Earth’s temperature had decreased
into extremely low temperatures due to the low specific heat of the substances
forming the crust. Water of oceans which covers 70% of Earth’s surface absorbs
great amounts of solar energy during daylight, then it emits this heat to the Earth’s
weather at night to preserve the Earth’s temperature suitable for the life of living
organisms. .

4 Surface tension and viscosity :

Surface tension is the cohesion of the free
surface of a liquid to take up the least possible area.
The viscosity is the resisting of a fluid to flow. Due
to the hydrogen bonds between water molecules
and its polarity, the surface tension of water is high
while its viscosity is low and they are suitable for
the continuation of life.
According to those two properties, water can Figure 22: Explain: Insects can stand
and walk on water surface without
help the cohesion of cell substances with the ability
sinking in it
to transfer water and nutrients into all the body
parts. Both the viscosity and surface tension slow down the water loss from plant
leaves throughout the stomata.
Be interconnected with the activities and exercises book: Practical activity: Water surface tension -
Assessment activity.

5 Increase the density of water at a temperature of 4°C:

When the temperature of the material (liquid -
solid - gas) is decreased its volume is decreased but
its density increases, water follows this rule within
certain limits, when the temperature of the water is
reduced its density begins to increase until reaches
the maximum value at a temperature of 4°C, then its
density decreases abnormally as its changes to ice at Figure 23: At 4 C°, water freezes
zero °C and the volume of the ice becomes greater and floats on the surface
than the volume of water and its density is less than
the water, so the ice floats over the water, and thus the freezing water is only on the
surface, while the water becomes below the ice at a temperature of 4°C.

18
 This property is much necessary for all living organisms. If water would have
been the same as other liquids, all the oceans and seas on the Earth had changed
into snow. But due to this property of water at 4C°, surface water freezes. This forms
an isolating layer to prevent the sea water from getting frozen. As a result, this
process provide a safe life to marine living organisms in oceans and seas water in
polar regions. This peerless phenomenon is attributed to the presence of hydrogen
bonds between water molecules .

6 In case of the presence of soluble substances, water freezing point is below

0C°:
This property is much necessary for living organisms
specially those living in cold regions where they are exposed
to temperatures below 0C° most of the time. Water in these
organisms’ bodies does not get frozen due to the soluble
substances in it. If the conditions would have been different,
living organisms had died as soon as they are exposed to
temperatures below 0C°.

7 The possibility of changing water into vapour at tem-

peratures much less than the boiling point:
Water changes into vapour in great amounts at
temperatures less than its boiling point. All living organisms
depend on this property. The water vapour formed on the
ocean surfaces is carried by the convection currents into the
cold layers of the atmosphere. These cold layers change the
vapour into clouds. Winds carry these clouds, then rain falls
down to provide the water necessary for the life of living
organisms.

8 Capillarity of water:
Water has the ability to raise in the capillary tubes without
Figure 24: Beside capillarity,
a need to a force to pump it up, in spite of the presence of
there are several forces and
gravity. With respect to this property, water can ascend from properties help water rising
tree roots to most of its parts. in the xylem tissue of trees
to extreme heights. Search
about them

Be interconnected with the activities and exercises book: Practical activity: Raising of water in
capillary tubes

Search and expand

Identify other properties of water on which living organisms depend. Share with your classmates
and teacher what you have learned.

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 Unit One
Chapter 4
Chemical Reactions in Organisms’ Bodies

By the end of this chapter, you

should be able to: Biochemical reactions necessary for growth,
• Identify what is meant by metabolism repairing damaged tissues, and obtaining energy take
in living organisms (catabolism and
anabolism) .
place in all living organisms’ bodies. These reactions
• Identify what are meant by enzymes , are called metabolism and they continue in all living
the principle, and mechanism of their
action.
organisms. If they stop working, this leads to death of
• Explore the effect of hydrogen ion the organism.
concentration (pH) on the enzymes’
activity.
• Determine (pH) of some solutions.
• Show the effect of temperature on the
Metabolism
enzyme activity practically.
• Clarify the grandeur of Allah in the Metabolism is a group of biochemical processes
accurate structure of living organisms’
bodies.
take place inside the cell. In these processes, complex
and macromolecules are being built from simple
molecules and called anabolism. On the other hand,
some molecules get broken down to extract chemical
energy stored in it and called catabolism.

Terms
• Metabolism Macromolecules Energy D
• Catabolism Catabolism Anabolism
• Anabolism
A Micro molecules F
• Enzymes
• pH Macromolecules
• Optimal pH
B
E
C
Figure 25: A diagram illustrating catabolism and anabolism

First: Catabolism:
Catabolism is the process of releasing energy stored
in the chemical bonds present in the molecules such as
glucose.

20
Second: Anabolism
In the process of anabolism,simple molecules are used to build up more complex
substances throughout a chain of reactions. These reactions consume energy such
as synthesis of proteins from the amino acids.

Enzymes
All the reactions occurring in living organisms require high Activation energy
activation energy to take place. To reduce the cell consumption The minimum energy
to more energy, there should be a catalyst to be sure that the needed in order for a
chemical reaction occurs rapidly throughout reducing the chemical reaction to
activation energy. This catalyst is the enzymes. occur.

Figure 26 illustrates the

consumption of a biochemical Activation en-
reaction to the energy in the ergy in absence
presence and absence of the of the enzyme
enzyme.
Activation ener-
* Compare the activation gy in presence
energy of the reaction in the of the enzyme
presence and absence of the
enzyme.
Enzymes are biological catalysts
made up of large protein Figure 26: Effect of enzymes on the energy
consumed in the reaction
molecules. They speed up the
chemical reactions inside the cell. The enzyme is made up of a combination of a
great number of amino acids forming a chain or more of polypeptide between each
others.

Properties of the enzyme:

1 Enzymes are similar to the other chemical
catalysts. They participate in the reaction
without getting affected. In other words, they
speed up the chemical reactions inside the
cells without getting consumed.
2 Enzymes are affected by the hydrogen ion
concentration (pH) and the temperature.
3 Enzymes are highly specific than other
catalysts. Each enzyme is specialized for one Figure 27: The three dimesions
reactant substance. This reactant substance is shape of an enzyme
called substrate, and it is specialized for one
type of reactions or few reactions.
4 Enzymes lower the activation energy required to get the reaction started.

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 Chemical composition of enzymes
The advancement of studying enzymes has enabled the scientists to divide the
enzymes according to their composition into two types:

Simple enzymes:
Simple enzymes are made up of simple proteins. They Word origin
The enzyme is
include a number of hydrolytic enzymes such as amylase, originally a Latin
figure 33. word means in the
yeast. Enzymes had
Complex enzymes: been discovered at
Complex enzymes are made up of two parts; protein the beginning in the
process of glucose
and nonprotein. The nonprotein part is made up of either fermentation into
a metallic atom (iron, magnesium, and copper), or an alcohol by the yeast.
organic molecule called coenzyme. The nonprotein part
in the enzyme is considered the active site for the enzyme
molecule.

Active site of the enzyme

There is one active site or more in each enzyme. It is responsible for making the
enzyme do its function.
Observe figure 28 and 29 to see that some enzymes such as trypsin has one
active site, while some others have more than one active site such as urease.

Active site 2

Substrate
Enzyme

Active site 1

Active site

Figure 28: A diagram illustrating an Figure 29: A diagram illustrating an

enzyme with one active site enzyme with more than one active site

Mechanism of enzyme action

Observe figure 30 to see that in any enzymatic reaction, the enzyme (E) binds
with the substrate (S) to form what is called enzyme - substrate - complex(ES).
This binding takes place on the active site, then the substrate is converted into the
products whilst attached to the enzyme, and finally the products are released, thus
allowing the enzyme to start all over again.

22
 Enzyme - Subtrate - Complex (ES)
Substrate (s) Reactants

Enzyme (E) Enzyme (E)

Figure 30: Adiagram illustrating the mechanism of enzyme action

Factors affecting the enzymes action

There are several factors that affect the speed of enzymes action such as:
concentration of the enzyme, concentration of substrate, temperature, hydrogen
ion concentrayion (pH), and the presence of inhibitors.
The following is an illustration to the effect of some of these factors on the
speed of enzyme action:

*The relationship between temperature and 0٫8 Enzyme activity

enzymes activity
Figure 31 illustrates the relationship between 0٫6
the activity of two enzymes and temperature.
Observe the figure and identify the following: 0٫4
✍ The temperature at which each enzyme
starts its activity. 0٫2

✍ The temperature at which the

Temperature
maximum activity of each enzyme 0 10 20 30 40 50 (C°)
appears. Figure (31): The relationship between tempera-
tures and enzyme activity.
✍ The temperature at which the activity
of each enzyme gets stopped.
Life application
✍ The thermal range of each enzyme’s activity.
Temperature degrees are
The protein nature of the enzymes makes them sometimes recorded on
some detergents to use
extremely sensitive to the thermal changes. Enzymes
them properly
activity is determined in a narrow range of temperatures
How can you explain this
comparatively to the ordinary chemical reactions. As you in the light of your study
have observed, each enzyme has a certain temperature at about the properties of
which the enzyme is more active. This point is called the enzymes?
optimal temperature which ranges between 37 to 40C°.
Be interconnected with the activities and exercises book: Practical activity: Effect of temperature
on the enzyme activity.

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 The enzyme activity gradually lowers, as the Improving the skills
temperature raises more than the optimal temperature
Design and do
until it reaches a certain temperature at which the an experiment to show
enzyme activity stops completely due to the change of the effect of lowering
its natural composition. the temperature of the
enzyme (below 0 C°) on
On the other hand, if the temperature lowers below its activity.
the optimal temperature, the enzyme activity lowers
until the enzyme reaches a minimum temperature at
which the enzyme activity is the least. The enzyme activity stops completely at 0
C°, but in case of raising the temperature, the enzyme gets reactivated once more

Potential of hydrogen (pH)

Potential of hydrogen pH is the best measurement determining the concentration
of hydrogen ion H+ in the solution. It also determines whether the liquid is acidic,
basic or neutral. Generally, all the liquids of pH below 7 are called acids whereas
the liquids of pH above 7 are called bases or alkalines. While the liquids of pH 7
is neutral and it equals the acidity of pure water at 25 C°. You can determine pH of
any solution using the pH indicators, figure 32.).

14 13 12 11 10 9 8 7 6 5 4 3 2 1

Power of acidic solution increases Power of basic solutions increases

Figure 32: Relationship of pH with the nature of the solution

Measuring pH
The most common mean to measure pH are the indicators and pH metre.
Examples of indicators are litmus papers, methyl orange and phenolphthalein.
Observe figure 33. Identify the colour produced with each indicator according
to the different pH values.

pH 14

0
Litmus papers Methyl orange Phenolphthalein

Figure 33: Indicators of measuring pH

24
 Indicators are always accompanied by standard colours used to determine pH
values,figure 34. These indicators give approximate values to pH, whereas the pH
metre gives more accurate values to pH, figure 35.

Figure 34: Standard coloured Figure35: Electronic pH

scale to measure pH meter

pH and the enzymes activity

You know that the enzymes are protein substances. They contain acidic
carboxylic groups COOH-, and basic amino groups NH2. So, the enzymes are
affected by the changing of pH value.

Each enzyme has a pH value working at it with a maximum efficiency called the opti-
mal pH. If the pH is lower or higher than its optimal pH, the enzyme activity decreased
until it stops working. For example, pepsin works at low pH. i.e, it is highly acidic
while trypsin works at high pH. i.e, it is basic. Most enzymes work at neutral pH 7.4.

‫ﹺ‬Enzyme
activity
Check your understanding

Why do most
enzymes work at pH
Trypsin 7.4?

Pepsin

pH
1 3 5 7 9

Figure 36: The optimal pH values for pepsin and trypsin enzymes

Be interconnected with the activities and exercises book: Practical activity: Effect of pH on enzyme activity-
Determining pH of several different solutions - Applied activity: Using raw materials from the environment to
make an indicator for measuring pH - Project: Measuring pH of various samples of water - Assessment activity.

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 Science, technology and society

Nanobiopharmaceuticals
Proteins have several vital roles in the human body. The ability of proteins
to treat a lot of diseases and disorders has been discovered. These biological
macromolecules have been known as biopharmaceuticals. Like several medicines,
it is extremely difficult to carry on the medicine directly to the target parts or
cells in the body. Recently and after the enormous development resulted from the
nanotechnology, many trials are conducted to carry on the medicine to the infected
cells in the body by using nanoparasites. These trials of carrying on the medicine to
the infected cells in the body by using nanoparasites have led to the originating of a
new field called nanobiopharmaceutics. As a result, the products used in this field
are called nanobiopharmaceuticals.

Key terms

• Carbohydrates: Carbohydrates are biological macromolecules made up of

several simple molecules (monosaccharides). They include sugars, starches and
fibres. They also are made up of carbon (C), hydrogen (H) and oxygen (O) atoms
with the ratio 1:2:1.
• Lipids: Lipids are biological macromolecules made up of carbon (C), hydrogen
(H) and oxygen (O) atoms. They made up of a large group of heterogeneous
compounds. All lipids are insoluble in water and dissolve in nonpolar solvents
asbenzene, and carbon tetrachloride
• Proteins: Proteins are biological macromolecules made basically up of carbon
(C), hydrogen (H) , oxygen (O) and nitrogen (N) atoms. They have high molecular
weight and their building units are amino acids.
• Nucleic acids: Nucleic acids are biological macromolecules. They contain
hydrogen, oxygen, nitrogen, carbon and phosphorus. They have two types: RNA
and DNA. They are made up of basic units called nucleotides.
• Metabolism: Metabolism is a group of biochemical processes occurring inside
the cell. During these processes, complex and macromolecules are built up from
simple molecules, and some other macromolecules are broken down to release
the chemical energy stored in them.
• Catabolism: Catabolism is a process in which some macromolecules
(carbohydrates, proteins and fats) are broken down into simple molecules to
release the chemical energy stored in them.

26
 Concept chart of chapter one

Cells of living organism

are made up of
occur inside the cells

Chemical reactions Inorganic molecules Organic molecules

By
Metabolism Enzymes Monosaccharide Carbohydrates

Amino acids Proteins

Anabolism Catabolism
Fatty acids lipids

Nucleotides Nucleic acids

Salts Water

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 Unit Two
Cell: structure and function

The cell is the basic unit of all life forms. Some living organisms are made up
of a single cell, while some others are made up of enormous number of cells. For
example, the human body is made up of 10.000.000.000.000 cells. Most cells are
extremely tiny to the degree that you can only see them by the microscope. Your
red blood cells, for example, are too extremely tiny to the degree that 40.000 cells
equal a size of pen head.
The cells are specialised to perform certain functions in the plants and animals.
For example, at the time you read these words, the nerve cells in your eyes carry
messages of what you read to the brain cells and the muscular cells connected to
your eyeballs move your eyes across the page.
Cells are collected together to form tissues such as the nerve tissue or muscular
tissue. In turn, the different types of tissues form organs such as the eyes, heart and
lungs.
All the cells whether they are specialised or unicellular organisms share in
general characteristics. The cell respires, feeds, rids of wastes, grows, reproduces
(produces similar cells) and finally dies after a certain period of time.
The cells can perform all these functions because they have special structures
called cell organelles, where each organelle is specialised for performing a certain
function.

net.
For mo n the
r e inform
ation about n cti o n , log i
the topic of Cell:structure and fu
 Time management
To achieve the maximum benefit of this unit, you need to:
• Manage your time among practical and theoretical study, research and the expan-
sion of information resources.
• Carefully, record the results of your practical study because they are the ideal way
to support your learning.

Learning outcomes
By the end of this unit , the student should be able to:
• Explain how the developing of the microscope contribute • Explain the structure of the cell wall and its function.
to state the cell theory. • Explain the role of plasma membrane in the process of
• Appreciate the efforts of scientists in discovering the cells cellular transport.
and their components. • Compare between the prokaryotic and eukaryotic cells.
• Explain the principles of the cell theory. • Clarify the differentiation of cells into specialized tissues,
• Compare the animal and plant cell. organs and systems in multicellular animal and plant liv-
• Draw the accurate structure of the animal and plant cell. ing organisms.
• Examine animal and plant cells microscopically. • Clarify some cellular processes (photosynthesis and res-
• Identify the organelles of the plant and animal cells and piration) briefly.
the functions of each of them. • Explain some vital processes and activities of the cell.
• Explain the accurate structure of the cell nucleus and its • Appreciate the grandeur of Allah in the ultrastructure of
functions. the cell as a building unit of all living organisms.
• Describe the structure of chromosomes. • Discard the extremism, fundamentalism, and give up
• Identify the number of chromosomes in some types of liv- clinging the opinion.
ing organisms. • Follow up the scientific method to solve the problems.
• Explain the ultrastructure of plasma membrane.

ory
1:Ce

ells and diversity of p

p s ues
u
3: Cell
C
Unit Two
Chapter 1

Cell theory

By the end of this chapter, you student

should be able to: You know that all living organisms are characterized
• Explain the principles of the cell with common characteristics such as feeding,
theory.
• Explain the development of the mi- transferring, respiration, excretion, motion, sensation
croscopes and reproduction. Some living organisms are unicellular
• Realize the role of the light and elec-
such as bacteria, Amoeba and Paramecium, while most
tron microscopes in studying the cell
• Appreciate the efforts of scientists in of them are multicellular such as humans, whales, and
discovering the cells and their com- trees.
ponents
Diversity of cells
.

Bacterial cell

Red blood cell Plant cell

key terms
Nerve cell
• Cell theory
• Light microscope
• Electron microscope
Muscular cell Egg cell
Figure 1: A group of various cells magnified 700 times of their real size.
Cell: The cell is the tiniest building unit in the
organism’s body capable of carrying out all the functions
of life.
Observe the group of cells illustrated in figure 1,
then identify:
• What are the differences between these cells in
regard to the shape and size?
• Determine which of these cells is the tiniest and
which is the biggest.

30
• According to your point of view, why cells differ from each other in the shape.
Cells vary in the shape, structure, and size as illustrated Enrichment
in figure (1). There is a relationship between the cell shape
Of all the cells, the
and the functions it performs. The nerve cell (neuron) is
nerve cell (neuron) is the
long to be able to transfer the messages from the spinal longest. The length of a
cord present inside the vertebral column into your toes. nerve cell may reach one
The muscular cells are characterized by being cylindrical meter or a little more,
and long, and accumulate with each other to form muscle while the biggest cell is
fibres. The muscular cells can contract and relax to help the ostrich unfertilised
the animal move freely. egg.

Cell theory
From the scientists which have contributed in developing the cell theory are
scientists:
Robert Hook
He is an English scientist and has the favour in discovering the cells. In 1665,
he invented a simple microscope and used it to screen a piece of cork. He found
that the piece is composed of small boxes, figure 2. He named each box the word
cell. The term cell is derived from the Latin word cellula which means the cell or
the small room.
Antonie Van Leeuwenhoek
Antonie Van Leeuwenhoek was born in Netherlands in 1932. He spent his life
as a government employee. Van Leeuwenhoek was amateur to screen objects using
the lenses. By using these lenses, Van Leeuwenhoek succeeded in making a simple
microscope with ability to magnify the objects up to 200 times of their real size.
He used this microscope for screening different substances such as water of ponds,
and blood. Van Leeuwenhoek was the first human being to observe the world of
microscopic organisms and living cells.

Figure 2: The draw which Robert Hook demonstrated

for the cork tissue in the form of rows of sequenced Figure 3: Antonie Van Leeuwenhoek’s
spaces as he screened throughout the microscope. microscope

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 Matthias Schleiden
In 1838, the German scientist Matthais Schleiden deduced that all the plants are
composed of cells. He stated his conclusion depending on his own researches and
that of the other previous scientists.
Theodor Schwann
In 1839, the German scientist Theodor Schwann deduced that all living
organisms bodies are composed of cells. Develop your skills
Rudolf Virchow Summarizing skill:
Rudolf Virchow is a German doctor. In Brief the role of scientists; Robert Hook,
1855, he stated that the cell is the functional Antonie Van Leeuwenhoek, Matthais
and building unit of all living organisms. Schleiden, Theodor Schwann and
Additionally, he emphasized that the new Rudolf Virchow in discovering the cells.
cells are produced only by previous other
living cells.
The efforts of previous scientists have resulted in and gave rise to what is known
by the cell theory. The cell theory is considered the most important basic theory
in the modern biology. This cell theory is mainly based upon the following three
principles:
1 All living organisms are made up of cells.
2 Cells are the basic functional units for all the living organisms.
3 All cells come only from other pre-existing living cells.

Development of microscopes
The progression of biology is thoroughly based upon the development of the
technologies used in the science field related to the cell science (Cytology). This
development has leaded to increase the ability of scientists to observe and analyse.
Among of all the technologies, the microscope was the most important tool.
Light microscope
The light microscope was the only available tool for the scientists until 1950.
This microscope depends on the sunlight or artificial light to work. It is characterized
with its ability to magnify micro - organisms and nonliving things. It is also used for
screening the composition of large sized objects by slicing them into thin slices that
allow the light to permeate through. The light microscope could magnify the objects
1500 times of their actual size according to the magnifying power of the two lenses
used (objective and ocular lenses). These lenses are made of glass and they can not
magnify more than 1500 times because the image will be blurred (unclear).

32
 Objective lens Ocular lens

White blood cells

Figure 4: White blood cells as seen by compound light microscope. The image is
magnified 1000 times of its actual size.

The total magnifying power of the light microscope can be calculated through
the following relation:
Magnification = the magnifying power of ocular lens * the magnifying power of the objective lens.

Over years, scientists innovated better methods to observe the samples more
clearly throughout increasing the contrast (difference) between the different parts of
the sample. One method of these contrast methods between the sample parts was
using the dyes to stain or colour certain parts of the sample to be clearer. Similarly
when we screen the white blood cells as illustrated in (figure 4). On the contrary,
using the dyes involve disadvantages such as they kill the living samples. There is
another method to increase the contrast which is done by changing the level of
light.
✲ Observe: How does the contrast between the three images in figure 5 seem?
Compare them.

Bright field micrograph Dark field micrograph Phase contrast micrograph

Figure 5: Three photographs of an unicellular organism (Paramecium) were taken using 3 different light
microscopes. Which of them is the most contrast and detailed?

Be interconnected with the activities and exercises book: Practical activity: Using compound
microscope in a proper way.

Electron microscope:
In 1950, scientists started to use the electron microscope in which a beam of
electrons with high-speed is used instead of light. These electrons are controlled by
electromagnetic lenses. Objects can be magnified 1000.000 times of their actual sizes.

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 The electron microscope provided a field to
Life skills
clarify the cellular components that had not been
known before. It helps to know more accurate Communication skill
details for the structures that had been known
Use the references in
before because the electron microscopes provide
school library or the
high resolution magnified, and highly contrasted
internet to write down
images comparatively to those produced by light
a report about electron
microscopes. It is related to the shortness of the
microscopes. Review your
wavelength of the electronic ray comparatively
report with your teacher
to the light ray. Objects’ images are received
then display it in front of
on a fluorescent screen or on a highly sensitive
your classmates to discuss
photographing board.
it.
There are two types of electron microscopes:
the scanning electron microscope used for studying
the cell surface, and transmission electron microscope used for studying the internal
structures of the cells.
✲ Observe the image of the white blood cell under the two types of the electron
microscopes-scanning and transmission.

The transmission The scanning electron

electron microscope microscope

Figure 6: A white blood cell as it appears under the scanning electronic microscope (magnifying power
used × 3500) and as it appears under the transmission electron microscope (magnifying power used ×8900).
Compare the tow images in the two cases..
• Thus, you can see that the development of microscopes increases our
knowledge of the science of cell (Cytology) and its related sciences.

Be interconnected with the activities and exercises book: Assessment activity.

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 Unit Two
Chapter 2
Cell ultrastructure

By the end of this chapter, you should

be able to:
You have learned that the cell is the functional
• Identify the organelles of plant and and building unit in all living organisms. These cells
•
animal cell and the functions of each.
Explain the ultrastructure of the cell
are characterized by their ability to grow, reproduce,
nucleus and its functions. respond to external stimuli and perform the different
• Describe the structure of the chromo-
some. metabolic processes.
• Explain the ultrastructure of the plas-
ma membrane. Think
• Explain the structure of the cell wall
and its function. • How can a cell perform all these functions?
• Appreciate the grandeur of Allah in
the accurate structure of the cell as a
building unit of living organisms. • What are the structures present in the cell that
• Design a model for the eukaryotic cell. enable it to perform these functions?
• Compare between the eukaryotic and
prokaryotic cells
• Compare between the plant and ani-
mal cells The cell as a factory
• Examine the plant and animal cells mi-
croscopically.
• Draw the ultructure of the plant and Suppose you take a tour in a factory producing nutrients.
animal cells.
The following figure illustrates such factory.

key terms
• Cell membrane
• Cell wall
• Cytoplasm
• Nucleus
• Cell organelles
• Chromosome
• Endoplasmic reticulum
• Golgi body
• Lysosome
• Mitochondria
• Centrosome
• Chloroplasts Exit
• Ribosomes Entry
• Prokaryotic cell
• Eukaryotic cell

Figure 6: Parts of a factory producing nutrients

35
 ✍ What are the main parts in this factory?
✍ What is the role of each part in preparing the product until reaching
its final shape?
The cell closely looks like the factory. The cell has a group of cellular organelles
and each organelle has a certain role to enable the cell to perform its vital functions,
table 1.
Table 1: Analogy of cell parts and factory ones.

Factory Cell Type of activity

1 Factory fence Cell membrane Entry and exit of materials

2 Manager’s office Nucleus Controlling centre

3 Oven Mitochondria Generating the energy

Transferring the
4 Conveyor belts Endoplasmic reticulum
substances inside the cell

5 Preparing food devices Ribosomes Making food

6 Warehouse Vacuoles Storage

Transferring the materials

7 Transferring vehicles Lysosomes
out of the cell

Cell parts
The cell is basically made up of a protoplasmic mass surrounded by the
cell membrane. The protoplasm is differentiated into a nucleus and cytoplasm.
Cytoplasm contains a group of cellular structures called cell organelles.

Be interconnected with the activities and exercises book: Practical activity: Comparing animal cell
and plant cell.

36
 Cytoplasm

Envelope

Nuclear envelope

Chromatin
Microtubules
Nucleus

Mitochondrion
Nucleolus
Ribosomes

rough endoplasmic
reticulum

Smooth endoplasmic
reticulum

Chloroplastid

Cell wall

Golgi apparatus
Plasma membrane

Figure (8): Plant cell

Mitochondrion
Vacuole

Nuclear envelope

Chromatin Nucleus
2 centrioles
Nucleolus

Ribosomes
Rough
Microtubule endoplasmic
reticulum

Lysosome

Plasma
Cytoplasm
membrane

Golgi apparatus Smooth andoplasmic

reticulum
Figure (9): Animal cell

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 First: Cell wall
Cells of plants, algae, fungi and some bacteria are surrounded by a cell wall
besides the cell membrane. This wall provides the cells with support and protection.
Cell wall is characterized with being pitted. It is mainly composed of cellulose
fibers, therefore this wall allows the passage of water and dissolved substances
through it easily.
Enrichment
Cellulose fibers in the
Cell walls play an cell wall cell wall of plant cell
important role in protecting
the cells and making them
resistant to wind and other
weather factors. These
walls provide the cells
with strong support as in plant cell

the perennial trees such as

palm trees. While herbal
small plants contain cell
walls with little elasticity
that make them able to cellulose molecules
maintain their shapes as
they are exposed to strong Figure 10: Cellulose fibers in the cell wall of the plant cell
wind.

Second: Cell membrane(plasma membrane)

It is a thin membrane covering the cell and separates its components and
surrounding medium. This membrane performs a basic role in organising the
passage of substances to and from the cell. Besides, it prevents the spreading of
cytoplasm outside the cell.
Cell membrane is composed of two layers of phospholipids molecules which
their hydrophilic heads (dissolve easily in water) meet the water medium in and
out the cell. While their hydrophobic tails (do not dissolve) are present inside the
membrane, figures 11 and 12.

Embedded proteins Phospholipids Hydrophilic

cholesterol head

Hydrophobic
tail

Figure 12: The structure of the

phospholipids molecule and
how phospholipids molecules
Fibers of cytoskeleton are arranged in the cell
membrane

Figure 11: The structure of cell membrane

38
 Molecules of proteins are embedded between molecules of these two layers.
Some of these protein molecules work as cell identification sites to different
substances such as nutrients and hormones. While some others work as gates to
pass the substances to and from the cell.
Due to the phospholipids forming the cell membrane are a fluid substance, the
membrane in turn is considered a fluid structure (similar to the oil floating on water
surface). The linkage of phospholipids molecules with molecules of cholesterol
contributes maintaining the cell membrane cohesive and intact.
Be interconnected with the activities and exercises book: Practical activity: Designing a model of
cell membrane.

Third: Nucleus
The nucleus is the most obvious organelle in the cell that you can see under
the microscope. It often has a spherical or oval shape and located in the middle
of the cell. Furthermore, it is surrounded by a double membrane called the
nuclear envelope. The nuclear envelope separates the contents of the nucleus from
cytoplasm. There are several tiny pores in the nuclear envelope through which the
substances pass between the nucleus and the cytoplasm.
The nucleus contains a transparent gelatinous fluid called nucleoplasm. The
nucleoplasm contains minute tangled threads coiled around themselves and called
chromatin. The nucleus also contains another structure called nucleolus. The cell
nucleus may contain more than a nucleolus, especially in the cells responsible for
forming and producing the protein substances such as enzymes, hormones and so on.

Nucleolus Chromatin
Endoplasmic reticulum Nuclear envelope
Nucleoplasm
Nuclear pore

Figure 13: Structure of the nucleus

Structure of chromosomes
During cell division, chromatin gets changed
into rod-like structures called chromosomes, figure
14. Chromosome appears in the metaphase of the
cell division consists of two threads joined together
at a central part called centromere. Each thread of Figure 14: Behaviour of chromosomes
those two threads is called chromatid, figure 15. Each during cell division

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 chromatid is composed of nucleic acid DNA coiled around molecules of proteins
called histone as illustrated in figure 16. DNA carries the genetic information that
controls the shape and structure of the cell and organises the vital activities of the
living organism cells. All your body traits are inherited from your ancestors and you
inherited them throughout transferring copies of the stored genetic material which
is being copied to the new generations during reproduction.
Be interconnected with the activities and exercises book: Applied activity: A model of chromosome.

Word meaning
Chromosomes were given this name because they are stained by the basic dyes and take
a coloured stain that makes them more clearly seen during cell division.

Do you know?
Chromosome is not consisted
of 2 chromatids in all phases
of mitosis except at its
beginning till its metaphase.
It becomes consisted of
one chromatid in anaphase
and telophase, and called
chromatid centomere daughter chromosome. At
the beginning of each new
division, the genetic material
Figure (15): Chromosome as appeared under the electron microscope is duplicated, so each
during cell division chromosome consists of 2
chromatids..

chromatid

chromatin

centromere

histone proteins

DNA

Figure 16: Chromosome structure

From the previous, we can summarize the role of the nucleus in the following points:
• It is a control centre in all cell activities.
• It contains the chromosomes responsible for transferring the genetic traits.

40
• It controls in the division of the cell.
• It contains the nucleolus responsible for sunthesis the ribosomes which play
a very important role in synthesising the proteins..

Fourth: Cytoplasm
The cytoplasm is almost a fluid-like substance present between the cell
membrane and nucleus. It is mainly composed of water and some organic and
inorganic substances. It also contains a network of threads and microtubules that
acquire the cell a support to help it maintain its shape and form. In addition to its work
as passages to transfer the different substances from one place to another inside the
cell and is called the cytoskeleton. The cytoplasm also contains a group of various
structures known as cell organelles. Some of these organelles are not surrounded
by a membrane and called non-membranous organelles such as ribosomes and
centrosome. While some other organelles are surrounded by a membrane and
called membranous organelles such as endoplasmic reticulum, Golgi apparatus,
mitochondria, lysosomes, vacuoles, and plastids.

1 Ribosomes
Ribosomes are round-shaped organelles that synthesize protein in the cell.
Some of them are present in the cytoplasm (single or in clusters) where the protein is
produced and directly released in the cytoplasm. The cell uses it in its vital processes
such as growth, regeneration, and so on. While most ribosomes are attached to the
outer surface of the endoplasmic reticulum and produce the proteins transferred by
endoplasmic reticulum to the outside of the cell (such as enzymes) after entering
some changes to it.

2 Centrosome
Animal and some fungi cells (except for nerve cells-neurons) contain two tiny
particles called centrioles. They are located near the nucleus in a region of the
cytoplasm. This region is called centrosome.
The centrosome is not present in the plant and some
microtubules
fungi cells. These cells contain a region of cytoplasm to
conduct the same functions instead. Each centriole is
composed of nine groups of microtubules ordered in
triples in a spherical shape, figure 17.
The centrosome plays an important role during cell
division where the spindle filaments extend between
the centrioles present at each pole of the cell. The
centrosome also plays an important role in forming the
flagella and cilia.
Figure (17): Centrioles

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 3 Endoplasmic reticulum:
The endoplasmic reticulum is a network of membranous canaliculi that extends
in all cytoplasm. It is attached to the nuclear envelope and cell membrane. So it
forms an internal transferring system that benefits in transferring the substances
from a part to another inside the cell and so transferring the substances between
the nucleus and the cytoplasm.
Thinking corner
✲ There are two types of the endoplasmic reticulum
There is a rough endoplasmic reticulum and The presence of
smooth endoplasmic
smooth endoplasmic reticulum. The rough endoplasmic
reticulum increases
reticulum is characterized by the presence of a large in heptic cells. While,
number of ribosomes on its surfaces. It is specialized in the presence of rough
synthesising proteins in the cell, making changes on the endoplasmic reticulum
protein produced by the ribosomes, and making new increases in cells of
membranes in the cell. As for the smooth endoplasmic stomach linig and
reticulum, the ribosomes are absent from it. It is endocrine glands. Explain
this in the light of your
specialized in synthesising lipids, transforming glucose
study of endoplasmic
into glycogen, and modifying the nature of some toxic reticulum functions.
chemicals in the cell to reduce its harmful effects.

4 g apparatus
Golgi pp
nuclear envelope

Ribosmes

rough endoplasmic reticulum

smooth endoplasmic reticulum

Figure (18): Endoplasmic reticulum.

Golgi apparatus is a series of flat membrane- Word origin

bound sacs. The numbers of Golgi apparatus differ Golgi apparatus is named for
in the cell according to the cell’s secretion activity. its discoverer,Italian anatomist
Golgi apparatus is specialised for receiving the and pathologist Camillo Golgi
molecules of substances secreted by the endoplasmic who described it for the first
time in 1898. This organelle is
reticulum across a group of transporting vesicles.
also known as Golgi complex or
Then, it classifies and modifies these vesicles and Golgi apparatus. It is also known
distributes them into the places where they are used as dictyosomes in plants and
in the cell. Golgi apparatus may also pack them algae.

42
inside secreting vesicles called lysosomes, that move forward to the cell membrane
as the cell dismisses it to outside as secretory products.
Vesicle

Flate plates

transporting vesicls

Figure (19): Golgi apparatus

bacterial cell
5 Lysosomes: endocytosis
Lysosomes are small, round,
membranous vesicles formed by Golgi endoplasmic
bodies. They contain a group of digestive reticulum
digestive vesicle
enzymes. Lysosomes’ function is to rid of transport vesicle
worn and senile cells and organelles which
no longer have benefits. Furthermore, lysosome
fusion of
vesicle with
lysosomes digest the large molecules of
lysosome
nutrients engulfed by the cell and change
them into structurally simpler substances lysis of bacterial
cell
to enable the cell to benefit from them.
Golgi apparatus
For example, white blood cells use the
digestive enzymes present inside the
secretory vesicles
lysosomes to digest and destroy the
pathogens which invade the cell, figure
20. exocytosis

The cell is not affected by the lysosome

Figure (20): The role of lysosmes in digesting the
enzymes because these enzymes are pathogens inside white blood cell
surrounded by a membrane isolating
Thinking cornerner
them from the cell components.
Imagine that
6 Mitochondria: the inner membrane
Mitochondria are sac-like membranous organelles. of mitochondria does
Its wall consists of two membranes. A group of folds not contain cristae.
known as cristae extends from the inner membrane into Does the efficiency of
mitochondria increase
its matrix. These cristae work on increasing the surface
or decrease? Explain.
on which the chemical reactions producing the energy

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 take place. Mitochondria are considered the main storehouse for the respiratory
enzymes in the cell. They are also considered a storehouse for other substances
necessary to store energy resulting from respiration (due to the oxidation of the
nutrients, especially glucose). The energy resulting from respiration is stored in the
form of a chemical compound called adenosine triphosphate (ATP) from which the
cell can extract energy once more.

cristae

outer memrane

inner membrane

Figure (21): Mitochondrion

7 Vacuoles:
The vacuoles are sac-like membranous sacs (similar to bubbles filled with a
liquid ). They store water, nutrients, and the wastes of the cell until it gets rid of such
wastes. The vacuoles are small and large in number in animal cells while they are
collected in one big vacuole or more in the plant cells.

8 Plastids:
The plastids are various shaped membranous organelles present in plant cells
only. There are three types of plastids that differ from each other in regard to the
pigment present in each type:
• White plastids or Leucoplasts: They are plastids that don’t contain any type
of pigments. They work as centers for storing starches. Furthermore, they can be
present in the roots of sweet potatoes, stems of potatoes and the internal leaves
of cabbage.
• Chromoplasts: They are plastids that contain carotenoids which their colours
varies between red, yellow and orange. This type
extensively spread in the petals of flowers, fruits and in the Enrichment
roots of some plants such as rapeseed The colours of the plant
• Chloroplasts: They are present in the leaves and stems of cell are related to the
chromoplasts as in the
green plants. They contain the chlorophyll that transforms
petals of the flowers or the
the light energy of the sun into chemical energy in the presence of some coloured
form of glucose throughout photosynthesis. Chloroplasts pigments in cytoplasm as
are composed of a double envelope surrounds a matrix in beet and roselle
called the stroma.

44
 The stroma contains layers of disc-shaped, compact structures known as
thylakoids which each group of them forms what’s known by granum.
outer memrane

inner memvrane

matrix

granum

Figure (22): A chloroplast

Be interconnected with the activities and exercises book: Applied activity: Designing a model of the
plant cell and animal cell

Prokaryotic
‫ﺧﻀﺮﺍﺀ‬and
‫ﺑﻼﺳﺘﻴﺪﺓ‬Eukaryotic
:(37) ‫ﺷﻜﻞ‬ Cells
Depending on the cell structure, all the living cells are divided into two groups:
prokaryotic cells such as bacteria and eukaryotic cells such as animals, plants, fungi
and protista. Observe figures 23 and 24, then determine the following :
✍ The similarities between prokaryotic and eukaryotic cells.
✍ The differences between prokaryotic and eukaryotic cells.

cell meembrane
cilia
cytoplasm
cell organelles
ribosomes

capsule nucleus
cell wall

cell membrane

gentic material
nucleolus

fagella
(A)
(B)
0.5μm 10 - 100 micrometers

Figure (23): The ideal structure of a Figure (24): The ideal structure of an eukaryotic
prokaryotic cell as it appears by the cell
transmission electron microscope

✲ We observe that all the cells are similar in some characteristics:

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 • They are surrounded by cell membranes which separate between their internal
components and the surrounding medium.

• They have some cellular structures called cell organelles that enable the cell to
do its functions. These organelles differ from a cell to another.

• They contain a gelatinous fluid called cytoplasm in which cell organelles float.
It also contains some substances necessary for the cell surviving such as water,
salts, enzymes and so on.

• They have a genetic material carrying the information necessary for duplicating
the cell and controlling all the vital processes of the cell.

Prokaryotic cells:
Prokaryotic cells are enormously smaller-sized than eukaryotic cells. Their
internal structure is less complex than eukaryotic cells. The prokaryotic cell doesn’t
contain a definite shaped nucleus and the genetic material is directly present in
cytoplasm and not surrounded by an envelope. Furthermore , the prokaryotic cells
don’t contain several membranous organelles like those present in the eukaryotic cells
, figure 23. However they conduct all the vital cellular activities such as respiration,
nutrition, motion, reproduction, responding to surrounding environmental stimuli
, and so on.

Eukaryotic cells:
Eukaryotic cells are enormously bigger-sized than prokaryotic cells. They are
characterized by an internal complex structure and contain a genetic material
surrounded by a nuclear envelope. As a result, they have a definite-shaped nucleus.
Furthermore, they contain several membranous organelles, figure 24.

Be interconnected with the activities and exercises book: Assessment activity

46 -U nit 2
io logy
B
Unit Two
Chapter 3 Differentiation of cells and diversity
of plant and animal tissues

By the end of this chapter, you should

be able to: Most living organisms are composed of several
• Identify the organization levels in cells. But, are these cells irregular or disordered? Does
the multicellular living organisms.
• Identify the concept of tissue.
each of them work separately from the other?
• Differentiate between the simple

•
and complex tissues.
Identify different types of animal
Organization of living organisms
and plant tissues.
• Determine the functions of the tis- Cells are specialized in their functions, so they are
sues.
present in types but not one. Each group of specialized
cells organize to form what is known as a tissue. For
example, the heart muscular cells which organize with
each other to form the muscular tissue of the heart wall,
figure:25.

Figure (25): Muscular

tissue in heart wall
Key terms
• Simple tissue
• Compound tissue
• Parenchyma
• Collenchyma
• Sclerenchyma
• Xylem
• Phloem Figure (26): Heart Figure (27): Circulatory system
• Epithelial tissue
• Connective tissue If the cells forming the tissue were symmetrical with
• Muscular tissue
each others in the shape, structure, and function, then
• Nervous tissue
the tissue is called a simple tissue.
But, if the tissue is composed of more than a type
of cells, then it is called a compound tissue. Types of
tissues vary and contrast in regard to the difference and
diversity of living organisms and so are the activities and
the vital functions conducted by the tissues. We will

47
 identify the most common types of tissues in animals and plants in the following. In
most living organisms the tissues organize with each other in groups called organs.
Each organ is a group of tissues working harmonly to perform certain functions.
Such tissues and organs are present in plants and animals. For example, the heart,
figure 26, is an organ in the multicellular organisms such as humans. It is mainly
composed of a heart muscular tissue, nervse, and connective tissue. Heart muscles,
nerves and connective tissue collaborate together in their work to pump the blood
from the heart to all body parts.
The group of organs working together form what is known as the system. The
heart, blood and blood vessles form the circulatory system of humans, figure 27.
Systems organise and integrate together to form the whole body of the organism. The
human body is composed of the integration of several systems besides the circulatory
system such as skeletal system, muscular system, nervous system, digestive system,
respiratory system, excretory system , reproductive system and so on.

Plant tissues
Plant tissues vary into simple and compound tissues.
First: Simple tissues
There are three types of simple tissues:
Parenchyma tissue: The cells of parenchyma potato tuber
tissues are oval or round shaped. Their walls
are soft and elastic and contain spaces
among them for aeration. The parenchyma
tissue contains chloroplasts, chromoplasts,
or leucoplasts.
Parenchyma cell contains one big vacuole
or more filled with water and mineral salts.
Figure (28): Parenchyma tissue
The parenchyma tissue performs several
parsley stem
functions such as photosynthesis, storing
nutrients such as starch, and it is responsible
for aeration.
Collenchyma tissue: The collenchyma tissue is
a soft tissue. It is a living tissue and its cells
are somewhat rectangular-shaped cells. Its
walls are irregularly thickened with cellulose.
This tissue helps in supporting the plants by Figure (29): Collenchyma tissue
acquiring them the elasticity needed
pear fruit
Sclerenchyma tissue: The sclerenchyma tissue is
a solid tissue. It is a non-living tissue. The cells of
these tissues are thickened by a substance called
lignin. It also strengthen and support the plants
and acquiring them the elasticity and hardness
needed Figure (30): Sclerenchyma tissue

48
Second-Compound tissues
Examples of compound tissues in the plants are vascular tissues the conductive
tissue. They are divided into two types; xylem and phloem. Their function is the
transport (conduct) in the plants.
Xylem tissue
• Xylem is composed of vessels, tracheids and parenchyma cells. Xylem vessels
are tubes, each of them is made up of a vertical raw of cells from which the
protoplasm disappeared, then their transverse walls disappeared too and lignin
precipitates on inner surface of their walls at the inside to change the cells into
long, wide vessels through which water and salts are transported. The vessels
length ranges from a few centimeters to several meters as in high trees. While
each tracheid is composed of one a cell in which protoplasm is disappeared and
its walls get lignified.
• Xylem is specialized for transporting water and salts from the root to the leaves
in addition to supporting the plants.
Phloem tissue companion cell parenchyma cells
tracheids
• The sieve tubes result from
the compact cells (vertically)
above each other, the nuclei
vanished and the separating
walls became perforated. For
that reason they are called
sieve tubes through which the
cytoplasm passes in the form
of cytoplasmic strands. The
sieve tubes are adjacent with
vesseles
companion cells to provide sieve plate
sieve tubes
the sieve tubes with the Figure (31): Phloem tissue Figure (32): Xylem tissue
energy required to perform
their functions, figure 31.
• The phloem transports the nutrients resulted from photosynthesis from the
leaves to the other parts of the plant.

Animal tissues
Animal tissues can be differentiated into four basic types. Each of them matches
with the function it performs:
First: Epithelial tissues: They are the tissues that cover the outer surface of the
body or line-up the body’s internal cavities. The epithelial tissue is composed of a
great number of closely adjacent cells connected by little interstitial substance
The epithelial tissues are subdivided into two basic types with respect to the
shape and structure:

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 1 Simple epithelial tissue:
Its cells are organized in one layer, figure 33, the example of this tissue are:
Simple squamous tissue : It is composed of one layer of flattend cells as in the
endothelium of blood capillaries and the walls the alveoli in the lungs.
Simple cuboidal tissue: It is composed of one layer of cuboidal cells as in the lining
of kidneys’ tubules.
Simple columnar tissue: It is composed of one layer of columnar cells as in the
lining of the stomach and the intestines

basement membrane

sub-epithelial tissue nuclei of cells

simple squamous tissue

simple columnar tissue simple cuboidal tissue

Figure (33): Examples of simple epithelial tissues

2 Stratified or compound epithelial tissue:

Its cells are organized in several layers, figure 34, its examples are:
Stratified squamous tissue: It is made up of several layers of compact cells above each
others. The surface layer of this tissue is squamous as in the skin epidermis.
The epithelial tissue performs different functions with
respect to its site such as:
• Absorbs water and digested food as in the lining of the digestive
canal.
• Protects the cells which it covers from drought and pathogens
as in the skin epidermis.
Figure (34): startified
• Secretes the mucus that makes the cavities it covers smooth as
squamous tissue
in the digestive canal and the trachea.
Second: Connective tissues
The connective tissues are made up of somewhat distant cells that immersed
in an intercellular substance that may be fluid, semi-solid, or solid (figure 35).
Accordingly, they are divided into three groups:
1 Connective tissue proper : It is the most widely spread type. It gathers between
being fairly solid and quite elastic. The main function of this tissue is to bind the
different tissues and systems of the body with each other. This type is present under
the skin and in the mesentries
2 Skeletal connective tissue: It includes the bones and cartilages. It contains a
solid intercellular substance in which calcium precipitates in case of the bones. Its
basic function is the supporting of the body

50
 3 Vascular connective tissue : It includes the blood and lymph. It contains a
fliud intercellular substance. Its basic function is to transport digested food and
excretory substances

Vascular connective tissue (blood) Skeletal connective tissue (cartivage) Skeletal connective tissue (bone) Connective tissue proper

Figure (35): Examples of connective tissues

Third: Muscular tissues:

The cells of this tissue are known as muscular cells or muscle fibers. They
differentiate from the rest of body cells with their abilities of contraction and
relaxation. This helps the organism to move. There are three types of muscular
tissues:

1 Smooth muscles:
They are composed of unstriated involuntary muscle
fibers. They are present in the walls of viscera such as the
Figure (36): Smooth muscule fibres
wall of digestive canal, urinary bludder and blood vessels.
2 Skeletal muscles:
They are composed of striated voluntary muscle
fibers. They are usually connected with the skeleton, such
as muscles of arms, legs and trunk. Figure (37): Skeletal muscle fibres

3 Cardiac muscles:
They are composed of striated involuntary muscle fibers
and present in the heart wall only. They contain special
parts called intercalated discs that bind the muscle fibers
Figure (38): Cardiac muscle fibres
together and make the heart beats in a rhythmic way as a
functional unit

Fourth: Nervous tissues:

The cells of nervous tissues specialize
cell body
in receiving sensory stimuli whether they are
internal or external the body and connect dendrites

them to the brain and the spinal cord, then

terminal arborization
transmitting the motor impulses from one of
axon
them to effector organs (muscles or glands). nucleus
‫ﻧﻮﺍﺓ‬

As a result, these tissues are responsible for Figure (39): The neurone is the building and
organizing the different activities of the body functional unit of nervous system
organs.
Be interconnected with the activities and exercises book: Practical activity: Examining different
types of plant and animal tissues - Assessment activity

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Unit Two
Chapter 4

Cell Processes

By the end of this chapter, you

should be able to: Cells are living units that perform several vital
• Explain the mechanisms of trans- activities such as respiration, nutrition, motion,
porting the substances from and reproduction, responding to the surrounding
to the cell across the plasma mem-
brane.
environmental stimuli and so on. The cell processes are
• Briefly, explain the mechanism performed by the organelles and structures of the cell.
and steps of cellular respiration. In this chapter, we will study some of the cell processes.
• Briefly, describe the steps of pho-
tosynthesis.
• Explain some vital activities and Cellular transport
processes of the cell.

To maintain the cell living, it must perform its vital

functions thoroughly. So, it obtains some substances
from the surrounding medium and gets rid of the wastes
resulted into the surrounding medium once more and
continuously to the external environment. Naturally,
these exchanges can be only performed across the cell
membrane. The cell membrane is the passage through
which all the substances move from and to the cell.
Now, let’s raise the following question:
Key terms • What are the mechanisms by which substances
• Passive transport can be transported and exchanged between the
• Active transport
cell and its surrounding medium across the cell
• Diffusion
• Osmosis membrane?
• Facilitated transport
• Bulk movement • What is the role of the cell membrane in organizing
• Exocytosis this exchange?
• Endocytosis
• Respiration Cell membrane is characterized by its property of
• Photosynthesis selective permeability. In other words, some substances
such as oxygen, water, and carbon dioxide can pass
through it and other substances such as macromolecules
can’t pass through it. This depends on several factors
such as the size and charge of the substance and the
difference of its concentration on the two sides of
the cell membrane. Generally, the mechanisms of
transporting the substances across the cell membrane
can be summing up in the following:
52
First: passive transport:
It is the movement of substances across the cell membrane without consuming
energy by the cell. It includes the following mechanisms:
A B
1 Diffusion: It is the movement of the
molecules across the cell membrane from
a highly concentrated region to a low
concentrated one until the concentration
of the molecules gets equilibrium on both Figure 40-A: The molecules diffuse into the cell
Figure 40-B: finally the concentration of the molecules
sides of the membrane. For example,
becomes equal in and out the cell.
exchanging oxygen and carbon dioxide Predict: What would happen if the concentration
between the internal and external medium of molecules outside the cell is less than their
of the cell during respiration. concentration inside the cell?

2 Osmosis: Osmosis is the diffusion of water (without the dissolved substances

in it) across the cell membrane from the less concentrated side of the dissolved
substances to the more concentrated side of dissolved substances. It is known that
the cell cytoplasm is a fluid made up of water and several dissolved substances.
Due to the difference in concentration between the cytoplasm (inside the cell) and
the surrounding medium of the cell (outside the cell), water moves from or to the
cell by the osmosis.
You can identify the effect of the concentration of solutions in the external environment
on transporting the water from and to the cell through figure 41 which illustrates
the results of mixing the blood with salty solutions of different concentrations.

The cell is in a hypertonic solution The cell is in an isotonic solution The cell is in a hypotonic solution (the cell
(the cell loses its water and (water dose not transport and the cell tears down due to absorbing the water)
shrinks) remains in its natural state)

Figure 41: The effect of osmosis of differently concentrated solutions on the erythrocytes. What is the direction
of water movement in each case of the three cases above

Be interconnected with the activities and exercises book: Practical activity: Osmosis

3 Facilitated transport: It is the transportation

of molecules of the substances through the cell
membrane by a carrier from the proteins of the
membrane itself without consming energy by the
cell to transport it,figure 42, and it is performed
according to the concentration gradient. For Figure 42: The facilitated transport
example, transporting glucose from the blood into where the protein carrier transports
the molecules from outside to inside
the body cells.
the cell

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 Second: Active transport:
It is the process of transporting molecules or ions against their concentration
gradients through the cell membrane. In other words, from a high concentrated side
to a low concentrated one using the energy.
Active transport is much important in keeping the concentration of ions inside
the cells. For example, the animal cell dismisses sodium outside it and pulls the
potassium inside it which is against the concentration gradient in each of them.
This graduation in the concentration of sodium and potassium is necessary for
contracting the muscle cells and transporting the nerve impulses. It is also the same
with respect to the plant cell, the active transport enables the roots to absorb the
ions of salts from the soil, however the concentration of these ions in the root cells
are higher than their concentration in the soil.

3 outside the cell Protein carrier

2 1

inside the cell

P ATP big molecule
P
Figure (43):Active transport of molecules and ions against the concentrion gradient through the membrane -
bound carrier proteins with the using of energy of ATP. Describe what happens in each of these three steps.

Third: Bulk movement:

In this type of cellular transport, the relatively big molecules such as protein molecules
or cell wastes are transported through the cell membrane. If these substances are
transported from inside the cell to its outside, then the process is called exocytosis,
figure 44. If these substances are transported from outside the cell to its inside, then
the process is called endocytosis, figure 45.

outside the cell

outside the cell

2 2
3 Cytoplasm 1
Cytoplasm
1 3
Figure (44): Exocytosis Figure (45): Endocytosis

In exocytosis, Golgi apparatus packs up the cell wastes in vesicles, called Golgi
vesicles. They move through cytoplasm in the direction of the cell membrane to
fuse with it then they discharge their contents outside. While in the endocytosis,

54
a part of cell membrane bends to surround the substance to form a sac-like or
vacuole-like around it. After that, this sac is transported into inside the cytoplasm. If
the substances entered by this way are solid, the process is called phagocytosis but
if the substances are liquid then the process is called pinocytosis.

Photosynthesis
Photosynthesis is the process by which green plants provide the energy that plants
use to perform different biological functions such as feeding, growth, reproduction
and so on. Photosynthesis is conducted inside chloroplasts in two stages. During
these two stages, light energy is converted into chemical energy, figure 46.
First stage:
It occurs inside the grana (present in chloroplasts) and starts by capturing the
energy of sunlight by the chlorophyll pigment, then using a part of this energy to split
water molecules into oxygen and hydrogen, while the other part of the absorbed
energy is stored in the form of the compound ATP. The oxygen rises up outside the
plant leaves, while the hydrogen moves to the stroma of the chloroplasts.
Second stage:
It occurs inside the stroma. The energy stored in the ATP compound is used to
combine hydrogen and carbon dioxide to form glucose sugar.

1. Plants use light energy of

sun to perform photosynthesis.

4. The oxygen produced during

photosynthesis gets out through
the leaf while the hydrogen
remains inside the chloroplasts.
3. A part of light energy of sun
absorbed is used in chloroplasts
chloroplast
to split water molecules into
oxygen and hydrogen.

2.Chloroplasts in plant cells

absorb the light energy of the sun
oxygen

carbon 5. The remained part of the light energy

dioxide
of the sun in the chloroplasts is used
to combine hydrogen molecules with
carbon dioxide molecules to form
glucose. In this way, the energy is stored
in the glucose.

Figure (46): Photosynthesis

Photosynthesis equation:
Energy of sunlight
carbon dioxide + water glucose + oxygen
Chlorophyll

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 Cellular respiration and energy release

Plant and animal cells use glucose to obtain the energy stored in it, but these cells
cannot obtain this energy without breaking down glucose molecules into simpler
molecules by oxidizing the glucose. This process is called cellular respiration which
can be defined as a group of chemical reactions in which the glucose molecules is
exposed to them inside the cell in order to release the energy stored in it.

glucose
energy water

small molecules

energy

oxygen mitochondria carbon dioxiede

Figure 47: The first stage of respiration occurs in cytoplasm and little amounts of energy are released. The
second stage occurs in mitochondria and large amounts of energy are released.

During cellular respiration, glucose molecules Enrichment

are broken down into water and carbon dioxide. The Cellular respiration occurs
energy stored in the form of a chemical compound in all living organisms
and in all times, whereas
called adenosine triphosphate (ATP) is released.
photosynthesis occurs only
in the plants in the presence
of sunlight.
Test your information:
✍ Through your study of metabolism, explain that: is the process of
glucose oxidation considered a process of anabolism or catabolism.

Be interconnected with the activities and exercises book: Assessment activity

56
 Science, technology and society

1 Stem cells:
Recently, scientists have discovered that there
is a type of cells has the ability to form any other
type of specialized cells such as muscle cells, liver
cells, nerve cells and skin cells. This can be done
according to specific environmental treatments at the
laboratory. These cells are called stem cells. These
cells are formed during the early stage of forming the
embryo. As a result, scientists and doctors are hoping
to use such cells to treat a group of intractable diseases
such as using these cells to produce dopamine used
Embryo cells in the early growth
to treat those suffering from Parkinson disease or to stages.
transplant stem cells to give cardiac muscle cells as
compensation about the damaged cardiac muscles
in heart patients or getting cells producing the insulin hormone as a compensation
about the decrease of secreting this hormone by pancreas for diabetes patients and
other diseases.

2 Cell fractionation:
Technology of cell fractionation is one of the modern
technologies used to study each type of different cells
forming a certain tissue. Studying the different organelles
forming one type of cells includes studying the site of
these organelles, their functions and their components.
Cell fractionation technology benefits in studying the
cellular molecules such as biological macromolecules
like enzymes. Furthermore, studying biological processes
occurring inside the cell.
The Cell fractionation technology depends upon
using ultracentrifuge apparatuses to separate cell
organelles at different speeds depending on the different
Ultracentrifuge
densities of these organelles.

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 Key terms
• Cell theory: It states that the cell is the basic functional unit of all living
organisms. Organisms are composed of cells and these cells may be single or in
groups. All the cells originate from pre - existing cells.
• Prokaryotic cell: It is the cell which its genetic material is not surrounded by
a nuclear envelope and membranous organelles are absent from it.
• Eukaryotic cell: It is the cell which its genetic material is surrounded by a
nuclear envelope and contains most cellular organelles.
• Parenchyma tissue: It is a tissue made up of irregular sheped cells with thin
walls. It performs several functions such as photosynthesis, storing nutrients such
as starch, and aeration.
• Collenchyma tissue: It is a living tissue and its cells are somewhat rectangular-
shaped. It has thickened, irregular walls uncovered with legnin.
• The sclerenchyma tissue: It is a tissue strengthening and supporting the plants
and protecting the internal tissues.
• Epithelial tissue: It is a tissue covering the surface of the body from the outside
to protect it from external stimuli such as temperature, drought, and pathogens.
• Connective tissue: The cells of this tissue are somewhat distant and present in
fluid, semisolid, or solid intercellular substance.
• Muscular tissue: Its cells are known as muscle cells or muscular fibers. It is
distinguished from all the body cells with its ability to contract and relax.
• Nervous tissue: Its cells are specialized in receiving the sensory stimuli.
• Chromosome: It’s a structure appearing in the metaphase of cell division. It is
composed of two filaments each of them called chromatid. They are connected
at a central part called centromere.
• Active transport: The process of transporting macromolecules or ions aganist
their concentration gradient across the cell membrane.
• Diffusion: The movement of molecules through the cell membrane from a high
concentrated area to a low concentrated one until the concentration on both
sides of the membrane gets equilibrium.
• Osmosis: The diffusion of water through the cell membrane from the high
concentrated side of water (less concentration of dissolved substances) to the
low concentrated side of water (more concentration of dissolved substances).

58
 Concept map of chapter two

Living organisms
The structural and functional units are

Cells

Perform several vital processes Divided into

Cellular respiration Photosynthesis Cellular transport Eukoriotic cells Prokaryotic

cells
Results in Results in Its mechanisms

Contain

Eenrgy + Glucose +
CO2+H2O Oxygen
Cell membrane Nucleus Cytoplasm

Contain Contains

Bulk transport Active transport Passive transport Nucleolus

Cellular organelles

Chromosomes
Includes the following Comprises the following
mechanisms mechanisms Are

Endoplasmic rectilum
Exocytosis Diffusion

Golgi apparatus
Endocytosis Osmosis

Mitochondria
Facilitated transport
Lysosomes

Vacuoles

Plastids

Ribosomes

Centrosome

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 Unit Three

Inheritance of Traits

We have blue, brown, green and gray eyes. Also, we have hair of different
colours - black, brown and blonde. We see the ornamental sparrows with green,
blue and yellow feathers. From where all these colours of living organisms come?
How do these characteristics transmit from parents to their offspring?
The ancient prevailing belief before mendel`s experiments was that these colours
are produced by the colours mixing theory. It is believed that the hybridization
between two parrots, one with yellow feathers and the other with blue ones, will
produce parrots with green feathers.
Recently, after discovering the chromosomes and the traits they carry on, the
concept of traits inheritance has been changed and becomes obedient to laws and
mechanisms which control the transmission of traits from a generation to another
generation. The prediction of traits appearance in the produced individuals becomes
more accurate and this helped in the prediction of genetic disorders in the offspring.
This aggrandizes the importance of the medical examinations before marriage to
avoid the transmission of genetic diseases to offspring.

For mo
r e inform h e net .
ation about log in t
the topic of Inheritance of Traits,
 Time management:
To achieve the maximum benifit of this unit, you need to:
• Manage your time between practical and theoretical study, search and
extending of information resources.
• Carefully, record the results of your practical study which is the best way to
support your learning.

Learning outcomes:
By the end of this unit the student should be able to:

• Explain the chromosome theory. • Mention some sex-linked, sex-influenced and sex-
• Identify what is meant by the karyotype. limited traits.
• Identify the number of chromosomes in some living • Distinguish between some abnormal cases of
organisms. chromosomes in humans.
• Explain the mean of linkage. • Mention some methods used to predict the likelihood of
• Identify what is meant by crossing over. genetic disorders occurring in offspring.
• Demonstrate the effect of genes interaction. • Appreciate the importance of medical examinations
• Explain the effect of the environmental conditions on the before marriage to avoid the genetic diseases.
action of some genes. • Use the pedigree in explanation the inheritance of some
• Explain how blood groups are inherited in humans. traits.
• Explain how rhesus factor is inherited.
• Explain the role of sex chromosomes in sex determination.

1:Chro
Ch

Ch d ses
Ch
 Unit Three
Chapter 1

Chromosomes and genetic information

By the end of this chapter, you From a long time ago, man searches about how do
Should be able to: genetic traits transmit across the successive generations
• Explain the chromosome theory. and the causes of similarities and differences in genetic
• Clarify the relation between the
chromosome and gene. traits.
• Identify what is meant by the karyotype
in humans.
At the beginning of the twentieth century, scientists
• Identify the number of chromosomes in discovered that genetic information are carried on the
some living organisms. chromosomes which lead to the appearance of traits in
• Compare between the karyotype of the
male and female humans. all living organisms.
• Explain the meaning of the linkage.
• Identify what is meant by crossing over.
The chromosomes are located inside the nucleus
of each cell. They are found in homologous pairs in the
somatic cells.
The following figure illustrates the chromosomes in
cells of humans pancreas and white blood cells.

Key terms
• Chromosome
• Chromosomal theory
• Gene
• Karyotype
• Crossing over Cells of pancreas The chromosomes of a pancreatic cell

White blood cells The chromosomes of a white blood cell

Figure (1): Different cells and chromosomes.

62
 Karyotype
We can photograph the chromosomes when they
are in the clearest form using the microscope, then be
Enrichment
chromosomes are found in
demarcated and classified into homologous pairs.
homologous pairs. Their number
After that, they arranged descendingly according in cells of the living organism
to their size. To facilitate carrying out of this task, dosen't express the degree of its
chromosomes can be coloured with different colours. advancement or its size.

The descending arrangement of chromosomes

according to their size and numerating them are called the karyotype.

Be interconnected with activities and exercices book: Applied activity: Karyotype model

The following figures illustrate the karyotype of both the human male and
female.

Observe and identify:

Figure (2): Karyotype of a human male Figure (3): Karyotype of a human female

• How many pairs of chromosomes in both Karyotypes of the male and female?
• What is the difference between the Karyotype of both the male and female?
Number of chromosomes:
The number of chromosomes in living organisms differs from a species to another,
but it is constant in the individuals of the same species. Somatic (body) cells contain
two sets of homologous chromosomes (one of them is inherited from father and
the other from mother). These ells are called the diploid cells (2N), while gametes
(sperms and pollens are male gametes and ova are female ones) contain half of the
chromosomes number found in the somatic cells, i.e. they are haploid cells (N).For
example, the nucleus of each human somatic cell contains 46 chromosomes (23
pairs), while the nucleus of both the male gamete (the sperm) and female one (the
ovum) contains 23 chromosomes only.

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 • Chromosomes are descendingly arranged in homologous pairs according to
their size from number (1) to number (23). The pairs from number 1 to number
22 are called somatic chromosomes, while the pair number 23 represents the sex
chromosomes. This pair is not subject to this arrangement where it comes after
the seventh pair in size, but it is arranged at the end of chromosomes and given
the number (23).
• The karyotype of male differs from that of the
female in the pair of sex chromosomes. This pair
is asymmetric (heterzygous) in male (XY) (Fig. 4)
and symmetric (homozygous) in the female (XX)
(Fig. 4) and called the pair of sex chromosomes
because it carries the genetic information of sex
determination.
• The constancy of the chromosomal number in
both the males and females of all members the
human race indicates that chromosomes carry the Figure (4): The sex chromosomes pair
(XY).
genetic information which determine the characters
of humans and other living organisms.
✲ The following table represents the chromosomal number in cells of some
living organisms:
Table(1): The chromosomal number in cells of some living organisms‫ﺓ‬

No. of chromosomes in the No. of chromosomes in the

Species Species
somatic cells somatic cells

Human 46 Gorilla 48

Wheat
Hen 32 42
Plant

Onion
Cat 38 16
plant

Sweet
Vinegar
8 potato 48
fly
plant

Dog 78 Pea plant 14

Tobacco
48 Frog 26
plant
✍ what can be concluded from this table?

64
 Chromosome theory
By 1902, the two scientists Sutton and Boveri had reached to the priciples of
chromosome theory which can be crystallized in the following main points:
• Chromosomes are found in the somatic cells as Enrichment
homologous pairs (2n).
Scientists found that there
• Sex cells (gametes) contain the half of chromosomal are 60-80 thousands genes
number (n) due to meiosis where the pairs of carried on twenty three
homologous chromosomes are segregated into two pairs of chromosomes in
equal sets of chromosomes. humans. The complete set
of genes in known as the
• Each pair of chromosomes behave independently at human genome
its transmission in gametes.
• During fertilization the diploid number of chromosomes returns again.
• Genes are located on the chromosomes and the single chromosome may carry
hundreds of genes.

Chromosomes and genes

The chromosome is composed of the nucleic acid DNA and protein. DNA
molecule carries the genes responsible for the genetic traits in living organisms.
You have learned that DNA consists of building units called nucleotides. The
gene consists of a sequence of nucleotides that represents a code of a protein
responsible for the appearance of a certain trait.

Interpretation of Mendel’s laws according to the chromosome theory:

The opposite figure illustrates the inheritance of a pair of allelomorphic
(contrasting) characteristics in pea plant:
P
✍ What is your explanation for the
appearance of the purple colour only
in the first generation plants? F1

✍ What is your explanation for the

appearance of the two colours in plants F2
of the second generation?
• In the meiotic division, the genes carried Figure (5) : Law of genetic factors
segreation
on the chromosome pairs are segregated
into the gametes, and during fertilization the
chromosomes return back again in pairs.
• The dominant trait appears in the first generation in a percentage 100%. The
dominant and recessive traits appear together in the second generation in a ratio
3:1 , respectively.

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 • The opposite figure explains the inheritance
of two pairs of the characteristics studied P
by Mendel in his experiments, such as: the y y s s Y Y S S

colour and shape of seeds in pea plants.

The yellow colour gene (Y) of seeds is G y s Y S

dominant on the green colour gene (y), and the

smooth shape gene (S) of seeds domiates over F1
the winkled shape gene (s). Y y S s

✍ Are the genes of seeds colour and that of seeds

shape located on the same chromosome or P.
Y y S s Y y S s
on two different chromosomes?
✍ What are the possibilities of genes
assortment into the gametes?

Y
S
Y

S
✍ What are the ratios of the appearance

Y
s
Y

s
of the two characteristics in members of

y
y

S
both the first and second generations?

y
y

s
• The assortment of genes carried on the
chromosomes in gametes is independent
because each gene is located on a separate
chromosome. F2
• The individuals of the first generation carry
the two dominant characteristics (the yellow Figure (6) : Law of independent
colour and smooth shape) in a percentage assortment of genes
100%.
• The ratio is 9:3:3:1 in the individuals of second generation.

Linkage of genes and crossing over

During his studying the inheritance of traits in

Drosophila insect (Fruit fly) , the scientist Thomas
Morgan noticed that there were several hundreds
of genes while four chromosomes only were found
(Fig.7).
This means that each chromosome carries a
number of genes inhereted together as one unit.
This contradicts the law of independent assortment
Figure (7) : The chromosomes of
which states that genes are found independently on Drosophila insect.
the chromosomes and assorted independently , i.e.
Mendel’s second law is not a general law.

66
 Morgan hypothesized that the linking of these genes together is due to their
presence on the same chromosome and the intensity of linking between genes
depends on the distance between the neighbor genes on the chromosome.

Types of linkage between genes :

The linkage between genes depends on the distance Grey with long wings Black with vistigial
wings
between these genes on chromosomes:

The complete linkage:

The opposite figure explains the inheritance of G G g g
.P
two paris of traits that Morgan had studied in his L L l l

experiments on Drosophila insect such as the body

G g
colour and wing length. .G
L l

The gray colour gene (G) of the body dominates

over the black colour gene (g) , and the long wings
gene (L) dominates over the vistigial wings gene (l). Grey with
long wings
✍ Are the genes of body colour and wing length F1 G g
insects L l
are located on the same chromosome or on
two different chromosomes?
✍ What are the possibilities of gene assortment
into the gametes? G g G g
P.
L l L l

✍ What are the ratios of appearance of the two

traits in the members of the first and second G. G g G g
L l L l
generations?
• Gene assortment does not take place in gametes
according to the law of independent assortment.
Genes carried on the same chromosome are G G G g G g g g
F2
transmitted as one hereditary unit, i.e. they are L L L l L l l l

inherited as one trait. Grey with long Black with

• The genes carried on the same chromosome do wings vistigial wings

not remain linked together unless they are very close Figure (8) : Complete linkage in
to each other on the same chromosome. Drosophila insect

• The complete linkage leads to the stability of

genes inheritance , i.e. stability in traits inheritance.

Incomplete Linkage :
In some genetic cases, the genes carried on the
same chromosome do not remain linked permanently,
but they may separate from each other and exchange
with other genes located on the analogous chromosome
due to the crossing over phenomenon that takes place Figure (9) : Crossing over
during meiosis and gametes formation. This leads to the phenomenon under the
appearance of new traits among the offspring. microscope.

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 Crossing over:
The crossing over phenomenon occurs during prophase of first stage of meiosis.
G L

g l
Duplication of
chromosomes G L
G L

Tetrad G L
Parental gamete
g l
g l

G l
G L
G l Recombinant
Chiasma and
g L gametes
crossing over g
g l L (new)

G L
G l
g l
Parental gamete
Separation of
chromosomes.
g L
g l

Figure (10) : Steps of crossing over.

In prophase I:
• The paris of homologous chromosomes approach to each other, and form the
tetrad where each pair of chromosomes contain four sister chromatids.
• The internal chromatids in the homologous pair of chromosomes remain in
contact with one another for some time , touching at certain points called
chiasmata at which some breaks appear.
• Exchange of the corresponding parts of the internal chromatids in the
homologous pair of chromosome then take place. This process is known as
crossing over.

In anaphase I :
The homologous pairs of chromosomes separate from each other, after
occurrence of crossing over into two sets of chromosomes.

In anaphase II :
The chromatids separate and move away from each other. These chromatids being now
independent chromosomes called daughter chromosomes, then they are assorted into
the gametes randomly.
Be interconnected with activities and exercises book: Applied activity: Model of
chiasma and crossing over

68
 The chromatids that the crossing over happen in them are called new
chromosomes , while the ones the crossing over does not occur in them are called
parental chromosomes. Therefore, there are gametes contain parental chromosomes
and other gametes contain new chromosomes.
Crossing over is an incomplete linkage of genes on the chromosomes. It
changes the traits in certain ratios that depend on the distance between the genes
on the chromosome. The chances of crossing over occurrence between the genes
on the chromosome increases as the distance between these genes increases on the
chromosome.

Importance of crossing over

Crossing over phenomenon leads to the diversity in the traits among the
members of the same species which helps in their adaptation with the environmental
conditions and their survival and evolution.

The chromosomal maps:

By studying of the ratios of crossing over, scientists were able to determine the
locations of genes on the chromosomes by using what is known as the chromosomal
maps.

Be interconnected with activities and exercises book : Assessment activity.

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Unit Three

Chapter 2

The interaction of genes

By the end of this chapter, you

Should be able to: Gregor Mendel arrived to that each trait is controlled
• Demonstrate the effect of genes by one pair of genes, one of them is dominant while the
interaction.
• Mention the mean of lack of
other is recessive. Later, scientists found that several traits
dominance. were not inherited according to Menel's laws and called
• Explain the lack of dominance. non-mendelian characteristics. They include cases in which
• Explain the conplementary genes.
• Explain the lethal genes.
the emergence of gentic traits is affected by the interaction
• Explain the inheritance of blood of the allelomorphic genes.
groups in humans.
• Show the bases of classifying blood
into four groups.
Remember
• Identify a blood group.
• Gompare the four blood groups.
• Each pair of alternative character is calld
• Explain how rhesus factor is inherited. allelomorphic characters.
• Analyze inheritance of some traits on
genetic bases.
• In case of Mendelian chracter: when crossing occurs
• Explain the effect of the environmental between to pure (homozygous) indiviluals, one of them having
conditions on the action of some the dominant chracter and the other having the recessive
genes.
one, the individuals of the first flial generation will all show
the dominant chracter. While the tow chracters,the dominant
and recessive, appear together in ratio 3 : 1, respectively, in
Key Terms the second flial generation. This genetic pattern is called the
• Complete dominance complete dominance.
• Lack of dominance
• Complementary genes
• Lethal genes • Examples of gene interaction are: lake of
• Blood groups dominance, complementary genes and lethal gene.
• Antigens
• Antibodies
• Rhesus Factor (Rh)
Lack of dominance
In Antirrhinum plant, the flowers are chracterized
by three colours: red, white and purple. The following
figure illustrates crossing of a plant with red flowers
(RR) with another plant with white flowers (WW).
✍ What is the flower colour of the first
generation plants?

70
 ✍ What are the possible genotype of first Red flowers White flowers

generation individuals?
P
✍ When first generation plants are self
polinated and their seeds are cultivated,
RR WW
What are the possibilities of the flowers
colour inheritance in plants of second F1
generation?
Purple flowers
✍ What is the ratio of the flowers colour in RW
plants of second generation
F2 R W
✍ Do these results agree with Mendels
laws?
The gentic analysis (fig.11) illustrates that the R
Red flowers Purple flowers
flowers colour chracter is controlled by a pair of RR RW
genes, no one of them dominates over the other.
This happens due to the gene interaction where
each one of these allelomorphic genes has an W
effect in the appearance of the new chracter. Purple flowers White flowers

RW WW
• Notice that the phenotype indicates the Red flowers Purple flowers White flowers

genotype in case of lack of dominance. 25٪ 50٪ 25٪

1 : 2 : 1

Inheritance of blood groups in humans: Figure (11): Inheritance of flowers

Despite of blood components are constant colour in Antirrhinum plant.
in all humans, but they differ in blood groups.
Blood transfusion processes depend on the type Enrichment
of blood group and the type of rhesus factor. The 14th day of
The blood groups chracter is controlled by june is the univeral
day of blood
3 types of genes called alternatives (allels). The
donation. This day
individual inherits one pair only (multiple allels). agree the birthday
These genes are symbled by letters A-B-O. These of Austrian scientist
genes are located on the ninth chromosome pair Karl Landsteiner,
in all humans. the discoverer of
blood groups.
Genetic classification of blood groups:
Blood groups include three patterns in heredity, they are: Table (2): Blood groups and
their genotypes
✲ Multiple allels: Blood groups trait is carried by three
allelomorphic genes: A,B and O. The individual has only Group Genotype
one pair of them. A AA AO
✲ Complete dominance: Both genes (A) and (B) B BB BO
dominate over the gene (O). AB AB
O OO

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 ✲ Lak of dominance: There is dominancy between gene (A) and gene (B). They
participate together in production of a new trait, which is AB blood group.
The opposite diagram shows mating group O group AB
of a man has blood group (AB) and a
woman (O). P. OO X AB

✍ What are the expected blood

groups of offspring?
G. O A B
✍ What is the ratio of blood group
among offspring?
✍ Are there possibilities of other
F1 AO BO
blood groups?
Figure (12): Genetic analysis of blood group
Chemical classification of blood inheritance.
groups: Table (3): A table shows blood groups
classification
Classification of blood groups into four groups (A), The Antigens Antibodies
(B), (AB) and (O) depends upon two types of subsfances group
found in blood. Thes substances are divided into two
types: A A anti-b
B B anti-a
Angifgens:
AB A and B -------
They are the substonces that found on the surface ------- anti-a
of red blood cells. They are two types: antigen (A) and O anti-b
antigen (B).

Antibodies: Life application

These substances are antithetic to
antigens and found in blood plasma. They A dispute took place between two men
are two types: (anti - a) and (anti - a). about the eligility of each in the parenty
of a baby has the blood group (O). The
✍ Use table (3) to compare between the blood group of both men was (O) and
four blood groups. blood group of the first man wife was
(A) while the blood group of the cecond
Importance of blood groups : man was (AB)

1 Dispute resolution in determining

paternity and enrollment children to their real parents (blood groups can
denying but can not pove the parevtage).
2 Determining the processes of blood transfusion among individuals.
3 Used in studies of human race taxonomy and studying evolution.

Blood transfusion processes:

Blood can be transfused between different groups according to a specific system
due to the presence of antigens and antibodies.

72
✲ Table (4) shows the possibilities of blood transfusion between different groups:
Table (4) Blood transfusion system

The donor
O
O AB B A

The receiver
A ✓ ✗ ✗ ✓
A B B ✓ ✗ ✓ ✗

AB ✓ ✓ ✓ ✓

Figure (13): Blood

AB O ✓ ✗ ✗ ✗
transfusion system

✍ What is blood group that called universal receiver? Why?

✍ What is blood group that called universal donor? Why?
The following table summarizes some information of the four blood groups:
Table (5): Blood groups

Group Genetic structure Antigens Antibodies Donates to Receives from

A AA AO A anti-b A and AB A and O

B BB BO B anti-a B and AB B and O
AB AB A and B ----- AB All groups
O OO ----- anti-b anti-a All groups O
Anti- a Anti- b
Determination the type of a blood group:
Each group of blood has certain antigens and their
corresponding antibodies. For example: A

The antigens (A) are agglutinated with antibodies (a). (+) (-)

Through the reactions that take place between

antigens and antibodies and occurrence of blood B
agglutination, the type of a blood group can be
determined. (-) (+)

Procedure of blood group type determination:

To determine the blood group, both types of antibodies, AB
anti-a and anti-b, are needed:
(+) (+)
1 A blood sample is drawn from the person to be
determining his blood group. Then two drops of O
blood are placed on clean glass slide.
2 We put anti-a on a drop of them and anti-b on the (-) (-)
other drop.
Figure (14): Blood group
determination
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 3 The result: There are four possibilities, which are :
Table (6): Determination of blood groups

First blood drop Second blood drop The possible blood group

1 Agglutination (+) No agglutination (-) A

2 No agglutination (-) Agglutination (+) B
3 Agglutination (+) Agglutination (+) AB
4 No agglutination (-) No agglutination (-) O
• Discuss your classmates and your teacher about the results in this table.

Life application
Risks of blood transfusion:
There are some risks related to blood transfusion that the reciver exposed to:
• When an incompotible blood with his blood group is transfused to
him. This includes symtoms such shiver, headache, chest pains,
breath lessness, blueness, tachycardia, hypotension and often
ends with death.
• A viral infection can be transferred to the receiver as hepatitis
C which its infection takes place by blood transfusion only
since it does not transferred among couples or from the
mother to the fetus, and AIDS viruses.
Blood is subjected to a range of blood tests to make sure that it is
Blood transfusion free of pathogens such as: viruses, as well as it is compatible with
the receiver's blood..

‫ﹴ‬Rhesus factor (Rh):

Beside the antigens of blood groups, there is another type of antigens on the
surface of red blood cells known as Rhesus factor antigens. These antigens are found
in blood of almost 85% of human beings who are known as positive Rhesus factor,
and symboled as (Rh+). While, the persons who have no this type of antigens in their
blood and represent about 15 % of hunan beings are known as negative Rhesus
factor, and symbled with (Rh-).
The inheritance of Rhesus factor antigens is controlled
by three pairs of genes, located on a pair of chromosomes.
The presence of any gene or more of these three gene
pairs in the dominat statae leads to the formation of rhesus
factor antigens, and the person becomes positive Rhesus
factor (Rh+), whereas all genes of the negative Rhesus
factor individual (Rh-) are recessive. Figure (15): A red blood
cell
Importance of Rhesus factor:
Rhesus factor determination should not be neglected before blood transfusion,
as well as before marriage to avoid risks arising from the formation of antibodies for
Rhesus factor antigens that cause disintegration of red blood cells.

74
Role of Rhesus factor in pregnancy and delivery:
If a (Rh+) man is married to (Rh-) woman, and the fetus
Enrichment
Rhesus factor antigens
inside the uterus was (Rh+) , a portion of fetus blood mixes
were first discovered in
with his mothers blood at delivery. This stimulates her 1940 when researches
immune system to produce antibodies against antigens were carried out on
of Rhesus factor and these antibodies remain in mother's blood of a kind of
blood. monkeys called Rhesus
monkeys.
If the mother carried (Rh+) fetus, the antibodies formed
Therefore, these antigens
from the first pregnancy move from mother's blood to
were given the name of
blood of fetus through placenta (fig. 16). These antibodies Rhesus factor.
cause the disintegration of red blood cells infecting the
fetus with sever anaemia that may lead to his death.
-
Rh
The preventive measure that we can do in case of
discovering this difference before the delivery of the first
baby is the injection of mother with a protective serum antibodies

through 72 hours after each birth to protect the future +

Rh

baby.
This serum disintegrates the blood containing (Rh+) Figure (16) : Transferring of
that leaked from blood of fetus to mother's blood before antibodies from mother's blood
enhancing mothers immune system to form antibodies. to the blood of second fetus
through mothers placenta.

Complementary genes
Complementary genes are
the genes that can often work
together to emerge a specific
trait, where the inheritance of
this trait is controlled by 2 pairs
of genes. The emergence of the
dominant character depends
on the presence of a dominant
gene at least in each pair.
While, absence of any pair of Figure (17) Pea flower plant.

dominant genes or both, will lead to disappearouce of the dominant character and
the recessive allelomorphic character appears.
An example of complementary genes is the inheritance of the flower colour
character of pea flower plant. The pink colour represents the dominant trait while
the white colour represents the recessive one, fig.17.
The character of flower colour in pea plant is carried by two different pairs of
dominant genes and symboled by the two letters A and B , while the recessive genes
are symboled by a and b .

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 The opposite figure shows the White flowers White flowers
crossing of 2 stains of pea flower plants,
each of them carries white coloured P. AA bb X aa BB
flowers.
✍ What is the flowers colour of
first generation plants? G. Ab aB
✍ What are the possible genotypes
of individuals of this generation? Aa Bb
✍ When self - pollination was F1 Pink flowers

carried between the first generation Pink flowers Pink flowers

plants, then their seed were cultivated, P.
what are the possibilities of the flower Aa Bb X Aa Bb
colour character inheritance in second
generation plants? F2 Gametes AB Ab aB ab
✍ What is the ratio of emergence AB AA BB AA Bb Aa BB Aa Bb
of flower colour in second generation Ab AA Bb AA bb Aa Bb Aa bb
plants?
aB Aa BB Aa Bb aa BB aa Bb
✍ Write down the different
genotypes for each of the pink flowers
ab Aa Bb Aa bb aa Bb aa bb
and white ones. Pink flowers White flowers

✍ Are these results in agreement 9 : 7

with Mendels second law (Law of Figure (18) : Inheritance of flower colour in pea
independent assortment) ? plants.

When white flowered pea plants were crossed Apply what did you
together , all the flowers of the first generation plants learned..
have learned
appeared pink (in a ratio 100%). In the second Show on genetic
generation, the flower produced were pink and white bases the phenotypes
in a ratio 9 : 7 , respectively. and genotypes of
flowers colour in pea
The appearance of pink colour (dominant character) plant resulted from the
in flowers of pea plants depends on gathering a dominant following crosses :
gene from each pair or more , because both of the two Aabb X aaBb
dominant genes participate to produce the pink colour AaBb X aabb
of flowers where each of them controls the production
of a specific enzyme that affect the formation of pink
colour. This indicates the complement of action of genes , where in this case the
dominant character can be obtained from two parents , each carries the recessive
character.
The ratio of the second generation in case of Mendelian characters (law of
segregation of factors) is 9 : 3 : 3 : 1 , while the ratio of second generation in non -
Mendelian characters (complementary genes) is 9 : 7 .

76
 Lethal genes
.
Some genes when present in a homologous condition (pure) cause harms to the
living organism resulting in disruption of some vital processes leading to the death
of organism at different stages of life .
✲ These genes are called the lethal genes. There are two types of these genes,
which are:
1 Dominant lethal genes : such as yellow fur colour in mice and bulldog strain in
cattles.
2 Recessive lethal genes : such as absence of chlorophyll in corn plants and
infantile dementia in humans.

Inheritance of fur colour of mice:

The opposite figure shows mating of a
male and a female mice. Each of them has a
heterozygous yellow fur and the ratio of the
resulted generation was 2 : 1.
✍ What is fur colour of the resulted P. Yy Yy
generation?
✍ What are the possible genotypes of G. Y y Y y
individuals of this generations?
✍ Why do these results disagree with
Mendel`s first law (law of segregation
F1 YY Yy Yy yy
of factors) ?
Homozy-
✍ What is percentage of loss of mice gous yellow
mice die
first generation? inside mothers Yellow mice Grey mice
uterus.
The death of pure yellow mice is 2 : 1
attributed to presence of a pair of dominant Figure (19) : Inheritance of fur colour in
genes in a homozygous state causing death mice
of mice inside mother's uterus . These dead
mice represent about 25% of individuals of the Apply what did you
learned..
have learned
resulted generation. The inheritance of this disease
in some infnants, there
takes place through heterozygous parents.
is a genetic disease known
as infantile dementia causes
Inheriting the absence of chlorophyll in death when its genes are
corn plants: recessive (aa).
It was observed that when some corn plants What is result when a man is
were self pollinated and their seeds were cultivated, married to a woman , each of
them is hetrozygous in respect
some seedlings free of chlorophyll (white coloured)
to this trait?
were shortly grown , then wilt and die.

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 Study the opposite genetic analysis , then answer the following questions:
✍ What is the ratio of chlorophyll free
Green corn plant Green corn plant
seedlings among plants of the resulted
generation?
P. Cc Cc
✍ What is your justification for wilting
and death of these seedlings?
✍ From your point of view , how can G. C c C c
losing of plants be avoided and obtaining
all seedlings green? F1 C c
The convergence of the two recessive C CC Cc
genes together in some corn seedlings leads
c Cc cc
to prevention of chlorophyll formation.
Green seedlings 75%.
Chlorophyll substance acquires plants their
White seedlings 25%
characteristic green colour, as well as it is
responsible for absorbing light energy for
Figure (20) : Inheritance of chlorophyll in
performing photosynthesis process. corn plants

Effect of environmental conditions on action of some genes

Many people thought that the action of genes is not affected by any other factors.
But, recent researches has proven that the action of some genes is affected by the
factors surrounding the organism such as air pollutants , oxygen deficiency, exposure
to rays , in addition to the environmental factors such as light and temperature .
Studying these factors affecting the action of genes helps in avoiding risks that may
arise from these factors.
Effect of the absence of light on appearance of chlorophyll character in green
plants:
Germinate a group of wheat or
bean seeds in a dark room, and other
similar group in a luminous place.
Irrigate the seedlings in both groups
regularly for several days.
✍ What is the colour of seedlings
in both groups?
In presence of light In absence of light
The gene responsible for
chlorophyll formation in green plants Figure (21) : Effect of light on the colour of wheat
seedling's.
needs to the factor of light to show its
effect. While , in absence of this gene , the plant can not produce chlorophyll even
if it was placed in light.

Be interconnected with actcivities and exercises book: Practical activity: Effect of light on ap-
pearance of chlorophyll in green plants. Assessment activity.

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Unit Three
Chapter 3
Genetic inheritance and genetic diseases

By the end of this chapter,

you Should be able to:
Sex determination remains a dream for many
• Explain the role of sex chromosomes
in sex determination of the fetus. people a long time ago. The idea that the woman is
• Mention some sex-linked, sex- responsible for determination of her fetus sex, male or
influenced and sex-limited traits.
female, remained untile the midde of the last century.
• Analyze some sex-linked and sex-
influenced traits on genetic bases. By discovering sex chromosomes, scientists decided
• Use the pedigree to explain the that man is responsible for determining of the sex of
inheritance of some traits.
• State some methods used to predict
fetus.
the likelihood of genetic disorders ✍ How can you explain that the man is
occurring in offspring.
• Appreciate the importance of responsible for sex determination of the fetus?
medical examinations before
marriage to avoid the genetic
diseases.
Sex determination in humans
there are 23 pairs of chromosomes in each human cell.
these chromosomes are classified into 2 types:
1 Autosomes (Somatic chromosomes): their number
is 22 pairs. They are similar in both the male and
female.
Key terms
2 Sex chromosomes: their number is one pair only
• Klinefelter`s Syndrome and they are different in the male and female
• Turner`s Syndrome
• Down`s Syndrome
(Figure 22)
• Sex-linked traits
• Sex-influenced traits X
X
• Sex-limited traits
• Colour blindness
• Hemophilia
Y
• Baldness
• Albinism
• Polydactyly
• Genetic family tree X
Male Female
Figure (22): The sex chromosomes
✲ Female cells: contain 22 pairs of autosomes, and
an identical pair of sex chromosomes (44 + XX).

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 ✲ Male cells: contain 22 pairs of autosomes
and one different pair of sex chromosomes
(44 + XY). P. XY XX
• The chromosome (X) differs from
chromosome (Y) in size and type of genes
each carries. G. X Y X
• The opposite genetic analysis illustrates
the possibilities of giving birth of males and
females. F1 XX XY
✍ What is the possible chromosomal
structure for both of sperms and ova?
✍ What is the ratio of males to females? Figure (23): The possiblities of embryo
formation
• The male and female gametes are formed
by meiotic division of cells of gonads (testes in males and ovaries in females),
therefore gametes contain half of the chromosomal number found in somatic cells.
• The male produces two types of gametes at equal
ratios, sperms carry the chromosome (X) and other Enrichment
sperms carry the chromosome (Y). The female
In some animals, sex is
produces one type of ova carry the chromosome (X). determined according to the
• When the ovum (22 + X) is fertilized by a sperm environmental conditions.
(22 + X), a female embryo will be produced. For example, temperature
that the eggs of turtles are
• When the ovum (22 + X) is fertilized by a sperm exposed to, plays a role in sex
(22 + Y), a male embryo will be produced. determination. the eggs located
near soil surface with higher
• Sperms determine the sex of the embryo, not the temperature hatch females,
ova. while the eggs away from the
surface of the soil with lower
• The genes carried on the two chromosomes (X) and
temperature produce males on
(Y) that responsible for sex determination work at hatching
the first months of pregnancy.
• After 6 weeks of the beginning of pregnancy, the fetus which carries the
chromosome (Y) begins in production of hormones stimulate the tissues of
ganads (which are undifferentiated) to from the 2 testes, then the rest of male
genital organs are differentiated.
• After 12 weeks of beginning of pregnancy, the fetus which does not carry
chromosome (Y) begins in the formation of the 2 ovaries, then the rest of female
genital organs are differentiated.

80
 Abnormal chromosomal cases in humans
These abnormal cases take place due to errors in gametes formation. This leads
to the formation of abnormal individuals as a result of a reduction or an increase in
the number of sex chromosomes or autosomes.
✲ Examples of abnormal chromosomal cases:
Klinefelter’s syndrome:
In 1942, Dr. Henery Klinefelter had discovered this case. Klinefelter’s syndrome
(44 + XXY) takes place due to the fertilization of an abnormal ovum (22 + XX) by a
sperm (22 + Y).
The presence of an extra (X) chromosome leads to a disturbance in body
hormones where the genes carried on the chromosome (X) express in some way.
From the symptoms of this case:
A sterile male due to absence of the sperm generating cells, mental retardation
and appearance of some femenine characteristics such as: growth of the breasts in
size, tallness, growth of limbs more than the normal, and small testes .

Figure (24): Karyotype of klinefelter’s syndrome. Figure (25): Karyotype of turner’s syndrome.

• Observe the difference of the chromosomal number in each case.

Turner’s syndrome:
Turner’s syndrome (44+XO) occurs due to the
fusion between an abnormal gamete (22 + O) by a
normal one (22+X). The lacking of chromosome (X)
which carries genes of non- sexual characteristics
produces a female with several deformities.
From the symptoms of this case:
shortness, does not reach puberty due to lack of
sufficient amount of hormones, slow mental growth
and presence of some congenital defects in heart
and kidneys
Figure (26): Turner’s syndrome.
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 Down’s syndrome (mongolism):

Figure (27): Down’s syndrome Figure (28) : the karyotype of Down’s syndrome

• OBSERVE THE EXTRA CHROMOSOME NUMBER (21).

The child shown in figure (27) suffers from a case called mongolism.
✍ Describe the shape of his face and eyes.
Examine the karyotype in figure (28) which represents the mongolism, then
answer the following questions:
✍ How many chromosomes in this karyotype?
✍ What is the number of the abnormal pairs of chromosomes? What is
its type?
✍ Is this karyotype for male or female? Why?
✍ Is the emergence of this case is limited to a particular sex over the
other? Give reasons.
✲ In 1866, the British doctor Down had discovered the case of mongolism. It
results due to the fertilization of an abnormal gamete (a sperm or an avum)
carries the pair of chromosomes no. 21, so a child carries three copies of the
chromosomes no.21 in his body cells. It is an autosome. The child may be
male (45 + XY) or female (45 + XX).

From the symptoms of this case:

A retarded growh, shortness, oval face, flat back of the head, fingers and toes
are short, small ears, convex eyes, and mental retardation.
Be interconnected with activities and exercises book: Assessment activity

82
 Sex-linked traits
Scientists discovered that the genes of some body characteristics in many animals
are located on sex chromosomes (X and Y) and called sex- linked characteristics.
Thomas morgan is the first scientist discovered the sex- linked genes during
studying the eye XR XR colour chacter in Drosophila insect. He crossed white Xr Y
eyed males Drosophila whit red-eyed females.The following figure illustrates the
crossing of a white-eyed male Drosophila with red-eyed female for 2 successive
generation:

R R r
P

R r
G.

R r R
F1

R r R
G.

R R R r R r
F2

Figure (29): Inheritance of eye colour characteristic in Drosophila insects.

✍ What is the ratio of appearane of eye colour characteristic between

the males and females of frist generation?
✍ What is the ratio of appearance of eye colour characteristic between
the males and females of second generation?
✍ What is the sex of insects with white eyes among the members of
second generation?
✍ Does this case agree with Mendel’s first law (segregation of genetic
factors)?

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 Morgan noticed that when white-eyed males Drosophila were crossed with red-
eyed females, the members of first generation were red-eyed. This means that the
red eyes characteristic is dominant over the white eyes one. When members of first
generation were crossed with each other, red-eyed and white-eyed insects appeared
in a ratio of 3 : 1, respectively. It was possible to consider this case as a Mendelian
characteristic unless his observation that all white- eyed insects were males.
Morgan explained that these genes are carried on the sex chromosome (X),
whereas the chromosome (Y) carries few genes only. He gave this case the name
sex-linked characteristics. Therefore, Morgan considered that the eye colour of
Drosophila insects is a sex-linked characteristic. Enrishment
Sex-linked characteristics in humans: There are some genes on
the chromosome (y) in the
In humans, the chromosome (X) carries the genes human male. There are no
that responsible for some body characteristics such corresponding genes on the
as: hemophilia, colour blindness, short-sightedness chromosome (x). therefore, the
and muscle atrophy. The father passes the genes of appearane of these traits, such
these traits to his daughters, but not to his sons. as the presence of hair on ear
margins, is restricted to males
Colour blindness: only.
The condition of colour blindness is caused by
a recessive gene carried on the chromosome (X). This gene causes the inability to
distinguish the colours especially the red and green ones.
The opposite genetic
Healthy mother Sick father
analysis shows the inheritance
of colour blindness trait:
P. XC XC X Xc Y
✍ Why is colour blindness
trait represented by a
single gene in males?
✍ What are the possibilities G. XC XC Xc Y
of this trait inheritance
among the male and
female offspring?
F1 XC Xc XC Y
✍ Why does not father pass
the colour blindness
Healthy male
trait to his sons? Healthy female (carrier)

The sex linked trait is

represented by a single gene Figure (30): The inheritance of colour blindness trait in human.
found only in males because
the chromosome (Y) does not
carry colour blindness genes, and is represented by one pair of genes in the females
due to the presence of a pair of sex chromosomes (XX)
• The male does not pass his trait to his sons because he passes the chromosome
(Y), not (X) to them.
• The male passes his trait to his grandsons through his daughters, while the
mother passes the trait to her sons and daughters.
84
 Test your eyes
Enrichment Look at the 2 following figures:
✍ What is the number in both the first and
The condition of muscle
atrophy is caused by
second circles?
a sex-linked lethal Your success in reading the numbers correctly
recessive gene carried indicates that you are healthy from colour blindness.
on (X) chromosome. This
condition is restricted only
to the males, not females.
It’s symptoms appear at
the age of twelve years.
This condition causes
a gradual atrophy of
muscles and healing is
not possible. It ends with
death.

Haemophilia:
Haemophilia is caused by a recessive gene carried on the chromosome (X). This
gene causes a case of blood liquidity due to the lack of some necessary substances
necessary for blood clotting. Haemophilia may cause death especially in the
childhood stage.

Sex-influenced traits
The genes of these traits are located on the autosomes, not on the sex
chromosomes. Sometimes, the sex of the living organism acts to modify the
dominancy of some traits, where the act
of these genes are influenced by the male Normal hair mother Bald headed father

or female sex hormones, such as the

presence of horns in cattels, baldness,and P. B+B
B+ B X
the shortness of human index finger.
G.
Baldness: B+ B B+ B
The opposite genetic analysis shows the
inheritance of hair falling trait: F1 B+ B
✍ What are the possibilities of appearance B+ B++ B+B
of hair falling trait among the members B B+B BB
of the resulted first generation? B+B+ Bald headed male and hair falling female.

✍ Is the ratio of hair falling trait B+B Bald headed male and normal hair female.
BB Normal hair male and female..
appearance is eqlual among the
two sexes? Why? Figure (31): Inheritance of baldness trait.

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 The baldness trait is attributed to the presence of a dominant gene responsible
for hair falling and affected only by the musculinity hormones. The phenotype of
the hybrid genetic structure is different in male from that of female. The baldness
appears in males in two cases: in the pure genotype (B+B+) and the hybrid genotype
(B+B) due to the effect of the musculinity hormones. While, the hair falling trait in
females appears only in the pure genotype (B+B+). The individuals with the genotype
(BB) in both sexes do not suffer from hair falling.

Genetic hair falling in Genetic baldness in males

females
Figure (32): The case of genetic baldness in humans

Sex-limited traits
There are some traits that are constricted to one sex only due to the differences
in sex hormones of each sex. These genes are responsible for the appearance of
some traits such as milk production which is limited to the females only, not males.
The females have cerain sex hormones help the gene to express its effect. Also, the
secondary sexual characteristics in humans such as the beard in men, and also the
ability of female birds to lay eggs.

Methods of studying human genetics

A-The pedigree:
Scientists are finding a difficulty in studying the inherited traits in humans due
to the long period of time between a generation and another, in addition to the
few number of offspring resulted from each marriage. Scientists try studying some
genetic patterns in humans by studying the pedigree or family tree of some families.
Pedigree is the genetic data in the form of a diagram illustrates the inheritance of a
specific trait in the family. It benefits in follow different genetic traits especially what
related with some deformities or genetic diseases.
It is also useful in prediction the possibility of appearance of these traits in the
future generations.

86
✲ Figure (33) shows a pedigree of a family.
I
• The male is represented by a square and the (1) (2)
female by a circle.
• The mirrage is represented by a horizontal line
II
cannecting between the square and the circle.
(1) (2) (3) (4)
• Giving birth is inicated by a vertical line
Figure (33): A pedigree
extending from the line of mirrage.
• Each generation is indicated by a Romon number, while each individual has
an Arabic number.
• The figures that carry the trait studied are coloured.
Be interconnected with activities and exercises book: Applied activity: Designing a pedigree
- Assessment activity

Studying some genetic cases in humans:

1 Albinism:
• Albinism can be resulted due to the absence of melanin
pigment from cells of skin epidermis, hair and eyelashes.
• The following pedigree shows the inheritance of albinism
which caused by a recessive gene (a).

I
(1) (2)
Figure (34): Albinism
II
(1) (2) (3) (4)
Figure (35): The pedigree of albinism

✍ Note that all expected possibilities of genotypes of this family are:

(I) 1- Aa 2- Aa

(II) 1- aa 2- AA or Aa 3- AA or Aa 4- AA or Aa

2 Polydactyly :
• Polydactyly (presencs of a sixth finger) is caused by a
dominant gene.

B- Studying of the genetic map:

Since a period of time, scientists ended from
developing a map for all human genes. By this map, it is
possible to predict the diseases which the humanes may
Figure (36): The sixth fingar
suffer from in the future.

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 C- Examination of the amniotic fluid during pregnancy:
The examination of chromosomes present in the embryonic cells obtained from
the amniotic fluid surrounding the fetus helps in diagnosis of the diseases resulting
from the increase or decrease the chromosomal number, such as Klinefelter's, Turner's
or Down's syndromes. It is possible to obtain photographs of these chromosomes
and make a karyotype for the fetus. Figure (37) illustrates how can some cells of the
amniotic fluid be obtained:

uterus

placenta

fetus

cells of the fetus

amniotic fluid

Figure (37) Getting the chromosomes from the fetal cells helps in making a karyotype for the fetus.

Medical examinations befor the marriage

Medical examination befor the marriage is a series of medical examinations
carried for the persons who will get married to be sure that they are free from the
infectious diseases such as hepatitis and AIDS, as well as genetic diseases such as
thalasemia.
These examinations are carried out to give the medical councel about the
possibility of transmission of these diseases to the partner or to the offspring in the
future. In addition, these examinations provide the choices or alternatives to who
will get married in planning for a healthy family.
The marriage of relatives and proceeding without making the medical
examinations are considered foctors of genetic diseases spreading out. Medical
examinations before marriage help in:
1 Giving birth healthy children.
2 Limiting the spreading out of gentic diseases, congenital deformifies and
mental retardation.
3 Avoiding the financial, psychic, social loads when caring the children infected
with genetic diseases.

88
 Science, Technology and Society

Genetic fingerprint
Genetic fingerprint did not know until 1984. When sir Alec
Jeffreys at university of leicester in London puplished a reseach
showed that the genetic material may repeat many times. After
one year, he stated that these repetitive sequences are unique and
chractedristic for each individual. They are imposible to be similar
in tow individuals unless in the identical twins only. Dr.Alec
recorded the patent of his discovery in 1985. He named these
repetitive sequences by the name the human DNA fingerprint.
This fingerprint was known as “a mean used to identify individuals
through compairing DNA sections (fragments)”. Sometims, it is
called “DNA typing”.
The usage of genetic fingerprint started in the medicine. It
was used in studying of genetic diseases, operations of tissues
implantation and others. It is fastly introduced into field of “forensic
medicine”, where it was used in identifying the deformed carpses
and tracing the missing children. Courts opened the files of crimes
registered against unknown persons, and the interrogations DNA carries the code of genetic
opened once again. The genetic fingerprint exempted hundreds fingerprint
persons from killing and ravishment crimes, and incriminate
others. It was the decisive word in the cases of ancestries.
Human genome
Human genome comprises all the genes found in the nucleus of each somatic
cell. Their number is ranging between 60,000 and 80,000 genes. They are located
on 23 pairs of chromosomes. The genes participate in presence of the enormous
number of human characteristics. The search for genes started in 1953 when the 2
scientists Watson and Crick proved that the gene is a double
helix of the nucleic acid DNA. In 1980, the idea of genome
appeared and the number of genes identified by scientists
was about 450 genes. At the middle of eighties, this number
is doubled three times over to reach 1500 genes. The aim of
scientists was the drawing of a good genetic map through
the accurate idenification of the locations of genes on the
chromosomes. So, the genes causing genetic diseases can
be indentified.
Now, scientists aim to benfit from the genome in the field
of drugs industry and reaching to drugs without side effects,
and studying the evolution of living organisms by comparing
human genome with other ones of the other living organisms.
Also, they aim to breed improvment through identifying the
Chromosomes carry thousands of genes.
genes of diseases in the fetus before its delivery and act to
improve them.

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 Key terms
• Linked genes: A group of different genes, carried on the same chromosome,
and inherited together.
• Chiasma: The points of contact of the internal chromatids of the homologous
pairs of chromosomes.
• Crossing over: The exchange of parts of internal chromatids between the pairs
of homologous chromosomes during meiosis.
• Lethal genes: The genes that lead to retardation of growth and cause death at
different stages of life when they are found in an identical form (pure).
• Antigens: Chemical substances found on the surface of red blood cells and
determine the transfused blood group.
• Pedigree: Genetic data displayed in the form of a diagram shows how a specific
trait is inherited, and it benefits in follow up the different traits.
• Karyotype: Classifying of chromosomes into homologous pairs arrnged
accoarding to their size.
• Lack of dominance: A genetic case in which the gene does not dominate over
the corresponding gene and they interact to produce a new trait.
• Sex-linked characteristics: Genes of these characteristics are carried on sex
chromosomes, and their appearance does not affected by sex hormones.
• Sex- influenced characteristics: Genes of these characteristics are carried on
autosomes and their appearance is affected by sex hormones.
• Klinefelter's syndrome: An abnormal case resulted due to the presence of an
extra (X) chromosome in some males (XXY).
• Turner's syndrome: An abnormal case resulted due to lack of one (X)
chromosome in some famales (XO)
• Down's syndrome: An abnormal case resulted due to persence of an extra
autosome in the pair of chromosomes number (21).
• Rhesus factor: A type of antigens found on the surface of red blood cells in most
humans. Three pairs of antigens located on the one chromosome pair control the
production of rhesus antigens.

90
 Traits inheritance

Afected by

Environmental factors Abnormal cases Genes interaction

include
Down's Turner's Kline-
syndrome syndrome felter's Comple- Lack of
Sex characters Lethal Multiple
syndrome genes mentary dominance
allels
include genes
are
include
example example
Sex- Sex-in- Sex- Recessive Dominant example
limited fluenced linked
example example

Flower Blood Flower

Absence of
Concept map of Unit three

Yellow
Milk secretion Baldness in colour colour groups colour
chlorophlyl in fur
in female man blindness in in pea character in

Biolo
plants colour

g
Oxygen Temperature Light mammals humans flower Antirrhinum
in mice
plants plants

y-U
Affect on

nit
3
Chlorophyll
character

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 Unit Four

Classification of living organisms

No one knows how many several kinds of living organisms on Earth’s surface.
In spite of human success in describing and naming about 1.4 million kinds of these
types till now, biologists are thinking that this number is not representing more than
10% only of the living organisms on Earth’s surface. There are millions of insects,
small animals and plants that live in oceans which are not yet discovered till now.
Due to the massive diversity in living creatures, the need to the classification
process appeared. Scientists classify the living organisms according to their common
features in order to make it easier to be studied. In this unit, we are going to know
the principles that biologists apply in classifying the living organisms and what are
the main groups of living creatures in the light of the modern classification. You will
acquire the skill of classifying living organisms according to their characteristics.

net.
For mo n the
r e inform
ation about ani s ms, log i
the topic of classiffying living org
 Time management
To achieve the maximum benefit of this unit, you need to:
• Manage your time between the practical and theoretical study, searching and
extending information resources.
• Carefully, record the results of your practical study which is the best way to support
your learning.

Learning outcomes
By the end of this unit you should be able to:

• Define what is meant by species. • Classify some living organism according to the modern
• Describe the way of binomial nomenclature of living classification.
organisms and give examples. • Appreciate the grandeur of Allah in creating different
• Explain some attempts of classifying living organisms. types of living organisms.
• Design dicotomous keys. • Appreciate scientists efforts in classifying living
• Explain modern classification system. organisms and identifying them.
• Explain the featured characteristics of the five kingdoms, • Follow the scientic method in solving problems.
phyla and classes. • Form a positive trend toward the protection of
• Give examples of kingdomes, phyla and classes. biodiversity.

tion.
iples of
Ch sms.

C alia.
er 3
Unit Four
Chapter 1

Principles of classification of living

organisms

By the end of this chapter, you

should be able to: Most of libraries contain thousands of books in
• Conclude some of the classification different fields. When you visit any of these libraries
benefits and importance.
• Define what is meant by species. to read a specified book, how can you find the book
• Describe the way of binomial that you are searching for between these enormous
nomenclature of living organisms
numbers of books? Libraries follow a specified system
and give examples.
• Numerate the levels of taxonomic to classify books and categorize them according to their
hierarchy of living organisms. fields, and in each field it divides into small categories
• Use and design the dichotomous key.
• Appreciate scientists efforts in
with specified subjects and so on till they use numbers
classifying and identifying living to place book on shelves.
organisms.
By this system it can be easy to find a specific book
in the library. We use classification system in our daily
life, in addition to books. We classify food, machines
and even television programs. Also, scientists use
a system to classify living organisms, but how can
scientists classify this huge numbers of several kinds of
living organisms on Earth’s surface?

key terms Importance of classification

Although living organisms may be similar in their
• Kingdom
• Phylum building and functional unit (the cell), as well as in
• Class the seven life features (nutrition, excretion, respiration,
• Order
• Family
movement, growth, reproduction and sensation), but
• Genus they differ in many other characteristics, as : form,
• Species structure, way of living, nutrition and reproduction.
• Binomial nomenclature system
• Dichotomous key
Due to the enormous diversity in the living organisms,
• Taxonomic hierarchy the need to classification process appeared to facilitate
studying these organisms. Classification is defined as
the arranging of living organisms in groups according
to similarities and differences between each other to
make it easier to be studied and identified. The science
field which concerns with classification of living
organisms in groups is called taxonomy.

94
 The classification of living organisms on scientific bases make it easier to identify
new organisms, and to add them into their similar groups. Also, classification
benefits many other fields of science.
The philosopher Aristotle (more than 2300 years ago) is considered as the first
who classified animals into red blooded animals and bloodless animals. Also , he
classified plants into trees, shrubs and weeds.
The modern classification depended on the definition of the species as a
scientific and basic principle in the classification of living organisms.
✲ What is meant by the species?
Tigon:
When mating takes place between a lion
female and a tiger male, the tigon is produced
(fig. 1). Tigons are sterile as they are unable
to mate and reproduce:
Mule Figure (1): Tigon
Mule is produced by mating of a male
donkey and a female horse. Mule is sterile
and unable to mate and produce of new
generation.
The term species does not given to tigon
or mule because they are unable to mate and
produce a new generation of the same kind.
✲ The species: is a group of individuals having
similar morphological characteristics, mate Figure (2): Mule
with each other and produce fertile offspring
similar to them.

Naming of living organisms

There are often different names for the same organism in the various Earth’s
regions and environments. These names are called the common names.

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 To overcome this problem, Linnaeus proposed a system
for nomenclature of living organisms called the binomial
system of nomenclature written by latin language. In this
system, each organism was given a binomial name. The
first name represents the genus (begins with a capital letter),
while the second name represent the species (begins with
a small letter). It was agreed to write these names by tilted
Felis domesticus
latin letters, or to underline each of them by a special line
to make it different than others. For example, the scientific Genus Species

name of cat is Felis domesticus. Felis = ‫ﻗﻄﺔ ﺑﺎﻟﻠﻐﺔ ﺍﻟﻼﺗﻴﻨﻴﺔ‬

domesticus = ‫ﺍﳌﻨﺰﻟﻴﺔ ﺑﺎﻟﻠﻐﺔ ﺍﻟﻼﺗﻴﻨﻴﺔ‬
Enrichment: Figure (3): The scientific name
Latin language was used to be a scientific language because of the domestic cat
its words has brief meanings.
In addition, it is an old language and not spoken by people.
This protects this language from any change or modification.

Taxonomic hierarchy
There are 7 groups or levels for classifying living organisms. Each group
comprises less numbers of organisms, that
have more similar characteristics than, that
of the group preceeding it. These groups
are: Kingdom :
Animalia

1 Kingdom:
• Includes a number of phyla.
Phylum:

2 Phylum: Chordata

• Includes a number of classes.

Class:
3 Class: Mammalia
• Includes a number of orders.
Order: Carnivora
4 Order:
• Includes a number of families. Family: Felidae

5 Family:
• Includes a number of genera. Genuns: Felis

6 Genus: Species: domesticus

• Includes a number of species.

Figure (4):Classification of domestic cat

96
 7 Species:
• Species is an interbreeding population of organisms that can produce healthy,
fertile offspring.
• In addition to the previously mentioned groups, there are other groups that
intermediate each two successive groups, such as sub - phylum, and sub - class.

Dichotomous key
✍ What will you do to Know the species of a living organism you founded
accidently?
You may be try to find it’s picture in a book, but this way sometimes is not
efficient, may be this organism have different colour from the picture, or even is not
existing in the book.
Scientists often use the dichotomous key to help them in identifying living
oranisms. Dichotomous key is a series of descriptions ordered in pairs, that leads
to identify an unknoun living oramism. Dichotomous key is designed to start with
broad features, then it get more specified and more privacy whenever we go through
the levels of dichotmous key. Through each step, you can choose one of the two
descriptions according to the characteristics of the living organism. By the end, you
will reach to a description leads you into the organism’s name or the group which
it is belonging to.

Wingless
Ant

Legs are
Shorter than
Insects the body
fly
One pair
Legs are longer
of wings than the bocly
Mosquito
winged
Wings covered
by bright scales
Two pair Moth

of wings
Wings are
transparent

Dragonfly

Figure (5): A bilateral dichotomous key for 5 species of insects

Be interconnected with the activities and exercises book: Applied activity: Designing
a dichotomous key.

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Unit Four
Chapter 2

Modern classification of living organisms

By the end of this chapter, you

should be able to: In 1700, Carolus Linnaeus established the
• Explain some attempts to classify traditional classification system that classified living
living organisms.
• Explain the modern system of organisms in two kingdoms only: Animal kingdom and
classification. Plant kingdom.
• Identify the main characteristics of
viruses. By the technological advances used in field of
• Explain the characteristic features biology and increasing of knowledge , the scientist
of the five kingdoms of living
organisms. Robert H. Whittaker (1969) established a new system
• Mention examples of living organisms of living organisms classification called the modern
belonging to the Monera, Protista ,
system of classification. In this system, living organisms
Fungi and Plantae kingdoms.
• Classify some living organisms in the were classified into five lingdoms: Monera, Protista,
light of modern classification. Fugi, Plantae and Animalia . It is the conventional
• Appreciate scientists efforts in
identifying and classifying living
system in the scientific communities. There are some
organisms. organisms that are difficult to classify according to
• Appreciate the grandeur of Allah in Whittaker classification. They include the viruses,
creation the various living organisms.
viroids and prions.

(1) Kingdom Monera

key terms
• Monera Kingdom Monera is charaterized by the following
• Protista characters:
• Fungi
• Plantae • Unicellular organisms.
• Animalia
• Non-vascular plants • It may live individually or in colonies.
• Vascular plants
• Ferns • Cell wall is devoid from cellulose or pectin.
• Gymnospermae
• Angiospermae
• Many cytoplasmic membranous organelles such
as: mitochondria, Golyi apparatus, endoplamic
reticulum and plastides are lack.
• It does not contain a definit nucleus , where its
genetic matarial is not externally surrounded with
a nuclear membrane.

98
 Monerans are classified into two different groups: Enrichment
Nanobacteria: They are very
1 Archaebacteria:
tiny bacteria. Their size is about
Most of them are often survive in harsh 20-200 nanometers. Scientits
environmental conditions, such as : hot springs, disagree in considering them
environments with no oxygen, and in highly salty as crystalline structures or a
water. This group differs from true becteria in the new form of life. These bacteria
grow slowly inside living cells
structure of both cell membrane and cell wall.
and their shape change during
their stages of growth. They are
2 Eubacteria: more resistant than the normal
This group includes many widely spread species. bacteria. They can protect
themselves from the defense
They exist everywhere, in air, on land and in water. systems of the body by secreting
Some of them are autotrophic such as cyanabacteria stony shields surrounding them
as Nostoc (fig.6) while others are heterotrophic. as a capsule . Researchers reach
Bacteria reproduce asexually by binary fission. that this kind of bacteria is a
They have various forms where their shape may be main cause in the formation of
kidney stones, atherosclerosis
spherical , rod - shaped or spiral (fig.7)
and inflammation of the prostate.

Spiral - shaped bacteria. Rod-shaped bacteria Spherical shaped bacteria.

Figure (6): Nostoc Figure (7): Various forms of bacteria.

Be interconnected with the activities and excercises book: Practical activity: Shapes and characteristics
of bacteria.

(2) Kingdom: Protista

These organisms are eukaryotic. They differ of both plants and animals, where
their structere is not complex. Some of them have a cell wall and plastids.
Protists are classified into several phyla, the most important ones are:

1 Phylum: Protozoa:
They are unicellular microscopic animal-like organisms, live in fresh and salty
water, as well as in moist soils ; they may live individually (solitary) or in colonies;
some are free living and others parasitize plants and animals, causing diseases; they
reproduce both sexually and asexually.
Protozoa is classified into four classes depending on the mean of locomotion:

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 Class : Sarcodina
They move by Temporary extensions from the body called pseudopodia , e.g.
Amoeba (Fig 8).

Class : Ciliophora
They move by cilia surrounding the body , e.g. Paramecium (Fig 9)
Cytoplasm Contractile vacuole

Oral groove
contractile
vacuole Cilia

Nucleus

Micronucleus
pseudopodia

Macronucless
Figure (8): Amoeba Figure (9): Paramecium

Class : Flgellata
They move by flagella , e.g. Trypanosoma (Fig.10) ‫ﺳﻮﻁ‬

which parasitize humans and causes sleeping sickness.

Figure (10): Trypamosoma

Class : Sporozoa
They have no mean for locomotion. They
Enrichment
produce phases called spores , e.g Plasmodium
which parasitizes human and infect him with malaria Sleeping sickness: This is one
disease. of widespread diseases of the
tropical regions. This disease
in transmitted by tsetse fly
2 Phylum : Euglenophyta which transfers Trypansoma
This phylum comprises Euglena . They are parasite by biting humans.
unicellular living organisms contain green plastids The infected person suffers
and do photosynthesis . They move by flagella. from fever, heavy sweat,
headache , tendency to sleep,
hallucination and weakness.
Eye spot Without treatment in proper
Nucleus
time, the patient goes into
coma which leads to death.

Chloroplastids

Flagellum

Figure (11): Euglena

100
 3 Phylum : Chrysophyta
Most of them are unicellular algae called diatoms. Diatoms have glass-like cell
walls containing silica. Diatoms are considered as an important source of food for
fish and other marine animals.
Enrichment
4 Phylum : Pyrrophyta Red tide: Red tide is a natural
phenomenon occurs in seas
These algae form a great portion of phytoplanktons and oceans water, where
live in seas and oceans. They acquire a red colour water is coloured red. This
because they contain a red pigment beside the is accompanied with death
chlorophyll pigment. Dinoflagellates represent the of thousands of fishes. This
largest group in this phylum. Its members move by phenomenon is attributed
two flagellae. to the enormous increase in
numbers of dinoflagellates.
When water becomes warm
with plenty of nutrients,
these organisms repreduce
very rapidly and secrete
toxins kill fishes.

Figure (11): Diatoms Figure (12): Dinoflagellates

(3) Kingdom: Fungi

Fungi are characterized by the following characters:
• Fungi are heterotrophic organisms, some are unicellular, and the most are
multicellular.
• They are immobile and have cell walls contain legnin.
• They are consisted of filaments called hyphae, and collected together to form
mycelium.
• They are heterotrophic, some are parasites and others are saprophytes.
• Most of them reproduce sexually, as well as they reproduce asexually by
producing spores.

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 Fungi are classified depending on their structure and ways of reproduction into
live divisions , the most important ones are:

The hyphae are not divided,

spores are produced inside
sporangia. Example:
Rhizopus nigricans (bread Sporangium
Division :
mould) which causes the
Zygomycota black putrefaction on
Sporangiophore
bread. An enzyme used in
Mycelium
cheese industry is extracted
from this fungus. Rhizoids

Figure (13): Bread mould fungus

Some are unicellular such Penicillium fungus

as yeast fungus , and others

are multicellular with
hyphae divided by septa .
Division :
They produce spores inside
Ascomycota sac-like structures called
asci. Example : Penicillium
fungus which produces the
antibiotic penicillin.
Yeast fungus

Figure (14): Examples of Ascomycota

Cap

Gills

Their hyphae are divided

by septa. Their spores are
Division :
produced inside a club-shaped
Basidiomycota structure called basidium. Stalk
Mycelium
Example : mushroom

Figure (15): Mushroom fugus

102
 (4) Kingdom: Plantae
Plants are eukaryotic organisms, characterized by cellulose walls. Plant cells
contain the chlorophyll substance in structures called chloroplastids. Most plants
repreduce sexually.
Scientists classify plant kingdom into:
a- Higher algae : they include the red , brown, and green algae.
b- Non - vascular plants : include bryophytes (mosses)
c- Vascular plants.

1 Phylum : Rhodophyta
They are marine weeds sticking together
by a gelatenous coat. The cells of these algae
contain chromatophores of red pigments.
Example : Polysiphonia (fig.16).

2 Phylum : Phaeophyta Figure (16): Polysiphonia

They are marine weeds consist of simple or branched filaments . There are
chromatophores of brown pigments in their cells.
Example : Fucus (fig.17).

3 Phylum : Chlorophyta
These algae contain chloroplastids. Some are
unicellular such as Chlamydomonas (fig.18) and
others are multicellular such as Spirogyra (fig.19) Figure (17): Fucus

which has the form of unbranched filaments and its

cells contain sprial - shaped chloroplastids.

Figure (18): Chlamydomonas Figure (19): Spirogyra

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 4 Phylum: Bryophyta (Mosses):
This phylum includes the plants which do not contain speciallized vascular
tissues, so they are called non-vascular plants. They are terrestrial plants that need
dampness greatly to grow and reproduce. Therefore, they live in damp soils and
shaded places. They are small, green in colour, and have certain hairs for anchorage
which are rhizoids. Some are flat such as Riccia and others are erect such as Funaria
(fig. 20).

Riccia Funaria

Figure (20): Bryophyte plants

5 Phylum: Tracheophyta:
This phylum comprises the plants which have speciallized vascular tissues
for transport of water and minerals (through the xylem) and transport of organic
substances produced by photosynthesis (throuhg phloem), so they are called
vascular plants. This phylum is classified into three classes:

Class: Filicatae (Ferns).

These plants have simple structure. Most of them are
herbs and few are shrubs or trees. They live in shaded
damp regions, as well as the wall of wells and shaded
damp valleys. They have stems, leaves and roots. Also,
they carry pinnate leaves and do not produce flowers
or seeds. They reproduce by the spores that found in
special structures on the lower surface of leaves. Example: Figure (21): A pinnate
Polypodium (fig. 21), and Adiantum. leaf of Polypodium

Be interconnected with the activities and exercises book: Practical activity: Examination of Ferns.

Class: Gymnospermae or Conifers:

Most of them are trees and few are shrubs. They do
not produce flowers. Thy carry male and female cones.
They have naked seeds and needle - shaped simple leaves.
Example: Pinus (fig. 22).

Figure (22): Pinus plant

104
 Class: Angiospermae or Flowering plants:
Be interconnected with the activities and exercises book:Practical activity: Examining flowering plants.

They are terrestrial plants; have stems, leaves and roots; they produce flowers
that convert into fruits enclosing seeds. These plants are classified into two groups:
Monocotyledons and dicotyledons.
Use the following table that help you to identify the differences between the
two major groups of flowering plants.
✲ Table (1): The taxonomic characteristics of monocotyledons and dicotyledons:

Seeds Leaves Flowers Stem Root

Root- monocotyledons

Dicotyledons

Monocotyledons Dicotyledons
• The seed has only one cotyledon. • The seed has two cotyledons.
• Bundles of vascular tissues are • Bundles of vascular tissues are
scattered inside the stem. arranged in a ring.
• Flowers with trimerous whorls or • Flowers are either tatramerous or
their multiples. pentamerous.
• Leaves are narrow and parallel • Leaves are of pinnate or palmate
viend. venation.
• They have fibrous roots. • They have tap roots.
• Examples: wheat, onion and palm. • Examples: peas, Beans and cotton.

(5) Kingdom Animalia

They are multicellular, eukaryotic organisms. They have the ability of moving and
transporting from a place to another. They have the ability for responding rapidly to
external stimuli in the surrounding environment. Their majority reproduce sexually.
• This kingdom will be studied in detail in chapter 3.

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Unit Four
Chapter 3

Kingdom Animalia

By the end of this chapter, you

should be able to: Scientists classify kingdom Animalia into nine phyla
• Identify the characteristic features of depending upon the degree of the body complexity.
the major animals phyla.
• Give examples of living organisms Some phyla are without vertebral column and called
belonging to animals. invertebrates, while others have a vertebral column
• Classify some living organisms in
inside their bodies and called vertebrates.
light of the modern classification.
• Form a positive trend towards the
maintaining of biodiversity. 1 Phylum: Porifera (Sponges)
• Appreciate the grandeur of Allah
in creation of the various living • Sponges are simple
organisms. structured, immobile,
aquatic animals. They
live attached to rocks.
Most of them live in
seas and oceans, and
the few in fresh water.
• Their bodies have
various shapes where
it may be tubular or
key terms vase-shaped. Figure (24): The sponge

• Porifera
• Cnidaria
• The body is hollow and its wall has many pores
• Platyhelminthes and canals. Soponges are known as porifers. The
• Nematoda body opens to the outside at its top by a large
• Annelida
• Arthropoda opening called osculum.
• Mollusca
• Echinodermata
• They live individually (solitary) or in colonies and
• Chordata their bodies are asymmetric.
• Body wall in supported with a skeleton of spicules,
fibers or of both.
• Most sponges are hermaphrodites, reproduce
sexually by gametes and asexually by budding
and regeneration.
• Example: Sponge (Fig.24)

106
 ✍ Sponges are classified as animals although they are immobile, because
they are multicellular, heterotophic, have no cell walls, and comprise
few speciallized cells.

2 Phylam: Cnidaria:
• They are aquatic animals; the most are marine, and live individually or in
colonies.
• They have no head, and the mouth is surrounded by appendages and extensions
called tentacles.
• Body cells are arranged in two tissue layers, the external one contains cnidocytes
(stinging cells) for defence and capturing of preys (fig. 25). There are a plenty
of these cells on tentacles.

Cnidocyte

Filament

Spicules
Prey

Nuclei

Tentacles

Hydra

Figure (25): Using of cnidocytes in capturing the preys

During life cycle, the majority of these animals exhibit two body forms: the
polyps (feeding individuals) which perform all life functions except reproduction,
and the medusae which are the individuals responsible for sexual reproduction. The
medusae are often free swimming (fig.26).
Tentecles

Gastro vascular cavity

Tentecles

Medusa Polyp

Figure (26): The polyp and medusa in the cnidarian life cycle

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 • In some cnidarians, the polyps only appear in their life, and in others the
medusae dominate over their life, while some others include these two forms.
✲ Phylum Cnidaria is calssified into 3 classes:

Class: Hydrozoa
Polyps dominate over their life cycle; the majority are marine and live in
colonies, and the few are solitary and live in fresh water such as Hydra (fig. 27).

Class: Scyphozoa
These animals spend the most of their life cycle in the medusa form. They are
marine animals live in seas and oceans, such as Aurelia (fig.28).

Class: Anthozoa
They have no medusa. They are flower-like animals. All of them are marine,
such as sea anemone and Alcyonium (fig.29).

Figure (27): Hydra Figure (28): Aurelia Figure (29): Sea anemone

• For more information about coral reefs, search at the speciallized internet sites.

3 Phylum: Platyhelminthes (Flat worms).

Figure (30) illustrates a group of flat worms. Observe these worms, and infer
their common features.
✍ Why are these worms called flat worms?

Planaria Bilharzia Tape worm

Figure (30): Different types of flat worms

108
✲ Flat worms are charaterized by the following characters:
• The bodies of these worms are flatened and have a head.
• Their bodies are composed of 3 layers (triploblastic) and bilaterally symmetrical.
• The majority are free living.
• The majority are hermaphrodites.
✲ This phylem is classified into 3 classes:

Class: Turbellaria
Free living worms, their majority live in fresh water. Their length is few
centimeters, such as Planaria.

Class: Trematoda
These worms parasitize humans and animals, and cause serious diseases, such
as Bilharzia worms.

Class: Cestoda
These worms are parasitic flat worms, live inside the intestines of humans and
animals.
They cause intestinal disturbances, anaemia, weakness and slimness. Their body
is long, ribbon - like and may reach several meters in length, such as: Tape worms.

4 Phylum: Nematoda (Round worms)

Round worms are characterized by the following characters.
• The body is cylindrical, tapers at its two ends and unsegmented. Their sizes are
ranging from the microscopic to what may reach 1 meter.
• Their bodies consists of 3 layers and bilaterally symmetrical.
• They have alimentary canal with two openings, the
mouth and anus.
• The sexes are separate (unisexual).
• They live in all environments; some are free-living in
water or mud and others parasitize humans, animals
and plants.
Examples: Ascaris and Flaria worms
Figure (31): Ascaris

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 Enrichment
Elephantiasis: This disease in caused by a nematode worm called
Flaria exists in the tropical regions of Asia continent. These worms live
inside human blood and lymph vessels. This disease is transmitted by
the biting insects, mainly mosquitoes. In cases of heavy infections,
the worms may become so numerous that obstruct the flow of fluids
through lymph vessels, causing swelling of the infected body parts as
shown in the opposite figure.

5 Phylum: Annelida (Ring or segmented worms):

Earth worms which live inside burrows in the soil
represent common examples of segmented worms.
This group of worms are characterized by the following
characteristics:
• The majority are free-living in the sea, fresh water
or the moist muddy soils. Few of these worms are
external parasites.
• The body is divided into rings (or segments), and Figure (32): Earth worm
many of them have chaetae (spine-like) buried in the
skin and help them to move.
Search and expand
• Some of them are unisexual and the few are
hermaphrodites The worm illustrated in the
figure is one of annelids (ring worms)
Be interconnected with the activities and exercises called the leech.
book: Practical activity: Examination Earth worms. Use the internet
or reference
books to search
6 Phylam: Arthropoda the importance
This phylum is characterized by the following of these worms.
characteristics:
• The body is bilaterally symmetrical and divided into a number of segments
carry many pairs of appendages. Each appendage consists of many jointed
pieces.
• The segmented body is divided into
many regions covered by an exoskeleton.
This phylum comprises four classes:

Class: Crustacea
The body consists of two regions
(cephalothorax and abdomen) and
Prawn Crab
covered with a chitinous cuticle. They
have many jointed appendages adapted Figure (33): Examples of crustaceans

110
in different forms to perform various functions. The eyes are compound. They
breathe by means of gills. Examples: prawn, crabs and lobster (fig. 33)

Class: Arachnida
The body consists of two regions
(cephalothorax and abdomen). They
have four pairs of walking lesgs
and breathe by Tracheoles or lung
books. Their eyes are simple. They
are unisexual. Examples: Spiders and
scorpions (fig. 34). Scorpion Spider
Figure (34): Examples of arachnids
Class: Insecta
The body is divided into head, Enrichment
thorax and abdomen. They have one pair Simple and compound eyes
of antennae, a pair of compound eyes, 3
Simple eyes are found in fishes, brids and
pairs of walking legs and 2 pairs of wings mammals inclecling human. The simple
which may be absent as in the majority eye consists of one lens. While, compound
of ant species or reduced into one eyes existim insects and crustaceans. The
pair as in house flies. They breathe by compound eye consists of a group of visal
Tracheoles. Examples: flies, mosquitoes, units (close minute lenses) which differ in
cockroaches, ants, bees, moths and number, and the area and shape of their
external surfaces depencling on the species.
locusts (fig. 35).

Hous fly Honey bee Locust Dragonfly

Figure (35): Exampes of insects

Class: Myriapoda
The body is distinguished into a head and a trunk
composed of several segments. They have many walking
legs. They respire by tracheae. Example: Scolopendra
(fig.36).

Figure (36): Scolopendra

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 7 Phylum: Mollusca
This phylum is chracterized by the following characteristics:
• Their majority live in salt water, some in fresh water and a few on land.
• The body is a soft mass, unsegmented and has a mascular part used in
locomotion called the foot.
• They have a calcareous shell which may be external or internal, absent or
reduced.
• The head is present and well developed (carries sense organs) and may be
absent in some of them.
• The majority of molluscs have an organ similar to the tongue called the radulla
used in feeding.
• Most of them are unisexual, and the few are hermaphrodites.
Molluscs are classified into several classes, the most important ones are:

Class: Gastropoda
They are the molluscs that slides along the foot located under their bodies. The
majority have a spiral shell consisted of one piece. Some live in water and breathe
by gills and others live on land and breathe by a simple lung. Examples: Snails and
slugs.

Class: Bivalva
These molluscs have a shell consisting of two jointed peices. All members of
this class are aquatic and breathe by gills. Examples: Oysters and mussels.

Class: Cephalopoda
A part of the food modifies into several tentacles located in the head and away
from the rest of the body. Examples: Octopus and Sepia.

Snail Oyster Octopus

Figure (37): Examples of molluscs

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 8 Phylum: Echinodermata
This phylum is characterized by the following chracteristics:
• The body is unsegmented, and has a hard endoskeleton. Some have spines and
calcareous plates in body wall.
• They have sucker - like structures called tube-feet.
• The body may be rounded, cylindrical or star-shaped. Some have arms.
• They move by tube feet, spines or arms.
• They are unisexual, reproduce asexually by regeneration and sexually by
gametes.
• They have no anterior or posterior end. The bodies of echinoderms majority
has two surfaces. The surface in which the mouth is located is called the oral
surface and the opposite sufface in called the aboral surface.
Echinoderms are classified into several classes, the most important ones are:

Class: Asteroidea
They have five arms or more extend radially from a central disc, such as sea star.

Class: Echinoidea
These animals have no arms. Their bodies are covered with spines for protection
and locomotion. They have beak-shaped five sharp teeth for fragmenting and
chewing food, such as sea urchin

Class: Holothuroidea
These animals have long soft bodies whith no arms. Their endoskeleton is
reduced. Example: sea cucumber.

Sea star Sea urchin Sea cucumber

Figure (38): Examples of echinoderms

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 9 Phylum : Chordata Do you know?
This phylum includes the most higher animals Vertebrates and thermal
of animal kingdom. The embryos of animals of equilibrium
this phylum are charaterized by presence of a Body temperature of some
skeletal structure located at the dorsal region and vertebrates such as birds and
called the notochord. The notochord either persists mammals does not change more
throughout the whole life or be converted into a with the change of environment
vertebral column in the majority of chordates. temperature. Therefore, they are
called endothermies or warm
This phylum is classified into several subphyla, blooded animals. They use the
the most important one is subphylum Vertebrata. energy of food to keep their
body temperature constant.
Sub- phylum: Vertebrata Fishes, amphibians and reptiles
are belonging to the variable
Notochord first appears in vertebrates in the
temperature animals, where
embryonic stage. It becomes gradually replaced they can`t regulate their body
by the vertebral column as the embryo develops. temperature which change
Vertebral column surrounds and protects the spinal according to the change in the
cord. Vertebrates also have an endoskeleton. It surrounding environment. They
consists of the vertebral column, skull, girdles and derive their temperature from
limbs, in addition to presence of a heart formed of this environment. Therefore, they
are called ectotherms or cold
many chambers and the blood flows inside blood
blooded animals.
vessels in a closed circulation to feed all body
organs with oxygen and nutrients.
✲ Vertebrates are classified into several classes:

Class: Agnatha
• They are jawless fishes with a circular
mouth similar to the funnel and provided
with many horny teeth.
• They have a thin , long and eel - like
body with no paired fins. Their skeleton is
cartilagenous.
Figure (39): Lamprey
• They are parasites. They stick by their mouth
into the big fishes. They attach themselves by the teeth and snap the flesh of
these fishes by their rough tongue which is similar to the rasp.
Example: Lamprey (fig. 39).

Class: Chondrichthyes
• They are marine fishes. The endoskeleton is cartilagenous.
• The mouth lies on the ventral surface and provided with several rows of teeth
that help them in predation.

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• They have paired fins and the body is covered with certain scales similar to
the teeth.
• They have no air bladder for floating. Their gill slits are not covered by an
operculum. The sexes are separate and fertilization is internal.
Examples: Shark and Ray fish (fig 40)

Shark Ray

Figure (40): Examples of cartilagenous fishes

Class: Osteichthyes
• These fishes live in salt or fresh water
• Its endoskeleton is bony. Their mouth is terminal. The body has paired and
medial fins. There is an air bladder inside the body helping in swimming and
floating.
• The body is covered with bony scales. Their gill slits are covered with an
operculum.
• The sexes are separate and fertilization is external.
Examples: Bolti and Bouri. (fig. 41)

Bouri Bolti
Figure (41): Examples of bony fishes
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Class : Amphibia
Frogs croaking: If you live
• They are cold - blooded animals. near agricultural fields,
• They have two pairs of pentadactyl limbs. The body perhaps you have heard the
croaking of frogs. This voice
is covered with smooth slimy skin.
comes from male frogs during
• The sexes are separate. Fertilization is external. They mating season for attracting
lay their eggs in water and the embryonic stages the females for mating. The
live in water and breathe by gills while adults are male can produce this voice
because it has a special
spent on land and breathe atmospheric air by lungs
structure called voice sac
and skin. which is absent in females.
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 Examples: frog and salamonder (fig.
g 42)

Salamander Frog

Figure (42): Kinds of amphibians

Class: Reptilia
• These animals are cold - blooded.
• The body consists of four regions: head, neck, trunk and tail. They have four
weak pentadactyl limbs. Each finger ends with a horny claw. The limbs may be
absent, so they move by creeping.
• The skin is dry and is covered with thick horny scales, which may be supported
by horny plates.
• They breathe atmospheric air by lungs.
• Sexes are separate. Fertilization is internal and they lay eggs with calcareous
or skiny shell.
Examples:
p Lizards, chameleon,, gecko,
g , tortoise,, snake,, and crocodile. (fig.
g 43)

Chameleon Lizard Crocodile

Figure (43): Kinds of reptiles

Be interconnected with the activities and exercises book: Practical activity: Comparing reptiles
and amphibians..

Class: Aves
• These animals are warm - blooded.
• The bodies are covered with feathers. They have four limbs, the anterior
ones are modified into wings for flying. Each one of hind limbs has four
digits provided with horny claws. The hind limbs help in movement on land,
climbing, swimming, diving or predation.
• Bones are hollow and light. The sternum is broad for attachment of the strong
thoracic muscles which move the wings during flying.
• They breathe by means of lungs. Their bodies contain air sacs act as stores for
additional amounts of air during flying.

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• The sexes are separate. Firtilization is internal, and they lay eggs and incubate them.
Examples: Pigeons, hens, ducks, hawks, eagles, sparrows
p and ostrich. (fig. 44)

sparrow Hawk Ostrich

Figure (44): Different types of birds

Class: Mammalia
• These animals are warm - blooded.
• The body is distinguished into head, neck, thorax, and abdomen. The skin is
covered with hair.
• They have four pentadactyl limbs provided with nails, claws, hooves or pads.
• They are characterized by presence of dissimilar teeth (incisors, canines and
molars).
• The sexes are separate. Fertilization is internal. The majority of them are
viviparous. The female has mammary glands which secrete milk to suckle her
youngs.
• They breathe by means of lungs.
✲ Class Mamalia is classified into three sub-classes:

Prototheria Metatheria Eutheria

These mammals do not give
birth, but they lay eggs and These animals give birth
incubate them. The eggs hatch immature young, therefore the All these animals are placental
youngs suckle milk secreted mother has to keep it a special mammals. They give birth
by mammary glands on the pouch at the bottom of her to fulley developed youngs
abdomen of the mother. They abdomen. The young feeds by feeding on milk secreted from
have a cloacal opening, through suckling milk from nipples inside the mother`s mammary glands.
which urine, faeces and eggs this pouch.
emerge.
Examples: Duck-billed Platypus Eutheria inclucle many of the
Eample: Kangaroo
and spiny ant - eater. animals that are headed by human.

Figure (45): Duck - billed Platypus Figure (46): Kangaroo

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 ✲ Sub-class Eutheria in classified into many oders, from which:
Order Characteristics Examples

• Some are without teeth,

while the others lost their
Armadillo and
Edentata front teeth only.
Sloth
• They have strong, curved
claws. Armadillo

• They feed on insects and their

front teeth extend outwards
Insectivora Hedgehog
like pincers for capturing of
the prey. Hedgehog

• They have large pointed

canines.
Lion, Tiger,
• The premolars are sharp,
Wolf, Fox,
Carnivora whereas the molars are broad
Dog, Cat and
and grinding.
Seal
• They have strong, sharp Tiger
curved claws.
• They are herbivore animals.
• They are odd-toed Horse,
(1-3). Each toe has a horny Donkey,
Perissodactyla
hoof. Their teeth are big- Zebra and
sized and adapted to grind Rhinoceros Zebra
food.

• These animals are herbivores.

Sheep, Goats,
• They are even - toed. Each
Artiodactyla Giraffe, Deer
toe is coated with a horny
and Camels
hoof.
Giraffe
• They are huge aquatic
animals live in seas and
oceans.
• The forelimbs are modified
to become paddle - like
for swimming and the hind Whale and
Cetacea limbs are absent. Dolphin
• They breathe atmosphric air
Whale
by lungs.
• Sexes are separate. They give
birth and suckle their youngs.
• Tail fin is horizontal.

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 • They have sharp chisel-
Rat, Gerbo.
shaped incisors.
Rodentia Mouse &
• The tail is long and ears are
Squirel
small. Rat

• The tail is short and ears are

long.
Lagomorpha • They have one pair of incisors Rabbit
in the upper jaw and two
pairs in the lower jaw. Rabbit

• The forelimbs are modified

into wings where the fingers
(2nd - 5th) are elongated, and
Chiroptra the skin extends between them Bat
from the body.
• They become active mainly Bat
during the night.

• They have a long muscular

proboscis.
Proboscida • The two upper incisors grow Elephants
to form what is known as the
two elephant canines. Elephants

• They are the most higher

mammals.
• They have two pairs of the Monkey,
pentadactyl limbs. The thumb
Lemur,
finger lies away from the rest of
Primates Gorilla,
fingers.
• The brain is large in size Chimpanzee,
Monkey
and nervous system is highly and Man
developed in the higher
forms.
Be interconnected with the activities and exercises book: Applied activity: Designing a concept map:
classifying animals.

• There are some organisms that are being difficult to classify

according to Whittaker classification. They include viruses, viroids
and prions.

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 Viruses
Envelop
✲ Viruses represent a link between living
organisms and non-living things. They do not
possess any cellular structures, cytoplasm,
cell membrane or nucleus. They appear in Capsid

a crystalline form and do not possess the

power to carry out any vital process outside
its specific host cell. However, they contain RNA

the nucleic acid DNA or RNA. They can

Figure (47): Structure of the virus
duplicate themselves and reproduce inside
its specific host cells only.
Rabies Herpes Virus
✲ The virus consists of a nuleic acid (DNA virus
or RNA), and a protein coat called capsid,
(fig.47).
✲ Viruses are very minute in size, and cannot
bacteriophage
be seen except by the electron microscope.
✲ Viruses vary in their shapes (Fig. 48). They
may be simple as the rod - shaped, spiral
and spherical, or may be very complex. Measles
virus
Tobacco mosaic virus
✲ Viruses are obligatory parasites, where
they reproduce only inside the host cells. Figure (48): Viruses come in
a veriety of shapes
Outside the host cells, they lose their ability
of reproduction.
✲ Viruses are highly specific organisms. Each virus can infect a cerctain specific
organism; even certain cells of that organism. The viruses which attack the plants,
for example, cannot attack humans or animals, and the viruses which infect liver
cells can not infect brain cells.

Viroids
Viroids are non - living creatures (Pathogenic factors) more simpler than viruses.
They merely short strands of the nucleic acid RNA in a double form (double helix).
They are lacking the protein coat which surrounds the nucleic acid (that is known
in viruses as the capsid)
Viroids apparently enter the nucleus of the infected cell of the organism they
attack, where they direct the synthesis of new viroids. Viroids cause several diseases
to plants such as potato spindle tuber disease, cucumber pale fruit disease and so
on. Viroids may be widely spread in nature, but due to they do not destroy and

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decompose host cells (as viruses) their existance can not be discovered. It is worth
mentioning that, the available information on how viroids spread are very little till
now.

Prions
Prions are non-living creatures. They are structurally simpler than viroids. They
consists of nothing but protein and have no any genetic material of nucleic acids.
They have the ability of spreading throughout tissues of infected organisms and
cause a disease destroys their central nervous system where their brain becomes
spongy riddled with holes as a sieve. This leads to the death of infected organism.
Infection with prions is wide spead in cattles and sheeps, and cause mad cows
disease. Also, prions infect humas by 2 neurological disseases, with symptoms
similiar to that of mad cows disease.
Recently, reserches proved the possibility of trammission of mad cows disease
prions to humans by eating any meat products of infected cows such as hamburgers,
or even using preparations or medicines that some animal prouducts extracted from
infected cows enter in their composition.

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 Science, technology and society

Modern technologies in classification of living organisms:

The studies of first scientists in classification of
living organisms depended upon the morphological
comparisons to determine the similarities and
differences between various organisms. After
that (hundreds years ago), scientists turned to
classify organisms on the basis of determining the
degrees of relevance and relatedness (evolutionary
relationships) among them through their researches
in the field of comparative anatomy for determining A technique of DNA analysis.
the anatomical similarities in natural structures as
skeletal structures and glands, as well as the embryonic development, too.
Nowadays, scientists knowledge of new foundations that can be relied upon
to determine the degrees of relevance and relatedness among living organisms
were increased through the development of microscopic screening techniques
by invention of electon microscope. The recent scientific studies for studying the
similarities between the genera of organisms depended on the scientific researches
on the nucleic acid DNA existing in the nucleus through DNA sequencing technique.
In this technique, the arrangement and sequence of nucleutides of DNA double
strand are identified. Scientists found that the greater the sequence in the order of
nucleatides in DNA strand, the organisms were more relevant and related.

Frontiers in biology
A more recent use for sponges and cnidarians,
especially jellyfish, is in the biomedical and
pharmaceutical industries. Researchers have found
promising new antibiotic and anticancer compounds
in the small percentage of sponge species they have
studied. Researchers are also investigating possible
medical uses for the paralyzing possible medical
uses for the paralyzing toxins that some jellyfish Jellyfish
use to capture prey. This branch of biotechnology is
quite new, but very exciting. Research will probably
result in the development of new medicines.

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 Key terms
• Kingdom: the highest level in taxonomic hierarchy of living organisms.
• Phylum: A taxonomc level represents the biggest group of the kingdom and
composed of classes.
• Species: A group of individuals which have similar morphological characteistics
and mate to produce fertile offspring similar to them.
• Dichotomous key: A series of descriptions ordered in pairs and guide the user
to adentify the species of an unknown living orgunism.
• Viruses: The organisms that gather both characteristics of living organisms and
non-living things.
• Monera: Unicellular prokaryotic organisms, their cell wall is devoid of cellulose
or pectin and they also are devoid of several membranous organelles.
• Protista: Eukaryotic, non-complicated structured organisms, some have cell
walls and plastids, their majority are unicellular and few are multicellular.
• Bryophyta: Terrestrial plants, contain no vascular tissues, and greatly need
wetness for growth and reproduction.
• Ferns: They are structurally simple plants containing vascular tissues, live in
shady wet areas and reproduce by spores.
• Portifera (sponges): They are structurally simple aquatic animals with
asymmetric bodies containing many pores and canals.
• Cnidaria: Aquatic animals, their bodies are radially symmetrical and provided
with stinging cells.
• Arthropoda: A group of animals, their bodies are divided into a number of
segments carry several pairs of appendages, each one consists of several
jointed pieces.
• Mollusca: A group of animals characterized by a soft body covered with a
dermal tissue called mantle that secretes a protective calcareous external or
internal shell.
• Echinodermata: A group of animals characterized by a rigid endoskeleton, and
many of them have spines, prickles and calcareous plates in their body wall.
• Chordata: A group of animals, their embryos are characterized by presence of
a skeletal structure at their dorsal region called the notochord.

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 Summary of living organisms classification
Kingdom Phylum Subphylum Class Sub-class Order Examples
Archaebacteria
Monera

Eubasteria Nostoc and several types of

bacteria

Sarcodina Amoeba

Ciliophora Paramecium
Protozoa
Flagellata Trypanosoma
Protista

Sporozoa Plasmodium

Euglenophuta Euglena

Crysophyta Diatoms

Pyrrophyta Dinoflagellates

Zygomycota Rhizopus (Bread monld)

Fungi

Ascomycota Penecillium - Yeast

Basidiomycota Mushroom

Rhodophyta Polysiphonia

Phaeophyta Fucus

Chlorophyta Clamyclomonas- spirogyra

Bryophyta Riccia - Funaria

Plantae

Ferns Adiantum & Adiantum

Gymnospermae
Pinus
(conifers)
Trachaeophyta
Angiospermae Monocoty- Wheat - Onion - Cactus -

(Flowering ledonae Maize

plants) Dicotyledonae Bean-Pea - Cotton

Porifera Sponge

Hydrozoa Hydra

Cnidaria Schyphzoza Aurellia

Animalia

Anthozoa Sea anemone-Alcyonium

Turbellaria Planaria

Platyhelminthes Trematoda Bilharzia

Cestoda Tape worm

Nematoda
Ascaris - Flaria

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Kingdom Phylum Subphylum Class Subphylum Order Examples
Annelida Earth worm - Leech
Crustacea Prawn - Crab
Flies - Mosquitoes
Insecta - Bees - Cockroaches -
Arthropoda
Moths - Locusts
Arachmida Scorpion - Spider
Myriapoda Scolopendra
Gastropoda Snails - Slugs
mollusca Bivalvia Oysters - Mussels
Cephalopoda Octopus - Sepia
Asteroidea Sea star
Echinodermata Echinoidea Sea urchin
Holothuroidea Sea cucumber
Agnatha Lamprey
Chondrichthyes Shark - Ray
Osteichthyes Bolti - Bouri
Amphibia Frog - Salamander
Chamaeleon - Snake
Reptilia - Lizard - Crocodile -
Turtle
Animalia

Aves Ostrich - Pigeon -

Hawk
Duck - Pilled Platypus -
Prototheria
Spiny ant - eater
Metatheria Kangaroo
Edentata Armadillo - Sloth
Insectivora
Vertebrata

Chordata Carnivora Hedgehog

Lion - Tiger - Wolf -
Perissdactyla
Dog - Cat - Seal
Artissdactyla Horse - Donkey -
Zebra - Rhinoceros
Mammalia
Cetacea Sheep - Goat - Giraffe
- Deer - Camels
Eutheria
Rodentia Whale - Dolphin
Rat - Gerbo - Mouse -
Lagomorpha
Squirel
Chiroptera Rabbit
Proboscida Bat
Primates Elaphant
Monkey - Gorilla -
Primates
Chimpanzee - Man

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 Unit Five

Biological evolution

When you look at the living organisms in your environment and other
environments you’ll be amazed by the enormous variation in their different species.
This variation is not only limited to their morphological characteristics but extends
also to their internal structure. What are the reasons for this variation and what is
its importance? Scientists have been busy searching for how life originated on Earth
when the earth came into existence 4.6 billion years ago. It has been difficult to
determine the exact moment that life on earth originated and the stages that living
organisms on Earth went through in order to appear as we see them now.
The disappearance of certain living organisms and the appearance of new ones
and the change in the characteristics of all other living organisms in order to adapt
to the environment are all evidence of the occurrence of biological evolution.
Through this chapter we will get to know the concept of biological evolution and
the evidence which supports it and the mechanisms that explain it.

For mo
r e inform h e ne t .
ation about log in t
the topic of Biological evolution,
 Time Management
To achieve maximum benefit from this unit, you need to:
• Manage your time between practical study, theoretical study, searching and
expanding in information resources.
• Carefully record the results of your practical study, it’s the best way to support
your learning.

Learning Outcomes
By the end of this unit, the student should be able to:

• Explain theories of the emergence of life on Earth. • Explain that an increase in variations in living organisms
• Identify what’s meant by “Biological Evolution”. increases their chances of survival.
• Illustrate the role of natural selection and isolation in the • Mention the reasons of small population extinction
emergence of new species. • Demonstrate some evidence of evolution in living organ-
• Illustrate the role of genetic drift, mutation and competi- isms.
tion in evolution. • Illustrate evolutionary relationships between some types
• Compare between natural selection and artificial elec- of living organisms using a cladogram.
tion. • Appreciate the greatness of Allah in the emergence of life
• Illustrate that evolution is based on the variation and ad- on Earth and the evolution of living organisms
aptation in living organisms.
• Explain the Hardy-Weinberg conditions for maintaining
genetic equilibrium in population.

f ution
igin o
p
Cha
2:
pter
Cha
Unit Five
Chapter 1

Origin of living organisms and

mechanisms of their evolution

By the end of this chapter you

should be able to: Till now Earth is considered the only planet which
• Explain theories of the origin of life on has all the factors of life, and many types of organisms
Earth.
• Identify what is meant by evolution. live on it. And so far, the origin of life is still unknown.
• Illustrate the role of natural selection There are two directions to determine the origin of life;
and isolation in the emergence of new
species. the first is that the organic components from which life
• Compare between natural selection originated came to Earth from space. The other indicates
and artificial selection.
• Illustrate the role of genetic drift, muta- that life originated from Earth. Scientists believe that
tion and competition in evolution. the first living organisms to emerge on the surface of
• Illustrate that evolution is based on the
variation and adaptation in living or- the Earth were bacteria. Then other organisms began
ganisms. appearing.
• Explain the Hardy-Weinberg condi-
tions for maintaining genetic equilib- ✍ How did life on Earth originate? How did
rium in the population.
• Explain that an increase in variations it develop? What evidence proves the
in living organisms increases their occurrence of evolution?
chances of survival.
• Mention the reasons for extinction.
Life origin theories
The question to which scientists are searching for
an answer regarding the origin of life will remain “how
did life originate on the surface of the Earth?” Many
attempts were made to explain the origin of life on Earth
Key terms including :
• Evolutionary tree
• Natural selection Special creation theory:
• Artificial selection
• Mutation This theory assumes that all living organisms on the
• Genetic equilibrium surface of the Earth were created in their current image
• Genetic drift
and that these organisms have not changed at all so far.
• Variation
• Adaptation ✍ What do you think of this theory?
• Isolation
• Extinction

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Spontaneous generation theory:
This theory assumes that living organisms can emerge all of a sudden and
spontaneously from any inert matter. Like the emergence of mice from dirty straw.
✍ Do you support this theory? Why?

The theory of universal origin of life

This theory assumes that life arrived to Earth in the form of germs like bacteria
from other heavenly bodies like meteors which means that life originated in space.
✍ What do you think of this theory?

The theory of Earthly origin of life:

In 1953 sciaentists Urey and Miller were able to transform Methane (CH4),
hydrogen (H2), ammonia (NH3), water (H2O) and carbon monoxide (CO) to amino
acids in the presence of strong electrical charges for long periods of time. Amino
acids are considered the building blocks of proteins. They received a Nobel Prize in
appreciation of their efforts.
And so the supporters of this theory believe that life originated on Earth as a
result of chemical reactions between some materials. These reactions were very
slow and complex and lead to the formation of amino acids from which proteins are
formed and that these reactions lead at the end to formation of protoplasm which
forms the living matter of organisms.
✍ Has this theory succeeded in uncovering the origin of life and the
secret of the origin of living organisms?
✍ Which theory do you think is the most appropriate and the closest to
the scientific method of thinking?
✍ Did living organisms originate in their current form like the special
creation theory indicates? Or do changes occur to them?

Evolution of living organisms:

Evolution: is a slow and gradual changing process that occurs to the characteristics
of living organisms over a long period of time.
✲ The supporters of the evolution theory see that the idea of biological
evolution depends on the following principles:

1 Each type of living organisms originated from a previously existing type which
was more primitive and simpler in its structure.

2 Living organisms constantly undergo changes in their shape, structure and

functions.

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 3 The changes that occur to living organisms are Do you know?
very few but their accumulation over time, eras
and over millions of years leads to considerable The opinions of some
philosophers about the origin
variations which cause the emergence of new
of living organisms and their
species of living organisms. evolution:
Thales: Living organisms
4 The number of living organisms is variable and
originated from water‫ﺍ‬
not all of them originated at the same time; Alexander: Living organisms
they originated gradually and evolved until originated from a mixture of
they became what they are now in their current water and sun.
forms. Aristotle: Believes in the concept
of gradual transformation from
the simple to the complicated.

Mechanisms of evolution

1 Natural selection:
British scientist Charles Darwin (1809-1882) took his
famous trip around the world in 1831 which lasted for five
years and he noticed during passing by some islands a
considerable variation between different living organisms
especially the beautiful birds he saw in the Galapagos
Islands. Darwin noticed that these birds have obvious
variations and differences in the shape of their beaks.
Darwin explained this variation in the birds’ beaks is due to
the adaptation of each species with the nature of its food and
that the beaks evolved via natural selection.
Figure (1): Darwin

Insect eaters

Common
ancestor Seeds eaters
Cactus eaters

Fig. (2) Different shapes of bird beaks to adapt to different types of

food
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 The explanation of natural selection:
kinds of living organisms face factors of extinction so the weak ones that are
unable to face the conditions of the environment die and cannot pass down their
genetic traits while only the strong organisms that have characteristics and traits that
suit their environment survive and pass down these traits to their offspring and with
time the strong traits accumulate which lead to the emergence of new species from
the old ones. Sexual selection helps the occurrence of natural selection since both
male and female tend to mate with the strongest and fittest, thus the good traits are
inherited by the resulting offspring while the weak traits disappear because of the
lack of tendency of animals to mate with weak members.
Be interconnected with the activities and exercises book: Assessment activity.

Artificial selection:
During his experiments on pigeons, Darwin
realized that any trait can be increased or decreased
between members through specifying the mating
members. Darwin concluded that what happens in
natural selection is similar to what happens during
artificial selection and achieves the same results but
requires a longer period of time. Fegure(3): Friesian cow strain is
the result of artificial selection
• Artificial selection has lead to the emergence of some
new animal strains as a result of human interference Life applications
which lead to the evolution of these strains like the
friesian cow strain. Fig. (3). Cattle herders hybridize
different strains with the
✍ What are the conditions of survival of these
purpose of uniting the qualities
new strains and ensuring that they do not of both strains together into
become extinct in the future? one strain, thus creating a new
• Artificial selection is directed unlike natural strain which contributes to the
selection which occurs without guidance except for evolution of living organisms
the factors of nature. through artificial selection.

• Natural selection in its new concept is the selection

of the most capable members to adapt with the conditions of the environment
as a result of the accumulation of the inherited traits that help them to exist and
continue.
2 Competition between living organisms: Thinking Corner
Competition between members of the same The constant struggle
species or between different species increases the between predator and prey
chances of natural selection and includes competition has aides the evolution of each
for food or shelter and it’s called “environmental of them and the females’ choice
selection” or competition for mating which is called of the strongest males to mate
“sexual selection” . with has helped in the evolution
of their offspring. How do you
✍ How does competition between organisms prove that with some examples?
help in their evolution?

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 3 Mutation:
Most evolution scientists think that natural selection is not enough to induce
significant variation in living organisms. Mutations also act to change the genetic
material which leads to the appearance of new traits that did not exist originally.
Mutations could be positive or negative. And they represent the primary material for
genetic variation which is necessary for evolution to occur. Examples of mutations
that create a marked evolutionary change are those mutations that occur to some
types of microbes (like bacteria) which increases their resistance to antibiotics.
The results of these mutations are new genetically altered organisms that
increase the variation of living organisms, and natural selection chooses the best
mutations and maintains them and gets rid of the others with bad mutations. This
means that natural selection acts as a sieve for mutated living organisms.

4Population genetics:
The population is a group of members of a certain species who live in a
specific place and mate randomly in between themselves. The genes of these
members represent the gene pool of the population. And by counting the
number of phenotypes associated with a certain trait and determining if the
genes are dominant or recessive we can calculate the rate of prevalence of
these genes in the gene pool of this population.

The Hardy-Weinberg Law

Scientists Hardy and Weinberg concluded that there is a
tendency for the rate of prevalence of any gene as well
as the phenotypes associated with it to remain constant
within the population from generation to generation. This
means there is a tendency for genetic equilibrium within
the population which ensures its survival and the constancy
Weinberg of its genetic traits. Hardy

Hardy and Weinberg asserted 7 conditions for genetic equilibrium:

1 The size of the population must be large to ensure that all genetic traits are
represented.

2 All members of the population must be of the same strain.

3 Mating between members of the population must occur at random so that

mating isn’t in favor of a certain characteristic alone.

4 The hereditary trail should not be subject to natural selection which may
protect the individuals or destroy them.

5 Members with certain genetic traits do not migrate out of the population and
others do not migrate into it.

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 6 No mutations occur which lead to new genetic traits.

7 Parents produce equal numbers of offspring.

✲ If one or more of these conditions is changed, the genetic equilibrium of the
population will be affected and it will then walk in a new direction known as
genetic drift which causes the evolution of the population.

5 Variation:
Variation helps the genetic traits of living organisms to adapt to the changing
conditions of the environment and ensures their survival. Variation occurs between
members of the same species for several reasons including :
• Sexual reproduction: Occurs between genetically different gametes and
increases the variation of members of the same species.
• Multitude of genetic traits of members of the same species which leads to their
variation.
• Gene interactions: causing them to affect each other which could lead to new
traits.
• Chromosomal crossing over during meiosis increases variations between
gametes.
• The effect of different environmental factors in the appearance of the effect of
genes responsible for certain traits.
• Genetic and chromosomal mutations.

6 Adaptation:
• Adaptation is the appropriateness of any structure in the living organism’s body
to the function it performs. Living organisms possess genetic traits that enable
them to adjust to their environment, survive and reproduce. For example: gills in
fish and wings in birds.

Wings in birds Gills in fish

Fig. (4) Adaptation helps living organisms to survive

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 7 The role of isolation in the emergence of new species of living
organisms:
Scientists think that in order for a new species to originate some members of the
population must become isolated and prevented from mating with the rest of the
population. This is known as reproductive isolation which leads to an imbalance of
the genetic equilibrium and the occurrence of genetic drift which affects its genes
leading after a period of time to the emergence of new species of living organisms.
Reproductive isolation occurs due to many reasons including geographical
isolation that occurs in cases of geographical barriers like seas and mountains
which prevents the mating of members of the same species.

8 Extinction:
Is the gradual reduction in the members of the species of living organisms which
leads to its disappearance. The reason for the extinction of some living organisms
is their inability to adapt to the changes that accompanied changes in the Earth
throughout different eras and the subsequent environmental and climate changes.
Whereas many species of living organisms were able to successfully adapt to these
changes.

Fig. (5) Giant reptiles have been extinct from 62 Million years

✲ Reasons of extinction:
1 Competition for limited resources known as competitive elimination in which
one species of living organisms can surpass another species thus one of them
survives while the other starves and dies out because of its inability to compete
with other species.
2 Climate changes are harmful to living organisms like droughts which lead to
the disappearance of many plants. Thus the animals that feed on these plants
die and become liable for extinction.

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 3 Introducing new species that compete with the original ones.
4 Heavinly bodies hitting the Earth which is one of the assumptions that
explained the extinction of giant reptiles like the dinosaurs.
5 Human activities: over cutting of trees, excessive hunting, drying water bodies
and environmental pollution.
✲ The effects of extinction on biological equilibrium:
The extinction of species doesn’t only mean the absence of a renewable source
from the environment but it negatively affects the biological equilibrium in it and
cause a disruption of the ecosystem in varying degrees; since biological equilibrium
in any ecosystem is connected to the variation of the species living in it; the more
numbers of species there are the more equilibrium continues, and the less species
there are the more equilibrium is disrupted

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Unit Five
Chapter 2

Evidence of Evolution Occurrence

By the end of this chapter you

should be able to: Evolution Theory – the currently most accepted
• Illustrate some evidence of evolution theory - has presented much evidence that proves its
in living organisms.
validity. Among these evidences are fossils, taxonomy,
• Illustrate evolutionary relationships
between some species of living organ- comparative anatomy, vestigial structures, physiological
isms using a cladogram. resemblance, fetal growth stages and molecular biology.
• Appreciate the greatness of God in cre-
ating life on Earth and the evolution of
living organisms. 1 Fossils
Fossils are the remains or traces of some living
organisms that lived long before the current age under
different conditions from the current ones, then died
and were buried in the sediment that forms sedimentary
rocks. (Fig. 6).

Key terms
• Fossil
• Index Intermediate links
• Mold
• Cast
• Trace

Figure(6): fossilized skeletons and shells

✍ Are skeletons and shells in the above

figure considered fossils? Why?
✲ Conditions of fossil formation:
• Presence of a rigid skeleton of the living organism.
• Burial of the living organism directly after death in
sediment that protects it from decomposition.

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• The presence of an appropriate mineral medium that replaces the organic
components of the organism.
Fossils are an evidence of the existence of these organisms in the past. However
nature did not allow formation of fossils for every type of organisms because of
factors that prevented the fossilization process from taking place like:
• Water running out in the porous layers of sedimentary rocks which leads to
decomposition of the organism remains.
• Earthquakes and volcanoes which lead to breaking and deformation of fossils.

Index Fossil:
It is the fossil of a type of organisms that appeared and lived for a short period of
the geological history of the Earth then disappeared but had a wide spread in multiple
environments.

Fig. (7) How do you explain the presence of a fossil of some whales in whale valley in the Fayyoum
desert?

Importance of studying fossifs: Thinking corner

✲ The study of fossils is useful in many fields like:
Scientists were able
1 Determining the geological age of rocks by to conclude the ancient
determining the age of fossils buried in them. climates of some areas
2 Identifying features of ancient environments. through the fossils found
in them. A fossil that’s
3 Presenting evidence of the evolution of living
10 million years old was
organisms.
discovered in rocks in a
4 Emulation of rock layers through index fossils. cold areas and when it was
5 Drawing ancient geographical maps; where compared with others of
the same species of living
fossils have helped change our information about
organisms it was found that
the geographical distribution of the surface of the they currently live in warm
Earth; they have provided information that helped seas. What do you conclude
in knowing the distribution of water and land in from that?
ancient times.

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 Examples of fossils:
The original remains of a living organism: This fossil could be of a complete
organism with all its parts like the Mammoth fossil which was buried in ice. The
Mammoth is a type of elephants that lived in Europe 20,000 years ago. (Fig. 8).
The fossil may be the bones and teeth of an organism that died, was buried, its
soft tissue decomposed and only the rigid parts like teeth and bones remained.
Example: bones and teeth of dinosaurs (Fig. 9).

Fig. (8) Mammoth elephant fossil Fig. (9) Dinosaur bones fossil

Petrified remains: Like petrified forests in Al Qattameya in which silica replaces tree
fibers, thus preserving the original shape of the trees. (Fig. 10).

Use your activity and exercise book: practical activity: examples

of mold and cast

Mold, cast and trace:

Mold: Bears the internal details of the rigid skeleton of
the organism after its death like Ammonite fossils in sedi-
mentary rocks (fig. 11).
Cast: Is the mark left by a living organism after its death
in contact with a soft rock then decomposition took place. Fig. (10) Petrified forest fossils

Like the cast left by leaves or fish bones in rocks (fig. 12)
Trace : Is the print left by an organism during its life on soft
rocks like footprints left by dinosaurs on rocks as evidence of
their activities (fig. 13)

Fig. (11) Ammonite fossil

Fig. (12) Fish fossil (Cast) Fig. (13) Dinosaur footprint (trace)

Be interconnected with the activities and exercises book: Applied

138 activity: Field trip to petrified forest in Al Qattameya.
The Fossil Record:
A complete group of fossils charting the
progress of organism during geological ages
like the fossil record of horse and elephant.

The fossil record of horse:

The fossil record of the horse indicates that Fig. (14) The fossil record of the horse
the first ancestors of the horse were smaller and
their forelimb ended in four toes and a trace
of a fifth. Their hind limb ended in 3 toes
and a trace of a fourth. A long time after that
they evolved, became bigger and their limbs
ended in 3 toes, the biggest of which is the
middle which the animal leans on during
running, then evolution continued and the
limbs ended in one toe with two little ones
on the sides that don’t touch the ground
then they evolved to become in the form we
see today.

✍ What do we conclude from studying

the fossil record of the horse?

Fig. (15) Diagram indicates fossil record of

horse
Transitional (intermediate) fossils:
Are fossils that combine in their characteristics
the features of two different consecutive classes for
example: a fossil of an ancient bird called Archaeopteyrx
that combines in its characteristics between the birds
and reptiles which confirms the existence of a link
between two species of living organisms. This bird
bears many features of birds including the presence
of feathers, a beak, the presence of vertebrae in the
tail and claws in wings. These fossils are known as
intermediate or transitional fossils.

Fig. (16) Archaeopteryx fossil

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 2 Taxonomy
Through your study of the topic of taxonomy you will notice that:
There is an obvious progression through different classes from simple to complex
and a progression in sophistication from one class to the other for example the
animal kingdom begins in sponges and ends in mammals.
This order of living organisms resembles
a branching tree that suggests the idea of
evolution and organizes living organisms
through the branches of the tree from simple
(the lowest branches) to complicated (highest
branches). This has lead to the discovery of
gaps in the sequence of living organisms
Scientists have succeeded in filling
these gaps in the sequence by placing some Fig. (17) Lung Fish
extinct organisms (intermediate fossils) or
contemporary organisms that combine in their structure the characteristics of a
certain class and those of the following class in the classification. For example :
✲ Archaeopteryx: fills the gap between reptiles and birds.
✲ Lung fishes : breathe using gills in water like fish and breathe with what
resembles a primitive lung in conditions of drought like amphibians.

Evolution Tree (Cladogram):

The evolution tree illustrates the relationship between different species and
groups. Figure 18 illustrates many consecutive types from a common ancestor
where four legged creatures appeared 360 million years ago and they were the
ancestor of all vertebrates.
Study the cladogram (Fig. 18) then answer the following questions:
✍ Which creatures appeared 150 million years ago and which appeared
300 million years ago?
✍ Which time witnessed common ancestors for each of the following:
(human and horse- human and frog- lizards and alligators)?
✍ When did the dinosaur become extinct?
✍ Which reptile is closer to birds, lizards or crocodiles?

140
 Crocodiles

Birds
Lizards
Turtles
Cartilagenous fish

Actinopterygii

Sarcopterygii

Dinosaurs

Mammals
Amphibians

Reptiles

Reptiles

Reptiles
Archaeopteryx

Reptiles
Age (million years)

Ostracoderms

Tetrapode organisms

Fig. (18) The organisms evolution tree (cladogram)

• All groups present in the figure share the presence of a spine which confirms
that they share a common origin.
• Some fossils like the Archaeopteryx appeared as a link between two groups of
vertebrates which are reptiles and birds thus confirming the evolution theory.
• The tree of life summarizes the relationship between consecutive species
and groups starting with common ancestors. The tree of life also allows us to
estimate the degree of relation between different species.
Be interconnected with the activities and exercises book: Practical activity: The cladogram.

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 3 Comparative anatomy
There are similarities and differences between living
organisms according to which they are classified; animals Enrichment
are classified into vertebrates and invertebrates based on Comparative anatomy:
whether or not they have a spine. Is the science which
concerns the studying of
• Vertebrates are similar in that they have a skull which
similarities and differences
contains the brain and blood which contains blood cells in anatomy of different
containing hemoglobin. living organisms organs.
• The limbs of vertebrates are similar in structure and
differ in shape where they modified in order to fit their function.
• Check the following figure which illustrates the limbs of some vertebrates then
answer the following questions:

Fish Reptiles
(turtle)

Birds (pigeon)

Mammals
(man)
Mammals
Amphibians
(Bat)
(toad)

Fig. (19) Adaptation of fore limbs of vertebrates. (Symmetric parts in the figure are
indicated in the same color)

✍ Why did the fore limbs of fish adapted into fins while in birds they
adapted into wings?
✍ What do you conclude from comparing these parts in vertebrates?
This similarity in structure indicates that vertebrates originated from a common
origin but adapted to fit the functions they perform.

4 Vistigial structures
The evidence that vertebrates originated from a common ancestor is that some
organs which used to perform necessary functions in ancient ancestors and have
now become unnecessary and atrophic.
✲ Examples of vestingial organs :
1 The appendix: releases enzymes to digest cellulose present in plants. So they
are nonexistent in carnivores (lions) and developed in herbivore (rabbits), and
atrophied in humans. It’s believed that it used to be developed in ancient humans
who fed on plants.

142
 2 The muscles that move the ear: are developed in most mammals like horses
and dogs in order to direct the ears towards the direction of sound and they are
atrophied in humans.
3 Coccygeal vertebrae : they are the
vertebrae at the end of the vertebral column
which forms the tail in many animals and
are atrophied in humans.
4 The nictating membrane : a transparent
membrane apparent in the eyes of birds and
reptiles to protect them from sand carried on Figure(20): The nictating membrane
the wind and intense light. This membrane
atrophies completely and disappears from the eyes of humans.

5 Physiological resemblance
✲ Living organisms are similar in many biological functions including :
1 Protoplasm : all living organisms share in the presence of protoplasm in which
the metabolic processes occur which include building and break down processes
that occur in similar ways in the cells of all living organisms .
2 Cellular division : cellular division occurs in the same method in all living
organisms under the control of the nucleus which contains the genetic material in
similar forms which are the chromosomes .
• The presence of protoplasm and occurrence of cellular division indicate that all
living organisms originated from a common origin.
3 Waste products : living organisms share that they all get rid of waste products
in the form of nitrogenous compounds but the quality of these compounds differs
according to the organism’s environment .
• Fish get rid of their nitrogenous wastes in the form of ammonia through gills
because it dissolves quickly in the surrounding water.
• Amphibians and mammals get rid of nitrogenous wastes in the form of urea
through the kidneys because it dissolves quickly in the water content of the urine.
• Reptiles and birds get rid of nitrogenous wastes in the form of uric acid with
feces because it cannot dissolve in water..
4 Hormones : vertebrates are similar in that they have glands that secrete the
same hormones responsible for organizing biological processes in the body like
digestion, growth and reproduction
✲ How do you explain injection the diabetic patient with insulin derived from
the pancreas of cattle?

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 6 Fetal growth stages
• All living organisms which reproduce sexually begin their lives as a single cell
called the zygote.
✍ Follow the fetal growth stages of fish, amphibians, reptiles, birds and
mammals in (fig. 21). Are there differences between different classes?

Fish Amphibians Reptiles Birds Mammals

Fig. (21) Fetal growth stages in vertebrates

• The fetuses of fish, amphibians, reptiles, birds and mammals go through similar
stages. They have little gill slits and a heart made up of two compartments (atrium
and ventricle). With the continued development, obvious changes occur that
distinguish each class from the others.
✍ Can you discriminate easily between fetuses of a group of mammals
like a dog, a cat and a rabbit in their early fetal stages?
• The fetal resemblance in species of mammals indicates that they all originated
from a common origin.
• The fetus of bird gets rid of nitrogenous wastes in the early stages (inside the egg)
in the form of ammonia (like fish) then after a while, this wastes are released in the
form of urea (like amphibians) and at the end of development they are released as
uric acid.

7 Molecular biology
Molecular biology is considered among the recent evidence which agrees with the
evolution theory. The genetic material in all living organisms is made up of the same
building blocks. This indicates that they originated from a common origin.

Be interconnected with the activities and exercises book: Assessment activity.

144
 Science, technology and society

Natural reserves:
A natural reserve is an area of nature including all of its living organisms and
natural phenomena and is surrounded by an isolating space in order to protect
it from natural conditions or human activity. Natural reserves are considered one
of the most important ways of conserving endangered species. These reserves
provide protection for natural resources and biodiversity. And they act to maintain
environmental equilibrium, in addition to their use for touristy purposes.
The Arab Republic of Egypt is considered one of the nations that has many
natural reserves which are characterized by their beautiful scenery. There are 30
reserves in Egypt: Ra’s Mohammed reserve, Tiran and Sanafir Islands, Saint Katherine
reserve, Nabq reserve, Abo Jalom reserve in South Sinai, Zaraneeq reserve, Sabkhet
El Bardawil in North Sinai, Elba reserve in Red Sea Governorate, Al Ameed
reserve in Matrouh, Ashtoom Al Gameel reserve, Tenees Island in Port Said, Wadi
Al Alaqi reserve in Asswan, Wady Al Rayyan reserve and Qaroon Island reserve in
Al Fayyoum.

Estimating the age of fossils

The age of fossils is estimated by measuring the percentage of radioactive carbon
in them. The dating of radioactive carbon has created a stir since it was first used by
American chemist Willard Libby in 1949 after he gave a precise estimate of the age of
an organic matter like bones, hair, plants, natural textiles and wood.

Radioactive carbon is a radioactive analogue of

carbon and called carbon 14. It’s produced when
cosmic radiation reaches the Earth’s atmosphere in
a concentration which occurs everyday. Carbon 14
behaves in the same way as other non radioactive
analogues of carbon like carbon 12 and carbon 13 in
that it interacts with oxygen forming carbon dioxide. All
plants absorb carbon 12 and its radioactive analogue,
carbon 14 during photosynthesis process thus it reaches
the tissues of humans and animals through absorption A fossil of Dinosaur

after eating these plants. The percentage of carbon 12 and carbon 14 in the bodies
of living organisms is similar to their percentages in the atmosphere at that time and
when organisms die the amount of carbon 12 remains constant whereas the amount of
carbon 14 decreases without being replaced by new amounts as occurs during the life
of the organism.
s

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 Key terms

• Evolution: A slow and gradual changing process that occurs in the characteristics
of living organisms over a long period of time.
• Natural selection: The selection of the most capable members to adapt with
the conditions of the environment as a result of the accumulation of the inherited
traits that help them exist and survive.
• Mutation: A change which occurs in the composition of the genetic material
and leads to the appearance of new traits.
• Hardy-Weinberg Law: the rate of prevalence of any gene in the population from
generation to generation is constant and so are the phenotypes and genotypes
related to that gene.
• Genetic drift: An evolutionary force working with natural selection to change
the characteristics of the species of living organisms over time and it occurs in
small populations.
• Adaptaion: The appropriateness of any structure in the body of the living
organism to its function which guarantees its survival.
• Extinction: The gradual decrease in the members of a species of living organism
which leads to its disappearance.
• Fossil: The remains or traces of some living organisms that lived a long time
ago before the current era and were buried after their death in sedimentary rocks.
• Index fossil: Is the fossil we depend on in comparing two layers of sedimentary
rocks in order to determine their relative ages.
• The fossil record: A complete set of fossils charting the progress of organism
during geological ages like the fossil record of horses and elephants.
• Transitional (intermediate) fossils: Are fossils that gather in their characteristics
the features of two different consecutive classes confirming the connection
between them, for example: The Archaeopteryx fossil (gathers features of birds
and reptiles)

146
 Concept map of unit Five

Origin and Evolution of life

Evolution mechanisms Evidence of evolution occurrence Life origin theories

Natural selection Special creation theory

competition Spontaneous generation theory

Mutations Universal origin

of life theory
Genetic drift
Earthly origin of
Variation life theory

Isolation

Molecular Fetal Physiological Vistigeal Comparative Classifi- Fossils

biology growth resemblance structures anatomy cation and fossil
stages record

Trace Cast Mold Petirified Rigid part of the Entire fossil

remains organism
such as such as such as such as such as such as

Dinosour Dinosour Petirified Ammonite Fish Mammoth

footprint bons forests

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 ‫ﻣﺼﺎﺩﺭ ﺍﻟﺘﻌﻠﻢ‬

‫‪ 1‬ﺳﻼﻣﺔ ﻣﻮﺳﻰ‪ ،‬ﻧﻈﺮﻳﺔ ﺍﻟﺘﻄﻮﺭ ﻭﺃﺻﻞ ﺍﻹﻧﺴﺎﻥ‪ ،‬ﻣﻜﺘﺒﺔ ﺍﻟﻤﻌﺎﺭﻑ‪1999 ،‬ﻡ‪.‬‬

‫‪ 2‬ﺷﻴﺨﺔ ﺳﺎﻟﻢ‪ ،‬ﺍﻟﻮﺭﺍﺛﺔ ﻣﺎ ﻟﻬﺎ ﻭﻣﺎ ﻋﻠﻴﻬﺎ ‪ ،‬ﺩﺍﺭ ﺍﻟﻤﻨﺎﻫﻞ ﻟﻠﻄﺒﺎﻋﺔ ﻭﺍﻟﺘﻮﺯﻳﻊ‪2003 ،‬ﻡ‪.‬‬
‫‪ 3‬ﺭﻳﺘﺸﺎﺭﺩ ﻭﻭﻛﺮ ) ﻣﺘﺮﺟﻢ(‪ ،‬ﺍﻟﺠﻴﻨﺎﺕ ‪ ،‬ﺍﻟﺪﺍﺭ ﺍﻟﻌﺮﺑﻴﺔ ﻟﻠﻌﻠﻮﻡ‪2006 ،‬ﻡ‪.‬‬
‫‪ 4‬ﻋﺒﺪ ﺍﻟﺤﺴﻴﻦ ﺍﻟﻔﻴﺼﻞ‪ ،‬ﺍﻟﻮﺭﺍﺛﺔ ﺍﻟﻌﺎﻣﺔ ‪ ،‬ﺍﻷﻫﻠﻴﺔ ﻟﻠﻨﺸﺮ ﻭﺍﻟﺘﻮﺯﻳﻊ‪1999 ،‬ﻡ‪.‬‬
‫‪ 5‬ﺣﻤﺰﺓ ﺃﺣﻤﺪ ﺍﻟﺸﺒﻜﺔ ‪ ،‬ﺍﻷﻃﻠﺲ ﺍﻟﻮﺻﻔﻰ ﻓﻰ ﺍﻟﺘﺸﺮﻳﺢ ﻭﺑﻴﻮﻟﻮﺟﻴﺎ ﺍﻟﺨﻠﻴﺔ ﻭﺍﻷﻧﺴﺠﺔ ﻭﺍﻷﺟﻨﺔ‪ ،‬ﺍﻟﺪﺍﺭ ﺍﻟﻤﺼﺮﻳﺔ‬
‫ﺍﻟﻠﺒﻨﺎﻧﻴﺔ‪2005 ،‬ﻡ‪.‬‬
‫‪ 6‬ﻓﺘﺤﻰ ﻣﺤﻤﺪ ﻋﺒﺪ ﺍﻟﺘﻮﺍﺏ‪ ،‬ﺑﻴﻮﻟﻮﺟﻴﺎ ﻭﻭﺭﺍﺛﺔ ﺍﻟﺨﻠﻴﺔ‪ ،‬ﺍﻟﺪﺍﺭ ﺍﻟﻌﺮﺑﻴﺔ ﻟﻠﻨﺸﺮ ﻭﺍﻟﺘﻮﺯﻳﻊ‪.‬‬
‫‪» 7‬ﺍﻷﺳﺎﺳﻴﺎﺕ ﺍﻟﻤﺘﻜﺎﻣﻠﺔ ﻟﻌﻠﻢ ﺍﻟﺤﻴﻮﺍﻥ« )ﺃﺭﺑﻌﺔ ﺃﺟﺰﺍﺀ(‪ ،‬ﺍﻟﺪﺍﺭ ﺍﻟﻌﺮﺑﻴﺔ ﻟﻠﻨﺸﺮ‬

‫ﻛﻴﻤﻴﺎﺀ ﺣﻴﻮﻳﺔ‪http://ar.wikipedia.org/wiki/‬‬
‫ﻛﻴﻤﻴﺎﺀ ﻋﻀﻮﻳﺔ‪http://ar.wikipedia.org/wiki/‬‬
‫ﺧﻠﻴﺔ‪http://ar.wikipedia.org/wiki/‬‬
‫ﺗﻮﺭﻳﺚ‪ar.wikipedia.org/wiki/‬‬
‫‪www.khayma.com/mtwan/kalia2.htm‬‬
‫‪bio.olom.info/cell1.pdf‬‬
‫‪www.eajaz.org/index.../600-Hidden-Secrets-in-the-life-of-the-‬‬
‫‪http://bio2.shtechclub.org/cd/bc_campbell_biology_7/index.html‬‬
‫‪http://www.emc.maricopa.edu/faculty/farabee/biobk/biobooktoc.html‬‬
‫‪http://www.ckfu.org/vb/t309065.html‬‬

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