Biology and

Health Sciences
FOR RWANDAN SCHOOLS

Senior 1 Senior
Student’s Book
 © 2020 Rwanda Basic Education Board
All rights reserved.
This book is the property of the Government of Rwanda.
Credit must be provided to REB when the content is quoted.
 © 2020 Rwanda Basic Education Board
CONTENTS All rights reserved.
This book is the property of the Government of Rwanda.
Credit must be provided to REB when the content is quoted.

Topic 1 Biodiversity and classification 1

Unit 1: Introduction to Biology 2

Unit 2: Introduction to classification 14
Unit 3: The external structure and importance of
flowering plants 24
Formal assessment 35

Topic 2 Organisation and maintenance of life 37

Unit 4: Magnifying instruments and biological drawings 38

Unit 5: Plant and animal cells 47
Unit 6: Levels of organisation in multicellular organisms 55
Unit 7: Food nutrients and diet 65
Unit 8: Structure and functions of human gas
exchange system 80
Unit 9: Tropic responses 87
Unit 10: Skeletal systems of organisms 93
Formal assessment 105

Topic 3 Health and disease 107

Unit 11: Classification of diseases 108

Unit 12: Human reproductive system 118
Unit 13: Puberty and sexual maturation 130
Unit 14: Reproduction, pregnancy and childbirth 136
Formal assessment 145

Glossary 148
Index 153
How to use this book

The learning
The book is objective says
divided into what you will
units. learn.

The key
competence
is from the
curriculum. Every unit has
activities and
Cross-cutting exercises.
issues are
dealt with.

Checklist of
learning.
Formal assessment
1. a) A learner views a specimen using a microscope. The eyepiece objective lens
used is 10× magnification, and the nosepiece objective lens is 40× magnification.
What is the total magnification? Show your working out. (3)
Formal
b) A learner draws a seed that measures 1,5 cm in length. Her drawing is
9 cm in length. What is the magnification of the drawing?
2. Complete the table below by filling in the missing information.
(1) assessment
Plant cell Animal cell
with marks.
Self-assessment Shape

Outer covering

Organelles
Vacuoles
(10)
3. a) Define each of these words.
i) tissue ii) organ (2 × 2 = 4)
b) Identify the tissues in A and B.
A B

(2 × 2 = 4)
c) Give one function of each tissue you gave in your answer to question b). (4)
4. Provide labels for parts 1 to 7 in the drawing of the respiratory system.

5
2

3 6
4

7
(7)

Formal assessment 109

TOPIC

1 Biodiversity and classification

Sub-topic Biodiversity
Unit 1 Introduction to Biology
Sub-topic Classification of living things
Unit 2 Introduction to classification
Unit 3 The external structure and
importance of flowering plants

Figure 1.1: There is a great diversity of living things in Rwanda.

1
 UNIT 1 Introduction to Biology

Key unit competence At the end of this unit, I should be able to:

To be able to explain • Define Biology and state its main branches

the meaning of
• Explain the importance of studying Biology
• Identify different forms of life from a wide range of organisms
biology and its • List the characteristics of living things
application , recall • Explain the principles of the first aid and how and when first aid kit is used
the characteristics • Compare characteristics of life throughout different groups of organisms focusing
common to all on their nutrition, respiration, excretion, reproduction, growth, sensitivity and
organisms and be able movement
to apply safety and first • Compare living things and explain their differences
aid in daily life.
• Practice rules and regulations governing the laboratory and know how to avoid
accidents
• Use first aid kit
• Know what to do if someone is injured in the laboratory
• Acknowledge the diversity and uniqueness of different organisms
• Appreciate the importance of Biology in society.

Introductory activity
1. Around you, there are huge number of things. Suggest the ones which are living, are non-living. Which
characteristics have helped you to group those things?
2. Name the two main groups of animals and give an example of each?
3. Among the sciences that deal with different studies, which one concerns the living things?
4. Observe the living things below. What are the possible interactions with their environment?

Topi Water lily Hippo

Algae, viewed under a microscope Forest cobra Black-headed gonolek

Figure 1.2: Different living things

2 Topic 1: Biodiversity and classification

1.1. Introduction to biology and different branches of biology
Meaning of Biology

Activity 1.1

1. Think about the world around us. Every day you see living things. Some of these living organisms are
plants, such as trees, grasses and flowers. Others are animals, such as birds, insects and dogs. Where
do they get their energy from? How do they move? What are they made of?
2. Discuss the following
a. What is biology?
b. What are branches of biology?

The word Biology comes from two Greek words: bios, which means life, and logos, which means knowledge.
Biology therefore means the study of life, or living organisms.
Branches of Biology
Biology is a subject that covers many different aspects. Some examples of branches of Biology are shown
below.
Taxonomy – Cytology – Microbiology –
Mycology – Parasitology –
study of the study of cells, study of microscopic
study of the which are the study of parasittes
classification of living things (micro-
fungi building blocks of organisms), such as
living things, how
they are identified, all organisms bacteria and viruses
and what makes
them similar and/or
Ecology –
different
study of the interaction
between living things
Genetics – and their environment
study of how the Branches of Biology
characteristics of
living things are Entomology –
passed from one study of insects and the
generation to impact they have on
the next human lives

Biotechnology – Physiology –
study of the use of study of how living
biological processes things and their
in research, industry, Anatomy –
different parts function.
agriculture and study of the physical Histology –
Bacteriology – Physiology explains how
waste management structure of living study of tissues
study of bacteria all the systems of the
things
body
work together
Figure 1.3: Branches of Biology

Unit 1: Introduction to Biology 3

 Self assessment 1.1
1. What does the word ‘Biology’ mean?
2. Name at least three branches of Biology, and explain what is studied in each branch.
3. Read the following case study and tell to your classmate or parents the key message from it.
Careers in Biology
There are many interesting careers related to different aspects of Biology that you can follow after you leave
school. A degree in biological sciences or a diploma in a biology-related field will enable you to work in
many different jobs.
For example, biomedical science is the field of biology that has medical applications. Health workers and
research workers often have a degree or diploma in this field. Biomedical scientists carry out different tests
to identify diseases. They also are involved in finding ways to improve peoples’ health.
Biological and biomedical scientists can work in hospital laboratories, blood banks, veterinary laboratories
and pharmaceutical companies. They can also work to save endangered plants and animals and help to
protect our environment from human impacts. There are even biological scientists on the International
Space Station!

1.2. Importance of studying biology

Activity 1.2

Read the case study, and then answer the questions.

Why do we study Biology?
Biology is the study of living organisms in their environments on planet Earth. Since we ourselves are
living organisms and we are surrounded by other living organisms, biology is an important subject in
schools. It is divided into many different branches. For example, zoology is the study of animals, botany
is the study of plants and ecology is the study of living organisms and their environment.
The study of many aspects of biology helps humans in their daily lives. Botanists have helped us to classify
plants and appreciate their diversity. We understand their value in medicine, food crops and as shelter for
both humans and other animals.
Animal biology and zoology, is important so that we can realise the value of animals. Animals provide
us with many resources such as honey, meat, milk and materials for clothing. Biologists also study the
interaction between living organisms and their impact on the environment. Maintaining the balance
between organisms and Earth is vital for the existence of humans on our planet in the future.
Source: N Ranga Reddy, http://www.rajaha.com/importance-biology

Questions
1. List four resources that humans get from plants.
2. Find out what the word ‘diversity’ means, and then explain it in your own words.
3. Which group of organisms is the greatest source of medicines?
4. Name any two plants and two animals that are used in Rwanda as food for humans.
5. The case study does not mention one very important group of organisms that can impact on human
health. Which organisms would be in this group?

4 Topic 1: Biodiversity and classification

Biology is a science that is growing and developing quickly in the 21st century. Scientists who study Biology
are known as biologists. There are many reasons why we study Biology.
● It improves our understanding of diseases and their causes, prevention and treatment.
● It helps us to meet the needs of a growing population; for example, through increased food production.
● We can understand the variety of living organisms on Earth, and why we need to look after all of them.
● We can appreciate how all life on Earth is connected.
● It helps us make decisions about our own health and form our opinions on controversial issues, such as
organ donation.
● It can provide us with career opportunities.

Figure 1.4: Scientists work in different fields of Biology to improve our lives.

Self Assessment 1.2

1. Explain why the study of ecology is important to both human beings and planet Earth.
2. Write down six reasons why people study Biology. Use your own words.
3. Imagine that a team of biologists is studying the impact of pollution on a forest. Which specialists do
you think would be in the team?

Unit 1: Introduction to Biology 5

1.3. Characteristics of living things
Activity 1.3

1. Look at the picture, and write down all the characteristics of living organisms that you can see.

2. Imagine some living things in your family or school garden. What do you consider to decide that
such things are living things?

Scientists use main characteristics to decide whether something is living or not. A characteristic is something
that an object or organism can do. For example, many animals move. So, movement is one characteristic of
living things. Table 1.1 on the next page shows the seven characteristics of living organisms. We think of
something as being alive only when it shows all seven of these characteristics. A monitor lizard is used as an
example to help you understand.
Hint
You can remember the
main characteristics of
life, or life processes,
with the words
MRS NERG.
M – movement
R – respiration
S – sensitivity
N – nutrition
E – excretion
R – reproduction
G – growth
Figure 1.5: A monitor lizard is an example of a living organism.

6 Topic 1: Biodiversity and classification

Table 1.1 describes the main characteristics of living things.
Table 1.1. The characteristics of living things
Characteristic What it means Monitor lizard

1. Movement or All living things change position and move from The lizard can move very quickly to catch
locomotion one place to another in some way. In animals, this food, to run away from predators or to swim
is easy to see. There are some parts of plants that in water.
move to get more sunlight, for example.
2. Respiration Respiration is a chemical reaction that takes place The lizard breathes in air, which contains
inside all living cells in an organism. During oxygen. Oxygen is transported in the blood
respiration, food is broken down to produce energy to the cells of the body, where respiration
that the organism can use. Oxygen is needed for reactions take place. Respiration reactions
the process to happen. Carbon dioxide is produced use oxygen and nutrients, such as glucose, in
during the respiratory process. the cells to make energy.
3. Sensitivity or All living things need to be able to respond to The lizards has eyes, a nose and ears. It
irritability changes in their environment so that they can, for uses these to pick up changes around it and
example, find food or seek shelter. respond to the changes.
4. Nutrition or All living things need to get energy to live. They The lizard eats small insects to get enough
feeding get their energy from food, or nutrients. Different energy to stay alive. Through the process of
organisms get food in different ways. Animals eat digestion, the nutrients inside the lizard’s
plants or other animals, or both. Plants use the food are slowly broken down until they are
energy from the Sun to make their own food, in a small enough to travel in the blood to the
process called photosynthesis. cells of the body.
5. Excretion Excretion is the process that gets rid of waste from The lizard produces carbon dioxide during
the body of a living thing. If these waste materials respiration. This gas is excreted when the
are not removed, they will become toxic to the lizard breathes out.
body.
6. Reproduction All living organisms must have offspring if they The lizard lays eggs that hatch, and baby
are to survive as a species on Earth. monitor lizards are produced.

7. Growth or All living things grow. The lizard hatches from an egg and then
development grows bigger.

Self assessment 1.3

1. What are the common characteristics between plants and animals? Explain on each characteristic.

Unit 1: Introduction to Biology 7

1.4. Safety rules and regulations
Activity 1.4

1. Identify the hazards shown in Figure 1.6. Why these are hazards.

Figure 1.6: Hazards in the laboratory.

2. Discuss other hazards that can be found in a laboratory besides those you identified in Figure 1.6.
3. List all the safety precautions that you will take, when you are in a laboratory?

Biology, like other science subjects, involves practical work that can be done in a laboratory, in a classroom,
or outside the classroom.
You will use a variety of materials, chemicals, pieces of apparatus and equipment. You will also use animals
and plants. To prevent accidents from happening when we work with these different items, we must take
certain safety precautions.

8 Topic 1: Biodiversity and classification

 Homework
Safety rules
1. on
Work Follow instructions.
your own and as a class.
2. Consider the safety of other learners during practical work.
3. Do not work in the laboratory when your teacher is not present.
4. Do only practical work that has been assigned to you by your teacher.
5. Do not use any chemical until your teacher has explained its use and the precautions
you must take when using it.
6. Do not touch apparatus on the demonstration table without instructions from your
teacher.
7. Know where fire extinguishers and first aid materials are stored, and find out how to
use them.
8. Always be careful when pouring chemicals from their containers. If you spill a
chemical, report it to your teacher.
9. Immediately wash off chemicals that get into the eye or onto the skin using running
water.
10. Never look into a test tube or point its mouth in the direction of other learners when
you heat liquids in the test tube.
11. Close gas burners tightly after use.
12. Ensure that the laboratory is well ventilated when you work in it.
13. Wear an apron and safety glasses whenever necessary.
14. Do not use a flame when you work with volatile or inflammable liquids, such as alcohol.
15. Only your teacher should handle large storage bottles that contain dangerous
chemicals.
16. Never pour a chemical back into its bottle or exchange the stoppers of bottles, because
contamination could result in dangerous reactions.
17. Never force glass tubing, thermometers or any breakable materials in or out of rubber
stoppers and tubing. Use glycerine as a lubricant, and not water.
18. Laboratory animals, whether living or dead, should be handled only with instructions
from your teacher.
19. Dispose of solid waste, broken glass and other laboratory waste in their specific containers.
20. Clean and dry laboratory work areas and equipment before the end of class.
21. Do not taste, eat or drink any laboratory materials without instructions from your teacher.
22. Do not touch any electrical device that has just been used, to avoid burns.
23. Report any broken glassware to your teacher.
24. Use sharp instruments with great care.
25. Wash your hands with soap after handling unknown plants or substances.
26. Make sure that you are safe from animals such as snakes, scorpions and wasps when
you do field work.
27. Report any accident or injury to your teacher.

Unit 1: Introduction to Biology 9

 Self assessment 1.4
1. Think of some safety rules that you must follow when doing practical work in the laboratory and
outside the laboratory.
2. Make a poster that you can dicuss in class.

1.5. First aid and the first aid kit

Activity 1.5

1. Look at the list of safety rules on previous page, and then make a list of injuries that could result if
these rules are not followed.
2. Based on your list of injuries, think of first aid equipment that should be kept in the school
laboratory.

There are many hazards in the laboratory; for example, chemicals, sharp objects, glass apparatus and
gas burners. Learners do not need to be trained in first aid, as one of your teachers will be trained. It is
important that there is a first aid kit available, in case someone is injured in the laboratory. The following
figure shows the components of the laboratory first aid kit.

Figure 1.7: A laboratory first aid kit

What to do if someone is injured in the laboratory
Follow the instructions given in Table 1.2 for dealing with common types of injury in the laboratory.
Table 1.2. Treating injuries in the laboratory
Injury Instructions
Heat burn • Cool the burnt area by holding it under cool running water or water in a basin, until the pain lessens
• Cover the burn with a sterile, non-stick bandage or clean cloth
• Give the person pain relief
• Go to a clinic or doctor
Chemical • Put on gloves and protective clothing to avoid exposing yourself to the chemical
burn • Flood the burnt area using cool water for at least 20 minutes, making sure that the water does not
touch your own skin
• Do not try to neutralise the burn using another chemical
• Cover a small burn with a dry sterile cloth or bandage

10 Topic 1: Biodiversity and classification

 Cut • Stop the bleeding by applying direct pressure on the area
• Clean the area using warm water
• Apply antiseptic ointment
• Cover the cut with a sterile bandage or non-stick plaster
• If the cut is deep, go to a clinic or doctor
Chemical • Remove any contact lenses immediately
in the eye • Flush the eye immediately using cool water, and continue for about 15 minutes
• Go to a clinic or doctor
Object in • Wash your hands with soap and water to prevent infection
the eye • Flush out the eye using water
• Gently pull the upper eyelid over the lower one. This causes tears to form, which may flush out the
object
• If you can see the object, you may be able to use a clean cloth to gently wipe away the object
• If the object cannot be removed, go to a clinic or doctor

Figure 1.8: Hold the burnt area under cool water Figure 1.9: Use water to flush out an object in a person’s eye.

Self assessment 1.5

1. Make a list of all the items in the first aid kit in your school’s laboratory.
2. Work out what each item is used for.
3. Are there items that you think should be included in the first aid kit that are missing?

Unit 1: Introduction to Biology 11

Checklist of learning (Unit Summary)
In this unit, I have learnt:

Biology is the study of life.

There are many branches of Biology, for example, botany, zoology, microbiology and genetics.
People study Biology for various reasons, but mainly to understand and to improve the quality of life
on Earth.
All living organisms have seven characteristics that make them ‘living’: movement, respiration,
sensitivity, nutrition, excretion, reproduction and growth (MRS NERG).
When you work in a laboratory, it is important to follow safety rules to prevent injury.
There should be a first aid kit in the laboratory that contains all the necessary items to treat injuries
that may occur.
First aid should be given if someone is hurt in the school laboratory, and a teacher trained in first aid
should be available to give assistance.

End unit assessment

1. Look at the pictures, and then write down which characteristic of life each one shows.

a. b. c.

d.

12 Topic 1: Biodiversity and classification

2. Match the description in Column A with the correct term in Column B.
Column A Column B
2.1 Toxic A. Excretion
2.2 Making energy from the Sun’s energy, B. Poisonous
carbon dioxide and water in plants

2.3 Getting rid of waste substances C. Variety of living organisms

2.4 Responding to the environment D. Respiration
2.5 Using food molecules and oxygen to E. Photosynthesis
get energy

2.6 Biodiversity F. Reproduction

2.7 Producing offspring G. Sensitivity
3. If you spill a chemical on a laboratory bench, what is the first thing that you should do?
4. Describe the treatment you would give to a learner who has cut himself or herself.
5. Choose one of the common types of injury in the laboratory. Prepare a role-play to show the treatment
of the injury, and then present it to the class. Discuss with your colleagues what was good about your
role-play and also which aspects could have been done better.

Unit 1: Introduction to Biology 13

 UNIT 2 Introduction to classification

Key unit At the end of this unit, I should be able to:

competence • Explain why we need to classify living organisms
To be able to explain
• Name the five kingdom system of classification
• Name the characteristics of the organisms making up the five kingdoms
the need for, and apply • Apply the binomial system of naming species
classification and use • Compare living and non-living things and explain their differences
identification keys • Explain hierarchical classification
to name unknown • Explain how organisms are grouped together into different taxonomic categories
specimens. • Use simple identification keys to identify given organisms
• Appreciate the need for classification of organisms.

Introductory activity
Observe carefully the living things below and answer the following questions:
Fungi Animals Plants

Monera

Yeast

Protoctista

Figure 2.1: Main groups of living things.

1. How do we know that something is living?
2. Make a guess about the number of different animals and plants in Rwanda. Do you think it is a large
number or a small number?
3. Think of ways in which you could put these organisms into groups.
4. Do you know the scientific name for some of these organisms?

14 Topic 1: Biodiversity and classification

2.1. The importance of classification
Activity 2.1

Look at the pictures below, and then answer the questions.

Figure 2.2: Living and non-living things

1. Draw a table with two columns. In one column, write down all the living things that you can see in the
picture. In the other column, write down all the non-living things.
2. How did you decide which things were living and which were not?
3. Of the non-living things:
a) Which were always dead?
b) Which were once alive, but are now dead?
4. Draw another table with two columns. In one column, write down the names of all the animals you
can see in the picture. In the other column, write down the names of all the plants.
5. How did you decide which things were animals and which were plants?

In the introductory activity, you talked about how many different organisms there are in Rwanda. No doubt
you realised that there are a large number of different living things in our country. In fact, there are more
than 2,000 different types of plants and 500 different types of animals in our country.
Scientists need to sort all living things into groups so that they can recognise and study them more easily. When
you were sorting the living things into plants and animals in the activity, you were classifying them. There
are so many different organisms on Earth that scientists need to sort them into groups. Classification means
sorting things into groups. Think back to how you sorted the living things. You put those that shared certain
characteristics into the animal group, and those that shared certain other characteristics into the plant group.
Sorting, or classifying, things into groups according to their similarities and differences is called classification,
or taxonomy.
Scientists sometimes change the way they classify an organism as they
learn more about it. Taxonomists use information from many branches of Biology to classify organisms; for
example, genetics, biochemistry and fossils.
Self assessment 2.1
1. Why is it necessary to group organisms?
2. What do the scientists consider to do the taxonomy of oganisms?

Unit 2: Introduction to classification 15

2.2. The concept of hierarchical classification
Activity 2.2

By considering the area of administrative entities in Rwanda like village, cell, sector, district, province and
country and by estimating the number of people in each administrative entity in Rwanda:
1. Which administrative entity has:
a)The largest number of people
b) The smallest number of people
2. How can you compare this with hierarchy of classification?

In Activity 2.1, you grouped different living organisms into two groups:
animals and plants. However, there are thousands of different organisms
in these two groups, so scientists must classify them into smaller groups.
Taxonomists study more similarities and differences between different
organisms so that they can classify them into smaller and smaller groups.
This is called hierarchical classification.
Self assessment 2.2
1. Arrange the classification groups below into the correct order. Start with the group that contains the
smallest number of organisms.
family species order genus phylum kingdom class
2. There are many organisms on earth. How difficult is to put in their hierarchical classes?

2.3. The binomial system

Activity 2.3

By using internet and textbooks, search and explain the nomenclature by binomial system and explain
how to write a scientific name of an organism.

Usually, we use an organism’s common name, for example, ‘cat’. However, the
word for ‘cat’ is different in different languages. So, people in different parts
of the world use different words to describe the same organism. This makes
it difficult for scientists to accurately communicate their findings about an
organism accurately.
To solve this problem, the biologist Linnaeus developed a system accurately
give an organism two Latin names. Using two names is called the binomial
system. The first word in the name is the genus to which the organism
belongs. So for a cat, this would be Felis. The second name is the species to
which the organism belongs. A species is a group of closely related organisms
that are able to breed with one another and produce offspring that can also
reproduce. The species name for a cat is domesticus. So the scientific name
for a domestic cat is Felis domesticus. Figure 2.5: Yellow commelina,
or Commelina africana

16 Topic 1: Biodiversity and classification

Let us look at another example, one from the plant kingdom. Yellow commelina
is a plant found commonly in Rwanda. Its scientific name is Commelina
africana. The name Commelina is its genus name. All commelina plants have
the same genus name. The africana part of the name is the species name. Only
one kind of commelina plant has the species name. So Commelina africana is
the scientific name for a particular kind, or species, of commelina plant.
How to write scientific names
A
Look again at the scientific names you have learnt about in this unit: Ficus
  
carica, Felis domesticus and Commelina africana. What do you notice about
how they are written?
B
• The first name is the name of the genus the organism belongs to; it starts
with a capital letter.   Ficus carica
• The second name is the name of the species the organism belongs to; it
starts with a small letter. Figure 2.6: A scientific name
• When written by hand, the two names must be underlined separately; written by hand (A), and the
when they are printed, they must be in italics. See Figure 2.6. same name in print (B)

Self assessment 2.3

1. Give the correct name or word for each of the following:
a) the biologist who developed the binomial system
b) the naming and classification of organisms.
2. Match each animal’s common name with its scientific name. To help you, here are some Latin words
translated into English:mel = honey; taurus = bull; terra = earth; sapiens = wise
Common name Scientific name
2.1 Earthworm A. Homo sapiens
2.2 Honeybee B. Bos taurus
2.3 Rhinoceros C. Panthera leo
2.4 Cow D. Apis mellifera
2.5 Hippopotamus E. Diceros bicornis
2.6 Lion F. Lumbricus terrestris
2.7 Human G. Hippopotamus amphibius

2.4. The five kingdom system

Organisms are grouped into five big groups, called kingdoms. The kingdoms
are Animals, Plants, Fungi, Protoctista and Monera.
The features that are used to group organisms into these kingdoms are: body
structure, method of getting food and method of reproduction.
The kingdoms are further divided into smaller groups called phyla, classes,
orders, families, genera and species. See Figure 2.3.

Unit 2: Introduction to classification 17

• Each kingdom is divided into phyla.
• Each phylum is divided into classes.
• Each class is divided into orders.
Hint
• Each order is divided into families.
• Each family is divided into genera. You can remember
• Each genus is divided into species. the groups with this
sentence: King Phillip
came over for great
Kingdom Contains spaghetti (K–P–C–O–
Phylum many different F–G–S).
organisms
Class

Order

Family
Contains only
Genus closely related
organisms
Species

Figure 2.3: A kingdom is made up of smaller groups.

The diagram below shows two classification hierarchies. A hierarchy is a way
of arranging groups from the biggest group to the smallest. The first is for a
fig tree and the second is for a cat.

A
Kingdom Plantae

Spermatophyta /Angiospematophyta
Phylum

Class Dicotyledonous

Order Urticala

Family Moraceae

Genus Ficus

Species carica

Scientific
Ficus carica
name

18 Topic 1: Biodiversity and classification

 B
Kingdom Animalia

Phylum Chordata

Mammalia
Class

Carnivora
Order

Felidae
Family

Felis
Genus

Species domesticus

Scientific
name Felis domesticus

Figure 2.4 The classification hierarchy for a fig tree (A) and a cat (B)

Characteristics of organisms in the five kingdoms

Table 2.2 shows characteristics and examples of organisms in each kingdom.
Table 2.2. Characteristics of organisms in the five kingdoms
Kingdom Characteristics Examples
Animalia • The organisms’ cells do not have a cell wall. Snail, mosquito, snake, bird
• The organisms are multicellular, feed on other organisms, and move
around.
• They are heterotrophic oranisms
• Most animals have ability to move from one place
• Their reproduction is mainly sexual by fusion of a sperm and egg.

forest cobra
Plantae • The organisms’ cells have a cell wall. Moss, fern, maize, fig tree
• The organisms contain a green substance called chlorophyll and make
their own food through photosynthesis.

fern

Unit 2: Introduction to classification 19

Fungi • The organisms reproduce by means of spores and not seeds. Toadstool, mould, yeas
• The organisms do not photosynthesise.
• Some are unicellular (yeast) others are multicellular (rhizopus,
penicillium,...)
• They have cell wall made up of substance called chitin.
toadstool
Protoctista • The organisms are single cells or colonies of single cells. Amoeba, paramecium
• They are euraryotes (have a true nucleus surrounded by a nucleus
membrane)

paramecia
Monera • The organisms are single cells that do not have a membrane-bound Bacterium
nucleus; they are prokaryotic.
• They are the smallest and simplest of all organisms.
• Most reproduce by binary fusion.

bacteria

Self assessment 2.4

1. Name the five kingdoms of organisms.
2. Identify the kingdom to which each of the organisms described belongs.
a) It has a cell wall and chloroplasts.
b) It is a single cell.
c) It reproduces by means of spores.
3. Copy the table, and then complete it by putting the following animals into their correct groups: buffalo,
earthworm, hyena, hare, cheetah, jellyfish, lynx. (Hint: all the animals belong to one group, but only
some belong to other groups, too.)
Kingdom Animalia

Phylum Chordata

Class Mammalia

Order Carnivora

Family Felidae (cats)

20 Topic 1: Biodiversity and classification

2.5. Use simple identification keys
Activity 2.5

Look at pictures A to D alongside, and read the example of a dichotomous A

key. Then, answer the questions.

Example of a dichotomous key

We can identify the animals A, B, C and D by using a dichotomous key
like this one:
(i) Has legs ________________________ See (ii)
Has no legs ____________________ Snake
(ii) Has two legs _________________ Chicken B
Has more than two legs __________ See (iii)
(iii) Has six legs _________________ Grasshopper
Has eight legs _________________ Spider
1. The key has three steps. Each step has a pair of statements which
describe the animals. Notice that each pair of statements in the key
divides the animals into two groups. What characteristic is used in
this key to group and identify the animals?
2. Step 1 of the key separates the animals that have legs (A, B and C)
from those that do not have legs (D). The first statement in Step 1 says
that if the animal has legs, we should move on to Step 2. The second
statement says that if the animal has no legs, it is a snake. Therefore C
animal D is identified as a snake.
3. Read Step 2 of the key. The first statement says that if the animal
has two legs, it is a chicken. Of the three remaining animals (A, B
and C), only B has two legs. Therefore, animal B is a chicken. This
leaves two animals (A and C), which have more than two legs.
The second statement tells us to go on to Step 3 to identify these
two animals.
4. Step 3 identifies an animal with six legs as a grasshopper. Therefore,
animal C is a grasshopper. Using the second statement in Step 3, can D
you identify animal A?
5. Your teacher will display some specimens or pictures of different
organisms in the classroom. Identify their observable characteristics,
and then try to make a dichotomous key using their characteristics so
that someone else could identify them.

Scientists use identification keys to help them to identify unknown organisms. A key is a list of characteristics.
Scientists compare the characteristics of the unknown organism with the descriptions on the key, and so can
classify the organism. You will use a dichotomous key in the next activity (‘di’ means ‘two’). A dichotomous
key consists of pairs of statements about a characteristic of a particular organism.

Unit 2: Introduction to classification 21

Checklist of learning (Unit summary)
In this unit, I have learnt:

There are many different organisms on Earth, and scientists classify them into groups.
There are five groups, called kingdoms, which each have many organisms; the kingdoms are:
Animalia, Plantae, Fungi, Protoctista and Monera.
The kingdoms are further divided into smaller and smaller groups; this is called hierarchical
classification.
The groups in the kingdoms are: phyla, classes, orders, families, genera and species.
Organisms have two names in the binomial system: a genus name and a species name.
Animals have cells without a cell wall, are multicellular, can move around, and feed on other
organisms.
Plants have cells with cell walls, contain chlorophyll and can make their own food through
photosynthesis.
Fungi reproduce by spores instead of seeds and do not photosynthesise.
Protoctista are single-celled organisms.
Monera are single cells without a membrane-bound nucleus.
To appreciate the need for classification of organisms.

End unit assessment

1. The group of classification where organisms resemble one another and are capable of interbreeding
together to produce viable offspring is known as:
a) Species
b) kingdom
c) Genus
d) Phylum
2. Which one of the following is not a kingdom of living organisms?
a) Monera
b) Animalia
c) Annelida
d) Protoctista
3. The following is a list of organisms belonging to various kingdoms: housefly (Musca domestica),
maize (Zea mays), Frog (Rana spp), Bat and Eagle.
a) Classify these organisms into their kingdoms
b) Name any two organisms that are not closely related and give a reason.
c) What does the name mays represent?
d) Define the term species
4. How are fungi different from members of kingdom plantae?

22 Topic 1: Biodiversity and classification

5. Copy the table, and then complete it by putting the following animals into their correct groups: cow,
perch, locust, lion, donkey, leopard.
(Hint: all the animals belong to one group, but only some belong to other groups, too.)

Kingdom Animalia

Phylum Chordata

Class Mammalia

Order Carnivora

Family Felidae (cats)

6. The figure below shows four animals: A, B, C and D.

a) Construct a dichotomous key that can be used to identify the animals.

A.

B.

D.

C.
b) Discuss the dichotomous keys that you constructed.

Unit 2: Introduction to classification 23

 The external structure and
UNIT 3 importance of flowering plants

At the end of this unit, I should be able to:

• Identify the external parts of a flowering plant
• Describe how plant organs are organized into systems
• Explain the functions of roots, stem and leaves in plants
Key unit competence • Identify different root, stem, and leaf modifications
• Describe the external structural modifications shown by roots, stem and leaves
To be able to analyse • Explain the importance of flowering plants
the external structure • Differentiate flowering plants from other plants
of a typical flowering • Observe the external structure of leaves and root modifications and how
plant they carry out other functions
• Explain the difference between fibrous and tap root systems
• Carry out home observation on the importance of flowering plants and submit a
report
• Appreciate the importance of food storage organs in plants and the value
of roots and leaves to man.

Introductory activity
1. In unit 1, you have seen that plants are not able to move from one place to another. In your groups,
choose one of the plants in school garden and observe its structure that cause inability for the plant to
move. What are parts of the plant that help it to survive though it cannot move for running after food
and water.
2. Describe how some plants, such as avocado, maize and cassava reproduce?

A B C

Figure 3.1: The flowering plants maize (A), sorghum (B) and cassava (C) are important food crops

24 Topic 1: Biodiversity and classification

3.1. The external structure of a flowering plant
Activity 3.1

Work out the following:

From your school garden, take a typical dicotyledonous plant with roots, e.g. a bean plant or black jack;.
Your will need a hand lens as material.
1. Identify the following parts on your flowering plant: shoot system, root system, bud, node, internode,
leaves, stem, flowers, fruits, roots. Use Figure 3.2, to help you.
2. Note the main features of the stem and root.
3. Make a large drawing of your plant specimen, showing all the parts you have identified. Label the
diagram carefully.

Flowering plants are a large group of plants and trees.

They all have flowers, bear fruit and produce seeds. flower
They are organisms that are made up of different
organs, which are called stems, leaves, flowers and bud
roots.
node
Monocotyledonous and dicotyledonous internode
leaf
plants shoot system shoot

stem
There are two main types of flowering plants:
monocotyledonous and dicotyledonous plants. All lateral roots
flowering plants have seeds with cotyledons, or seed
leaves. Some plants have just one cotyledon and others
have two. Table 3.1 shows the main differences between
these two groups.
Table 3.1. Differences between monocotyledonous
and dicotyledonous plants
tap root
Monocotyledons Dicotyledons root system

One seed leaf, or Two seed leaves, or

cotyledon cotyledons
Fibrous roots Tap root
Flower parts are in Flower parts are in Figure 3.2: A generalised flowering plant
multiples of three multiples of four or five
Narrow leaves with Leaves with a net-like
parallel veins pattern of veins
Examples: grasses and Examples: mangoes,
cereal plants, such as avocados, beans and figs
maize and sorghum

Unit 3: The external structure and importance of flowering plants 25

 A a) The stem
The stem is the part of a flowering plant that usually grows above the ground.
A stem has buds and side shoots, and bears leaves. Most stems are green as
they contain chlorophyll.
The place where a leaf grows from a stem is called a node. The length of a
stem between the leaves is called an internode.
Functions of the stem
The stem:
runner (stolon) • transports water and mineral salts from the roots to other parts of the
plant
• transports sugars (food) from the leaves to all other parts of
the plant
B • supports and holds buds and leaves so that they can get enough
sunlight for photosynthesis
• holds flowers in the best position for pollination
• supports the fruits and seeds in the best position for dispersal
• makes food for the plant through the process of photosynthesis.
Modified stems
Most stems have similar functions, but some stems are modified so they can
do other jobs. Modified stems have features that help them to do a particular
job. For example, some stems can be modified for asexual reproduction.
rhizome Plants with such stems can make new plants using their modified stems. The
stems can produce small, identical new plants at their ends, or roots can form
C where a stem touches the ground, and a new plant can grow from there.
For example, in strawberries, bananas and sisal, suckers and stolons can be
used to make new plants.
Some stems are modified for food storage, for example, ginger, potatoes,
stem
yams and strawberries. Figure 3.3, on page 28 shows some modified stems.
tuber

Experiment 3.1
Work on your own.
D You will need: specimens or photographs of the following: a rhizome of
ginger, a canna lily, couch grass or potato; a creeping stem of oxalis; a corm
of coco yam; a stolon of a strawberry; a hand lens
corm Procedure
1. Examine the different types of stems provided. Note the main features
of each stem.
2. Suggest the function of each stem and note how it is suited to its
Figure 3.3: Examples of function.
modified stems: strawberry (A), 3. Make a drawing of each different stem type, and label the drawings
ginger (B), potato (C), yam (D) carefully.

26 Topic 1: Biodiversity and classification

b) Leaves
apex
Leaves are attached to a plant’s stem at the nodes by a stalk called a petiole (see
Figure 3.4). Leaves are usually thin, wide and flat in shape. The wide, flat area
midrib
of a leaf is called the lamina. Leaves are the main organs of photosynthesis. veins
margin
Leaves are green because their cells contain a lot of chlorophyll, to capture
the sunlight that falls on the leaf. lamina
The structure of a leaf is closely related to the job it has to do for the plant.
The thin, flat lamina means that leaves have a large surface area. Carbon petiole
dioxide can easily get into the leaf. The large surface area can also trap lots of
sunlight for photosynthesis. Leaves have a system of veins which bring water Figure 3.4: The generalised
and minerals to the cells and carry away the sugar made by photosynthesis. structure of a leaf
The main vein, which connects with the petiole, is called the midrib.
The top layer of a leaf is covered by a waxy waterproof layer called
the cuticle. The cuticle prevents water loss through the surface of
the leaf.
The arrangement of the veins on a leaf can vary a lot. The veins of a
monocotyledonous plant run in parallel lines. The leaves of a dicotyledonous
plant have a network of branching veins.
The size and shape of leaves can also vary (see Figure 3.5). Leaves can be split
into several parts or have smooth, toothed or lobed edges (margins). Many
of these features help us to identify different types of plants.

simple leaf with

toothed margin simple leaf
simple palmate leaf

compound trifoliate leaf compound

bipinnate leaf simple leaf with
compound pinnate leaf
lobed margin

Figure 3.5: Leaves can have different shapes and sizes.

Unit 3: The external structure and importance of flowering plants 27

Functions of leaf parts
Table 3.2 describes the functions of the different parts of the leaf.
Table 3.2. Parts of the leaf and their functions
Part Function

Petiole • Carries food made by photosynthesis from the leaf to

the stem
• Transports mineral salts and water from the stem to
the leaf
• Supports the leaf
Midrib • Supports the lamina
• Carries water and mineral salts from the petiole
to the lamina
• Transports food from the lamina to the petiole A
Veins • Support the lamina
• Distribute water and mineral salts within the lamina
• Collect food from the lamina
Lamina • Contains chlorophyll for trapping light energy, which
is needed for photosynthesis
B
Modified leaves
As with stems, some leaves are modified for different functions. Some of the
most common modifications enable the plant to:
• Prevent animals from eating the plant. Such leaves are usually prickly,
poisonous or have an unpleasant taste.
• Prevent water loss. These leaves often have a thick, shiny, waxy layer on
their surface. They may be reduced to spines (e.g. a cactus), or be covered
with a layer of tiny hairs. Some leaves are curled up to prevent water
leaving the leaves.
• Store water. These leaves are fleshy and used to store water.
• Store food; examples include onion and garlic.
C

Exercise
Work out the following:
1. Collect at least three different types of leaves.
2. Draw a table to show the differences between the leaves.
3. Make a labelled drawing of any one of the leaves, showing its main
parts.

Figure 3.6: Examples of leaf

modifications: a cactus (A),
onion (B) and succulent (C)

28 Topic 1: Biodiversity and classification

Leaf arrangement on the stem (phyllotaxis) and leaf venation
In botany, phyllotaxis or phyllotaxy is the arrangement of the leaves on the stem of a plant.
Types of leaf arrangement
1. Opposite leaf arrangement
In this case, two leaves grow in opposite directions from the same nodes.
If successive leaf pairs are perpendicular, this is called decussate.
2. Alternate leaf arrangement
Alternate leaf arrangement means that each leaf grows at a single node.
3. A whorled leaf arrangement
It consists of three or more leaves at each node.
A whorled leaf pattern/arrangement can occur as a basal structure where all the leaves are attached at the
base of the shoot and the internodes are small or non existent

Venation
This is the arrangement of veins in the leaf. There are two types of venation:
(i)Reticulate venation: the veins are arranged in a network (E.g.: Dicot plants)
(ii)Parallel venation: there are several main veins running parallel to one another and connected by short
cross branches (E.g.: grass, maize or other monocot plants)

Unit 3: The external structure and importance of flowering plants 29

c) Flowers anther: the pollen is made here; the anther ripens and splits
Flowers are the reproductive open and then the pollen is released
organs of a plant. Some flowers petal
form individually on stems, whilst stigma: receives the stamen
others are arranged in clusters. pollen
An arrangement of flowers on a filament
stem is called an inflorescence.
Figure 3.7 shows the main parts style: connects the
of a flower. Flowers produce the carpel stigma to the ovary sepal
male and female sex cells, which
are called gametes. The female receptacle nectary
sex cells are inside the ovules. The ovary: the ovules are
made and fertilised here
male sex cells are inside the pollen
gains.
Figure 3.7: The structure of a flower
Experiment 3.2
Work in groups. Complete the experiment, and then answer the questions.
You will need: a razor blade; a hand lens; a large flower such as hibiscus; a grass flower
Procedure
1. Compare the characteristics of both flowers.
2. Carefully dissect the hibiscus flower to observe all its parts.
Questions
1. Explain why some parts of a flower are brightly coloured.
2. Name at least eight parts that you saw on the hibiscus flower.
3. Make a labelled drawing to show the main parts of a flower.

Self assessment 3.1

1. Suggest the functions of all the plant parts you identified in activity 3.1.
2. Explain why potatoes, sweet potatoes and carrots are called tubers.
3. What makes a potato a stem and not a root?
4. Give two functions that different types of modified stems can
carry out.
5. Give the meaning of each of these terms.
a) petiole
b) pollination
c) monocotyledon
6. a) List the functions of leaves.
b) Describe two ways in which leaves are suited to their functions.
7. A plant has a tap root, two cotyledons and a flower with eight petals. Is this a monocotyledonous or
a dicotyledonous plant?

30 Topic 1: Biodiversity and classification

3.2. The external structure of a root system
Activity 3.2

Work out the following:

You will need: specimens or photographs of the following: a bean plant, an onion, couch grass or a maize
plant, a carrot; a hand lens
Procedure
Use the hand lens to observe the different types of root systems in the specimens.
Questions
1. Suggest two functions of roots.
2. a) Draw and label the parts of the bean plant’s root system.
b) What is the function of each part labelled?
3. Identity the type of root for each plant.
4. a) What root modifications can you see?
b) What are the functions of modified roots?

The root system of a flowering plant develops from the radicle of the embryo A
in the seed. Most roots are white, cream or brown in colour. They do not
contain chlorophyll and so cannot photosynthesise.
There are two main types of root systems.
• A tap root system consists of a single main root with smaller lateral, or side,
roots branching from it. Tap root systems are found in dicotyledonous
plants, for example black jack, carrot and bean. See Figure 3.8A.
• A fibrous root system is made up of many roots that grow from one
point and that have side roots branching from them. Monocotyledonous
plants, such as maize and elephant grass, have a fibrous root system. See
Figure 3.8B. Figure 3.8. A: Root
Functions of roots systems: a tap root
B
The main functions of roots are to:
• hold the plant firmly in the soil
• absorb water and minerals from the soil
• transport water and minerals to the stem.
Modified roots
Roots can also be modified to carry out other functions. While most roots are
underground, sometimes roots grow above the ground for extra support, for
example maize and sugarcane. These are called prop roots. Aerial roots grow Figure 3.8. B: Fibrous root
above the ground and are used for gaseous exchange. This is the exchange
of oxygen and carbon dioxide between the inside and outside of the root.
Many plants that grow in mangroves have aerial roots. Prop roots can grow
from aerial roots to give the plant extra support; for example, maize and

Unit 3: The external structure and importance of flowering plants 31

sugarcane. Some plants have roots that are used for food storage; for example, carrot and sweet potato.
Some modified roots enable the plant to reproduce asexually. Examples include sweet potato and cassava.
A B C D

storage
root

aerial roots of a mangrove prop roots

sugarcane carrot Clasping root
E F G

Buttress root Breathing root Stilt root

Figure 3.9: Examples of modified roots: aerial roots (A), prop roots (B), a storage root (C), clasping root (D), buttress root
(E), breathing root (F) and stilt root (G)

Self assessment 3.2

1. Work out the following:
You will need: specimens or photographs of the following: prop roots of maize or sugarcane;
clasping roots of vanilla; aerial roots of Ficus; buttress roots of flamboyant tree; breathing
roots of white mangrove; stilt roots of red mangrove; storage root of carrot or sweet potato;
a hand lens
Procedure
a. Examine the roots of your specimens, and then make a list of all the root modifications you can see.
b. Describe the main features of each root.
c. Describe how each root type is suited for its functions.
d. Make labelled drawings of the different root types.
2. Collect at least four plants with different types of root systems.What type of root system does each
plant have?

32 Topic 1: Biodiversity and classification

3.3. The importance of flowering plants
Activity 3.3

1. List the importance of flowering plants in your own home and community.
2. Try to find examples of plants in Rwanda that their flowers are used with economic purpose?
3. Research the growing of plants using hydroponics. Find out how this practice works, and explore its
advantages and disadvantages.

Flowering plants are important for the following reasons.

• They are a food source for many organisms.
• Plants help to maintain a balance of gases in the atmosphere. They remove carbon dioxide from the air,
and release oxygen into it during photosynthesis.
• They are important food crops for humans, for example, maize, wheat and sorghum.
• They provide shelter for many animals, such as birds and monkeys.
• Many trees are a source of timber, which is used in construction, to make furniture and for firewood.
• Some plants can be used to make medicines, for example, the quinine tree is used in anti-malarial
medicines.
• Some plants, such as cotton, can be used to make fabrics.
• Plants help to make our surroundings beautiful.

Unit 3: The external structure and importance of flowering plants 33

Checklist of learning (Unit summary)
In this unit, I have learnt:
Flowering plants have flowers, bear fruits and produce seeds.
Flowering plants consist of roots, stems, leaves and flowers.
There are two main groups of flowering plants: monocotyledons and dicotyledons.
The stem is usually green, and it is above the ground.
The stem holds the leaves and flowers in place, transports water and mineral salts to the leaves,
transports sugars from the leaves to other parts of the plant, and makes food
by photosynthesis.
Some stems are modified for asexual reproduction and food storage.
Leaves are the main organs of photosynthesis, and they are well adapted for this function.
Some leaves are modified for water and food storage, and to prevent water loss.
Flowers are the reproductive organs of flowering plants.
There are two types of root systems: tap roots and fibrous roots.
Roots hold the plant in the soil, and absorb and conduct water and mineral salts from the soil into
the plant.
Some roots are modified for food storage, extra support and asexual reproduction.
Flowering plants are important because they balance gases in the atmosphere, provide food
and shelter for animals, and are food crops; they beautify our environment and can be used in
construction, to make furniture, medicines and fabrics, and as firewood.

End unit assessment

1. Give the correct word or term for each of these descriptions.
a) the thin, flat, wide area of a leaf
b) a root system that has one main root and small lateral roots
c) plants that have their flower parts in multiples of three.
2. Draw a picture of a flower, showing all its parts.
3. Explain how a leaf is adapted to enable it to photosynthesise.
4. Name two types of root systems.
5. List three reasons why flowering plants are important.
5. Find out about biodiversity in Rwanda by researching the following:
• indigenous plants and animals in Rwanda
• the names of some endangered species in Rwanda
• the importance of conservation in Rwanda.

34 Topic 1: Biodiversity and classification

Formal assessment for topic 1
1. Identify animals A to H below by using the key.
A B

C D

E F

G H

Formal assessment 35
 KEY
1. Animal has four legs �������������������������������������������� See 3
Animal has fewer or more than four legs ��������������������������� See 2
2. Animal has two long legs ������������������������������������ Blue crane
Animal has eight legs and two pincers ��������������������������� Scorpion
3. Animal has horns ������������������������������������������ See 4
Animal does not have horns ���������������������������������� See 5
4. Horns are straight and pointed ������������������������������� Duiker
Horns are large and curved ���������������������������������� Buffalo
5. Animal is covered with fur ����������������������������������� See 6
Animal is covered with scales ����������������������� Nile monitor lizard
6. Animal has speckled fur all over its body ��������������������� Mongoose
Animal has dark fur on some parts of its body �������������������� See 7
7. Animal has dark fur on its legs �������������������������� Bat-eared fox
Animal has dark fur on its back and tail �������������� Black-backed jackal
(8)
2. What type of plant structure is each of the following?
an onion
a)  b) ginger c) cassava (3)
3. Complete the table by filling in the missing information.
Kingdom Features Example

3.1 Have many cells. Need to eat other organisms. Chimpanzee

3.2 Can photosynthesise. 3.3

Fungi 3.4 3.5

3.6 Are single-celled. Have a nucleus. Amoeba

Monera 3.7 Bacterium

(7)

4. a) Make a labelled drawing to show the structure of a flower.  (8)

b) Name two types of root systems.  (2)
c) List three reasons why flowering plants are important.  (3)
5. Find out about biodiversity in Rwanda by researching the following:
• indigenous plants and animals in Rwanda
• the names of some endangered species in Rwanda
• the importance of conservation in Rwanda.
Present your information as a poster. (14)
Total marks: 45

36 Formal assessment
TOPIC

2 Organisation and maintenance of life

Sub-topic Cell structure

Unit 4 Magnifying instruments and biological drawings
Unit 5 Plant and animal cells
Unit 6 Levels of organisation in multicellular organisms
Sub-topic Nutrition
Unit 7 Food nutrients and diet
Sub-topic Gas exchange and smoking
Unit 8 Structure and functions of human gaseous exchange
system
Sub-topic Co-ordination in plants and animals
Unit 9 Tropic responses
Sub-topic Support and locomotion
Unit 10 Skeletal systems of organisms

Figure 4.1: Cells are the simplest unit of life; we can see them by using a microscope.

37
 UNIT 4 Magnifying instruments and biological drawings

Key unit competence At the end of this unit, I should be able to:

To be able to explain • Explain why we need to use magnifying instruments

the components and • Identify a given unknown specimen
demonstrate proper • Recall that a hand lens is a simple magnifying glass for observing
use and care of a relatively small objects
hand lens and light • Identify the different components of a light microscope and explain
microscope. their functions
• Recall that microscopes are delicate instruments that need great care
• Explain that the light microscope has various levels of magnification
• List the features of a good biological drawing
• Explain that magnification is the number of times larger an image is
than the object (specimen) under the microscope
• Manipulate a hand lens to observe relatively small specimens
• Manipulate a light microscope to observe various specimens from
prepared slides
• Illustrate the biological specimens observed under a light microscope
• Illustrate well labelled biological diagrams of specimens
• Compare the relationship between the actual size of the specimen and
its image
• Measure and calculate the magnification of a given specimen
• Appreciate the need for using a light microscope and a hand lens in
observation of specimens
• Show perseverance when making scientific observations
• Show care and proper use of the magnifying instruments.

Introductory activity
Observe the figure 4.2 and answer the following questions:
1. Give two reasons why scientists need to observe things using instruments
that make these things bigger.
2. Work out a definition of the word ‘magnify’.
3. Discuss whether you have ever used a magnifying instrument.
If you have, then describe what you used it for and what you saw.

Figure 4.2: Microscopes are

important instruments for
observation.

38 Topic 2: Organisation and maintenance of life

4.1. Why do we need magnifying instruments?
Activity 4.1

Work out the following:

You will need: a hand lens; a light microscope; newsprint; moss plants; a pencil; paper
Procedure
1. Place the lens just above the newsprint, and then look down through the lens.
2. Move the lens closer to your eyes, and then further away from your eyes.
3. Repeat step 2, above, using a moss plant. Identify the small green leaves and the tiny transparent
rhizoids.
Questions
1. How does the image appear when the hand lens is close to the object and when it is further away from
the object?
2. Make a simple drawing of a moss plant, and label the structures you have identified; for example, the
leaves, rhizoids and stem.

Biologists make many observations when they work. Observations enable them to see the details of living
things. Many things are too small for us to see using only our eyes, so they need to be made bigger, or
magnified. There are two instruments that biologists use for this. When they work outside the laboratory,
they can use a hand lens. Inside the laboratory, they can use a microscope.
Hand lenses
A hand lens is a magnifying instrument that is held in the hand. We use it to look at small things, such as
insects, flowers and animal parts, that are too big to put on a microscope slide.
Microscopes
The first microscope was invented by Robert Hooke in 1665. He used it to look at cells. Today, we can use
powerful microscopes to see viruses, bacteria and cells. There are many types of microscopes.

Figure 4.3: Hand lens Figure 4.4: The first microscope, invented by Robert Hooke, in 1665

Unit 4: Magnifying instruments and biological drawings 39

4.2. Parts of a microscope
Activity 4.2

Work out the following:

You will need: a microscope, or you can use the diagram below if your school does not have a
microscope
Procedure
1. Look at the microscope and Figure 4.5, which shows the parts of a light microscope.
2. What are the functions of the main parts of a microscope?

In the following experiment, you will learn about the different parts of a light microscope and what the
function of each part is.

1 eyepiece – the lens that 9 light source – bulb or

you look through; it usually lamp; if the microscope
1 has 10× or 15× power has a mirror, it is used
2 2 body tube to reflect light from an
external light source up
3 nosepiece – holds two or
through the bottom of the
more objective lenses; it is
stage
rotated to change power
10 coarse focusing knob –
4 objective lenses – lenses of
brings the specimen into
different magnification; the
focus under a low-power
shortest lens has the lowest
3 objective lens; it cannot
power; the longest lens has
4 be used with high-power
the highest power
objective lens
5 stage clip – holds the slide
11 fine focusing knob –
in place
5 brings the specimen into
6 stage – the flat platform focus under medium- and
where you place your high-power objective
10 7 6 slides; it can be moved left lenses
and right to view the slide
8 12 light switch – turns the
and up and down to focus
11 9 light source on
7 diaphragm – a rotating
12 disk with holes of different
sizes; it is used to vary
the intensity and size of
the cone of light that is
projected upwards into the
Figure 4.5: Light microscope slide
8 condenser – focuses the
light onto the slide

40 Topic 2: Organisation and maintenance of life

4.3. The functioning of a microscope
Activity 4.3

Work out the following:

1. Carefully carry a microscope to your workbench or desk using both hands. One hand should be on
the arm of the microscope and the other underneath, below the base.
2. Identify the different parts of the microscope using Figure 4.5, on
page 42, to help you. Do not touch the surface of the lenses.
3. Turn the nosepiece so that the objective lens with the lowest magnification is in position.
4. Turn the coarse focus knob and observe what happens to the objective lens.
5. Turn the mirror so that light is reflected through the lens.

The following are the steps in using a microscope

1. Make sure that the lowest power objective lens is in place.
2. Turn the coarse focus knob until the lens is as far away from the stage as possible.
3. Put the slide onto the stage and clip it in place. Move the slide until the specimen is directly under the
lens.
4. Slowly turn the coarse focus knob until the specimen is in focus. You can use the diaphragm above the
mirror to change the amount of light passing through the specimen.
5. Once the specimen is in focus with one lens, it will be nearly in focus with the other lenses. Now you will
need to turn only the fine focus knob.
6. Turn the nosepiece so that a more powerful objective lens is in place above the slide.
7. Use the fine focus knob to bring the specimen into focus.
How to store and care a microscope
Care of a microscope
Microscopes are expensive instruments that can be damaged easily, so it is important to handle them with
care. These are some of the ways of caring for a microscope.
1. Always place the microscope in its box when it is not in use, or cover it with a plastic cover.
2. Avoid touching any lens surface of the condenser and objectives. Polish these regularly using a tissue.
3. Never force the coarse and fine focus adjustments beyond the end of their range of movement.
4. Always carry a microscope by the arm and stand, and use two hands.
5. Keep the stage dry and clean.
6. Always cover the specimen on the slide with a cover slip, to protect the objective lens.
7. Always move the lens up when focusing, to avoid breaking the slide.
8. Clean the mirror occasionally using a tissue.
9. Never unscrew the lens components.
4.4. Biological drawings
Biologists need to make careful and accurate observations. They need to record what they see, and so they
need to draw accurate biological drawings of their specimens. We can learn the skill of drawing biological
specimens accurately, through practice.

Unit 4: Magnifying instruments and biological drawings 41

A good biological drawing should:
• have a detailed, underlined title at the top of the page
• have smooth, fairly thin, solid pencil lines made by controlled movements of the hand
• be large enough to show all the parts
• be neat
• show the magnification (you will learn about this in the
next section).
Head of a fly × 100
1
Transverse section of a mango ×
2
skin sensory palp

compound eye
pad with grooves

proboscis

flesh
scar where fruit joined
tree
large stone containing seed
Figure 4.7: Examples of biological drawings

4.5. Magnification
The magnification of a specimen is a measure of how much bigger it is when viewed with a hand lens or a
microscope compared with its actual size.
The magnification of a hand lens is usually written on it. Hand lenses can magnify specimens between 2 and
6 times.
For a light microscope, the magnification of each lens is written on its side. It can be written in the form
of ‘×40’, or ‘40×’ or simply ‘40’. There are two lenses: the eyepiece lens and the objective lens. The total
magnification of an image through a microscope is calculated as follows:
Total magnification of microscope = eyepiece magnification× objective lens magnification

Worked example: Calculate total magnification

A learner views a specimen using a microscope with an eyepiece lens that has a magnification of 10×.
She uses an objective lens of 50×.
What is the total magnification?
We use this formula.
   Total magnification = eyepiece magnification × objective lens magnification
So total magnification = 10 × 50
   = 500×

42 Topic 2: Organisation and maintenance of life

Magnification of biological drawings
When you draw a specimen, you usually also magnify it. Your drawing will be bigger than the image that you
see through the hand lens or microscope.
If you have an image or biological diagram of a specimen, you can work out how many times it has been
magnified. You work with three factors when working out the magnification of an object. These are:
• the image size (how large an image is or how big a drawing of the specimen is)
• the actual size of the specimen (how large it is in the real world)
• the magnification (how much larger the image size is compared with the actual size; how many times
the image has been enlarged).
We use this formula to work out the magnification of a drawing.
size of drawing
Magnification =
actual size of specimen
In this formula, size could be length or breadth, but the same measurement must be taken of both the
specimen and the drawing.
Always include a magnification or scale bar on your drawing.

Worked example: Calculate magnification of a drawing

Uwimana measures a bean seed. It is 3 cm long. She makes a biological drawing of the seed. The length
of the seed in her drawing is 15 cm. By how much has the bean seed been magnified?
15
Magnification =
3
= 5×
This means that the drawing is five times bigger than the bean specimen.

Self assessment 4.1

1. A leaf measures 4 cm in length. A diagram of the leaf that appears in a Biology textbook measures 12
cm. By how much has the leaf been magnified?
2. A group of learners use a microscope to view a cell. The eyepiece lens magnifies objects 10× and the
objective lens that they use magnifies 25×. What is the total magnification?
3. A learner looks through a microscope using a 20× eyepiece lens and a 40× objective lens. What is the
total magnification that the learner is using?

Unit 4: Magnifying instruments and biological drawings 43

 Experiment 4.1
Work out the following:
You will need: a microscope; a hand lens; slides; glycerine; a razor blade; pollen grains; cover slips; a
needle; forceps or small tweezers;
a dropper; an onion bulb; iodine solution; a dead fly or mosquito
Procedure
Part A
1. Use the hand lens to look at the insect specimen.
2. Discuss how much detail you can see.
Part B
You will now prepare a slide for viewing using a light microscope. Look at Figure 4.6, on page 45, to help
you as you work.
1. Make sure that the glass slide is clean. Use a tissue to clean it if it is dirty. Try to hold the slide on the
edges.
2. Place a small drop of iodine in the centre of the slide (see A in Figure 4.6).
3. Use forceps to peel off the thin outer layer that surrounds the fleshy white storage leaves of the onion
(see B). This layer is the epidermis; it is made up of a single layer of cells.
4. Carefully, use a razor blade to cut off a small piece of the epidermis, about one centimetre square.
5. Place the piece of onion skin in the drop of iodine (see C). Try to flatten it against the slide, using the
needle.
6. Hold one side of the cover slip as shown in the diagram, and slowly lower it on top of the iodine (see
D). Do this carefully to avoid trapping air bubbles.
7. If there is iodine around the slip cover, clean it away using a tissue (see E).
8. Place the slide onto the stage of the microscope (see F).

44 Topic 2: Organisation and maintenance of life

Part C
1. Adjust the microscope to view the specimen (as you learnt to do in Activity 4.2).
2. Make an accurate drawing of what you see.
3. Make other slides using specimens such as a fly’s wing and pollen grains. Use glycerine instead of
iodine for these slides.
A B C

E F
D
Figure 4.6: Preparing a specimen for viewing under a microscope

Checklist of learning (Unit summary)

In this unit, I have learned that:
Biologists use two types of instruments to observe things: hand lenses and microscopes.
These instruments magnify things, which means that they make them appear larger than their actual
size.
A hand lens is often used outside on fieldtrips as it is easy to carry and use.
Microscopes are used in laboratories, and specimens can be seen at higher magnifications than when
using a hand lens.
The different parts in a microscope are designed to make it function properly.
Biologists need to observe specimens and record their observations by drawing biological drawings.
The total magnification of a specimen when viewed with a microscope can be calculated by multiplying
the eyepiece magnification by the objective lens magnification.
The magnification of a biological drawing of a specimen can be calculated by measuring the size of the
drawing and dividing it by the actual size of the specimen.

Unit 4: Magnifying instruments and biological drawings 45

End unit assessment
1. Name two types of instruments that can be used to magnify things.
2. List two differences between a hand lens and a microscope.
3. Give one advantage of using a hand lens and one advantage of using a microscope for magnifying
specimens.
4. Explain why you must NOT use the coarse focus adjustment knob when the high power objective is
in place.
5. Complete the table.
Eyepiece magnification Objective lens magnification Total magnification

5× 25×
10× 100×

6. Look at the drawing of a bee. If the Provide labels for the microscope
bee’s actual length is 1,5 cm, how parts A to E.
many times has it been magnified
in the drawing?

A
B
C
D
E

7. Follow the instructions and do the following:

a. Collect two biological specimens. They can be a flower, leaf or plant you collected outside the
classroom.
b. Use a hand lens to view your specimens.
c. Make careful biological drawings of your specimens. Label anything you can. Remember to give the
magnification of
your drawing.
d. Which part of this activity did you find the most difficult? Explain what you would do differently if
you had to do the activity again.

46 Topic 2: Organisation and maintenance of life

 UNIT 5 Plant and animal cells

Key unit At the end of this unit, I should be able to:

competence
• Explain the role of a cell in a living organism
To be able to • Describe the structure of a plant and animal cells
differentiate • Identify the different parts of the cell
between • Explain the uses of the various structures seen under the light microscope in the plant and
animal and animal cell
plant cells • Explain that cells with high rates of metabolism contain large numbers of mitochondria for
using a light sufficient energy
microscope. • Organize a science practical setup according to given instructions
• Prepare slides of human cheek cells and epidermal cells of an onion
• Explain the differences in the structure of plant and animal cells seen under a light
microscope
• Demonstrate that plant and animal cells differ in shape
• Appreciate the importance of cells in organisms
• Show perseverance when observing slides of plant and animal cells
• Pay attention while handling delicate slides and sharp instruments to avoid injury.

Introductory activity
Observe well the following structures and think about what you learnt in the previous unit and try to work on given
questions

cell wall
cell membrane
cytoplasm
cell
large vacuole membrane
containing cell sap
mitochondrion
nucleus
nucleus
small vacuole
mitochondrion
cytoplasm
chloroplast

A B
Figure 5.1
1. Between the above cells suggest the animal cell and the plant cell
2. Use a Venn diagram to compare the two cells provided in this activity
Unit 5: Plant and animal cells 47
5.1. The cell
Hint
Activity 5.1
Microscopes are
useful for identifying
Think about what you learnt in the previous unit and earlier grades. Then,
organisms that cause
brainstorm the answers to these questions.
diseases in Rwanda
1. Arrange these structures in the correct order, starting with the smallest
structure: tissue, organ, cell, organism.
2. What different types of microscopes are available for biologists to use
to view cells?
3. How would a biologist choose the type of microscope he or she should
use to view a cell?

Cells are the basic units of all living organisms. Cells are made of molecules
such water, proteins, carbohydrates and fats. These molecules are made up of
atoms such as carbon, hydrogen and oxygen. Cells are the building blocks of
living organisms.
Some organisms, such as bacteria, are made up of only one cell. These are
called unicellular organisms (‘uni’ means ‘one’). Other organisms, such as
humans and trees, are made up of many cells. They are called multicellular
organisms (‘multi’ means ‘many’).
Because cells are too small to be seen with the naked eye, scientists use
microscopes to see the structure of cells. Sometimes they use powerful
microscopes called electron microscopes to view structures that are too
small to be seen with a light microscope.
Structures found in plant and animal cells
All cells have the same basic structure. Cells contain cytoplasm and
organelles. The cytoplasm is a living, jelly-like substance in which the
organelles are found. Many chemical reactions take place inside the
cytoplasm. It is made mainly from water, in which substances such as
sugars and gases are dissolved. The organelles in the cytoplasm carry out
special functions inside the cell. Examples of organelles include the nucleus,
chloroplasts and mitochondria. A cell membrane surrounds the cytoplasm.

48 Topic 2: Organisation and maintenance of life

Figure 5.2 shows typical plant and animal cells and their organelles.

cell wall
cell membrane
cytoplasm
cell
large vacuole membrane
containing cell sap
mitochondrion
nucleus
nucleus
small vacuole
mitochondrion
cytoplasm
chloroplast

A B
Figure 5.2: A generalised plant cell (A) and an animal cell (B)

Experiment 5.1
Work out the following:
You will need: a microscope; prepared slides of onion epidermis and human cheek cells; drawing paper
Procedure
1. Look at Activity 4.1, on page 43, to remind yourself how to use a microscope to view specimens.
2. View the prepared slides that your teacher will give you.
3. Make careful drawings of the two different types of cells using. Figure 5.3, below, to help you. Only
draw the structures that you
can see on the slide.
Questions
1. Mention two things that you did to ensure that you avoided any injuries whilst doing this activity.
2. How do the two types of cells differ in shape?
3. Which structures are present in the onion cells but absent in the cheek cells?
4. What was the total magnification that you used to view these specimens?

A B
Figure 5.3: A micrograph of an onion epidermis Human cheek cells, as seen under a light microscope

Unit 5: Plant and animal cells 49

There are many different types of plant and animal cells. Although they all have slightly different structures
(depending on their functions), they all have these organelles:
• cell membrane
• nucleus
• mitochondria
• vacuole
• cytoplasm.
Cell membrane
The cell membrane surrounds the cytoplasm and keeps the cell contents in place. It is selectively
permeable, which means that it can control the movement of substances into and out of the cell.
Nucleus
The nucleus is the control centre of the cell. It is easily seen inside the cell. The nucleus is round and found
near the centre of an animal cell and on the side of a plant cell.

nuclear membrane

pore
nucleoplasm
nucleolus
chromatin network

Figure 5.4 The nucleus, as seen using an electron microscope, is the control centre of the cell.
The nucleus plays an important role when the cell divides to make new cells. It contains the hereditary, or
genetic, information that is passed from parents to their offspring during reproduction.
Mitochondria
Mitochondria (singular = mitochondrion) are the organelles inside plant and animal cells where the reactions
of cellular respiration take place. Energy that the cell can use is made in the mitochondria. Some cells,
depending on their function, have more mitochondria than others. For example, muscle cells (which need a
lot of energy to work) have several thousand mitochondria.
Vacuoles
Vacuoles are organelles that usually contain fluid. They are surrounded by a membrane. Animal cells have
small vacuoles or no vacuoles. The fluid in animal vacuoles often contains substances such as enzymes, or
stored food or waste products. Plant cells have large vacuoles that take up a lot of space inside the cell. Plant
vacuoles usually contain water and dissolved substances, such as mineral salts and food molecules. Plant
vacuoles are important for keeping the cell rigid.

50 Topic 2: Organisation and maintenance of life

 Self assessment 5.1
1. Define each of these terms:
a) unicellular
b) multicellular
c) organelle
2. Give one example each of a unicellular and a multicellular organism.
3. What is the function of each of the following?
a) the cell membrane
b) the nucleus
4. Which organelle in the cell makes energy?
5.    a) What is sometimes stored inside vacuoles?
b) What is the difference between the vacuoles found in animal cells and those found in plant
cells?
6. Use the library or the Internet to find out about the structure and the functions of each of the following
cell organelles: nucleus, mitochondrion, ribosome, Golgi body, endoplasmic reticulum, lysosome and
chloroplast.

5.2. Differences in the structure of plant and animal cells

Activity 5.2

Observe again the animal & plants cells on figure 5.2 in previous page and answer the following questions:
a. What are the common parts they have.
b. What are the parts specific to plant cell?
c. Establish a comparison between the two cells.

a) Structures that are found only in plant cells

Two important structures are found in plant cells but not in animal cells: cell walls and chloroplasts.
Cell wall
The cell wall is a rigid structure found around the outside of plant cells. It is not living, and it is made up of
a substance called cellulose.
The cell wall gives the plant cell its shape. Because the cell wall is rigid, it protects the contents of the cell. It is
fully permeable, which means that substances can move freely into and out of the cell through the cell wall.
Chloroplasts
Chloroplasts are the organelles found in plant cells that carry out the process of photosynthesis.
They contain a green pigment called chlorophyll. Chloroplasts are also found in the cells of algae and
some bacteria.
b) Plant cells versus animal cells
Although plant and animal cells have many features in common, there are some obvious differences. Table
5.1 lists the main differences between plant and animal cells.

Unit 5: Plant and animal cells 51

Table 5.1. The main differences between plant and animal cells
Plant cell Animal cell
Shape • Have cell walls • Do not have cell walls
• The cell wall is rigid and has a fixed shape • Because there is no cell wall, they vary in shape
Chloroplasts Contain chloroplasts, which are used for Animals do not photosynthesise, so cells do not
photosynthesis have these organelles
Vacuoles Have a large, central vacuole Have no vacuoles or one or more small vacuoles
(which are much smaller than plant vacuoles)

Self assessment 5.2

1. a) What is the function of the cell wall in plants?
b) What substance is the cell wall made of?
2. a) What is the function of chloroplasts?
b) What pigment is found inside chloroplasts?

Checklist of learning (Unit summary)

In this unit, I have learned that:
Cells are the basic units of life; they are the building blocks of living organisms.
Some organisms consist of only one cell (unicellular), whilst other are made up of many cells
(multicellular).
We can view cells using either a light microscope or an electron microscope.
All cells contain cytoplasm and organelles such as a nucleus, mitochondria, a cell membrane and
vacuoles.
The cytoplasm is a jelly-like substance in which the organelles are found inside the cell.
The cell membrane surrounds the cytoplasm and controls what goes in and out of the cell.
The nucleus is the control centre of the cell and contains hereditary material.
Mitochondria are the organelles in the cell where energy is made; cells that need more energy, such
as those found in muscles, have more mitochondria.
Vacuoles are membrane-bound organelles that contain fluid; plants have large vacuoles and animals
have no vacuoles or small vacuoles.
Only plant cells have a cell wall, which gives the cell a rigid shape and allows substances to pass in
and out of the cell.
Chloroplasts are organelles in plant cells where the reactions of photosynthesis take place.

52 Topic 2: Organisation and maintenance of life

End unit assessment
1. Match the organelles in Column A with the correct function in Column B.
Column A Column B
1.1 Nucleus A. Living, jelly-like fluid in which reactions take place inside the cell
1.2 Mitochondria B. Control centre of the cell
1.3 Cell wall C. Produces energy
1.4 Cell membrane D. Controls what goes in and out of the cell
1.5 Chloroplast E. Photosynthesis takes place here
1.6 Cytoplasm F. The rigid structure on the outside of plant cells that keeps the shape of the cell
2. Give the meaning of each of these terms.
a) permeable c) enzymes
b) hereditary d) photosynthesis
3. Draw a table to show the differences between a plant and an animal cell. Include these headings:
Shape, Outer covering, Organelles, Vacuoles.
4. Copy this table, and then complete it.

Plant cell Animal cell

Shape
Outer covering
Organelles
Vacuoles

Unit 5: Plant and animal cells 53

 Levels of organisation in multicellular
UNIT 6 organisms

Key unit competence At the end of this unit, I should be able to:

To be able to explain • Recall that a cell is a basic structure of an organism

specialisation of cells, • Describe the different types of cells in this unit and state their functions
and the link between • Describe the different cell structures found in animals and plants and
levels of organisation how they relate to their functions
in multicellular • Identify different levels of organisation in multicellular organisms
organisms • Observe and illustrate different types of cells and tissues under light
microscope or micrographs
• Categorize plant and animal tissues using observation of micrographs
or slides
• Illustrate well labelled structures of xylem and phloem tissue from
slides or micrographs of sections of vascular plants
• Sequence the levels of organization of multicellular organisms from
the simplest to the most complex
• Differentiate the relationship between the structure and function of
specialised cells
• Appreciate the complexity of life from the tiny cell through to the
tissue, organ, system and organism levels of organisation
• Be aware that an organism is a complex organisation of cells, an
important unit of life.

Introductory activity
Think back to what you learnt in the last two units. Then,
brainstorm the answers to these questions.
1. Why is the cell referred to as the ‘basic unit of life’?
2. Are all cells the same? If not, in what ways are they
different?
3. What structures do plant cells have to help them carry out
photosynthesis?
4. Are all organisms made up of many cells? What do we call
single-celled organisms? What do we call organisms that
consist of many cells? Give an example of an organism
Figure 6.1. Red blood cells are part of blood and that has many cells in its body.
are specialised to transport oxygen.

Unit 6: Levels of organisation in multicellular organisms 55

6.1. Cell specialisation
Activity 6.1

1. Multicellurar organisms have different cells.

a) What are the special cells do they have?
b) Why those cells are considered as specialised cells?
2. Work out the following
You will need: a microscope; prepared slides or micrographs
Procedure
a. Use a microscope to look at the prepared slides of different tissues
that your teacher will give you. Remember the rules for using a
microscope. If your school does not have slides, use the micrographs
that your teacher gives you.
b. Identify the tissues shown in the slides/micrographs. Decide which
slides/micrographs show plant tissue and which show animal tissue.
Discuss the reasons for your choice in your group.
c. Can you identify specialised cells in the tissue specimen?
d. Draw labelled biological diagrams of each tissue specimen in the Hint
slides/micrographs
Understanding how
In the previous unit, you learnt about plant and animal cells. Not all cells look our bodies are made
the same or work in the same way. There are many different types of cells and up can be useful in
each type can carry out different functions. For example, in animals, cells in health related careers
muscles are specialised to bring about movement. These cells contain lots of in Rwanda
mitochondria so that they can make energy for the muscles to work.
Blood cells in animals are another specialised type of cell. They transport
oxygen. A plant’s leaf cells are specialised to perform photosynthesis, whereas
its root cells are adapted to take in water and nutrients from the soil. The
cells are able to do these different functions because they are slightly different
in structure from one another.
In this unit you will find out more about some specialised cells in animals and
in plants. You will also learn how their structure is linked to their functions.
mucus in
Examples of some specialised animal cells ciliated goblet cell
cell cilia
In this section, we look at examples of different types of animal cells whose
structures have been adapted to enable them to perform different functions.
Ciliated cells
Ciliated cells have tiny hair-like structures, called cilia, on their surfaces.
There are also other specialised cells, called goblet cells, amongst the ciliated nuclei
cells. Goblet cells make a substance called mucus.
Ciliated cells line the surfaces of some parts of the body, such as the air
passages. Air passages take air to and from the lungs. The cilia trap dust Figure 6.2. Ciliated cells have
particles and stop them from going into the lungs. Mucus from the goblet hair-like structures, called
cilia.
cells also traps dust.

56 Topic 2: Organisation and maintenance of life

 Ciliated cells are also found in the female reproductive organs. You will
learn about their function in this part of the body later on.
Nerve cells
axon Nerve cells, or neurons, are specialised to conduct nerve impulses in the
nervous system. They carry information from one part of the body to another
part.
nucleus Nerve cells are long and thin, and are grouped together in bundles to form
cell body
nerves. Their shape makes them suitable for conducting nerve impulses over
long distances.
Figure 6.3 Nerve cells can Red blood cells
transmit nerve impulses.
Red blood cells are specialised cells that are found in the blood. They transport
   red blood cell oxygen around the body.
Red blood cells are small and have an unusual shape. They are referred to as
biconcave discs. This shape gives them a large surface area on which oxygen
molecules can bond. Red blood cells do not have a nucleus. They are packed
full of a special substance called haemoglobin. Haemoglobin attracts oxygen
molecules, which makes red blood cells well suited for carrying oxygen around
they body. The cells are elastic, so they can easily squeeze through narrow
Top view tubes in the blood system.

Side view

Figure 6.4. Red blood cells

are specialised to carry
oxygen.

Sperm cells
Sperm cells are male sex cells. They are made inside the
male reproductive system in structures called the testes.
flagellum Sperm cells are specialised for joining, or fusing, with the
female sex cell, the egg. Sperm cells have a tail, called a
flagellum, which they use to swim. Because sperm cells can
middle piece move, we say that they are motile. There are large numbers
containing of mitochondria in the middle region of a sperm cell. These
head mitochondria
mitochondria make energy to help the flagellum to move.
The flagellum enables the sperm cell to swim towards the
egg when it is inside the female reproductive system.
nucleus In the head of the sperm, there are special enzymes inside
acrosome the acrosome. These enzymes break down the membrane
Figure 6.5: A sperm cell is a male sex cell around the female egg cell. The sperm nucleus contains
genetic material. The nucleus enters the egg cell and fuses
with the nucleus of the female egg during fertilisation.

Unit 6: Levels of organisation in multicellular organisms 57

 nucleus
cell Egg cells
membrane Egg cells are female sex cells. They are also called ova (singular
= ovum). They are produced in the ovaries of the female
reproductive system.
Egg cells are large cells that have a large nucleus, and they can be
seen with the naked eye. The cytoplasm contains many nutrients.
Each egg cell has a special cell membrane that allows only one
male sperm cell to pass through it. There is genetic material in
the egg’s nucleus. The egg and sperm nuclei fuse to form a single
cell, called a zygote.
cytoplasm Examples of some specialised plant cells
mitochondria
Figure 6.6: An egg cell is a female sex cell. Examples of plant cells that have been specialised to do different
functions include root hair cells, xylem cells and mesophyll
cells.
Root hair cells
Root hair cells are found on the outside layer of roots, where they
absorb water and dissolved nutrients from the soil.
Look at the diagram of a root hair cell in Figure 6.7. You can see
that the cell has a long, thin extension that pushes between the
cytoplasm soil particles. This increases the surface area of the root cell, which
enables more water to pass into it. Root hair cells have a large
permeable cell wall
vacuole which water can pass into. Their cell wall is permeable,
central vacuole so water passes easily into the cell.

root hair

Figure 6.7: Root hair cells are specialised

for taking up water from the soil.

58 Topic 2: Organisation and maintenance of life

Xylem cells
Xylem vessel
Xylem cells are sometimes called xylem vessels. They transport water up
from the roots to the other parts of the plant. one direction
only
Xylem cells are non-living cells. The end of each cell has holes in its wall and
the cells are arranged one on top of the other, to form a long narrow tube.
water and
These tubes, rather like long straws, are ideal for transporting water. minerals

holes in
Phloem cells cell walls

Phloem is a living tissue. It transports food made by the leaves during

photosynthesis to all parts of the plant. Figure 6.8 shows the difference
between the xylem and phloem. In the xylem, water flows in one direction thickened
only from the roots to the leaves. In the phloem, the food flows in both wall
directions.

Mesophyll cells Phloem vessel

Most cells inside a leaf are found between the upper and lower surfaces. (see
Figure 6.9). This region of the leaf is called the mesophyll. Mesophyll cells
are specialised for photosynthesis, which is their main function. Look at the
water and food
diagram below, which shows the inside of a leaf.
There are two types of mesophyll cells and they are found in different places
in the mesophyll. These cells are called palisade mesophyll cells and spongy two-way flow

mesophyll cells. Palisade mesophyll cells are long, thin cells which are full
of chloroplasts. They are found near the upper surface of the leaf. It is easy
for them to trap lots of light in this position. Spongy mesophyll cells also
have lots of chloroplasts and they are loosely packed in the leaf. This makes
it easy for gases, such as carbon dioxide, which is needed for photosynthesis,
to move into and out of these cells. Figure 6.8: Difference between
Xylem and phloem cells.

air space

Figure 6.9: Palisade and spongy mesophyll cells are leaf cells specialised for photosynthesis.
Unit 6: Levels of organisation in multicellular organisms 59
 Self assessment 6.1
1. Give the meaning of each of these words.
a) specialised c) neurons
b) cilia d) haemoglobin
2. a) What is the function of ciliated cells?
b) List two ways in which ciliated cells are adapted to
their function.
3. a) What is the function of red blood cells?
b) List two ways in which red blood cells are suited to
their function.
c) Make a neat, labelled drawing of some red blood cells.

Advantages of specialisation of cells

Specialisation of cells occurs only in multicellular organisms and not in unicellular organisms.
Cell specialisation gives these advantages to multicellular organisms.
• It enables them to grow bigger.
• It enables them to carry out complex processes. Different cells carry out different functions.
• Specialised cells can work together to form tissues, organs and organ systems.

6.2. Organisation in multicellular organisms

Activity 6.2

Structures of similar level in an organisms may be grouped togother. What will be the relationship
between
a) Cells and tissues?
b) Tissues and organs?
c) Organs and organ systems?

There are four levels of organisation in multicellular organisms such as plants and animals: cells, tissues,
organs and organ systems. An organism is made up of many organ systems which enable it to function for
life.
Cells
These are the most basic units of life. There are many different types of cells in a multicellular organism. They
are specialised to do a certain function.
Tissues
In multicellular organisms, similar cells are grouped together to form tissues. A tissue is a group of specialised
cells that have a similar structure and function. For example, muscle tissue is composed of muscle cells,
which function to help the animal move, by contracting and relaxing. Examples of tissues in plant leaves
are xylem, phloem and mesophyll. As you have learnt, xylem is made up of xylem cells, which are able to
transport water. Phloem transports food in the plant. Xylem and phloem are found in leaf veins. Mesophyll
tissue is made up of mesophyll cells and makes food.

60 Topic 2: Organisation and maintenance of life

Organs
Organs are structures that are made up of tissues. For example, your stomach is an organ for digesting your
food. A particular organ may contain several different tissues. For example, your stomach contains muscle
tissue (for mixing up the food) as well as glandular tissue (which produces digestive juices). Animal organs
include the skin, heart, liver, brain, lungs and kidneys. Roots, stems, flowers, leaves and fruits are plant
organs.
Organ systems
Organ systems are the highest level of organisation. A system consists of several organs working together to
perform a function of life. For example, your digestive system consists of your stomach and your intestines
(amongst other organs), which function to digest your food. In plants, the leaves, stems and roots work
together to form a transport system.

Organ system: digestion

stomach

Organ – stomach Part of the stomach has been cut

open to show the layers
stomach lining

muscle layer Tissues Enlarged diagram showing the

different tissues of the stomach
Cells
epithelial tissue

epithelial cells muscle tissue

Notice that muscle cells look the same as one another and
muscle cells epithelial cells look the same as one another

Figure 6.10: Levels of organisation of a human being: cell, tissue, organ, system

Unit 6: Levels of organisation in multicellular organisms 61

 Organ systems

leaf

Organ – leaf
stem
vein
root
leaf blade
midrib Tissues
epidermal tissue

mesophyll tissue xylem and phloem tissue

Cells

Cell wall is made up of

cellulose molecules

Figure 6.11: Levels of organisation of a multicellular plant organism: cell, tissue, organ, organ system

Self assessment 6.2

1. Define each of these words.
a) cell
b) tissue
c) organ
d) organ system
2. Give an example for each of the words in question 1.
3. Make a simple drawing showing organisation in multicellular organisms. Use Figure 6.10, on page
64, and Figure 6.11, above,
to help you.
4. Name two animal tissues and two plant tissues.

62 Topic 2: Organisation and maintenance of life

Checklist of learning (Unit summary)
In this unit, I have learned that:
In multicellular organisms, cells are specialised to perform certain functions.
Examples of specialised cells in animals include ciliated cells, nerve cells, red blood cells, sperm cells
and egg cells; examples in plants include root hair cells, xylem cells and mesophyll cells.
A group of similar cells is called a tissue.
Plant tissues, such as mesophyll tissue and xylem and phloem tissue, consist of similar cells that are
structurally adapted to their functions.
Mesophyll tissue in the leaves contains cells with lots of chloroplasts, where the reactions of
photosynthesis take place; xylem tissue transports water around the plant.
Animal tissues, such as muscle tissue, consist of similar cells that work together to perform a function.
Organs consist of many tissues that work together to do a certain function.
Animal organs include the skin, heart, liver, brain, lungs and kidneys; plant organs include roots,
stems, flowers, leaves and fruits.
An organ system consists of many organs working together, for example, the digestive system in
animals and the transport system in plants.
The specialisation of cells in multicellular organisms gives them advantages over unicellular organisms.

End unit assessment

1. Give the meaning of each of these words.
a) flagellum
b) motile
2. a) What is the function of sperm cells?
b) List three ways in which sperm cells are suited to
their function.
c) Make a neat, labelled drawing of a sperm cell.
3. a) What is the function of egg cells?
b) What happens when a sperm cell meets an egg cell?
c) How is the egg cell suited to its function?
4. Arrange these structures in the correct order, starting with the smallest.
organ tissue cell organ system organ
5. Give definitions for each of these words.
a) specialisation
b) permeable

Unit 6: Levels of organisation in multicellular organisms 63

6. Identify each cell structure or organelle from its description below.
a) Site of protein synthesis
b) Manufactures ATP in animal and plant cells
c) Controls the activity of the cell, because it contains the DNA
d) Carries out photosynthesis
e) Partially permeable barrier only about 7 nm thick2.
7. Which organelles are found in high numbers in muscle cells? Why is this so?
8. Explain the functions of each of these cells:
a) red blood cells
b) xylem cells
9. Look at the micrographs, and then answer these questions.
a) Identify each type of cell shown in pictures A
to D.
b) Identify each type of cell as either an animal
cell or a plant cell.
c) Give one function for each type of cell.
d) Explain how cell D is suited to its function.
A B C D

64 Topic 2: Organisation and maintenance of life

 UNIT 7 Food nutrients and diet

At the end of this unit, I should be able to:

• Explain the importance of the classes of foods

• List the main sources of food nutrients
• List the chemical elements that make up carbohydrates, fats and
proteins
• Explain that large molecules consist of smaller molecules joined
Key unit competence together
• State that a balanced diet is eating a variety of foods containing all the
To be able to analyse nutrients and in the correct proportions
the different food • Explain that people have different dietary needs, dependant on age,
nutrients and their gender and activity levels including pregnant and breastfeeding
significance to the mothers
human body. • Explain the effects of malnutrition
• Explain that obesity is the build-up of excess fat in the body due to
excess intake of calories
• Apply knowledge of deficiency symptoms to identify the different
deficiency diseases among individuals
• Test for carbohydrates, proteins and lipids in different food samples
• Demonstrate the different functions of water, mineral salts and
vitamins in the body
• Acknowledge the importance of having a balanced diet and its relation
to age and gender
• Appreciate the need for a specific diet for individuals who carry out
strenuous activities like sports and manual labour.
• Take care when using reagents to test for food types
• Appreciate the myths and values communities attach to certain foods
• Adopt and develop healthy eating habits by eating a balanced diet.
Introductory activity
Answer these questions:
1. Make a list of your favourite foods or the foods you
usually eat.
2. Can you think of the nutrients that these foods contain?
3. Try to work out the functions of each of these food
Figure 7.1: A balanced diet includes foods from all nutrients.
five food groups.

Unit 7: Food nutrients and diet 65

7.1. Food nutrients
Activity 7.1

Answer these questions.

1. Identify the nutrients present in the food sources A and B.
A B

2. Keep a journal of the food that you eat over a week. Bring the list to school, and discuss it with your
partner.
a) Is your list of foods similar to your partner’s list? If it is not, how is it different?
b) Did your list of foods change during the week? If it did, explain why?
c) Were any of the food nutrients missing from your lists?

Nutrients are chemical substances that organisms need to live. In Unit 1 you learnt that all living things need
nutrition in order to live. Animals get their nutrients from the food they eat. Plants get their nutrients from
the air, water and soil.
Food nutrients give organisms:
• energy for daily activities
• the building blocks for growth and cell repair
• substances that enable the organisms to function properly and stay healthy.
There are six types, or classes, of food nutrients: carbohydrates, proteins, lipids (fats and oils), vitamins,
mineral salts and water. Food nutrients are made up of elements such as carbon, hydrogen and oxygen, and
sometimes nitrogen, phosphorus and sulphur.

66 Topic 2: Organisation and maintenance of life

Sources of food nutrients
Table 7.1 shows sources of food nutrients for human beings.
Table 7.1 Sources of nutrients
Food nutrients Foods

Carbohydrates (sugars Bread, pasta, potatoes, cassava, maize, sorghum, rice,

and starches) fruits, sweets, sugar
Lipids (fats and oils) Nuts, fish oils, meat, milk, butter, cheese, cooking oil

Proteins Meat, milk, chicken, fish, eggs, groundnuts, soya

beans, seeds
Vitamins Fruits, vegetables, meat, fish, milk, wholegrain cereals,
nuts
Mineral salts Salt, milk, meat, fruits, fish, eggs

Water Drinking water, fruit and vegetable juices, food

Sources of nutrients.
Carbohydrates
Carbohydrates are nutrients made up of the elements carbon (C), hydrogen
(H) and oxygen (O). Some carbohydrates, such as glucose, are small, simple
molecules. Other carbohydrates, such as starch and cellulose, are large,
complex molecules.
Simple sugars such as glucose are the basic units of all carbohydrates. We
call these units sugars, or monosaccharides (‘mono’ means ‘single’ and
‘saccharide’ means ‘sugar’). Examples of monosaccharides include glucose
and fructose. Monosaccharides can join together to form disaccharides;
for example, sucrose. Polysaccharides, such as starch, are made up of many
single units (‘poly’ means ‘many’).

Unit 7: Food nutrients and diet 67

Figure 7.3 shows how polysaccharides are formed.

Combine to form

single a complex carbohydrate

sugars
Figure 7.3 Formation of large carbohydrates.

Starch is an important storage carbohydrate in plants. Glycogen is an important storage carbohydrate in

animals. It is stored in the muscles and liver. Cellulose is another large carbohydrate. It is found in plant
cell walls.
Lipids
Lipids are fats and oils. Fats are lipids that are solids at room temperature. They are used mainly to store energy
in the bodies of living things. Like carbohydrates, lipids are made of the elements carbon (C), hydrogen (H)
and oxygen (O). Lipid molecules consist of one molecule of glycerol joined to three long fatty acid molecules.

one glycerol three fatty acid Combine to form one lipid

molecule molecules molecule
Figure 7.4 A lipid molecule consists of a glycerol molecule joined to three fatty acid molecules.
Proteins
Proteins are nutrients made up of the elements carbon (C), hydrogen (H), oxygen (O) and nitrogen (N).
Some proteins also contain the element sulphur (S). Proteins are large molecules that consist of chains of
smaller molecules called amino acids. There are over 20 different types of amino acids. They can be joined
in different combinations to make many different proteins.

amino acids Combine to form

a protein

Figure 7.5 Proteins consist of long molecules of amino acids joined together.

68 Topic 2: Organisation and maintenance of life

7.2. The importance of food nutrients
Table 7.2 below shows the importance of the different food nutrient groups.
Table 7.2. Food nutrient groups and their importance
Food nutrients Importance
Carbohydrates (sugars and • Provide the body with energy
starches
Lipids (fats and oils) • Provide energy
• Help with absorption of fat-soluble vitamins A, D, E and K
• Form a layer beneath the skin that insulates the body and reduces heat loss
• Form a layer around organs to provide protection from injury
Proteins • Needed for growth
• Needed for repair of damaged tissues
• Needed for producing the enzymes required for chemical reactions
in the body
Vitamins Needed in small amounts for different functions in the body, for example:
• Vitamin C is needed to fight infections and heal wounds, and for healthy bones,
teeth, skin and gums
• Vitamin D helps the body to absorb calcium from food, which is needed for
healthy bones and teeth
Mineral salts Needed in small amounts for many different functions in the body,
for example:
• Iron is needed to make haemoglobin, a substance in red blood cells that
transports oxygen around the body
• Calcium is needed for strong bones and teeth
Water • Needed for chemical reactions in the cells
• Keeps body temperature constant
• Helps the movement of joints
• Helps digestion of food
• Helps to remove poisonous substances from the body

Unit 7: Food nutrients and diet 69

7.3. Food tests
We can test for the presence of food nutrients in different foods. In the next activity, you will work in groups
to find out whether food samples contain carbohydrates, proteins or fats. You will use chemicals called
reagents to do this. Remember to work carefully while doing these experiments.

Experiment 7.1: Experiments for food test

Tests for carbohydrates, proteins and lipids.
You will need: some bread, maize porridge or other complex carbohydrate; test tubes; a white
tile; droppers; iodine solution; cooked chicken; meat or egg; butter; water; nuts (crushed); sodium
hydroxide solution; copper sulphate solution; ethanol; test tube racks; permanent markers; test strips
for testing proteins, fats and glucose (if your school has these)
Procedure
Part A
1. Copy the table below. You will need this to record your results.
Colour change
Food sample Iodine Biuret test Ethanol
1. Bread
2. Maize porridge
3. Chicken
4. Meat
5. Egg
6. Butter

2. Set up your test tubes in a test tube rack. For each test, you need to test all your food samples. Use the
marker pen to label each test tube with the number that matches the table.

70 Topic 2: Organisation and maintenance of life

Part B
Starch is a carbohydrate. We can easily test for its presence in a food sample by using iodine.
1. Put a small piece of each food sample into a test tube or onto a white tile.
2. Use a dropper and add two drops of iodine to each food sample.
3. Observe what happens, and then record any colour changes in the table.

dropper

iodine solution

food sample
white tile

Figure 7.6. Test for carbohydrates

Part C
We test for proteins in a food sample by using the Biuret test. If proteins are present in the food, it will turn
purple when we add sodium hydroxide solution (colourless) and copper sulphate solution (blue) to the
sample. If there are no proteins in the food, the sample will remain blue.
1. Put a small piece of each food sample into a test tube and add some water.
2. Use a dropper to add about 20 drops of sodium hydroxide solution to the test tube.
3. Use another dropper to add about 2 drops of copper sulphate solution to the test tube.
4. Gently shake each test tube.
5. Observe what happens, and then record any colour changes in
the table.

dropper
sodium copper
hydroxide sulphate
solution solution
test tube (shake)
water

food
sample blue colour purple colour
indicates the
presence of protein

Figure 7.7. Test for proteins.

Unit 7: Food nutrients and diet 71

Part D
We test for lipids by using organic solvents such as ethanol. If lipids are present, they will dissolve in the
ethanol. When water is added to the ethanol, the water will turn milky.
1. Put a small piece of each food sample into a test tube and add some ethanol. Shake the test tube well
and then allow the contents
to settle.
2. Add the same amount of water to the test tube and shake it well.
3. Observe what happens, and then record what you see.

dropper

water

(shake) (shake)
ethanol

food
contents clear/ contents clear/ contents milky;
transparent transparent indicates the
presence of lipids

Figure 7.8. Test for lipids.

Questions
1. Make a list of the foods that you tested that contained carbohydrates, proteins and lipids. Some food
samples may contain more than one nutrient.
2. Did you take any precautions when you were doing these tests?
3. Is there anything that you would change if you did the tests again?

72 Topic 2: Organisation and maintenance of life

7.4. A balanced diet
A person’s diet consists of all the foods and liquids that he or she eats and drinks. A balanced diet gives us
all the nutrients we need in the right amounts, as well as enough energy for our body to function well. The
amount of energy we need is measured in kilojoules (kJ).

carbohydrates fruits and vegetables

non-dairy
proteins dairy foods
foods high in sugar
or fat

Figure 7.9. A balanced diet includes foods from all five food groups.

You have learnt about the groups of food nutrients your body needs to stay healthy. Your body needs different
amounts of each food nutrient. The ‘pie chart’ in Figure 7.9 shows the relative amounts of each food group
that we need for a balanced diet. Water is also an essential part of a balanced diet.
Table 7.3 describes the importance of each food group and gives the proportion each group should make up
in the diet.
Table 7.3. Food groups and their percentages in the diet
Food group Importance Examples % of diet
Carbohydrates Provide energy for growth and development. Bread, maize and cassava 33%
Wholegrain forms are best because they provide
extra fibre.
Fruits and These foods provide vitamins and minerals needed Bananas, spinach and tomatoes 33%
vegetables for a healthy immune system. They also provide
fibre. You should aim to eat five portions of these
foods per day.
Dairy foods These foods provide fat for energy, protein for Milk, yoghurt and sour milk 15%
muscle and nerve development, calcium for bone
development and vitamins for fighting infections.

Unit 7: Food nutrients and diet 73

Non-dairy These foods provide protein needed for muscle and Meat, eggs, beans 12%
proteins nerve development, and for tissues to repair after
infections.
Foods high in These foods should be limited to prevent excessive Cakes, biscuits, fried foods, 7%
sugar or fat weight gain or problems with chocolate and cooldrinks
blood sugar.

Exercise
Work in pairs.
The amount of energy different people need is shown in the bar chart in Figure 7.10. Look at the chart,
and then answer the questions.
7,000
6,000
Amount of energy (kJ)

5,000
4,000
3,000
2,000
1,000
0
Child Woman Pregnant Woman Male office Male
aged 10 aged 35 woman aged 70 worker athelete

Figure 7.10: The amount of energy needed by different people

1. Which person needed:

a) the most energy b) the least energy?
2. Explain your answers to question 1.

Balanced diets for different people

In previous exercise, you saw that different people need different amounts of nutrients and energy. A person’s
needs depend on their age, gender, level of activity and whether or not the person is ill. For example, males
need more energy per day than females of all ages, and people with very active jobs need more energy than
people who stay seated all day.
Young people
Children grow quickly and are very active, so they need a diet that provides lots of food nutrients and energy.
When they reach their teenage years, they have times of rapid growth called growth spurts, when extra
nutrients and energy are needed. A balanced diet for a school child should contain similar proportions of
foods to those shown in Figure 7.9 (see page 75), but in amounts that provide them with enough energy. The
child should also drink plenty of water.

74 Topic 2: Organisation and maintenance of life

Pregnant and breastfeeding women
Pregnant and breastfeeding women need more energy per day than the
average adult woman. A pregnant woman needs extra nutrients and energy
for the healthy growth and development of her baby.
A balanced diet for a pregnant woman should contain similar proportions
of foods to an average adult woman, but should include extra fruits and
vegetables, dairy foods, non-dairy proteins and water.
A breastfeeding woman needs extra energy and nutrients to make breast
milk. Her diet should contain similar proportions of foods to an average
adult woman, but with extra carbohydrates, dairy foods, non-dairy proteins
and water.
Sports players
People who play sport need extra energy for their sporting activities. They
also need extra nutrients to build and repair their muscles and to replace the
minerals lost in their sweat. A balanced diet for people who play sport should
contain similar proportions of foods to a healthy man or woman, but should
include extra carbohydrates and non-dairy proteins, as well as extra water
and other fluids.

7.5. Nutritional disorders

A nutritional disorder is also called malnutrition. It happens when a person’s
body has either too little or too much of a certain food nutrient. As a result,
their body does not grow or function properly. Examples of nutritional
disorders include deficiency diseases, starvation, obesity and constipation.
There are many reasons for malnutrition. It can be caused by poverty, where
people are either too poor to buy enough food, or can only buy cheap food
that does not provide all the nutrients they need. Malnutrition can also be
caused by poor food choices and poor cooking methods.
Deficiency diseases
Deficiency diseases occur when a person has too little of a vitamin or Figure 7.11. A child with
mineral. Examples of deficiency diseases include scurvy, rickets and rickets
anaemia.

Figure 7.12: The gums and teeth of a person with scurvy

Unit 7: Food nutrients and diet 75

Table 7.4, shows the causes, symptoms and prevention of some deficiency diseases.
Table 7.4. Deficiency diseases
Deficiency Deficiency Symptoms Prevention and treatment
disease
Vitamin C Scurvy Soft, bleeding gums, tooth loss, bleeding Eat citrus fruits such as oranges and
under the skin, and increase in the lemons, as well as guavas, papayas,
amount of time that wounds take to heal. potatoes and fresh green vegetables.
Vitamin D Rickets If the body does not have vitamin D, it Eat sources of vitamin D such as eggs,
and calcium cannot absorb the calcium it needs to butter, cheese, milk, and liver. Sunlight
make bones. People with rickets have soft encourages the manufacture of vitamin
bones that bend as they grow because D in the skin. Calcium is found in dairy
they cannot support the weight of the products and some green vegetables.
body. Deficiency in calcium may lead
to osteoporosis (brittle bone disease) in
adult females.
Iron Anaemia Less oxygen can be transported around Eat sources of iron such as liver, eggs and
the body by the red blood cells. People green leafy vegetables. Iron tablets are
with anaemia have a pale complexion, also a good source of the mineral.
lack energy, and suffer from tiredness
and weakness.

Starvation
Starvation occurs when a person does not eat enough food. There are two
forms of starvation: marasmus and kwashiorkor.
Marasmus is caused by not eating enough of almost all nutrients, but especially
energy-rich foods such as carbohydrates, fats and proteins. Marasmus causes
extreme loss of body fat and muscle. A sufferer of marasmus is very thin. Other Figure 7.13: A child with
symptoms of marasmus include lack of energy, severe hunger and swelling of marasmus
the hands and feet.
Kwashiorkor occurs when a person’s diet does not include enough proteins,
vitamins and minerals. Mainly children are affected. Sufferers have a swollen
stomach, while the rest of their body is very thin and has little muscle. Other
symptoms of kwashiorkor include changes in hair colour, skin rashes, swollen
hands and feet, and loss of appetite.

Figure 7.14: A child with

kwashiorkor

76 Topic 2: Organisation and maintenance of life

Obesity
Obesity is caused by eating a diet that contains too many energy-rich
carbohydrates and fats. These foods are usually called junk foods and contain
very few nutrients. The body stores the extra energy as body fat. Obesity can
lead to serious health problems such as heart disease, stroke and diabetes.
Impact of deficiency diseases
Deficiency diseases can affect a person negatively if they are left untreated. Figure 7.15: Obesity can lead
Some of the effects are: stunted growth, increased likelihood of getting to serious health problems.
infections, blindness (in the case of untreated vitamin A deficiency), being
unable to take part in everyday activities, deformity, and death.
When children get sick, parents or guardians and other family members have
to care for them. So, there is less time to do other activities that are necessary
for the family’s well-being. This can have negative effects on the family.
At a community and national level, caring for sick people takes up valuable
resources that could be used for the development of the community and
nation. In this way deficiency diseases, which are easily preventable, can slow
down the development of the community and nation.

Case study

Work in pairs. Read the case study and then discuss how soya milk can improve children’s health.
Life-saving soya milk
Soya milk contains all the proteins necessary to replace meat and milk. In a village in eastern Rwanda,
women have learnt how to extract soya milk from soya beans. Soya milk contains more proteins than
cow’s milk and many adults and children prefer it. Malnutrition amongst children in this area has
decreased in the last few years since the women’s soya milk production has started. There has also been
a decrease in the number of childhood illnesses in this area.

Constipation
Constipation occurs when a person does not eat enough fruits and vegetables. Their stools become hard and
difficult to pass. We can prevent constipation by eating food rich in fibre and by drinking plenty of water.

Unit 7: Food nutrients and diet 77

Checklist of learning (Unit summary)
In this unit, I have learned that:
All living things need food nutrients to provide energy, build and repair cells and
keep them functioning properly.
The main food groups are carbohydrates (sugars and starches), proteins, lipids (fats and oils), vitamins,
mineral salts and water.
Different foods contain different nutrients.
Simple carbohydrates are made up of single sugars, such as glucose; complex carbohydrates, such as
starch and glycogen, consist of many single sugar units joined together.
Lipid molecules are made up of a molecule of glycerol and three fatty acids.
Protein molecules are large molecules that are made up of amino acids.
Foods can be tested using reagents to find out which nutrients they contain.
A balanced diet contains all the food nutrients that a person needs in the right quantities.
Different people need different diets depending on their age, gender, level of activity and whether or
not they are ill.
A nutritional disorder occurs when a person does not have enough food or when their diet is lacking
certain vitamins or minerals.
Scurvy, rickets, anaemia, starvation and obesity are examples of nutritional disorders.

End unit assessment

1. Name six food nutrients.
2. Give an example of a food that contains:
a) carbohydrates b) proteins c) vitamins.
3. Name the elements that are found in each of the following:
a) carbohydrates b) proteins c) fats.
4. Give the basic units of each of the following:
a) carbohydrates b) proteins c) fats and oils.
5. What is a balanced diet?
6. Name three deficiency diseases.
7. a) Discuss some of the nutritional disorders that occur in your local community. Include the
causes, prevention and treatment of each disorder.

78 Topic 2: Organisation and maintenance of life

 b) What impact do these disorders have on:
i) an individual
ii) a family
iii) a community
iv) the nation?
8. Kalisa recorded the number of children at his local clinic that suffered from nutritional disorders
over three months. His results are shown in this table.
Nutritional disorder January February March
Rickets 5 4 6
Kwashiorkor 1 3 1
Anaemia 6 3 4

a) How many children in total had kwashiorkor?

b) In which month were there the most children with anaemia?
c) Which foods should children with anaemia eat?
d) Which vitamin and mineral should children with rickets eat more of in their diet?
9. Match the word in Column A with the correct statement in Column B.
Column A Column B
1.1 Carbohydrates A. Needed for healthy skin and gums
1.2 Iron B. Needed to build new cells
1.3 Proteins C. Helps make haemoglobin in red blood cells
1.4 Vitamin C D. Needed for energy

10. Name the reagents that are used to test for the presence of the following in a food sample:
a) proteins
b) starch.
11. A family has four members: an 80-year-old grandfather, a 35-year-old father, and 28-year-old
pregnant mother, and a 2-year-old boy.
a) Between the boy and the grandfather, who should be given more milk?
b) Why?
12. Miss Umutoni visited a doctor as her gums were bleeding and she complained that she was always
tired. The doctor told her to eat two oranges, spinach and plenty of red meat every day for one
month. After two weeks, Miss Umutoni felt better and went
to thank the doctor.
Discuss the causes of Miss Umutoni’s symptoms, and explain why her treatment
was successful.

Unit 7: Food nutrients and diet 79

 Structure and functions of the human gas
UNIT 8 exchange system

Key unit At the end of this unit, I should be able to:

competence • Identify the structures of the human gas exchange system namely the
To be able to describe larynx, trachea, bronchi, bronchioles, alveoli and associated capillaries
the structure and • List the functions of the parts of the human gas exchange system
functions of the • Observe the structure of gas exchange system and relate it to its
human gas exchange functions
system. • Demonstrate the structure of human gas exchange system using
models
• Appreciate the similarity between the human gas exchange system
and that of other mammals.

Introductory activity

Think back to your earlier grades. Then, discuss these questions.

1. What is respiration?
2. Why does respiration take place in the cells of the body?
3. Which gas is needed for respiration?
4. Which gas is produced by respiration?
8.1. Structure of the human gas exchange system
Activity 8.1

1. Name the respiratory organs in humans.

2. Do all organisms have the same respiratory organs?
3. Try to remember the pathway that air follows when we breathe in
until it reaches the respiratory organs.
Figure 8.1: We need oxygen
to make energy for exercise. Most living organisms need oxygen gas (O2) for respiration. You learnt in
Unit 1 that respiration is a characteristic of living things. During respiration,
glucose is broken down using oxygen, to release energy in cells. During this
process, carbon dioxide (CO2) is produced as a waste product. So, the cells
must take in O2 and get rid of CO2 at the same time. The movement of gases
across a surface or a membrane in opposite directions is called gas exchange.
Gas exchange enables the movement of gases. It takes place in our lungs and
in our cells.

80 Topic 2: Organisation and maintenance of life

How does gas exchange work?
In Figure 8.2, you can see that O2 molecules move from
one side of the gas exchange surface to the other side. The Low concentration High concentration
of O2 of O2
O2 molecules move from the side where there are lots of
them to the side where there are fewer of them. The CO2 O2
molecules move in the opposite direction through the gas
exchange surface. However, they too move from where CO2
there is a high concentration of CO2 molecules to where
there is a lower concentration of CO2 molecules.
The movement of molecules from a place where they are High concentration Low concentration
in a high concentration to a place where they are in a of CO2 of CO2
lower concentration is called diffusion. So, gas exchange
takes place by diffusion. gas exchange surface
Do not confuse gas exchange with breathing in mammals. Figure 8.2: The process of gas exchange
Breathing is the movement of air into and out of the lungs.
The structure of the lungs
Air moves in and out of the lungs. Humans get the oxygen
they need from the air. They get rid of carbon dioxide in
the air that leaves the lungs. The lungs are part of the gas
exchange system in humans.
Air is taken in from the outside, or inhaled, through the nasal cavity
nose and mouth. The nose has two nostrils, which lead
to the nasal cavity. The nasal cavity is lined with hairs and mouth cavity
mucus, which filter and moisten the incoming air. They tongue
also trap dirt and bacteria. Blood vessels warm the air as epiglottis
it passes through the nasal cavity. larynx
trachea
Air passes from the nasal cavity down a tube called the
trachea, or windpipe. There is a flap of cartilage at the top
lung
of the trachea that flaps over it during swallowing. This
stops food from entering the trachea. The trachea is held bronchus
open by C-shaped rings of cartilage.
The trachea branches into two smaller tubes called
bronchi (singular = bronchus). One bronchus leads to
each lung and branches into many smaller tubes called
bronchioles. The bronchioles end in many bunches position of the
of small, thin-walled air sacs called alveoli (singular = heart diaphragm
alveolus). The alveoli are the gas exchange surfaces. The Figure 8.3: The structure of the human gas
alveoli provide a very large surface area for gas exchange. exchange system
The inside surfaces of the alveoli are kept moist by water
that diffuses out of the blood. The walls of the alveoli
are only one cell thick, and many small blood capillaries
surround them.

Unit 8: Structure and functions of the human gas exchange system 81

 Experiment 8.1
Dissect a lung.
You will need: a dissecting set; plastic sheeting; a hand lens; a lung of a goat, sheep or cow (with the
trachea and bronchi intact); water; a container; a towel; soap; disinfectant; rubber tubing
Procedure
1. Wash the lungs carefully with enough water to remove the blood. Do not allow water to enter the trachea.
2. Place the lungs on a piece of plastic sheeting on a bench. Position the lungs so that you can see the tubes
leading into them. You may have to cut away some pieces of flesh to fully expose the lungs.
3. Use Figure 8.3, above, to identify the various parts of the lungs.
4. Insert the rubber tubing into the trachea. Take a deep breath, and blow into the lungs very hard. Do you
notice any movement of the lungs? Describe this movement. Do you think your lungs behave in a similar
way when you breathe in? Explain your answer.
5. Examine the sides of the trachea and bronchi very closely. Do you see the rings on the trachea and
bronchi? What colour are these rings? Next, feel the sides of the trachea and bronchi, and then the
surface of the lungs. Do you notice any differences between them? Describe these differences.
6. The thin layer of skin covering the lungs is called the pleural membrane. What do you think is the
function of this membrane?
7. Bend the trachea until the open end faces downwards, and then let it go. Was it easy to bend? What
happened to the trachea when you let go? Next, try to close the trachea by squeezing it with your fingers,
and describe what you feel. What happens to the trachea after you stop squeezing it? What function do
the rings have?
8. Cut off one bronchus from the trachea to separate a lung. Next, cut along the bronchus until you expose
the inside of the lung. Use the hand lens to see whether the bronchus divides further into smaller tubes.
What are these sub-divisions of the bronchus called? What other details inside the lung have you
observed? Describe the inside of the lung.
9. Figure 8.3, on page 86, shows the human lung in detail. Could you see this much detail when you
examined the lung? Why can you not see the alveoli?
10. Put the lungs and other parts into the container and bury them in the ground. Carefully wash the bench
and plastic sheeting with soap, and then disinfect them.
11. Wash your hands thoroughly with soap.

Table 8.1 describes the functions of the different parts of the human gas exchange system.
Table 8.1. Functions of parts of the human gas exchange system
Part Functions
Nasal passages • Hairs in the nostrils trap dust and other small particles
• Mucus lining the nasal passages traps germs
Pharynx Warms and moistens the air entering the lungs as the air passes over blood vessels
Epiglottis Stops food and liquids from going into the trachea during swallowing
Trachea and • Provide an open passage for air to enter and leave the lungs
bronchi • Mucus lining the inside walls traps dust and germs
• Move mucus, which contains dust and germs, to the pharynx, using hair-like structures (cilia)
that line the inside walls
Alveoli Enable the exchange of gases between the blood passing through the lungs and the air in the lungs

82 Topic 2: Organisation and maintenance of life

 Self assessment 8.1
1. Draw a labelled diagram of the human lungs.
2. Describe the function of each of the following:
a) rings of cartilage
b) mucus inside the trachea and bronchi.
3. What are alveoli?
4. The inside of the lung is spongy. Explain the word ‘spongy’.
5. Copy the table below, and then complete it.
Part Functions
Trachea
Rings of cartilage in the bronchi
Cilia in the nasal passage

8.2. Functions of the parts of the human gas exchange system

In humans, gas exchange takes place in two places: in the alveoli in the lungs and in the cells of the body.
Gas exchange in alveoli
Air, which contains oxygen, is breathed into the lungs. Oxygen moves from the alveoli into the blood in
the capillaries that surround the alveoli. Carbon dioxide moves out of the blood into the alveoli. Carbon
dioxide is breathed out.

blood capillaries

alveolus

pulmonary
arteriole pulmonary venule

movement of oxygen rich

blood
movement of air passage in bronchiole
blood rich in CO2

Figure 8.4: Structure of the alveoli

Unit 8: Structure and functions of the human gas exchange system 83

Gas exchange in cells
Blood containing oxygen flows from the heart to the body cells. Oxygen molecules move by
diffusion from a high concentration in the blood towards a region where there is less oxygen inside
the cells. Inside the cell, oxygen is used in the process of respiration. Carbon dioxide is made during
respiration in the cells. This means that there is a high concentration of carbon dioxide molecules
inside the cells. Carbon dioxide moves out of the cells into the blood where there is a lower carbon
dioxide concentration.
deoxygenated blood
returning to the
heart

oxygenated blood oxygen

flow carbon dioxide
from the heart
Figure 8.5: Gas exchange in a cell of the body

Experiment 8.2
Make a model to demonstrate breathing.
You will need: rubber bands or string; a glass rod; a rubber sheet of a size that will cover the bottom of a
bell jar; a bell jar; two balloons; a Y-shaped tube; a rubber bung or cork
Procedure
1. Using a rubber band, tie the glass rod to the rubber sheet. Secure the rubber sheet around the open
end of the bell jar using rubber bands. The rubber sheet represents the diaphragm.
2. Tie a balloon around each arm of the Y-shaped tube. Push the other end of the tube through a
rubber bung or a cork. The balloons represent the lungs and the Y-shaped tube represents the
trachea and bronchi. Assemble the apparatus as shown in Figure 8.6, below.
3. Pull the rubber sheet downwards using the glass rod. This represents an inhalation. Note what
happens to the balloons when the rubber sheet is pulled downwards. Explain what happens.
4. Push the rubber sheet upwards using the glass rod. This represents an exhalation. Note what happens
to the balloons when the rubber sheet is pushed upwards. Explain what happens.
A    Air in B Air out
glass tube (trachea)

bell jar (thorax)

airtight space
(thoracic cavity)
glass tube (bronchus)

balloon (lung)
rubber sheet (diaphragm)

glass rod
Pull down Push up

Figure 8.6: Experiment to demonstrate inhalation (A), and exhalation (B)

84 Topic 2: Organisation and maintenance of life

 Exercise
Work in pairs.
1. Use a microscope to examine the microscope slides that your teacher will give you. You can also use
the micrographs in Figure 8.7 if you do not have slides.
2. Make a labelled drawing of what you see. What magnification did you use?

A B.
Figure 8.7: Micrographs showing alveolar cells (A) and ciliated epithelium (B)

Checklist of learning (Unit summary)

In this unit, I have learned that:
Gas exchange is the movement of gas molecules across a surface or membrane which is called the
gas exchange surface.
The movement of gas molecules takes place by diffusion.
All organisms need to make energy through respiration, so they need oxygen and they produce
carbon dioxide.
In humans, gas exchange takes place inside the lungs and in the cells of the body.
The human gas exchange system consists of the nostrils, nasal passages, trachea, bronchi,
bronchioles and alveoli.
The walls of the alveoli are only one cell thick; the alveoli are surrounded by small blood capillaries.
Air, which contains oxygen, is breathed in; oxygen molecules diffuse through the walls of the alveoli
into the blood.
Blood that contains oxygen flows to the cells of the body; oxygen molecules diffuse across the cell
membrane into the cell, where they are used for respiration.
Carbon dioxide diffuses out of the cells into the blood.
Blood that contains carbon dioxide flows into the lungs; carbon dioxide molecules diffuse through
the walls of the alveoli into air in the lungs, and are breathed out.

Unit 8: Structure and functions of the human gas exchange system 85

End unit assessment
Choose the correct answer.
1. What are the tiny sacs in the lungs called?
A bronchi B alveoli C capillaries
2. What happens during gas exchange in the lungs?
A Oxygen passes into the blood and carbon dioxide passes out of the blood.
B Oxygen passes out of the blood and carbon dioxide passes into the blood.
C Oxygen and carbon dioxide pass into the blood.
3. Which structures does the trachea lead to in the lungs?
A pleural membranes B bronchioles C bronchi
4. The alveoli are suited for gas exchange because they have:
A a small surface area B a large surface area C walls that are many cells thick
5. The cilia in the air passages:
A trap dust B trap bacteria C trap dust and bacteria
6. Explain the difference between:
a) gaseous exchange and breathing
b) diffusion and breathing.
7. List the pathway for air from the nose into the lungs.
8. Name two places where gas exchange takes place in humans.
9. a) What type of cells line the trachea?
b) How are these cells specialised for their function?
10. Research gaseous exchange in the following animals:
a) insects
b) fish
c) spiders.

86 Topic 2: Organisation and maintenance of life

 UNIT 9 Tropic responses

Key unit competence At the end of this unit, I should be able to:

To be able to explain • Recall that plants have a root system

a plant’s response to • Identify the parts of the shoot that respond to light
light and gravity and • Define phototropism as a response in which parts of a plant grow
explain the importance towards or away from the light source
of tropic responses in • Explain that gravitropism is a response in which parts of a plant grow
plants. towards or away from gravity
• Describe the change in shape of the shoot and root tips when exposed
to light and ground level
• Explain the importance of phototropism and gravitropism in plants
• Carry out investigations showing the response of a plant shoot towards
light and gravity
• Observe and illustrate plant shoots growing toward stimuli of light
and gravity
• Show that plants respond quite differently compared to animals
• Appreciate the importance of tropisms in plants
• Show patience and perseverance when carrying out experiments that
take a long time to get results.

Introductory activity
Think back to the structure of a flowering plant. Then, talk about these
questions.
1. What do you do when you see a fierce dog charging at you? Why and
how?
2. When you touch a hot object, you directly remove the hand from it.
B
Why?
3. Look at the plants A and B on the left. According to you, what caused
the plant in picture A to bend? Why? The next picture shows a
germinating seed, why the shoot and radical grown as you see it in the
picture? How do we call these kinds of responses? Do you now have
an idea what this unit is about?

Unit 9: Tropic responses 87

9.1. Meaning and types of tropism
Activity 9.1

1. Name two types of root systems.

2. Give two functions of roots.
3. In what ways are roots well suited to their functions?

In Unit 1, you learnt that all living things need to respond to their environment.
This response is known as sensitivity. It is one of the characteristics of living
organisms. Organisms are sensitive to a stimulus (plural = stimuli). Light
is an example of a stimulus. When we go into bright light, the pupils of our
eyes get smaller, to protect the eye. The response to a stimulus involves many
different parts of an organism, such as the sense organs and nervous system.
Animal responses to stimuli are easy to see, as they are quick. The animal’s
sense organs and nervous system are involved. Plants do not have sense
organs or a nervous system, but they still need to respond to changes in
their environment. For example, they need to grow towards light and water.
Although plants cannot move from one place to another, they can move
their stems, roots, leaves and flowers towards or away from a stimulus. This
movement takes place by growth. For example, shoots grow upwards towards
light, and roots grow downwards towards water.
The word ‘tropism’ refers to plant growth towards or away from a stimulus.
When part of a plant grows towards a stimulus, this is called a positive
tropism. When a plant part grows away from a stimulus, this is called a
negative tropism.
In this unit, you will learn about two types of tropisms: phototropism and
gravitropism.
Stimulus Tropism
Light Phototropism
Gravity Gravitropism or geotropism
Chemical Chemotropism
Water Hydrotropism
Touch Thigmotropism

Phototropism
‘Photo’ means light. Plants can respond to the stimulus of light. This is called
phototropism. Their shoots grow towards the light. For example, if you leave
a plant near a window, the stem will start to bend towards the light. We say
that the plant is positively phototropic.
There exist two types of phototropism:
- Positive Phototropism: Stem tip growing toward the light
- Negative Phototropism:Root tip growing away from the light Figure 9.1: Plants grow
towards light.

88 Topic 2: Organisation and maintenance of life

The importance of phototropism is that ithelps leaves be in the best position
possible to receive enough light for photosynthesis.

Experiment 9.1
Demonstrate phototropism in plants.
You will need: two bean plants; cotton thread; ink; a ruler; a cardboard
box; a pair of scissors
Procedure
1. Mark the stem of both plants at two-millimetre intervals using cotton
that has been dipped in ink. See Figure 9.3.
2. Put one plant in a place where it can get light on all sides. Or, place it ink marks
on a clinostat, if your school has one. 2 mm apart
3. Make a slit in the cardboard box so that light can get in. Place the
second plant inside the box.
4. Make sure the plants are watered and leave them for a few days.
Questions
1. Examine the plants. In which direction did the plant grow that had
received:
a) light on all sides Figure 9.2: Mark the bean
b) light from one side? plants at two-millimetre
2. Describe the growth of a stem using the words ‘phototropic’ and intervals.
‘positive’.
shoot radicle
Gravitropism (Geotropism)
Gravitropism also called geotropism is the response of plants’ stems and
roots to the effect of gravity. Gravity is a downward pull towards the centre
of the Earth. Plant stems grow upwards, against gravity. They are negatively
Figure 9.3: Plant roots grow
gravitropic. However, plant roots grow downwards, in the same direction in
downwards, in the same direction
which gravity acts. We say that they are positively gravitropic. as gravity.
If a seedling is planted on its side, the radicle, or first root, will start to grow
downwards and the shoot will grow upwards.
The importance of gravitropism is that it pulls roots down to anchor a plant
and roots can get needed water and minerals.

Experiment 9.2
Demonstrate gravitropism in plants.
You will need: bean seeds that have been soaked in water overnight; paper
towels; elastic bands; marker pens; four glass jars; a pot plant

Unit 9: Tropic responses 89

 damp paper
towel Procedure
1. Fold each paper towel into a narrow strip that is 12 cm long (see
Figure 9.5). Make about 15 strips.
seed
2. Moisten each strip with water, so that it is damp.
Roll up 3. Place one seed on the end of each strip and roll it up. Wrap an
elastic band around the seed to keep it inside the paper towel.
tube
4. Place the pot plant on its side and put it into a dark cupboard for
Figure 9.4: Rolling seeds into a few days.
a paper towel 5. Leave the seeds for a few days, but keep them damp with water.
6. Choose the twelve seedlings that have grown the longest roots
and shoots. Do not remove the seedlings from the paper towels.
jar 1 7. Label the jars 1, 2, 3 and 4, and then do the following (see
Figure 9.6):
a) Place three seedlings into jar 1 with the roots facing upwards.
jar 2
b) Place three seedlings into jar 2 with the roots pointing
sideways to the right.
c) Place three seedlings into jar 3 with the roots facing
downwards.
d) Place three seedlings into jar 4 with the roots pointing sideways
to the left.
8. Check the seedlings every second day for ten days. Examine the
jar 3 roots and record your observations in a table like this one.

jar 4 Date Observations

Jar 1 Jar 2 Jar 3 Jar 4
Roots facing Roots Roots Roots
upwards facing facing facing
sideways to downwards sideways to
Figure 9.5: Position of the the right the left
seedlings with the roots
facing in different directions.

Questions
1. What did you notice about the direction in which the seedlings’
roots and stems grew?
2. Describe the seedlings’ root and stem growth using the words
‘gravitropic’, ‘positive’ and ‘negative’.
3. a) What happened to the growth of the pot plant?
b) Can you explain why the pot plant grew like this?
c) Explain why the pot plant was put into a dark cupboard.

90 Topic 2: Organisation and maintenance of life

9.2. Why do plants respond to light and gravity?
Activity 9.2

Work in pairs.
1. Your teacher will show you a plant that shows another type of tropism: the plant responds to touch.
a) How does the plant respond when something touches it?
b) Make a drawing to show how the plant responds.
2. Research other types of plant responses, for example, hydrotropism, chemotropism and
thigmotropism. Write up your findings using these headings: Stimulus; Name of tropism; Positive
response of plant part; Negatice response of plant part.

Plants need light for photosynthesis.

Photosynthesis is a process in plants that is used
to make food using light energy, carbon dioxide
and water. The green pigment, chlorophyll, is also
needed. Near the tips of plant shoots, there are
special chemicals that are sensitive to light. These
chemicals cause shoots to grow towards light.
Plant roots grow downwards into the soil to find
water and minerals. There are special cells near
the tips of roots that cause the root to grow in the
direction of gravity.
Some plants respond to other stimuli besides light
and gravity. One of these stimuli is touch. This
is called thigmotropism (see Figure 9.7 and 9.8).
In the next activity, you will research other plant Figure 9.6: A climbing plant responds to touch by growing
tendrils towards the place where it touches a structure.
responses.

Self assessment 9.1

1. Give the meaning of these words:
a) tropism c) response
b) stimulus d) phototropism.
2. Give one reason why plant shoots respond to:
a) light b) gravity.
3. Make a labelled drawing to show how the
shoot and root grow in a seedling.

Figure 9.7: When touched, the feathery leaves

of the shrub Mimosa pudica curl inwards.

Unit 9: Tropic responses 91

Checklist of learning (Unit summary)
In this unit, I have learned that:
All organisms respond to changes in their environment; sensitivity is a characteristic
of life.
Plants respond to stimuli by growing towards or away from the stimulus; this is called
a tropic response.
Plants’ response to light is called phototropism, and their response to gravity is called gravitropism.
Plant stems grow towards light; they are positively phototropic.
Plant roots grow downwards in the same direction as the force of gravity; they are positively
gravitropic.
Plant shoots grow towards light so that they can receive more light for photosynthesis.
Plant roots grow into the soil so that they can absorb water and mineral salts.
Other examples of tropisms include hydrotropism (the response to water), chemotropism (the
response to chemicals) and thigmotropism (the response to touch).

End unit assessment

1. Do plants and animals respond to changes in their environment in the same way? If you answer no,
then explain how their responses differ.
2. Complete the sentences below using these words: towards, phototropism, roots, stimulus,
negatively.
a) The growth of a stem ______________________ or away from a light ______________________ is
called ______________________.
b) Plant stems are ______________________ gravitropic.
c) Plant ______________________ are positively gravitropic.
3. Explain why plants respond to light.
4. Draw a diagram to show what will happen if a pot plant is left to grow on its side for
a while.
5. Explain how you would demonstrate that roots are positively gravitropic. Use the following
headings: Materials; Method; Results (what you expect to happen); Conclusion (what you
found out).

92 Topic 2: Organisation and maintenance of life

 UNIT 10 Skeletal systems of organisms

Key unit competence At the end of this unit, I should be able to:

To be able to analyse • Recall the different types of skeleton in organisms

the different types of • List the characteristics of hydrostatic skeletons, exoskeletons and
skeletons and identify endoskeletons
the main parts of a • Explain the role of the different types of skeletons
human skeleton. • State the functions of the human/ mammalian skeletal system
• Describe the general structure of the human skeleton and identify
the bones of the central and peripheral parts
• Recognise the different parts of the human skeleton from models in
class
• Practice illustrating and labelling the major bones
• Research on the skeleton and presentation of the findings
• Take care of your bones so your skeleton stays strong and healthy.

Introductory activity

Think back to what you have already learnt about skeletons and answer the following questions:
1. What structures support our bodies?
2. What is attached to these structures that help us to move?
3. Which organs in our bodies need to be protected?
4. Do all organisms have bones? If not, how are their bodies supported?
5. Are different animals able to move differently? If so, how do they move? Are their skeletons adapted for
this movement? If so, think of ways in which they are adapted.

Figure 10.1: Humans have a strong skeleton that helps them to move.

Unit 10: Skeletal systems of organisms 93

 10.1. Types of skeletons
Activity 10.1

flatworm 1. Look at the pictures or specimens of different animals. Are their

skeletons the same?
2. How each animal is able to move and how its skeleton helps it to do
this?
3. Find an earthworm and an insect (e.g. a locust, grasshopper or
cockroach). Place your specimens in glass jars that have had holes
punctured in their lids for air. Place some moist soil into the jar with
the earthworm, so that it does not dry out. All specimens must be alive
earthworm and unharmed. Your teacher will show you pictures of a small frog,
bird or mammal.
4. Observe the locomotion of each animal, and discuss the structures
that enable each animal to move.
slug 5. Return the specimens to the places where you collected them.

All animals need a support system that can help them stay upright and move.
This support system is the skeleton. Animals in water need less support than
Muscles squeeze animals on land because the water supports them as well. On land, animals
the fluid inside the need to overcome the force of gravity to be able to move. They also need
body
layers of
protection for the soft tissues and organs inside their bodies.
muscle A skeleton is a structure on the inside or the outside of the body that
gut gives support to the body and protects the softer parts of the organism.
coelom There are three types of skeletons: hydrostatic skeletons, exoskeletons and
filled with endoskeletons.
fluid Hydrostatic skeletons
cross-section of an Hydrostatic skeletons are found in animals that have soft bodies. Such
earthworm skeletons are not made up of hard structures such as bones. Instead, these
Figure 10.2: Soft-bodied animals have a liquid skeleton. There is fluid inside their bodies. Muscles in
animals have hydrostatic the animal’s body can work against the fluid that keeps their bodies firm.
skeletons. Examples of animals with hydrostatic skeletons include earthworms, slugs,
snails, jellyfish, leeches and flatworms.
Exoskeletons
Some animals have a skeleton on the outside of their bodies. This is called an
exoskeleton (‘exo’- means ‘outside’). This type of skeleton is found in insects,
crabs, spiders and scorpions.
These are some of the features and functions of an exoskeleton.
• An exoskeleton lies outside the muscles of an animal’s body.
• It is made by the animal’s skin.
• It protects the internal body parts from injury.
• It provides protection against predators.
Figure 10.3: Insects moult so • Its colour may help the animal to hide or to attract a mate.
that they can get bigger. • It is waterproof, and it prevents the animal from losing too much water.

94 Topic 2: Organisation and maintenance of life

Exoskeletons are not made from living cells, so they do not grow with the
animals. As an animal grows, the non-living skeleton needs to be replaced.
The animal sheds its protective outer skeleton and a new, larger skeleton
takes its place. This is called moulting. The new skeleton is soft just after
moulting. This makes the animal easy prey for predators at this time.
At certain places in the exoskeleton, there are joints. In these places the
exoskeleton is soft and flexible. Muscles are attached to different places on
the joints.
Figure 10.4 shows different animals that have an exoskeleton.

Insects have hard exoskeletons. Crabs have an exoskeleton Spiders have a leathery Scorpions have an exoskeleton
that is shaped like a shield. exoskeleton. similar to that of insects.

Figure 10.4: Examples of different animals that have an exoskeleton

Endoskeletons
Some animals, such as humans, have a skeleton inside their body. This is called A
an endoskeleton (‘endo’ means ‘inside’). In most animals, the endoskeleton is
made up of bones and cartilage. The endoskeleton is living tissue.
An endoskeleton supports an animal’s body. Animals need to move from
one place to another in search of food or a mate. An endoskeleton provides a
place where the muscles can be attached. Some bones are fused together and
other bones form joints that help the animal to move. As the bones are on the B
inside of the body, they grow as the animal grows. This means that animals
that have an endoskeleton do not need to moult.
Animals that have endoskeletons include fish, frogs, birds, reptiles and
mammals. All of these animals have a backbone. All animals that have a
backbone are vertebrates. Animals with endoskeletons nearly all have the
same basic parts: a backbone, four limbs (arms and legs), a skull and ribs. C
Some animals have bones in their skeletons that are adapted to suit their way
of life. For example, the bones of a bird are adapted for flying.

Figure 10.5: Animals with

endoskeletons: a bird (A),
a fish (B) and a frog (C)

Unit 10: Skeletal systems of organisms 95

Characteristics of hydrostatic skeletons, exoskeletons and endoskeletons
Table 10.1 shows the characteristics of the three skeleton types you have learnt about.
Table 10.1 Characteristics of hydrostatic skeletons, exoskeletons and endoskeletons
Hydrostatic skeleton Exoskeleton Endoskeleton
• Inside the body • Outside the body • Inside the body
• Made of fluid • Made of non-living material • Made of living material
• Muscles around the fluid • Muscles are attached to the inside of the • Muscles are attached to the
can press against it skeleton outside of the skeleton
• Does not grow, so it needs to be shed to • Grows inside the animal
enable the animal to grow

Self assessment 10.1

1. Name two animals that have a hydrostatic skeleton.
2. What makes up a hydrostatic skeleton?
3. Name three different animals that have an exoskeleton.
4. a) What is ‘moulting’?
b) Explain why animals that have an exoskeleton have
to moult.
5. How do animals that have an exoskeleton move?
6. Write down two ways in which an exoskeleton helps an animal.
7. What do we call endoskeletons?
8. Describe the animals with endoskeletons and give examples.

10.2. The human skeleton

Activity 10.2

Think back on what you learnt and answer the following:

1. Are there bones in the head? If yes, name them.
2. Are there bones in thorax? If yes, name them.
3. Are there bones in the legs? If yes, name them.

The human endoskeleton is made up of 206 bones. The human skeleton is different to all other animal
skeletons because humans walk on two legs and other animals usually walk on four legs. The bones in the
skeleton are made from living cells. They can break and grow.

96 Topic 2: Organisation and maintenance of life

There are two basic types of bone tissue
• Compact bone
• Homogeneous Spongy bone

Bones are classified basing on their shapes

1.Long- bones are longer than they are wide (arms, legs)
2. Short- usually square in shape, cube like (wrist, ankle)
3.Flat- flat , curved (skull, Sternum)
4.Irregular- odd shapes (vertebrae, pelvis)

Unit 10: Skeletal systems of organisms 97

The bones of the human skeleton
Look at Figure 10.6. It shows the bones that make up the human skeleton. The human skeletal system is
divided into the central skeleton and the peripheral skeleton, which you will learn about in the sections to
follow.
skull
orbit
nose
lower jaw
cervical
vertebra
clavicle

scapula
sternum

rib
thoracic
vertebra
humerus lumbar
vertebra
ulna
pelvis
sacrum
radius coccyx

carpals

metacarpals
femur
phalanges
patella

tibia

fibula

tarsals
metatarsals
phalanges

Figure 10.6: The bones of the human skeleton

98 Topic 2: Organisation and maintenance of life

Central skeleton
The central skeleton consists of the skull, the joined bones
vertebral column and the thoracic cage.
Skull
The skull is made up of different bones all fused, or eye socket
joined, together to form a type of case for the brain.
The skull has openings for the eyes and nose. It cheek bone
protects the brain, the eyes, and the parts of the ears
that are inside the skull. upper jaw bone

Vertebral column teeth

This is the part of the skeleton that enables us to walk
upright, bend over, crouch, bend and turn. It is also
lower jaw bone
called the backbone. It is made up of lots of bones, Figure 10.7: The structure of the skull
called vertebrae. The vertebral column works like
a chain. Each vertebra can only move a little, but
as a whole it moves better than one solid bone. The
vertebral column needs to be strong and flexible, to
give us good support. From the side, it is S-shaped.
The bones of the vertebral column form a hollow tube vertebrae
through which the spinal cord passes. The spinal cord
is the part of the brain that extends into the back. The
vertebrae protect the spinal cord.
The vertebral column also supports the thorax (chest),
and the ribs are attached to it.
Thoracic cage
The thoracic cage consists of 12 pairs of ribs that are Figure 10.8: Vertebrae of the
attached to the vertebral column at the back and a backbone
bone called the sternum in front of the chest. Ribs
are thin bones. They play a very important function
in protecting the heart and lungs. There are muscles
between the ribs that help us to breathe in and out.
sternum

ribs

Figure 10.9: The ribcage protects the

heart and lungs.

Unit 10: Skeletal systems of organisms 99

 clavicle Peripheral skeleton
(collarbone)
The peripheral skeleton consists of the upper and lower limbs, pectoral girdle
and pelvic girdle.
Upper limbs
humerus The arms are the upper limbs. The upper limb is made up of the humerus,
scapula radius and ulna, carpals, metacarpals and phalanges (see Figure 10.10
(shoulder alongside). The bones of the upper arm are joined to the lower arm at the
blade) elbow joint. The lower arm is joined to the hand by the wrist joint. Each hand
has five fingers. The arms and hands are used to do countless activities, such
as grasping, writing and eating.
radius Pectoral girdle
ulna
The bones of the upper arm are attached to the pectoral girdle. The pectoral
carpals girdle is made up of the collarbone (clavicle) and shoulder blade (scapula)
metacarpals (see Figure 10.10). The collarbone is a long, thin bone below the front of the
phalanges neck. The shoulder blades are the large, flat bones that you can see in the
(fingers)
back view of the skeleton. These bones help to protect the heart and lungs.
Figure 10.10: Bones of the Together with the collarbones, the shoulder blades form joints for the bones
pectoral girdle and arm of the upper arm.
Pelvic girdle
pelvic This is made up of a ring of bones and includes the base of the vertebral
girdle
column (see Figure 10.11, on the next page). The hip bones are large flat
bones. They protect the internal parts of the body that are important for
reproduction. The hip bones form joints for two legs.
Lower limbs
femur
The legs are the lower limbs. The bones of the lower limbs include the
femur, patella, tibia and fibula, tarsals, metatarsals and phalanges (see
patella Figure 10.11). The bones of the upper leg are joined to the lower leg at the
(kneecap) knee joint. The lower leg is joined to the foot by the ankle joint. Each foot
has a heel and five toes. The legs are the organs of locomotion.

tibia
fibula

Side view of foot

phalanges
(toes)

tarsals
metatarsals Figure 10.11. Bones of the pelvic girdle and legs

100 Topic 2: Organisation and maintenance of life

 Self assessment 10.2
1. What is the main function of the skull?
2. How many ribs are there in the human skeleton?
3. a) What is another name for the vertebral column?
b) What are the bones that make up the vertebral
column called?
4. Which bones protect the heart and lungs?
5. Which bones form joints with the hip bones?
6. What is the function of the backbone?
7. List the bones of each of the following:
a) thoracic cage
b) pectoral girdle
c) lower limbs.
8. The diagram below shows part of a skeleton. Provide labels for bones A to D.
A

B
D

10.3. Functions of the skeleton

Activity 10.3

You will need: a variety of different bones; a sharp pencil; a

ruler; an eraser; drawing paper
1. Make a drawing of the bone
shown in Figure 10.12, alongside.
2. Make a neat labelled drawing to show the structure of the
pectoral girdle and the pelvic girdle.

Figure 10.12 A human femur

Unit 10: Skeletal systems of organisms 101

Table 10.2 summarises the functions of the skeleton.
Table 10.2. Functions of the skeleton
FUNCTION DESCRIPTION
Support. As most animals with an endoskeleton live on land, they need support for the mass of their
bodies
Protection The bones of the skeleton are strong, and so they protect important organs inside the body.
The bones of the skull protect the brain, the vertebrae protect the spinal cord, the ribs
protect the heart and lungs, and the pelvis protects some of the digestive organs and the
female reproductive organs.
Movement The skeleton helps the animal to move. It is used for the attachment of muscles. Joints help
parts of the skeleton to bend; for example, the elbow joint makes it possible to bend the
arm.
Production of The bone marrow manufacture the blood cells. The red blood cell are made in red bone
blood cells marrow while the white bone marrow are made in white bone marrow
It gives the The body shape depends on the shape of the bones.
shape of the
body
Storage of Huge number of minerals in the body are stored in bones. Examples: Calcium 99%,
minerals Phosphorus 89%, and it stores also small amount of Magnesium and Sodium

Self assessment 10.3

1. Give a definition for each of these terms.
a) exoskeleton c) endoskeleton
b) joint d) hydrostatic skeleton
2. Give an example of an animal that has:
a) an exoskeleton b) a hydrostatic skeleton.
3. List the bones in the:
a) upper arm   b) pectoral girdle   c) pelvic girdle.
4. Give three functions of the human skeleton.

102 Topic 2: Organisation and maintenance of life

Case study
Looking after our skeletal system
Work in groups. Read the Case study below, and then answer
the questions.
Care of our bones
There are three things that we need for healthy bones: calcium, exercise
and sunshine.
Calcium
Dairy products are rich in
Calcium is an important building block for bones. It gives them their calcium.
strength. We measure healthy bones by their density. Bones with a high
density are strong. Bones store calcium that can be used when we do
not have enough calcium in our diet. We must replace the used calcium
to keep our bones strong. Different people need different amounts of
calcium, depending on their age, gender and stage of life. Bone building
takes place mainly during childhood and early adulthood. Bone calcium
decreases as we age. We should exercise and eat calcium-rich foods to
keep our bones strong.
Exercise
When we exercise, our muscles pull on our bones. This helps to build Exercise builds healthy,
healthy, denser bones. Bones respond better to weight-bearing exercises dense bones.
such as walking, stair climbing, jogging and aerobics. Exercises that offer
resistance to movement like weight training and high impact exercises
like skipping and jumping are also good for healthy bones.
Sunshine
Vitamin D forms in our skin when it is exposed to sunlight. It is difficult
to take in enough vitamin D from our diet alone. Vitamin D improves
bone strength by increasing the amount of calcium that is absorbed into
the body.

Questions
1. What can you do to make sure that you have strong bones. The body makes vitamin D when
2. Talk about your diets, the amount and type of exercise that you do, the skin is exposed to sunlight.
and the amount of time you spend outside in the sun.

Unit 10: Skeletal systems of organisms 103

Checklist of learning (Unit summary)
In this unit, I have learned that:
Animals have skeletons to support their bodies.
There are three types of skeletons: hydrostatic skeletons, exoskeletons and endoskeletons.
Hydrostatic skeletons are found in soft-bodied animals and consist of fluid.
Exoskeletons are found in animals such as insects, crabs and scorpions and are on the outside of the
animal’s body.
Endoskeletons are found inside the bodies of animals, for example, humans.
The human skeleton consists of a central and peripheral skeleton.
The central skeleton is made up of the skull, vertebral column and thoracic cage.
The peripheral skeleton is made up of the upper and lower limbs, pectoral girdle and pelvic girdle.
A skeleton is important as it provides support, protects important organs and enables the animal to
move.
We need to look after our bones by eating enough calcium, getting enough exercise and making sure
that we are sometimes exposed to the sun.

End unit assessment

1. What structures make up an endoskeleton?
2. An exoskeleton does not grow, so how do animals with an exoskeleton grow?
3. Name two soft internal parts of the body that ribs protect.
4. What is the name of a place where two bones meet?
5. Which part of the skeleton protects the brain?
6. Which bones make up the vertebral column?
7. What is the function of the backbone?
8. Give three reasons why animals with an exoskeleton are able to move.
9. The table shows how the amount of calcium in a person’s diet relates to their bone density.
Amount of calcium in diet (mg/day) Bone density (units)
25 500
30 600
40 800
60 1,000

a) What do you notice about the relationship between the amount of calcium a person eats
and their bone density?
b) Name and explain two other factors that affect a person’s bone density.
10. Give functions of the human skeleton.
11. a) What is synovial joint?
b) What function does each of the following havein a joint.
(i) A tendon (ii) A ligament (iii) Synovial membrane.
(iv) Synovial fluid. (v) A cartilage.

104 Topic 2: Organisation and maintenance of life

Formal assessment for topic 2
1. a) A
 learner views a specimen using a microscope. The eyepiece objective lens used is
10× magnification, and the nosepiece objective lens is 40× magnification. What is
the total magnification? Show your working out. (3)
b) A learner draws a seed that measures 1,5 cm in length. Her drawing is 9 cm in
length. What is the magnification of the drawing? (1)
2. Complete the table below by filling in the missing information.
Plant cell Animal cell
Shape
Outer covering
Organelles
Vacuoles

3. a) Define each of these words.
i) tissue ii) organ (2 × 2 = 4)
b) Identify the tissues in A and B.
A B

 (2 × 2 = 4)
c) Give one function of each tissue you gave in your answer to question b). (4)
4. Provide labels for parts 1 to 7 in the drawing of the respiratory system.

5
2

3 6
4

7
(7)
5. The table below shows the amount of food nutrients in 100 g of breakfast cereal.
Food nutrient Amount per 100g
Protein 15,9 g

Formal assessment 105

 Carbohydrate 53,5 g
Fat 20,2 g
Vitamin C 3 mg
Iron 5 mg
Vitamin B 4 mg

a) Which food nutrient is present in the cereal in:

i) the highest amount    ii)   the lowest amount? (2)
b) Name two vitamins that are in the cereal. (2)
c) Name one mineral that is found in breakfast cereal. (2)
d) Name the deficiency disease that results if a person does not eat enough:
i) iron ii) vitamin C. (2)
6. A learner did some food tests on a sample of food. He recorded his results in a table.
Name of reagent used Colour before test Colour after test
Iodine Orange Blue-black
Ethanol Clear Clear
Sodium hydroxide and Blue Purple
copper sulphate
a) Which food nutrients are:
i) present in the sample   ii)   absent from the sample? (3)
b) Describe how the learner tested the food sample for the presence of starch. (6)
7. Conduct research to find out why cells in organisms are specialised, and then
present your findings in a report.
a) Under the heading ‘Cell specialisation in animals’:
• Give two examples.
• Make a labelled drawing of each example.
• Discuss how the specialisation makes the cells well suited
to their functions.
b) Under the heading ‘Cell specialisation in plants’:
• Give two examples.
• Make a labelled drawing of each example.
• Discuss how the specialisation makes the cells well suited
to their functions. (18)
Total marks: 68

106 Formal assessment

 TOPIC

3 Health and disease

Sub-topic Infectious and non-infectious diseases

Unit 11 Classification of diseases
Sub-topic Reproductive health
Unit 12 Human reproductive system
Unit 13 Puberty and sexual maturation
Unit 14 Reproduction, pregnancy and
childbirth

Figure 11.1: Rwandans need to grow up fit and healthy so that they can become strong adults that help Rwanda grow.

107
 UNIT 11 Classification of diseases

Key unit At the end of this unit, I should be able to:

competence • Define good health as a state of mental, social and physical wellbeing
To be able classify • Define disease as any physical or mental disorder or malfunction
diseases and explain with a characteristic set of signs and symptoms
ways of preventing the • Explain how infectious diseases (cholera, tuberculosis, malaria,
spread of infectious Ebola, HIV/AIDS) are spread
diseases. • Explain ways in which infectious and non-infectious diseases can be
prevented
• Classify diseases into infectious, non-infectious, inherited,
degenerative, social, mental, eating disorder and deficiency diseases
• Adopt and encourage the practices that enhance good health
• Be aware that the clearing of bushes and grasses in the habitats of the
anopheles mosquitoes and the treatment of the stagnant water for the
anopheles larvae are necessary for eradicating malaria.

Introductory activity
Some people are healthy, but others are sick. Sometimes sick people need to go to hospital. In groups, talk
about these questions.
1. What is good health?
2. Name some diseases that occur in your community.
3. Discuss whether or not people get these diseases from other people.
4. Talk about ways to prevent sick people from spreading disease.
5. Work out a definition for the terms ‘disease’ and ‘good health’.

Figure 11.2: Many people go to the local clinic when they are sick.

108 Topic 3: Health and disease

11.1. Health and disease
Activity 11.1

You may have heard the saying ‘prevention is better than cure’. Describe five good practices that can
prevent a person from getting a disease.

When we say that a person is in ‘good health’, we mean that the person
is in a good mental, physical and social state.
The word ‘disease’ refers to a physical or mental disorder or malfunction
that has a particular set of signs and symptoms. A person that has a
disease is sick and may need to be treated by a health worker.
Some diseases do not cause symptoms, so we may not know that the
person is sick. However, other diseases cause a clear set of signs and
symptoms.
Figure 11.3: A nurse taking care of
Practices that promote good health a patient in hospital

We can follow these good practices to prevent disease and stay

healthy.
• Eat a balanced diet.
• Eat at regular intervals.
• Get enough sleep.
• Maintain good hygiene of the body, clothes, the home and foods.
• Drink safe water.
• Exercise regularly.
• Avoid eating too much salt.
• Wash your hands before each meal and after going to the toilet.
Self assessment 11.1
1. List five types of diseases.
2. Explain the meaning of each of these terms.
a) infectious disease
b) hypertension
c) immunisation
d) haemoglobin
3. Design a poster to show how washing your hands helps to prevent the spread of infectious diseases.
Include information about how and when we must wash our hands.

Unit 11: Classification of diseases 109

Classfication of diseases
There are two main types of diseases: infectious and non-infectious
diseases.
11.2. Infectious diseases
Activity 11.2

1. What is an infection?
2. a) Find out the names of at least five infectious diseases.
b) Research how each of these diseases is transmitted,
and then suggest preventive measures for each one.
tuberculosis malaria Ebola fever HIV/AIDS

3. The wall chart below shows some ways to prevent cholera.

Analyse it, and then answer these questions.
a) Use the wall chart to suggest ways to prevent cholera.
b) Suggest any two other ways to prevent cholera.
c) How can we help someone with cholera?

Infectious diseases are diseases that are passed on, or transmitted, to a

person by another organism, such as a bacterium or virus. Organisms
that cause disease are called pathogens. They attack the body’s cells or
release poisons called toxins. Nearly all pathogens are micro-organisms,
so they are microscopic. When a person has an infectious disease, he or
she can spread it to another person. Table 11.1 lists some examples of
pathogens and the infectious diseases that they cause.
Figure 11.4: Malaria is caused
Table 11.1. Pathogens and infectious diseases by a parasite (plasmodia)
Type of pathogen Examples of infectious diseases that is transmitted to humans
when a mosquito (anophele)
Bacteria Cholera, tuberculosis, typhoid fever bites.

Protists Malaria, sleeping sickness

Fungi Thrush, athlete’s foot, ringworm

Viruses HIV/AIDS, influenza, chicken pox, measles

Parasitic worms Guinea worm disease, bilharzia

110 Topic 3: Health and disease

 Figure 11.6: Athlete’s foot is an
Figure 11.5: Ringworm is
infectious fungal skin disease that
caused by a fungus that forms a
occurs mainly on the feet.
distinct ring on the skin.

The spread and prevention of infections

You have learnt that infectious diseases can be transferred, or transmitted,
from one infected person to another. Another name for an infectious
disease is a communicable disease. Communicable diseases are
transmitted by infections.
Infectious diseases can spread through:
• water (e.g. cholera); these are called waterborne diseases
• air (e.g. measles, tuberculosis)
• blood (e.g. HIV/AIDS)
• sexual intercourse (e.g. gonorrhoea).
There are several ways to prevent the spread of infectious diseases,
including the following:
• Inform and warn people about a particular infectious disease, for
example, cholera or Ebola fever. Offer health education at all levels of
the country.
Figure 11.7: A patient
• Improve public hygiene measures; for example, remove the remains of
suffering from tuberculosis
dead animals, have rubbish collection points around schools and cities, (TB), which is an infectious
and provide safe drinking water and sewage systems. disease
• Isolate or quarantine infected people in places where they have little
contact with people other than health workers.
• Immunise people against infectious diseases. This is an injection that
helps our bodies to fight a disease.
• Build more healthcare centres.

Unit 11: Classification of diseases 111

 Self assessment 11.2
1. What are the vectors of infections diseases and give examples of diseases each.
2. Copy the table below, and then complete it.
Name of disease Causes
Sickle cell anaemia
Allergy
Stroke
3. Follow the steps on the next page to prepare an oral rehydrating solution (ORS) that you can use as
a first aid to help a patient suffering from cholera. ORS is a mixture that is made from clean water,
table salt and sugar.

You will need: sugar (table sugar); table salt; two teaspoons; a clean one-litre bottle with a lid; boiled
water; a clean measuring cylinder or any suitable container; soap
Procedure
1. Wash your hands with soap and water. Wash the teaspoons, bottle and measuring cylinder with soap
and clean water and leave them to dry.
2. Put 750 ml of boiled water into the bottle.
3. Measure out one level teaspoonful of table salt. Remove half of the salt from the spoon. Add the
remaining half (2,5 ml) to the water in the bottle.
4. Measure out one level teaspoon of sugar (use the other teaspoon to level the sugar with the edge of
the spoon). Add the teaspoonful of sugar (about 5 ml) to the 750 ml of water in the bottle.
5. Repeat step 4 until you have added six level teaspoonsful (30 ml) of sugar.
6. Put the lid on the bottle and shake it until all the sugar and salt have dissolved. You have now
prepared an oral rehydration solution (ORS). Taste it; it should be no more salty than the tears from
your eyes.

11.3. Non-infectious diseases

Activity 11.3

Kalisa and Nyirasafari still have their grandparents, who are 90 years old. They like to visit their grandparents.
One day, their grandmother fell and broke her arm. The doctor said that her arm broke because of osteoporosis,
which is an age-related disease.
1. Do research in the library or on the Internet, and then explain the words ‘ageing’ and ‘osteoporosis’.
2. What are the signs of ageing?
3. Is ageing a non infections disease? Explain
4. With examples, what do we call non infections disease?

Non-infectious diseases cannot be passed from one person to another by living organisms. They develop
because the body does not work properly, or they may be caused by a person’s lifestyle. Examples include sickle
cell anaemia, allergies, ageing, osteoporosis, cancer, cardiovascular diseases, eating disorders, deficiency
diseases and mental illnesses.

112 Topic 3: Health and disease

Sickle cell anaemia
Sickle cell anaemia is a disease of the red blood cells. Sickle-shaped red blood
cells are unable to carry oxygen as well as normal red blood cells can. They
can also easily get stuck in narrow blood vessels. This prevents oxygen from
reaching the cells of the body.

sickle-shaped red
blood cells

normal red blood cells

Figure 11.8: Sickle-shaped red blood cells and normal red blood cells
Sickle cell anaemia is caused by a change in a gene that makes haemoglobin,
the molecules that give your blood its red colour. Haemoglobin helps red
blood cells to carry oxygen from the lungs to all the cells in the body.
The sickle cell gene is passed from one generation to the next. If both a
mother and father have the sickle cell gene and pass it to their child, then
their child will have sickle cell anaemia. If only one parent has the sickle
cell gene and it is passed to his or her child, then the child will be able to
make both normal and sickle cell haemoglobin. This child will be a carrier
of the sickle cell gene. There are tests available to find out if a child has
sickle cell anaemia. Although
there is no cure for sickle cell anaemia, medications can relieve
the symptoms.
Allergies
An allergy is a reaction by the immune system to a substance in the
environment. A substance that causes an allergy is called an allergen.
Some people are allergic to certain foods, for example, nuts or shellfish, or
to substances in the environment, for example, dust, pollen or pesticides.
When someone is allergic to something, they sneeze, get itchy eyes, get a
rash or have swelling on their body. There are different medicines available
to treat allergies.
Ageing
Figure 11.9: As you get older,
Ageing is the process of becoming older. Many physical, mental and social
organs and systems are likely to
changes take place. For example, older people do not walk or think as fast as suffer from age related diseases.
younger people do. Ageing is a natural process that we will all go through. Nelson Mandela lived to a very old
age of 95, and then he passed on
due to age related diseases.

Unit 11: Classification of diseases 113

Osteoporosis
Osteoporosis is a bone disease that occurs mostly in women after menopause. The bones become very porous,
and they break easily and heal slowly. The disease can lead to curvature of the spine after the vertebrae
collapse.
Cancer
Cancer is a non-infectious disease that develops when cells of the body do not divide normally. Cancer can
start almost anywhere in a person’s body. Cancer may lead to the growth of tumours. There are many ways
to treat cancer, but it is important to find it early on.
Cardiovascular diseases
These are diseases of the heart and blood vessels. Examples include coronary heart disease (CHD) and
strokes. CHD can lead to a heart attack, which is when the heart muscles do not get enough oxygen. A stroke
occurs when too little oxygen is transported to the brain cells.
Eating disorders
Eating disorders lead to diseases that are caused by undereating or overeating. You have already learnt about
some diseases that occur from undereating, such as kwashiorkor and marasmus.
Obesity is caused by eating more food calories than are used up by physical activity. Excess energy is stored
as fat. Obesity is becoming more common as people eat more unhealthy ‘fast’ foods and spend less time
exercising.
Deficiency diseases
Deficiency diseases occur when a person’s diet lacks certain vitamins and minerals. For example, a
deficiency of vitamin C can lead to scurvy. You learnt about some of these diseases in Unit 7 in Table 7.4,
on page 79.
Mental illnesses
Diseases that affect a person’s mind include depression, anorexia and schizophrenia. There are many ways
to treat these diseases. Table 11.2 summarises different types of diseases and gives examples of each disease.
Activity 11.4

1. Look at the diseases given in the blocks below.

high blood pressure (hypertension) tuberculosis (TB) cystic fibrosis obesity

kwashiorkor malaria HIV/AIDS anaemia

Put each disease into one of these categories:

a) infectious disease
b) non-infectious disease
c) inherited disease
d) eating disorder
e) deficiency disease.
2. Name four other diseases, and classify each disease into one of the groups above.

114 Topic 3: Health and disease

Table 11.2. Different diseases and their descriptions
Type of disease Description Examples
Infectious disease A disease caused by an invading organism; it can be Cholera, malaria, tuberculosis,
transmitted from one person to another Ebola
Non-infectious disease A disease that cannot be transmitted from one person Stroke, sickle cell anaemia,
to another scurvy, high blood pressure
Inherited disease A disease caused by a genetic fault that may be passed Sickle cell anaemia,
from parents to children haemophilia, cystic fibrosis
Degenerative disease A gradual decline in function, often associated with Arthritis
ageing
Social disease Drug dependence, often caused by social pressure and Alcoholism
certain types of social behaviour
Mental illness A disorder of the mind Anorexia, schizophrenia
Eating disorder A disease caused by undereating or overeating Anorexia, obesity
Deficiency disease A disease caused by a poor diet that lacks one or more Scurvy, rickets
essential nutrients

Checklist of learning (Unit summary)

In this unit, I have learned that:
A person’s health includes their mental, social and physical well-being.
There are two main types of diseases: infectious and non-infectious diseases.
Infectious diseases are caused by pathogenic organisms, and they can be transmitted from one
person to another unless preventive measures are taken.
Preventing the spread of infectious diseases is important and includes quarantine
and immunisation.
Cholera is an infectious disease that is caused by a bacterium and spread through contaminated
water.
Some diseases are non-infectious; they include sickle cell anaemia, allergies, ageing, osteoporosis,
cancer, cardiovascular diseases, eating disorders, deficiency diseases and mental illnesses.

Unit 11: Classification of diseases 115

End unit assessment
Look at Table 11.2, on previous page, and then answer these questions.
1. Name:
a) three infectious diseases
b) two inherited diseases
c) one degenerative disease.
2. Give the meaning of the following terms:
a) degenerative disease
b) social disease
c) deficiency disease.
3. Which vitamin is deficient when a person has:
a) scurvy
b) rickets?
4. Look at the photographs below, and then comment on the health of each child.

116 Topic 3: Health and disease

5. Ask your partner to look at the pie chart, and then to tell you, according to the data presented,
which disease causes:
a) the most deaths b) the fewest deaths.

cancers

cardiovascular disease

chronic respiratory disease

diabetes

digestive diseases

other non-infectious diseases

Number of deaths caused by the main non-infectious diseases worldwide

Source: http://www.who.int/gho/ncd/mortality_morbidity/ncd_premature_text/en
6. Describe to your partner two measures for preventing the spread of infectious diseases.
7. We often hear in the news that people in refugee camps die from cholera. Ask your partner to
explain factors that make cholera common in such camps.
8. a) Discuss with your partner the preventive measures the Rwandan government uses to eradicate
malaria.
b) Despite the measures taken by the government, malaria still causes the death of many
Rwandans. What factors are causing this failure to eradicate malaria?
9. The Rwandan government encourages its citizens to participate in sport. Discuss with your partner
the impact that sport can have on our health.

Unit 11: Classification of diseases 117

 UNIT 12 Human reproductive system

Key unit At the end of this unit, I should be able to:

competence • Describe the structure and function of the human sexual and
To be able to analyse the reproductive system
structure, functions and • List the external and internal organs of the male reproductive system
processes of the human • List the external and internal organs of the female reproductive system
sexual and reproductive • Explain the production of sex cells: gametogenesis
system and relate to the • Compare the size and shape of ovum and sperm
understanding of sex • Explain the role of hormones in growth, development and the
and gender. regulation of the reproduction organs and sexual functions
• Define sex determination
• Analyse how culture, tradition and religious practices influence one’s
thinking about sex, gender and reproduction
• Appreciate that gender stereotypes are not biologically determined
and can be challenged.

Introductory activity
In groups, talk about these statements.
1. What do you see on following figures?
2. How does a female getpregnant?
3. What is the importance of reproduction?

Figure 12.1: Male sperm cells and a female egg.

118 Topic 3: Health and disease

12.1. Reproductive organs
Activity 12.1

When you observe the boy and the girl, directly you see or you imagine some of their parts that make
the difference between them.
1. List the parts that make the differences between boy and girl.
2. In the reproductive system, the male and female organs play their role. Which one involves more
than another and why?

The reproductive organs in humans are structures that are involved in reproduction. You learnt in Unit 1 that
reproduction is a characteristic of living things. In this unit, you will learn about the structure and functions
of the male and female reproductive systems.
The reproductive organs are important for:
• producing male and female sex cells, or gametes
• transporting the male sex cells to the female sex cell
• producing chemicals called hormones
• enabling a baby to grow inside the female’s body.
The male and female human reproductive systems have external and internal parts.

A. Male reproductive organs

The male reproductive organs are the testes,
penis, epididymis, sperm ducts, Cowper’s
glands, seminal vesicles, prostate gland and
urethra.
External organs
There are two testicles, or testes, which are
surrounded by a sac called the scrotum. The
testes produce male gametes, called sperm,
and secrete the male hormone testosterone.
The penis is important for the transfer of sperm
to the female during sexual intercourse. The penis
penis is covered by skin called the foreskin.
This is removed during circumcision. foreskin
scrotum
Side view

Figure 12.2: The external male reproductive structures

Unit 12: Human reproductive system 119

Internal organs
Table 12.1 describes the internal male reproductive structures.
Table 12.1 The internal male reproductive structures

Structure Description
Epididymis A tightly coiled tube 5 to 6 metres in length. It stores sperm, and it is the place where sperm
cells mature.
Seminiferous tubules Long, coiled tubes inside the testes. They contain germinal cells that can divide to produce
sperm cells.
Sperm ducts A sperm duct transports sperm from the epididymis to the urethra. The sperm duct is also
called the vas deferens. There are two sperm ducts, one from each testis, that open into the
urethra.
Cowper’s glands Secrete mucus that lubricates the urethra.
Seminal vesicles Produce and release seminal fluid into the sperm duct. This fluid helps to neutralise the
acidity that the sperm will meet inside the female’s reproductive structures. There are also
nutrients in the seminal vesicle secretion that provide energy for the sperm.
Prostate gland The prostate gland surrounds the urethra. It also secretes a fluid into the urethra as the
sperm passes through during ejaculation. This fluid helps to neutralise the acidity of urine
residue that the sperm will meet inside the urethra. The secretions of both the seminal
vesicles and the prostate gland improve the motility, or movement, of the sperm.
Urethra A passage for both urine and semen, at different times. Semen is a fluid that contains
sperm, neutralising chemicals and nutrients.

seminal vesicle

sperm duct prostate gland

urethra

epididymis

testis
penis
scrotum
Front view
Figure 12.3: The internal male reproductive structures

120 Topic 3: Health and disease

B. Female reproductive organs

The female reproductive organs include the vulva, ovaries, oviducts, uterus, cervix and vagina. The female
reproductive system produces female gametes, called ova (singular = ovum) inside the ovaries. The ovaries
also produce the female sex hormones oestrogen and progesterone.
External organs

The external organs are collectively called the vulva.

Table 12.2 describes the different parts of the vulva.

Table 12.2. The parts of the vulva

Structure Description
Labia majora An outer fold of skin that covers the labia minora.

Labia minora An inner fold of skin that protects the openings of the urethra and
vagina.
Clitoris A female erectile organ that is important during sexual intercourse.

Vaginal opening The opening into the vagina is important during sexual intercourse and
during childbirth. The vaginal opening in a virgin girl is covered by a
membrane called a hymen. During sexual intercourse, the hymen is
broken.

Unit 12: Human reproductive system 121

Internal organs
Table 12.3 describes the internal organs of the female reproductive system.
Table 12.3. Th.e internal organs of the female reproductive system
Structure Description
Vagina A narrow, muscular tube. It is also known as the birth canal as it is a passage for the birth of a baby. The
vagina has folded walls that can be easily stretched. It has a rich supply of mucus for lubrication. During
sexual intercourse the penis is inserted into the vagina to deposit the male gametes.
Cervix At the top of the vagina is a narrow opening called the cervix. The cervix is a ring of muscle that is
important during childbirth.
Uterus The uterus is a pear-shaped organ where the baby develops. It has thick, muscular walls that are lined
with a mucous membrane called the endometrium. During menstruation, the endometrium is shed. The
muscular walls of the uterus contract powerfully during childbirth to help with the delivery of the baby.
Ovaries The two ovaries are about three centimetres in length. They are inside the abdomen, one on each side
of the uterus. They are attached to the uterus by ligaments. Every 28 days an ovum is released from one
ovary. This is called ovulation.
Oviducts The oviducts are tubes that extend from the ovaries to the uterus. The ovum is released into a funnel at
the end of each oviduct. The oviducts are sometimes called Fallopian tubes. The ovum is moved along the
oviduct towards the uterus by the action of tiny hairs called cilia. Fertilisation takes place in the oviduct.

uterus
oviduct
ovary
womb
(uterus) oviduct

bladder ovary
ligament which
muscular wall holds ovary in
cervix position
of womb

rectum
cervix
anus
urethra vagina
vagina
Side view Front view
Figure 12.4: The internal organs of the female reproductive system

122 Topic 3: Health and disease

 Self assessment 12.1
1. Copy the table, and then complete it using what you have learnt about the female reproductive
system.
Structure Function

2. a) Name two female reproductive hormones.

b) In which part of the female reproductive system are these hormones produced?
3. Give a reason for each of the following:
a) the uterus has powerful muscles
b) the oviducts are lined with ciliated epithelium.

12. 2. The process of sperm and ovum production.

Activity 12.2

Study and discuss the following structures.

Figure 12.5: Structure of a sperm cell Figure 12.6: Structure of an ovum

a) Which of the above structures is a male or female sex cell?
b) Use a Venn diagram to compare the two cells

Introduction
Gametogenesis is the process involved in the formation of gametes. In human being, the formation of female
gametes is known as oogenesis or ovogenesis and occurs in the ovaries while the formation of male gametes
is called spermatogenesis and occurs in the testes.

Unit 12: Human reproductive system 123

Gametogenesis
This is the process by which gametes are formed. It occurs in the gonads.
In humans, the female has different types of gonads from the male. These are located in different parts of the
body.
In the females, the gonads are known as ovaries and they lie in the dorsal abdominal cavity below the kidneys.
In the females, the ovary produces the ova through the process called oogenesis orovogenesis.
In the males, the gonads are called testes and they are found hanging outside the body.
In the males, the testes produce spermatozoa through the process called spermatogenesis.
Spermatogenesis.
Sperms are produced in seminiferous tubules inside the testes.The walls of the seminiferous tubules contain
cells called the germinal epithelium that produce sperm cells by meiosis.

The process includes the following stages:

• Diploid epithelial cells in the seminiferous tubules of the testes undergo mitosis producing
spermatogonia (single: spermatogonium).
• The spermatogonia divide by mitosis to produce primary and secondary spermatocytes.
• The spermatocytes divide by meiosis to produce haploid spermatids.
• The spermatids develop into spermatozoa.

124 Topic 3: Health and disease

Oogenesis or ovogenesis.
This is the formation of the egg cell or ovum.
The ova begin to develop before a baby girl is born. About 70000 potential ova are present at birth, though
only about 450 will mature within the ovaries.
Ovogenesis is similar to spermatogenesis and has the following stages

Table 12.4 lists the differences between the processes that produce sperm and ova. cell division as it is shown
here below
Table 12.4. Differences between the processes that produce sperm and ova
Production of sperm Production of ova
Occurs in the testes of the male Occurs in the ovaries of the female
Many sperm per germinal cell are One egg cell per germinal cell is produced
produced
Sperm are small but motile Ova are large but non-motile
Starts at puberty and does not stop Starts in the embryo and stops at menopause
Sperm can survive for about four An egg cell can survive for about two days inside the female's body
days inside the female's body

12.3. The role of hormones in reproduction

Activity 12.3

1. Why some persons may reproduce at very early age and other at late age?
2. Is it possible to accelerate the time of reproduction? How?

Male and female hormones are important in the growth, development

and regulation of reproductive organs and their functions. Table 12.5, on the next page, lists some of the
hormones in males and females, and describes where the hormones are made and their functions. You will
learn more about these hormones in Unit 13.

Unit 12: Human reproductive system 125

Table 12.5. Hormones in males and females
Place where made Functions
Male hormone
Testosterone Testes • Involved in the development of male characteristics during puberty
• Involved in the production of sperm
Female hormones
Follicle stimulating In a part of the brain Involved in the production of ova
hormone (FSH) called the hypophysis
Luteinising In the hypophysis Causes ovulation to take place
hormone (LH)
Oestrogen Ovaries • Involved in the development of female characteristics during
puberty
• Involved in the development of an ovum in
the ovary
• Plays a role in the menstrual cycle and pregnancy
Progesterone Ovaries Plays a role in the menstrual cycle and pregnancy

Self assessment 12.2

1. Make a neat, labelled drawing of a sperm cell and an ovum.
2. Name one male hormone.
3. a) Name four female hormones.
b) Give the functions of each female hormone you named.

12.4. Sex determination

Activity 12.4

Work in pairs, and role play how a person’s sex is determined by chromosomes. Show how male and female
gametes from a couple determine the sex of their baby.
You could use different coloured cards. Females would have two cards of the same colour and males would
have two cards with different colours. Place two different coloured cards in one bag and cards of the same
colour in another bag. Randomly pick one card from each bag. Do you have a male or female? Work out the
chance of having a male or female baby.

Looking at the outside of the body, a person’s sex, is indicated by his or her external reproductive organs.
These include the penis and testes of males and the vagina of females. However, the sex of a person is actually
controlled by chromosomes in the sex cells, or gametes. Chromosomes are structures that are found in the
nucleus of all cells. They give an organism its characteristics. A person’s sex is determined when fertilisation
takes place.
In human cells, there are 22 pairs of non-sexual chromosomes and one pair of sex chromosomes. It is the sex
chromosomes that determine the sex of an individual. Girls have two X chromosomes in all their cells while
boys have one X and one Y chromosome. There is only one sex chromosome in the sex cells.

126 Topic 3: Health and disease

There can only be an X chromosome in ova but some sperm will have an X chromosome and some will have
a Y chromosome. When the ovum fuses with a sperm once again there will be two sex chromosomes. If an
ovum with an X chromosome fuses with a sperm that also contains an X chromosome, then the baby will be
a girl (XX). If an ovum with an X chromosome fuses with a sperm that contains a Y chromosome, then the
baby will be a boy (XY).

Parents

egg sperm

Gametes

female sex chromosome

combinations possible
male in new individual

Figure 12.7: An individual’s sex is determined by chromosomes.

Self assessment 12.3

1. State two ways in which a person’s sex is indicated.
2. What is a chromosome?
3. Which two chromosomes determine a person’s gender?
4. A male sperm has a Y chromosome and it fuses with the female ovum. Will the baby that results be a
boy or a girl?
5. Explain why it is the father who determines the sex of a baby.

12.5. Influence of culture, tradition and religion on sex, gender and reproduction
Activity 12.5

1. Give examples of characteristics and behaviours that are seen as ‘male’ and ‘female’ in your community.
Discuss whether these characteristics and behaviours are biological or social.
2. In African families, girls and boys often grow up together. However, they have different tasks to do and
they are treated differently by others. The table below lists different attitudes towards boys and girls.
Copy the table and complete it by putting a tick ( ) next to a statement when it applies to boys or girls
and a cross ( ) when it does not.

Unit 12: Human reproductive system 127

 3. Explain your opinions.
Statement Boys Girls
Should learn all domestic tasks, e.g. cooking and mopping.
Should be allowed to visit friends and relatives freely.
Should look down as a sign of politeness whenever he or she is talking to an adult.
Should not cry, even at a mourning ceremony such as a funeral.
Should be clever from early childhood.
Should not be allowed to take part in certain sports, e.g. boxing, karate or bicycle riding.
Should inherit his or her parents’ wealth.
Should stop going to school if the family cannot afford it.
Should be judged by society when he or she dresses in an unacceptable way.
Should receive presents from the family on the day of his or her wedding.

Most societies expect people of a particular gender to perform certain tasks. This happens for cultural reasons
or as a result of customs, traditions and religious views. For example, hunting was traditionally assigned to
men and mourning to women. As our society has changed, the role of the different genders has also changed.
Gender equality means that males and females are equal. In the activity you will discuss this important issue.

Self assessment 12.4

1. Look at the picture of the family below, and then assess how they live in terms of gender equality.
Then, answer the questions.

An example of gender roles in a family

1. Would you like to be a husband or a wife like the people shown in the picture? Would you like to
have a wife or a husband like that? Why or why not?
2. Talk about how you could encourage gender equality in your community. For example, you could do
a drawing, tell a story or write a poem.

128 Topic 3: Health and disease

Checklist of learning (Unit summary)
In this unit, I have learned that:
The reproductive organs are important for producing sex cells, transporting the male sex cells to the
female’s sex cell, producing hormones, and enabling a baby to grow inside the female’s body.
The external male reproductive organs are the testes and penis; the internal organs are the
epididymis, sperm ducts, Cowper’s glands, seminal vesicles, prostate gland and urethra.
The female external reproductive organ is the vulva; the internal organs are the ovaries, oviducts,
uterus, cervix and vagina.
The production of sex cells is called gametogenesis; the sperm are produced in the testes, and the ova
in the ovaries.
The sex of a baby is determined by chromosomes and occurs at fertilisation.
The sex chromosome in the sperm can be either X or Y; the sex chromosome in all ova is X.
Hormones play a major part in the growth, development and regulation of the reproductive organs
and sexual functions.
Cultural, traditional and religious practices have an important influence on one’s thinking about sex,
gender and reproduction.

End unit assessment

1. The diagrams below show the human male and female reproductive systems. Look at the diagrams,
and then answer these questions.
a) Provide a heading for each diagram (A and B).
b) Name parts 1 to 8 in diagram A.
c) Name parts 9 to 12 in diagram B.
d) Suggest the function of each part in diagram A.
e) Suggest the function of each part in diagram B.

A B
4 10
3
5
6
2 9

1 11
7
12
8

2. On your own, write a paragraph in which you discuss how cultural, traditional and religious
practices influence peoples’ ideas about sex, gender and reproduction. Hand it in to your teacher
for evaluation.

Unit 12: Human reproductive system 129

 UNIT 13 Puberty and sexual maturation

Key unit At the end of this unit, I should be able to:

competence • Define puberty and how it affects the body emotionally and
To be able to analyse the physically
physical, emotional and • State the key emotional and physical changes during puberty
social changes related to • Describe the hormones that bring about these changes
puberty. • Describe the various phases of the menstrual cycle
• Analyse the physical, emotional, and social changes associated with
puberty between girls and boys
• Show respect for diversity in when and how peers develop and
change during puberty.

Introductory activity
Think about changes that occur in boys and girls during their teenage years. Then, answer these questions.
1. Are teenagers treated differently to people of other ages? If so, talk about ways in which they are treated
differently.
2. Are girls and boys treated differently from one another when they are teenagers? If so, how?
3. Are there educational opportunities for teenagers in Rwanda? How do these compare to opportunities
that were available ten years ago?
4. Do teenagers have any responsibilities? If so, what does society expect of them?

Figure 13.1: The teenage years are fun filled, but teenagers also have responsibilities.

130 Topic 3: Health and disease

13.1. Puberty
Activity 13.1

Observe the figure 13.2 and answer the following questions:

1. What are the differences in females of different age?
2. What are the differences in males of different age?
3. What are the differences between childhood and puberty in terms of external characteristics?

Puberty is the time when boys and girls become sexually mature. Biological changes take place in the person’s
body in preparation for reproduction. Puberty involves both physical and emotional changes. Some changes
can be stressful, but it helps to realise that puberty is a natural step in the development of every person.
Puberty occurs at different times for different people, and it has different effects on boys and girls. Puberty
occurs sometime between the ages of nine and sixteen.
All organisms have features or characteristics that make them male or female. Primary sexual characteristics
are physical characteristics that indicate whether a person is male or female. These characteristics are present
from birth, for example a penis or vagina. Secondary sexual characteristics develop only at puberty.
In males, the testes begin to produce the hormone testosterone during puberty. It brings about the development
of male secondary sexual characteristics. In females, the ovaries begin to produce the hormone oestrogen
during puberty. It brings about the development of female secondary sexual characteristics.

Adulthood
Adulthood
Puberty Puberty

Childhood Childhood

Females Males
Figure 13.2: Puberty brings about physical changes in girls and boys.

Unit 13: Puberty and sexual maturation 131

Table 13.1, on the next page, shows some secondary male and female sexual characteristics that appear
during puberty.
Table 13.1. Secondary sexual characteristics
Changes in boys Changes in girls
• Facial, pubic and underarm hair starts to grow • Pubic hair starts to grow
• Voice deepens • Breasts enlarge
• Body size increases and becomes more muscular • Fatty tissue is deposited on the hips and thighs
• Sex organs increase in size • Hips broaden
• Sperm are produced in the testes • Menstruation starts
• Acne may occur • Ova are released from the ovaries
• Acne may occur
Hormones and puberty
Male and female hormones differ, and they have a major influence on the emotional and physical changes
that occur over a person’s lifetime.
At puberty, the hypophysis secretes two hormones in both boys and girls: follicle stimulating hormone (FSH)
and luteinising hormone (LH). These hormones cause the testes in boys and the ovaries in girls to develop.
As the testes develop, they produce testosterone, the main male sex hormone that leads to the development
of male secondary sexual characteristics. Inside the ovaries, oestrogen and progesterone start to be produced.
They lead to the development of female secondary sexual characteristics.

13.2. The menstrual cycle

Activity 13.2

The picture alongside shows the menstrual cycle. Analyse the picture, and then answer the questions.
1. How many days does one menstrual cycle last?
2. What happens on the first day of the menstrual cycle?
3. According to the diagram, how many days does menstruation last?
4. What happens during ovulation?
5. On which days can a female fall pregnant if she has unprotected sexual intercourse? Explain your
answer.
6. What happens if the egg cell is not fertilised?

The menstrual cycle is a series of changes that the female body goes through to prepare for possible
pregnancy. It is a pattern of changes
in the ovaries and the secretion of different hormones over about
28 days. Different people have menstrual cycles of different lengths.
The menarche is the first menstrual cycle that occurs at puberty when the ovaries begin to release ova. The
menstrual cycle continues until menopause, when the ovaries gradually become inactive between 40 and
54 years of age.

132 Topic 3: Health and disease

 Egg is released

Thickness of uterus liningº

(ovulation
phase) Uterus
Menstruation
occurs Uterus lining Uterus lining is lining
(menstrual builds up maintained (luteal phase) breaks
phase) (follicular down
phase)

uterus lining
Day 1 Day 4 Day 14 Day 28
Figure 13.3: The events of the menstrual cycle
Phases of the menstrual cycle
The menstrual cycle can be divided into different phases, based on events that occur within the female
reproductive system. These phases are the menstrual phase, follicular phase, ovulation phase and
luteal phase.
Menstrual phase
The menstrual phase, or menstrual period, starts from the first day of menstrual bleeding. On day 1 of the
phase, the thickened lining, or endometrium, of the uterus begins to pass out of the body through the vagina.
A normal menstrual period can last from three to seven days.
Follicular phase
During the follicular phase, one of the ovaries gets ready to release an egg. At the same time, the uterus starts
producing a new lining to prepare for a possible pregnancy.
Last day
28
27
Ovulation phase
26
Day 1
During this phase, an ovary releases an egg into 2
3
25
the oviduct. This is called ovulation. Menstruation
4
The egg then moves down the oviduct towards 24
Uterus lining
the uterus. Immediately after ovulation, a continues to
thicken
5
23 Uterus
woman can fall pregnant by having unprotected lining shed
6
sexual intercourse. 22

Luteal phase 7

21
During this phase, the lining of the uterus Ovulation
Uterus
lining 8
Egg dies if
becomes thicker. If an egg is fertilised by a 20 not fertilised
starts
to grow
sperm it then attaches to the uterus lining and again 9

19
a pregnancy begins. If the egg is not fertilised A mature egg
10

or does not attach, the uterus lining begins to 18 released from

ovary 11
break down and bleeding occurs. 17
12
16
15 13
14

Figure 13.4: The menstrual cycle

Unit 13: Puberty and sexual maturation 133

 Self assessment 13.2
1. Explain the difference between primary sexual characteristics and secondary sexual characteristics.
2. Which hormones influence puberty in: a) boys   b) girls?
3. a) Copy Figure 13.4, on the previous page.
b) On what day does ovulation take place?
c) Does ovulation always take place on this day? Explain.
d) On which day does menstruation start?
e) Does menstruation always start on this day? Explain.
4. Explain: a) menopause  b) Follicular phase.

13.3. Social issues and puberty

Activity 13.3

1. What can be done to avoid early pregnancies?

2. Do you think all boys and girls have enough information to avoid pregnency in puberty? If no, how
can be done?

At puberty, boys and girls can produce a baby if they have unprotected sexual intercourse. However, they
are too young to manage the responsibilities of having a child. They will lose out on many educational and
career opportunities, which could affect their future lives negatively. The unintended pregnancy will also
cause family disruption. Rwandan society prepares boys and girls for their gender responsibilities. Adults
warn girls and boys about avoiding unintended pregnancies.
Self assessment 13.3
Discuss how an unintended pregnancy can disrupt the life of a teenage boy and girl.

134 Topic 3: Health and disease

Checklist of learning (Unit summary)
In this unit, I have learned that:
Primary sexual characteristics indicate a person’s gender and they are present
from birth.
Puberty is a time of sexual maturation that leads to physical and emotional changes.
Puberty is a time in a person’s life when he or she develops secondary sexual characteristics.
Puberty occurs at different times for different people, and it has different effects on boys and girls.
The menstrual cycle is a series of events that are controlled by hormones.
The menstrual cycle has four phases: the menstrual phase, follicular phase, ovulation phase and
luteal phase.
The menstrual cycle starts on the first day of menstruation and ends on the first day of the next
menstruation.
Some women experience certain symptoms before menstruation, for example, cramps, headaches,
diarrhoea or constipation, nausea, dizziness or fainting.

End unit assessment

1. Match the word in Column A with the correct definition in Column B.
Column A Column B
1.1 Ovulation A. Having a period
1.2 Menstruation B. The process in which a child’s body begins to change
into an adult’s body
1.3 Ovum C. The male gamete
1.4 Puberty D. Involved in the secretion of hormones
1.5 Sperm E. The release of an ovum from an ovary
1.6 Hypophyis F. An egg cell

2. A girl starts her period on 2 July. Her menstrual cycle is 29 days long. Work out when her next
period will be.

Unit 13: Puberty and sexual maturation 135

 UNIT 14 Reproduction, pregnancy and childbirth

Key unit At the end of this unit, I should be able to:

competence • Describe male and female reproductive systems
To be able to analyse the • Explain the process of fertilisation
process of reproduction, • Explain how a pregnancy occurs
pregnancy and • Describe the signs of pregnancy, and the stages of foetal development
childbirth. and childbirth
• Define maternal mortality and list major causes of maternal mortality
• Describe ways that poverty and gender inequality lead to death among
pregnant women and how these outcomes can be prevented
• List health risks associated with early pregnancy and birth
• Analyse using simulations of stages of pregnancy and discuss the signs
and behavioural symptoms of pregnancy
• Appreciate the importance of the steps that should be taken to promote
safe pregnancy and childbirth
• Show concern about maternal mortality as an issue in the region.
Introductory activity
1. Name two main functions of the human reproductive system.
2. During which time in a woman’s menstrual cycle is she most likely to fall pregnant after unprotected
sex?
3. Discuss how unintended pregnancy can occur.
4. What are the consequences of unintended pregnancies?

Figure 14.1: Pregnancy can be an exciting time.

136 Topic 3: Health and disease

 The male and female reproductive systems
In unit 12 you learnt about the male and female reproductive organs and
how they are involved in reproduction. Reproduction is the production
of offspring or new individuals from their parents. Human reproduction
is sexual reproduction, as it requires sex cells, or gametes, from male and
female parents. The gametes fuse, or join, to form a new cell. A new organism
develops from this cell.
The reproductive organs are important for two reasons: they play a role in
sexual intercourse and, in females, they provide a place for a new baby to
develop. You will find out about these two roles in this unit.
14.1. Sexual intercourse
Activity 14.1

By using internet and textbooks, search and explain the processes of sexual
intercourse and fertilization.

The male sex cells, or sperm, are produced in the testes of the male
reproductive system. So the sperm need to be transferred to the inside of the
female body to enable one of them to fuse with the ovum. This takes place
during sexual intercourse.
Sexual arousal occurs when a man and a woman interact and their senses
are stimulated. The pulse rate, breathing rate and blood pressure increases.
The male penis fills with blood and becomes erect. The external female
reproductive parts become sensitive to touch and the vagina secretes mucus
for lubrication during intercourse.
The erect penis is placed inside the vagina. In the male, the movement of
the penis inside the vagina stimulates a reflex and causes ejaculation. This is
a rhythmic muscular contraction of the male reproductive system from the
sperm tail left outside the ovum
testes to the penis. It results in the release of semen from the urethra. Male
male nucleus orgasm happens at the same time as ejaculation. In the female, the movement
of the penis to and from vaagina leads to orgasm. An orgasm is the peak of
sexual arousal and is a combination of pleasurable physical and emotional
sensations.

Fertilisation
During sexual intercourse, the male ejaculates between two and six millilitres
of semen that contains about 300 million sperm. Semen is deposited inside
the female vagina near the cervix. Sperm in the semen swim upwards into
female nucleus
the oviducts. If an ovum is in an oviduct, the sperm can reach it within five
Figure 14.2: Fertilisation is the
fusion of a sperm and an ovum to minutes.
form a zygote.

Unit 14: Reproduction, pregnancy and childbirth 137

The ovum is surrounded by a tough outer coat that makes it difficult for the sperm to penetrate into the
ovum. After a few minutes, the strongest sperm passes through the coat around the ovum and attaches to the
membrane. Only the head of the sperm penetrates the ovum; the tail stays outside. The nuclei of the ovum
and the sperm fuse; this is called fertilisation. The fertilisation event is called conception – a new human
being has been created. The new cell that forms after fertilisation is called a zygote.

Self assessment 14.1

1. List the parts of the male reproductive system in which:
a) sperm are produced
b) semen leaves the male body.
2. Write down the pathway of an ovum from the time it is released until it leaves the female body.
3. In which part of the female reproductive system do the following take place?
a) fertilisation
b) development of the foetus

14.2. Foetal development

Activity 14.2

By using internet and textbooks, search and explain the processes of Foetal development in placenta during
pregnancy.

After fertilisation, the zygote continues to divide. It divides into two cells, then four, then eight, and so on.
Eventually a ball of cells is formed. After about seven days, it develops into a fluid-filled cavity surrounded by
a single layer of cells.
The cilia move the ball of cells down the oviduct towards the uterus. After about ten days, the ball of cells
burrows into the wall of the uterus. This process is called implantation. There it continues to divide into
more specialised cells and an embryo is formed. From the eighth week until birth (around 40 weeks), the
developing organism is called a foetus.

138 Topic 3: Health and disease

 a)

ball of cells
attached to
the uterus
wall

zygote 2-cell 4-cell 8-cell stage 16-cell ball of cells foetus – feotus – foetus – foetus – 40
b. stage stage stage 8 weeks 12 weeks 20 weeks weeks

Figure 14.4: a) Implantation of the ball of cells, b) Development of the foetus over 40 weeks

The placenta
Part of the embryo forms a structure called the placenta.
The functions of the placenta are:
• to provide the foetus with nutrients
• to remove waste products from the foetus’ blood
• exchange oxygen and carbon dioxide between the foetus’ blood and the mother’s blood
• act as a filter for harmful substances, although some substances, such as nicotine, drugs and alcohol, as
well as viruses such as HIV, can pass through it and reach the foetus
• to secrete hormones.
There is no direct contact between the mother’s blood and the blood of the foetus. The umbilical cord
transports substances between the placenta and the embryo. The umbilical cord contains blood vessels and
it extends from an opening in the foetus’ stomach to the placenta.

placenta

umbilical cord
uterus wall

Figure 14.5: The position of the placenta

Unit 14: Reproduction, pregnancy and childbirth 139

 Self assessment 14.2
1. Define each of these words.
a) zygote
b) fertilisation
c) conception
d) placenta
2. a) List five functions of the placenta.
b) Explain why pregnant women should avoid drugs and alcohol during their pregnancy.

Signs of pregnancy
Pregnancy starts on the day of fertilisation. There are no signs of pregnancy at this time, but as time passes
the following signs appear:
• there is no menstrual period
• slight bleeding or cramping as the embryo implants in the uterus
• tender breasts
• extreme tiredness
• backache
• nausea or sickness
• needing to urinate more often
• headaches, due to the sudden rise of hormones in the body
• darkening of the skin around the nipples
• food cravings or aversions
• emotional sensitivity and outbursts, due to high hormone levels.
14.3. Process of childbirth
Activity 14.3

By using internet and textbooks, search and explain the process of Childbirth

Childbirth, which is also known as labour or parturition, brings pregnancy to an end. It results in one or
more newborn infants being expelled from a woman’s uterus. There are three stages of labour.
First stage (about 12 hours)
The cervix dilates, or widens, and the uterus begins to contract. Fluid called amniotic fluid is released. This
is sometimes called ‘breaking
of the waters’ and it signals that the second stage of labour is about
to begin.
Second stage (20 minutes to 1 hour]
The muscles of the uterus and abdomen contract to push the baby out of the uterus, cervix and vagina. This
is known as delivery of the baby. In normal childbirth, the head of the baby comes out first. The umbilical
cord is cut.

140 Topic 3: Health and disease

Third stage (10 to 30 minutes after birth)
The placenta is expelled from the woman’s body. The expelled placenta is known as the afterbirth.

Stage 1: Dilation of the

cervix

foetus uterus
uterus

cervix vagina

vagina
dilated cervix
umbilical cord umbilical cord

Stage 2: Birth of the baby Stage 3: Expulsion of the placenta

foetus cervix
uterus

umbilical
clamp

umbilical cord
The head
appears first vagina
placenta umbilical cord
Figure 14.6 Stages of childbirth
Problems during birth
If the mother or the baby experience difficulties during the birth, then a Caesarian section may be done.
This is a surgical procedure during which the doctor cuts through the abdominal wall and uterus to deliver
the baby.
According to the World Health Organization, every day worldwide 800 women die of causes related to
pregnancy or childbirth. This is called maternal mortality. Nearly all maternal deaths occur in developing
countries, and the incidence is higher in rural areas and among poorer communities.
Women die as a result of complications such as:
• severe bleeding after childbirth
• infections
• high blood pressure during pregnancy
• complications from delivery
• unsafe abortion.
Inadequate health care, lack of information, poverty, distance to travel to health clinics and cultural practices
are some of the reasons why women do not receive help during their pregnancy.

Unit 14: Reproduction, pregnancy and childbirth 141

Unintended pregnancy
An unintended pregnancy is any pregnancy that is unplanned or unwanted. Pregnancy in unmarried
women and pregnancy after rape are examples of unintended pregnancies.
Causes of unintended pregnancy include not using contraception or not using it properly,
contraceptive failure, lack of knowledge about sex and reproduction, lack of planning and rape.

Self assessment 14.3

1. Give the meaning of each of these terms.
a) embryo   b) zygote   c) labour
2. Distinguish between an embryo and a foetus.
3. List four complications that can occur during childbirth.
4. What is meant by an ‘unintended pregnancy’?

Design a poster for a clinic in Rwanda to display in their waiting room. Show the steps a pregnant
woman should take for a healthy pregnancy and childbirth.

14.4. Teenage pregnancy

Activity 14.4

Think about the following:

1. Events and circumstances that can bring about
unintended pregnancy
2. Consequences of teenage pregnancy
3. Reasons for maternal mortality.

Teenage pregnancy is pregnancy in girls under the age of 20. A girl can fall pregnant after puberty if she
has unprotected sexual intercourse. Every day in developing countries, 20 000 girls under the age of 18 give
birth.
Health risks associated with teenage pregnancy
Pregnant teenagers face many of the same problems as other pregnant women. However, teenage
pregnancy results in greater health risks to both the mother and baby. These include the risk of:
• the baby having a low birth weight
• the mother going into premature labour
• the mother dying as a result of complications during pregnancy or childbirth.
Other consequences of teenage pregnancy
As well as health risks, there are also emotional and socioeconomic consequences of teenage pregnancy. For
example, a girl may be excluded from her family and community after she falls pregnant. Teenage pregnancy
also affects girls’ education and income potential as they may be forced to drop out of school. This threatens
future opportunities and economic prospects.

142 Topic 3: Health and disease

According to the United Nations Population Fund (UNFPA), ‘Pregnancies among girls less than 18 years
of age have irreparable consequences. It violates the rights of girls, with life-threatening consequences in
terms of sexual and reproductive health, and poses high development costs for communities, particularly in
perpetuating the cycle of poverty.’
Teenage pregnancies can be prevented by sex education and access to birth control.

Figure 14.7: Teenage pregnancy has health, emotional and socio-economic consequences.
Steps to promote safe pregnancies and childbirth
Antenatal, or prenatal, care refers to looking after and protecting a pregnant woman and her foetus during
pregnancy and childbirth. The first few months of pregnancy are the most critical for the developing infant
because major steps in foetal development take place at this time.
A woman should take these steps to care for herself and her unborn child during pregnancy:
• As soon as she finds out that she is pregnant, she should see a doctor or health worker. She will be
given vitamins to take, such as folic acid, to reduce the risk of birth defects.
• She should rest often.
• She should eat a healthy, balanced diet.
• She should avoid foods that can cause food poisoning, for example, shellfish, as food poisoning can
cause miscarriage.
• She should avoid caffeine, alcohol and cigarettes. Cigarette smoking has been linked to a low birth
weight.
• She should not change cats’ litter boxes as she could get toxoplasmosis, which is a very serious illness.
• She should eat only well cooked meat as undercooked meat can contain harmful pathogens.
• She should arrange for a health worker to assist at the birth or arrange to go to a hospital for the birth.

Unit 14: Reproduction, pregnancy and childbirth 143

Postnatal care
Postnatal care refers to care of the mother and baby after childbirth. After the birth, the mother produces
breast milk. Breast milk is the ideal food for infants. It contains a perfect balance of proteins, carbohydrates,
fats, minerals and vitamins, and the infant can digest it easily. It also contains antibodies that boost the
infant’s immune system.
Postnatal care for the mother include provide to her with enough balanced meal, hygiene, avoid conflicts with
her; Postnatal care for the newborn include enough breast feeding, protection against bad wealth, pathogens,
parasites and diseases.

Checklist of learning (Unit summary)

In this unit, I have learned that:
Human reproduction is sexual reproduction as it requires gametes from male and
female parents.
The sex organs play two major roles: sexual intercourse and pregnancy.
Sexual intercourse occurs when the penis is inserted into the vagina and ejaculation, the release of
semen, takes place.
Fertilisation is the fusion of the egg and sperm nuclei in the oviduct to form a zygote.
After fertilisation, the zygote undergoes a series of cell divisions to increase the number of cells.
Implantation occurs when the embryo burrows into the wall of the uterus.
The symptoms of pregnancy include no menstrual period, nausea, fatigue, headache
and backache.
Antenatal care aims at protecting the mother and her foetus, especially during early pregnancy,
when most of the foetal organs are forming.
Childbirth has three main stages: the cervix widens and the uterus begins to contract in preparation
for birth; the baby is delivered; the placenta is delivered.
Teenage pregnancy and childbirth carry great health, emotional and socioeconomic risks for the
young mother and her baby.

End unit assessment

1. State two roles of the sex organs.
2. Define each of these words.
a) intercourse
b) implantation
c) labour
3. State any four causes of unintended pregnancy.
4. Suggest any four antenatal care measures for safe pregnancy and childbirth.
5. State any six signs of pregnancy in women.
6. In Rwanda, what is the significance of the placenta?

144 Topic 3: Health and disease

Formal assessment for topic 3
1. Choose the correct answer from the options given.
1.1 Malaria is an example of:
A an inherited disease
B a social disease
C a communicable disease
D a degenerative disease
1.2 Pneumonia is transmitted from one person to another by:
A water
B air
C blood
D an insect
1.3 What name is given to the female external sex organs?
A vagina
B vulva
C penis
D testis
1.4 In what part of the female reproductive system does fertilisation of the ovum take place?
A uterus
B cervix
C oviduct
D vagina
1.5 In which part of the male reproductive system are sperm produced?
A penis
B prostate
C seminiferous vesicles
D seminal vesicles
1.6 Figure 1 shows the structure of a human sperm.
What is the role of the part labelled A on the diagram?
A to produce energy
B to help sperm swim and reach the ovum
C to fuse with the egg cell during fertilisation
D to produce the male gametes

Figure 1

Formal assessment 145

 1.7 The ball of cells that forms a few days after fertilisation is called the:
A zygote
B embryo
C morula
D foetus (7 × 2 = 14)
2. Figure 2 shows the male and female reproductive systems.
a) Identify parts 1 to 8 in diagram A. (8)
b) Redraw diagram B and give labels for parts 1 to 6. (6)

A B
1
1

6 2

8
7 5
6
3
2

5 4
3 4

Figure 2

3. Figure 3 shows causes of maternal death worldwide by percentage.

a) What percentage of women died as a result of:
i) severe bleeding   ii) high blood pressure?     (2 × 2 = 4)
b) i) Does maternal mortality occur more frequently in urban
areas or in rural areas?    (2)
ii) Give two reasons for your answer to question (b) (i). (2 × 2 = 4)
3 pre-existing conditions
8

9 28 severe bleeding

high blood pressure

11 infections

labour difficulties

abortion complications
14
27 blood clots

Figure 3: [Source: http://www.who.int/mediacentre/factsheets/fs348/en/]

146 Formal assessment

4. Give three consequences of teenage pregnancy. (3 × 2 = 6)
5. List three ways in which the transmission of communicable diseases
can be prevented. (3 × 2 = 6)
Total marks: 50

Formal assessment 147

 Glossary

acrosome – the part of a sperm cell that makes chromosomes – long coiled structures made from
enzymes special molecules called DNA; they carry
adapted – modified or changed to do a particular genetic information
function cilia – hair-like extensions on the membrane of
alveoli – small sacs that enable the exchange some animal cells
of gases circumcision – a surgical procedure that is
amino acids – the building blocks of proteins performed to remove the foreskin

backbone – a column of bones that is found in clinostat – a motorised machine that turns
the back of an animal; also called a vertebral clitoris – a sensitive area in the female external
column sex organs
balanced diet – a diet that contains a combination communicable disease – a disease that can be
of the food nutrients needed for healthy transmitted from one person to another
living, in the right amounts conception – the fusion of the nuclei of the male
breathing – the movement of air into and out of and female sex cells
the lungs, in mammals Cowper’s gland – a gland that produces seminal
bronchi – tubes that branch from the trachea fluid
bronchioles – smaller tubes that branch from the deficiency diseases – diseases caused by a
bronchi shortage of a food nutrient, such as a
Caesarian section – a type of birth, when a particular vitamin
surgical procedure is done density – how hard or compact a substance is
carbohydrates – nutrients made from carbon, diffusion – the movement of molecules
hydrogen and oxygen, e.g. simple sugars and from a high concentration to a
starch lower concentration
cartilage – a type of tissue that is found in some disease – a disorder in structure or function in a
places in an endoskeleton person’s body
cervix – a narrow opening at the top of diversity – variety
the vagina ejaculation – a reflex action in which semen is
characteristics – features of something, such as an released from the body
organism elements – the simplest substances on Earth; they
chlorophyll – a green pigment molecule in leaves cannot be made smaller
that is important for photosynthesis embryo – an unborn human during the first eight
weeks after fertilisation

148 Glossary
endometrium – the lining of the uterus germinal cells – special cells that line the ovaries
endoskeleton – a support system that is found and the seminiferous tubules
inside an organism’s body and are able to make the female and male sex
cells
enzymes – special molecules that take part in
chemical reactions in cells gravitropism – the response of plants to the effect
of gravity
epidermis – a single layer of cells on the outside of
some organisms haemoglobin – a molecule found in red blood
cells that helps to transport oxygen
epididymis – a coiled tube inside the testes that
stores sperm until they are released health – a person’s physical, mental and
social state
erectile (tissues) – tissues that can fill with blood
and become hard hereditary – something that is passed on from
one generation to another; inherited
exoskeleton – a support system that is found on
the outside of an organism’s body hip bones – large flat bones to which the leg bones
are attached
fertilisation – the fusion of male and female sex
cells to form a zygote hydrostatic skeleton – a support system found
inside an organism’s body; the muscles work
fibre – substances in the diet that help food to against fluid that is trapped inside spaces in
move through the digestive system the body
flagellum – a tail on a cell that enables it hymen – a membrane over the opening
to move of the vagina that is broken during
foetus – an unborn human from the ninth week sexual intercourse
after fertilisation until birth hypophysis – a part of the brain that
gametogenesis – the process by which sex cells secretes some hormones; also called the
are made pituitary gland
gas exchange – the movement of oxygen and immune system – a system in the body that fights
carbon dioxide across a membrane in opposite substances that should not be inside the body
directions implantation – the process during which the ball
gender – being masculine or feminine of cells burrows into the wall of the uterus
gender equality – when males and females are infection – when a person has an organism inside
considered to be equal their body that makes them sick
gene – a unit that can be passed from parents to insulate – to keep at a constant temperature
their children joint – a structure found where bones
come together

Glossary 149
labia majora – an external skin fold near the neutralise – to keep the level of
opening of the vagina acidity constant
labia minora – a skin fold that protects the nostrils – two openings in the nose
openings of the urethra and vagina nutrients – food substances that organisms need
labour – the process during which the foetus, to live and grow
membranes, umbilical cord and placenta is oestrogen – a female hormone that is secreted
expelled from the uterus by the ovaries and stimulates the production
lipids – food nutrients made up of carbon, of secondary sexual characteristics; it is also
hydrogen and oxygen; their molecules consist involved in the menstrual cycle
of one molecule of glycerol joined to three organ – a group of tissues that form a structure
fatty acids that performs a function, e.g. the heart
magnification – how many times bigger an image organ system – a group of organs that work
is compared to the actual object together to perform a function, e.g. the
magnified – made larger using a scientific digestive system
instrument or by drawing organelles – structures found inside cells; they
malnutrition – when a person does not perform different functions
eat enough, or eats too much, of a ova – female sex cells
food nutrient
ovaries – the female sex organs that produce
menopause – the time in a woman’s life when she female sex cells and hormones
stops menstruating
oviducts – tubes that lead from each ovary to the
menstrual cycle – a series of events that prepares uterus; the pathway for the female
the uterus for pregnancy sex cells
monosaccharides – simple sugars, such ovulation – the release of an ovum from an ovary
as glucose into an oviduct
motile – able to move palisade mesophyll cells – long thin cells found
motility – the ability to move in leaves; they are specialised
moulting – shedding an outer covering of the for photosynthesis
body pathogens – disease-causing organisms, such as
mucus – a sticky substance that is made by some bacteria
animal cells penis – the part of the male reproductive system
multicellular – multi-celled; refers to an organism that is used to place sperm in the female
that consists of many cells vagina during intercourse

nerve impulses – a signal transmitted along a permeable – a structure that lets molecules pass
nerve fibre in the body through it

150 Glossary
photosynthesis – a life process that happens in selectively permeable – a structure that allows
green plants and that uses sunlight, carbon only certain molecules to pass through it
dioxide and water to make food molecules, seminal vesicles – structures that produce and
such as glucose release seminal fluid into the
phototropism – the reaction of a plant to light sperm duct
placenta – an organ that develops in seminiferous tubules – long coiled tubes in which
the uterus sperm are produced
pleural membranes – two membranes found sensitivity – being able to respond to a change in
inside the chest: one covers the outside of the the environment
lungs; the other lines the inside of skeleton – a structure on the inside or the outside
the chest of the body that gives support to the body and
polysaccharides – nutrients made from many protects the softer parts
simple sugars joined together specialised – changed, to do a
porous – a substance that has holes in it special function
progesterone – a female hormone that prepares sperm duct – a tube that transports sperm out of
the uterus for pregnancy the testes
proportion – the different sizes of objects relative spinal cord – part of the nervous system; an
to one another extension of the brain in the backbone
prostate gland – a gland that produces seminal spongy mesophyll cells – cells in leaves that
fluid contain lots of chloroplasts and have air spaces
proteins – food molecules made up of carbon, between them
hydrogen, oxygen, nitrogen, and sometimes stimulus – something that causes a reaction
sulphur support system – a system that gives strength and
puberty – a time during which secondary sexual holds the body upright
characteristics develop in males and females surface area – the area on the outside of
reagents – chemicals used for a structure
testing substances taxonomy – the classification of things, especially
respiration – a chemical process for the making of organisms, into groups based on their
energy using food molecules and oxygen similarities and differences
ribs – the thin bones that protect the lungs and testicles – a male reproductive structure in which
heart male sex cells are made; also
scrotum – a sac that covers the testes called testes
testosterone – a male hormone that is important
in the development of sperm and secondary
sexual characteristics

Glossary 151
thorax – the scientific name for the
chest cavity
tissue – a group of similar cells that perform a
function; e.g. muscle tissue
toxic – poisonous
toxins – poisons
trachea – a tube that leads from the throat into
the lungs
tropism – a movement of a plant in a certain
direction in response to a stimulus
umbilical cord – the organ that connects the
foetus to the placenta
unicellular – single-celled; refers to an organism
that consists of a single cell
urethra – a tube that is a passage for urine from
the bladder to the outside of
the body; it also transports sperm
during intercourse
uterus – the place where a baby develops;
also called the womb
vagina – the birth canal
vertebrae – bones that make up the backbone
zygote – a single cell that forms when the nucleus
of a sperm cell fuses with the nucleus of an
ovum

152 Glossary
 Index

A E
acrosome 57 ejaculation 120, 137, 144
adaptation 56-60, 67, 98, 100 elements 65-68,78
alveoli 80-86 embryo 31,125, 138, 139, 140, 142, 144, 146
amino acids 68, 78 endometrium 122, 133
B endoskeleton 95, 96, 102, 104
enzymes 50, 53, 57, 69
backbone 95, 99, 101, 104 epidermis 44, 49
balanced diet 65, 73, 78, 74, 75 epididymis 119, 120, 129
breathing 81, 84, 86 erectile (tissue) 121
bronchi 80-85 exoskeleton 93-96, 102, 104
bronchioles 80, 81, 85, 86 F
C
fertilisation 57, 122,126,129,136-138,140,144-146
Caesarian section 141 fibre 73, 77
carbohydrates 65-79, 144 flagellum 57, 63
cartilage 81, 83, 95, 104 flexible 95, 99
cervix 121, 122 foetus 138, 139, 141-144,146
characteristics 12, 14, 15, 19, 21, 30, 88, 93, 96,126, G
127, 131-135
chlorophyll 19, 22, 26, 27, 28, 31, 51, 91 gametogenesis 118,123,124,129
chromosomes 126, 127, 129 gas exchange 80-86
cilia 56-60, 63, 82, 83, 86, 122, 138 gender 65,74,78,103,118,,128,129,134,135,136
circumcision 119 gender equality 128
clinostat 89 gene 113
clitoris 121 germinal cells 120
communicable disease 111, 145, 147 gravitropism 87,88,89,92
conception 138, 140 H
Cowper’s gland 119, 120, 129
D haemoglobin 57, 60,69,79,109,113
health 4,5,56,77,107,108,109,111
deficiency diseases 67,75-78,106,108,112,114-116 hereditary 50,52,53
density 103, 104 hip bones 104
diffusion 81, 84-86 hydrostatic skeleton 93,94,104
disease 76, 77, 106-117 hymen 121
diversity 1, 2, 4, 13, 130 hypophysis 126, 132

Index 153
I P
immune system 73,113,144 palisade mesophyll cells 59
implantation 138, 139,144 pathogens 110, 143, 144
infection 11, 69,73,74,77,110,111,112,141,146 penis 119-145
J permeable 50-64
photosynthesis 7, 13, 19, 22, 26, 28, 33-34,51-59,
joint 69,95,100-104 63-64, 89-92
L phototropism 87-89,91,92
placenta 138-140,141-144
labia majora 121 pleural membranes 82, 86
labia minora 121 polysaccharides 67, 68
labour 140, 142, 144, 146 porous 114
lipids 65-70, 72, 78 progesterone 121, 126,132
M proportion 65, 73-75
prostate gland 119,120,129
magnification 38, 40-49, 85, 105 proteins 48, 65-79, 144
magnified 39, 43, 46 puberty 125-135, 142
malnutrition 65, 75, 77 R
menopause 114, 125, 132, 134
menstrual cycle 126,130, 132, 133 135, 136 reagents 65,70,78,79
monosaccharides 67 respiration 2, 6, 7, 12, 13, 50, 80, 84, 85
morula 146 ribs 95,99, 101, 102, 104
motile 57, 63, 125 S
motility 120
moulting 95, 96 scrotum 119, 120
mucus 59, 81-83, 120, 122, 137 selectively permeable 50
multicellular 19, 22, 37, 48, 51,52, 55, 60-63 seminal vesicles 119, 120, 129, 145
N seminiferous tubules 120, 124
sensitivity 2,6, 7, 12, 13, 88, 92, 140
nerve impulses 57 skeleton 93-104
neutralise 10, 120 specialised 55-60, 63, 86, 106, 138
nostrils 81, 82, 85 sperm duct 119, 120, 129
nutrients 7,37,57,58,65-79, 105-106, 115, 120, 139 spinal cord 99, 102
O spongy mesophyll cells 59
stimulus 88, 91,92
oestrogen 121, 126, 131, 132 support system 94
organ 5, 24, 25, 27, 30, 34, 48, 55-145 surface area 27,57, 58, 81, 86
organ system 55, 60-63 T
organelles 48-64, 105
ova 30,58,112,121,124,-129 taxonomy 3, 15
ovaries 58, 121,-133 testicles 119
oviducts 121-129, 137 testosterone 119,126, 131, 132
ovulation 122, 126, 132-135 thorax 84, 96, 99

154 Index
tissue 3, 41, 44, 48, 55, 56, 59-64, 69, 74,
94,95,97, 105, 132
toxic 7, 13
toxins 110
trachea 80-86
tropism 87-92
U
umbilical cord 139-141
unicellular 20,48,51,52,60,63
urethra 119-122, 129, 137
uterus 121-123, 129, 133, 138-145
V
vagina 121-145
vertebrae 97, 99, 102, 114
Z
zygote 58, 137-146

Index 155