Take Good Care of

This Textbook
This textbook is the property of your school.
BL
PU ATIO
OF
IC N
ET
HIOP
IA
Take good care not to damage or lose it.
RE
IC EDUC
AT

Here are 10 ideas to help take care of the book:

CR OF
MO RY
DE NIST
L MI
RA
DE
FE

1. Cover the book with protective material, such as plastic, old

newspapers or magazines.
2. Always keep the book in a clean dry place.
3. Be sure your hands are clean when you use the book.
4. Do not write on the cover or inside pages.
5. Use a piece of paper or cardboard as a bookmark.
6. Never tear or cut out any pictures or pages.
7. Repair any torn pages with paste or tape.
8. Pack the book carefully when you place it in your school bag.
9. Handle the book with care when passing it to another person.
10. When using a new book for the first time, lay it on its back. Open only
a few pages at a time. Press lightly along the bound edge as you turn
the pages. This will keep the cover in good condition.
 BIOLOGY
STUDENT TEXTBOOK
GRADE 7
Authors, Editors and Reviewers:
Anteneh Tesfaye(Ph.D)
Dereje Mergia (B.Sc, M.A.)
Fekadu Worku (M.Sc)
Gessesse Assefa (M.Sc)
Abebe Getahun(Ph.D)

Evaluators:
Solomon Belayneh
Getachew Bogale
Gashaw Kebede

FEDERAL DEMOCRATIC REPUBLIC OF ETHIOPIA

MINISTRY OF EDUCATION
Published E.C. 2004 by the Federal Democratic Republic of Ethiopia, Ministry of
Education, under the General Education Quality Improvement Project (GEQIP)
supported by IDA Credit No. 4535-ET, the Fast Track Initiative Catalytic Fund and
the Governments of Finland, Italy, Netherlands and the United Kingdom.

© 2012 by the Federal Democratic Republic of Ethiopia, Ministry of Education.

All rights reserved. No part of this book may be reproduced, stored in a retrieval
system or transmitted in any form or by any means including electronic,
mechanical, magnetic or other, without prior written permission of the Ministry
of Education or licensing in accordance with the Federal Democratic Republic
of Ethiopia, Federal Negarit Gazeta, Proclamation No. 410/2004 – Copyright and
Neighbouring Rights Protection.

The Ministry of Education wishes to thank the many individuals, groups and other
bodies involved – directly and indirectly – in publishing this textbook and the
accompanying teacher guide.

Copyrighted materials used by permission of their owners. If you are the owner of
copyrighted material not cited or improperly cited, please contact with the Ministry
of Education, Head Office, Arat Kilo, (PO Box 1367), Addis Ababa, Ethiopia.

While every attempt has been made to trace and acknowledge copyright, the
authors and publishers apologies for any accidental infringement where copyright
has proved untraceable.

Developed and Printed by

STAR EDUCATIONAL BOOKS DISTRIBUTORS Pvt. Ltd.
24/4800, Bharat Ram Road, Daryaganj,
New Delhi – 110002, INDIA
and
ASTER NEGA PUBLISHING ENTERPRISE
P.O. Box 21073
ADDIS ABABA, ETHIOPIA
Under GEQIP Contract No. ET-MoE/GEQIP/IDA/ICB/G07/09-F.

ISBN 978-99944-2-261-6
 Content
Unit 1: Biology and Technology 1
1.1 What is biology? 3
1.2 Industries that Utilize Biological Knowledge 5
1.3 The elevance of Biology to Society 10
1.4 Biology and Technological Innovations 18
1.5 Values in Biology Education 20
hh Unit summary 22
hh Review Exercise for Unit 1 23

Unit 2: Cell Biology 25

2.1 Microscope and its Uses 26
2.2 The Cell 32
2.3 Looking at cells 37
2.4 Cell type, shape and size 42
hh Unit summary 45
hh Review Exercise for Unit 2 45

Unit 3: Human Biology and Health 49

3.1 The Muscular and Skeletal System 50
3.2 Human Dentition 62
hh Unit summary 66
hh Review Exercise for Unit 3 67
IV C o n t e n t

Unit 4: Plants 69
4.1 Diversity of plants 71
4.2 Flowering plants 74
hh Unit summary 96
hh Review Exercise for Unit 4 97

Unit 5: Animals 99
5.1 Diversity of Animals 100
5.2 Life histories of some insects 103
5.3 Some economically important insects 107
5.4 Social insects 111
hh Unit summary 122
hh Review Exercise for Unit 5 123

Unit 6: Environment 127

6.1 Habitats 128
6.2 Studying a habitat 133
6.3 Food relationships 139
hh Unit summary 145
hh Review Exercise for Unit 6 146
 Unit
Biology and
1
Technology
Unit Outcomes
By the end of this unit, you will be able to:
”” define biology as the study of life;
”” list the branches of biology;
”” state what each of these branches of
biology studies about;
”” indicate that all natural sciences are
interrelated;
Main Contents
”” describe how biological knowledge is 1.1 What is biology?
utilized in the fields of agriculture, 1.2 Industries that Utilize
medicine and food science; Biological Knowledge
”” explain the relevance of biology to the 1.3 Relevance of Biology to
society;
Society
1.4 Biology and Technological
”” give examples of technological Innovations
innovations derived from biological
1.5 Values in Biology Education
knowledge;
ŒŒ Unit Review
”” identify values developed in learning
science to maintain a more proactive
and environmentally conscious
population.
 2 Biology Grade 7
Introduction
In your earlier grades you have studied science, which dealt with all living and non-living
things in nature in an integrated form.

Science is a systematic method of gaining knowledge about the natural world and the
social aspect of human society. Generally, it is divided as social and natural sciences as
shown in Figure 1.1. The study of natural science is divided into three major subject areas
as Biology, Chemistry and Physics.

Which of your Grade 5 and 6 topics were about living things?

The survival and well-being of humans largely depend upon knowledge of living things,
and their interactions among themselves and with their environment.
Science
Did You Know?
Social Science Natural Science
Social science deals with how people think,
behave and act; whereas natural science
Physics Biology studies about natural things.
Chemistry

Figure 1.1: Classification of science

Do biology and technology interrelate?

Biology is a branch of science by which living things Key Terms
are studied. On the other hand, technology is the science
55Science: a systematic way of
or technique that develops machines, hardware or getting knowledge through
instruments used by humans. observation and experimentation
so as to understand nature.
Biology helps the society in many different aspects, like 55Living things: are organisms
which show the properties of life.
in medicine, agriculture, environment and population 55Life: is the characteristics of
control. For biology to effectively serve the society it organisms that make them alive;
it includes characteristics like
requires materials and instruments from technological growing, reproducing, sensitivity
innovations. to stimuli, metabolizing, and
moving by their own.

As biology requires the knowledge of technological innovations; so does technology; that

is, technology needs the understanding of living systems for its further improvement and
progress of techniques to better serve the society.

In this unit, you will start studying one branch of natural science known as Biology. You
will describe biology as a part of science. You will also identify branches of biology, its
relationship with other sciences, its application and relevance to society.
 Unit 1: Biology and Technology 3
1.1 What is biology?

By the end of this section, you will be able to:

”” define biology as the study of life;
Did You Know?
”” list the branches of biology; ¸¸Living organisms range from the smallest
”” state what each of these branches of bacteria to the biggest whale.
biology studies about; and ¸¸The smallest bacteria which is the
smallest organism is less than 1 micron
”” indicate that all natural sciences
(one-millionth of a meter) in diameter.
are interrelated.

Can you define biology?

Biology is the study of living things. Biologists are

Word Roots and Origins
people who study biology or about living things.
Living things range from tiny organisms like bacteria Biology: came from two Greek words ‘bios’
to very large organisms, such as whales, elephants meaning life, and ‘logos’ meaning study.
and big trees.

Branches of Biology
Can you list down branches of biology?

Biology is the science that studies about various living

Key Terms
organisms. A living organism could be a one-celled
bacteria or a several-celled organism such as animal 55Biologists: are people who
study living things.
or plant. Although there are many branches of biology,
each focused on different aspects of living things.
The three main branches, are shown in Figure 1.2:
Zoology (animals), Botany (plants), and Microbiology
(microorganisms). See Table 1.1 for some of the major
sub-branches of biology and their definitions.

Biology
Botany
Zoology
Microbiology
Figure 1.2 Classification of Biology based on major groups
of organisms it studies
 4 Biology Grade 7
Table 1.1: Sub-disciplines in biological sciences
Sub discipline Description
Botany The scientific study of plants.
Cytology The study of cells.
Ecology The study of relationships between organisms, and their environment.
Evolution The study of the origin and gradual change of organisms in time.
Genetics The study of heredity and identity.
Microbiology The study of microscopic organisms (micro-organisms).
Physiology The biological study of the functions of living organisms and their parts.
Taxonomy The science of identification, classification and naming of organisms.
Zoology The study of animals.

Activity 1.1
Searching for other branches of biology
55 Go to your school library.
55 Find out other branches of biology
Present your findings: what do the branches study?

The Relationship of Biology with Other Sciences

Is biology related to other fields of science?

Biology requires knowledge from
Geography
other fields of science to understand
about processes in living things.
These overlaps in the study areas of
Chemistry Biology Physics
biology and other sciences resulted
in interdisciplinary studies. The
body of living things is composed of Mathematics
chemical substances. Understanding
Figure 1.3: Overlap of biology with other
reactions in living organisms and fields
their physical activities needs
knowledge of chemistry and physics
(Figure 1.3). The overlap of biology
with chemistry, for example, forms
biochemistry.
 Unit 1: Biology and Technology 5
Exercise 1.1
Choose the best answer for each of the following.
1 The word biology is derived from
A Two Latin words – bios and logos
B Two English words – bio and logos
C Two Greek words – bios and logos
D Two Greek words – bio and logy
2 Which one of the following is not true about biology: It studies
A about all living things
B about life
C the interaction between organisms
D about non-living things
3 The branch of biology that studies about plants is
A Zoology C Ecology
B Botany D Taxonomy
4 One of the following field of biology examines organisms not seen by unaided eyes?
A Taxonomy C Genetics
B Microbiology D Ecology
5 The branch of biology which studies animals is known as
A Botany C Zoology
B Cytology D Micro biology

1.2 Industries that Utilize Biological

Knowledge
By the end of this section, you will be able to:

”” describe how biological knowledge is utilized in the fields of agriculture,

medicine and food science.

Knowledge from all branches of biology are utilized directly or indirectly in different
areas of human activities. These include agriculture, medicine, and the food industry.
In general, the application of biological knowledge and techniques are necessary to the
improvements in the quality of life as well as the economic benefits they generate.
 6 Biology Grade 7
Agriculture
How is biological knowledge utilized in agriculture?
Agriculture is one of the human activities to which biological knowledge and skills are
very essential. Agricultural practices include cultivation of soil, growing and harvesting
crops, breeding and raising livestock, forestry, etc. (see Figure 1.4a−d) for the illustration
of some of the terminologies used here.

Figure 1.4 Different agricultural activities. a) spraying

pesticide to crop plantation, b) crop plantation, c) dairy cow and
d) plowing with oxen.

Is biological knowledge important to

study plant nutrients? Did You Know?
Plants require different factors for their growth. These
¸¸Plants use essential nutrients which are
include temperature, inorganic nutrients, water, light, available in the soil.
and air. Plants obtain substances such as inorganic ¸¸Primary nutrients include nitrogen, potassium
nutrients and water from the soil. Therefore, biological and phosphorous.
knowledge is essential to understand the role of ¸¸Soil is a non-renewable natural resource
which is composed of minerals, water,
nutrients in plant growth. organic matter and living organisms including
microorganisms and worms.
¸¸The top soil that contains much of the organic
Is biological knowledge necessary to matter is the fertile layer of a soil.
study soil composition? ¸¸Different soil conservation practices (vegetation
Soil plays a major role in determining the kinds covering, avoiding overgrazing, exercising
good farming practice, etc.) protect the top
of plants that grow on it. Biologists study growth
soil from being easily eroded out.
requirement of crops, analyze soil composition and ¸¸Inorganic nutrients include major soil
design ways of increasing productivity. nutrients like nitrogen, phosphorus, calcium,
potassium, magnesium and sulfur.
 Unit 1: Biology and Technology 7
Is biological knowledge necessary to study agro-chemicals ?
Biological knowledge is used to increase productivity of crops in many ways. Agricultural
industries use agro-chemicals like fertilizers, herbicides (weed-killers), and pesticides
to increase productivity. See different types of agro-chemicals in Figure 1.5. Biological
knowledge is utilized for the preparation and use of the right quantities and qualities of
agrochemicals.
Key Terms
a)
55Fertilizer: a chemical or natural
substance added to soil to
increase its fertility.
55Pesticide: a substance used
for destroying insects or other
pests of plants or animals.
55Herbicide: a chemical
substance used to destroy
unwanted vegetation or weeds
from farming sites.

Figure 1.5: Agrochemicals used by

large farms in Ethiopia:
a)atrazine (herbicide),
b)acetochlor herbicide,
b) c) d) c)hand spray and d)claearys 3336F
(fungicide)

Does crop rotation practice require biological knowledge?

Crop rotation consists of growing different crops in succession on the same land. For
instance, a farmer can possibly rotate corn, bean and teff in succession. The rotation of crops
helps to reduce the effect of pests and keep the soil fertile; moreover, it increases the yield.

Does preservation of soil require biological knowledge?

Poor agricultural practices like overgrazing, burning the vegetation cover, over fertilizing,
and vertical ploughing of steep land reduce soil fertility. So, protecting the top surface of
the soil from effects, such as erosion, is very important in agriculture.

Medicine
How is biological knowledge and skill utilized in medicine?
Medicine is the science and art of diagnosing, treating
Word Roots and Origins
and preventing disease and injury. Medical scientists
engage themselves in a constant search for new drugs, Medicine from a Latin word ‘medicus’ which
effective treatments, and more advanced technology. means physician.
Biology is one of the central foundations for knowledge
and techniques in medicine.
 8 Biology Grade 7

Does the study of effect and use of drugs require biological knowledge?
Biological knowledge and skills are found to be important to analyze the effects of drugs
on human body. A drug is a medicine or any substance which has a marked physiological
effect when taken into or applied on the body.

Antibiotics (Greek anti, “against”; bios, “life”) are

chemical compounds used to kill or inhibit the growth Did You Know?
of bacteria. All antibiotics share the property of Tobacco smoke contains about 4000 chemicals;
selective toxicity: They are more toxic to an invading one of which is nicotine and it stimulates nerves
organism than to an animal or human host. These and makes the heart beat faster.
drugs are used to fight diseases.

Does the practice of correcting drug abuse require biological knowledge?

Drug abuse is a pattern of using a substance that leads to significant problems or distress.
It can be taking more than the recommended dose of prescribed drugs such as stimulants
or depressants without medical supervision and it can also be taking antibiotics without
prescription. The major drug abuse, however, is illegally using substances like marijuana,
cocaine, heroin, or other illegal substances that are not allowed by governments.

Food

How is the biological knowledge utilized in food industries?

Food production and processing industries utilize biological knowledge and skills to
produce good quality food and to keep it safe and longer. Food is anything nutritious
and taken into the body in order to maintain life. Food is made up of compounds known
as nutrients, which can be used by organisms after the process of digestion. Biological
knowledge is needed to know the end products of digestion, absorption and utilization by
our body.

Food producing and processing industries utilize biological knowledge and skills to
provide safe and quality foods.

Does the understanding of deficiency diseases require biological knowledge?

The food we eat should contain the nutrients in a balanced proportion. The increase or
decrease of nutrients in the diet causes diseases. Deficiency diseases are diseases caused
by a lack of nutrients in the diet. See Table 1.2 for some of the deficiency diseases that
result due to lack of minerals, vitamins or other nutrients in the diet of a person. See also
Figure 1.6 for the effect of some of the deficiency diseases.
 Unit 1: Biology and Technology 9
Table 1.2 Lack of nutrients in diet and their associated deficiency diseases
Deficient Nutrient Deficiency disease
Iodine Goiter
Iron Anemia
Vitamin A Night blindness
Vitamin B (thiamine) Beriberi
Vitamin B (niacin) Pellagra
Vitamin D Rickets
Vitamin C Scurvy
Carbohydrate Marasmus
Protein Kwashiorkor

a) Rickets b) Kwashiorkor c) Marasmus

Figure 1.6 Effects of lack of nutrients in the food

Does the study of agro-chemical residues on / in food need biological

knowledge?
Agro-chemical is a general name given to those chemicals used commonly during
agricultural practices and these include fertilizers and pesticides. These chemicals have
been used for long to increase productivity in agriculture. However, most of the chemicals
used remain as residues on plants and can cause health problems when consumed by
people. Furthermore, when plants with chemical residues are consumed by other animals
and when the animals are eaten by people, the concentration of the chemical increases
several times and cause more serious health problems.

Does the practice of selective breeding require biological knowledge?

Selective breeding is a practice of controlled mating in plants and animals. It is done to
produce organisms that better serve human needs. It is a technique by which offspring are
made to have superior quality (high yield, disease resistant, drought tolerant, etc.) to that
found in either parent.

Exercise 1.2
Choose the best answer among the given alternatives.
1 One of the following aspects of agriculture does not need biological knowledge?
A studying requirements for plant growth
B preservation of soil
C the use of a tractor
D the use of manure
 10 Biology Grade 7
2 Antibiotics are drugs used to
A reduce pain C cure disease
B avoid infection D prevent diseases
3 Drug abuse is the use of
A drugs to fight diseases
B drugs to reduce pain
C drugs with out the order of doctors
D drugs with the order of doctors
4 Deficiency diseases are caused by a lack of
A lack of agro-chemicals in food C lack of drugs
B lack of balanced diet D A and B
5 Biology is useful in food industries to improve
A quality of food C preservation of food
B safety of food D all of the above

1.3 The Relevance of Biology to Society

By the end of this section, you will be able to:
”” explain the relevance of biology
to society.
Biology contributes to society in many different ways.
Biologists use their knowledge of organisms and their Did You Know?
interaction to make contributions in medicine,
Acid rain or acid deposition, is air pollution
agriculture, nutrition, population control, conservation from burning fossil fuels. Fossil fuel burning
and many other industries. Biotechnology is the applied releases large amounts of acid chemicals that
branch of biology that uses living organisms and rain down as acids.
bioprocesses in engineering, technology, medicine,
agriculture, and environment.

Health

Is biology relevant to study drugs that combat diseases in our body?

Biology is involved in understanding the human body

Key Terms
and describes its normal and abnormal conditions. All
professionals in medicine study biology. The study of 55Disinfectant: a substance used
for destroying germs from non-
biology is necessary to understand the normal body living surfaces.
processing, cause of diseases, methods of prevention,
to identify the causes of diseases, and to develop drugs.
 Unit 1: Biology and Technology 11
Drugs are used to fight diseases by curing sick people or
Word Roots and Origins
by preventing diseases before they occur. Some people
may use drugs without the instruction of physicians Antibiotics: from two Greek words ‘anti’
or illegally. The use of drugs illegally or too much of meaning against and ‘bios’ meaning life.
instructed drugs is known as drug abuse. The knowledge
and techniques in biology are useful to discover drugs (antibiotics), analyze their interaction
with the body, and their action against disease causing organisms. Antibiotics have the
property of magic effects. Drugs like penicillin is a well-known antibiotic that has been used
to fight many infectious diseases, including syphilis, gonorrhea, and tetanus.

Is biology relevant to characterize effects of antiseptics and disinfectants?

Antiseptics and disinfectants are antimicrobial chemical

substances, which reduce potential germs. Antiseptics D Y
id ou now K ?
are antimicrobial substances that destroy potential ¸¸Antibiotics are chemicals used to kill
germs. Disinfectants are chemical substances that are disease causing bacteria.
used to destroy microorganisms that contaminated
nonliving objects. These chemical substances are necessary for us to keep our places free of
potential germs. The preparation and testing the effects of these chemical substances against
potential germs require the knowledge of biology.

Is biology relevant to describe the healthy status of an individual?

Biology is involved in analyzing the human body and describes its normal and abnormal
conditions. Healthy people are those people whose body parts properly work, have good
mental status and interact with other people properly. Unhealthy people are those either
their body parts, mental condition or interaction with other people is affected in a negative
way, or all of them are affected. Analyzing the body weight of and describing the health
status of an individual requires knowledge of biology.

Nutrition

Is biology relevant to nutrition?

Nutrition is a branch of biology that studies different aspects of food we eat. The studies in
nutrition include how organisms obtain food, digest it, its composition and its uses to the
body of an organism. Biologists study foods and their contents. We depend on biological
knowledge to analyze nutrition and its health impacts. Our body requires food to grow,
reproduce, and maintain good health. Without food, our bodies could not stay warm,
build or repair tissue, or maintain a heartbeat. Eating the right foods can help us avoid
certain diseases or recover faster when we are ill. These and other important functions
of our body are fueled by chemical substances in our food called nutrients. Nutrients are
classified as carbohydrates, proteins, fats, vitamins, minerals, and water.
 12 Biology Grade 7

Is biology relevant to identify major groups of foods?

All foods at least contain one of the six basic nutrients: carbohydrates, lipids, proteins,
vitamins, mineral and water. Each nutrient plays a different role in keeping an organism
healthy.

Knowledge from biology is required to understand the composition food, digestion

and function of food that is consumed by organisms. Techniques from biology are also
required to test the presence and amount of these nutrients in the food.

Fats and sweets

Milk, yogurt Meat, chicken,

and cheese fish and egg

Fruits and
vegetables

Breads, grains
and other
starches
Figure 1.7 The five major food groups
Did You Know?
Based on their function biologists classify foods
The daily requirement of the five major food
into five groups. These groups of food include meat
groups are:
and legumes, milk and cheese, fruits and vegetables, ¸¸Group A (milk and cheese) – 300-600 gm.
bread and cereals, and fats and sweets (Figure 1.7). ¸¸Group B (fruit and vegetables) – Four
Each group of food contains the six nutrients in servings (Example: 1 fruit is one serving).
different proportions. So, the food that an individual ¸¸Group C (meat and legumes) – Two
consumes should contain the five groups in a servings (Example: 55-85 gm of meat is
one serving).
balanced form as balanced diet. Knowledge of
¸¸Group D (bread and cereals) – Four
biology is necessary to identify the major groups of servings (Example: 2 slices of bread is
foods, their sources and workout the balanced diet one serving).
an individual requires consuming. ¸¸Group E (fats and sweets) – in small
amounts.
 Unit 1: Biology and Technology 13
Activity 1.2
Constructing a balanced diet
1 Look at the picture (Figure 1.8) and classify
the food components into nutrient groups.
2 In a group, list down food items in the
food you had for your breakfast; from the
list prepare a balanced diet combination
Figure 1.8 Ethiopian dish
and discuss with the other groups.

Environment
Is biology relevant to study environment?

With growing population, rapid industrialization

Key Terms
and urbanization the use of all resources is rising.
Bad farming practices and deforestation created 55Resource: any natural or artificial
substance, energy or organism,
additional problems as well. It is feared that unless which is used by human being for
proper measures are taken to conserve them in time, living.
we will face serious problems like loss of species and 55Environment: the surroundings
or conditions in which organisms
pollution of the environment. live and operate.
55Conservation: the proper
Biologists study the environment, organisms and their management of a natural resource
interaction. We rely on biological knowledge and to prevent its exploitation,
destruction or degradation.
skills not only to investigate environmental problems
55Biodiversity: variety of organisms
but also to find their solutions. living at a given region.
55Deforestation: is clearing away
of trees and vegetation that hold
Is biology relevant to increase water and soil in place.
agricultural productivity? 55Pollution: is contamination of
the environment with materials
Farming is a collection of activities done in an area that harm health, quality of
of land and its buildings to grow crops and to rear life or the natural functioning
of living organisms and their
animals. The main activities in farming include surroundings.
cultivation of soil, growing plants, and animal 55Population: all inhabitants of a
husbandry practices. These practices can either be particular place.
good (friendly) or bad (unfriendly) to the environment.
Loss of top soil reduces the fertility of the soil and
agricultural productivity. Biological knowledge is
necessary to examine whether the farming practices
techniques in biology can also be used to reduce
problems associated with bad farming practices.
 14 Biology Grade 7
The bad farming practices consist of:
55 cutting trees to get space of crop cultivation,
55 plowing horizontally steep lands,
55 monoculturing (growing a single crop in a given area year after year),
55 burning vegetation cover and
55 allowing overgrazing.

Good farming practices, on the other hand, protect the soil from erosion and increase
agricultural productivity of the land. The good farming practices contain:
55 planting trees,
55 contour farming (farming step land horizontally),
55 terracing,
55 crop rotation,
55 reduce overgrazing.
55 manuring or using fertilizer
If good farming practices are not used and soil erosion is allowed to continue at its current
rate in Ethiopia, it will lead to continuous loss of the top fertile soil. Knowledge and
techniques in biology are needed to reduce soil erosion and conserve the top fertile soil.
Conserving the top fertile soil is important to increase agricultural productivity.

Is biology relevant to conserve natural resources?

Conservation is the wise use and protection of the environment. The environment consists
of natural resources including plants, animals, minerals, soils, water air and fossil fuels.
The environment is conserved for its biological, economic, and recreational value, as
well as its natural beauty and importance for survival of human beings. In general,
conservation of natural resources requires understanding of basic biological concepts.
Therefore, the conservation of natural resources requires knowledge from biology.

The way in which one natural resource is managed has a direct effect upon other natural
resources. For instance, cutting a forest near a river increases erosion, loss of top soil, and
can lead to flooding. Appropriate conservation methods are used to conserve different
natural resources. These include reducing planting trees, practicing good farming activities
like terracing (Figure 1.9a), reusing or recycling natural resources, and protecting or
preserving when necessary. The actual practices of these conservation activities require
biological knowledge.

Is biology relevant to control the effect of deforestation?

Deforestation is a human activity that leads to removing plant cover from a given land
for agricultural, firewood or settlement purposes (Figure 1.9b). These practices expose
the soil and lead to loss of top soil due to wind erosion and water erosion. On the other
 Unit 1: Biology and Technology 15
hand, forestation or planting tree (Figure 1.9c) has
many advantages like reducing soil erosion. Plants Did You Know?
are also an important defense against global climate ¸¸The Ethiopian Red Fox is found at Simen and
change. Forests produce life saving oxygen and Bale Mountains. It is the most endangered
consume carbon dioxide and reduce global warming. Fox with only about 550 adults remaining.
Knowledge of biology is necessary to select and grow
the appropriate plant suitable for a given area and to
care as well for the growing plant.

a) b) c)
Figure 1.9 Good farming practices. a) Planting trees; b) Terracing;
c) Crop rotation

Is biology relevant to study the effects of atmospheric pollution?

Pollution is contamination of the Library Research

environment with materials that harm
Go to the library and answer the following
health, quality of life or the natural
questions.
functioning of living organisms and
1 List activities that you consider as
their surroundings. Kinds of pollution harmful to the environment.
include air (atmosphere), water and 2 Describe the importance of planting
land pollution. Among the major trees and the effects of deforestation.
sources of pollution are power and heat 3 List down the effects of population
growth on the environment.
generation, the burning of solid wastes,
industrial processes, and, especially,
transportation (Figure 1.10). Evaluation
of the effects of pollution to human,
other organisms and the environment
requires knowledge from biology. The
solution towards reducing the effect of
practices that increases the rate of
pollution needs an understanding of
biological concepts.
16 Biology Grade 7

a) b) c)
Figure 1.10 Sources of air pollution: a) Cars,
b) Industries and c)Burning forest

Activity 1.3
Discussion on harmful activities to the environment
Method: in groups,
”” discuss and list activities that are harmful to the environment,
”” discuss and describe the importance of tree planting and effects of
deforestation.
”” discuss the effects of population growth on the environment.
”” present your summary to the class.

Population
Is biology relevant to control growth of world population?
A population refers to the total number of individuals of the same kind that are living in
a specified space. Biologists commonly use the term population to refer to the number of
the same kinds of animals, plants or other living things. But, most of the time, population
refers to human beings.
For instance human population means the number of humans living at a given area (such
as in the village, town, city, country or the Earth). Since human population has a very
strong effect on the environment than any other living things, here we will consider
human population.
The effects of population growth are different and
vast. Population growth may be beneficial to a certain Did You Know?
extent, like increasing labor force. But, there may ¸¸The prevalence of Female Genital Mutilation
come a time when the number in the population (FGM) in Ethiopia is reported to be 62%
exceeds the natural resources available to feed and between ages of 15-19, (estimates of
house it. The consequences of such an event are Population Bureau, 2010 (2002 EC)).
severe. Therefore, controlling the number of ¸¸In Ethiopia, 19% of girls were married by age
population is necessary. Knowledge of biology is 15 (Population Council, July 2004 (1996 EC)).
relevant in designing the activities that are used to
control the number of population.
 Unit 1: Biology and Technology 17
Is biology relevant to develop vaccine?
Immunization is one of the most
effective weapons available to combat
the spread of infectious disease.
Immunization is the process of making
the body resistant or immune to a specific
disease by using a vaccine. A vaccine
is a chemical substance that stimulates
the body to create antibodies to fight
a specific disease causing organism.
It is the process of safe and effective
Figure 1.11 Immunization: A child
use of a small amount of a weakened receiving a vaccine
virus or bacteria to prevent infection
(Figure 1.11). For instance vaccines developed to fight many infectious by biologists
include tetanus vaccine, meningitis vaccine, small pox vaccine, polio vaccine, hepatitis
vaccine and many others. Knowledge of biology is relevant to develop vaccine and to
immunize the population against different communicable diseases.

Is biology relevant to reduce the rate of harmful traditional practices in

Ethiopia?
Harmful cultural practices that are commonly practiced by many societies include female
genital mutilation, early marriage, rape and illegal abortion. These traditional practices
are common in Ethiopia. In Ethiopia it is possible to relate these practices to low level
of education and poverty. Education as a whole and biology education in particular is
relevant to reduce the extent of these harmful traditional practices.

Exercise 1.3
Choose the best answers for the following questions.
1 Biology is relevant to society to ensure
A over population C pollution
B health D deforestation
2 Biology is important to solve social problems of
A harmful traditional practices C recycling natural resources
B poor diet D All of the above
3 Which of the following agricultural practices is harmful?
A overgrazing C reforestation
B crop rotation D contour farming
4 Which of the following can not be the effect of over population?
A increasing famine C increasing stress
B increasing poverty D increasing quality of life
 18 Biology Grade 7
5 Tree planting reduces
A oxygen production C soil fertility
B global warming D CO2 consumption

1.4 Biology and Technological Innovations

By the end of this section, you will be able to:
”” give examples of technological innovations derived from biological
knowledge.
From early times in history, humans have
been studying other living things and tried D Y
id ou now K ?
to copy what they are doing. After observing
New robotic cars avoid collisions by using sensors
the processes and features in living systems based on bumble-bee’s compound eyes.
humans tried to apply knowledge and biological
principles to meet practical needs. Some of the discoveries made in the past were copied
from the understandings of biological principles; these include the invention of camera,
airplane and submarines. You can easily recognize how valuable the discoveries are and
their importance in changing the living pattern of humans.

Human Eye and Camera

How is a camera related to a human eye?

A human eye and a camera share

a number of features. Both the
retina film
human eye and a camera are
iris diaphragm
composed of comparable parts, pupil aperture
such as a lens, iris/diaphragm, lens lens
pupil/aperture, retina/film and choroid black point
choroid/black paint, which
actually work in different ways.
Refer to Figure 1.12 to observe Figure 1.12 A camera and a human eye
the common parts that a human
eye and a camera share.

Activity 1.4
Look at Figure 1.12 and describe similarities and differences between a camera and
a human eye in a tabular form.
 Unit 1: Biology and Technology 19
Birds versus Airplane Key Terms
55Submarine: war-ship that
moves underwater for a long
Do birds and airplanes share features? period.
The desire to fly dated back to the pre-historic period.
Many stories from olden times involve flight, such as Did You Know?
the Greek legend of Icarus and others. Long in history
humans were attracted by the flying of birds, and they A number of anatomical, physiological and
behavioral adaptations enabled birds to meet
tried to fly like birds. Wings made of feathers or
the requirements of flight.
lightweight would be attached to arms to test their
ability to fly. The results were often disastrous as the ¸¸Have hollow bones that reduce weight.
muscles of the human arms are not strong like birds. ¸¸Have strong keel-shaped breast bone
(sternum), to which the flight muscle is
The first successful piloted flight with self-powered attached to.
aircraft was done in 1903 by Orville Wright and Wilbur ¸¸Have feathers, which are light, and
smoothly shaped body.
Wright (Figure 1.13).
¸¸Have efficient four chambered heart.

a) b) c)

Figure 1.13 a) showing air lifting, b) an airplane,

c) a bird flying

Fish versus Submarine

Do submarines relate to fish?

The practice of human swimming has been known since
prehistoric times. The earliest record of swimming dated
back to Stone Age paintings from around 7,000 years a)
ago. The first submarine appeared during the 19th century
(Figure 1.14). Obviously, fish came earlier than the
submarines, which are constructed by humans. Beyond
doubt, humans tried copying the body plan, structures
and functions of fish into submarines long ago.

b)
Figure 1.14 a)A swimming fish and
b)Submarine
20 Biology Grade 7

Activity 1.5
Library reading. Go to your school library
”” in group, research on the study of Icarus.
”” research the early attempts made by people who worked under water
in huge bells containing air.

Exercise 1.4
Choose the best answers for the following questions.
1 Which of the following functions like our eyes?
A microscope C camera
B handlens D A and B
2 Which of the following is made possible by observing birds?
A submarine C Car
B an aeroplane D B and C
3 Which of the following machines moves like a millipede?
A tank C train
B excavator D A and B
4 A boat looks like a
A duck C frog
B tortoise D Lizard
5 A robot is analogous to
A dog C human
B monkey D cat

1.5 Values in Biology Education

By the end of this section, you will be able to:
”” identify values developed in learning
science;
”” maintain a more proactive
environmentally conscious Did You Know?
population. ¸¸Values in education are principles,
rules or standards of behavior that are
Both the theoretical and practical activities during realized in school life and afterwards.
biology lessons will give you the opportunity to ¸¸Biology education similar to other
develop different values. Biology, as an experimental science is intended to achieve the three
science, involves activities like critical thinking, major educational objectives, which
reasoning and problem solving. include the development of values, skill
and knowledge.
 Unit 1: Biology and Technology 21
Nowadays, biology education has Openness Cooperation
received special attention due to its Curiosity
Freedom
rapid progress and its influence on our Value
daily lives. Love Reasoning

Honesty Respect
Biology raises a wide range of issues (for
Tolerance Humility
example, ethics in relation to using
animals during experiment, conservation
of nature, environmental protection,
sustainable development). These issues
Figure 1.15 Values developed
can serve as a base for an economically in biology education
efficient, socially reasonable and
environmentally sustainable development
(see Figure 1.15 and Table 1.4).
Table 1.3 Values you can develop by learning biology

Curiosity Curiosity is the strong desire of learning more, which is the driving force to develop
skills that enable success in the study of the subject and beyond.
Love Biology gives the chance to value life, living things and the environment. While
learning biology we develop love and compassion for life, humanity, living things
and environment.
Freedom As a branch of science, while you are studying biology you will practice the freedom
of thinking and expression of your observation.
Honesty Honesty is very important in science. As a young science student you have to honestly
collect, organize, analyze and summarize your data.
Respect Learning about living things and environment at school is usually being done in
groups, during which you learn and practice how to interact with others and respect
the ideas of others.
Cooperation Group activities in a class while learning science are strong foundations for the
collaborative nature of scientific and technological works. It is important to develop
respect for others and to learn from one another.
Tolerance While working in a group during biology lesson you will develop the quality of
tolerating the view of others.
Humility Humble way of listening to what others are saying, respecting and accepting the view
of others: and accepting ones mistakes and weakness.
Reasoning In science to make a conclusion or a summary one needs to critically evaluate and
develop sense of pattern among pieces of information collected.
Openness During science lesson you should not restrict yourself to what you are only told,
without examining it. You should be open-minded to learn more than limiting
yourself to what you only learn in the class.
22 Biology Grade 7
Exercise 1.5
Choose the best answers for the following questions.
1 The interest that one develops to know about things around is known as
A humility C reasoning
B curiosity D cooperation
2 The determination that one shows to keep going until getting a solution is
A honesty C tolerance
B respect D love
3 The values that you give to the natural environment and people around you is
______.
A respect C freedom
B openess D all of the above
4 The loyality and humbleness that one shows in all activities is called
A freedom C cooperation
B openess D respect
5 The power to be critical of yourself and the information that you collect is called
______.
A cooperation C humility
B reasoning D honesty

Unit Summary
ŒŒ Biology is a natural science that studies living things (life).
ŒŒ Biology is divided into many branches, such as botany, zoology, micro
biology, cytology, ecology, physiology and genetics.
ŒŒ Biology is related with chemistry, physics, geology and other sciences.
ŒŒ Biological knowledge is utilized in various industries such as agriculture,
medicine and food science.
ŒŒ In agriculture, biological knowledge is useful to utilize fertilizers, pesticides and
weed killers to increase crop productivity. Biology is also useful in determining
soil composition, identifying plant growth requirements, practicing crop
rotation and soil preservation.
ŒŒ In medicine biological knowledge is utilized in making drugs to combat
diseases, and in food industries, to supply the right quality and quantity of
nutrients in the diets.
ŒŒ Biology is relevant to human society in aspects of health, nutrition, environment
and population.
ŒŒ In relation to health, biology is useful in using drugs against diseases, effect
of drug abuse, recognizing the physiology of healthy people, determine the
effects of antiseptics and disinfectants.
ŒŒ Regarding nutrition biology plays important roles to classify foods, identify
nutrients, determine sources of nutrients and balanced diet.
 Unit 1: Biology and Technology 23
ŒŒ Biology is relevant for the environment in many ways including practice in
good farming, preventing species loss, avoiding deforestation, preventing
pollution and also in conserving natural resources.
ŒŒ Biology is relevant to world population growth and enables provision of
medical care, immunization and avoiding harmful traditional practices.

?
Ajsjsdf AjsjsdfAjsjsdf
AjsjsdfAjsjsdf Ajsjsdf

AjsjsdfAjsjsdf Ajsjsdf
AjsjsdfAjsjsdf Ajsjsdf

AjsjsdfAjsjsdfAjsjsdf Aj
Ajsjsdf AjsjsdfAjsjsdf

Review Exercise for Unit 1

Ajsjsdf AjsjsdfAjsjsdf
AjsjsdfAjsjsdf Ajsjsdf

AjsjsdfAjsjsdf Ajsjsdf
AjsjsdfAjsjsdf Ajsjsdf

..............
..............
..............
Ajsjsdf

Part I: Choose the best answers for the following questions

1 The study of living things is the concern of
A Chemistry C Biology
B Physics D Geology
2 The concern of taxonomy is
A Classifying living things C Identifying living things
B Naming living things D All of the above
3 Which branch of science studies the chemical substances in nature?
A Physics C Mathematics
B Chemistry D Taxonomy
4 Which of the following field of studies does not require the knowledge of biology?
A Agriculture C Medicine
B Electricity D Nutrition
5 Biology is needed for a human society to improve
A health C life style
B nutrition D all of the above
6 Which of the following innovations is derived from biological knowledge?
A Bicycle C Train
B Airplane D Television
7 A good scientist has to be
A curious C incooperative
B dishonest D intolerant
8 All natural sciences are
A interacting C interrelated
B overlapping D all of the above
Part II: Match the items in column ‘B’ with items in column ‘A’
Column A Column B
9 Antiseptic A Aspirin
10 Disinfectant B Global
11 Drugs C Reasoning
12 Value D Alcohol
13 Pollution E Shisha
24 Biology Grade 7
Part III: Fill in the blanks with appropriate terms.
14 Humans invented __________ by copying the flying of birds.
15 As retina is to an eye a film is to __________.
16 A food that contains a healthy proportion of the six nutrients is __________.
17 Humans invented a __________ by copying the swimming ability of fish.

Part IV: Give short answer to the following questions.

18 Define biology?
19 List down bad agricultural practices.
20 What is the risk of trying to fly like birds? Why?

Part V: Word search.

Think about some words related to the relevance of biology to the society. Can you
find them in the word search table below? Look down, diagonally and sideways.
Be careful, some words overlap and some are written diagonally.

C B G Z D S T A E T

T P I U R X C W N E

X D O M U E J U P C

D U M I G W T K Q H

V U M L Q R E M R N

S H U W I L X T Y O

V B O T A N Y S X L

A S I Y L P N T M O

H O N E S T Y Z I G

N T E X V O L D N Y
Unit
Cell Biology
2
Unit Outcomes
By the end of this unit, you will be able to:
””define microscopes;
”” classify them into simple and
compound;
””identify their parts and tell the
functions of each part;
””define cell, list parts of plant and
animal cells seen under a compound
microscope;
””tell the functions of each part
and compare a plant cell with an
animal cell;
””examine plant and animal cells
under a microscope and draw and
Main Contents
label the structures seen under a 2.1 Microscope and its Uses
microscope; and 2.2 The Cell
””show types, shapes, and sizes of 2.3 Observation of Cells
cells using diagrams. 2.4 Cell Type, Shape and Size
ŒŒ Unit Review
 26 Biology Grade 7
Introduction

Is discovery of cells related to invention of microscope?

Biologists use different types of instruments to study life and life systems. Microscope is
one of the most important tools that biologists use to study living things. In fact, it is the
invention of microscope that led to the discovery of cells. Cells are the smallest units from
which all life forms are made. Both multi-cellular organisms, like you, and an eucalyptus
tree, and single-celled organisms like amoeba, paramecium and bacteria are made up of cells.

Microscope is a very useful instrument which is used to observe and study different types
of cells. With a microscope biologists not only observe cells but also identify their type,
shape and size.

In the following sections you will learn more about the types, parts and uses of compound
light microscope.

2.1 Microscope and its Uses

By the end of this section, you will be able to:
”” define microscope; Did You Know?
”” classify microscope into simple and ¸¸Electron microscope magnifies up to
compound; 100,000 x of the sample size under study.
”” identify parts of a microscope; ¸¸Most cells are less than 50 µm (micrometer
”” tell the functions of parts of a = 1/1000 mm) in diameter, much smaller
microscope. than the dot at the end of this sentence.

When were cells first detected?

Today we commonly get used to think of living things

Word Roots and Origins
as being composed of cells. However, the word was
not used until the seventeenth century. The first Microscope: is made up of two smaller Greek
observation of cells was made in 1665 by the English words. Micro which means small and, scope
scientist Robert Hooke. Hooke, using a microscope of meaning to ‘look’ or ‘see’.
his own invention, observed and named it cell. But,
he did not understand its significance. In 1673, Anton
van Leeuwenhoek, a Dutch merchant pioneered the
invention of one of the best microscopes of the time.
He was the first to observe, draw, and describe a
variety of cells including bacteria, other one-celled
organisms and sperm cells.
 Unit 2: Cell Biology 27
What is a microscope?

A microscope is an instrument that is used to observe objects too small to be seen clearly
with the naked eye. Microscope uses lenses or system of lenses to produce a magnified
image of an object under study. The science of investigating small objects using such an
instrument is called microscopy. Microscopic means invisible to the eye unless aided by a
microscope.

Have you ever had a chance to see and use a microscope? Tell your experience to the class.

What is the use of a microscope?

A microscope offers a chance to closely study and

learn more about smaller organisms. Even if biology is
one of the oldest in the history of science, recognition
of cells came very late. The use of magnifying
lenses was vital for their recognition and study (see
Figure 2.1).

Figure 2.1: Students observing

a sample under a microscope
Types of Microscopes
A microscope enlarges the size of the object observed
so that it looks bigger than its actual size. This is
Key Terms
called magnification. 55Monocularcompound
microscope: A compound
There are two types of microscopes. These are simple microscope with single eye
piece lens.
microscope and compound microscope (see Figure 2.2). 55Binocular compound
microscope: A compound
microscope with two eye
pieces.
55Microscope: an optical
instrument used to observe
very small objects.
B 55Microscopic: very small
A objects which are only
C viewed with microscope.
D E 55Magnification: ability of a
microscope to enlarge the size
Figure 2.2: Different types of simple of the specimen.
microscopes: A) and B) magnifying lenses; 55Lens: a piece of glass used to
C) reading lenses; D) binocular two eyepieces
and E) monocular (single eye piece) converge or diverge light and
form optical images.
28 Biology Grade 7

What is a simple microscope? Did You Know?

A simple microscope consists of a single convex When an object is magnified with a microscope,
it looks bigger, but its true size remains the
lens that is capable of magnifying an object. A
same.
microscope which consists of only one curved lens
is simple microscope. A hand lens is an example of
simple microscope. The magnifying glass, reading
lens and hand lens magnify between 10 times to
20 times (usually written as 10X to 20X). It means
that the object you are looking through these simple
microscopes will appear 10X larger than its normal
size (see Figure 2.3).
Figure 2.3: Observation of
sample with a hand lens

Activity 2.1
Observing different plants using hand lens
Materials you require:
;; Hand lens
;; Flowers from different plants (from rose and chrysanthemum plant)
;; Leaves from different plants
;; Body parts of small insects (like house fly, ants and grasshopper)
Procedure:
1 Collect flowers and leaves from different plants and bring samples of insects
to the laboratory.
2 Pick your hand lens and the objects you are going to observe.
3 Sit in an area with good lighting or sunlight.
4 Observe the flower from a rose plant (try to observe the anther and the
stigma) with your naked eyes and note what you observe.
5 Hold the rose plant flower on the opposite side of the hand magnifier from
your eyes.
6 Move the object or the hand lens until you are able to see clearly through the
lens and draw what you see.
Important: while you look through the lens, hold the object close to the hand lens
or magnifier, probably less than an inch away (see Figure 2.3).
7 Do the same for the other samples you have brought to the class or laboratory;
and note the difference between what you have observed with your naked
eyes and with the hand lens.
Also observe the skin at the back of your hand, and note the difference between
your observation with the hand lens and with your naked eye.
 Unit 2: Cell Biology 29
What is a compound microscope?

A compound microscope is a microscope that uses two

lens systems at the same time. The two lens systems Did You Know?
are the eyepiece (ocular) lens and the objective lenses.
Recent models of compound microscope can
The eyepiece lens usually magnifies ten times and is have a total magnification up to 2,000X.
labeled 10X. The objective lenses magnify four to
hundred times. The total magnification is the product
of the eye lens and objective lens magnifications. For
example, if the magnification of the eye lense is 10X
and the magnification of the objective lense is 4X, then
the total magnification is 40X.

Activity 2.2
Discussing total magnification.
In groups, discuss the total magnification of a compound microscope. Take as an example
a medium power objective and an eyepiece lens with a 10X magnifcation.

Parts of a Compound Microscope

The compound light microscope Ocular lens
(Eyepiece)
is a type of microscope
Body tube
which is commonly used in
many laboratories. This light
microscope consists of different Revolving
parts through which the sample nosepiece
Arm
under study is magnified and Objectives
observed.
Stage
Table 2.1 is based on the diagram Stage clips
of the compound microscope. Coarse adjustment
Diaphragm knob
The column on the left lists the Fine adjustment
knob
parts, and the column on the Light source
right gives its function. See also
Figure 2.4 to help you identify Base

the parts.

Figure 2.4: Compound light microscope

and its parts
 30 Biology Grade 7
Table 2.1: The compound microscope parts

Structure (part) Function (job)

Ocular (eyepiece lens) A convex lens used to magnify the image (usually 10X)
Body tube (barrel) Supports the eyepiece and the nosepiece.
Coarse adjustment knob Moves the tube up and down and produce a rough focus of
the image.
Fine adjustment knob Moves the tube up and down by very small amount and
produce a sharp focus of the image.
Arm Used to carry the microscope.
Nosepiece Contains the high- and low-power objectives.
Low-power objective lens (LP) A convex lens used to magnify the image (usually 4X)
Medium-power objective (MP) A convex lens used to magnify the image (usually 10X)
High-power objective lens (HP) A convex lens used to magnify the image (usually 40X)
Oil immersion objective A convex lens used to magnify the image (usually 100X)
Stage Supports the glass slide and contains the specimen being
observed.
Stage clips Hold the slide in place.
Diaphragm (iris) Adjusts the amount of light passing through the stage.
Light source (lamp or mirror) Illuminates the specimen.
Base The bottom of the microscope, used for support.

N.B: Your teacher will provide you with a microscope so that you can identify the parts
and their functions.
Mounting: is preparing a specimen for observation under a microscope.
Focusing: is adjustment of focus to observe specimen clearly.

Activity 2.3
Practicing mounting and focusing
Materials you require:
;; Clean slide and cover slip
Caution
;; A dot on a piece of paper FFSpecimen to be observed under a microscope
should be thin enough to pass light through it.
;; Dropper with nipple
FFSlides and cover slips should be clear because
;; Forceps dirt can interfere and confuse the observation.
;; Water in a beaker FFIf your specimen is too thick, then the cover slip
;; Compound light microscope will swing on top of the sample like a see-saw.
 Unit 2: Cell Biology 31
Procedure:
1 Lay down the piece of paper with a dot on a clean microscope slide as shown
in the diagram. (Figure 2.5)

Figure 2.5: Illustration showing how to place the cover

slip on the sample

2 Place one drop of water directly over the specimen and cover it with a cover
slip.
3 If you put too much water over the specimen, cover slip will float on top of
the water. This makes it harder to observe the specimen!
This process, if done correctly, there should be no air bubble trapped in the
water between the slide and the cover slip.
55 Air bubbles confuse the observer.
55 Cover slips protect objective lens and keep the specimen in position.
4 Place the slide on the microscope stage, with the specimen directly over the
center of the glass circle on the stage (directly over the light).
5 Always start and end with Low Power objective. Lower the objective lens to
the lowest point, then focus using first the coarse knob, then with the fine
focus knob.
6 Adjust the Diaphragm as you look through the Eyepiece, and you will see
that more detail is visible when you allow in less light!  Too much light will
give the specimen a washed-out appearance. Try it out!!
7 Once you have found the specimen on low power, then, without changing
the focus knobs, switch it to medium power. Move the object or the hand
lens until you are able to see clearly through the lens.
8 Once you have it on Medium and High Power remember that you only use
the fine focus knob! (Never use the oil immersion lens).
9 Click the high power objective lens in position and only use the fine adjustment
knob to focus on specimen. At this point, if the specimen is too light or too
dark, try adjusting the diaphragm.
10 Then, focus using the fine adjustment for sharp focusing. Do not use the
coarse adjustment/
11 Is the dot compact or diffused? Draw it.
32 Biology Grade 7
Exercise 2.1
Choose the best answer for each of the following questions
1 One of the following is not the function of a microscope.
A Magnifying the image of the sample.
B Showing the details of the sample.
C Enabling one to observe something difficult to see with naked eye.
D Enlarging the size of the sample.
2 Which of the followings is a simple microscope?
A Compound binocular microscope.
B Compound monocular microscope.
C Hand lens.
D A microscope with eye piece and objectives.
3 Why are a hand lens and a compound microscope known as light microscopes?
A Because they produce light.
B Because they use light as a source of energy.
C Because they are not heavy in their weight.
D None of the above.
4 A simple microscope consists of?
A three lenses C one lens
B two lenses D four lens
5 Magnification power of a microscope is related to its ability to:
A increase the size of the image.
B showing the fine details of the sample.
C resolving the image.
D all of the above.

2.2 The Cell

By the end of this section, you will be able to:
”” define cell as the smallest unit of life;
Word Roots and Origins
”” list parts of plant and animal cells
The word “Cell” come from Latin word, cellula,
seen under a compound microscope;
means “small room”.
”” tell the functions of parts of plant and
animal cells seen under a compound
microscope;
”” compare a plant cell with an animal
cell.
 Unit 2: Cell Biology 33
The cell is the basic structural and functional unit of
all living organisms. Most cells are very small in size. Did You Know?
Since they are so tiny they can only be seen with the Our body is made up of trillion (1013) of cells
aid of a microscope. Your body is composed of
billions of cells! Can you estimate the number of cells
in an elephant?

What is a cell?
A cell is the smallest unit of life and is often called the building block of life. All plants
and animals are made up of one or more cells. Based on the number of cells they have,
organisms can be grouped as unicellular (consisting of a single cell) or multicellular
(made up of many cells). Unicellular organisms are those organisms composed of one cell.
Examples of unicellular organisms include different bacteria, most algae and protozoans
such as, amoeba and paramecium (see Figure 2.6).

a) Chlamydomonas (an alga) b) Paramecium (a protozoa) c) Yeast (Fungi)

d) Rod shaped bacteria

e) Amoeba (a protozoa)
f) Euglena (Protozoa)
Figure 2.6: Different unicellular organisms

Multicellular organisms: plants and animals are examples of multicellular organisms.

Within your body, cells have different functions. You have blood cells, skin cells, brain
cells, heart cells and many types of other cells.

Plants are multicellular organisms, for instance, a

rose plant has also different types of cells: like stem Did You Know?
cells, root cells, and many other types. Despite their
Every living thing - from the smallest bacterium
differences, cells in living organisms have similar
to the largest whale - is made of one or more
structures and functions.
cells.
34 Biology Grade 7
Under a compound microscope a cell is observed Key Terms
to have three main parts. These are cell membrane
Unicellular organism: an
55
or plasma membrane, cytoplasm and nucleus (see organism which is made up of
Figure 2.7). a single cell.
Multicellular organisms: an
55
Plasma membrane
organism which is made up of
many cells.
Cell membrane: part of a cell,
55
Nucleus which is very thin and delicate
Cytoplasm envelope (membrane) that
covers and contains the
internal parts of a cell.
Cytoplasm: the internal fluid
55
Figure 2.7: Common parts of cells component of the cell.
(structure of an animal cell)
Nucleus: part of a cell and
55
found within the cytoplasm. It
is membrane bound structure
which contains the genetic
material of the cell.

Activity 2.4
Comparison of unicellular and multicellular organisms
55 In groups, discuss the differences and similarities between unicellular
and multicellular organisms. You may consider the difference between
yourself and an amoeba.
55 What is the difference between you and an amoeba?
55 What are the common feature(s) between you and an amoeba?

Structures of Plant and Animal Cells

What are the common cellular parts of both animal and plant cells?
Cells, the tiny structural units of life, are made up of different parts. The parts of cells are
known as sub-cellular structures or organelles. Different sub-cellular structures carry out
different functions in cells. When observed under compound microscope, both animal
and plant cells have common cellular parts (see Figure 2.8a and b). The three main parts
that can be seen under a compound microscope are:
55 the cell membrane (plasma membrane)
55 an inner region called the cytoplasm and
55 the nucleus
In fact, animal and plant cells share some more common features like the cell membrane,
nucleus and cytoplasm. The cell membrane controls materials that get in and out of the
cell. The nucleus controls reproduction and the activities of the cell. The cytoplasm
contains different sub-cellular structures in which chemical processes take place.
 Unit 2: Cell Biology 35
Chloroplasts
Cell wall

Plasma
membrane

Nucleus

Central
Vacuole

Cytoplasm

a) Animal cell b) Plant cell

Figure 2.8: Parts of animal and plant cells

Comparing Plant and Animal Cells

Did You Know?
Do animal and plant cells have Cells differ from each other within the body of
different parts? an organism according to their function.

Animal and plant cells have some key similarities

Key Terms
(Figure 2.7) and differences as well (Figure 2.8;
55Vacuole: a smaller cavity which
Table 2.2). One of the primary differences between is both found in animal and
animal and plant cells is that plant cells have a plant cells.
cell wall made up of cellulose. Plant cells have 55Large vacuole: large-sized which
is only found in mature plant cells.
chloroplast, which contains the chlorophyll pigment
55Cell wall: a rigid and protective
in which they make their own food in the process external cover of plant cells,
known as photosynthesis. Although both animal and which is made up of cellulose.
plant cells have vacuoles, the vacuoles in plant cell 55Chloroplast: sub-cellular part
of plant cells which contains
merge together at maturity and form large vacuole. chlorophyll and in which photo-
synthesis takes place.
Table 2.2: Differences between plant and
55Chlorophyll: a green pigment
animal cells
found in chloroplast and
Animal cells Plant cells responsible for absorption of
light by plants to provide energy
yyCells are smaller in size yyCells are larger in size for photosynthesis.
yyHave no cell wall yyHave cell wall 55Photosynthesis: the process in
yyHave no large central which plants use sunlight energy
vacuole yyHave large central vacuole
to synthesize food from carbon
yyHave no chloroplast yyHave chloroplast dioxide and water.
36 Biology Grade 7

Activity 2.5
Comparison of Animal and Plant Cells
;; In groups, compare and contrast animal and plant cells. Show your
comparison (similarities and differences) in a table form.
;; What do you think is the possible reason for the absence of chloroplast in
root cells?

Exercise 2.2
Choose the best answer for each of the following questions.
1 One of the following is true about cells.
A Cells are generally too small to be seen with the naked eye.
B Cells are the structural and functional units of all life forms.
C Cells are the smallest units that carry out all process of life.
D All of the above
2 One of the following is part of a cell and only found in a plant cell?
A Cell membrane
B Cell wall
C Cytoplasm
D Nucleus
3 One of the followings is a characteristic of a unicellular organism.
A It is made up of many cells.
B It is made up of a single cell.
C It requires the assistance of other cells for its biological activities.
D It is seen with the naked eyes.
4 One of the followings is a unicellular organism.
A A tree
B A cat
C A man
D A bacterium
5 One of the following parts of a cell is common to all type of cells.
A Cell wall
B Large vacuole
C Small vacuole
D Chloroplast
 Unit 2: Cell Biology 37
2.3 Looking at Cells
By the end of this section, you will be able to:
”” examine plant and animal cells under a microscope;
”” draw and label the structures of plant and animal cells seen under
a microscope.

In the previous sub-unit you have been familiarized with parts of a microscope and
their functions. Now, you will practice observing different cell samples obtained from
different organisms under compound light microscope. This will give you the opportunity
to observe different types of cells.

Precaution to be Exercised When a Using Microscope

55 Make sure the working table is clean and without any unnecessary items. 
55 When the microscope is not in use, place the low power objective in position.
55 Avoid tilting the microscope and do not touch lenses with your finger.
55 Carry the microscope by the arm with one hand and support its base with the
other hand.
55 Treat your microscope respectfully and according to proper instructions.

General Procedures on How to Set a Microscope

55 Put the microscope on the working table, keeping the arm towards yourself
and stage away.
55 The base of the microscope should be kept several centimeters away from the
edge of the table.
55 Rotate the nosepiece to make the low power objective in line with the body tube.
55 By using the coarse adjustment, raise the body-tube about 2 cm above the stage.
55 Open the diaphragm of the condenser for passing the light on the stage.
55 Look through the eyepiece, adjust the light source so that it is directed upwards.
55 Do not use coarse adjustment when viewing through the high power objective.
55 Keep the microscope always in upright position.

What are pollen grains?

Pollen grains are male reproductive cells of plants, which are equivalent to the mammalian
sperm cells.
38 Biology Grade 7

Activity 2.6
Observing pollen grains under a microscope.
Materials you require:
55 Compound microscope
55 Microscope slides
55 Flowers
55 Cover slip
55 Beaker with dropper
Procedure:
1 Gather some pollen from a flower.
2 Place it on a slide.
3 Cover with cover slip and observe the pollen under the microscope.
4 Draw the cells you see on your note book.

Activity 2.7 Key Terms

55Scanning objective: the low
Making a Wet Mount power objective used to scan
the slide in order to spot the
specimen to be observed.
Materials you require:
55Specimen: a sample to
55 Compound microscope be examined under the
55 Microscope slides microscope.
55 Flowers 55Stain: a dye used to color and
55 Cover slip make visible the whole or
55 Beaker with dropper part of specimen under the
microscope.
55 Water
55Wet mount: a process during
Procedure: which water is used as
1 Gather some pollen from a flower. mounting medium to examine
specimen under study.
2 Place it on a slide and add a drop of water. 55Pollen grains: are male
3 Cover with cover slip and observe the reproductive cells of plants,
pollen under the microscope. the botanical equivalent of the
mammalian sperm.
4 Draw the cells you see on your note book.

What are Stains?

Not all parts of cells are observed clearly while examining cellular samples under a
microscope. Certain parts of cells will be observed clearly only when samples are stained.
Stains are coloring agents. Staining is the process of adding stains or dyes to specimen
while observing the specimen under a microscope. Adding stains make the whole or parts
of the sample colored and render it easy to be examined.
 Unit 2: Cell Biology 39
What are plant epidermal cells?
Generally, the surface of the leaf is covered by Did You Know?
thin layers, which are tough skin cells (called the An onion is an edible bulb, which is made up
epidermis); the upper and lower epidermis. The of many layers of modified leaves. The surface
epidermis is made of a single layer of cells. of each leaf is covered by a thin layer of cells,
the epidermis.

Activity 2.8
Observing onion epidermal cells
Materials you require:
;; Compound microscope ;; Onion
;; Forceps ;; Eye dropper
;; Microscope slides ;; Cover slips
;; Iodine solution ;; Beaker with water

Procedure:
1 Place a drop of water in the middle of a clean slide.
2 Using forceps, gently remove a section of the skin from the inside layer of the
onion and place it on the slide on a drop of water.
3 Put the cover slip over the top gently using the forceps to hold it.
4 Observe through the microscope (by first using low-power and then focusing
under medium-power).
5 Did you see cells?
6 Put two drops of iodine solution closer to one side of the cover slip, and
leave the solution to diffuse for some minutes.
7 Observe under low and
medium power objectives.
Compare your specimen with
Figure 2.9 below.
8 Which structures of a cell
can be seen under a light
microscope?
9 Draw one cell and label all
the parts identified.
Figure 2.9: Image of onion epidermal
cells see under a microscope
40 Biology Grade 7

Activity 2.9
Observing the Epidermis of Elodea (Water Plant)
Materials you require:
55 Compound microscope 55 Iodine solution
55 Forceps 55 Eye dropper
55 Microscope slides 55 Cover slips
55 Elodea 55 Beaker with water
Procedure:
1 Place a drop of water on the slide again, and put an Elodea (water weed)
leaf in the water.
2 Put the cover slip in place as you did before and observe the leaf through the
microscope.
3 Observe a cell under low power and medium power.
4 Make a drawing of the cell and label all of the structures that you see.
Compare with Figure 2.10.

Chloroplast

Cytoplasm

Cell wall

Figure 2.10: Elodea leaf cells seen under a microscope

;; What cellular structures did you observe?

;; Compare onion epidermal cell and Elodea leaf epidermal cell.

What is the shape of cheek cells?

Unlike plant cells, all animal cells lack the rigid

Key Terms
and protective cover, the cell wall. As a result of the
absence of cell wall in animal cells, they look irregular 55Epidermis: the outer layer of
tissue in plants.
in their shapes. Due to having a cell wall, plant cells
have regular rectangular shapes (plant epidermal
cells). Remember, you are going to observe your own
cells, cheek cells.
 Unit 2: Cell Biology 41
Activity 2.10
Observing Animal Cells (Cheek Cells)
Materials you require:
;; Compound microscope ;; Cover slips
;; Microscope slides ;; Toothpicks
;; Methyl blue ;; Beaker with water
;; Eye dropper
Procedure:
1 Place a drop of methyl blue in the
middle of the slide.
2 With the end of the toothpick scrap
the inside of your cheek, then stir
the toothpick in the methyl blue,
then cover it with a cover slip.
3 Observe starting with the low
power objective and working up to
the high power objective. Compare Figure 2.11: Cheek cells observed
your specimen with Figure 2.11. under the microscope
4 Make a drawing of one or more cells and
label all of the structures that you see.
;; Can you now distinguish the nucleus, the cytoplasm and the cell
membrane?
;; Compare the size, shape, position of the nucleus of the cheek cell and
onion epidermal cell.

Exercise 2.3
Choose the best answer for each of the following questions
1 What is pollen grain?
A Small plant. C Part of pistil.
B A flower. D Part of stamen.
2 One of the following is true about onion epidermal cells observed under a microscope.
A Are flat and regular in their shapes.
B Irregular in their shapes.
C They look green without staining.
D Are flat and irregular in their shapes.
42 Biology Grade 7
3 One of the following is true about cheek cells observed under a microscope, they:
A look green without staining.
B are irregular in their shapes.
C are flat and irregular in their shapes.
D are flat and regular in their shapes.
4 Wet mounting is:
A permanent mounting.
B mounting procedure without water.
C mounting procedure with water.
D similar to staining.
5 Stains are used during microscopic observation of cellular structures is to:
A enlarge the size of the image.
B make some parts of cells coloured and easily observable.
C make the specimen to be observed more beautiful.
D resolve the parts of the cell.

2.4 Cell Type, Shape and Size

By the end of this section, you will be able to:
Key Terms
”” show types, shapes, and sizes
55Muscle cell: a cell that forms
of cells using diagrams. a muscle tissue and which is
tapered at both ends for easy
The cell is the smallest unit of living things that can contraction and relaxation.
carry out all processes of life. Not all cells are alike. 55Skin cells: epithelial cells
In the previous sub-unit you have seen that there that cover our body and are
thin and flat.
are differences between animal and plant cells (see 55Nerve cell: a cell that is
Figure 2.8). Even cells within the same organism involved in transmission of
show differences in type, size, and shape. nerve message, which is long
and branched.
55Red blood cells: very small
Cell Type in size and nearly circular in
shape.

Do different types of cells exist?

Not only cells of different organisms, but also cells within the same organism are different.
The cells that form our body are of different types. Some of the cells that compose our
body include skin cells, red blood cells, nerve cells, bone cells, muscle cells and many
others (Figure 2.12).
 Unit 2: Cell Biology 43

Epithetical cell Nerve cell Bone cell

Figure 2.12: Different cells that form part of our body

Cell Shape
Are there differences in shape among cells?
Shapes of cells of different unicellular organisms
vary (see Figure 2.6). For instance the shape of
Key Terms
Paramecium is slippery, yeast cells’s shape is oval, 55Regular shape: the defined
amoeba’s shape is shapeless, and chlamydomona’s shape (rectangular/hexagonal)
shape is round. You may take as a second example of of plant cell is due to the
shape of cells that make our body, a nerve cell is long presence of the tough and rigid
and branched, skin cells are flat and thin, red blood external cover, the cell wall.
cells are round disks, and muscle cells are pointed at 55Irregular shape: absence of
both ends. defined shape in animal cells,
is due to lack of cell wall in
animal cells.
Cell Size

Do cells differ in their size?

Majority of cells are microscopic in their size. There is diversity in size among cells that
form the same organism. If we take the same example, our body, different cells in our
body vary in their size (see Table 2.3). Eggs of animals including that of humans are
exceptionally big size as compared to other microscopic cells.
Table 2.3: Some different types of cells, their shapes and sizes
Cell Type Size in Micrometer (µm) Cell Shape
(1 µm or 1/million of mm)
Red blood cell 9 Round disk
Human egg 100 Oval Did You Know?
Amoeba 90 Shapeless
One of the longest cells is the giraffe’s nerve
Most of our cells 10-30 Different cell that extends from spinal cord to its feet,
Frog egg 2 mm Circular which is about 2 m long.
44 Biology Grade 7

Activity 2.11
Associating variation in cells to their functions
Materials you require:
55 drawings on your text and some more provided by your teacher.
55 drawing from your previous activities (Activity 2.6 and 2.7).
Procedure:
In groups, discuss the possible reason why cells that form our body vary in
their type, size and shape. Present your summary to the class (use specific
types of cells in our body when presenting your summary).

Exercise 2.4
Choose the best answer for the following questions
1 One of the following statements is true about all cells.
A They are similar in their size.
B They are similar in their shapes.
C They are similar in their size and shape
D They vary in their sizes and shapes.
2 One of the following is true about cells in our body.
A They are all similar in their sizes, shapes and types.
B They are different in their shapes, sizes and types.
C They are all different only in their sizes but similar in their shapes and types.
D They are all different only in their shapes but similar in their sizes and types.
3 A nerve cell in a human body can be characterized as:
A circular in shape. C long and branched.
B pointed at both ends. D flat and round.
4 The shape of a muscle cell is:
A circular. C flat.
B branched. D pointed at both ends.
5 Skin cells are:
A circular. C flat and thin.
B pointed. D rounded.
 Unit 2: Cell Biology 45
Unit Summary

ŒŒ Cells are generally microscopic in their size.

ŒŒ Cells are the smallest biological units that carry out all processes of life.
ŒŒ All organisms are made up of cells.
ŒŒ Unicellular organisms are those organisms that are made up of single cell.
ŒŒ Multicellular organisms are those organisms that are made up of many cells.
ŒŒ All cells commonly have cell membrane, cytoplasm, and nucleus.
ŒŒ Unlike animal cells, plant cells have additional cellular parts like cell wall,
chloroplast and large vacuole.
ŒŒ Because of the presence of cell wall, plant cells have regular shapes when
observed under the microscope.
ŒŒ Because of the absence of cell wall, animal cells have irregular shapes when
observed under the microscope.
ŒŒ Cells of different unicellular organisms vary in their shapes and their sizes.
ŒŒ Cells that make up a multicellular organism like us, are different in their sizes,
shapes, and types according to their functions.

? R Exercise for Unit 2

Ajsjsdf AjsjsdfAjsjsdf
AjsjsdfAjsjsdf Ajsjsdf

eview
AjsjsdfAjsjsdf Ajsjsdf
AjsjsdfAjsjsdf Ajsjsdf

AjsjsdfAjsjsdfAjsjsdf Aj
Ajsjsdf AjsjsdfAjsjsdf

Ajsjsdf AjsjsdfAjsjsdf
AjsjsdfAjsjsdf Ajsjsdf

AjsjsdfAjsjsdf Ajsjsdf
AjsjsdfAjsjsdf Ajsjsdf

..............
..............
..............
Ajsjsdf

Part I: Choose the best answer for each of the following questions.
1 One of the following cell structure is not seen through a light microscope.
A Nucleus.
B Cell membrane.
C Ribosome.
D Cell wall.
2 The magnification power of low power objective is:
A 10X C 40X
B 4X D 100X
3 One of the following is the function of condenser.
A Magnifying the image
B Scatering the image
C Collecting light and passing it through the stage openings
D Holding a specimen at the stage.
46 Biology Grade 7
4 One of the following is true about coarse adjustment. It is used to:
A focus under high power objective.
B adjust the amount of light.
C focus under low power objective.
D move back and forth the stage of the microscope.
5 One of the following makes a plant cell different from an animal cell?
A Cytoplasm C Nucleus
B Cell wall D A and B only
6 One of the following is found in both animal and plant cells.
A Chloroplast C Cell wall
B Large vacuole D Cell membrane
7 The regular shape of plant cells which is observed under the microscope is due to
having:
A vacuoles C cytoplasm
B cell membrane D cell wall
8 Plant cells manufacture their own food due to the presence of a cell part known as:
A vacuole C chloroplast
B cell membrane D cell wall
9 The shape of a human red blood cell is:
A disk-like C short and branched
B flat D pointed at both ends
10 The sizes of most of our body cells are about:
A 1 µm C 100 µm
B 1 mm D 20 µm
Part II: Match items given in column ‘B’ with items given in column ‘A’
Column A Column B
11 Coarse adjustment knob A Sharp focusing
12 Plant cell B With out large vacuole
13 Animal cell C Inner region of a cell
14 Cell membrane D Rough focusing
15 Fine adjustment knob E Outer region of a cell
16 Cytoplasm F With large vacuole
 Unit 2: Cell Biology 47
Part III: Fill in the blank spaces with correct answer.
17 The ability of the microscope that makes the specimen appear large is known as
________.
18 The objective lenses of a compound microscope are , , ,
and .
19 Cell membrane allows materials get and of the cell.

Part IV: Give short answers for the following questions.

20 Why do we use stains?

21 What structures make plant cells different from animal cells?
22 Where do you find sub-cellular structures of a cell?
23 Which parts of a microscope are used for focusing the image of a specimen?
24 How do unicellular organisms differ from multicellular organisms?

Part V: Copy the crossword puzzle below and use the numbered clues to complete
and solve the puzzle.

10 8

5 1 3
2
9

6
48 Biology Grade 7
The numbers in the bracket indicate the number of letters in each word.

Across

2 Controls cell reproduction (7)

4 Cell cavity with fluid filled cavity in a cell (7)

6 Cell structure for photosynthesis (11)

7 Instrument used to see small objects (10)

9 A dye used to identify cell parts (5)

10 Cell part for materials enter and leave a cell (12)

Downward
1 Contains sub-cellular structures (9)

3 Preparing specimen for observation through a microscope (8)

5 Protects plant cell (8)

8 Enlarges image of specimen (13)

 Unit
Human Biology
3
and Health Bone
Cartilage

Unit Outcomes
By the end of this unit, you will be able to:
”” describe the structure and functions of
human skeleton and divide it into axial
and appendicular skeleton;
”” list types of bones and joints, state their
functions, give examples for each and
demonstrate by using models;
”” list types of muscles, explain their
structures and functions and demonstrate
how they work using models;
”” describe how muscles and the skeleton
work together; Main Contents
”” describe the importance of physical
exercise and proper diet for health of 3.1 The Muscular and Skeletal Systems
bones, muscles and joints; 3.2 Human Dentition
”” name the different types of human teeth ŒŒ Unit Review
and relate them with their functions;
”” define dental formula;
”” show the dental formula of humans
and compare it with that of some other
animals.
 50 Biology Grade 7
Introduction
Human beings are able to walk, run, play sports, work and do exercises. All of these activities
are carried out because of the interaction of the skeletal and muscular systems. The human
skeleton is similar in design to the skeletons of other vertebrates (animals with an interior
spinal column). All vertebrates (including mammals, birds, fish, reptiles, and amphibians)
have a spine, a skull and ribs. A spine supports their body, a skull protects their brain, and
ribs protect their heart and lungs.

As in humans, skeletons give animals their shape and ability to move in particular ways.
Skeletons can give us clues about the way an animal lives. For instance, some animals (like
a rabbit) need to run very fast. Such animals have very long, large back legs compared to the
rest of their body. The bones of bats and most birds are very thin and lightweight, making
it easier for them to fly.

The other creatures are invertebrates that do not have a skeleton inside their body. A few
types of invertebrates (such as insects, spiders, and crabs) have a special exoskeleton (a
hard outer casing) on the outside of their bodies. However, most invertebrates (including
mollusks, worms, and sponges) do not have a skeleton at all. Since the skeletal system works
with the muscular system, this unit deals also with the types and functions of muscles.

Because the human teeth development and arrangement is related to the skeleton this unit
also deals with the types and functions of teeth.

3.1 The Muscular and Skeletal System

By the end of this section, you will be able to:
”” divide human skeleton into axial and appendicular skeleton;
”” describe the structure and functions of human skeleton;
”” list types of bones;
”” give examples of each type of bone;
”” list types of joints;
”” tell the functions of each type of joint;
”” classify joints into movable and immovable;
”” demonstrate movable joints using models;
”” list types of muscles;
”” explain the structure and functions of muscles;
”” demonstrate how muscles work using models, describe how muscles
and skeleton work together;
”” describe the importance of physical exercise and proper diet for the
health of bones, muscles and joints.
 Unit 3: Human Biology and Health 51
Can you define a skeleton?

The skeleton is the entire collection of bones inside

Did You Know?
our body. See Figure 3.1 below that shows the human
¸¸There are 206 bones in adult human body.
skeleton.

Activity 3.1
Investigating the human skeletal system.
Materials you require:

A drawing or a model of the skeletal system.

Procedure:
55 in groups, examine the drawings of the human skeletal system; and
55 identify the axial and the appendicular skeleton.

Bone
Cartilage

Figure 3.1: The human skeleton

 52 Biology Grade 7
Axial and Appendicular Skeleton

What are the parts of the skeletal system?

The bones of the skeleton can be categorized into Key Terms

two: the axial and appendicular skeleton.
55Cranial bones are parts of
the skull serving as brain
What is the axial skeleton? case.
55Facial bones are parts of the
The part of the skeleton along the axis of the body is skull that maintain the shape
the axial skeleton. The axial skeleton consists of Skull, of the face.
Sternum, Ribs and Vertebral column (see Figure 3.1). Sternum

What is the Skull? Ribs

The skull is a bony outline of the head formed from

Vertebral
cranial and facial bones. The cranium protects the column
brain. However the facial bones provide structure for
the upper and lower jaws, cheeks and nose.
Figure 3.2: The human rib cage
What is Sternum?

The sternum is the breast bone found in the middle of Did You Know?
the rib cage attached to it by cartilage.
¸¸The ribs help you to breath.
What are Ribs?

The Ribs are 12 pairs of thin and flat bones. They

are slightly curved and connected to sternum in the
middle of the chest. The ribs form a protective cage
around the internal organs in the upper body.

What is the vertebral column?

The vertebral column also referred to as the back-

bone or spine vertebral column is extending from the
end of skull to the pelvis (hip). The vertebral column
serves to connect all other bones of the skeleton and
support the body.

The vertebral column with its continuous hollow tube Figure 3.3: The vertebral
keeps the spinal cord in and protects it. column
 Unit 3: Human Biology and Health 53
Key Terms
Activity 3.2
55Axial skeleton is the axis of
the skeletal system.
Looking at the axial skeletal system of 55Appendicular skeleton is the
humans appendage of the skeletal
system.
Materials you require: 55Skull is part of the axial
A drawing or a model of the axial skeletal system skeleton with the bones of
head and face.
Procedure: 55Sternum is breast bone at
55 in groups, examine the drawing or model of the center of the chest cavity.
the human vertebrae, skull, and chest, then 55Ribs are chest bones that
form the chest cavity.
55 identify the bones of the vertebral column.
55Vertebral column contains
back bones that give support
What is the appendicular skeleton? to the other body parts.

The second category of the human skeleton is called Word Roots and Origins
the appendicular skeleton. It supports the limbs and
connects them to the axial skeleton. It is composed of Skeleton from Greek word skeleton, dried body.
all the bones of shoulder, hip and limbs or appendages.

Clavicle
What are shoulder bones?
Scapula
The shoulder bones are composed of clavicle and
scapula. The clavicle or collar bone is connected to
Humerus
the sternum in front while the scapula bone is at the
back (see Figure 3.4).

What are limbs or appendages? Ulna

Radius
The fore limbs are the front limbs that refer to the
Carpals
arms, the forearms and the hands. It consists of various Meta carpals
bones (See Figure 3.4). These bones are: Humerus Phalanges
(upper arms), Radius (inner lower arm), Ulna (outer
lower arm), Carpals (wrists), Metacarpals (hands) Figure 3.4: The shoulder
and fore limb
and Phalanges (fingers).

What are hip bones?

The hip bones are also known as hip girdle and composed of two hip bones.
54 Biology Grade 7

What are the hind limbs? Coxal

bone Sacrum
The hind limbs are the back limbs or appendages and
consist of different bones (See Figure 3.5). These
bones include: Femur (upper leg or thigh), Tibia and
Femur
Fibula (lower legs or shin), Patella (kneecap) Tarsals
(ankles), Metatarsals (feet), and Phalanges (toes).

Activity 3.3 Patella

Tibia
I Looking at the pectoral and pelvic
Fibula
girdles and appendages
55 in groups, examine the bones of the Metatarsals
Phalanges
appendicular skeleton, and
55 identify the shoulder bone and hip Tarsal
bone and appendages. Figure 3.5: The hip bones
and hind limb
II Constructing models of the human
skeleton
Word Roots and Origins
Method
Appendicular from latin word appendicula,
55 in groups, construct a model for a appendage.
human skeletal system using paper
or other local materials.
55 try to trace on card board, by
cutting and connecting them in the
appropriate position.
55 label each bone.

Structures and Functions of the Skeleton

What does the skeleton do?
The skeletal system is one of the major systems of the Did You Know?
human body, and has four major functions: ¸¸Hydrostatic pressure or water inside the
55 it protects vital organs, such as the brain, body of small plants and animals serves
heart, and lungs. as a skeleton.
¸¸Femur is the largest while stapes (ear
55 it supports the body and gives us our
bones) are the smallest bones.
distinctive shape. Without our skeleton, ¸¸When humans are born they have around
we would look more like a slug. 350 bones, but have only 206 bones at
55 it allows us to move in particular ways. adult stage. What is the reason?
 Unit 3: Human Biology and Health 55
55 it makes new blood cells to maintain a
healthy bloodstream. Did You Know?
¸¸Limbs compose more than 50% of our
The skeletal system, besides providing support,
bones in number.
movement, and organ protection, is also the storage ¸¸Clavicle are the most commonly broken
area for substances. It stores calcium phosphate that bone in the body.
is needed for blood clotting, nerve function, and ¸¸Bones continue to grow until people are
muscle activity. With so many important jobs to do, 18-25 years old.
the skeleton is a vital part of the human body.
Word Roots and Origins
Types of Bones
Pectoral from Greek word pechys, for arm.
Can you list down types of bones in our body?
Bones are living organs. They are made up of living
cells. These are cells surrounded by hard and dead Cartilage
mineral substances with an outermost layer of thin
membrane. The cells enable bones to grow and
Spongy bone (contains
repair themselves while the minerals give strength red bone marrow)
and shape. The membranes are supplied with nerve Compact bone
and blood vessels to nourish the bone. Bones are the
strongest materials in the body but only represent
Blood vessel
about 14 percent of a body’s weight.

Do our bones have the same size and

shape?

Bones of the skeleton vary in shape and size so do in

their structure. Based on their structures bones can be
grouped into:
55 Long bones: are compact bones with
hollows or cavities filled with yellow
bone marrow. Their ends contain spongy
bones covered with cartilage for cushion.
They are designed for strength. Upper and Figure 3.6: Anatomy of
lower limb bones are the best examples of long bones
long bones.
55 Short bones: are compact bones with
chambers or partitions but without
marrow. Bones of fingers and toes are
some examples.
56 Biology Grade 7
Flat bones are compact bones that have no cavity or hollow. Examples are bones of ribs,
sternum and scapula.

The outermost layer is a thin membrane containing nerves and blood vessels that nourish
the bone. On the surface there are small holes for entry and exit of materials in and out
of the bones.

Activity 3.4
Classifying bones of cattle in accordance with size and strength
Materials you require:
Bones of cattle
Procedure:
55 in groups, collect bones of cattle from a butcher or a village, and
55 identify and classify the bones according to their types size and strength.

What is a bone marrow?

In many bones the middle part holds bone marrow. Bone marrow makes new red blood
cells for the body. Not all bones contain marrow.

To keep our bones strong and healthy, we should be able

Key Terms
to get plenty of calcium in our diet. Calcium is the most
55Bone marrow is soft
abundant metallic mineral element in the human body, structure in the bones where
and 99% of it is stored in the bones. Along with building blood cells are made.
strong bones, calcium also helps your heart, muscles,
and nerves function.

Types of Joints

What are the types of joints in our body?

The place where two bones meet is called a joint. Joints have two main jobs to perform.
One is to keep bones far apart so that they don’t rub together. The other job is to hold the
bones in place as they move or rotate.

What is an immovable joint?

There are two different types of joints: fixed (immovable) joints (see Figure 3.7) and
movable joints (see Figure 3.8).
 Unit 3: Human Biology and Health 57
55 In an immovable joint, the bones are fixed Cranium
in place and do not move at all. The skull
has many of these joints. Although it
looks like one solid piece of bone, it is
actually made up of bones fused together
with fixed joints.
55 Moving joints allow a person to twist
and bend. Some moving joints allow us
to move a lot and others only allow us to Figure 3.7: Immovable
joint (skull)
move a little.

There are two main kinds of moving joints.

55 A hinge joint is like a hinge on a door,
Hip socket
allowing movement back and forth in a
single direction. Elbows and knees have Femoral head
(ball)
hinge joints, as do fingers and toes.
55 A ball and socket joint is made of the round Femur
(thigh bone)
end of one bone (the “ball”) fitting into a cup- a) Hinge joint b) Ball and socket joint
shaped socket in another. Such joints allow Figure 3.8: Types of
movement in all planes (in every direction). moveable joints
Shoulders and hips have these joints.
55 Gliding joints allow sliding surface movements between adjacent bones.
Vertebrae bend our neck and waist by gliding movements.
55 Pivot joints allow twisting movements. For instance, when someone is saying
‘yes’ or ‘no’ using his/her head. Another occurs when a person twists a screw
driver. You can turn your head and look up and down because of this joint.

Activity 3.5
Discussion on the Types of Joints
55 in groups, write down the different types of joints.
55 discuss the type of movement allowed by each type of joint.
55 give example for each from your body.
55 make model joints.

What is a ligament?
Bones are held together at the joints by stretchy bands of tissue called ligaments. In
between the bones of a joint, there is a firm, rubbery tissue called cartilage. Cartilage
supports and cushions the bones, acting like the body’s natural shock absorber. It also
gives shape to boneless parts of our body like our ears and noses.
58 Biology Grade 7

Activity 3.6
Constructing models of different types of joints
Materials you require:
Cardboard, papers, and glue.

Procedure:
55 Observe carefully the types of joints and then cut the cardboard or any
thick paper accordingly, and
55 Put them together or connect them.

Structures and Function of Muscles Did You Know?

¸¸Our body is made up of over 600 muscles.
What are muscles?
In unit two, you have learnt
about cells. Now, in this sub-
unit you are going to learn
about a particular tissue, i.e.,
muscle, its structures, types
and functions.

Muscles are tissues composed

of cells that are called muscle
fibers.

Muscles are needed for all

types of movement. They are
also needed to pump blood,
breathe, produce body heat,
regulate body temperature,
and protect internal organs.

Figure 3.9: The muscular system

 Unit 3: Human Biology and Health 59
Types of Muscles Key Terms
55Skeletal muscles are muscles
What are the types of Muscles? found attached to the
skeleton.
There are three types of muscles in human body. 55Smooth muscles are muscles
They are skeletal muscles, the smooth muscles and found attached to the internal
organs.
cardiac muscles. 55Cardiac muscles are muscles
found in the heart.
Skeletal Muscles 55Tendons are connective
tissues that connect bones to
muscles.
What are skeletal muscles?

Skeletal muscles: are muscles attached to the bones

of the skeleton by tissues called tendons. They are
capable of permitting body movement. When these Skeletal
muscle

muscles contract, skeletal parts move. The contraction

of the skeletal muscles is under conscious or voluntary
control and occurs faster than other muscles (see
Nuclei
Figure 3.10). Figure 3.10: Skeletal muscles

Smooth Muscles

What are smooth muscles?

Smooth muscle
Smooth muscles: are muscles found in the walls
of viscera (intestine, stomach, and other internal
organs) and blood vessels. Their contraction is
involuntary and contract more slowly than the Nucleus

skeletal muscles. However, they can remain Figure 3.11: Smooth muscles
contracted for a long time. They are not connected
to bones (see Figure 3.11).

Cardiac Muscles Cardiac muscle

What are cardiac muscles?

Cardiac muscle: is found only in the walls of the Nucleus

Figure 3.12: Cardiac muscle

heart. Unlike the skeletal muscles its contraction is
involuntary for the most part. Its contraction Did You Know?
pumps blood and accounts for the heart beat (see
Heart never rests and beats between 2 and 3
Figure 3.12).
billion times in a person’s life time
60 Biology Grade 7

How do muscles work? Triceps Triceps

When muscles are involved in body movement,

they actually work in pairs in antagonistic manner.
While one muscle in the pair contracts the other must
relax. For instance, if you were to bend your arm at
the elbow, the following sequence of events would
take place. The biceps contracts and bulges and at the
same time the triceps relaxes (see Figure 3.13). You Biceps Biceps

can see the bulge in your arm as the biceps contract.

To lower the arm to the original position, the muscles

work in reverse of what was just described. The biceps
relax while the triceps contract. Try this by yourself!
Figure 3.13: An example of
In your heart also, when the upper chamber (auricles) antagonistic function
contract, the lower chambers (ventricles) relax. of muscles

Activity 3.7
Looking at how muscles work
55 in groups, use two bones from models you have constructed before.
55 attach coiled wires to the bones to their front and back sides.
55 move one of the bones up and down while holding the other.
55 observe what is happening to the coils.
55 how do you associate this to the action of skeletal muscles?

Muscles and Skeletal Health

Key Terms
Do our skeleton and muscles require 55Antagonistic muscles are
health care? Yes, they do. a pair of muscles that work
oppositely.
To take proper care of your skeletal and muscular 55Biceps are the front muscles
of the upper arm.
systems, there are three things you can do. You should do 55Triceps are the back muscles
physical exercise; have a healthy diet; and plenty of rest. of the upper arm.
55Involuntary muscles are
muscles that are not under
How does physical exercise affect conscious control.
muscle and skeletal health? 55Voluntary muscles are
muscles that are under
Exercise is needed to help muscles and skeleton grow conscious control.
55Striations are bands or lines
and develop. When muscles and skeleton are not used, formed by actin and myosin
they shrink and become weaker and smaller. Exercise fibers in muscle cells.
55Contraction is the
helps to keep muscles strong. Physical exercise can shortening of muscles.
improve muscular and skeletal strength, endurance and 55Relaxation is the stretching
of muscles.
flexibility in all adults regardless of age (see Table 3.1).
 Unit 3: Human Biology and Health 61
Table 3.1: Recommended physical exercise for different age groups
Children 7-12 Teenagers 13-18 Adults 19-55 Elders>55
Vigorous activity for Vigorous activity for 3-5 Vigorous activity for 1/2 hrs, Moderate exercise
1-2 hours times a week 3 times a week 3-4 times a week
Free play Build muscles with Exercise aerobics, stretching Plan a daily walk
physical exercise exercise
Develop motor Pursue tennis , swimming, Take active vacation, bicycle, Daily stretching
skill of Team sports, horseback riding cross country exercise
dancing, swimming
Encourage more Continue team sports, Join a running club, bicycle Try low-impact
exercise outside HPE dancing club, outing group aerobics
HPE: Health and Physical Education

How does a proper diet help muscle and skeletal health?

A proper diet helps your bones and muscles get the nutrients needed for their healthy
growth and functions. Meat supplies proteins needed for cell growth and the creation of
new cells. Dairy products supply minerals, such as calcium, that are needed to make bones
strong and hard. Fruits and vegetables provide vitamins like vitamin D that are good for
bone structure. Breads and cereals provide carbohydrates and minerals for muscles to
move the bones.

How does rest help skeletal and muscle health?

Rest is also critical to good health. When muscles move, food molecules are burned
and waste products are left behind in the muscles. Rest provides an opportunity for the
circulatory and excretory system to remove these wastes. Rest also helps prevent muscles
from being overused.

Activity 3.8
Discussion on the importance of physical activities and proper diet for
healthy muscles and skeleton
55 In groups, discuss and suggest exercises required to keep muscles and skeleton
healthy.

Exercise 3.1
Choose the best answers for one of the following questions.
1 One of the following is part of the axial skeleton?
A skull C tibia
B humerus D metatarsals
62 Biology Grade 7
2 Which of the following is part of the appendicular skeleton?
A vertebrae C sternum
B ribs D metacarpals
3 The pectoral girdle consists of the bones of:
A collar and scapula C tibia and fibula
B radius and ulna D wrist and ankle
4 The hind limb consists of:
A tibia C femur
B metatarsals D all of the above
5 Which of the following bones are found in both fore and hind limbs?
A wrist C ankle
B phalanges D ribs
6 Knee is an example of which type of joints:
A ball and socket C pivot
B gliding D hinge
7 Ball and socket joints are found in the:
A hip C elbow
B shoulder D A and B
8 As the ribs protect the lungs, ________ protects the brain.
A facial bones C sternum
B cranium D metacarpals
9 Which type of bones is wrongly paired with its example?
A long bone-humerus C short bone-vertebrae
B flat bone-ribs D A and B
10 One of the following is wrong?
A Skeletal muscles move skeletal bones.
B Smooth muscles are found in blood.
C Cardiac muscles work life long.
D Muscles work antagonistically.

3.2 Human Dentition

By the end of this section, you will be able to:
”” mention the different types of human teeth;
”” relate types of human teeth with their functions;
”” define dental formula as a short way of indicating the numbers,
types and arrangement of teeth;
”” show the dental formula of humans;
”” compare human dental formula with that of some other animals.
 Unit 3: Human Biology and Health 63
What are teeth?
Before you learn human dentition it will be
helpful to see the structures of tooth for your
Crown Enamel
understanding of the lesson (see Figure 3.14). Dentin
Pulp
Teeth of humans and other animals are hard Gum

structures that grow from jaw bone. These

Root canal
teeth are used to bite and chew food. Each Neck
tooth consists of crown, neck and root. A crown
is the part above the gum level. A neck is the
part surrounded by gum; and a root is the part Jawbone

embedded in jaw bone. The crown is a surface

Root
for biting food and composed of outer layer
enamel. Both root and inner part of the root
contain a living substance dentine. A tooth is Figure 3.14: Structure of a tooth
also composed of a central region called pulp
cavity that contains nerves and blood vessels.

Activity 3.9
Identifying parts of a tooth
Materials you require:
Model or drawing of teeth.
Procedure:
55 in groups, identify parts of a tooth, and
55 label the parts.

What are milk and permanent teeth Key Terms

in humans? 55Dentition is the arrangement
and development of teeth in
Humans grow two sets of teeth in their lives. The first the mouth.
55Gum is the flesh that covers
set has 20 teeth called milk teeth. Milk teeth loosen the jaw.
and fall out when a child is about 6 years old. The 55Crown is the white part of a
second set has 28 teeth that replace the milk teeth and tooth seen above the gum.
are called permanent teeth. When a person is around 55Enamel is the hardest outer
covering of the crown.
20 – 25, four additional back teeth grow called
55Dentine is the living tissue of a
wisdom teeth. tooth.
55Pulp cavity is the inner part
This development and arrangement of teeth is known of a tooth, with blood vessels
as dentition. It differs among mammals according to and nerves.
their feeding habit. 55Root is the part of the tooth
that is inserted into the jaw.
 64 Biology Grade 7
Types of Human Teeth Incisors

Upper jaw

Can you list the types of human teeth? Canines

Premolars

Humans have four types of teeth (see Figure 3.15.)

These are:
55 Incisors: are front teeth with chisel edge.
55 Canines: are side teeth beside incisors
Third molars
and with pointed edge.
Second molars

55 Premolars: are side teeth behind the First molars

canines with fairly flat ridges having

depressions.
Lower jaw
55 Molars: are far back side teeth with wider Permanent Teeth
and stronger ridges having depressions. Figure 3.15: Types of Teeth

Activity 3.10 Key Terms

Looking at different types of teeth 55Milk teeth the first and
replaceable set of teeth.
Materials you require: 55Permanent teeth the second
and non replaceable set of
Models or drawings of teeth. teeth.
55Wisdom teeth the last
Method: four teeth that appear in
55 In groups observe closely the types of adulthood.
teeth in humans. 55Upper jaw: jaw in the upper
55 Notice the different types of teeth and row.
label them. 55Lower jaw: jaw in the lower
row
55 Write their respective functions.

Functions of Each Type of Teeth

Can you tell the functions of each type of teeth?

There is correlation between the type of tooth and its function. Each type of tooth is
suitable for its function.
55 Incisors being chisel-shaped used for biting, cutting and gnawing food. They
function as scissors.
55 Canines as they are sharp pointed used for tearing and piercing food. They
function as pincers.
55 Premolars because they have flat ridges used for grinding.
55 Molars since they have wider and stronger ridges are used for crushing and
grinding foods.
55 Both molars and premolars function as grinders.
 Unit 3: Human Biology and Health 65
Dental Formula
How do you define dental formula?
Dental formula is a short way of indicating or
representing the number of teeth, type and arrangement.
It shows the number and type of teeth in one half of the
upper and lower jaws. In dental formula each type of
tooth is symbolized by the first letter of its name. Also, Molars
the types and number of teeth are written according to
Premolars
their location in the mouth from the front to the back
Canines
sides. As a result, incisors (I) are the first, canines (C) the Incisors
second, premolars (P) the third and molars (M) the last. Figure 3.16: Dental formula
of humans
How do you write dental formula of a mammal?
Dental formula of a given mammal can be L i b r a ry R e a d i n g 3 . 1
written by counting the number and type of
Go to the library and read about the
teeth in one half of the upper and lower jaws.
dental formula of different mammals
From Figure 3.16, the dental formula of an adult then, answer the following questions.
human is: 1 Write down the dental formula of
I = 2/2, C = 1/1, P = 2/2 M =3/3 a cat, a dog and a cow.
2 Explain why dental formula differs
Therefore, the total number of teeth in a given among mammals.
mammal can be calculated. First add the number 3 Can you write the dental formula
of teeth in upper and lower jaws, and then of human milk teeth and calculate
multiply each jaw by two. Finally, sum up the the total number of teeth?
product. For instance we can calculate the total
number of teeth in adult human as follows:
2+1+2+3 8 8×2 16 Did You Know?
= , = 16 ¸¸Enamel is the hardest substance in
2+1+2+3 8 8×2
our body
Total teeth =16 + 16 = 32 ¸¸Lower incisors are the first to
grow out in childhood.

Exercise 3.2
Choose the best answers for each of the following questions.
1 Which of the following types of teeth function as scissors?
A Molars C Canines
B Premolars D Incisors
2 Types of teeth with the widest upper surface are:
A Molars C Canines
B Premolars D Incisors
66 Biology Grade 7
3 The shapes of teeth in humans is related to their:
A size C function
B location D A and B
4 The dental formula of mammal is representing the number and type of:
A teeth in one half of the upper jaws
B teeth in one half of the lower jaws
C full set of teeth in the mouth
D A and B only
5 Which of the following shows the formula for incisors in the dental formula of an
adult human?
A 1/1 B 2/2 C 3/3 D 4/4
6 Compared with the dental formula of human, a mammal having a dental formula
0123
3123
is having
A less number of incisors C more number of molars
B less number of canines D less number of molars

Unit Summary
ŒŒ In this unit, we have first taken a brief look at the skeletal and muscular systems
of the human body.
ŒŒ Each of these systems is important to the functioning of our complex bodies.
ŒŒ The skeletal system of humans has axial and appendicular parts.
ŒŒ The axial includes the skull, sternum, ribs and vertebrae bones.
ŒŒ The appendicular comprises the pectoral girdle (clavicle and scapula), limbs
(fore and hind) and pelvic girdle (hip) bones.
ŒŒ The skeletal system carries out five important functions.
ŒŒ It provides structure and framework for the entire body, allows movement,
protects vital tissues and organs inside the body, stores some substances
needed in body activity, and produces new blood cells.
ŒŒ The skeletal system is structurally composed of bones, cartilage, joints,
tendons and ligaments.
ŒŒ Bones are living organs made up of cells surrounded by hard minerals of
calcium phosphate.
ŒŒ Bones can be long, short and flat.
ŒŒ Joints are junction of bones which can be movable or immovable.
ŒŒ Movable joints can be hinge, ball and socket, gliding, and pivot.
ŒŒ The muscular system makes movement possible by working with the skeletal
system.
ŒŒ There are three types of muscles. They are skeletal, smooth, and cardiac muscles.
ŒŒ Skeletal muscles are voluntary muscles attached to skeleton for movement.
ŒŒ Smooth muscles are involuntary muscles that are found in internal organs (lung,
intestine) and blood vessels.
ŒŒ Cardiac muscle is found in the heart to pump blood.
ŒŒ Skeletal muscles are found in pairs and work in antagonistic manner; when
one contracts the other relaxes.
 Unit 3: Human Biology and Health 67
ŒŒ Programmed Physical training and proper diet with good rest are needed for
the health of the skeletal and muscular system.
ŒŒ Dentition is the development of teeth and their arrangement in the mouth.
ŒŒ The four types of teeth in human dentition are Incisors, Canines, Premolars
and Molars.
ŒŒ The four types of teeth vary in their shape and are suitable for their functions.
ŒŒ Dental formula represents the number and type of teeth in one half of the
upper and lower jaws.

? R
Ajsjsdf AjsjsdfAjsjsdf
AjsjsdfAjsjsdf Ajsjsdf

AjsjsdfAjsjsdf Ajsjsdf
AjsjsdfAjsjsdf Ajsjsdf

AjsjsdfAjsjsdfAjsjsdf Aj
Ajsjsdf AjsjsdfAjsjsdf

Exercise for Unit 3

Ajsjsdf AjsjsdfAjsjsdf
AjsjsdfAjsjsdf Ajsjsdf

eview
AjsjsdfAjsjsdf Ajsjsdf
AjsjsdfAjsjsdf Ajsjsdf

..............
..............
..............
Ajsjsdf

Part I: Choose the best answers for each of the following questions
1 Axial skeleton does not include
A Clavicle C Vertebrae
B Skull D Ribs
2 The shoulder consists of clavicle and
A cranium C scapula
B skull D sternum
3 The rib cage consists of the bones of the ribs and
A humerus C patella
B skull D sternum
4 Bones are attached to one another with a tissue called ______.
A ligaments C cartilage
B tendons D joints
5 Which of the following types of muscles never tire?
A Smooth muscles C Skeletal muscles
B Cardiac muscles D Ligaments
6 The up and down movement of the head is an example of one of the following
joints?
A ball-and-socket C pivot
B hinge D gliding
7 The bones of the skull are examples of one of the following joints?
A ball-and-socket C pivot
B hinge D fixed
8 Which of the types of teeth are not found in a six years old baby?
A Incisors C Molars
B Canines D Premolars
9 If a given mammal has a dental formula of 0/3, 2/2, 2/3, 3/3, how many total teeth
does the animal have?
A 26 C 46
B 36 D 56
68 Biology Grade 7
10 Which one is necessary for healthy bones, muscles and teeth?
A proper diet C restlessness
B physical exercise D A and B
Part II: Match the items in column B with items in column A
Column A Column B
11 Skull A pumping action of the heart
12 Ribs B front teeth
13 An example of pivot joint C protect lungs
14 An example of hinge joint D side teeth
15 Smooth muscles E knee
16 Cardiac muscles F blood vessels contraction
17 Incisors G wrist bones
18 Canines H protect brain
Part III: Fill in the blanks with the appropriate terms.
19 The human skeleton is divided into ______ and ______ skeleton.
20 Front teeth with chisel edge are known as ______.
21 Muscles in a pair ______ and ______ antagonistically.
22 The development and arrangement of teeth in the mouth is known as ______.
23 Dental formula of mammals varies in accordance with their ______ habit.
Part IV: Give short answers for the following questions.
24 Which part of the skeleton is axial?
25 Where do you find the scapula part of the human skeleton?
26 How does hinge joint differ from pivot joint?
27 When does your cardiac muscle stop work?
28 Why are molar teeth used for crushing and grinding foods?
Part V: Copy this table into your exercise book. Draw a pencil line through each of
the words related to skeletal system. Words go up and down in both directions.
P E L V I C G I R D L E Q H
E B E E T W E N A E U C U E
O G F R T T N Q D T C B E L
P K P T I B I A I H Y D E L
L D Z E U K D H U M E R U S
E V W B P L S M S O T I L K
M N J R E A T S O V H B N U
A M O A R F H Q T E I S A L
N S F I B U L A H R O J T L
A X I A L S K E L E T O N R
Unit
Plants
4
Unit Outcomes
By the end of this unit, you will be able to:
”” tell that plants are diverse in size, type
and distribution and demonstrate love
and respect to plants;
”” classify plants into flowering and non-
flowering and mention mosses, ferns
and gymnosperms as non-flowering
plants;
”” give examples of flowering plants,
state their general characteristics and
explain the structures and functions of
the root, stem and leaves;
”” identify stomata using a microscope;
”” classify flowering plants into mono-
cotyledons and dicotyledons, distinguish
between the two, and give examples for
each; Main Contents
”” explain vegetative reproduction and
give examples of flowering plants that 4.1 Diversity of Plants
reproduce by vegetative reproduction; 4.2 Flowering Plants
”” draw and label the structures of
a flower, state their functions and ŒŒ Unit Review
examine pollen grains and ovaries
using a hand lens; and
”” tell the importance of pollination and
the process of fertilization, state how
fruits and seeds develop, state the
functions of the structures of a seed
and draw and label these structures.
 70 Biology Grade 7
Introduction
Plants are essential for our survival because they
produce our foods. We eat them directly as grains, Did You Know?
vegetables, and fruits. We also eat plants indirectly by
¸¸Algae, which mainly live in water and are
eating animals that consume them. Plants also serve photosynthetic organisms were used to be
as sources of medicines, cosmetics, perfumes, papers, included with the plants, but they are now
for making shelters (houses), fuels and other many classified with the protists. Currently, plants
products (Figure 4.1). Can you add more? include organisms that live primarily on land,
excluding algae that live mostly in water.

Key Terms
55Autotrophs: organisms that
synthesize their own foods from
simple inorganic substances like
Figure 4.1: The use of plants carbon dioxide and water.
55Producer: autotrophic organisms.
Plants are multicellular organisms with the ability to
55Flower: the sexual reproductive
produce their own food by the process of structure of flowering plant.
photosynthesis. They are known as autotrophs. Thus, 55Seeds: a flowering plant’s unit of
plants are known as producers. They have cellulose reproduction and which is capable
of developing into another plant
cell wall and store their food as starch. of the same type.
55Fruit: the seed bearing structure of
Have you ever tried to classify plants flowering plants which developed
around you? after fertilization; which is usually
sweet and fleshy in its nature.
You may look outside and observe plants around 55Cotyledon: an embryonic
leaf which is found in seeds of
you. You will observe that they appear in different flowering plants.
sizes, forms, and colours. It is true that plants show 55Monocot: types of flowering
great diversity. They include living organisms from plants that have a single cotyledon
very small to big trees. They differ in the type with in their seeds.
no flowers and with flowers. Up to now, about 55Dicot: types of flowering plants
that have two cotyledons in their
350, 000 different species are identified and studied seeds.
by botanists. They are distributed from tops of big
mountains to deserts.

Flowering plants make about 80% of all known plants. These plants have flowers as their
organs for sexual mode of reproduction. The flowering plants produce seeds and fruits.
On the basis of their seeds there are two major groups of flowering plants, namely the
monocots (plants with seeds made up of single cotyledon) and dicots (plants with seeds
consisting of two cotyledons).
 Unit 4: Plants 71
In this unit, you will begin studying plant biology. You will examine the diversity of
plants together with the characteristics of non-flowering and flowering plants. You will
also identify the parts of flowering plants and their functions.

4.1 Diversity of Plants

By the end of this section, you will be able to:
”” tell that plants are diverse in size, type and distribution;
”” demonstrate love and respect to plants;
”” classify plants into flowering and non-flowering;
”” mention mosses, ferns and gymnosperms as non-flowering plants.

Activity 4.1
Examining the general characteristics of plants
55 In groups discuss and summarize the main characteristics of plants. Consider
different plants that you know and refer to the general features given in
your text.
55 Summarize your discussion in the form of a table.

Diversity of Plants

What are the general characteristics of plants?

Basically, plants are groups of living organisms that Key Terms

prepare their own food. Most of them live on land. They
55Mosses: small non-flowering
include different types of organisms – with large number
plants with leafy-like structures
of known living species. and which commonly grow in
moist places closely packed
Do plants appear in different sizes? together (Figure 4.2a).
55Ferns: leafy non-flowering plants
When we look at plants living around us, yes, they with an under ground stem with
exist in different sizes. Some of them appear as big roots from which leaves (fronds)
trees and some look very small like the moss (less than grow.
7 cm in its height) and grasses (Figure 4.2). 55Gymnosperms: plants that form
unprotected seeds, which are not
covered by ovary or fruits.
55Cones: reproductive structures
which contain male and female
gamete forming units.
72 Biology Grade 7

a) Mosses b) Big trees

Figure 4.2: Plants of different size

Activity 4.2
Looking at Plants
You are going to look at plants growing in your school compound. Classify them
according to:
55 their size.
55 having flower or not.
55 having cones or not.
55 the color of their flowers.
You may do observation of different types of plants growing on the roadside while
coming to school or going back home.
55 Do all plants you have been observing contain the same part?
55 Do all look similar?

Classifying Plants into Flowering and Non-Flowering Plants

Are there different types of plants in our surroundings?

Plants not only differ in their sizes, they also vary in the presence or absence of flowers.
The non-flowering plants are those plants that do not have flowers and they include
mosses, ferns and gymnosperms (Figure 4.3). The flowering plants are those plants
having flowers as their sexual reproductive structure. Out of the 390,000 known species
of plants about 352,000 species are flowering plants. Thus, plants that use flowers for
their sexual reproductive system make the largest production of the total land plants so
far identified. The non-flowering plants use other structures instead of flowers for their
sexual reproduction. For instance pines (a gymnosperm plant) use cones (Figure 4.4) for
their sexual mode of reproduction.
 Unit 4: Plants 73
Plants

Non flowering plants Flowering plants

Eg. Eucalyptus (Bahir zaf [in Amharic]),
Rose plant (Tsigereda in Amharic)
Mosses Ferns Gymnosperms
Eg. Conifer (like
Tid in Amharic)
Figure 4.4: Cone of
Figure 4.3: Classification of plants based Gymnosperm
on presence or absence of flower as
reproductive structure

Activity 4.3
Checking whether a plant has flower or any other reproductive
structure
Materials you will require:
55 cones of gymnosperms
55 flower of chrysanthemum or any other plant

Procedure
1 Collect cones of conifers and flowers of chrysanthemum or any flowering plant.
2 Examine them carefully. Note that seeds of conifers are found attached with
cones. Flowers of flowering plants are structures that develop into seeds and
fruits.
55 Do all plants have flower

Do plants that live at different places Key Terms

differ? 55Cactus: succulent (with much
water) plant with thick fleshy
Plants are found in all parts of the world in different and spiny stem that live in dry
numbers and types. They live in different climates places (Figure 1.3a).
(wet to dry places); at different altitudes (in highlands 55Grasslands: a large area of land
mainly covered with grass and
and lowlands) and on different soil types (sand, silt, especially used for grazing.
clay and loam). Plants living in a particular place or
habitat have special features that allow them to live
there. Features suitable for a given habitat might Did You Know?
make it difficult for the plant to live in a different Mosses are very small green plants. Typically
place. For instance, you wouldn’t see a cactus on the they consist of a stem not much thicker than
top of Ras Dashen Mountains (Figure 4.5). Nor would a thick hair. A moss plant stem is covered by
you see tall trees in grass lands (Figure 4.6). many tiny leaves.
 74 Biology Grade 7

Figure 4.5: Succulent plants, Figure 4.6: A grassland region with

agave (Ret in amharic) a vast stretch of grass without
cactus (Kulkual in Amharic) any visible tall trees

Exercise 4.1
Choose the correct answer from the alternatives for each of the following questions.
1 Which of the following plants are useful in making household materials?
A Mosses
B Rose plants
C Ferns
D Conifers
2 Plant materials can be used:
A for preparing the textbook you are now using.
B as direct food sources.
C for preparing chairs.
D all of the above.
3 Types of plants in a given area can be affected by:
A the type of the climate. C the type of the soil.
B the elevation. D all of the above.
4 A flower is the reproductive structure of:
A mosses. C conifers.
B ferns. D a coffee plant.
5 A moss plant is commonly found in:
A dry places. C in water bodies.
B on sunlight exposed areas. D on shady areas.

4.2 Flowering Plants

By the end of this section, you will be able to:
”” state the general characteristics of flowering plants;
”” give examples of flowering plants;
 Unit 4: Plants 75
”” explain the structures and functions of the root;
”” explain the structures and functions of the stem;
”” explain the structures and functions of the leaf;
”” identify stomata using a microscope;
”” classify flowering plants into monocotyledons and dicotyledons;
”” distinguish between monocotyledons and dicotyledons;
”” give examples of monocotyledons and dicotyledons;
”” explain vegetative reproduction in flowering plants;
”” give examples of flowering plants that reproduce by vegetative
reproduction.

General Characteristics of Flowering Plants

What are the general characteristics of flowering plants?

The flowering plants are the most common types of

Key Terms
plants on Earth. They make the largest proportion of
all land plants and majority of all known seed plants. 55Angiosperms: group of plants
that have flowers and produce
They are the only group of all plants that have flowers their seeds within containers.
as their sexual reproductive structures. Flowers are 55Fodder: food for cattle and
unique structures of these plants that ensured their other livestock.
dominance on Earth. Flowering plants are also known 55Seed: a part of flowering and a
gymnosperm plant and which
as Angiosperms, which literally mean ‘hidden seeded
is capable of developing into
plants’. Economically they are important sources of another such plant.
our food, wood fire, shelter, fences, spices, beverages, 55Fruit: usually sweet fleshy part
clothes, fodders, dyes, and medicines. They include of flowering plants that cover
their seeds.
about 352,000 different species; as a result botanists
55Pollination: the process of the
consider them as the most abundant, varied, familiar transfer of pollen grains from
and economical plants. one flower to another or within
the same flower.
Flowering plants or Angiosperms are generally 55Pollination agent: an agent
characterized as plants: which is involved in transferring
pollen grains from flower to
55 having flowers, special sexual reproductive flower or within the same flower.
structures.
55 having seeds and fruits, where their seeds
are enclosed in fruits. Did You Know?
55 having unique fertilization system. The size of flowering plants ranges from giant
Eucalyptus (Bahir zaf) to the smallest type like
55 in addition to wind, use different pollination
Wolffia (1 mm across).
agents.
76 Biology Grade 7

Activity 4.4
Examining the general characteristics of flowering plants.
In groups:
55 Discuss the general characteristics of flowering plants. (You may even raise
the issue like why they become so successful of all plants that live on land)
55 Mention some of the examples of flowering plants that grow in your locality.

What are the main parts of flowering plants?

From your lesson of Unit 2, you are aware of a

Key Terms
flowering plant has three major parts namely; the
stem, the leaf, and the root. At maturity these plants 55Vegetative: parts of a plant
which are not directly related to
will have an additional fourth component, the sexual reproductive system.
flower (Figure 4.7). These structures in turn may be 55Shoot system: the above ground
organized as reproductive and vegetative structures. parts of the plant, which included
the stem, the leaf and the flower.
The only sexual reproductive structure of a flowering 55Root system: the underground
plant is flower. The stem, leaf and root make up the part of the plant, which consists
vegetative part of the plant. Commonly, the stem, of the main root, lateral roots, root
hairs, root tip and the root cap.
the leaves and the flower are above ground parts 55Stem: the main body or stalk of
of plants. These parts of a plant work together to a plant that supports a fruit, leaf
keep the plant fixed at a given place, erected above and flower: and helps the whole
plants to be erected.
ground, photosynthesize and reproduce. The root is 55Leaf: a flat and blade like structure
an underground part of plants. In fact, each of these of a plant in which photosynthesis
structures has an important set of functions. mainly takes places.
55Root: a part of a plant that grow
below the ground and which
absorbs water and minerals from
Flower the soil.
Shoot System

Did You Know?

Leaf
Stem
Root System

Lateral ¸¸Welwitschia – a unique gymnosperm plant

Roots roots that grows in Namib desert (Southern Africa),
and lives up to 2000 years in these extreme
conditions! But only makes two leaves
throughout its life. It takes water from sea
Figure 4.7: The main parts of a mist (water vapor).
flowering plant
 Unit 4: Plants 77
Activity 4.5
Examining the main parts of flowering plants
You will require:
55 bean plant, 55 hand lens, 55 maize/grass
Procedures:
Working in groups, carefully uproot bean and maize/grass plants grown for the
purpose in pots.
1 Identify the major parts of these plants as the stem, the root, the leaves and
the flower.
2 Draw and label the parts.

What are the major functions of roots to plants?

The root is one of the important parts of the plant that
grows underground and fixes it to the soil. The root Key Terms
not only attaches the plant into the soil, but it also 55Primary root: the main root that
first grow from the base of the
absorbs water and minerals. The main functions of the
stem.
roots of a plant include: 55Lateral roots: secondary roots
55 absorption of water and minerals from the that branch from the primary or
surroundings. main root. They are commonly
thinner than the main root and
55 attaching the plant to the ground and structurally
are uniform in their size.
supporting the plant. 55Root hairs: very fine roots that
55 conducting absorbed water and minerals to the are branching from lateral roots
above ground parts of the plant. or main root. They are involved in
absorption of water and minerals.
55 food storage.
55Root tip: the part of the root
which is growing down wards into
What are the main external features of the soil.
the root? 55Root cap: a very hard part of the
The root system of a plant contains different root which covers and protects
the growing region of the root,
parts. The main (primary) root, lateral roots, root
the root tip.
hairs, root tip and root cap form the root system 55Tap root system: a main or central
(Figure 4.8). Root systems can be bigger than the root that grows deep down wards
plant they support. The root system of the plant tends and from which lateral roots grow.
to grow in length and not width, in order to search for 55Fibrous root system: a system
water, and minerals. in which many smaller roots with
equal width grow from the stem
The Root base.

ROOT

Primary root
Lateral root
Root hairs
Root tip
Tap root System Fibrous root System
Root cap (Carrot) (Grass)

Figure 4.8: The root systems Figure 4.9: The tap (Example: carrot) and
fibrous (Example: grass) root systems
78 Biology Grade 7

What are the main root systems?

Generally, there are two main kinds of root systems in plants, namely the tap root system
and the fibrous root system (Figure 4.9). In tap root system a single central main root
grows deep downward into the soil and lateral branches developed sideways. In this root
system the main root is wider in diameter and the lateral roots are narrower. A carrot root
is a good example for the tap root system. Fibrous root system is a type of root system
which contains many smaller roots of similar diameters. Roots of corns make the best
example of fibrous root system.

Activity 4.6
Examining fibrous and tap root systems
You will require:
55 bean plant, 55 maize/grass,
55 hand lens, 55 carrot plant.
Procedure:
1 Working in groups, carefully uproot bean, carrot and maize/grass plants
grown for the purpose in pots.
2 Brush away a little of the soil and wash off the rest so that the roots are well-
cleaned.
3 Identify the root system as fibrous or tap root system.
4 Draw and label parts of the root system.

What are the main internal

features of the root?
All plant body parts, the stem, the leaf and the root have
similar internal features. These parts of the plant are made
up of two major parts; the external cover and the internal Key Terms
component (Figure 4.10). The main parts of a plant are 55Epidermis: the outer layer of
externally covered by the epidermis. In addition, the tissue in a plant.
internal part of the root and stem is made up of different 55Cortex: the outer layer of
parts like the cortex, the transport elements and the pith tissue immediately below the
epidermis of a stem and root.
(not commonly found in roots). The transport component, 55Pith: the central part of tissue
which is also known as vascular bundles contains the found commonly in a stem.
xylem and the phloem. The cortex and the pith are located 55Vascular bundles: food and
to the outside and inside of the transport component. water transporting tissues in
higher plants that include the
Unlike parts of the shoot system, such as the stem and phloem and xylem.
the leaf, the root is not exposed directly to sunlight.
Thus, its external cover, the epidermis is not covered
by a waxy substance; the cuticle. The cuticle covers
mainly leaves and the stem epidermal layer in order to
reduce the loss of water from the plant body.
 Unit 4: Plants 79
The root is part of the plant which is found below
Cortex
the soil. As a result it is not exposed to sunlight, Epidermis
and it is not involved in the process of
photosynthesis. The cells that make up the
Pith
internal part of the root do not have chloroplast.
Chloroplasts are sub-cellular structures that
Phloem
Vascular
contain the photosynthetic pigments like Xylem bundle
chlorophyll. Unlike the root, the stem and the
leaf are the above ground parts of the plant. Figure 4.10: The cross section
of major internal parts
Especially, cells that make up the leaf contain of roots and stems of
high numbers of chloroplasts. flowering plants

The Stem
What are the main functions of stems to plants?

The stem is part of a plant which is found above

ground, above the soil. The stem together with the
Key Terms
leaf and the flower (at the time of maturity) make 55Herbaceous plant: a type of
flowering plant with soft and
up the shoot system of the plant. It is part of the usually green stem, which is
plant that erects and keeps the whole plant body commonly small in size. The
above the soil. There are many different ways to stem surface is covered by
epidermis.
describe plants in a given environment. Based on
55Woody plant: a type of
softness or strength the stem, there are two types plant with tough and mostly
of flowering plants: herbaceous (non-woody) and non-green stem, commonly
woody (Figure 4.11). large in size and its surface is
covered by bark.
The main functions of the stem include:
55 Transporting water and minerals from the root to other parts of the plant.
55 Erecting the plant above the ground and holds there so that it receives
maximum sunlight.
55 Supporting above ground part like leaves and flowers; even fruits.
55 Transporting photosynthetic products from leaves to other parts of the plant.
55 Providing the attachment of climber plants.

a) A woody plant b) Herbaceous plant

Figure 4.11: Woody and herbaceous plant
 80 Biology Grade 7

Activity 4.7 Did You Know?

Examining transport of water and minerals
up through the stem.
You will require:
55 bean plant,
55 beaker/tin
55 blue/red dye ¸¸There are carnivorous plants which together
55 blade/knife/scalpel with photosynthesis obtain their additional
nutrients by digesting other organisms (like
Procedures: insects). This jug-like plant traps insects
1 Working in groups, carefully uproot bean into rolled leaves which contain digestive
plants grown for the purpose in pots. enzymes.
2 Brush away a little of the soil and wash off the
rest so that the roots are well-cleaned.
3 Place the plant carefully into a beaker that contains a dye.
4 Leave the plant in the ink for an hour.
5 Cut the stem with a blade (be careful not to hurt yourself or your friend) into
pieces and observe the progress of the dye through the stem from the root.
55 Is the dye moved upwards through the stem?
55 What do you think about the movement of water within the stem of a big
tree?

The Leaves
What are the main functions of leaves to plants?

Leaves are one of the parts of the shoot system,

which are found attached to the stem. They
are parts of plants which are flat and broad;
as a result, they have a large surface area.
Thus, the larger part of leaves is exposed to
the environment, and makes them suitable for
their functions, being the site of photosynthesis
(Figure 4.12). Figure 4.12: Leaves

The most important functions of leaves include:

55 Carry out photosynthesis to make food
55 Gaseous exchange
55 Transpiration (water loss)
55 Store food
 Unit 4: Plants 81
What are the main parts of leaves?
Commonly, a leaf has the blade or lamina, (the broad
Key Terms
leaf part), and the petiole (leafstalk) that fixes it to the
55
Pest: an animal like an insect
stem. The petiole extends into the blade and branches that feeds and attacks part of
into veins (Figure 4.13). A leaf is made of tissues, which the plant.
55
Blade: the broad and flat part of
are sandwiched between two tough layers (upper and the leaf.
lower epidermis). The epidermis also secretes a waxy 55
Midrib: the large strengthened
or the main vein along the
substance called the cuticle. The epidermal layers midline of the leaf.
protect the leaf from insects and other pests. Among 55
Mesophyl tissue: the tissue
the epidermal cells are pairs of sausage-shaped guard of leaves which is found in
between the upper and lower
cells. Each pair of guard cells forms a pore (called epidermis, and with many
stoma; the plural is stomata). Gases enter and exit the chloroplasts.
55
Stoma (stomata): minute
leaf through the stomata. Most food production takes opening in the leaf epidermis.
place in cells called mesophyll tissue (Figure 4.14). 55
Guard cells: a pair of curved
cells that surrounded the stoma.

Stoma
Blead (opening for gas Guard cells
exchange)

Waxy circle

Vein
Messophyle Vain
(Photosynthetic (vacular
Midrib cells) bundle)

Leafstalk Lower
Air space epidermis
(Petiole) Guard clles
Waxy circle
Carbon Oxygen
Stem dioxide
Figure 4.13: External structure Figure 4.14: The internal structure
of a leaf of a leaf

Activity 4.8
Examining the Leaf
You will require:
55 Leaf of Cana indica (Qey abeba) 55 Hand lens
or leaf from any other plant, 55 Glass slide
55 Blade/scalpel 55 cover slip
55 Nail varnish 55 beaker, dropper and water
55 Microscope
I Observing under the Microscope or using a Hand Lens
Procedures
1 Cut a very small section of the leaf (about 2 mm2).
82 Biology Grade 7
2 Place it on the microscope slide and add a drop of water.
3 Cover it with a cover slip (be careful not to trap air bubble in between).
4 Identify the stoma using medium power objective.
5 Observe the under side of the leaf directly using a hand lens and identify the
stoma.
II Observing the Underside of the Leaf using Nail Varnish
Procedures
1 Paint the underside of a leaf (Cana indica leaf) with clear nail varnish and
leave it to dry.
2 When nail varnish dried, peel off the part very carefully.
3 Examine the imprints of the stoma using hand lens.
55 Can you observe the stomata and the guard cell?
55 What do you think is their function?

Monocotyledons and Dicotyledons

What are the two major groups of flowering plants?
The two main groups of flowering plants are the
Key Terms
monocots and the dicots. Both have flowers as their
reproductive organs. Actually, the names monocots 55Dicots: are flowering plants
basically with two cotyledons in
and dicots refer to the number of cotyledons, or their seeds.
food storage structures, in the seed. There are two 55Monocots: are flowering plants
cotyledons in dicots and only one cotyledon in basically with one cotyledon in
their seeds.
monocots. Naturally, the number of dicots (about
170, 000 different species) are more in the environment
than the number of monocots (about 65, 000 different species). It is because of this that
we commonly come across a dicot plant than a monocot. But, remember that grasses
including the edible ones (teff, barely, wheat and maize) are monocots.

What are the similarities between monocots and dicots?

The monocots (monocotyledons) and the dicots (dicotyledons) are two groups of flowering
plants that share many features, like having flowers as their sexual reproductive structures,
seeds and fruits, and the vegetative body parts (the stem, the leaf and the root).

What are the differences between monocots and dicots?

In addition to the number of cotyledons they have in their seeds, the monocots and dicots
differ in many aspects. Examples of dicot plants include most flowering trees, all of the
common shrubs, most common vegetables we eat, sunflowers, Venus’s flytrap, beans,
and peas. Examples of monocot species include wheat, corn, rice, barley, all grasses, and
palms. The differences between dicots and monocots are summarized in Table 4.1.
 Unit 4: Plants 83
Table 4.1: Main differnces between monocots and dicots

Character Monocots Dicots Key Terms

55Cotyledon: a leaf-like structure in
seeds. It serves as stored food for
embryos in seeds.
Leaf venation 55Venation: the arrangement of
veins in a leaf.
55Parallel venation: venation
Parallel venation Net venation
in which veins are arranged in
parallel to the mid rib across the
leaf surface.
55Net venation: venation in which
Flower parts veins are branching sideways
from the mid rib on the leaf
surface.
Flower parts Flower parts in
in threes four or fives 55Vascular bundles: the food
transporting (phloem) and water
transporting (xylem) tissue.

Number
of seed
cotyledons
One cotyledon Two cotyledons

Vascular
component
arrangement Distributed Arranged in
through out circle

Activity 4.9
Examining Monocotyledonous and Dicotyledonous Plants
Materials you will require:
55 different plants in the school compound
55 tapes
55 paper

Procedure:
1 Arrange yourself in groups and collect one specimen for each flowering plant
main group from your school compound.
2 Bring the specimens to the class, arrange and tape the specimens on a piece
of paper, examine them carefully.
3 Label the samples as a monocot or dicot.
84 Biology Grade 7

What are the differences between seeds of monocots and dicots?

Seeds of monocotyledonous and dicotyledonous plants have one cotyledon and two
cotyledons, respectively. A cotyledon contains stored food and serves as a food reservoir.

Activity 4.10
Examining the Seeds of Flowering Plants
You will require:
55 corn and bean seeds (soaked 55 peanut
in water 1 day before) 55 knife (not sharp) to cut seeds
55 iodine 55 worksheet
Procedure:
55 In this practical you will differentiate between monocot and dicot seeds.
55 Make sure you soak the seeds in water one day prior to the laboratory
session.
55 Examine the seeds carefully and draw exactly what they see.   

Reproduction in Flowering Plants Key Terms

55Sexual reproduction: a type of
How do plants reproduce? reproduction during which two
parents are involved and that
Flowering plants reproduce both through sexual and requires union of gametes.
asexual means in order to produce new individuals 55Asexual reproduction: a type
or offspring. Sexual reproduction is a means of of reproduction during which
reproduction during which offsprings are produced by a single parent is only involved
the union of gametes formed from female and male with out the union of gametes.
parents. This results in the formation of offspring 55Offspring: the child or children
of a person, or young of an
genetically different from the parent or parents. animal or a plant.
Asexual reproduction is a type of reproduction during
55Genetics: the study of heredity
which an organism produces new individuals without and variation among organisms.
the need of union of gametes. The offspring produced
are genetically identical to the parent plants and each
other. Flowering plants use flowers for their sexual Did You Know?
mode of reproduction. They use their vegetative body In seed plants, the offspring can be packaged in
parts such as the stem, the leaf and the root during their a protective seed, which is used as an agent of
asexual mode of reproduction. dispersal.

Vegetative Propagation
What are the main characteristics of asexual reproduction in flowering
plants?
Asexual reproduction is production of new individuals without the fusion of gametes. It
requires only one parent and produces large number of new plants within a very short
 Unit 4: Plants 85
period of time. It does not involve flowers, pollination Key Terms
and seed production. Instead, a new plant grows from
55
Clones: a group of organism or
a vegetative part. During asexual means of reproduction
cells, produced asexually from
in flowering plants, the new plants are obtained from one ancestor to which they are
non-reproductive parts such as the root, stem and leaf. genetically identical.
The process is known as vegetative propagation. 55
Pollination: the transfer of pollen
from anther to stigma.
In asexual reproduction: 55
Natural vegetative propagation:
55 a single organism is involved in reproduction. a type of reproduction during which
plants naturally use vegetative body
55 there is no production of gametes. parts for asexual reproduction.
55 offsprings produced are genetically identical. 55
Artificial vegetative propagation:
55 it is relatively rapid mode of multiplication. a type of vegetative reproduction
that humans utilize the vegetative
Vegetative propagation in flowering plants can be means of reproduction in flowering
natural or artificial. Commonly, plants which can plant to asexually reproduce them.

reproduce asexually almost always reproduce sexually

as well, with flowers. During natural vegetative propagation a vegetative part of a plant
like the stem develops into a plant rather than forming branches.

Natural vegetative propagation is a type of asexual reproduction during which a flowering

plant produces new individuals naturally using vegetative parts. The main part of the
plant body which is involved in natural vegetative reproduction is the stem. Vegetative
propagation by stem includes both underground stems such as tubers, rhizomes, and corms
or sub-aerial stems like stolons, runners and suckers (Figure 4.15).

Bud
Leafy Shoots

Terminal Bud

Onion Adventitous roots

bulb
Adventitious
roots

a) Bulb b) Corm c) Rhizome

Potato plant
Wild strawberry Runner

Tuber

d) Runner e) Stem cutting f) Tuber

Figure 4.15: Types of vegetative propagations
86 Biology Grade 7

What are the underground stems used for natural vegetative propagations
of flowering plants?

The underground stems of flowering plants that are commonly used for vegetative
propagation include bulbs, tubers, rhizomes, and corms.

Bulbs
For plants such as onions and garlic, the bulb is the
Key Terms
unit of vegetative propagation. A bulb contains an
55Terminal bud: embryonic tissue
underground stem (Figure 4.15a). Fleshy leaves are that supplies cells allowing a
attached to the stem. These leaves contain stored plant to grow in length; found at
food. As the plant grows and develops it will form a the tips of roots and stems.
new bulb underground. 55Lateral bud: an auxiliary or side
bud from which branches grow.

Corms
These are thick underground stems with upright position and function like a bulb.
However, corms consist of a layer of stem tissue storing food instead of fleshy leaves. As
with bulbs, the terminal bud grows into a flowering shoot and the lateral buds produce
new plants. A common example of a corm is crocus (Figure 4.15b).

Rhizomes
Rhizomes are horizontal underground stems that can give new shoots. In some cases
the underground stems are swollen with food reserves. The terminal bud produce the
flowering shoot and the lateral buds may grow out to form new rhizomes. Common
examples of plants that propagate by using rhizomes are Cana indica (Qey abeba in
Amharic) and Ginger (Zingible in Amharic) (Figure 4.15c).

Runners
Runners are also horizontal stems growing from the parent plant, but they grow above-
ground. When their terminal buds touch the ground they take root and produce new plants
(Figure 4.15d). Common examples of plants that can be vegetatively propagated using
stolons or runners are grasses like Cynodon dactylon (“Serdo”) and wild strawberry.

Suckers
A form of budding called suckering is the regeneration of a plant by shoots that arise
from an existing root system. Banana do not produce seeds and are propagated by suckers
that develop from buds on underground stems. Production of new plants is by vegetative
means, and propagation is from suckers that develop at the bases of the old plants.
 Unit 4: Plants 87
Activity 4.11
Examining Natural Vegetative Plant Propagation Methods
Materials you will require:
55 Onion 55 Corms
55 Ginger 55 Serdo
Procedure:
1 Arrange yourself in groups and examine very carefully the plant samples you
are provided with.
2 Identify their axial buds and auxiliary buds and categorize according to their
vegetative means of propagations.

What are the methods of artificial vegetative propagations of flowering

plants?
The methods by which gardeners and farmers commonly vegetatively propagate plants
using non-reproductive parts of the plant is known as artificial vegetative propagation.
The common methods of artificial vegetative propagation methods used by gardeners or
farmers are stem cuttings, layering and grafting.
Stem Cuttings
It is a process in which a vegetative portion from a plant is taken and is rooted in the soil to
form a new plant. The portion used is called a cutting. Stem cuttings are most commonly
used for this purpose (Figure 4.15e). The factors to be considered for cutting are optimal
length with a few nodes and internodes, diameter of the cutting, age of the plant and the
season. Examples of plants that are commonly propagated using stem cuttings include
roses, grapes, sugarcane, and citrus plants.

Grafting
Grafting is a technique of transplanting a part of
one plant on to another plant so that they grow as Scion Graft
one plant. Both plants are selected for their best
characters. The supporting (rooted) portion of the
plant is called a stock, whereas the transplanted
plant is known as scion (Figure 4.16). For Stock
example, the shoot part of one plant that produces ready for Stock
Grafting
large, sweet fruit can be grafted to the rooted
portion of another plant which is drought resistant.
Common examples of plants that can be propagated Figure 4.16: Grafting
using grafting include Citrus fruits (orange and
lemon), rubber, apple, pear, and mango.
88 Biology Grade 7
Layering
Layering is an artificial vegetative
propagation methods during which plants
that have long slender stem are induced to
form roots before it is detached from the
parent plant.

In layering, the lower branch close to the

ground is bent down and covered with
moist soil (Figure 4.17). After some days
roots develop from the branch, which
can be cut and grown independently.
Rhamnus “Gesho” can be propagated by Figure 4.17: Layering
layering.

Activity 4.12

Project work on methods of artificial vegetative plant propagation

Materials you will require:
55 Scalpel
55 Hibiscus (Yachaina rose abeba in Amharic), Geranium or rose plant

Procedure:

1 In groups, remove from the parent plant a portion of rose stem 11 to 20 cm

long with the leaves attached.
2 For most deciduous plants, a tip, simple, or straight cutting will suffice. For
most evergreen plants, use tip or heel cuttings.
3 Remove leaves (or needles) which would contact the rooting medium (the
bottom 4 to 5 cm of stem) to prevent rotting of these leaves. Do not remove
the remaining leaves as they will continue to produce substances that aid in
root formation on the cutting.
4 Prepare the ground by digging not less than 20 cm deep and moisten it. Plant
the cutting into the ground at a depth of 5 cm.
5 Keep the above ground portion of the cutting moist and cool.
6 Observe rooting for not less than 2-3 weeks.
 Unit 4: Plants 89
Activity 4.13
Examining the effect of plant hormones on stem cuttings
Materials you will require:
55 Scalpel 55 Rose plant 55 Auxin powder

Procedure:
1 In groups, prepare 10 rose stem cuttings and the ground for planting as in
Activity 4.12.
2 Prepare auxin solution by adding 5 mg in a liter of clean water.
3 Dip 2/3 of the 5 cuttings into the solution prepared and plant them as
indicated in Activity 4.12. Dip the other 5 into clean water and plant them as
well.
4 Plant them in two rows, row 1 cuttings dipped in rooting solution and row 2
of stem cuttings dipped in pure water.
5 Keep the above-ground portion of the cutting moist and cool.
6 Observe rooting of the cuttings.
55 Do the stem cuttings begin rooting?
55 What do you conclude from this experiment?

Sexual Reproduction in Plants

What are the general characteristics of flowers?

Of all parts of the flowering plant, the flower is the

most unique and ensures efficient sexual reproduction Key Terms
of the plant. A flower is the part of the plant that makes 55Sepals: usually are small green
the seeds. A flower has four specialized parts; sepals, leaves found below the flower.
55Petals: usually are large colorful
petals, stamens, and carpels (Figure 4.18). attractant part of a flower.
55Stamens: a male fertilizing
A carpel is the female part of a flower. Within this organ of a flower, it consists of
closed structure, egg develops, fertilization takes a pollen, anther and a filament..
place, and seed matures. The male part of a flower is 55Pistil or carpel: a female
reproductive organ of a flower, it
the stamen. A stamen contains a filament and an consists of an ovary and a stigma.
anther. An anther has containers within which pollen 55Receptacle: the base of a flower.
grains develop. The functions of the parts of a flower
are given in Table 4.2.
90 Biology Grade 7
Stigma
Anther Carpel
Stament
Style
Filament Ovary

Sepal

Figure 4.18: A longitudinal

section of a typical Petal
flower Receptacle

Table 4.2: Flower parts and their functions

Floral part Function

Petals Brightly colored. They are used to attract insects by their bright
color and scent.
Stamens (has two parts) This is where pollen is made. It is the male part of the flower.
Filament
55 A thin long structure that supports the anther.
55
Anther
55 A sack like structure that contains pollen grains.
55
Carpel (has three parts) The carpel is the green stalk in the middle of the flower:
Stigma
55 top of pistil and where pollen lands on
55
Style
55 the neck of the pistil and supports the stigma
55
Ovary
55 swollen bottom part and contains the ovule, where seed is
55
formed
Sepals Green leaves around the outside of the flower. Sepals are usually
smaller than the petals. Used to protect the flower while it is still
in bud.

A ctivity 4.14
Examining Flowers
Materials you will require:
55 Flowers 55 Blade or scalpel 55 Paper
Procedure:
1 Using a blade dissect flowers provided.
2 Identify the parts and then draw and label the parts as petals, anthers,
filaments, style, stigma, ovary, nectaries, calyx and corolla.

How are flowers designed for sexual reproduction?

Flowers are the reproductive organs of the angiosperms. A flower is the plant organ where
fertilization occurs, seeds are formed and fruits develop. Flowers can have either male
part (stamens), female part (pistil or carpel), or a combination. Flowers that have either
 Unit 4: Plants 91
the male part or the female part are called imperfect Key Terms
(cucumbers, pumpkin and melons). On the other
55Pollinating agents: pollen grain
hand, flowers that have both male and female parts carriers that are involved in
are called perfect (roses, lilies, dandelion). transferring pollen grains from
the anther (part of the stamen)
to the stigma (part of the pistil).
What is pollination? 55Wind pollination: a plant that
uses wind as a pollinating agent.
The process of the transfer of pollen grains from 55Animal pollination: a plant that
the male part (anther) to the female part (stigma) is uses animals as its pollinating
agents.
pollination. Since pollen grains or any part of flowers
55Cross pollination: pollination
can not move by their own, agents that move pollen between flowers of separate
grains from the anther to stigma are required. These plants of the same species.
agents are known as pollinating agents. The agents that 55Self pollination: pollination
within the same flower or between
are involved in transferring pollen grains include wind, flowers of the same plant.
water and animals. The major pollinating agents for 55Perfect flower: a flower that
land plants are wind and animals. Of all animals, insects has both the male (stamen) and
female (pistil) parts.
and birds are the most important pollinating agents
55Imperfect flower: a type of
(Figure 4.19a-c). flower that has either the male
or the female part.
Flowers are adapted in many different ways to ensure
the transfer of pollen grains to stigma. For instance,
pollens of wind-pollinated plants like grasses are
lightweight, smooth, and small.

Plants that are wind pollinated generally occur as

large populations so that the female flowers have a
better chance of receiving pollen. These plants also
produce large numbers of pollen grains.

a) Wind pollinated flower b) Bird pollinated flower (note the c) Insect pollinated flower
(note the stigma that funs pollen grains on the forehead (Example, Rose flower)
out) (Example, Grasses) of the bird) (Example, Hibscus)
Figure 4.19: Pollinating agents

The two types of pollination in flowering plants are self-pollination and cross-pollination.
Self-pollination is a type of pollination during which pollen grains are transferred from
92 Biology Grade 7
the anther to stigma of the same plant. Cross-
pollination is a type of transfer of pollen grains from Did You Know?
anther to stigma of a different plant, which involves Flowers are composed of modified leaves.
two separate plants of the same species. Each floral structure represents a different
modification of a leaf. Not all flowers have the
same parts, but male and/or female structures
are essential.

Activity 4.15
I Comparing Wind and Animal Pollination
In groups, make a comparison between wind and animal pollinated flowers
based on the following characteristics.
Flowers
Character
Wind pollinated Animal pollinated
Petal

Color of petals

Smell

Nectar

Pollen grains

Nature of the anther

II Identifying flowers as wind or animal pollinated types.

Materials you will require:

55 Flowers from different plants
Procedure:
1 In groups, identify the flowers you have obtained from your school compound
as wind or animal pollinated types.
2 Give your own reasons as to why you have categorized the flowers as wind
or animal pollinated type.

III Examining pollen grains

Materials you will require:
55 Scalpel
55 Flowers from different plants
55 Magnifying lens (hand lens/microscope)
 Unit 4: Plants 93
Procedure:
1 Remove the sepals and the petals by pulling down the receptacle of the
flowers.
2 Remove the stamens and crush the anther on a glass slide and prepare a wet
mount and observe it under a microscope. If there is no microscope you can
use hand lens.
3 Do the same for different plants and observe if different plants have similar
pollen grains or not.

What is the unique feature of fertilization in flowering plants?

As pollen grain lands on the stigma of the same plant,

Key Terms
a pollen tube grows through the style to the ovary. The
pollen tube enters into ovule through the opening of 55Pollen tube: a tube that
develops from a germinating
ovary known as micropyle. By the time the pollen tube pollen grain and that carries the
enters the ovule it has two sperm cells. One of these sperm cells of a pollen to the
sperm cells fertilizes the egg (ovum) and the other one ovule of the pistil down through
the style.
fertilizes two polar nuclei. The fertilized egg develops
55Micropyle: an opening of the
into an embryo. The fertilized polar nuclei form an ovary through which the pollen
endosperm (nutritive tissue) of the seed (Figure 4.20). tube delivers the sperm cells to
the ovule.
After fertilization the ovule develops into a seed and
55Ovule: the part of the pistil that
the ovary develops into a fruit that covers the seed(s). contains the egg and the embryo
sac which after fertilization all
together develops into the seed.
Stigma
Pollen tube 55Embryo: the part of the seed
which develops into a new plant.
Style
55Embryo sac: a mature ovule
ready for fertilization.

Polar nuclei
Ovule
Ovary Endosperm
Embryo sac
Sperm

Embryo
Egg
a) Pollen tube development b) Embryo sac c) Fertilization

Figure 4.20: Fertilization in flowering plants

 94 Biology Grade 7

What is pistil?

The female part of the flower, the pistil, is made up of different parts. In fact, it is part of
the flower which fertilizes and develops into a seed. Do Activity 4.16 to identify parts of
the pistil.

Activity 4.16
Examining the pistil
Materials you will require:
55 Scalpel
55 Flowers
55 Magnifying lens (hand lens/microscope)
Procedure:
1 Remove the sepals and the petals by pulling down the receptacle of the
flowers.
2 Get the central part of the flower, the pistil and using the scalpel cut it
lengthwise into two equal halves (Be careful; make sure that your fingers are
out of the way).
3 Use the hand lens to identify parts of the pistil.
4 Draw and label the parts.

How are seeds and fruits formed?

Following fertilization the ovules mature into a seed. The zygote inside the ovule develops
into seed embryo, which consists of the radicle (future root), the plumule (future shoot)
and cotyledon(s). The seed is covered by a seed coat or testa. A seed of an angiosperm
may have one cotyledon (monocot) or two cotyledons (dicot). The embryo in both types
of seeds consists of epicotyls, hypocotyls, radicle, plumule and cotyledon (Figure 4.21).
Seed Coat
Endosperm
Seed Coat

Two Single
Cotyledons Cotyledon

Embryo Embryo

a) A Dicot (Bean) b) A Monocot (Corn)

Figure 4.21: Seeds of dicot and monocot
 Unit 4: Plants 95
Activity 4.17 Did You Know?
¸¸The endosperm of a monocot seed is larger
Studying parts of the seed than the dicot seed. In general, monocots
Materials you will require: tend to store food in their endosperms, and
nutrients are transferred to the cotyledon.
55 Soaked (for a day or two) seeds of
In contrast, many dicots tend to store food
bean and corn (maize) in their cotyledons, where the endosperm
Procedure: is reduced to a papery coating around the
1 In groups, examine the seeds carefully by embryo.
removing the external soft cover (may be
impossible for a corn seed).
2 Identify the parts of the seeds and discuss
their respective functions.

Exercise 4.2
Choose the best answer for each of the following questions
1 One of the following statements is false about flowering plants.
A They all have flowers.
B They all have stems, roots and leaves.
C They all form seeds and fruits.
D None of the above.
2 Flowers can be characterized as:
A vegetative means of reproduction of flowering plants.
B always perfect types.
C do not have sterile parts.
D being modified to be pollinated by different agents.
3 One of the following is common for both monocots and dicots.
A Parallel venation.
B Fibrous root system.
C Number of petals in fours.
D Production of seeds.
4 The site of plants in which gas exchange with the environment takes place is:
A epidermis. C stomata.
B mesophyll tissue. D vascular bundles.
5 One of the following is used as a pollination agent for teff:
A Birds C Butterflies
B Bees D Wind
96 Biology Grade 7
Unit Summary
ŒŒ Plants are photosynthetic organisms and are diverse types.
ŒŒ Plants can be classified into non-flowering and flowering plants (angiosperms).
ŒŒ Non flowering plants include mosses, ferns, and gymnosperms. They have no
flower and except gymnosperms, the others do not produce seeds.
ŒŒ Flowering plants, which are also known as Angiosperms are the only group of
plants that, have flowers as their sexual reproductive structures.
ŒŒ Flowers are organs of sexual reproduction in Angiosperms.
ŒŒ Flowering plants are economically the most important group of plants.
ŒŒ A flowering plant has three major parts namely; the stem, the leaf, and the
root. At maturity these plants will have an additional fourth component, the
flower.
ŒŒ The root is a plant part that grows underground and anchors into the soil.
ŒŒ The root absorbs water and minerals from the surroundings, it supports the
plant, conducts absorbed water and minerals to the above-ground parts of
the plant, and stores food.
ŒŒ The main (primary) root, lateral roots, root hairs, root tip and root cap form the
underground plant system or the root system.
ŒŒ The two main kinds of root system in plants are the tap root system and the
fibrous root system.
ŒŒ All plant body parts, the stem, the leaf and the root have similar internal
features. Especially the stem and roots of higher plants have the outer
covering epidermis, the cortex, vascular elements and the pith to the centre.
ŒŒ The stem is part of a plant which is found in the above-ground, above the
soil. The leaf and flower (at the time of maturity) together make up the shoot
system (above ground system) of the plant.
ŒŒ Based on softness or toughness of the stem, there are two types of flowering
plants: herbaceous (non-woody) and woody.
ŒŒ The main functions of stem include erecting the plant above the ground
so that it receives maximum sunlight. It is involved in transporting water
and minerals from the root to other parts of the plant, supporting above
ground part like leaves and flowers; even fruits. It also serves in transporting
photosynthetic products from leaves to other parts of the plant.
ŒŒ The leaves are responsible for both converting sunlight, water, and carbon
dioxide into food through photosynthesis and gas exchange.
ŒŒ The main parts of the leaf include the blade (lamina, the broad part), the mid
rib and a petiole (leafstalk) that fixes it to the stem.
ŒŒ The two main groups of flowering plants are the monocots and the dicots.
ŒŒ The monocots have one cotyledon and dicots have two cotyledons in their
seeds.
ŒŒ Flowering plants reproduce both sexually and asexually.
ŒŒ Vegetative propagation by stem includes both underground stems such
as tubers, rhizomes, and corms or sub-aerial stems like stolons, runners and
suckers.
 Unit 4: Plants 97
ŒŒ A flower is the part of the plant that makes the seeds. A flower has four
specialized parts; sepals, petals, stamens, and carpels.
ŒŒ Pollination is the process of the transfer of pollen grains from the male part
(anther) to the female part (stigma).
ŒŒ The two types of pollination in flowering plants are self-pollination and cross-
pollination.
ŒŒ The major pollinating agents for land plants are wind and animals.
ŒŒ When pollen grain lands on the right stigma it germinates and develops pollen
tubes. The pollen tube carries the sperm cells to the ovule, where fertilization
occurs.

? Review Exercise for Unit 4

Ajsjsdf AjsjsdfAjsjsdf
AjsjsdfAjsjsdf Ajsjsdf

AjsjsdfAjsjsdf Ajsjsdf
AjsjsdfAjsjsdf Ajsjsdf

AjsjsdfAjsjsdfAjsjsdf Aj
Ajsjsdf AjsjsdfAjsjsdf

Ajsjsdf AjsjsdfAjsjsdf
AjsjsdfAjsjsdf Ajsjsdf

AjsjsdfAjsjsdf Ajsjsdf
AjsjsdfAjsjsdf Ajsjsdf

..............
..............
..............
Ajsjsdf

Part I: Choose the best answer for each of the following questions
1 One of the following is not a flowering plant.
A A barely plant C A pumpkin plant
B A papaya plant D A fern
2 Which one of the following does not form the internal tissues of stems and roots?
A Epidermis C Vascular bundles
B Cortex D None of the above
3 One of the following is not part of the shoot system.
A Stem C Leaves
B Flowers D None of the above
4 In one of the following structure and function is wrongly associated.
A Epidermis – protection C Root cap – protection.
B Mesophyll tissue – gas exchange. D Vascular bundles – transport.
5 One of the following is not used as a means of artificial vegetative propagation method
A Stem cutting C Layering
B Grafting D Seed sowing
Part II: Match correct terms/meaning given in column ‘B’ with their items given in
column ‘A’ .
Column A Column B
6 Mosses A Tid plant
7 Ferns B Fruit forming plants
8 Gymnosperms C Dry area
9 Flowering plant D Underground stem
10 Succulent E Moist place
98 Biology Grade 7
Part III: Fill in the blank spaces with correct answers.
11 ________ is the process of food making in plants.
12 The vegetative body parts of a higher plant is made up of ________, ________ and
________.
13 ________ and ________ are sex organs of a flower.
14 The two types of pollination of flowering plants are ________ and ________.
15 Endosperm is formed by the union of ________ and ________.
Part IV: Give short answer to the following questions.
16 List down the major groups of plants that do not posses flower.
17 Write down the major body parts of a flowing plant and give one function for each.

Part V: Copy the crossword puzzle below and use the numbered clues to complete and
solve the puzzle.
4

10 2

The numbers in the brackets show the number of letters in each word.

Across
6 The neck of a pistil (5)
9 Part of a stamen that contains pollen grains (6)

Downward
2 Part of a pistil that contain an egg (5)
4 The swollen lower part of a pistil (6)
10 Brightly coloured part of a flower (5)
 Unit
Animals
5
Unit Outcomes
By the end of this unit, you will be able to:
”” tell that animals are diverse in size, type
and distribution, demonstrate love and
respect to them and explain why insects
are the most diverse group of animals;
”” define metamorphosis, explain complete
and incomplete metamorphosis and give
examples of insects that reproduce by
complete and incomplete metamorphosis;
”” describe how tsetse flies, army worm and
maize borer affect humans and explain
the methods of controlling them;
”” explain the characteristics specific to
social insects and give examples of social
insects;
”” explain the roles of queen, drones and
Main Contents
workers in bees, explain methods of bee 5.1 Diversity of Animals
keeping and management of beehive,
demonstrate the techniques of harvesting 5.2 Life Histories of Some Insects
honey and compare a modern beehive 5.3 Some Economically Important Insects
with a traditional one; and 5.4 Social Insects
”” construct a model of modern beehive,
ŒŒ Unit Review
appreciate the behaviour of social insects
and express an interest to investigate
more about social insects.
100 Biology Grade 7
Introduction
The word “animal” comes from the Latin word animale, meaning vital breath or soul. In
everyday usage, the word refers to non-human animals. The biological definition of the
word refers to all members of the Kingdom Animalia including humans.

Animals can be grouped into two main groups: Vertebrates and invertebrates. The main

difference between vertebrates and invertebrates is that invertebrates do not have a
backbone or a spinal column. Examples of vertebrates include humans, birds and snakes
while examples of invertebrates include insects and flatworms.

There are several types of animals living under different conditions. Some animals live in the
wild, some live with humans, some are very large and others are very small. In this unit, you
will study the diversity of animals, and insects as the most diverse group of animals, including
their life history. Some economically important insects (tsetse fly, dark moth – armyworm, and
maize borer moth) and social insects including the honeybee are discussed.

5.1 Diversity of Animals

By the end of this section, you will be able to:
”” tell that animals are diverse in size, type and distribution;
”” demonstrate love and respect to animals;
”” explain why insects are the most diverse group of animals.

Diversity of Animals

How diverse are animals?

Animals are diverse in size, type, and distribution. There are many types of animals. The
two main groups are vertebrates and invertebrates (see Table 5.1). See Figure 5.1, 5.2 and
5.3 for different sizes and types of animals.
Table 5.1: Comparison chart of vertebrates and invertebrates
Features Invertebrate animals Vertebrate animals
Characteristics Animals without backbone Animals with back bone
Numbers 98% of the animal species 2% of the animal species
Size Small Big
Examples Insects, flatworms, round worms, Humans, snakes, fish, birds etc
snails etc.
 Unit 5: Animals 101
How are animals different in size?
Key Terms
Animals show differences
in size from very large to 55Vertebrates: Animals which
very small. An elephant have backbone or spinal
column.
is a large animal while a Centipede Termites 55Invertebrates: Animals
rat is a small animal, and which do not have backbone
a housefly is smaller than or spinal column.
both. 55Terrestrial animals: Animals
Honeybee living on land.
55Arboreal animals: Animals
Mite living on the branch of trees
in the forest.
55Aquatic animals: Animals
which live in water.
Bug
55Aerial animals: Animals
Snail living in air.
Figure 5.1: Invertebrate animals

How are animals distributed?

Animals live in various
environments such as land, sea, Birds
air, forests, soil etc. Animals such
as cattle and lions live on land and
use limbs to walk. Land animals Fish Bat (mammal)
have toes that produce claws and
hooves for walking, climbing, and
running. Animals living on land
are called terrestrial animals. Reptile Monkey (mammal)
Frog (amphibian)
Animals such as monkey and Goat (mammal)
apes live on trees. They use their
limbs to climb. Some animals
travel slowly along branches Figure 5.2: Some vertebrate animals
of trees. Animals living on the
branch of trees in the forest are Key Terms
called arboreal. 55Amphibian: Animals living in
water and on land.
Animals such as fish and whale live in water. They use
55Reptile: Animals living on land
their fins to swim. Animals, which live in water moved by crawling and with
environment are called aquatic animals. Whales, horny scale covered body.
which live in water, are the largest known animals. 55Mammals: Animals which
Some animals such as birds and bats live mostly in the the female gives birth to live
air. They use their limbs to fly. Animals living in air young and can feed them
are called aerial animals. with their own milk.
102 Biology Grade 7

Activity 5.1
Observe and Group Animals
55 Look at Figure 5.3 and fill in the table.
Wild animals Domestic animals

55 Which animals in Figure 5.3 is the largest, and which is the smallest? Are they
Vertebrates or invertebrates?
55 Make a visit of your school compound and record the type of animals you
see. Look into every surface including the soil.
55 What type of organisms are found in large numbers and variety in your locality?
55 Name some animals which live in Ethiopia.

An elephant Lion Zebras

Cow Hyena

Giraffe Monkey Donkey

Figure 5.3: Some large Mammals

Activity 5.2
1 What are the uses of animals - wild and domestic animals.
2 Name types of wild animals found only in Ethiopia and reason why we
should take care of them.
3 How do you show your love and respect for animals.
 Unit 5: Animals 103
Why are insects the most diverse group of animals?
Insects are among the most diverse groups of animals on the planet. They include more than
a million described species and represent more than half of all known living organisms.
Insects may be found in nearly all environments, although only a small number of species
occur in the oceans.
Insects are the most diverse group of animals because:
55 they are able to live in different habitats,
55 they are able to adapt to the different physical conditions in which they are found,
55 they are able to adapt to changing conditions,
55 they are able to reproduce rapidly.
Show love and respect to animals as they are useful for humans and they have the right to live.

Exercise 5.1
I Choose the most exact answers for the following questions.
1 Which of the following animals live in holes of a ground?
A Termites C Honey bees
B Birds D Snails
2 Which of the following animals live on trees?
A Zebras C Lions
B Monkeys D Hyenas
3 The habitat of a fish can be a
A lake C forest
B mountain D land
4 Insects are found in many places because of their
A ability to adapt C ability to fly
B body size D abdomen
5 Which of the following is the largest animal?
A Lion C Elephant
B Whale D Donkey

5.2 Life Histories of Some Insects

By the end of this section, you will be able to:
Word Roots and Origins
”” define metamorphosis as a change of
Insects from Latin insectum meaning cut into
form of an animal involving several
distinct stages; sections.

”” explain complete and incomplete metamorphosis; and

”” give examples of insects that reproduce by complete and incomplete
metamorphosis.
104 Biology Grade 7
Insects Eye Antenna Head
Fore Wing
Fore Leg
What are Insects?
Insects are a class of living creatures that have
Thorax
segmented bodies supported by an exoskeleton, Hind Wing
a hard outer covering made mostly of chitin Middle Leg
(chitinous exoskeleton). Abdomen Hind Leg

The segments of the body are organized into

three distinctive but interconnected units: a head, Figure 5.4: External structure
a thorax, and an abdomen (see Figure 5.4).  of insects

The head consists of a pair of sensory antennae, a pair of compound eyes, and, if present,
one to three simple eyes and mouthparts.
The thorax has three segments and six segmented legs. One pair of legs on each segment
of the thorax. If wing’s are present in the species, there are two or four wings.

The abdomen consists of eleven segments, though in a few species of insects these
segments may be fused together or reduced in size. The abdomen also contains most of
the digestive, respiratory, excretory and reproductive internal structures.

Metamorphosis
Key Terms
What is metamorphosis? 55Instar: each stage between
moults in incomplete meta-
A fundamental difference between insects and morphosis in insect life cycle.
other animals is that as insects grow, their bodies 55Moult: removal of outer
completely change their form. This process is called body cover.
metamorphosis. 55Nymph: wingless stage
hatching out from egg in
some insects which looks like
There are two types of metamorphosis in insects:
adult except it is small.
Complete and Incomplete metamorphosis. 55Metamorphosis: complete
55 Complete metamorphosis involves a change of body.
complete change of form involving four 55Hatch: keeping warm until
young break out of egg.
main stages: egg, larva, pupa and adult.
55Larvae: an active feeding
55 Incomplete metamorphosis involves a worm like stage of life coming
gradual development involving only three out of egg in insects.
stages: egg, nymph and adult. The nymph 55Caterpillar: the larvae of
butterfly, moths, etc.
closely resembles the adult except it is 55Pupa: the inactive, non-
smaller and wingless. feeding stage of life after
larval stage in insects.
 Unit 5: Animals 105
Incomplete Metamorphosis
What processes take place in the life cycle of grasshoper?
The following processes take place in the life cycle of grass hoppers.
55 The desert locust is a species of grasshopper. It develops by incomplete metamorphosis,
i.e., there is no larval stage (see Figure 5.5).
55 The eggs hatch into wingless nymphs, which resemble miniature, incomplete adults.
55 In order to grow, the nymph needs to shed its hard outer skin (cuticle) and expand its
body before the new cuticle hardens.
55 Each stage between molts is called an instar. At each moult, the nymph develops more
adult features until after the fifth moult when it is a fully formed adult with wings.
55 For the first five instars, the nymphs are called ‘hoppers’ and move by crawling or
hopping along the ground. They feed on the natural vegetation by cutting off pieces
with their jaws.
55 When they develop wings, they fly to a new area where they feed, mate and reproduce.
55 The female extends her abdomen to about 5 cm below the surface of damp sandy soil
to lay the eggs. The eggs hatch in 10 – 20 days, depending on the temperature.

ult
About 2 weeks th Mo
5
ADULT
ADULT
4th Moult

5th stage nymph

EGG EGGS
4th stage nymph
NYMPH
ult

in g
Mo

tc h
rd
3

Ha

33rdrdstage
stagenymph
nymph

ult
4 − 7 weeks Mo
o ult 1st stage
1st M
2 nd
Moult several times 2nd stage Nymph
ADULT nymph

Figure 5.5: Incomplete metamorphosis in Grasshopper

Complete Metamorphosis

What processes take place in the life cycle of butterfly?

The following processes takes place in the life of butterflies.

55 The butterfly lays its eggs on the underside of leaves. For example, cabbage
(see Figure 5.6).
55 The eggs hatch into larvae (caterpillars) which feed on leaves and grow
rapidly, moulting the outer layer of their ‘skin’ (cuticle) as they do so.
106 Biology Grade 7
55 Just before its final moult, the caterpillar attaches itself to a wall or tree by
means of its clasper and a girdle of silk. Rhythmic contractions split the
cuticle, which is then shed.
55 The caterpillar has now become a pupa. Its organs have taken on a form that
will later become a butterfly. The cuticle begins to darken and hardened outline
of the butterfly’s external structures can be seen in the pupa. The pupa will stay
dormant over winter; then the cuticle will split and the butterfly will emerge.
1
Eggs
Eggs
2
Caterpillar
Larva
3
Pupae

Adult
4
Chrysalis
Moth
Figure 5.6: Stages of complete metamorphosis of butterflies

Activity 5.3
Examining Insect Life Cycles
You need to collect houseflies and mosquitoes including the various stages in their
life cycles.
1 Examine the stages in the life cycle of the housefly and identify the following
life stages. An egg, A caterpillar, A pupa and A housefly; what kind of
metamorphosis is it?
2 Draw the life cycle of a mosquito?

Exercise 5.2
I Choose the correct answers for each of the following questions.
1 Incomplete metamorphosis does not include
A egg stage C nymph stage
B larval stage D adult stage
2 During complete metamorphosis larval stage is followed by,
A egg C pupa
B adult D nymph
3 Which one of the following insects do not shows complete metamorphosis?
A housefly C honey bee
B butter fly D locust
 Unit 5: Animals 107
4 Moulting is:
A shedding of exoskeleton C harmful to insects
B shedding of leg D used to lay egg
5 Both nymph and larva
A look like the adults C hatch from eggs
B are able to reproduce D all of the above

5.3 Some Economically Important Insects

By the end of this section, you will be able to:
Key Terms
”” describe how tsetse flies affect
humans and animals; 55Vector: a carrier of disease
causing organisms.
”” explain the methods of control of 55Anaemia: disease of the
tsetse flies; blood.
”” describe how armyworm damages 55Sleeping sickness: name
crops; given for the disease caused
by trypanosomite in humans.
”” explain the methods of control of
armyworms; 55Pest: harmful insects and
other small animals.
”” describe how maize borers damage 55Insecticides: chemical
maize; and substances used to kill
”” explain the methods of control of insects.
maize borers.

Some Economically Important Insects

What are Economically important insects?

Some insects are of great economic importance; some are harmful while others are
beneficial to human beings. Insects such as tsetse fly, dark moth and maize stock borer
moth are economically harmful.

Tsetse fly

How are tsetse flies economically harmful?

The tsetse fly is a harmful pest that affects both cattle and people. Tsetse flies are vectors
of the diseases known as Trypanosomiasis or Tryps (sleeping sickness in humans and
Gendi in cattle) with common symptoms such as intermittent fever, progressive anaemia
and loss of weight. Tsetse flies are commonly found along the edges of lakes and banks
of rivers. Vector control consists of two practical interventions, trapping and spraying the
Tsetse fly (see Figure 5.7).
108 Biology Grade 7

What are the methods of controlling tsetse fly?

The following are some of the methods used to control tesetse flies.
55 Removing bushes and undergrowth along streams to reduce tsetse fly
populations.
55 Spraying areas known to shelter the tsetse flies with insecticides.
55 Spraying livestock with insect repellent.
55 Trapping tsetse flies by traps.

Figure 5.7: A tsetse fly and a trapping apparatus

Activity 5.4
Reading and Evaluation
Controlling trypanosomiasis can be achieved by the release of large numbers of
sterile male tsetse flies into an area. These sterile males mate with females but no
offspring are produced hence the population falls. Read about this method and
discuss how it is used. Evaluate this method when compared with other traditional
methods of control and discuss in class.

Army Worm

What is the Dark moth (Armyworm)?

The African armyworm is not a worm at all but it is the larval stage of the night flying
moth (see Figure 5.8). The larval stages of moths and butterflies are called caterpillars.
55 Caterpillars can be hairy, spiny and have unusual shapes.
55 They have large powerful jaws adapted to cut and chew leaves.
55 Caterpillars are very greedy eaters. If they become too numerous they can
soon finish the leaves a tree. It is these larval forms or caterpillars that cause
much damage to agricultural crops.
55 Most adult butterflies and moths feed on nectar.
55 The larvae have biting mouthparts and the adults have sucking mouthparts.
 Unit 5: Animals 109

Figure 5.8: Adult Butterfly, Caterpillar and Armyworms moving in mass

The term armyworm is given to the armyworm because it advances in a mass across a field
consuming the grass as they go. Armyworms attack maize, sorghum, wheat, barley, millet,
teff, rice, sugarcane and rangeland grasses. They do not attack vegetables, tea and coffee.

Within a few days, all plants in a field may be covered with black caterpillars. Larvae first
eat the upper and lower surface tissue of leaves. This results in windowing of the leaves
with big swarms, the entire leaves are eaten. This results in severe crop loss.

What are the methods used to control armyworms?

The following traditional methods can be used to control armyworms.

55 Use of moth traps to protect infestations.
55 Using cut branches from trees to ‘brush’ the caterpillars off the plants.
55 Driving herd of cattle, sheep, and/or goats back and forth across affected areas .
55 Dragging thorn bushes or beating the infested areas with sticks and branches.
55 Collecting larvae by hand.
55 Letting chickens feed on larvae.

Traditional control measures are only effective for

Key Terms
small areas. In large areas with heavy infestation, the
pests have to be sprayed with pesticides from the air. 55Armyworms: are caterpillars
that move in mass as armies
The disadvantage of this method is that useful insects and consume grasses on
are also destroyed. their way.

Maize Stalk Borer Moth

What is maize stalk borer moth and its importance?

Maize stock borer is a species of moth that is also known as the maize stalk borer. It is
known as “Ageda Korkur” in Amharic. Adults are pale brown and the wingspan is
35 – 40 mm. The larvae feed on various grasses, as well as sorghum and sugar cane (see
Figure 5.9).
Eggs are laid in a long column stretching up the stem, under a leaf sheath. They hatch
after about 10 days.
110 Biology Grade 7
The larvae are called caterpillars and they crawl up the plant into the funnel and feed on
the leaves. This results in characteristic lines of holes and “windows”. The shoot may turn
yellow and die. If the plant dies, the caterpillars will move to another plant.

Adult

Hole made on stalk by larvae Larva in stalk

Figure 5.9: Maize stalk borer moth

The mature caterpillar cuts a hole in the stem before pupating within the tunnel. Eventually
the moth will use this hole to emerge.
The leaves of young plants have holes and “windows”. When the attack is severe, the
central leaves die. In older plants, the caterpillars of the first generation bore in the main
stem. Some caterpillars bore in the cobs. Damage to sorghum is usually less serious than
damage to maize.

Activity 5.5
Group Work and Discussion
1 Ask people to tell you some economically harmful insects, which damage crops
in your community. Ask their name, how they harm, and the method of control
people use.
2 Visit the health facility and ask what kinds of insects are involved in the transmission
of disease in your community. Ask the name of the insect, the disease transmitted,
how it is transmitted and the method of control.
3 Write a report of your investigation in groups. In the report, write what you can
do to control the harmful insects in your community. Discuss about the methods
of control in class.

Exercise 5.3
I Choose the best answer for each of the following questions
1 Which one of the following is a vector?
A Dark moth C Tsetse fly
B Grasshopper D Butterfly
2 Which of the following form a swarm that attacks crops?
A tsetse fly larvae C honeybee larvae
B moth larvae D housefly larvae
 Unit 5: Animals 111
3 Sleeping sickness is
A a disease of cattle C a disease of people
B a disease of crops D a disease of insects
4 Caterpillars are ________ stage of insects
A adult C pupa
B larvae D nymph
5 Larval stages of insects moving in mass is called
A Caterpillar C Armyworm
B Instar D Swarm

5.4 Social Insects

By the end of this section, you will be able to:
”” explain the characteristics specific to social insects;
”” give examples of social insects;
”” explain the roles of queen, drones and workers in bees;
”” explain methods of bee keeping and management of beehive;
”” demonstrate the techniques of harvesting honey;
”” compare a modern beehive with a traditional one;
”” construct a model of modern beehive;
”” appreciate the behavior of social insects; and
”” express an interest to investigate more about social insects.

Social Insects

What are social insects and their characteristics?

Insects that live together in communities or colonies are called social insects. The main
groups of social insects are bees, ants and termites.

Social insects live together in large groups or colonies and share out the work needed to
sustain the colony between them. Different casts of the insect carry out different duties
within the colony.
All social insects possess the following common characteristics.
55 Large populations (colonies) 55 Swarming
55 Elaborate nests 55 Communication and
55 Parental care, 55 Division of work.
55 Protective devices
112 Biology Grade 7

Activity 5.6
Individual Library Assignment
1 Give examples of social insects.
2 What are the advantages of living in a large social group to the insects?
3 Why are honeybees considered as social insects?

The Honeybee
What are the castes of honeybee?

Honey bee is a social insect which produce honey. A colony

of bees consists of three castes of bee (see Figure 5.10). Queen
They are queen, drone, and worker castes.

What is a Queen Bee?

Drone
55 There is only one queen bee per hive.
55 The queen is the only bee with fully developed ovaries.
55 A queen bee can live for 3 – 5 years.
Worker
55 The queen mates with several male bees Figure 5.10: Castes of
(drones), and will remain fertile for life. honeybee

55 She lays up to 2000 eggs per day.

55 Fertilized eggs become female (worker bees) and unfertilized eggs become
male (drone bees) (See Figure 5.11).
55 When she dies or becomes unproductive, the other bees will “make” a new
queen by selecting a young larva and feeding it a diet of “royal jelly”.
55 For queen bees, it takes 16 days from egg to emergence.

Queen lays Worker feeds Larva reaches Worker seals Larva becomes Adult bee
egg in wax cell hatched larva full growth cell a pupa leaves cell

Figure 5.11: The process of honeybee hatching

 Unit 5: Animals 113
What is a Worker Bee?

55 All worker bees are female, but they are not able to reproduce.
55 Worker bees live for 4 – 9 months during the winter season, but only 6 weeks
during the busy summer months (they literally work themselves to death).
55 Nearly all of the bees in a hive are worker bees.
55 A hive consists of 20,000 – 30,000 bees in the winter, and over 60,000 –
80,000 bees in the summer.
55 The worker bees sequentially take on a series of specific tasks during their
lifetime (see Table 5.2).
Table 5.2: Periods of work activity of worker bees

Period Work activity

Days 1 – 3 Cleaning cells and incubation

Day 3 – 6 Feeding older larvae

Day 6 – 10 Feeding younger larvae

Day 8 – 16 Receiving honey and pollen from field bees

Day 12 – 18 Wax making and cell building

Day 14 onwards Entrance guards; nectar and pollen foraging

55 For worker bees, it takes 21 days from egg to emergence. The worker bee has
a barbed stinger that results in her death following stinging, therefore, she can
only sting once.

What is a Drone Bee?

55 A drone bee is a male which mates with the queen.
55 These male bees are kept on standby during the summer for mating with a
virgin queen.
55 Because the drone has a barbed sex organ, mating is followed by death of the drone.
55 There are only 300-3000 drones in a hive.
55 The drone does not have a stinger. Because they are of no use in the winter, drones
are expelled from the hive in the autumn.
114 Biology Grade 7
Key Terms
How do honeybees communicate?
55Waggle dance: a term used
A honeybee that discovers a new food source will for a particular figure-eight
dance of the honeybee.
tell other honeybees about its location through the
55Round dance: circular dance
honeybee dance. When a worker bee returns from an pattern by honey bee.
abundant food source, she will dance inside their nest 55Nectar: Sweet fluid produced
in a circle. The dancer wiggles her abdomen while by flowers is 60% water and
40% solids. This is collected
crossing the circle made by round dance. by the bees and converted
into honey at 17 – 18%
Waggle dance is a term used for a particular number moisture content.
8 – like dance of the honeybee. 55Super: the supplementary
wooden boxes placed on top
of the hive body to expand
Methods of Beekeeping the size of the colony, and to
provide for storage of surplus
honey.
What is beekeeping?
Beekeeping is the maintenance of honey bee colonies, commonly in hives, by humans.
A beekeeper keeps bees in order to collect honey and beewax, to pollinate crops, or to
produce bees for sale to other beekeepers.

What are beehives?

A beehive is an enclosed structure in which honeybees live

and raise their young. Natural beehives are naturally occurring
structures occupied by honeybee colonies, while domesticated
honeybees live in manufactured beehives, often in an apiary
(Figure 5.13). These manufactured structures are typically
referred to as “beehives”. Figure 5.12: Natural
beehive on tree
The beehive is internal structure with a densely packed matrix of hexagonal cells made
of beeswax, called a honeycomb. The bees use the cells to store food (honey and pollen)
and to house the “brood” (eggs, larvae, and pupae).

Traditional (Fixed comb) hive: is a hollow structure Key Terms

made of cheap materials like clay, straw, bamboo, false
55Beehive: it is an enclosed
banana leaves, logs, barks of tree, and animal dung. structure in which honeybees
The bees fill all the available space with honeycombs live and raise their young.
from the top downwards. The honeycombs cannot be
removed since they are attached to the top and the
sides of the hive. The honey can be removed only by
removing one wall of the hive and breaking or cutting
out the honeycomb (see Figure 5.13).
 Unit 5: Animals 115

Hive made of mud Hive made of bamboo

Hives made of wood Hives made of mud and grass

Figure 5.13: Different types of traditional hives in Ethiopia

Modern Hive (Hive with Frames) is a brood (offspring) chamber (box) with a fixed
bottom board and flight board. In the bottom board, there is a ventilation hole (15 cm × 30 cm),
which can be covered with fine wire mesh or other suitable materials. The brood chamber
holds ten frames, which are kept separately at the right distance by means of a side bar,
or nails. Queen excluder (not necessary) placed horizontally on top of the brood chamber.

Figure 5.14: A man made modern hive

Activity 5.7
Talk to a beekeeper about bee keeping and demonstrate some of the techniques used.
116 Biology Grade 7

What is the importance of beekeeping?

Honeybees are important for humans.

People keep honeybee for their economic importance. Honeybees are important pollinating
agents of crops and give various products such as:
55 Honey 55 Pollen 55 Propolis
55 Beeswax 55 Queen jelly
These products can be sold to get money or used for various purposes.

Pollen

Pollen is the male germ cells produced by all flowering plants for fertilization and plant
embryo formation. The Honeybee uses pollen as a food. Pollen is one of the richest
and purest natural foods, consisting of up to 35% protein, 10% sugars, carbohydrates,
enzymes, minerals, and vitamins.

Honey

The bees use honey for food all year round. There are many types, colors and flavors
of honey, depending upon its nectar source. The bees make honey from the nectar they
collect from flowering trees and plants. Honey is an easily digestible, pure food. Honey is
hydroscopic and has antibacterial qualities.

Beeswax

Secreted from glands, beeswax is used by the honeybee to build honey comb. It is used by
humans in drugs, cosmetics, artists’ materials, furniture polish and candles.

Propolis

Collected by honeybees from trees, the sticky resin is mixed with wax to make a sticky
glue. The bees use this to seal cracks and repair their hives. It is used by humans as a
health aid, and as the basis for fine wood varnishes.

Royal Jelly

Royal jelly is the powerful, milky substance that turns an ordinary bee into a Queen Bee. It is
made of digested pollen and honey or nectar mixed with a chemical secreted from a gland in
a nursing bee’s head. It commands higher prices, and is used by some as a dietary supplement
and fertility stimulant. It is loaded with all of the B vitamins.
 Unit 5: Animals 117
Management of Beehives
How should a beehive be managed?
Management of beehives includes:
55 Preparing modern hives
55 Selecting proper place for the hive where water and flowers are available
55 Protection of a hive from disturbance and enemies
55 Knowledge of proper method of honey harvesting
55 It is possible to harvest some of the honey made by bees but the beekeeper
should leave sufficient for the needs of the colony of bees.
55 Knowledge of forming new colonies
55 Monitoring colonies carefully for the appearance of queen cells, which are a
signal that the colony is determined to swarm and for signs of disease.

Techniques of Harvesting Honey

What is the technique of harvesting honey?

Honey is harvested from the super of the hive following

careful procedures (see Figure 5.15 ‘a’ and ‘b’).
Did You Know?
55 protection methods of bee sting during Honeybees are not aggressive by nature, and
harvest. will not sting unless protecting their hive from
an intruder or are unduly provoked.
55 knowledge of the bees is the first line of
defense.
55 wearing protective clothing is the second line of defense. The protective
clothing is generally light coloured (but not colourful) and of a smooth
material.
55 smoke is the beekeeper’s third line of defense. Smoke calms bees.

Activity 5.8
I Library Assignment
1 Why is it advisable to leave some of the honey in the colony when harvesting
honey?
2 What is the economic importance of beekeeping, both in terms of pollinating
crops, and obtaining products from the hive?
3 What is the use of the following? Honey, Beeswax, Pollen, and Queen Jelly.
4 What is the advantage of using a modern beehive?
118 Biology Grade 7

a) b)
Figure 5.15: Harvesting honey with protective clothing and using smoke

Most beekeepers use a “smoker” – a device designed to generate smoke from the
incomplete combustion of various fuels.

Comparing a Traditional and a Modern Beehive

Traditional hive Modern hive
Frames not removable and difficult to Removable frames which allow the apiarist to
inspect. inspect for diseases and parasites.
Not easy to form new colony. Movable frames also allow a beekeeper to
more easily split the hive to make new colonies.
No re-using of comb thus decrease the Re-using comb can thus increase the
productivity. productivity of a beekeeping enterprise.

Bee are damaged during honey harvest Safe to bee during harvest only extra honey is
yields more beeswax but less honey. harvested. Yields more honey but less beeswax

Activity 5.9
Work in small groups and write a group report
1 Discuss how bees are able to communicate with each other through various
dances, to indicate the source of food.
2 Discuss the ability of honeybees to live together in a hive and how that
increases the chances of their survival.

Construction of a Model Beehive

How is model modern beehive constructed from locally available materials?
For bees to give us their products they need to be kept in hives and provided with necessary
services. Providing the proper hives with enough space together with enough food supply
(flowers) are considered to be very important in bee farming. Construction of suitable
hives is very crucial in beekeeping practice in order to harvest the yield, inspect and
manage the hives without disturbing, annoying and killing bees.
 Unit 5: Animals 119
In our country almost all beekeeping practices by the rural farmers are done in a very
traditional way, with traditional hives (Figure 5.16). The traditional hollow log hives are
hanged in long trees. These hives make the activities of inspection, management and
harvesting very difficult.

Figure 5.16: The traditional cylindrical hives

Traditional hives which are made from clay pots, barrels and most containers can easily be
modified into modern top-bars hives. The important thing in modern hives is to maintain
the proper, equal distance between the combs. In Ethiopia it is possible to construct an
alternative, easy, economical and productive top bar like hives from locally available
materials at the farmer level.

Activity 5.10
Constructing a model top bar modern beehive from local material.
Materials you require
55 Hard paper or cardboard
55 Measuring tape
55 A pair of scissor
55 Glue

Procedure
1 In groups observe Figure 5.17 very carefully and the box should have a height
of 30 cm and width of 40 cm at the top and 22 cm of at the bottom.
120 Biology Grade 7
2 Cut the hard paper and prepare two pieces of 1 m X 40 cm for the top cover
and 1 m X 22 cm for the bottom covers.
3 Cut the hard paper and prepare again two pieces of 1 m X 30 cm for the side
covers.
4 Prepare two pieces of 40 cm X 30 cm and 22 cm X 30 cm for the front and
rear side covers.
5 Cut 2 cm X 10 cm on the 40 cm X 30 cm (front side cover you have already
prepared) and set an entrance for bees
6 Measure and cut appropriate partition board at the middle.
7 Stick all sides with a glue together.

Figure 5.17: Model top bar hive

Activity 5.11 Key Terms

55Termite mound: large nest
Work in small groups and write a group made from clay, sand and
their saliva by termites with
report the nest chamber above
ground level.
Research into how the life of solitary wood
bees differs from that of the honeybee and
another social insect such as the termite and Did you know?
make comparisons with the honeybee. ¸¸Termite colonies eat non-stop, 24 hours a
day, seven days a week.
¸¸Termites have wings that they shed once
they have found a good place to build a
nest.
 Unit 5: Animals 121
What are termites?
Termites are social insects and raise their young as a group. They are organized into
colonies similar to those of bees and ants but they are unrelated to these insects (see
Figure 5.17).

Figure 5.18: Termite mound and termite casts

Activity 5.12
I Library Assignment
1 Why is it advisable to leave some of the honey in the colony when harvesting
honey?
2 What is the economic importance of beekeeping, both in terms of pollinating
crops, and obtaining products from the hive?
3 What is the use of the following? Honey, Beeswax, Pollen, and Queen Jelly.
4 What is the advantage of using a modern beehive?
5 Try to appreciate the behavior of social insects and show interest to investigate
the similarity between honey bee and termites.

II Constructing a Model Beehive

Visit a beekeeper and ask how a beehive is prepared, read books in the
library and construct a model beehive in groups, make a drawing of your
beehive and label the parts.

Exercise 5.4
Choose the best answers for each of the following questions
1 From the castes of bees, sterile females which cannot reproduce are called
A Drones C Queen
B Workers D Queen and workers
122 Biology Grade 7
2 A small six sided chamber made from wax by workers bee is called
A Royal jelly C Honey
B Honey comb D Frame
3 Which of the following is not true about useful insects?
A They spread disease
B They kill harmful pests
C They pollinate plants
D Some decrease crop production
4 The insect that causes a huge damage to crops is
A Mosquito C Housefly
B Dark moth D Bee
5 An insect which can build a mound is
A Termite C Mosquito
B Housefly D Locust

Unit Summary

ŒŒ Animals show differences in a number of ways including size, type and

distribution.
ŒŒ Insects are the most diverse group of animals.
ŒŒ The fundamental difference between some insects and other animals is that
as insects grow, their bodies completely change their form. This process is
called metamorphosis. Metamorphosis may be said to be incomplete or
complete.
ŒŒ Complete metamorphosis involves a complete change of form involving four
main stages: egg, larva, pupa and adult.
ŒŒ Incomplete metamorphosis involves a gradual development involving only
three stages: egg, nymph and adult. The nymph closely resembles the adult
except it is smaller in size and wingless.
ŒŒ Some insects are of great economic importance; some are harmful while
others are beneficial.
ŒŒ Tsetse fly is a harmful pest that affects both cattle and people. They are vectors
of disease. The term vector means a carrier of disease. They are commonly
found along the edges of lakes and banks of rivers.
ŒŒ The tsetse fly carries a parasite called trypanosome, which causes a disease
called nagana in cattle and sleeping sickness in people.
ŒŒ Suitable methods of controlling the tsetse fly include removing bushes and
undergrowth along streams to reduce tsetse fly populations, spraying areas
known to harbour the infection with insecticides, and Spraying livestock with
insect repellent.
 Unit 5: Animals 123
ŒŒ Some insects live together in large groups or colonies and share out the work
needed to sustain the colony between them.
ŒŒ Different castes of the insect carry out different duties within the colony. The
ability of social insects to live together in a hive increases the chances of their
survival. Examples of social insects include ants, termites, and honeybees.
ŒŒ Honeybees are a social insect which are beneficial to people. They live in a
hive in which there are three castes, Queen (lays eggs), Drones (mates with
the queen) and Workers (gather nectar, build honeycomb, protect the hive).
ŒŒ It is possible to harvest some of the honey made by bees but leaving the
colony of bees sufficient for its needs.
ŒŒ A beehive should be managed carefully and the honey is harvested with
protective clothing.
ŒŒ The economic importance of beekeeping is great. Bee are pollinators of
crops and produce useful substances. The useful products obtained from
honeybee include honey, beeswax, pollen, and queen jelly.
ŒŒ Bees communicate with each other through various dances, to indicate the
source of food.

? Review Exercise for Unit 5

Ajsjsdf AjsjsdfAjsjsdf
AjsjsdfAjsjsdf Ajsjsdf

AjsjsdfAjsjsdf Ajsjsdf
AjsjsdfAjsjsdf Ajsjsdf

AjsjsdfAjsjsdfAjsjsdf Aj
Ajsjsdf AjsjsdfAjsjsdf

Ajsjsdf AjsjsdfAjsjsdf
AjsjsdfAjsjsdf Ajsjsdf

AjsjsdfAjsjsdf Ajsjsdf
AjsjsdfAjsjsdf Ajsjsdf

..............
..............
..............
Ajsjsdf

Part I: Choose the best answer for each of the following questions.
1 Which one of the following is the largest animal?
A Elephant C Whale
B Mule D Zebra
2 Animals living in water are called
A Aquatic C Terrestrial
B Arboreal D Aerial
3 Which one of the following is not true about insects
A Their body is divided into three main parts
B They are the most diverse animals
C All of them have an abdomen
D All of them have complete metamorphosis life cycle
4 The head of insects support
A Wings C Thorax
B Abdomen D Antenna
5 Each stage between moults of incomplete metamorphosis is called
A Pupa C Larva
B Instar D Caterpillar
124 Biology Grade 7
6 Which of the following shows incomplete metamorphosis
A Butterfly C Grass hopper
B Moth D House fly
7 The larval stage of moths and butterflies is called
A Nymph C Caterpillar
B Pupa D Moult
8 The correct sequence of complete metamorphosis is
A Egg  Pupa  Larva  Adult
B Egg  Larva  Pupa  Adult
C Egg  Larva  Caterpillar  Adult
D Egg  Larva  Instar  Caterpillar
9 Army worm is the larval stage of
A Dark moth C Butterfly
B Locust D Tsetse fly
10 In a modern hive of honey bee, honey is harvested from
A Brood box C Top cover
B The super D The hive stand

Part II: Match items given in Column A to the appropriate description given in
Column B.

Column A Column B
11 Caterpillar A Removal of outer body cover
12 Pupa B Young stages of honeybee
C Female honeybee
13 Moulting
D Male honeybee
14 Brood E Animals having back bone
15 Drone F Animals living on land
16 Invertebrate G Animals living in water
H Animals with no backbone
17 Vertebrate
I The 3rd life stage in butterflies
18 Terrestrial
J The larval stage of butterflies
19 Aquatic K Animals living on tree branches
20 Vector L Disease carrying insects
 Unit 5: Animals 125
Part III: Fill in the blanks with the appropriate terms.
21 The most diverse group of animals are ______ .
22 Complete metamorphosis involves ______ distract stages.
23 The larval stage of the night flying moth is ______ .
24 Social insects live in ______ .
25 Honey bees perform ______ to locate a new food source.

Part IV: Give short answers for each of the following questions.

26 What are social insects?

27 What is the role of the queen in a honeybee colony?
28 What are the advantages of a modern beehive?
29 How can the sting of bee be protected when harvesting honey?

Part V: Copy the crossword puzzle below and use the numbered clues to complete
and solve the puzzle.

1, 2 3

4 5 6

7 8

10
126 Biology Grade 7
The numbers in the bracket indicate the number of letters in each word.

Across

1 Change of body structure in insects (13)

5 Animals living on tree (8)

7 Animal group with back bone (5)

9 Stage between molts in incomplete metamorphosis (6)

10 Animals living in air (6)

Downward

2 Vertebrate group (7)

3 3rd life stage in complete metamorphosis (4)

4 Animal group without back bone (12)

6 2nd life stage in complete metamorphosis (5)

8 1st life stage of all insects (3)

Unit
Environment
6
Unit Outcomes
By the end of this unit, you will be able to:
”” define habitat, classify habitats into
terrestrial and aquatic and give
example for each;
”” define population and community and
give examples for each;
”” identify smaller habitats in your
surroundings, examine organisms
that dwell in them and write a report
on your findings;
”” use quadrats to estimate distribution
of organisms in a given habitat,
demonstrate methods of collecting
and preserving plant and animal
specimens and collect and preserve
plant and animal specimens,
Main Contents
”” describe food chain and food web with 6.1 Habitat
practical examples and construct a
simple food chain by observing food 6.2 Studying a Habitat
relationship of organisms in your 6.3 Food Relationships
surroundings; and
ŒŒ Unit Review
”” explain the different trophic levels of
a food chain; describe the pyramid of
numbers using a diagram and indicate
the trophic levels on the diagram of the
pyramid of numbers.
128 Biology Grade 7
Introduction
Why is it so important to know about our Environment?

We should question about the environmental change

that is happening in our day to day life. Natural Did You Know?
and Man-made contribution and its consequences ¸¸Ethiopia is known for its natural
brought the attention of leaders and other people to resources, however, less than 3% of
the environment. Unexpected climate change, such the forest cover is left, 81 billion M3
as global warming, poor productivity of harvest (74% of 110 billion M3) of water leaves
the country with soil and nutrients; 95%
due to poor care for the soil, air pollution, erosion
(Urban + Rural) and 99.9% (Rural) of
and deforestation are some among many others. energy demand is met from biomass
energy; drought and desertification is
Look around your environment, what are the natural spreading; temperature is rising even
and man-made environmental disasters? What should in high lands; and land productivity is
be done to make the environment more suitable for declining.
living organisms?

Good understanding about environment is the basis to care for the natural system. As a
result of awareness about the environment, people might care and maintain the proper
natural system in a better way. In this unit you are going to explore habitats and their
characteristics. The second subunit focuses on how to study a habitat through various
tools and techniques that help us collect information on the types, distribution and numbers
of living organisms within. The last subunit deals about food relationship among living
organisms and how energy is transferred from one form of living thing to another within
an environment.

6.1 Habitats
By the end of this unit, you will be able to:
”” define habitat as a place where living things live;
”” classify habitats into terrestrial and aquatic;
”” give examples of terrestrial and aquatic habitats;
”” define population as a group of organisms of same species;
”” give example of populations;
”” define community as a group of populations of different species;
and
”” give examples of communities.
 Unit 6: Environment 129
Key Terms
What is a Habitat?
55Environment: everything
A habitat is a place where an organism lives and in the surrounding of an
reproduces in its environment. It is the natural home or organism that could possibly
address, where an organism can be found, such as under influence it.
a stone or at the bottom of the pond. It might be also a 55A habitat: is an ecological
clean stream, river edge or a forest. For example, the or environmental area that
habitat for a tadpole can be a pond, where its environment is occupied by a particular
species of animal, plant or
consists of water, temperature and oxygen that will
other type of organism.
influence the tadpole’s rate of growth and activity. The
55Aquatic habitat: a watery
watery environment contains plants and animals on environment in which living
which the tadpole will feed, but it also contains fish and things dwell.
insects which may eat the tadpole. Thus, the water, the 55Terrestrial habitat: a land
oxygen, the temperature, the food and the predators are environment in which living
all part of the tadpole’s environment (see Figure 6.1). things live.

Figure 6.1: Example of a Habitat

Aquatic and Terrestrial Habitats

Since there are various ways of life observed in living things, there has to be wide range
of habitats suitable for the different types of living things. These habitats are generally
classified into aquatic and terrestrial habitats.

What is an aquatic habitat?

Aquatic Habitat is an environment, which is characterized by living organisms that live

in water. It includes ponds, streams, rivers, seas and oceans. Such habitats are suitable
for harbouring fishes, algae, tadpole, ducks, tortoises and others (see Figure 6.2a and
Figure 6.3a). Can you add some more?
130 Biology Grade 7

What is a terrestrial habitat?

Terrestrial Habitat is an environment, which is characterized by living organisms that live

on land. It includes forests, mountains, hills, rocks and soils. Such habitats are suitable
for birds, insects, worms, trees and wild animals (see Figure 6.2b and Figure 6.3b). Can
you add some more?

a) Lake b) Forest
Figure 6.2: An example of aquatic and terrestrial habitat

a) Whale b) Rhino

Figure 6.3: Animals living in aquatic and on terrestrial habitats

Activity 6.1
Discuss on habitats
Materials you will Require:
Did You Know?
A log, a stone (rock), a tree, a river, or a pond. ¸¸Whale is the biggest animal living in
Procedures: aquatic habitat and an elephant is
55 In groups, look for a habitat in your the biggest mammal that lives on a
school compound and village. terrestrial habitat.
55 Discuss on the habitats you may have
observed and classify them into aquatic
and terrestrial.
 Unit 6: Environment 131
Population and Community
In a given habitat every living organism is adapted or
suited to its environment. Moreover, living organisms Did You Know?
do not exist separately but interact with their living ¸¸Ethiopian human population is estimated
and nonliving environment. For example, fishes live to be 73,918,505 (CSA 2008) and the
only in aquatic habitat because they are adapted to population of one of the endemic wild
animals of Ethiopia, Walia Ibex, is
interact with the aquatic environment.
approximately 745.

What is population?

A group of living organisms of the same species

Key Terms
that lives in a particular area is called a population.
Within any habitat there are a number of organisms 55Population is a group of living
organisms of the same species
of the same species living together as members of a that live in a particular area.
population. For example, there will be a population of 55Community is all the different
each type of algae, fish, bird and insects. On the other population that are found in a
particular area.
hand on land, you can find a population of human
beings, domestic animals such as cats, dogs and so on.

Each population has its own requirements to live within a given habitat such as
temperature, humidity, types of food and other factors that can determine its existence
and reproduction. In addition, places where there are predators, competitors or parasites
may not be suitable and can prevent a population from occupying the area. Therefore,
living organisms interact within the environment as a population.

Population of a certain species can be characterized in a way they are distributed in a given
area. They may be found distributed randomly, uniformly or in a group form. Therefore,
in some populations, individuals can be observed living in groups, in some others they are
dispersed here and there, evenly or unevenly (see Figure 6.4).

Figure 6.4: Population of Walia Ibex

132 Biology Grade 7

What is community?

A community is all the various

living things or populations
living and interacting in a
particular area. A community
is made up of all the plants
and animals living in a
habitat. Within a habitat,
there likely are populations of
different species. A group of
populations that live together
in a given habitat are called a
Figure 6.5: Community of domestic animals
community (see Figure 6.5). and men

Exercise 6.1
I Choose the best answer for each of the following questions
1 Which of the following is the best habitat for a fish
A a lake B a stone C a log D a tree
2 Which of the following is the best habitat for a tape worm?
A a lake C a human intestine
B a forest D a grass
3 A community includes all
A the plant species only C the different species
B the animal species only D all the single species
4 A population consists of
A all different species within a given habitat
B a group of the same species with in a given area
C plants and animals only
D none of the above
II Try to sort out, the following as aquatic and terrestrial habitats from the biggest
container to the smallest ones.

Habitat Aquatic Terrestrial

Ditch, farmland, park, pond, stream,
river, savannah, lake, rock pool,
ocean, rain forest, mountain, field,
desert, sea, ocean.
 Unit 6: Environment 133
6.2 Studying a Habitat
At the end of this section, you will be able to:
Key Terms
”” identify smaller habitats in your
55Sampling: is the technique
surroundings; used to estimate the
”” examine organisms that dwell in population of a species that
the smaller habitats; are found in a given habitat.
”” write a report on the small habitats 55Quadrats: are a series of
and the organisms dwelling in them; square (1 m2) frames that are
”” use quadrats to estimate distribution placed in a habitat used for
sampling.
of organisms in a given habitat;
”” demonstrate methods of collecting
and preserving plant and animal
specimen;
”” collect plant and animal specimens;
and
”” preserve plant and animal specimens.

What is the importance of studying a habitat? How is it possible to

determine or estimate the number of a population within a habitat?

Observing Habitats in Our Surroundings

If you observe your surroundings, you can find habitats in which there are various
populations and communities. It might be possible to count all the trees in your school or
all the insects under a stone, or all the worms in the moist soil sample. However, it would
be difficult or impossible to identify and count all the different kinds of fish in a lake or
all the trees in a forest.

Observing habitats and identifying different species, population or community requires a

systematic approach. Scientific approach uses various tools and techniques. Sampling is
one of the techniques that is commonly used in identifying a population of a species. By
sampling we mean we take a portion or sample of the area to estimate the population of a
species that is found in a given habitat.

The sampling technique enables a biologist to estimate the total number of organisms in
the habitat under study. Since the organisms may not be evenly distributed, it will be good
to take several samples from different parts of the habitat randomly. The samples will also
need to be taken at regular interval throughout the year as there are seasonal fluctuations
in the environment.
134 Biology Grade 7

What are quadrats?

Quadrat is a square or rectangular frame made of metal,
wood or is pegged out with string on the ground. It is shown
in Figure 6.6. It can be made up to an area of 0.25 m2 or
(0.5 m X 0.5 m), you can make quadrats using locally
available materials such as bamboo, or sticks, wire or
strings. Figure 6.6: A quadrat

Quadrats are best suited to sampling vegetation. The quadrats must be placed at random
throughout a habitat so that they are not deliberately placed towards vegetation which
looks interesting, you can use the quadrat land depending on the type of information you
require.

Activity 6.2
Mapping a habitat
In this activity you will examine your surrounding and map it so that you can
better describe it.

Procedures:
55 Make a group and identify a habitat to be visited.
55 Draw a map of the habitat and then look for living organisms and mark
where you find them on the map.
55 Did you find similar types of living organisms in one spot?
55 What are the most common types of living organisms in the area?
55 Does the habitat have enough food, water and shelter for the living
organisms?
55 Write a brief habitat survey report and present it in the class. Your report
should include:
33 the size of the habitat.
33 the nature of the habitat.
33 sizes of the various populations of organisms found and identified.
33 comments on any particular interesting features. For example,
particular plants found only where the ground is damp.

Using Quadrats

How is it possible to determine the population of a certain species within

a habitat?
 Unit 6: Environment 135
Quadrats are samples used to identify and
estimate the number of plant communities in a
given habitat. In using quadrats first map the area
and know the total coverage of the habitat. The
quadrats must be placed randomly throughout
a habitat of interest. The quadrats can be used to
have quantitative information such as density,
frequency and percentage cover of the plant species
(see Figure 6.7). Figure 6.7: Using a quadrat

There are factors that need to be considered in relation to the use of quadrats. These are
55 distribution of various species,
55 shape and size of the quadrat (square, circle or rectangle), and
55 number of observations needed to obtain an adequate estimate of density
(sample size).

To obtain the density of organisms per unit area of habitat

55 first count the number of a plant species present within a quadrat each time it
is placed,
55 repeat counting until the quadrat has reached and placed all the randomly
selected area of the habitat, and
55 finally calculate the average number of this plant species per unit area.

Activity 6.3
Identification and examining of a small habitat
Procedures:
Divide yourself into groups and look for a small habitat in your surrounding
probably on a playing field, a pool or a small wood.
55 Form a quadrat tool using locally made bamboo or stick, the quadrat
should be arranged in the order of a square metre for simplicity.
55 Divide the habitat into locations and select locations randomly by
picking numbers in some random way.
55 Examine and identify the organisms found.
55 Write a brief report on your findings following the format below.
33 The size of the habitat in square meters.
33 The nature of the habitat either aquatic or terrestrial (draw the
picture of the habitat or use camera or mobile phone, if possible).
33 Sizes of the various populations of organisms found and identified.
33 Comment on any particular interesting features, example, particular
plants found only where the ground is damp.
136 Biology Grade 7
33 Estimate the whole population of the habitat.
33 Comment on how reliable the estimates are.
33 Is there any other better way to sample the organisms in a habitat
besides using a quadrat? (as line transects)

Collecting and Preserving Plant and Animal Specimens

Why do we collect and preserve specimens of plants and animals?

Plants and animals are collected to obtain specimens for demonstration and studies. In
fact many plants and animals can be studied where they live and they don’t have to be
collected. Only collect specimens which must be taken back to the school laboratory for
display or study or specimens which cannot be studied at once because they live in places
such as water or under soil. Then, collected specimens can be preserved to keep the dead
sample remain unspoiled and can be used for future learning by displaying in a laboratory
or museum of the school.

How can you collect and preserve animal specimens?

There are various methods of collecting and preserving plant and animal specimens
depending on their nature (size, strength). This can be done using collecting tools such as
pitfall trap, pooter, sweep net, butter fly net and the like. Chemicals such as chloroform,
alcohol, formalin are used to kill and preserve animal specimens.

Note: We should treat all animals with respect. If the animals are simply to be examined
and drawn they should be returned to the wild unharmed as soon as possible. If the animals
are to be retained as specimens, they should be killed in a humane way, using chemicals
such as chloroform, and immediately placed in a preservative solution such as formalin.

Description of Various Tools used in Collecting Animal

Specimens
Pitfall Trap: is a container that is sunk into
the ground so that its rim is flush with the
Insect Pitfall Trap
soil surface. Insects and other arthropods
are captured when they fall into the trap.
To prevent insects from escaping or
preying on each other, pitfall traps usually Ground

contain a killing/preserving agent such as

Alcohol
pet safe anti-freeze, soapy water, or ethyl
alcohol (see Figure 6.8).
Figure 6.8: A Model of Pitfall trap
 Unit 6: Environment 137
Sweep nets: are study nets, often with a
canvas bag that are used to collect insects
and other invertebrates from long grasses
(see Figure 6.9).

Figure 6.9: Sweep net on use to collect insects

Tullgren Funnel: This is to extract Light Bulb

insects from soil. A soil sample is placed
on wire gauze which is over a funnel Soil goes here
which leads into a beaker with a mixture -----------------------
of alcohol and water. There is a strong
Wire mesh
light held over the soil for the necessary barrier
amount of time. The light gradually dries
Vial of alcohol
out the soil, driving the insects within it
to go downward until eventually reaching
the beaker of liquids (see Figure 6.10). Figure 6.10: A model of Tullgren Funnel

Pooter: A small jar with two separate Plastic pipe

tubes leading out. One tube is covered
with wire gauze on the inside of the
beaker. Inhale through this tube while
placing the other end over small insect
to suck the insect into the beaker (see Wire gauze

Figure 6.11). Beaker

Insect

Figure 6.11: A model of pooter, to trap

insect using inhale in to beaker.

How can you collect and preserve plant specimens?

Collecting plant specimens is different from animal specimens both in technique and
procedure because of their nature. Plant specimens are collected and preserved using various
techniques, such as pressing and drying, storing the seeds in a gene bank and others.
Procedures followed in collecting and preserving plant specimens:
1 Collecting various types of plants leaves and flowers: Plant specimens are usually
collected using a plastic bag. In collecting a plant specimen first you have to devise a
method of removing plants whole from the ground, taking care that the root system is
not damaged. Any soil should be washed off and the plant is left in the sun to dry out.
138 Biology Grade 7
2 Pressing and drying: The best specimens are plants that are pressed as soon as
possible after collection, before wilting and shrivelling. Specimens are pressed flat
and dried between sheets of absorbent blotters or semi-absorbent paper such as
newspaper. The plant should be carefully laid out between the drying sheets, as
their form at this stage largely determines their ultimate appearance. The flowers
should be spread out with the petals carefully arranged, wilted leaves should be
straightened and unnecessary shoots of excessively twiggy shrubs may be cut away.
3 Mounting is a process of posting or putting specimens on a card or other materials
to minimize damage and to sustain for long period of time. Well-mounted herbarium
specimens can last for many centuries. We can use various four methods to secure
a specimen to a mounting card:
55 spot glue paper strip with gummed paper.
55 sew with needle and thread, securing knots with linen tape.
55 float specimens on to card (in the case of macroalgae), and others.
4 Labelling: In order to identify the plant specimens and where it was collected,
labelling is important. Plant specimens should be stored in a dry room. Museums,
gene banks and laboratories are the common places to preserve various types of
plants and animal species for visit and study (see Figure 6.12).

Name of Specimen _________

Place of collection _________
Name of collecter _________
Date of collection _________

Figure 6.12: Preserved plant specimen

Activity 6.4
Collection and preservation of animal and plant specimens
Procedures:
55 In your group, discuss the various techniques that could be used to
collect animals and insects within a habitat.
1 Collect and preserve some animals and plants from your village using the
above mentioned techniques.
2 Display them in your class.
 Unit 6: Environment 139
Exercise 6.2
Choose the best answers for the following questions
1 Quadrat is more suitable for sampling of
A animals C microorganisms
B plants D all of the above
2 During studying habitats,
A quadrats are placed randomly C mapping is needed
B quadrats are placed all over the D A and C
place
3 Which of the following is used to preserve animal specimens for laboratory study?
A formalin C salt
B water D gasoline
4 Preservation of plant specimen involves
A drying C labelling
B mounting D all of the above
5 Sweep net is used to trap
A spider C monkey
B butterflies D ants

6.3 Food Relationships

By the end of this section, you will be able to: Key Terms
”” describe food chain with a 55A food chain is a single path as
practical example; organisms of a single habitat eat
”” construct a simple food chain by each other.
observing food relationship of 55Food webs show how plants
and animals are interconnected
organisms in your surrounding;
by different paths.
”” describe food web with a practical
example;
”” explain the different trophic
levels of a food chain;
”” describe the pyramid of numbers
using a diagram;
”” describe the pyramid of energy
using a diagram;
”” indicate the trophic levels on
the diagram of the pyramid of
numbers.
140 Biology Grade 7
Food Chain and Food Web
Living organisms in a habitat interact with each other for food, space and other resources.
From your Unit 4 lesson, you remember that green plants are able to convert sunlight energy
into chemical energy. This chemical energy in the form of food is transferred through the
various organisms. The transfer of energy contained in food can be well explained in terms of
food chain and food web.

Food Chain

What is a food chain?

A food chain is a simplified food relationship showing

Key Terms
food transfer from green plants to the different
organisms. It is a single path of food transfer. A food 55Consumers: can be classified
chain always begins with a producer, or an organism into three groups depending
that makes its own food through photosynthesis, and on the way they feed.
consists of organisms that feed on the other. For 55Herbivores: are animals that
feed on plants or primary
example, green plants (producers) produce food by
consumers.
photosynthesis. The grass (produce) is eaten by a 55Carnivores: are animals
grasshopper (consumer), the grasshopper is eaten by that feed on herbivores or
a frog, the frog is eaten by a snake, and the snake is secondary consumers.
eaten by a hawk (bird). A plant or an animal can be in 55Omnivores: are animals
more than one food chain. that feed on both plants and
animals.
Food chains are not always limited to three consumers;
they may contain more than three consumers.
Example:
Grass (Autotrophs/Producer) → Grasshopper (Primary Consumer) →
Frog (Secondary Consumer) → Snake (Tertiary Consumer)
Green plants, which are the producers, have a critical position in the thread of life because
they form the energy linkage between the sun and non-photosynthetic organisms.

Food Web

What is food web?

In nature, organisms in a habitat are involved in more than one food chain, therefore, in
actual situation, natural food chains are interlocked to form a food web. A food web is
a complex feeding relationship showing actual food transfer in nature from producers
to consumers. A food web may begin with grass (producers), which would be eaten
by insects, mice or rabbits, which would be eaten by different predators. More species
are included in a food web, which uses a series of arrows to describe relationships
(see Figure 6.13).
 Unit 6: Environment 141
Activity 6.5
Identification of examples of food chain
Procedures:
55 Be in groups of four and consider the above example or your surrounding.
55 Give similar examples of food chains that show two level consumers
(secondary consumers) and three level consumers (tertiary consumers).
55 Share your examples in your class.
55 What are the general patterns of relationship in a food chain?

King fisher

Small fish Frog

Hawk

Snake

Tadopole Water beetle Snail

Rabbit
Mouse

Wildflowers Grass Algae

a) Terrestrial b) Aquatic
Figure 6.13: Food web in terrestrial and aquatic habitats

In general, food chain and food web are means of describing feeding relationship within
the environment. In both cases, the feeding relationship starts from a producer, green
plants which make their food by the process of photosynthesis.

The sun is the source of energy for living organisms. Those that make their own food are
known as producers and those that feed on either plants or animals are called consumers.

Can you give examples for each type of consumers?

Activity 6.6
Identification of food chain and food web
Be in groups of four and look at the following living organisms in a habitat:
(trees, sun flower, dog, elephants, monkey, rat, cat, sheep, donkey, algae, cow, mice,
frog, grasshopper, hawk, fish, lion, tigers, grass, fruits, hyena, earthworm, birds,
beetles, snake, butterfly….)
142 Biology Grade 7
1 Then sort them out into the following groups or categories.
A Producers ______. C Secondary consumers ______.
B Primary consumers ______. D Tertiary consumers ______.
2 Draw second level food chain.
3 Draw third level food chain.
4 Construct a food web using these organisms.

Trophic Levels

What are trophic levels?

Trophic level is the feeding level of an organism in
Key Terms
a food chain. Each stage of a food chain is called a
trophic level. The producers occupy the lowest (first) 55Trophic Level: is each level in a
food chain. Matter is always ‘lost’
trophic level of any ecosystem. At the second trophic as heat energy at each trophic
level are herbivores. They are primary consumers. level.
The third trophic level constitutes animals that eat
herbivores, called carnivores, and are secondary
consumers. Some food chains may contain a four trophic level composed of carnivores
and are called tertiary consumers or top carnivores.
Trophic level: As we go from the lower to the upper trophic level, the amount of initial
energy decreases. This is because of the loss of much energy by consumers for their daily
activity. As a result more energy is available at the lower trophic level than the upper.

All the trophic levels occupied FOOD WEBS

by the consumers use small Secondary Tertiary
proportion of the energy to build carnivores consumers
their body. In consumers most
of the energy in foods is lost for
different activities such as body
heat regulation, movement of carnivoresPrimary Secondary
consumers
body and to expel their waste. The
amount of energy flowing through
the food chain usually drops Herbivores Primary
consumers
with each step up the chain, thus
giving the characteristic ‘pyramid’
shape. This is why a trophic level Producers
is represented as a pyramid. The Arrows point to the animal doing the eating (predator)
base of the trophic level represents
Figure 6.14: Diagram of a Trophic level
the producer trophic level and the
apex (tip) is the highest level of
consumers called the top predators
(see Figure 6.14).
 Unit 6: Environment 143
The initial energy that comes from the sun flows through the producers and converted
into chemical energy. The producers use some of the chemical energy for their own life
processes and pass only a portion of the trapped chemical energy to the consumers.

Activity 6.7
Based on Figure 6.14 discuss on the number of organisms in trophic
levels
55 In groups, observe the number of organisms from bottom to top of each
trophic level.
55 Discuss what happens to the number of the organisms as you go up or
down the pyramid. What is the reason?

Biological Pyramids
Ecologists classify the relationship among living organisms in pyramid model. Basically
there are three types of ecological pyramids. These are pyramid of number, pyramid of
biomass and pyramid of energy.

Pyramid of Numbers

What is a pyramid of numbers?

As the name suggests, pyramid of numbers represents the number of individuals at each
trophic level. A graphical representation in the form of a pyramid showing the feeding
relationship and the number of organisms at each trophic level is known as pyramid of
numbers.

The number of individuals generally decreases

passing along a food chain. We can show the
relative number of organisms at each trophic level
as a pyramid of numbers. Accordingly, if the upper
trophic level contains more numbers of individuals
than the lower, there will not be enough food for the
upper. As a result both organisms perish. However,
this is not always the case, in some food chain the
lower trophic level may contain individuals than
the upper and the pyramid becomes inverted. This
happens in parasitic food relationship because on Figure 6.15: Pyramid of numbers
a host we can find large number of parasites (see
Figure 6.15).
144 Biology Grade 7
Pyramid of Energy
Tertiary
Shows the amount of energy Consumers
predators

lost and transferred in each

trophic level. It describes
9 kilocalories per
that less energy is found Square meter peryear
in each next trophic level Secondary Consumers
predators
because of a small portion
of the food becomes part of
90 kilocalories persquare meter peryear
the organisms’ body. Much available in bodies of secondary Consumers

of the rest of the food is used

Primary Consumers
Herbivores

for various activities of the

organism (see Figure 6.16). 900 kilocalories persquaremeter peryear
The pyramid of energy gives available in the bodies of primary Consumers

the clearest general picture

of the relation ships within a
particular community. Primary producers: Trees, Shrubs,ferns, grasses, flowers
9000 kilocalories persquare metere peryear available for primary consumers
Figure 6.16: Pyramid of Energy
Pyramid of Biomass
A measure of the total mass of dry organic matter produced in a given community. The
pyramid of biomass is more useful than the pyramid of numbers because it indicates the
quantity of living things present in each trophic level.

Activity 6.8
Discussion on the shape of pyramid of numbers
In Groups:
1 discuss how the shape of a pyramid of numbers may be different for different
food webs. For example, a single large tree may provide food for a large
number of caterpillars. So, in this case, the base of the pyramid of numbers
would be very small.
2 explain how an inverted pyramid of numbers might arise. For example, a
single rose bush may support many aphids, and each aphid may support a
large number of bacteria.

Exercise 6.3
Choose the best answers for the following questions
1 Food Chain is
A a simple type of feeding relationship only among animals
B a simple type of feeding relationship among living organisms
 Unit 6: Environment 145
C not always limited to three consumer levels
D A and C
2 Which one of the following is true about food web and food chain?
A Plants are not involved in case of food web
B Food web is more complex type of food relationship
C Both are limited to explain similar types of organisms
D None of the above
3 Plants
A are producers of food for consumers
B are the first to convert light energy into chemical energy
C form the base of the pyramid of number
D all of the above
4 One of the following consumers is characterized by eating only meat
A herbivores C omnivores
B carnivores D producers
5 One of the following describes correctly about pyramid of energy
A it is the number of consumers at each level
B it is the amount of energy lost and transferred at each trophic level
C energy flow increases as we go up to the pyramid
D none of the above

Unit Summary
ŒŒ In this unit we have discussed the following main points
ŒŒ A habitat: is an ecological or environmental area that is occupied by a
particular species of animal, plant or other type of organism.
ŒŒ Population: A group of living organisms of the same species within a habitat.
ŒŒ Community: A group of populations within a habitat.
ŒŒ Sampling is a technique used to estimate the population of a species that
are found in a given habitat. Quadrats are a series of square (1 m2) frames
that are placed in a habitat used for sampling.
ŒŒ There are various ways of methods of collecting and preserving plant and
animal specimens depending on their nature (size, strength). This can be
done using collecting tools such as pitfall trap, pooter, sweep net, butterfly
net and the like. Chemicals such as chloroform, alcohol, and formalin are
used to kill and preserve animal specimens.
ŒŒ Food relationship among living organisms is classified into two categories.
These are food chain and food web. A food chain is a single path as organisms
of a single habitat eat each other. Food webs show how plants and animals
are interconnected by different paths.
146 Biology Grade 7
ŒŒ Trophic level: These are defined as steps of food chains which are differentiated
on the basis of their method to obtain the food.
ŒŒ A graphical representation in the form of a pyramid showing the feeding
relationship and the number of organisms at each trophic level is known as
pyramid of numbers.
ŒŒ Pyramid of energy shows the amount of energy lost and transferred in each
trophic level.

? R
Ajsjsdf AjsjsdfAjsjsdf
AjsjsdfAjsjsdf Ajsjsdf

AjsjsdfAjsjsdf Ajsjsdf
AjsjsdfAjsjsdf Ajsjsdf

Exercise for Unit 6

AjsjsdfAjsjsdfAjsjsdf Aj
Ajsjsdf AjsjsdfAjsjsdf

Ajsjsdf AjsjsdfAjsjsdf
AjsjsdfAjsjsdf Ajsjsdf

eview
AjsjsdfAjsjsdf Ajsjsdf
AjsjsdfAjsjsdf Ajsjsdf

..............
..............
..............
Ajsjsdf

Part I: Choose the best answers for the following questions.

1 Populations of different organisms living together in an area is called:
A habitat D species
B community E all
C ecosystem
2 Terrestrial habitats are:
A fresh-water D land
B ponds and streams E sea
C lakes
3 The amount of earth covered with water is:
A 1/2 D 1/4
B 2/4 E 4/4
C 3/4
4 Which of the following comes first?
A Mounting the plant D Drying the plant
B Pressing the plant E All are done at once
C Collecting the plant
5 The origin of energy for all living organisms is
A water D sun-light
B chlorophyll E oxygen
C plants
6 Which one of the following feeds on primary consumers?
A Producer D Primary consumers
B Tertiary consumer E All of the above
C Secondary consumers
7 At the base of any ecological pyramid will be:
A decomposers D herbivores
B consumers E all of the above
C producers
 Unit 6: Environment 147
8 The transfer of food energy from the source in plants through a series of organisms
with repeated stages of eating and being eaten is known as:
A food-chain D energy flow
B food web E all of the above
C succession
9 Which of the following is not the same to the others?
A Herbivores D Cow
B First order consumers E None
C Second order consumers
10 Fungi, moss and ferns grow on a dead decaying log. The log is
A producer D population
B consumer E all of the above
C habitat
Part II: Match items given in column ‘B’ with items given in column ‘A’.

Column A Column B
11 Pit fall traps A surrounding
of an organism
12 Food web B natural
home for living organisms
13 Food chain C water dwellers
14 Quadrat D land dwellers
15 Community E a group of organisms of the same species in a given area
16 Population F a group of different species in a given area
17 Terrestrial G sampling technique
18 Aquatic H simple food relationship
19 Habitat I complex food relationship
20 Environment J a tool to collect insects for study and preservation purpose

Part III: Fill in the blank spaces with correct answers.

21 A food chain begins with _______ .
22 Dead animals can be preserved using chemicals such as _______ and _______ .
23 As one goes from the lower tropic level to the upper the initial energy _______ in
amount.

Part IV: Give short answers.

24 Distinguish the difference between aquatic and terrestrial habitat.
25 What is the difference between environment and habitat?
26 What is the difference between population and community?
27 How do you determine the population within a habitat?
28 What is the difference between food web and food chain?
148 Biology Grade 7
Part V: Word Puzzle. Copy the crossword puzzle below into your exercise book and
solve the numbered clues to complete.
1 2

3
4 5
6

The numbers in brackets indicate the numbers of letters in each word to be inserted in a
box

Across
1 A watery environment in which living things live. (4)
3 A series of square frames for habitat study. (7)
5 All animals that depend on producers (green plants). (9)
6 The techniques used to estimate the population of a species in a given
habitat. (8)

Downward
2 All the different population that are found in a particular area. (9)
4 A habitat that covers (3/4)th of the earth surface. (5)