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Introduction
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1.1 Definition of Biology and its branches
The word ‘biology’ comes from two Greek words:“Bio” – which means ‘life’ and “Logos” – which means ‘study of’. Therefore, Biology is the science that deals with the study of life and living things. Living things are also known as organisms.
Branches of biology
Like a tree, biology is divided into many branches. Can you name some of them?
Activity 1.2: Playing a game of naming branches of Biology
In pairs
• Write names of the various branches of Biology in manila paper then cut them out.
What to do:
1. Hold up one name of branches of Biology.
2. Let your partner say what the branch is about.
3. Share your work with other members of the class.
4. Repeat this until you finish all the branches of Biology.
The two main branches of Biology are:
• Zoology - the study of animals.
• Botany - the study of plants.
Other common branches of Biology include:
a) Genetics- the study of genes and inheritance.
b) Ecology - the study of the interaction of organisms with each other and with their environment.
c) Anatomy - the study of organisms and their structure.
d) Microbiology - the study of micro-organisms.
e) Physiology - the study of how cells function.
f) Biochemistry – the study of the chemical processes that take place in the body of a living thing.
Assuming each of the leaves in the tree above is a branch of biology; draw it in your notebook and fill the gaps.
1.2 Importance of studying Biology
Activity 1.3: What role does Biology play in our lives? Let us find out.
Discussion corner In pairs
1. What do you think would happen if:
(a) We did not understand how our bodies work?
(b) Doctors were not there?
(c) Research on new drugs and vaccines was not carried out?
(d) We did not understand how various organisms interact with one another and with the surrounding environment?
(e) Scavengers, bacteria and fungi did not feed on dead animals and plants.
(f) Yeast was not used in bread and during fermentation.
(g) We did not have plants to carry out photosynthesis.
(h) We did not have domesticated animals and wild animals.
2. List down in your notebook some jobs or professions that require knowledge of Biology. Refer to the chart provided by your teacher.
The following are some reasons why the study of Biology is important in our society today.
1. Biology helps us to understand our bodies. We are able to know how our bodies work and how they are affected by what we eat, the air we breathe, and our surrounding environment .This can help prevent, cure and even eliminate diseases.
2. The study of Biology helps us in treating and preventing diseases. Here, research is done to invent new drugs and to even come up with better vaccines.
3. The study of Biology helps nutritionists come up with appropriate diets for our various body needs.
4. Biology helps us to understand the science of exercise. The knowledge of anatomy enables athletes to understand how the body functions. This helps athletes to create methods of training that enable them to become more proficient.
5. Biology helps us to understand our environment. Through Biology, we are able to appreciate the wide range of organisms around us. These organisms affect us and we affect them as well. This knowledge helps us to realize the need to conserve the environment.
6. As a subject, Biology guides us on the best farming practices and thereby ensuring food security. Through biotechnology, we are able to develop high yielding crops and animals. Disease and drought
resistant plants and animals are also developed.
7. Biology is a career subject. Some careers linked to Biology include medicine, pharmacy and veterinary among others. With these careers, we are able to earn a living and take care of our families.
Another activity
1.study the following chart carefully.
2. Come up with a table on the applications of biology based on the chart.
3. Compare your work with the other class members.
1.3 Characteristics of living things
What would you look out for if you wanted to distinguish between things that are living and things that are not living?
Activity 1.4
In groups
1. Go to the field for a nature walk.
2. Collect a few things from the environment. Such things may include stones, pieces of wood,
insects such as grasshoppers, butterflies, ants, termites and branches of plants, leaves or roots.
3. Bring the things you have collected to class.
4. Observe them in detail using a hand lens noting the presence of:
a) Breathing structures.
b) Movement structures such as legs, wings, among others.
c) Feeding structures, such as mouth parts among others.
5. Discuss with your partner, how the animals use the above structures for.
6. How about the things that do not have these structures? How do they survive? Are they living?
For an organism to be described as living, it must be able to carry out some processes, which are essential for life. The processes constitute the 6 characteristics of living things. They include:
1. Movement - this is the ability of organisms to change position of the whole body (like in animals) or even parts of the body (like in plants) where leaves or branches that move.
2. Reproduction - this is the ability of organisms to make new individuals of their kind. It can be through sexual or asexual means.
3. Growth - this is the irreversible increase in size and dry mass of a living organism. Growth can occur in three forms: cells of the organism can become bigger, they can increase their number or both.
4. Sensitivity (or Irritability) - this is the ability of an organism to detect or sense changes in its surrounding environment and then respond to them. These changes are known as stimuli (singular – stimulus). For example, plants respond to sunlight by growing its leaves towards it. Animals respond to touch, sound and chemicals among others.
5. Respiration - this is the process whereby an organism produces energy by breaking down food substances. Oxygen is taken in alongside the food while carbon dioxide, water and energy get released. This process is preceded by gaseous exchange which is the process by which living things take in oxygen and release carbon dioxide.
6. Excretion - this is the process whereby organisms remove toxic waste products from the body. The toxic wastes come from m e t a b o l i s m ( t h e c h e m i c a l reactions occurring inside the body). Plants use old leaves, fruits and flowers to get rid of wastes while animals use the excretory system.
The four main excretory organs are the skin, kidneys, lungs and liver.
7. Nutrition (Feeding) - this involves taking food into the body to provide energy as well as bring about growth and repair of worn out tissues. In green plants, photosynthesis occurs to produce food while animals eat plants, other animals or both in order to survive.
Things that possess these characteristics are living things. Things that do not possess these characteristics are non- living things. Plants and animals are living things. Objects like stones, desks, pens and pieces of wood among others are non-living things.
Work to do
1. Read the above points then come up with summarized notes on characteristics of living things.
2. Create a table on the differences between living and non-living things.
Self Test 1.1
1. Justify why a motor vehicle moves but it is not considered a living thing.
2. Plants and animals are both living things. Show how they differ in terms of:
i) Growth
ii) Movement
iii) Nutrition
3. Which characteristics are not exclusive to living organisms only?
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