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BIOLOGY REVISION NOTES
These notes will cover four topics:
Chapter 1: Introduction to Biology
Chapter 2: Classification 1
Chapter 3: The Cell
Chapter 4: Cell Physiology
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INTRODUCTION TO BIOLOGY
Biology is a branch of science that deals with the study of living things. There are
diverse forms of life on earth ranging from the invisible microscopic living things to
the gigantic life forms. It aims at explaining the living world in terms of scientific
principles.
It is important to note, however, that living things interact with the non-living things
in the environment as Well. Biology, therefore also entails the study of non -living
things as well.
The role of human beings in shaping the environment is also investigated in biology.
In summary, biology deals with the study of origins, types, nature, growth,
development, interactions and maintenance of all life forms on earth.
Branches of Biology
Biology is such a broad field of knowledge. It is divided into two broad branches
1. Zoology- This is a branch of biology that deals with the study of animal life.
2. Botany- This is a branch of biology that deals with the study of plant life.
Within the two branches, there exist even smaller branches because the branches
(botany and Zoology) are very wide and complex.
The smaller branches of biology include:
a) Ecology- This is the study of the interrelationships between organisms and their
environment. Ecology aims at establishing how organisms are related to each other
and their environment.
Ecology is further subdivided into smaller branches. These can be forest ecology,
marine ecology, rangeland ecology etc.
b) Genetics- This sub-branch of biology deals with the study of inheritance and
variation. It deals with the study of how variations (differences) occur between
parents and their offspring. It is also concerned with how various characteristics are
passed on from parents to offspring.
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c) Entomology- This is the study of insects.
d) Parasitology- This is the study of parasites.
e) Physiology- This deal with the study of the functions of various structures of an
organism. It deals with the processes that take place in the body of organisms.
f) Anatomy- The study of the internal structure of organisms
g) Microbiology- This is the study of microorganisms
h) Bacteriology- The study of bacteria
i) Ornithology- This is the study of birds
j) Ichthyology-This is the study of fishes
This list is in-exhaustive as there are very many other branches of biology.
Importance of biology
The study of biology is very important. The knowledge acquired from this study
can benefit an individual in myriad ways. The study of biology is important in that:
The knowledge acquired from the study of biology can be very helpful in solving
environmental problems such as food shortage, poor health services, pollution and
environmental degradation.
The study of biology can grant one an entry into various careers such as medicine,
veterinary medicine, animal husbandry, horticulture and dentistry.
The study of biology leads to development of scientific skills which are very useful
in life. These include skills of observing, identifying, recording, classifying,
measuring, analyzing and evaluating. These skills can enable one learn how to make
right choices and lead an improved life.
Through the study of biology man learns the causes of human, plant and human
diseases and how best these diseases can be prevented and cured.
Biological knowledge acquired in the study of biology is very useful in enhancing
international cooperation. Some biology related international conventions include:
> Joint development of HIV/AIDS vaccine by Kenyan and British scientists.
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> The coordinated fight against Severe Acute Respiratory Syndrome involving
scientist all over the world.
> The fight to save the ozone layer from depletion through various international
agreements such as the Kyoto protocol.
> Management of resources through international treaties such as the CITES
(Convention against International Trade on Endangered Species).
Characteristics Of Living Things
Living things share a lot of characteristics in common. These characteristics are
discussed below.
a) Nutrition
Nutrition is the process by which living things obtain and assimilate (utilize)
nutrients. Living things require nutrients for various purposes; growth, repair of
worn-out tissues and for provision of energy. Plants manufacture their own food using
light energy, carbon (IV) oxide, water and mineral salts through the process of
photosynthesis. Conversely, animals feed on already manufactured foods from plants
and other animals.
b) Respiration
Respiration is the process by which food substances are chemically broken down to
release energy. During respiration, oxygen is used while energy, carbon (IV) oxide
and water are released. Respiration occurs in all living cells.
The energy produced in living things is very useful as it enables the living things
carry out some of their physiological processes.
The energy is also required for growth and development, movement and repair of
worn-out tissues.
c) Gaseous Exchange
Gaseous exchange refers to the process by which living things exchange oxygen and
carbon (IV) oxide across the respiratory surfaces. Animals always take in air rich in
oxygen and give out air rich in carbon (IV) oxide.
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Carbon (IV) oxide is a waste product of chemical reactions in the body. Animals
require oxygen for respiration. Gaseous exchange, therefore, enables animals obtain
oxygen for respiration and get rid of carbon (IV) oxide, a waste product.
Plants, however, require carbon (IV) oxide for photosynthesis during the day. They
give away oxygen as a by-product. The plants equally require oxygen for respiration
and give away carbon (IV) oxide.
d) Excretion
This is the process by which living things separate and eliminate the waste or harmful
materials resulting from chemical reactions Within the cells. These harmful waste
products of metabolism maybe toxic to the body if they are left to accumulate in the
cells of the living things
e) Growth and Development
Growth refers to an irreversible increase in size and mass while development refers
to the irreversible change in complexity of the structure of living things. Growth and
development of living things is essential as it enables the living things to attain
maximum size that can enable them to perform their functions and roles.
f) Reproduction
This is the process by which living things give rise to new individuals of the same
kind. All living things reproduce. Reproduction is essential as it leads to perpetuation
of species and it avoids extinction of certain animals and plants.
g) Irritability
This is the ability of living things to perceive (detect) changes in their environment
and respond to them appropriately. Living things respond to changes in temperature,
humidity, light, presence or absence of certain chemicals.
Response of organisms to these changes is crucial as it enables them to escape from
harmful stimuli. Ability to detect changes in the environment also enables organisms
to obtain resources in their environment.
h) Movement
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Movement refers to change is position (displacement) of a part or parts of an
organism. Movement in plants includes folding of leaves, closing of owers and
growing of shoots towards light. The change of position of an entire organism from
one position to another is locomotion.
Study questions
a) Motor vehicles move, use energy and produce carbon dioxide and water. Similar
characteristics occur in living organisms yet motor vehicles are not classified as
living. List the other characteristics of living things that do NOT occur in motor
vehicles.
b) Give the name to the study of:
The cell
Microorganisms
The study of differences between parents and their offspring
The study of relationships between organisms and their environment.
Collection of Specimen
We have defined biology as the study of living things. For effective study, a biologist
may have to collect some living things or some parts of living things for observation
and analysis. The living things or parts of living things that are used for biological
study are called specimens.
Biological studies always take place in laboratories. A laboratory is a building or a
room that is designed and equipped for scientific studies.
Collections of living things especially animals may not be very easy. Some of the
animals are not easy to catch while some are quite dangerous. Knowledge on proper
specimen collection and handling of is very important. We will discuss some of the
apparatus used in specimen collection.
a) Sweep net- This is used for catching ying insects.
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