Definition of Science and Biology

Science is defined as a systematic process of making enquiry about the living and non-living things in our environment. Human beings have always been so curious to know more about the existence of things around them especially those which have to do with the ones that have life, hence the study of biology.


Biology: The term biology is coined from two Greek words – bios meaning life and logos meaning to study. Hence biology can simply be defined as the study of life. In other words, it is defined as the study of plants and animals.



Biology is basically grouped into two main branches. These are:

  1. Zoology: Zoology is the study of animals.
  2. Botany: Botany involves the study of plants. Other branches include:
  • Ecology: Ecology involves the study of plants and animals (living things) in relation to their environment.
  • Morphology: Morphology involves the study of external features of plants and animals.
  • Anatomy: This is another branch of biology which involves the study of internal structures of plants and animals.
  • Genetics: This is the scientific study of heredity and variation in living things.
  • Physiology: Physiology involves the study of how plants and animals function.



The processes or methods of science involves the sequence of making enquiries about an object or thing under study in science. Students of science have to learn to make clear, systematic and accurate accounts of their scientific investigations.

Scientific methods of therefore take the following procedures:

  • Observation.
  • Classification.
  • Inference.
  • Measurement.
  • Identification.
  • Hypothesis.
  • Experiment.
  • Control or conclusion.
  • Theory or Law.

The starting point of scientific method is observation which involves the use of the senses to describe what one has seen or felt about an object. The observation then leads to the classification, then to inference and later to measurement and identification of the existing problems. After that, the scientist now forms hypothesis or a tentative answer. The hypothesis is now tested by an experiment. In reporting an experiment, it is very important to use or follow the patterns laid down by scientists. These patterns include:

  • Aim: This is to state the purpose of the experiment.
  • Apparatus: This stands for the materials that will be used in the experiment.
  • Method: This is to describe in detail, the procedures that are required or the step-by-step set-up of the experiment.
  • Observation: This records what one has seen during and after the experiment has been set up.
  • Conclusion: This is to draw conclusions on the outcome of the whole experiment based on the final result and observations.

Note: In performing an experiment, a scientist or science student needs to take note of control experiment. In control experiment, the scientist makes sure that during the experiment, the organism or object being observed is not deprived of the particular factor being investigated.

The end of the experiment can then be used to show whether the hypothesis is true or false. If the subsequent experiments show that the hypothesis is false, the whole idea or concept of the matter under investigation is then repeated or at worst discarded. But when the hypothesis has been tested and found to be repeatedly correct within the limits of available evidence, the concept becomes a theory. If a theory has been extensively tested and proven to be true, it becomes a law.



Science has been put into many good uses for the benefit of man. The usefulness of science finds application in:

  1. Medicine: Science has contributed greatly to the manufacture of vaccines and drugs that are used today to cure various diseases of man.
  2. Manufacturing industries: Various raw materials have been combined to manufacture many finished products commonly used by man.
  3. Construction: Roads, railways, airports, etc have been designed and constructed as a result of the knowledge derived from science.
  4. Engineering: Ship building, skyscrapers, bridges, roads, etc have been designed and constructed due to the knowledge acquired from science.
  5. Agriculture: New breeds of animals and varieties of crops including fertilizers have been developed and these have helped to increase food production.
  6. Technology: Science has helped in the development of computers that have enhanced the efficiency of mankind in their activities.
  7. Communication: Televisions, telephone, telex, fax machines, etc have been developed with the aid of science which now makes communication among countries to be possible.
  8. Transportation: Aeroplanes, ships, rockets, etc have been built due to the knowledge of science and these have made movement of people and goods within and across nations possible.



Everything on earth can be classified as either living or non-living things. Living things include plants and animals that have life, while non-living things include those things that do not have life. Examples of living things include man, rabbit, hibiscus, elephant, monkey, grass, mango tree, sheep, dog, etc, while non-living things include air, stone, water, table, house, book, pen, etc.



Living things are distinguished from nonliving things by a number of characteristics which include:

1) Movement: Movement is defined as the ability of an organism to move its own whole body or part of its body from one place to another. Living things move in order to look for food, for reproduction and to run away from danger or respond to the environment. Generally, most animals can move themselves from one place to another; while plants can only move parts of their bodies in response to external stimuli.


2) Nutrition: Nutrition is defined as the ability of living organisms to feed. The reason for feeding is to enable living things live and carry out life processes like growth, respiration and reproduction. While all green plants can manufacture their own food through the process of photosynthesis (i.e. autotrophic or holophytic nutrition), all animals cannot manufacture their own food but depend on plants directly or indirectly for their food; hence this type of nutrition is called heterotrophic or holozoic nutrition.


3) Respiration: Respiration is defined as the exchange of gases between organisms and their environment. Living organisms take in oxygen and breathe out carbon dioxide. The purpose of respiration is to burn down or oxidise food substances in order to release energy which is used for all life processes.


4) Excretion: Excretion is defined as the removal of metabolic waste products from the body. The purpose of excretion is to remove waste products of metabolism, e.g. water and carbon dioxide, which are poisonous or toxic to the body. The process of getting rid of these poisonous metabolic waste products from the body is called excretion.


5) Irritability or sensitivity: Irritability is defined as the ability of organisms to respond to stimuli. Living things exhibit sensitivity in order to enable them survive in their environment. Stimuli include heat, light, pain, water, sound and chemical substances to which living things respond.


6) Growth: Growth is defined as an irreversible or permanent increase in size, dry mass or weight of an organism due to the addition of living protoplasmic materials. The purpose of growth is to enable organisms to repair or replace damaged or old tissues in their bodies. The food eaten provides the basis for growth of organisms.


7) Reproduction: Reproduction is defined as the ability of a living organism to give birth to young ones or offspring. The purpose of reproduction is to ensure continuity of life, i.e ., it enables life to be passed on from one generation to the next.

Reproduction occurs in two forms:

  • Asexual reproduction: This involves only one organism to produce another offspring.
  • Sexual reproduction: This involves two organisms coming together for the purpose of reproduction.


8) Adaptation: Adaptation is the way living organisms get used to their various environments in such a manner that they would be comfortable. This is done in order to survive.


(9) Life span/death: All living things must die because they have a definite and limited period of existence. All

living things must pass through these five stages of life namely:

Birth-> Growth-Maturity->Decline (old age)  ->  Death.


(10) Competition: This is the ability of living things to struggle for all the necessities of life in order to survive in their various environments. Living things compete for food, light, space, water, mates, etc, in order to survive and be in continuous existence.

In summary, all living things carry out all the above characteristic processes, while non-living things cannot.



Plants and animals are living things, but there still exist differences between them. The differences between plants and animals are summarised in this table.



  1. Most green plants carry out photosynthesis (autotrophic nutrition) but non-green plants cannot, i.e ., they are heterotrophic.
  2. Growth is mainly restricted to growing regions or apical meristem.
  3. Continuous throughout life (growing regions).
  4. Indefinite number of parts.
  5. Plants are not active and have no organs of movement.
  6. Plants have slow response to external stimuli.
  7. They possess no special excretory systems.
  8. They possess no special sense organs.
  9. Food is stored mainly as starch except in fungi.
  10. They have no fixed number of parts and branching is continuous.
  11. Gaseous exchange is through the entire body.
  12. Cell has rigid, non-living cellulose cell wall.
  13. Plant cells have large vacuoles containing cell sap.



  1. Animals cannot carry out photosynthesis but depend on plants for their food, i.e ., they are heterotrophic.
  2. It takes place in all parts of the body or intercalary.
  3. Limited to certain periods in life.
  4. Definite number of parts.
  5. Animals are active and have organs of movement.
  6. Animals have fast response to external stimuli.
  7. Animals possess well-developed excretory systems.
  8. They possess specialised sense organs.
  9. Food is stored mainly as glycogen and fat, which is in form of glycogen.
  10. Animals have fixed number of parts which are usually compact.
  11. Gaseous exchange is through special organs.
  12. Cell has thin, flexible living cell membrane.
  13. Animal cells do not contain large vacuoles.

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