Form 1:
Introduction to Biology

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Characteristics of living organisms

Living things share a lot of characteristics in common. These characteristics are discussed below:

1. 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.

2. 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.

3.Gaseous Exchange

Gaseous exchange refers to the process by which living things exchange oxygen and carbon (IV) oxide across the respiratory surfaces.

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.


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 may be toxic to the body if they are left to accumulate in the cells of the living things.

5.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.


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.

7. 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.

Movement refers to change is position (displacement) of a part or parts of an organism. Movement in plants includes folding of leaves, closing of flowers and growing of shoots towards light. The change of position of an entire organism from one position to another is locomotion.

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