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Living organisms and their Life Processes!
You have learnt that living organisms have tissues, which comprise groups of cells with similar structures and functions. A cell is the basic structural and functional unit of any living thing.
Each cell is made up of molecules. The molecules exhibit movement during cellular reactions. Such reactions lead to the cellular life activities.
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There is an absence of such molecular movements in viruses, which remain non-living until they infect a living organism. Their molecular movement begins when they use the other organism’s cell molecules and organelles for producing their own proteins and replicating themselves.
Let us now discuss how living beings grow and how they maintain and repair their structures. The growth of a living organism starts with the division of its cells. When a cell divides, it forms two daughter cells from a single mother cell. The daughter cells divide and divide to give rise to tissues and organs.
Different life processes of an organism, like growth and maintenance, require energy which is obtained from food by a process called nutrition. Different organisms have varied nutritional processes depending on their environment and specific food requirements.
Food is broken down into simpler forms by a stepwise oxidizing-reducing process known as respiration. During this process, oxygen is commonly required by organisms to release energy from food for carrying out various life processes.
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Generally, in multicellular organisms all the cells are not in contact with the environment. The exchange of gases and the uptake of food occur in specialized tissues. So, food and oxygen have to be transported to all parts of the body.
For the movement of food and oxygen from one part to another, there is a transportation system. The carrying out of different life processes involves metabolism (chemical reactions in organisms), which produces harmful waste products that have to be removed from the bodies of living beings.
The process of elimination of these waste products of metabolic activity from the body is excretion. In complex organisms a specialized tissue system carries out excretion and a specialized transportation system carries the metabolic waste products to the excretory tissues.
The exchange of materials with the environment is accomplished by diffusion in unicellular organisms as the entire surface of the organism remains in contact with the environment.
Living things also respond to changes in their environment in a particular manner. They produce new individuals similar to themselves by a process called reproduction. They have a definite life cycle of birth, growth, reproduction and death.
From the above discussion it is clear that living things can be easily distinguished from non-living things as they carry out various life processes such as nutrition, respiration, transportation, excretion, etc.
Nutrition provides nutrients to the body so that it can obtain energy to carry out the activities required to stay alive. Nutrients are substances that give nourishment, which provides energy to an organism. Cells obtain nutrients from the food taken by the organism.
The food taken by the organism is complex, but nutrients are much simpler molecules. The digestive system of an organism breaks down complex food into simpler molecules, so that the cells can take them in and use them for survival, growth and reproduction.
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Nutrition promotes growth of the body, which involves the formation of new protoplasm. Nutrition meets the energy requirement of the body. Nutrition helps synthesize a variety of substances, like proteins, carbohydrates, lipids, etc., which in turn perform a variety of functions.
