All organisms require energy in order to stay alive. Energy is utilised to do the various bodily functions such as breathing, ingesting and digesting food, excreting, reproducing, locomotion, etc. Energy is obtained from food. Thus the process of intake of food is vital for the survival of an organism as it provides energy. This intake of food is called nutrition.
All living creatures need food. The food is consumed so that energy is obtained. The energy is utilised by the body for various purposes like locomotion, conduction of impulses, repair of damaged tissues, building of cell materials, etc.
In unicellular organisms a single cell carries out all the life processes as the cell itself is the organism. In advanced forms like the few-celled algae, protozoa, sponges, etc., the size of the organism ensures that all the cells are not very far from each other.
The steam engine uses the power generated from steam pressure to move. Coal is used in furnaces to heat water in the boiler to generate steam. Steam pressure makes the wheels of the engine move. As coal is burnt, smoke is emitted and ash is left behind in the furnace. Smoke is let off through the chimney and the ash is removed periodically.
As the complexity of the individuals, plants or animals increases the different cells and organs become separated from each other by greater distance. Thus it becomes necessary to have a system by which the different parts of the organisms can function as a single unit. This is possible only if the different parts can coordinate with each other and carry out a particular function.
Reproduction is defined as the production of individuals of the same species, that is the next generation of the species. While it is one of the fundamental characteristics of living things, it is not an essential life process. An individual can live without reproducing, but, a species cannot survive without reproduction.
Heredity is the transmission of characteristics, physical or mental from parents to offspring, that is from one generation to the successive generation.
Environment is defined as the surroundings in which the organism lives. The environment may be the physical environment, the chemical environment or the biological environment. Thus, the environment has two components - abiotic and biotic.