Living organisms are easily distinguishable from non-living things by the peculiar characteristics which they possess and that are commonly observed externally. It can be observed that a pigeon can eat by picking grains, it can fly and walk about, can pass waste materials to the exterior and would fly away on perceiving an unusual sound or movement.
Those processes which only living organisms can perform are called functions of life and stoppage of these proccesses in an organism may lead to death of the organic!I I,e. It losses its life . the functions of life are movement, respiration, nutrition, irritability, growth, excretion and reproduction which are abbreviated as M.R.N.I.G.E.R. For easy memory recall by students.
Nutrition is the taking in food into the body of am organism in order to stay alive. Respiration is the use of air to release energy from the food taken in. The removal of poisonous waste products of chemical processes in the cells of living organisms is called excretion. Growth is the irreversible increase in size and form of an organism as a result of the usage of food to build new rissues. Reproduction can be define as the ability of a living organism to produce new individuals or offspring in order that its type may live on from generation to generation. The ability to sense changes in the surroundings like change in temperature, sound, light and chemicals is called irritability or sensitivity. In order to carry out all their activities, living organisms are able to move part of or the entier body from place to place-movement and locomotion.