Living and the Non-Living organisms, Metabolism, Growth and Development

Living and the Non-Living

If we chemically analyse a living organism, plant or animal, we find that it is made up of carbon, hydrogen, oxygen, nitrogen and a few other elements. However, a mixture of these elements does not make a living organism. Then, how do we define life. It is difficult to arrive at a universal definition of life. Nevertheless, it is possible to characterise living things. We may say that living organisms are those characterised by the following features.

(i) Organisation All living organisms have a definite shape and size as well as physical and chemical composition inherited from their parents. This is possible because of a high degree of organisation. The molecules of which an organism is made up are organised into cells, which in turn are organised into tissues, organs and organ systems making the whole individual. This kind of complex organisation is not found in non-living things.

(ii) Metabolism Green plants obtain their nourishment from the environment in the form of water, carbon dioxide, and certain minerals which are utilised to synthesize carbohydrates during photosynthesis. Carbohydrates are in turn broken down during respiration and the energy thus released is used to synthesize other organic compounds like lipids, proteins, nucleic acids, etc. which make up the body. Animals, bacteria and fungi, on the other hand, obtain nourishment in the form of organic compounds and utilise them to synthesize compounds they need. Such reactions do not occur in non-living objects.

(iii) Growth and Development Living organisms often arise from a single cell which divides and re-divides to form a large number of cells that differentiate into the various organs of the body. These kind of phenomena are not known in the non-living world.

(iv) Reproduction Living organisms, unlike non-living, are universally recognised by their capacity to multiply their own types by means of asexual or sexual reproduction.

(v) Responsiveness All living organisms respond to stimuli, e.g., roots move towards the earth and shoots toward the sun, stomates open during the day and close during the night, and the dog wags its tail on seeing its j master. This kind of response does not occur in the non­living.

(vi) Adaptation    Organisms have the ability to adapt themselves to the needs of the environment which helps j them to survive. For example, plants growing in saline soils have a high-concentration of salts in their body and those in deserts have few leaves with thick waxy coatings. Likewise, animals living in cold climates have a thick coat of hair on the body and a chameleon can change its body colour according to its surroundings.