What are the characteristics of living things?

Living or non-living?

A snail shell lying still on the path may still be part of a living snail. So how do we decide whether something is living? Look around your classroom: a pencil, a book, a pigeon at the window, a plant in a pot. One good way is to compare each thing with yourself, because you are a wonderful example of a living being. What can you do that a pencil or a car cannot?

Movement

Animals walk, run, fly, crawl and swim. Plants do not move from one place to another, but they do show movement. Flowers open. The leaves of Drosera, an insectivorous plant that depends on insects for its nutrition, are shaped like saucers with sticky hairs; when an insect enters, the hairs move inwards and trap it. Climbers wind themselves around any support near them.

Movement alone, though, does not prove that something is alive. A car, a fan and a river all move.

Food and growth

Living beings need food, or nutrition, to grow and develop. You cannot wear the clothes you wore four years ago, because your body has grown. Plants and animals grow too. A car never grows.

Respiration

Count your breaths in one minute after a normal walk, after a run and after a few dance steps: you breathe faster after exercise. When we breathe in, air moves into the body; when we breathe out, it moves out. Breathing is part of a process called respiration. Watch a resting dog or cow and you will see its belly move as it breathes. Plants respire too: tiny pores called stomata on the surface of leaves let air in and out. All living beings respire.

Excretion

The white patches that form on shirts in summer come from sweat, which is water and salts removed by the body as waste. Urine is another waste. Removing waste products from the body is called excretion. Plants excrete too: grass and roses give out extra water and minerals as small droplets on their leaves.

Response to stimuli

If you step on a thorn or touch a hot cup of tea, you pull away at once. Any thing or event that makes a living being respond is a stimulus (plural: stimuli). Plants respond as well. Touch-me-not (mimosa, chhui-mui or lajjalu) folds its leaves when touched, and the leaves of the amla tree come together after sunset, as if they were sleeping.

Reproduction and death

Cats have kittens and dogs have puppies, but a pencil never has young ones. Reproduction is producing new ones of one’s own kind, and it is necessary for life to continue. Finally, all living beings die. When a living being cannot show these characteristics even though food, air and water are available, it is dead.

Sorting things around you

Thing	Living or non-living?	Reason
Pencil, book	Non-living	They do not grow, eat, respire or reproduce.
Pigeon	Living	It moves, eats, grows, breathes and lays eggs.
Car	Non-living	It moves only when driven; it does not grow or reproduce.
Plant	Living	It grows, respires, makes seeds and responds to stimuli.

A seed may look lifeless, but give it water and air and it germinates and grows, so a seed is living. Find out what a seed needs in germination of seeds.