Biology is the branch of science which deals with the study of living beings, both plants and animals. These organisms are found practically everywhere on this earth, even in adverse situations like host springs, Polar Regions and under the ground. If you carefully look around the school campus, you will find a variety of insects and birds flying from one place to another. Trees like bargad (banyan), neem, jamun (jambolana), peepal, mango, coconut, eucalyptus, etc., are common. Small plants such as Bougainvillea, jasmine, roses, crotons, etc., are also common.

A little beyond your school campus you may find banana, rice, wheat, and maize. The boundary wall of your campus may be fenced with babul thorns. Likewise you come across various types birds like cows, peacock, parrot, pigeon, dove, eagle, sparrows, and chickens. A large number of insects like house-flies, mosquitoes, ants, termites, bedbugs, spiders can be observed in the neighborhood. Some mammals are very common like cat, dog, cow, goat, buffalo, elephants and camels, etc. On the other hand, you will never find a whale in the desert or an elephant in the ocean. Plants and animals living in rain forests cannot live in extremely dry conditions. Thus organism can live in places which are suitable for them.

Normally, a particular organism thrives well in one environment but is unable to live comfortably in other environmental conditions. It is natural phenomenon that all organisms adjust to their changing surroundings or environment. Moreover, no organism can live alone. They depend upon other organisms for food and shelter.

The branch of biology which deals with the relationship of organisms with their environment is known as ecology. The life styles of living organisms are intimately related to their environment. There are basically two components of environment-biotic or living, which includes plants and animals, and abiotic, or nonliving, which includes surrounding conditions of water, air, light, temperature, soil, nutrients, etc. Every organism lives amidst a particular set of biotic and abiotic factors and adapts itself accordingly. If there is any drastic change in its environment, it is bound to affect the organism.