Earth is truly a marvelous planet and consists of living and nonliving components. It is the only planet in our solar system that has the components necessary to support life as we recognize it. The planet is only a tiny part of the universe, but it is the home of human beings and many other organisms. Animals and plants live almost everywhere on the surface of earth. Perhaps the most amazing feature of our planet is the rich diversity of the life that exists here. Millions of beautiful and intriguing species populate the earth and help sustain a habitable environment. This vast multitude of life creates complex, interrelated communities where towering trees and huge animals live together with, and depend upon, tiny life-forms such as viruses, bacteria, and fungi.

Ecology is an interdisciplinary branch of biology, which deals with study of distribution, structure, various aspects of life organisms and their interaction with environment. Depending upon the field of study, it is divided into two aspects - plant ecology and animal ecology, though the two cannot be separated from each other.

The Environment (from the French environner: to encircle or surround) can be defined as : (1) the circumstances or conditions that surround an organism or group of organisms, or (2) the complex of social or cultural conditions that affect an individual or community. Since humans inhabit the natural world as well as the built or technological, social, and cultural world, all constitute important parts of our environment. The different types of organisms living in a particular environment are not only independent and mutually reactive but also react with the environment. Environmental science is the systematic study of our environment and our proper place in it. A relatively new field, environmental science is highly interdiscipunary, integrating natural sciences, social sciences, and humanities in a broad, holistic study of the world around us. In contrast to more theoretical disciplines, environmental science is mission-oriented. That is, it seeks new, valid, contextual knowledge about the natural world and our impacts on it, but obtaining this information creates a responsibility to get involved in trying to do something about the problems we have created.