Ecology is the branch of biology that is the study of how living organisms interact with their environment. In its strictest definition, the term environment refers to any aspect of the physical world that affects life.

Ecology, then, investigates relationships in the living world. Ecological research may concentrate

*on a single organism interacting with its environment

*on populations of a single species

*on all organisms in an ecosystem

*on environmental factors that affect life

*on several populations of different species that live together in a community.

Ecologists recognize that no organism can function without interaction with the environment in which it lives.

The environment is made up of both biotic factors and abiotic factors. Biotic factors are the parts of the environment that are living—all organisms, including plants, animals, bacteria and fungi, are biotic. So are humans, though we often see ourselves and the communities in which we live as separate from the rest of the natural world.

We may think of nature as the open spaces, parks, mountains, forests, wetlands and places where other animals live apart from our human settlements. But ecosystems include humans, just as they do bacteria, pond snails, and daisies. Nature affects us just as fully as we impact nature.

Abiotic factors are the parts of the environment that are not living, but are necessary to allow the biotic factors to function. Abiotic factors include bedrock and soils, climate, sunlight, water, minerals, atmosphere, and so on.