Ecology is the study of how organisms interact with one another and with their physical environment.

• OR, Ecology is the branch of biology which studies relationships of living organisms with the abiotic (physico-chemical factors) and biotic components (other species) of their environment.
• Ecology comes from the Greek words ‘oikos’, means “house” or “place to live,” and logos, means “study of”.
• Study of how organisms interact with biotic and abiotic environment.
• Biotic environment means interaction with other organisms; Abiotic environment means physical environment or physical factors like water, light, temperature, soil.
• Father of Ecology in India – Ramdeo Misra
• Ecology focus on organisms, populations, communities, ecosystems, and the biosphere.

Levels of Ecological organization:

Levels of Ecological organization

Organism: An individual living being.

Population: A group of individuals of the same species that live in the same place at the same time.    E.g. field mice living in a cornfield, monarch butterflies clustered in a tree, and people in a country.

Community or Biological community: Consists of populations of different species that live in a particular place. E.g. catfish species in a pond sharing pond with other fish species, and with plants, insects, ducks, and many other species that makes up the community.

Ecosystem: Consists of community of different species interacting with one another and with their nonliving environment like soil, water.   E.g. forest, desert, river.

• Ecosystems can be natural or artificial (human created). Examples of artificial ecosystems are crop fields, tree farms, and reservoirs,aquariums.

Biosphere: Consists of portions of earth which supports life like air, water, and soil. In effect, it is the global ecosystem in which all organisms exist and can interact with one another. It is the highest level of ecological organization.