Employment in the science of the interrelationships between organisms and their enviroments.

1. The branch of the biological sciences that deals with the relationship between organisms and their environment, including their relationship with other organisms.
2. The science concerned with interactions between organisms and the environment on spatial scales ranging from parts of individuals to the biosphere as a whole.

Literally, ecology means the "study of houses". The word was coined as ökologie by Ernst Haeckel, a German zoologist, in the 1870’s, based on the Greek word oikos. Although this means “house”, Haeckel was using it in the wider sense as “dwelling, habitat”. It was adopted into English soon after its coinage, originally as oecology which is similar to a Latin form.

Ecology has been divided into four major sub fields:

• Physiological ecology, concerned with interactions between individual organisms and the environment.
• Population biology, the regulation of population growth and population size, and interactions among populations.
• Community ecology, characteristics of the collective properties of the organisms in an area.
• Ecosystem ecology, regulation of the flows of energy and material in terrestrial and aquatic ecosystems.

The study of the flows of material and energy resources in industrial and consumer activities, of the effects of these flows on the environment, and of the influences of economic, political, and social factors on the use of such resources: "Industrial ecology utilizes the principles from ecology, thermodynamics, and systems theories."

The study of the relationship between the activities of soil organisms and the overall soil environment: Part of Jim's universities studies in biology included soil ecology in which he learned about the interactions between organisms and physical and chemical substances.

1. The study of the effects of thermal conditions on living organisms, either in a naturally heated environment or in one affected by human activities.
2. The study of the independent and interactive biotic and abiotic components of naturally heated environments.