Ecosystems and Communities

An ecosystem is a complex network of living organisms interacting with each other and their environment. In this lesson you will learn the key ecology terms, how energy flows through food chains and webs, and why energy is lost at each trophic level.

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Key Ecology Definitions

You must know these terms precisely — examiners look for exact definitions:

Term	Definition
Ecosystem	A community of living organisms (biotic) interacting with the non-living (abiotic) components of their environment
Population	All the organisms of one species living in a particular area at a particular time
Community	All the populations of different species living and interacting in a particular area at a particular time
Habitat	The place where an organism lives
Niche	The role an organism plays within its ecosystem — including what it eats, what eats it, and how it interacts with its environment
Biodiversity	The variety of different species of organisms on Earth, or within an ecosystem

How They Relate