A level Biology exam revision resources written by A level Examiners


Ecology is the study of living organisms and how they interact with their environment. It is an important part of modern Biology (though not one that is universally enjoyed by A level Biology students).

Because ecology is a very broad area of study exam questions often have unfamiliar stimulus material in them such as organisms that aren't on the specification. It's important not to get distracted by this because the examiners are always trying to test your understanding of the key concepts that are covered by the specification.

A useful starting point in ecology is to become familiar with some of the key terms.

The basic unit of ecology is the ecosystem. This is a reasonable self-contained unit that contains organisms that are interacting with each other and their environment E.g. a forest or a lake.

All the organisms of a single species in 'a given area' are the population of that species.

The 'given area' within an ecosystem where a population lives is the habitat.

All the populations in one habitat make up a community.

How one particular species fits into a food web and the area it lives in defines the niche that that species has.

The environment of an organism is the external conditions that surround the organism. Environments consist of biotic (biological) and abiotic (physical) factors.

Light intensity



Mineral ion

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