Biology 7.1 Investigating variation

Interspecific variation = when one species differs from another.

Intraspecific variation = when members of a species differ from members of the same species.

Making measurements

• usually measuring aspect of living organisms and all living organisms are different.
• need lots of measurements.
• can't accurately measure using just one, and can't measure all in existence.
• to get around this, biologists use samples.

Sampling = taking measurements of individuals from the population of organsims being investigated.

Theoretically, individuals are representative of population. However, sample could be unreliable:

• Sampling bias: unrepresentative choices by investigators, intentionally or unintentionally e.g. likely to pick buttercups from area covered in nettles or cow dung?
• Chance: by pure chance may not be representative.

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