Population

Look at the individuals in any population and they will not all be identical. Their characteristics differ: this is variation. The differences may involve appearance, physiology or behaviour, so a phenotype is not restricted to features that can be seen.

This does not mean that differences can never appear: a new mutation may occasionally introduce genetic variation. However, the usual outcome of asexual reproduction is a population with little or no genetic variation.

All the rabbits living in that meadow at the same time form a population. A population contains members of just one species; the foxes in the meadow form a separate population.

Researchers often cannot collect information from every member of a population. They therefore study a sample and use it to make cautious conclusions about the wider population. Sampling saves time and resources, but only a well-chosen sample can provide representative evidence.