A species is a category within the classification system. Living things of the same type belong to the same species. For example, humans are one species and dogs are another species.

Individuals of the same species can reproduce to make more individuals of the same species. Two individuals belonging to different species cannot normally reproduce together. If they do, their offspring is usually infertile and unable to reproduce.

For example animals called ligers are produced when a male lion and a female tiger reproduce. But a liger cannot have offspring. This means that lions and tigers are different species.

What is variation?

All people are human. They belong to the same species. Your friends and classmates may have different eye colour and hair colour. Some will be boys and some will be girls. Some will be tall and some will be shorter. The presence of differences between living things of the same species is called variation.

Variation between different species is always greater than the variation within a species.