Coevolution is where the existence of one species is tightly bound up with the life of one or more other species. Species whose lives connect, evolve together. What happens is that survival rates in each species changes as a result of changes in the other species.

Examples of coevolution are:

  • Species which mutually benefit
    • Flowers and the animals that pollinate them
    • Life-forms in a symbiosis
  • Species which are antagonistic
    • Predators and their prey
    • Parasites and their hosts

Coevolution is extremely common, and may involve more than two species. Mimicry rings, with dozens of species, are known.

New or 'improved' adaptations which occur in one species are often followed by the appearance and spread of related features in the other species.