The answer is coevolution.
Coevolution is a change in one species that results from a change in another species that it interacts with. For example, some species of orchid and African moth coevolved. That was a consequence of African moths' dependence on flower nectar and the orchids' dependence on moths' help in pollination. This two species coevolved, therefore the orchids have deep flowers while African moths have long proboscides.