What does coevolution refer to?

Coevolution refers to the evolutionary changes that occur in two or more species that interact closely with each other, leading to reciprocal adaptations. This process often arises in relationships such as predator-prey, parasite-host, or mutualistic interactions, where the traits of one species influence the evolution of traits in another. For instance, the relationship between flowering plants and their pollinators exemplifies coevolution, as plants develop traits to attract pollinators while pollinators may evolve to effectively access the plant's nectar.

The other options address aspects of evolution but do not capture the essence of coevolution. Changes in species due to competition focus primarily on the struggle for resources rather than the mutual influence of interacting species. Adaptation of organisms to their environment is a broader concept that does not necessarily involve interaction with other species. Lastly, the extinction of non-adaptable species pertains to survival and natural selection but does not reflect the specific interactions and reciprocal influences seen in coevolution.