Explain co-evolution with reference to parasites and their hosts. Mention any four special adaptive features evolved in parasites for their parasitic mode of life.
Co-evolution is a phenomenon where many parasites have evolved to be host-specific in such a way that both the host and parasite tend to co-evolve, i.e. if the host develops/evolves special mechanism for rejecting or resisting the parasite the parasite has to evolve mechanism to counteract and neutralise them to succeed with the same host species.
Parasites have special adaptations according to their lifestyles such as; loss of unnecessary sense organs, presence of adhesive organs or suckers, loss of digestive system, and high reproductive system.