(a) Parasites have evolved the following adaptations.
(i) Loss of unnecessary sense organs.
(ii) Presence of hook/adhesive organs and suckers.
(iii) Loss of digestive system.
(iv) High reproductive capacity.
(b) In some cases, a parasitic species may evolve with its host taxa. Long-term co-evolution sometimes leads to a relatively stable relationship, tending to commensalism or mutualism, as it is in the evolutionary interest of the parasite that its host thrives. A parasite may evolve to become less harmful for its host or a host may evolve to cope with the unavoidable Presence of a parasite, to the point that the parasite's absence causes the host harm.
