a. Parasites have evolved the following adaptations.
1.Loss of unnecessary sense organs.
2. Presence of hook/adhesive organs and suckers.
3. Loss of digestive system.
4. High reproductive capacity.
b. In some cases, a parasitic species may evolve with its host taxa. Long-term co-evolution sometimes leads to 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.