Question

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.

Answer 1

Host–parasite co-evolution is a special case of co-evolution. it is defined as the reciprocal adaptive genetic change of two antagonists (e.g. different species or genes) through reciprocal selective pressures. Hosts and parasites exert reciprocal selective pressures on each other, which may lead to rapid reciprocal adaptation. In the particular case of host–parasite coevolution the antagonists are different species of host and parasite.

If the host evolves a special mechanism for rejecting or resisting the parasite, then the parasite has to (simultaneously) evolve i..e, co-evolve the mechanism to counteract and neutralise them.

Parasitic adaptation in animals:

(i) Loss of (unnecessary) sense organs in animals

(ii) Presence of adhesive organs/suckers

(iii) Loss of digestive system

(iv) High reproductive capacity

(v) Resemblance of eggs in the case of brood parasitism