While living in a

Parasites have evolved special adaptations while living on and in the host species they are as follows:

(i) The loss of unnecessary sense organs for example: lice, mites and fleas don't have wings.

(ii) Presence of adhesive organs or suckers to cling on to the host for example - in tapeworms and leeches.

(iii) Loss of digestive system i.e., tapeworm.

(iv) High reproductive capacity i.e., roundworm produces large progeny.