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. [3]

Answer 1

Co-evolution is a term used to describe the mutual changes in two or more species, usually one following the other, that affect their interactions.
In terms of the relation of host and parasite, it can be explained as follows :
A parasite is an organism that derives nourishment and protection from another living organism known as the host, but in doing so, it also harms the host. The host evolves over a long period of time to protect itself from the parasite, while the parasite evolves so that it can find another way to derive nutrition from the host and hence, the cycle continues. [1]

Four special adaptive features evolved in parasites for their parasitic mode of life are as follows :
1. Parasites have suckers/hooks as organs for attachment that help them to firmly attach to the host body and help in deriving nutrition from them. For example suckers and hooks in Taenia solium. [0.5]
2. Parasites are covered by protective body covering, that is tegument (in case of Taenia solium) and cuticle (in case of Ascaris lumbricoides) to protect them from harmful effects of digestive enzymes of the host.[0.5]
3. All parasitic organisms usually lack locomotory structures, they do not require to move in search of food.[0.5]
4. High reproductive capacity of parasitic organisms ensures the continuation of parasitic race.[0.5]