Parasitism - Practice Questions & MCQ

• It is the mode of interaction between the two species in which one species (parasite) depends on the other species (host) for food and shelter and damages the host.
• In this process, one organism is benefited (parasite), while the other is harmed (host).

Adaptation Methods of a Parasite:

• Parasite is host-specific in a way that both host and parasite tend to co-evolve.
• Loss of unnecessary sense organs.
• Presence of adhesive organs or suckers.
• Loss of digestive system.
• High reproductive capacity.
• The life cycles of parasites are often complex, involving one or two intermediate hosts or vectors to facilitate parasitisation of its primary host, examples:
  • Human liver fluke (a trematode parasite) depends on two intermediate hosts (a snail and a fish) to complete its life cycle.
  • Malarial parasite (Plasmodium) needs a vector (mosquito) to spread disease to other hosts.
• Majority of parasites harm the host. They reduce the survival, growth and reproduction of the host. They reduce its population density by making it physically weak.

Ectoparasites:

• Ectoparasites feed on the external surface of the host organism for food and shelter.
• Examples are lice on humans, ticks on dogs, copepods in marine fishes and Cuscuta, a parasitic plant that grows on hedge plants.

Endoparasites:

• Endoparasites live inside the host’s body at different sites like liver, kidney, lungs, etc., for food and shelter. 
• Examples are tapeworm, liver fluke, Plasmodium, etc. 
• The life cycles of endoparasites are more complex because of their extreme specialisation.

Brood parasitism:

• Brood parasitism is a phenomenon in which one organism (parasite) lays its eggs in the nest of another organism. 
• For example, eggs of cuckoo (koel) and the crow resemble in size and colour, to reduce the chances of the crow (host) detecting the foreign eggs (cuckoo’s) and ejecting them out from the nest.