What is parasitism? Describe the adaptations of parasites and explain brood parasitism with an example.

1. 1 · Define in one line. Parasitism is a (+, −) interaction in which a parasite lives on or in a host, takes food and shelter, and harms it.
2. 2 · Explain host specificity. Many parasites use only one host species, and the host and parasite co-evolve.
3. 3 · List the adaptations.
   • Loss of unnecessary sense organs.
   • Suckers or adhesive organs.
   • Loss of the digestive system.
   • High reproductive capacity.
   • Complex life cycles with intermediate hosts.
4. 4 · Give ecto and endo examples.
   • Ectoparasites: lice, ticks, Cuscuta (no chlorophyll, no leaves).
   • Endoparasites: liver fluke (snail and fish as intermediate hosts), malarial parasite (mosquito vector).
5. 5 · Explain brood parasitism. The koel lays its eggs in a crow's nest; the eggs resemble the host's, so the crow incubates them.
6. 6 · Link to real life. School deworming drives in India target gut endoparasites such as roundworms.
7. 7 · Close in one line. So parasites are specialised to take from the host, usually at the cost of its health.

Scoring tip: Name Cuscuta's two losses (chlorophyll and leaves) and the liver fluke's two intermediate hosts. Both are favourite 1-mark points.