Q.Remora & shark exhibits:

A parasite is an animal that makes its living inside or on another animal, the host, taking food and shelter from it. Living this way sounds easy, but it poses a real problem: the host's body is a slippery, moving, food-rich environment that constantly tries to move things along and out. To survive there, parasites carry a set of special body tools — parasite adaptations — that let them hold on and feed without needing the equipment a free-living animal would use.

The flatworms make an especially clear example. Most of them live as endoparasites inside other animals, including human beings, and they are fitted out for it:

• They carry hooks and suckers that let them grip the host's tissues and avoid being swept away.
• Some absorb nutrients straight through the body surface, taking food directly from the host rather than through a mouth and gut.

Roundworms show the parasitic habit too, with many living as parasites inside plants and animals, although the phylum also contains free-living forms in water and soil. Tapeworm and liver fluke are well-known parasitic flatworms, while roundworm, filaria worm and hookworm are parasitic roundworms. …