Key Concepts

CONCEPT 13.1 Parasites typically feed on only one or a few host species, but host species have multiple parasite species.

CONCEPT 13.2 Hosts have mechanisms for defending themselves against parasites, and parasites have mechanisms for overcoming host defenses.

CONCEPT 13.3 Host and parasite populations can evolve together, each in response to selection pressure imposed by the other.

CONCEPT 13.4 Hosts and parasites can have important effects on each other's population dynamics.

CONCEPT 13.5 Parasites can alter the outcomes of species interactions, thereby causing communities to change.