In a desert ecosystem, rattlesnakes prey on kangaroo rats. During a drought, plant growth declines, leading to fewer seeds for the rats.

Two bird species, Species A and Species B, both nest in the same type of tree cavity in a forest.

Cleaner fish remove parasites from larger reef fish. When cleaner fish populations are healthy, larger fish are healthier and more abundant.

In a prairie, bison graze on grasses. Grazing reduces grass height but helps prevent tall shrubs from taking over.

Arctic foxes feed on lemmings. When lemming populations increase, fox populations also grow.

Dragonfly nymphs and beetle larvae both eat mosquito larvae in a pond.