Which statement best describes an ecosystem

maintaining a state of approximate equilibrium?

(1) Nutrients from decayed organisms are

recycled in a forest ecosystem.

(2) All the frog species in a South American rain

forest become extinct.

(3) A mutation spreads through a species of

bacterium, making them unable to decompose

wastes.

(4) Mice are released into a field ecosystem as

food for a declining predator population.