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.