D. Predators
Predators keep populations of other species in check. This was pretty clearly demonstrated in Yellowstone National Park after the wolves were eradicated there. The deer populations increased to the point that the aspen trees nearly disappeared due to the saplings' being eaten by deer. Since the reintroduction of wolves to the park, the aspen trees have begun to flourish once again.
The growth of plants and formation of land mammals characterized the paleozoic era.
Answer:
use all practicable means to create and maintain conditions under which man and nature can exist in productive harmony
Explanation: