In the 1800s, populations of sea otters were decimated. But sea urchin populations did not increase drastically until the 1950s, when the other sea-urchin predators were overfished. That if you want one species to increase, you must sacrifice others. That humans can decimate the populations of as many species as they need to, as long as they leave one species to fill each function. D. That sea otters are not as important to the control of sea urchin populations as are lobsters, crabs, and fishes.
Estuaries are A. very diverse, but none of the species is very abundant.
B. not very diverse, and none of the species is very abundant. C. very diverse, and each species is very abundant. D. not very diverse, but each species is very abundant. An organism that stays in one place on the bottom of an estuary, A. will live in fresh water all of the time since the salt water, being less dense, stays at the surface. C. will be exposed to varying salinities as the tide moves in and out of the estuary.