Describe the role of the American alligator as a keystone species

Alligators have a big habit of helping carnivores like the wolf, cougar, bear, etc. hunt off deer and fish. Even with this amount of carnivores around, just a simple change as one carnivore removal such as the alligator would increase the fish population. This would make the bears have more time for fishing. The next thing to happen would lead to bears increasing more rapidly, then deer, elk, and moose begin to decrease due to the bear increase.

supercell thunderstorms are perhaps the most violent of all thunderstorm types, and are capable of producing damaging winds, large hail, and weak-to-violent tornadoes

since there are no options posted i'll give you a few examples.

a dolphin's flipper, bird's wing, cat's leg.