Parland’s alligator population has been declining in recent years, primarily because of hunting. Alligators prey heavily on a sp
ecies of freshwater fish that is highly valued as food by Parlanders, who had hoped that the decline in the alligator population would lead to an increase in the numbers of these fish available for human consumption. Yet the population of this fish species has also declined, even though the annual number caught for human consumption has not increased. Which of the following, if true, most helps to explain the decline in the population of the fish species?
(A) The decline in the alligator population has meant that fishers can work in some parts of lakes and rivers that were formerly too dangerous.
(B) Over the last few years, Parland’s commercial fishing enterprises have increased the number of fishing boats they use.
(C) The main predator of these fish is another species of fish on which alligators also prey.
(D) Many Parlanders who hunt alligators do so because of the high market price of alligator skins, not because of the threat alligators pose to the fish population.
(E) In several neighboring countries through which Parland’s rivers also flow, alligators are at risk of extinction as a result of extensive hunting.
(C) The main predator of these fish is another species of fish on which alligators also prey.
Explanation:
The ecosystems are complex systems, and removing one species of them, always has a chain reaction and affects the population of the other species, be it in a positive or negative manner. In this case, the alligators prey upon fish, multiple different species. The alligators though have been removed from the ecosystem, thus the apex predator exists no more. This has opened up the top predator niche in the food chain in this particular ecosystem. The predatory fish species had no predators of its own, so its population increased, thus it needed more food, and that food was obtained by hunting the other fish species, resulting in a decline in the population of the other species of fish. Only when the carrying capacity is reached in the ecosystem for the predatory fish, the population of the other fish will stop declining.
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<span>Regulation of the cell cycle is dependent upon cyclins and cyclin-dependent kinases. The key(s) that allows a cell to progress beyond the restriction point is (are)
