Question

Study the population growth curve of three species of squirrels on an island. Red squirrels and gray squirrels have been the native species on the island for the past 1,000 years. The black squirrel is an invasive species. Invasive species aren’t native to the ecosystem. They move into an ecosystem because of natural changes or human intervention. In 2005, black squirrels entered this island. Red squirrels and black squirrels have identical food requirements, but gray squirrels eat different kinds of food. What’s the plausible reason for the population change?


A. 

The red squirrel has no predators, and the black squirrel has many predators.

B. 

The gray squirrel competes with the black squirrel for food.

C. 

The black squirrel has no predators, and the red squirrel faces higher competition for resources.

D. 

The black squirrel has many predators and faces tougher competition for resources.

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Answer 1

Answer:

Option C, The black squirrel has no predators, and the red squirrel faces higher competition for resources.

Explanation:

Here , the black squirrel  is an invasive species and it competes with red squirrel for food as they rely on the same food unlike the gray squirrel.

As shown in the graph, the black squirrel's population has increased at a very fast rate as compared to the population of grey and red squirrel.  

Thus, it can be concluded that there are no predators for black squirrel thereby contributing to it high growth. Also the red squirrel face tough competition with the black squirrel for food due to which population of red squirrel is declining.

Hence, option C is correct.

Answer 2

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