Question

These pictures compare the numbers of prairie dogs in an area at twodifferent times. The picture on the right shows the area 10 years after thepicture on the left.Which statement best explains the change over the 10-year period?

Answer 1

The change over the years can be explained by the statement in option A which states that both the birth rate and the immigration rate have decreased.

What are birth and immigration rates?

Birth rate refers to the number of individuals born in a period.

Immigration rates refer to individuals who moved regions during a given period.

With a high immigration rate, the animal population tends to decrease, however, in the image shown above, we can see that this is not what happened. The immigration rate decreased, meaning that the population did not change in size, but the birth rate also fell, causing the number of individuals who died to be greater than the number of individuals who were born, thus reducing the size of the population.

Answer 2

In the first picture, we can see clearly a larger population of prairie dogs than in the second one (10 years later). If we look at the possible explanations of this, we have one that says that the immigration state remains stable and the birthrate increased, this one cannot be, because one of the rates increased, therefore, it´s expected an increase or at least a stable number of individuals. C statement says that inmigration and birth rate increased, so just like the previous statement, this cannot be, an increase in population numbers would be expected. D statement, mentions a new rate, death rate, however, this one decreased, meanwhile, immigration remained stable, this one cannot explain it either because