9.7 Scenario-Based Questions
Read the following scenario and answer the questions below.
Western Canada contains a series of tall mountain ranges that extend south through the United
States and far down into Mexico. The largest of these ranges are the Rockies and the Coast
Range, but they are all part of the same mountain-building event that occurred many millions of
years ago, and they all have similar features. In the southwestern United States, much of the
vegetation on these mountaintops is alpine, or very similar to the vegetation of the mountains in
Western Canada, and they are often referred to as “Sky Islands” because of their similarity to
each other, their higher moisture content, and their isolation from the lower, drier, areas
surrounding them.
1) There are groups of tropical birds, such as trogons and parrots, that are usually considered to
live in Central America and the mountains of southern and central Mexico. Small populations of
these birds migrate into the United States each year. It is probably true that ________.
A) more of these birds are found in the mountains of New Mexico and Arizona than in the
mountains of Colorado or Canada
B) more of these birds are found in the taller mountains of Canada than in the shorter mountains
in southern Arizona, even if the relative area of the mountains is the same
C) these birds can live in the lower, drier elevations in Canada as well as in the mountain ranges
D) these birds migrate to southern Vancouver Island in the winter because it is warmer there
E) these birds have higher genetic diversity in the Canadian populations than in the populations
in Central America
2) Large predators and omnivores, such as mountain lions and bears, roam the Sky Islands of the
southwestern United States. Which of the following statements is true?
A) Because of habitat fragmentation, the individual populations of these Sky Islands have more
biodiversity than they did in the past.
B) Because of habitat fragmentation, the individual populations of these Sky Islands have less
genetic diversity than they did in the past.
C) Because of immigration and emigration, the individual populations of these Sky Islands have
less biodiversity than they did in the past.
D) Because of immigration and emigration, the individual populations of these Sky Islands have
more biomass than they did in the past.
E) Because of extirpation, many of these individual populations have more biodiversity than they
did in the past.