Scenario I In a study published in 2003, Martin Wikelski and L. Michael Romero m

Question

Scenario I In a study published in 2003, Martin Wikelski and L. Michael Romero measured the length of Galápagos marine iguanas and observed the percent survival of different-sized animals, all of the same age. The graph shows the log snoutvent length (SVL, a measure of overall body size) plotted against the percent survival of these different size classes for males (open circles) and females (closed circles).

1. Examine the figure above. Assuming the average male SVL is ~2.4 mm, what type of selection for body size appears to be occurring in the male marine iguanas?

A. Directional

B. Disruptive

C. Stabilizing

Wikelski and Romero (2003) found that large marine iguanas had higher reproductive success than smaller iguanas did, but the large iguanas were also generally in poor body condition because they could not eat enough to sustain their higher metabolic needs. However, at higher temperatures their foraging efficiency improved, allowing them to eat more. Based on this information, iguana size should _____ as global warming gradually increases air and water temperatures in the Galápagos Islands.

A. Stabilize around the mean body size

. B. Increase

C. Decrease

Currently the only predators of Galápagos marine iguanas are Galápagos hawks. Iguana body size is not correlated with risk of hawk predation, although small iguanas can sprint faster than large iguanas. If predators (for example, cats) that preferably catch and eat slower iguanas are introduced to the island, iguana body size is likely to _____ in the absence of other factors; the iguanas would then be under _____ selection.

A. Increase; directional

B. Decrease; directional

C. Increase; disruptive

D. Decrease; disruptive

E. Stay the same; stabilizing

Explanation / Answer

Ans 1. The following are the observations and answers:-

C. Stabilizing Selection tends to appear for body size

A. Stabilize around the mean body size, as the global warming increases, the temperature would increase as well.

B. Decrease (as smaller iguanas sprint faster and to survive they have to run) directional selection

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