Use the following information to answer the question below.
Martin Wikelski and L. Michael Romero (Body size, performance and fitness in Galápagos marine iguanas, Integrative and Comparative Biology 43 [2003]:376-86) measured the snout-to-vent (anus) length of Galápagos marine iguanas and observed the percent survival of different-sized animals, all of the same age. The graph shows the log snout-vent length (SVL, a measure of overall body size) plotted against the percent survival of these different size classes for males and females.

Examine the figure. What type of selection for body size appears to be occurring in these marine iguanas?
A) directional selection
B) stabilizing selection
C) disruptive selection
D) You cannot determine the type of selection from the above information.

Question

Use the following information to answer the question below.
Martin Wikelski and L. Michael Romero (Body size, performance and fitness in Galápagos marine iguanas, Integrative and Comparative Biology 43 [2003]:376-86) measured the snout-to-vent (anus) length of Galápagos marine iguanas and observed the percent survival of different-sized animals, all of the same age. The graph shows the log snout-vent length (SVL, a measure of overall body size) plotted against the percent survival of these different size classes for males and females.

Examine the figure. What type of selection for body size appears to be occurring in these marine iguanas?
A) directional selection 
B) stabilizing selection 
C) disruptive selection 
D) You cannot determine the type of selection from the above information.

Quizplus · Accepted Answer

The graph shows a curve that is narrowest at the highest percent survival point, indicating that individuals with intermediate body sizes have the highest survival rate. This is an example of stabilizing selection, as the extreme sizes have reduced survival rates.

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