Three-spined stickleback fish (Gasterosteus aculeatus)show substantial heritable variation in gill-raker length.Fish caught in open water tend to have longer gill rakers and eat different foods than do those caught in shallower water.Longer gill rakers appear to function better for capturing open-water prey,while shorter gill rakers function better for capturing shallow-water prey.Which of the following types of selection is most likely to be found in a large lake (open water in middle and shallow water around the sides)with a high density of these fish?

Question

Quizplus · Accepted Answer

In a large lake that has open water in the middle and shallower water around the sides, disruptive selection is the most likely type of selection that will occur. This is because longer gill rakers are better for capturing open-water prey and shorter gill rakers are better for capturing shallow-water prey. Since the two different types of prey are found in different areas of the lake, the stickleback fish with longer and shorter gill rakers are more likely to survive and reproduce, while those with intermediate-length gill rakers will be at a disadvantage. This situation would result in disruptive selection, which favors extreme phenotypes over intermediates.

Three-Spined Stickleback Fish (Gasterosteus Aculeatus)show Substantial Heritable Variation in Gill-Raker