This figure shows the geological history of North and South America and the closing of the Isthmus of Panama
If a single species were distributed throughout the region indicated by the arrow in the left-most panel, and today is found as two separate species, one in the Atlantic Ocean and one in the Pacific, would this be more likely to be an example of allopatric speciation by the dumbbell model or the peripheral isolate model? Why?
What will be an ideal response?
ANS:
This would more likely be an example of the dumbbell model, which splits a population roughly in two. With a widespread distribution originally, there is no reason to expect that the population on one side was smaller than the other side as found in the peripheral isolate model.
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Agglomeration effects
A) have limited the growth of the computer industry in Silicon Valley. B) typically slow down regional economic development. C) are a form of external economy. D) occur when businesses are located near each other, but are not interdependent with each other. E) include both A and B.
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