SAT Subject Biology Practice Question 283: Answer and Explanation

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Question: 283

13. Homologous structures, which have similar underlying structures but may have different functions, are formed by

A. divergent evolution
B. speciation
C. segregation
D. convergent evolution
E. stabilizing selection

Correct Answer: A


A Divergent evolution occurs when the same ancestral organism is placed into different environments and must then adapt to function in these different environments. Thus the same original structures evolve separately and "diverge" from one another. Examples of homologous structures are the arm of a man, the wing of a bat, and the flipper of a whale. All have the same basic bone structure but vastly different functions. The opposite of divergent evolution is convergent evolution, in which vastly different organisms are placed into the same environment and must adapt to perform similar functions with different structures. Convergent evolution produces analogous structures, examples of which are the wings of bats, the wings of birds, and the wings of butterflies. Speciation is often the result of divergent evolution, not the cause of it.

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