A shovel - A shovel, a mole paw, a human hand, and a mole...

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A shovel, a mole paw, a human hand, and a mole cricket forelimb: Which structures are homologous? Which share functional constraints? Homology "exists for important functional reasons … not due to shared ancestry" Homology is similarity in structure and position that occurs because a trait occurred in a common ancestor. If the similarity is not due to common ancestry, the structures would not be homologous. Biologists test alternative explanations, including shared function, natural laws, and other constraints. Like homology, these effects are all testable. Furthermore, similarity in shape, as between mole cricket forelimbs and the paws of a mole, is not homology. No one has ever suggested such a thing, and Explore Evolution is grossly misleading in suggesting otherwise. The errors Explore Evolution promotes are common only in the creationist literature. Once more, Explore Evolution confuses students rather than bringing clarity to a subject. A good textbook would explain that, and show how scientists test these hypotheses;
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This note was uploaded on 11/08/2011 for the course BIOLOGY BSC1086L taught by Professor Leostouder during the Fall '10 term at Broward College.

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A shovel - A shovel, a mole paw, a human hand, and a mole...

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