23 answer a 2 which of the following was the least

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Answer: A 2) Which of the following was the least likely factor causing the Cambrian explosion? A) the emergence of predator-prey relationships between animals B) the accumulation of diverse adaptations, such as shells and different modes of locomotion C) the movement of animals onto land D) the evolution of Hox genes that controlled development E) the accumulation of sufficient atmospheric oxygen to support the more active metabolism of mobile animals Answer: C 3) Acoelomates are characterized by 4) The distinction between sponges and other animal phyla is based mainly on the absence versus the presence of 5) Which of these is a point of conflict between the phylogenetic analyses presented in Figures 32.10 and 32.11 of your textbook? 6) What is the main basis for placing the arthropods and nematodes in the Ecdysozoa in one hypothesis of animal phylogeny? A) Animals in both groups are segmented. B) Animals in both groups undergo ecdysis. C) They both have radial, determinate cleavage, and their embryonic development is similar. D) The fossil record has revealed a common ancestor to these two phyla. 24
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E) Analysis of genes shows that their sequences are quite similar, and these sequences differ from those of the lophotrochozoans and deuterostomes. Answer: E 25
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