Comparative embryology helped clarify the relationships among major groups of animals. The bilaterians, for example, can be divided into the _____ based on the developmental fate of the blastopore.

Question

Quizplus · Accepted Answer

Comparative embryology can help in clarifying the relationships among major groups of animals. The bilaterians, for instance, are distinguished as protostomes and deuterostomes based on the developmental fate of the blastopore, with protostomes having a spiral, determinate cleavage, and deuterostomes having radial, indeterminate cleavage. Therefore, option A, protostomes and deuterostomes, is the correct answer. Option B, coelomates and acoelomates, refers to the presence or absence of a body cavity, which is not related to the developmental fate of the blastopore. Option C, coelomates and pseudocoelomates, also refers to the presence or absence of a true body cavity, but not the developmental fate of the blastopore. Option D, cnidarians and radiolarians, are not bilaterally symmetrical and thus, are not divided based on the developmental fate of the blastopore. Option E, protostomes and coelomates, is incorrect because both protostomes and deuterostomes can be coelomates or acoelomates.

Comparative Embryology Helped Clarify the Relationships Among Major Groups of Animals