A researcher working with the embryo of the sea snail Ilyanassa allows the embryo to go through two cleavages and then removes one of the four cells.The embryo continues to develop into a swimming larva, but the larva is missing a number of structures, such as the intestine, heart, retractor muscles, and eyes.From this, the researcher is most likely to conclude that

Question

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The missing structures in the larva suggest that the cell removed from the four-cell stage was necessary for the proper development of these structures. This indicates that there are informational molecules present in the early embryo that restricts the fate of early blastomeres. Therefore, choice C is the best option. Choice A is not correct because the missing structures indicate that the removed cell was necessary for their development. Choice B is not applicable as it does not relate to the sea snail embryo development. Choice D is incorrect as dividing the embryo at the four-cell stage will result in incomplete development. Choice E is incorrect because the missing structures suggest that the blastomeres are not autonomous and require signals from neighboring cells.

A Researcher Working with the Embryo of the Sea Snail