Problem 4 - Biology: The Dynamic Science

Question

A major event during gastrulation is: a. the outward movement of cells at the dorsal lip of the blastopore. b. the displacement of the archenteron by the blastocoel. c. the formation of the coelom from the endoderm. d. the extension of ectoderm and endoderm to form the yolk sac. e. the development of ectoderm to form epidermal and neural tissues.

Step-by-Step Solution

Answer

None of the options given accurately describe a major event during gastrulation. However, option a is the closest, although the movement of cells is internal.

Step 1: Analyze Option a

Option a refers to the outward movement of cells at the dorsal lip of the blastopore. This is indeed a part of gastrulation and involves cell migration. However, this movement is internal, not outward.

Step 2: Analyze Option b

Option b suggests the displacement of the archenteron by the blastocoel. The blastocoel is a fluid-filled cavity within the blastula, but it does not displace the archenteron during gastrulation. In fact, it's the other way around: the archenteron forms by pushing into the blastocoel.

Step 3: Analyze Option c

Option c proposes the formation of the coelom from the endoderm. But actually, the coelom forms from the mesoderm, not the endoderm, making this statement incorrect.

Step 4: Analyze Option d

Option d discusses the extension of ectoderm and endoderm to form the yolk sac. In reality, the yolk sac is formed by the endoderm, not by an extension of ectoderm and endoderm.

Step 5: Analyze Option e

Option e is the development of ectoderm to form epidermal and neural tissues. This is true as the ectoderm indeed forms these structures, but it happens after gastrulation, during the process of organogenesis.