Which statement best describes the role of gastrulation in vertebrate development?

• A. It results in the formation of the neural tube
• B. It reorganizes the blastula into three germ layers
• C. It involves cell division without growth
• D. It forms the placenta

Answer: (B)

Gastrulation reorganizes the blastula into three germ layers in vertebrate development. This moves cells so they form the ectoderm, mesoderm, and endoderm, establishing the tissue foundations that will give rise to all organs and major body plans. Neural tube formation is a later event that arises from the ectoderm during neurulation, not during gastrulation itself. Placenta formation involves extraembryonic tissues beyond the germ layers, and cleavage refers to rapid cell division without growth that occurs earlier than gastrulation. So the key role of gastrulation is creating the three germ layers.