Which statement is true about embryonic development in animals?

• A. All animals develop from a single germ layer.
• B. Organogenesis occurs before the formation of germ layers.
• C. Cleavage results in the formation of a blastula with differentiated cells.
• D. The process of gastrulation forms the three primary germ layers.

Answer: (D)

Verified step by step guidance

1. Understand the stages of embryonic development: Fertilization, Cleavage, Blastulation, Gastrulation, and Organogenesis.
2. Recognize that during gastrulation, the embryo reorganizes into a structure with three primary germ layers: ectoderm, mesoderm, and endoderm.
3. Identify that cleavage is an early stage where the zygote divides without growth, forming a blastula, which is a hollow ball of cells.
4. Note that organogenesis, the formation of organs, occurs after the germ layers are established during gastrulation.
5. Conclude that the statement 'The process of gastrulation forms the three primary germ layers' is true, as it accurately describes a key event in embryonic development.