What is the sequence of embryonic development stages in frogs?

• A. Zygote, morula, blastula
• B. Cleavage, blastula, gastrula
• C. Blastocyst, embryo, tadpole
• D. Egg, embryo, adult

Answer: (B)

The sequence of embryonic development stages in frogs begins with cleavage, progresses to the blastula stage, and then moves on to gastrula.

After fertilization occurs, the zygote undergoes a series of rapid cell divisions known as cleavage. This process is crucial as it results in the formation of the blastula, which is essentially a hollow ball of cells. The blastula stage is characterized by the rearrangement of cells and the formation of a blastocoel, which is a fluid-filled cavity.

Following the blastula stage, the embryo undergoes gastrulation, where cells begin to migrate and differentiate to form the three primary germ layers: ectoderm, mesoderm, and endoderm. This process establishes the foundation for further development into various tissues and organs.

The other options do not accurately represent the embryological development sequence in frogs. For instance, the concept of the blastocyst is more relevant to mammals rather than amphibians, and the sequence of egg to adult does not detail the critical embryonic stages.