Question

Blastopore is
A. Opening of neural tube
B. Opening of gastrocoel/archenteron
C. Future anterior end of embryo
D. Found in blastula

Answer 1

Hint: The blastopore is produced during gastrulation by an inward migration of the archenteron's endoderm and mesoderm cells. The blastopore becomes the anus of many animals, although it covers up at the end of gastrulation in others, and can emerge again at or near the same place.

Complete Answer:
A) Animals produce either two or three embryonic germ layers. Animals exhibiting radial symmetry form two germ layers, an inner endoderm layer and an outer ectoderm layer. Such animals are known as diploblasts.
- The animals with bilateral symmetry form three tissue layers and are known as triploblasts. They are the inner endoderm layer, the middle mesoderm layer and the outer ectoderm layer.

B) The triploblastic animals are further divided according to the ability of forming an internal body cavity called a coelom.
- Triploblasts that do not have a coelom are called acoelomates. Triploblastic Coelomates that are bilaterally symmetrical, can be further split into two classes, protostomes and deuterostomes, according to variations in the early stage of embryonic development.
- These two classes are divided on the basis of which digestive cavity opening emerges first, the mouth or anus. The mouth or anus emerges from a structure known as the blastopore. It forms the opening of the archenteron on the embryo's surface in the gastrula stage.

Therefore, the correct answer is option B i.e., Opening of gastrocoel/archenteron.

Note: Gastrulation is the process that transforms the embryo from a blastula with a single cell layer to a gastrula with several cell layers during embryonic development.