The yolk plug of a gastrula represents which part in the later stage of development?

During gastrulation,the dorsal lip of the blastopore (the first external sign of gastrulation) appears:

In which of the following is meroblastic cleavage observed?

The point of sperm entry during fertilization in amphibian eggs forms:

Which one of the following statements is correct?

In which of the following animals are cleavage divisions restricted to a small part of the cytoplasm and nucleus in the animal pole of the egg?