Question

In a frog, gastrulation process involves
A. Epiboly
B. Emboly
C. Invagination
D. All of the above

Answer 1

Hint: Gastrulation is a phase in the embryo development in animals where blastula develops into gastrula. The process of gastrulation involves the following steps:
> Zygote formation
> Division of zygote into eight celled stages.
> Blastulation
> Gastrulation.
> Gastrula is made up of 3 layers-ectoderm, mesoderm and endoderm.

Complete answer:
The formation of the gastrula not only involves the division of the cell but the arrangement of cells is also important. The arrangement of cells is done by the movement of cells along the specific paths which is known as morphogenetic movements. These movements are listed below:
Epiboly- blastopore the cavity present in the embryo once formed the animal hemisphere cells undergo a process called epiboly. In the process of epiboly, the outer layer of cells becomes radial and starts to move towards the blastopore.
Emboly – In this process the cells of blastula which will become mesoderm and endoderm are arranged beneath a layer of cells which then becomes the ectoderm. This step involves the formation of three layers from a single layer to transform into the gastrula.
Invagination: This mechanism happens in the other part of the hemisphere i.e. vegetal pole where the exterior sheet of cells starts to move inside the blastula.

In a process of gastrulation in frog epiboly, emboly and invagination will take place.

So, the correct answer is option (D) All of the above.

Note: Gastrulation in frogs is similar to that of other animals but is quite complicated. The blastula is not empty but it is filled with the yolk cells. The gastrula formation from blastula is mainly due to the cell movement not by cell division. The cells of a single layer of blastula will move and arrange to form three layered layers.