Question

.Choose the correct underlying process of the following
Zygote_____(i)______ Morula ______(ii)______Blastula ______(iii)________ Gastrula.

• A. (i) Cleavage (ii) Blastulation (iii) Gastrulation
  
• B. (i) Blastulation (ii) Cleavage (iii) Gastrulation
• C. (i) Cleavage (ii) Gastrula (iii) Blastula
  
• D. (i) Blastulation (ii) Cleavage (iii) Gastrulation
  

Answer 1

The correct option is A (i) Cleavage (ii) Blastulation (iii) Gastrulation


Zyygote is formed as a result of fusion between the male and female gametes. Zygote undergoes mitotic division called cleavage.
Cleavage starts at the animal pole and proceeds towards the vegetal pole. The repeated division results in a 8-16 celled stage called morula.
These cells of morula (blastomeres) continue to divide and increase the number of cells inside the definite cytoplasmic mass of the zygote. It continues to increase its numbers by division and finally a hollow ball of cells called the blastula forms. The process of formation of the blastula is called blastulation.
Next, invagination of the cells on one side of the blastula develops a hollow centre within the embryo that becomes the gut or archenteron later. This stage of the embryonic development is called gastrula and the process is called gastrulation.
Figure: Human embryonic development