Question

Gastrula is the embryonic stage in which
A. Cleavage occurs
B. Blastocoel forms
C. Germinal layers form
D. Villi form

Answer 1

Hint: Gastrula is an embryonic stage which is followed by the blastula stage of the embryo. Embryo is a ball of cells. Embryo represents an unborn or unhatched baby.

Complete Answer:
Gastrulation is a process by which embryonic stage blastula gets changed into the embryonic stage gastrula. Blastula has single layers of cells and gastrula has multilayered cells.
- During gastrulation blastula folds inwards and create three layers of cells-
1. Endoderm
2. Mesoderm
3. Ectoderm
- Organisms that do not form a third layer i.e. mesoderm are called the diploblastic animals, for example – jelly fishes.
- The organisms that form all the three layers are called triploblastic animals , for example - humans.
- These layers become germ layers. Gastrulation is followed by organogenesis (formation of organs).
- Each layer gives rise to specific tissue and organs in the developing embryo.
1. Endoderm – Endoderm gives rise to the respiratory system and digestive system.
2. Mesoderm – Mesoderm gives rise to muscles, bones and connective tissues.
3. Ectoderm – Ectoderm gives rise to the outermost layer of the body which creates the skin and nervous system.

Hence, the option C is the correct answer for this question.

Note: The animals in which embryos develop inside the body of a female are called viviparous animals (humans). The animals in which embryo development takes place outside the body of a female are called oviparous animals (birds).