Question

Describe the criteria for classification considering the number of Germinal layers.

Answer 1

The germinal layer of cells is a primary layer of cells that are formed during embryogenesis. There are three germinal layers:

• Ectoderm
• Mesoderm
• Endoderm

These germ layers differentiate into animal embryos at the gastrulation stage and later, different tissues and organs are formed from these layers. On the basis of germ layers, animals are classified as diploblastic and triploblastic.

• Diploblastic body plan is the simplest organisation at the tissue level. The outer layer ectoderm forms the epidermis and the inner layer endoderm forms the internal structures. A non-cellular gel-like matrix may be present between ectoderm and endoderm which is called mesoglea.
• Triploblastic animals develop from a three-layered embryo. Besides ectoderm and endoderm, such animals have an extra middle layer called mesoderm.