Question

Match the germ layers.

• A. Outer germ layer
• B. Two germ layers
• C. Three germ layers
• D. Inner germ layer

Answer 1

The primary layers of tissues formed during embryonic development are called germ layers. The number of layers organised during the embryonic stage is an important criterion for the classification of animals.

• Embryonic layers are of three types. Ectoderm is the outermost germ layer. Endoderm is the innermost germ layer. Mesoderm lies in between the ectoderm and the endoderm.
• If the embryonic stage of a particular animal has only two germinal layers (ectoderm and endoderm), it is said to be diploblastic and have a radial symmetry.
• If the embryo has three germinal layers (ectoderm, mesoderm and endoderm), it is said to be triploblastic and have a bilateral symmetry.