1. The given diagrams represents the number of germ layers and body symmetry used as criteria for animal classification. 

2. Number of germ layers: 

(a) When an organism shows only two germ layers, they are called diploblastic animals. In this case, the outer ectoderm is separated from the inner endoderm by a non-living substance called mesoglea. 

(b) When an organism shows three germinal layers, they are called triploblastic animals. 

The three layers are namely – outer ectoderm, middle mesoderm and inner endoderm.

 3. Body symmetry: Body symmetry implies to the similarity in shape, size and number of parts on the opposite sides of a median line when body is divided into two halves by an imaginary line along different plane. Animals may be asymmetrical, radially symmetrical or bilaterally symmetrical.

(a) Asymmetrical animals: 

An animal is said to be asymmetrical when its body cannot be divided into two identical halves in any plane. 

(b) Radially symmetrical animals: In certain animals, body can be cut or divided into two similar halves in a number of planes wherein, all the cuts (planes) pass through the centre. This type of symmetry is called radial symmetry. 

(c) Bilaterally symmetrical animals:

In this type, the body of the animal can be bisected or divided in two equal or identical halves by a single median or vertical plane.