Explain the organisation of embryonic layers in animals.

(N/A) Animals can be classified based on the number of germinal layers present during their embryonic development:
$1$. Diploblastic Animals: Animals in which the cells are arranged in two embryonic layers, an external $ \text{ectoderm} $ and an internal $ \text{endoderm} $. An undifferentiated layer called $ \text{mesoglea} $ is present in between the $ \text{ectoderm} $ and the $ \text{endoderm} $. Examples include $ \text{Cnidarians} $.
$2$. Triploblastic Animals: Animals in which the developing embryo has a third germinal layer, the $ \text{mesoderm} $, in addition to the $ \text{ectoderm} $ and $ \text{endoderm} $. Examples include animals from $ \text{Platyhelminthes} $ to $ \text{Chordates} $.