In which of the following organisms is metamerism (segmentation) observed?

The term "phylum" in animal classification was coined by

Select the correct match for Column $X$ and Column $Y$:

Column $X$	Column $Y$
$(1)$ Aves	$(A)$ Endoskeleton made of cartilage
$(2)$ Amphibia	$(B)$ Left aortic arch
$(3)$ Chondrichthyes	$(C)$ First homeothermic animals
$(4)$ Mammalia	$(D)$ Metamorphosis

Which of the following is observed in the adult stage of $Cnidaria$ and $Echinodermata$?

Choose the group of parasitic animals.

Give an example of the following:
$(a)$ $A$ viviparous animal
$(b)$ $A$ fish possessing a poison sting
$(c)$ $A$ fish possessing an electric organ
$(d)$ An organ which regulates buoyancy
$(e)$ An animal which exhibits alternation of generation
$(f)$ An oviparous animal with mammary glands