Name the five classes of vertebrates. Compare any two on the basis of their $(i)$ Habitat,$(ii)$ Covering of skin,$(iii)$ Respiratory organs,$(iv)$ Chambers of heart,and $(v)$ Reproduction.

State reasons for the following:
$(a)$ Protists have appendages like cilia or flagella.
$(b)$ Angiosperms are called so.
$(c)$ Fish have scales on their body.

Echinoderms have a system that they use for moving around. Name the system. What is their skeleton made-up of?

Charles Darwin first described the idea of evolution in his book "The Origin of Species". Define the concept of evolution.

$(a)$ Associate any three phyla of Animalia with triploblastic body organisation and bilateral symmetry.
$(b)$ State the meaning of triploblastic body organisation and bilateral symmetry.
$(c)$ On the basis of presence or absence of coelom,compare the three phyla answered in $(a)$.

Label $X$ and $Y$ in the given diagram of Hydra.