Amphibians do not have which of the following?

Name two mammals which lay eggs. Between which two phyla do they serve as connecting link? Name a mammal which gives birth to poorly developed young ones.

Hard calcium carbonate structures are used as a skeleton by

The locomotory organs of $Echinodermata$ are:

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

$(a)$ 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 $(a)$.