Question

-Compare and contrast the function of the notochord in cephalochordates, urochordates and vertebrates.In each group of animals, is the notochord present throughout their lifespan?

-Explain why monotremes are considered mammals.What are the key differences between monotremes and other mammals?

Answer 1

Ans) In urochordata Notochord is present only on posterior part of body and its function is to support the body. While in cephalochordata notochord is extended in the head region where also it supports body and may transmit some signals laterally. In urochordata notochord only in larval stage, in cephalochordata throughout life while in vertebrates it is replaced by vertebral column. In vertebrates the main function of notochord is support and it disappears and developes to vertebral column which is supporting structure for spinal cord.

Ans) Monotremes have a single bone in their lower jaw, three middle ear bones, high metabolic rates, hair, and they produce milk to nourish the young so they can be related to mammals. But unlike mammals they are very primitive and lay eggs.