Question

11. (a) What are the permanent methods of family
planning ? Write short notes on any two.
2 + 2 n
OR​

Answer 1

Explanation:

An endoskeleton is a structure that holds an animal from inside.

One can find endoskeletons in three phyla and one subclass of animals: in Chordata, Echinodermata, Porifera and Coleoidea. An endoskeleton allows the body to move and gives the body structure and shape.

A true endoskeleton develops from mesodermal tissue. Such a skeleton is present in echinoderms and chordates. The Coleoidae do not have a true endoskeleton in the evolutionary sense; here, a molluscexoskeleton developed into several sorts of internal structure, the "cuttlebone" of cuttlefish being the best-known version. An important advantage of an endoskeleton over an exoskeleton is that the endoskeleton provides more structural support. Endoskeletons hold ones insides together easily.