Fill up the blank spaces appropriately.                                                                          

Phylum	Excretory organ	Circulatory organ	Respiratory organ
Arthropoda	a	b	trachea
c	Nephridia	closed	skin
vertebrata	d	closed	lung

How useful is the study of the nature of body cavity and coelom in the classification of animals?

Distinguish between intracellular and extracellular digestion? 

What is the difference between direct and indirect development?

What are the peculiar features that you find in parasitic platyhelminthes?

What are the reasons that you can think of for the arthropods to constitute the largest group of the animal kingdom? 

Water vascular system is the characteristic of which group of the following: 

“All vertebrates are chordates but all chordates are not vertebrates”. Justify the statement.

How important is the presence of air bladder in Pisces?

What are the modifications that are observed in birds that help them fly?

Could the number of eggs or young ones produced by an oviparous and viviparous mother be equal? Why?