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

1.In order to eradicate mosquitoes Housing colony members were asked to keep the surroundings dry, not to let water standing any where and cover the drainage. It was found that the strategy worked and there was decline in the number of mosquitoes.What according to you is the reason for the decline in the number of mosquitoes.?

Endoparasites are found inside the host body. Mention the special structures possessed by these to enable them to survive in those conditions.

On a morning  walk  with your friend you came across an animal which looks like a snake. But on watching it closely, your friend says it is an earthworm. What helped him in identifying it as an earthworm?                                                                                                             

What is metagenesis? Mention an example which exhibits this phenomenon.