(1) The respiratory surface is both are highly extensible.(2) The respiratory surface is fully permiable.(3) The respiratory organs are richly supplied with blood for complete diffusion.(4) Both the organs are highly protected
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Some common features are as follows:
1)All animal's respiratory organs are supplied with numerous no. of blood vessels.This help in the exchange of gases.
2)Are extensible so that right amount of air can be filled to fulfill the gaseous exchange.
3)Are usually sac-like structure.
4)Usually soft and delicate.
5)Contains villi to increase the surface area.

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