Respiration

[vhpk]

I want to ask 4questions:
1/Can you show me whether 2 questions are true or false and explain:
a/ In animals, a specalized respiratory system is always linked to a circulatory system
b/ The counter-current exchange system works by maintaining the oxygen concentration gradient between the respiratory medium and the blood
2/Explain how these two processes are involved in gas exchange:
a/ dissolving b/ diffusion
3/ What are three important adaptations in the mammalian respiratory system? What advantages do these adaptations provide?
4/Among lenticel, spiracle and stoma.
a/ Which of these structures open and close?
b/ Does opening and closing serve the same purpose for the different structures?
Thanks for helping. Any help would be highly appreciated?

[vhpk]

Hix, can anyone help me

[canalon]

You? By reading your textbook, our tutorial, or asking questions showing that you are not asking us to do your homework, but that you rather have some conflicting//unclear/holey information, and that you need help to do your work by yourself.

[Ladygoth]

Try these links:
http://wiki.answers.com/

http://answers.yahoo.com/

http://en.wikipedia.org/wiki/Main_Page

Hope they help