How do pioneer species help in establishing the next type of vegetation?

Name the pioneer species on a bare rock. How do they help in establishing the next type of vegetation. Mention the types of climax community that will ultimately get established.

How rainfall determines the kind of vegetation?

How do muscles help in movement of bones ?

How do biomembrances help in cellular movements?

How do leydig's cells help in spermatogenesis?

How do plants and animnals help each other in the exchange of gases in the atmosphere ?