1. in terrestrial vertebrates, what is the advantaged of having the surfacesfor oxygen and carbon dioxide exchange embedded deep in lung tissue?
2.the capillaries that lie in close contact with the alveoli are branches ofwhat blood vessel?
3.the confluence of these capillaries forms what blood vessel?
4.compare blood composition in adult circulation with reference to oxygenand carbon dioxide between capillaries approaching alveoli andcapillaries leaving alveoli. the capillaries approaching the alveoli contain low oxygen and highcarbon dioxide, and the capillaries leaving the alveoli contain high oxygenand low carbon dioxide.

the oldest known insects are believed to live around 400 millions ago as suggested by the fossil records.   some plants having woody stems also evolved during this time.

after the evolution of insects the first four legged species or the tetrapods evolved in shallow freshwater habitats from the intermediate species approximately 397 million years ago. the tetrapods went on conquering the land giving rise to amphibians, reptiles, mammals and birds.

the major split in tetrapods first occurred 340 million years ago branching off from amphibians.

363 million years ago when the carboniferous period began the insects started roaming on land and taking flights, following which the four limbed tetrapods adapted in the terrestrial habitat.