Oxygen and carbon dioxide pass across the alveolar membrane in the lungs through a process called

Oxygen and carbon dioxide pass across the alveolar membrane in the

lungs through a process called Diffusion.

Diffusion is defined as the movement of molecules from a region of higher

concentration to a lower concentration through a semi-permeable

membrane.

The alveolar membrane serves as the semi-permeable membrane in

which the oxygen and carbon dioxide pass through.

Read more about Diffusion here link

what's the rest of the question

clumped distribution, because you'de have all of the population gathered in a relatively small are.

it's the most common because it provides protection and a mate for reproduction

example: humans, seeweed, cattles, etc.