Question

Why are there so many alveoli in the lungs?

Answer 1

To increase the surface area to volume ratio, therefore maximising the effectiveness of gas exchange in the lungs.

Explanation:

Gas exchange occurs rapidly and continuously in our lungs. Alveoli are tiny sacs at the end of bronchioles, the reason they are so tiny yet abundant is to increase their surface area to volume ratio.
This ratio is extremely crucial to any organism's survival.

A larger surface area to volume ratio means there is more surface area to one unit of volume.

Gas exchange is when the oxygen gas in the air we breathe in is absorbed through diffusion into our blood stream via the blood vessels in the alveoli. This occurs on the surface of the alveoli, therefore the more surface area there is, the more oxygen gas get taken up and used in our body (without taking up so much space in our body because the alveoli are so small).

Hope that helped anyone :)