Answer:
get pollen from one flower to another
This exchange process takes place in the aveolus (air sac) inside your lungs by diffusion.
it's from a different concentration gradient
the deoxygenated blood with carbon dioxide diffuse into a aveoli (which is in high concentration) and the aveoli release the oxygen into the blood stream (which is low concentration) therefore the blood will be oxygenated again
They help an environment because they create an ecosystem allowing animals to thrive and live a lifecycle with the resources they need.