The air we breathe is mostly a mixture of oxygen and nitrogen. How do air molecules change when they reach altitudes above 100 km? I need to make sure the answer I have is right.

What is hydroelectric power produced by?

Consider this plant cell which organelle is labeled g

Which of the following can occur to two segments of a population if they are geographically isolated 1.) they can only share some types of genes 2.)both groups most likely become extinct 3.)they find a way to come back together 4.)eventually they become separate species