Answer:
Facilitated Diffusion
Explanation:
Some molecules can move down their concentration gradients by crossing to the lipid portion of the membrane directly,while others must pass through membrane protein s in a process called Facilitated Diffusion
No they cant be mechanical because then something would have to generate their rays through the inventing of a machine.
4.6 million years ago the earth had less green house gasses so the atmosphere was cooler rather than hotter.
