The answer is concentration gradient. Have a good day.
Answer: Cows put in a pasture of fresh grass will eat it down too a point it would regrow fast.. Unless the pasture is not large enough for the number of cattle. Then they will eat it into the ground and kill it.
Explanation:
You see, passive transport needs no energy. So that being said, it moves from areas with high concentration to areas with low concentration.
Hope that helps!