Active transport
requires energy. This is because it is going against the natural process of diffusion. Substances diffuse when their net movement is down the concentration gradient (from higher concentration to lower). Active transport is movement from lower concentration to higher. Cytosis (phagocytosis , pinocytosis) also requires energy.
Downward pull of gravity can cause materials to move from areas of high elevation to areas of low elevation. The force of gravity can cause rocks and glaciers to move down mountain slopes, and also cause rivers to flow toward the oceans. Landslides are the sudden mass erosion of rocks down a hill.
I would have to say Auroras. they occur when the suns particles get charged by the earths atmosphere
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The answer to this question is:
Scavengers
I hope this helps!
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