During diffusion molecules tend to move a. up the concentration gradient b. down the concentration gradient c. from an area of lower concentration to an area of higher concentration d. in a direction that doesn’t depend on concentration

Which of the following is likely not involved in this example of ecological succession? a) the rotting remains of plants add to the fertility of the soil. b)the soil becomes so fertile that eel grass is replaced by other plant species. c) the roots from plants stabilize the sediment, keeping it in place. d) the concentration of salt becomes so high that all plant life is destroyed.