Why is it necessary for cells to use up valuable energy to transport materials across a membrane, il diffusion occurs naturally ?

Cell specialization occurs by the process ofa. reproductionb. differentiationc. maturationd. growth

When analyzing tree rings, what do scientists assume a thin ring indicates?

Which statement is the best summary of the model? a-a series of aerobic and anaerobic reactions take place in cells b- the sun's energy moves through trophic levels in a food chain c-light energy is converted into stored chemical energy plants.d- food molecules are broken down in the cells if living things.