Of the following choices, which would require the cell to expend energy to move it across the membrane?
water
oxygen
carbon dioxide
protein

Which of the following is not a symptom of desertification? a) decrease in salt content of the soil b) lowering of the water table c) reduced surface water d) increased soil erosion e) loss of native vegetation

Which of the following is a true statements about viruses? viruses have no nucleus. viruses are alive. viruses have a cell membrane. all viruses are deadly.

Which organism in this food web is an omnivore?coati