Nitrification and denitrification are important steps in the nitrogen cycle. What is the function of these steps? A. Balancing the level of oxygen in the soil.
B. Taking the nitrogen from the air.
C. Changing the form of nitrogen as it enters and leaves the soil.
D. Pulling nitrogen from the groundwater.

a time line cause it goes from 685 to 978

answer; i believe the answer is hydraulic action;

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.