Organ systems of the human body interact to maintain a balanced internal environment. as blood flows through certain organs of the body, the composition of the blood changes because of interactions with those organs. state one change in the composition of the blood as it flows throug the respiratory system.

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.

i think the answer is a.keratin is the pigment responsible for skin color.