Learn more about the extinction that occurred at the end of the paleozoic era. describe how life was effected and the theory behind the extinction.

the answer is "a.) well–developed vascular system."

explanation:

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.