Which form of cell transport allows small molecules to move from an area of higher concentration to an area of lower concentration without energy being required from the cell?

Veins have a much lower blood pressure than arteries. which of these prevents backflow of blood in veins? a. pressure applied by the heart b. one–way valves in veins c. thin muscular walls of veins

Eutrophication caused by human nutrient pollution.

Cloning an individual usually produces orangisms that (1) contain dangerous mutations (2) contain identical genes (3) are identical in appearance and behavior (4) produce enzymes different from the parent