A fish is at the surface with high water flow and a fish down with a low water flow compare the counter current flow between the fishes

8. The cell wall is the outer most covering of the cell. ... The cell membrane is present in almost all types of cells. The cell wall is present in bacteria, fungi, algae and plant cell.
9. the spreading of something more widely.
10. In facilitated diffusion, molecules only move with the aid of a protein in the membrane. In simple diffusion, molecules move down the concentration gradient but in facilitated diffusion molecules move up the concentration gradient.
11. a process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one
12. Differences: Passive Transport (or Diffusion) moves ions from high concentration to low, using no metabolic energy. Active Transport moves ions from low concentration to high, using metabolic energy in the form of ATP. ... Both use ion channels to move ions across the cell membrane, in or out of the cell