The Black Death was an epidemic of bubonic plague, a disease caused by the bacterium Yersinia pestis that circulates among wild rodents where they live in great numbers and density. Such an area is called a âplague focusâ or a âplague reservoirâ.
Diffusion is the net movement of molecules or atoms from a region of high concentration to a region of low concentration.his is also referred to as the movement of a substance down a concentration gradient. A gradient is the change in the value of a quantity (e.g., concentration, pressure, temperature) with the change in another variable (usually distance).
Osmosis and diffusion are alike, as osmosis is a special kind of diffusion. Diffusion: Diffusion is the process of where a substance moves from an area of high concentration to an area of lower concentration. Diffusion doesnât need a membrane. Osmosis: Whereas, osmosis is a special kind of diffusion in which water moves through a selectively permeable membrane from an area of high concentration to an area of low concentration.