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).
Simple diffusion allows non-polar molecules to pass through and a little amount of H20. On the other hand, Facilitated diffusion allows ions and polar molecules across the mem â¦ brane because it contains carrier proteins. It is highly specific to substances it diffuses across the membrane.acilitated Diffusion is the movement of molecules across cell membranes through protein channels and carrier proteins.