Final answer:
Things naturally move from areas of high concentration to low concentration in a process called passive transport, or diffusion. Diffusion is essential for the transport of substances such as gases and nutrients in biological systems and does not require energy, as it moves substances down the concentration gradient until equilibrium is achieved.
Step-by-step explanation:
Naturally, things move from areas of high concentration to areas of low concentration. This is called passive transport, or diffusion. Diffusion is the movement of molecules from an area of high concentration to an area of low concentration until the concentration is equal across a space.
For example, when someone opens a bottle of ammonia in a room, the ammonia gas diffuses from the higher concentration inside the bottle to the lower concentration in the room until it reaches equilibrium. This process is essential in various biological contexts, such as the movement of nutrients and gases around the body and the transport of materials within cells and across cell membranes.
The principal force driving movement in diffusion is the concentration gradient, which means materials move 'down' the gradient until an equal concentration, or equilibrium, is reached on both sides of the membrane. Diffusion is a natural and passive process that does not require energy, in contrast to active transport mechanisms that do.