What factor is a characteristic of passive transport?

In passive transport, substances simply move from an area of higher concentration to an area of lower concentration, which does not require the input of energy. Concentration gradient, size of the particles that are diffusing, and temperature of the system affect the rate of diffusion.

It occurs without energy input. Passive transporters let something across a membrane "with the gradient" in other words, substances travel from high concentration to low concentration, which is energetically favorable.

primary succession occurs in essentially lifeless areas regions in which the soil is incapable of sustaining life as a result of such factors as lava flows, newly formed sand dunes, or rocks left from a retreating glacier. secondary succession occurs