Single celled organisms are made up of one cell, often microscopic and limited in size, able to meet all challenges of life with in one cell, and are able to differentiate to perform a specific job.
Explanation:
Singled celled organisms are usually, as the name suggests, single celled. To see one, you must use a microscope, and usually range anywhere from 0.5 to 10cm tall. A single celled organism can preform the necessary functions for life. They can eat, breathe, grow, and do other things other organisms with more than one cell.
Facilitated diffusion is a diffusion mechanism facilitated by membrane transporters. it's the spontaneous passage of molecules or ions (like the passive diffusion) through a biological membrane through transport molecules (unlike passive diffusion). This process does not consume energy (like the passive diffusion) and therefore does not involve active transportation.
Unlike the gain or loss of member through immigration, emigration, or death, the age of a population's members does not effect population size, meaning the correct answer is D.
