Some cells live for years, while others live for only a few days. Why do some cells get replaced faster than others?

Some cells don't divide and last you a life time such as many of those in the central nervous system other cells such as stems called cell populations have their telemeres repeatedly extended by the enzyme telomerase other cells are never replaced and live as long as we do .

I hope this answer might help u

several tissues working together form an organ, and several organs together make up an organisms.

the group of cell that carries out special jobs are tissue.