Cells divide for many reasons. For example, when you skin your knee, cells divide to replace old, dead, or damaged cells. ... When organisms grow, it isn't because cells are getting larger. Organisms grow because cells are dividing to produce more and more cells.
Cells in an organism go through division all the time. One reason is for growth. As an organism grows, more cells are created. Cells divide instead of grow because there is an optimal size for cell. So it is more efficient to create new cells.
Second reason for cell division is to repair damaged cells. Some cells like skin cells are damaged routinely and cell division is the way to repair and replace damaged cells.
Last reason is for reproduction. All organisms use cell division to reproduce.
Fossils, or preserved parts of organisms from the distant past, have shown that species change over time. Radiometric dating can be used to determine the age of fossils by measuring the how much of the radioactive materials in each rock layer have broken down.
