According to the theory, a population may go long periods of genetic stability, interspersed with short periods of extreme evolutionary change

This theory is called punctuated equilibrium. In this theory it is explained that there are very long periods of no change at all to a species, yet there are also bursts of evolutionary change interspersed within the time period. The period of remaining the same throughout time (most of the time) is called stasis, and is present within this theory of punctuated equilibrium.

Centriole.centrioles are present in animal cells but are usually absent in plant cells.