Quotes & Sayings About Prokaryotic Cells

Throughout 150 years of the science of bacteriology, there is no evidence that one species of bacteria has changed into another ... Since there is no evidence for species changes between the simplest forms of unicellular life, it is not surprising that there is no evidence for evolution from prokaryotic [i.e., bacterial] to eukaryotic [i.e., plant and animal] cells, let alone throughout the whole array of higher multicellular organisms. — Alan H. Linton

There is no theoretical reason to expect evolutionary lineages to increase in complexity with time, and no empirical evidence that they do so. Nevertheless, eukaryotic cells are more complex than prokaryotic ones, animals and plants are more complex than protists, and so on. This increase in complexity may have been achieved as a result of a series of major evolutionary transitions. These involved changes in the way information is stored and transmitted.
[The major evolutionary transitions, Nature 374, 227 - 232 (16 March 1994)] — John Maynard Smith