BIOL 1002 Chapter : Bio 1002 Chapter 19
Document Summary
The organisms that make up the two prokaryotic domains (bacteria and achaea) were the first organism to arise on earth (about 3. 5 billion years ago). While only about 5000 prokaryotic species have been describe, there may be as many as 100-1000 time that number. 0. Prokaryotes range in size from 0. 2-1. 0 micrometers in diameter (see fig 19-10) How big (or small) is a micrometer 1,000,000 of a meter. The thickness of a dime is about 1 millimeter (1000 micrometers). The two domains appear similar in many respects however they are different in some very basic ways. One main distinction between the bacteria and the achaea is the type of a semi-rigid permeable cell wall. The bacteria cell wall is composed of peptidoglycan. Peptidoglycan is a complex of structural polysaccharides cross-linked by peptides. The cell wall of a bacteria gives it the different types of characteristics shapes (19-1)
