Chapter 27
1. Theyre
(almost) everywhere! An overview of prokaryotic life
2. Bacteria
and archaea are the two main branches of prokaryote
evolution1
3.
Prokaryotes were the earliest organisms on Earth
and evolved alone for 1.5 billion years.
Today, prokaryotes still dominate the
biosphere.
Their collective biomass outweighs all
eukaryotes combined by at least tenfold.
More prokaryotes inhabit a handful of fertile
soil or the mouth or skin of a human than the total number of people who have
ever lived.
Modern prokaryotes are diverse in structure
and in metabolism.
About 5,000 species of prokaryotes are known,
but estimates of actual prokaryotic diversity range from about 400,000 to 4
million species
4. Nearly
all prokaryotes have a cell wall external to the plasma membrane
5. Many
prokaryotes are motile
6. The
cellular and genomic organization of prokaryotes is fundamentally different
from that of eukaryotes
7. Populations of prokaryotes grow and adapt
rapidly
8. Prokaryotes
can be grouped into four categories according to how they obtain energy and
carbon
9. Photosynthesis
evolved early in prokaryotic life
10. Molecular systematics is leading to a phylogenetic
classification of prokaryotes
11. Researchers
are identifying a great diversity of archaea in
extreme environments and in the oceans
12. Most known prokaryotes are bacteria
13. Prokaryotes
are indispensable links in the recycling of chemical elements in ecosystems
14. Many
prokaryotes are symbiotic
15. Pathogenic prokaryotes cause many human
diseases
16. Humans use
prokaryotes in research and technology
Additional Notes