Eu-karotes and pro-karyotesEukaryotes (meaning true kernel, also spelled "eucaryotes") covers all species that have a true nuclei within their cells, containing their DNA, while Pro-karyotes' covers micro-organisms with cell-material where the genetic material is not membrane-bound. Eukaryotes are organisms that have cell nuclei and may be variously unicellular or multicellular and thus termed "plants" or "animals". The difference between the structure of prokaryotes and eukaryotes is so great that it is considered to be the most important distinction among groups of organisms. Most pro-karyotes are
bacteria, and the two terms are often treated as synonyms.
In 1977, Carl Woese proposed dividing prokaryotes into the Bacteria and Archaea (originally Eubacteria and Archaebacteria) because of the significant genetic differences between the two. This arrangement of Eukaryota (also called "Eukarya"), Bacteria, and Archaea is called the three-domain system replacing the traditional two-empire system.
Evolution of PolycarotesProkaryotes are found in nearly all environments on earth. Archaea in particular seem to thrive in harsh conditions, such as high temperatures or salinity. Organisms such as these are referred to as extremophiles. Many prokaryotes live in or on the bodies of other organisms, including humans.
It is generally accepted that the
first living cells were some form of prokaryote and may have developed out of protobionts.
http://en.wikipedia.org/wiki/Origin_of_life
Fossilized prokaryotes approximately 3.5 billion years old have been discovered, and prokaryotes are perhaps the most successful and abundant organism even today. In contrast the eukaryote only appeared between approximately 1.7 and 2.2 billion years ago.[1] While Earth is the only known place where prokaryotes exist, some have suggested structures within a Martian meteorite should be interpreted as fossil prokaryotes;
this is open to considerable debate and skepticism.
Prokaryotes diversified greatly throughout their long existence. The metabolism of prokaryotes is far more varied than that of eukaryotes, leading to many highly distinct types of prokaryotes. For example, in addition to using photosynthesis or organic compounds for energy like eukaryotes do, prokaryotes may obtain energy from inorganic chemicals such as hydrogen sulfide.
This has enabled the bacteria to thrive and reproduce. Today, archaebacteria can be found in the cold of Antarctica and in the hot Yellowstone springs.
The sizes of prokaryotes relative to other organisms and biomolecules.http://en.wikipedia.org/wiki/Prokaryote