Monday, March 30, 2009
Archaea vs. Bacteria
Tom Brock found what he thought to be another kind of bacteria living in the hot springs of Yellowstone National Park. However, further analysis revealed that these oragnisms were actually as different from bacteria as eukaryotes. We now call these organisms Archaea. Using your understanding of the diversity of life, compare and contrast the two traits of bacteria and archaea (preferably one compare, one contrast), how these are selective advantages, and how these difference might have arisen.
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Comparison: Both Archaea and Bacteria have circular chromosomes "...The mass of fibers is actually the prokaryotic chromosome, one double-stranded DNA molecule in the form of a ring," (Campbell 531). The selective advantage to having circular chromosomes is that it provides a lower chance for errors by polymerases and it allows for the swift copying of the genetic material. With such celerity, Archaea and Bacteria would be able to replicate quickly and colonize a certain microclimate. Both Archaea and Bacteria have heritable information and through the copying of the chromosome, there is a connection to Biological Theme 3: Heritable Information.
ReplyDeleteContrast: (Some) Archaea have the ability to survive/reproduce in extreme conditions while Bacteria cannot. Methanogens are Archaea "named for the unique way they obtain energy by using CO2 to oxidize H2, producing methane (CH4) as a waste product. Methanogens, among the strictest of anaerobes, are poisoned by oxygen," (Campbell 536). The selective advantage for Archaea is that they can inhabit the "anaerobic environment" of animals (within their guts) by having a symbiotic (mutualistic) relationship with the animals. The Archaea are protected from predation and are provided for with CO2 and H2. The difference may have arisen when the earliest prokaryotes evolved - when they inhabited "extreme" environments such as deep-sea hydrothermal vents. Such prokaryotes retained their extremophilic properties while other prokaryotes did not. Both Archaea and Bacteria are composed of cells (in this case prokaryotic cells) as compared to eukaryotic cells, in relation to Biological Theme 2: The Cell.
Comparison: Both archaea bacteria and eubacteria generally have pili, which are hairlike appendage found on the surface of the bacteria that used during conjugation, a process through which bacteria can share/transfer genetic material. Conjugation via the pilus a highly useful selective advantage because it allows for the rapid transfer of useful genetic material across multiple bacteria. For example, genetic material that produces a beneficial thicker cell wall can be transfered from one bacteria to another, without need to wait until the original bacteria reproduces. Essentially, the process of natural selection is enhanced by conjugation via the pilus.
ReplyDeleteContrast: Archaea bacteria have histones (and hence nucleosomes), while eubacteria lack histones. The existence of histones in archaea allow for the increased condensing of genetic material in the cell, which leaves more room for more genetic material. More genetic material can provide further selective advantages to archea bacteria, better equipping them against their harsh and extreme environment.
Both archaea and bacteria are able to reproduce asexually via binary fission. They are able to undergo binary fission because they lack membrane bound organelles which makes them fairly simple organism. Binary fission is where the prokaryote divides and the daughter cell will have the same chromosome as the parent. This is a selective advantage for archaea and bacteria because they do not have to come in contact with another organism of their species. Because these organisms are so small it is fairly rare for them to meet, therefore sexual reproduction would cause them to go extinct.
ReplyDeleteBacteria have multiple types or RNA polymerase and archaea only have one RNA polymerase. Although archaea only have one RNA polymerase, it is similar to the ancestor of the eukaryotic polymerases.