As my game shop is quiet now...enable to post
Iron-sulfur world theoryhttp://en.wikipedia.org/wiki/Iron-sulfur_world_theoryThe iron-sulfur world theory is a hypothesis for the origin of life advanced by Günter Wächtershäuser, a Munich chemist and patent lawyer, involving forms of iron and sulfur [1] . Wächtershäuser proposes that an early form of metabolism predated genetics. Metabolism here means a cycle of chemical reactions that produce energy in a form that can be harnessed by other processes. The idea is that once a primitive metabolic cycle was established,
it began to produce ever more complex compounds. A key idea of the theory is that this early chemistry of life occurred not in bulk solution in the oceans, but on mineral surfaces (e.g. iron pyrites) near deep hydrothermal vents. This was an anaerobic, high-temperature (near 100°C), high-pressure environment.
The first 'cells' would have been lipid bubbles on the mineral surfaces. Wächtershäuser has hypothesized a special role for acetic acid, a simple combination of carbon, hydrogen, and oxygen found in vinegar. Acetic acid is part of the citric acid cycle that is fundamental to metabolism in cells. Proto-Ecological SystemsWilliam Martin and Michael Russell reported a modified iron-sulfur-hypothesis in 2002.[4]
According to their scenario, the first cellular life forms may have evolved inside so-called black smokers at seafloor spreading zones in the deep sea. These structures consist of microscale caverns that are coated by thin membraneous metal sulfide walls. Therefore, these structures would solve several critical points of the "pure" Wächtershäuser systems at once:the micro-caverns provide a means of concentrating newly synthesised molecules, thereby increasing the chance of forming oligomers;
the steep temperature gradients inside a black smoker allow for establishing "optimum zones" of partial reactions in different regions of the black smoker (e.g. monomer synthesis in the hotter, oligomerisation in the colder parts);
the flow of hydrothermal water through the structure provides a constant source of building blocks and energy (freshly precipitated metal sulfides);
the model allows for a succession of different steps of cellular evolution (prebiotic chemistry, monomer and oligomer synthesis, peptide and protein synthesis, RNA world, ribonucleoprotein assembly and DNA world) in a single structure, facilitating exchange between all developmental stages;
synthesis of lipids as a means of "closing" the cells against the environment is not necessary, until basically all cellular functions are developed.
Some of the fundamental ideas of the iron-sulfur theory can be summarized in the following brief recipe for life: Boil water. Stir in iron sulfide and nickel sulfide. Bubble in carbon monoxide and hydrogen sulfide gas. Wait for peptides to form.More technically, Wächtershäuser hypothesized the following steps for producing proteins:
Produce acetic acid through metallic ion catalysis.
Add carbon to the acetic acid molecule to produce three-carbon pyruvic acid.
Add ammonia to form amino acids.
Produce peptides and then proteins.
Both acetic acid and pyruvic acid are key chemicals in the citric acid cycle.
In 1997, Wächtershäuser and Claudia Huber mixed carbon monoxide, hydrogen sulfide, nickel sulfide, and iron sulfide particles at 100°C and demonstrated that amino acids could form.[2] The following year, using the same ingredients, they were able to produce peptides.[3]http://www.pbs.org/wgbh/evolution/library/faq/cat02.html5 to 8 million years ago. Shortly thereafter, the species diverged into two separate lineages. One of these lineages ultimately evolved into gorillas and chimps, and the other evolved into early human ancestors called hominids.3. Does evolution stop once a species has become a species?Evolution does not stop once a species becomes a species. Every population of living organisms is undergoing some sort of evolution, though the degree and speed of the process varies greatly from one group to another. Populations that experience a major change in environmental conditions, whether that change comes in the form of a new predator or a new island to disperse to, evolve much more quickly than do populations in a more stable set of conditions.
This is because evolution is driven by natural selection, and because when the environment changes, selective pressures change, favoring one portion of the population more heavily than it was favored before the change.