Started by Smartmarzipan, September 11, 2013, 03:21:05 PM
Quote from: "Eric1958"I've taken college classes that I have put less work into than reading through this thread. Is there a test?
Quote from: "AllPurposeAtheist"I gotta tell you.. very few, if ANY of the religious nitwits I know would bother reading much past: see evolution sticky note..God would certainly render them blind and they automatically qualify for the government dole..Sorry to be such a stick in the mud. :)
QuoteThe E. coli long-term evolution experiment is an ongoing study in experimental evolution led by Richard Lenski that has been tracking genetic changes in 12 initially identical populations of asexual Escherichia coli bacteria since 24 February 1988. The populations reached the milestone of 50,000 generations in February 2010.Since the experiment's inception, Lenski and his colleagues have reported a wide array of genetic changes; some evolutionary adaptations have occurred in all 12 populations, while others have only appeared in one or a few populations. One particularly striking adaption was the evolution of a strain of E. coli that was able to use citric acid as a carbon source in an aerobic environment.
QuoteIn 2008, Lenski and his collaborators reported on a particularly important adaptation that occurred in the population called Ara-3: the bacteria evolved the ability to grow on citrate under the oxygen-rich conditions of the experiment. Wild-type E. coli cannot grow on citrate when oxygen is present due to the inability during aerobic metabolism to produce an appropriate transporter protein that can bring citrate into the cell, where it could be metabolized via the citric acid cycle. The consequent lack of growth on citrate under oxic conditions, referred to as a Cit- phenotype, is considered a defining characteristic of the species that has been a valuable means of differentiating E. coli from pathogenic Salmonella. Around generation 33,127, the experimenters noticed a dramatically expanded population-size in one of the samples; they found clones in this population could grow on the citrate included in the growth medium to permit iron acquisition. Examination of samples of the population frozen at earlier time points led to the discovery that a citrate-using variant (Cit+) had evolved in the population at some point between generations 31,000 and 31,500.
QuoteAbiogenesis, or biopoiesis, is a natural process by which life arises from simple organic compounds. The earliest life on Earth existed at least 3.5 billion years ago, during the Eoarchean Era when sufficient crust had solidified following the molten Hadean Eon.Scientific hypotheses about the origins of life may be divided into a number of categories. Many approaches investigate how self-replicating molecules or their components came into existence. For example, the Millerï¿½Urey experiment and similar experiments demonstrated that most amino acids, often called "the building blocks of life", can be racemically synthesized in conditions thought to be similar to those of the early Earth. Several mechanisms have been investigated, including lightning and radiation. Other approaches ("metabolism first" hypotheses) focus on understanding how catalysis in chemical systems in the early Earth might have provided the precursor molecules necessary for self-replication.
QuoteThere is no "standard model" of the origin of life. Most currently accepted models draw at least some elements from the framework laid out by the Oparin-Haldane hypothesis. Under that umbrella, however, are a wide array of disparate discoveries and conjectures such as the following, listed in a rough order of postulated emergence:The Oparin-Haldane hypothesis suggests that the atmosphere of the early Earth may have been chemically reducing in nature, composed primarily of methane (CH4), ammonia (NH3), water (H2O), hydrogen sulfide (H2S), carbon dioxide (CO2) or carbon monoxide (CO), and phosphate (PO43-), with molecular oxygen (O2) and ozone (O3) either rare or absent.In such a reducing atmosphere, electrical activity can catalyze the creation of certain basic small molecules (monomers) of life, such as amino acids. This was demonstrated in the Millerï¿½Urey experiment by Stanley L. Miller and Harold C. Urey in 1953.Phospholipids (of an appropriate length) can form lipid bilayers, a basic component of the cell membrane.A fundamental question is about the nature of the first self-replicating molecule. Since replication is accomplished in modern cells through the cooperative action of proteins and nucleic acids, the major schools of thought about how the process originated can be broadly classified as "proteins first" and "nucleic acids first".The principal thrust of the "nucleic acids first" argument is as follows:The polymerization of nucleotides into random RNA molecules might have resulted in self-replicating ribozymes (RNA world hypothesis)Selection pressures for catalytic efficiency and diversity might have resulted in ribozymes which catalyse peptidyl transfer (hence formation of small proteins), since oligopeptides complex with RNA to form better catalysts. The first ribosome might have been created by such a process, resulting in more prevalent protein synthesis.Synthesized proteins might then outcompete ribozymes in catalytic ability, and therefore become the dominant biopolymer, relegating nucleic acids to their modern use, predominantly as a carrier of genomic information.No one has yet synthesized a "protocell" using basic components which would have the necessary properties of life (the so-called "bottom-up-approach"). Without such a proof-of-principle, explanations have tended to be focused on chemosynthesis of polymers. However, some researchers are working in this field, notably Steen Rasmussen at Los Alamos National Laboratory and Jack Szostak at Harvard University. Others have argued that a "top-down approach" is more feasible. One such approach, successfully attempted by Craig Venter and others at The Institute for Genomic Research, involves engineering existing prokaryotic cells with progressively fewer genes, attempting to discern at which point the most minimal requirements for life were reached. The biologist John Desmond Bernal coined the term biopoiesis for this process, and suggested that there were a number of clearly defined "stages" that could be recognised in explaining the origin of life.Stage 1: The origin of biological monomersStage 2: The origin of biological polymersStage 3: The evolution from molecules to cellBernal suggested that evolution commenced between Stage 1 and 2.
QuoteCertain creationists correctly point out that abiogenesis must have taken place at some point to begin the process of evolution. They then attempt to use this premise to "disprove" evolution, claiming that Louis Pasteur had conclusively refuted it. However, he only showed that it is not a typical present-day occurrence even for the simplest of free-living organisms.Creationists also like to rebut abiogenesis by pointing out seeming prebiotic environments where it does not happen, like in their Peanut Butter Argument. However, the most suitable environment has been the subject of active research, like that of Gï¿½nter Wï¿½chtershï¿½user with his hypothesis of an iron-sulfur world of hydrothermal vents.Another creationist statement often made is that evolution is abiogenesis; this is simply ignorance of scientific terminology. Evolution is the gradual change of organisms over time, whereas abiogenesis is the start of life itself. The creationists may also be projecting their belief in separate creations onto mainstream biologists.Yet more creationist illogic is, "Scientists can't explain the origin of life, therefore it must have been God and specifically the God I believe in."
QuoteA hydrothermal vent, also called a "black smoker", is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, tectonic plates that are moving apart, ocean basins, and hotspots.Hydrothermal vents are abundant on Earth because it is both geologically active and has large amounts of water on its surface. Common land types include hot springs, fumaroles and geysers. The most famous hydrothermal vent system is probably Yellowstone National Park in the United States.Relative to the majority of the deep sea, the areas around hydrothermal vents are biologically productive, often hosting complex communities fueled by the chemicals dissolved in the vent fluids. Chemosynthetic archaea form the base of the food chain, supporting diverse organisms, including giant tube worms, clams, and shrimp.
QuoteThere are many different theories about where the origin of life occurred. These theories range from life beginning in deep sea thermal vents to bacterial life arriving from other places in the universe, among others. Some of these theories are more credible than others, yet all provide an interesting explanation for life's beginnings.Significance of WaterEveryone knows that liquid water is essential for humans to survive. In fact, it is essential in the chemistry of all biological systems. Water provides the medium in which the transport of molecules can occur in reactions. Because water is necessary for all life, scientists look for evidence of liquid water wherever they search for life, whether it is somewhere on Earth, or even somewhere else in our solar system or beyond. In fact, astronomers are currently examining the satellites of Jupiter, Europa and Ganymeade, and Titan, one of Saturn's satellites, to see if they contain liquid water and the conditions which may give rise to life as we know it.Before we look to see where life may have begun elsewhere in the universe, let's look at where, or how, life might have begun on the earth.Thermal VentsOne current theory is that life originated deep beneath the surface of the ocean at deep sea hydrothermal vents. These hydrothermal vents were first discovered in 1979. Soon after, scientists made an exciting discovery. These vents release hot gaseous substances from the center of the earth at temperatures in excess of 572oF. Previously scientists were sure that life could not exist, deep beneath the surface of the ocean. After the discovery of hydrothermal vents, they found ecosystems thriving in the depths of the ocean. These ecosystems contained various types of fish, worms, crabs, bacteria and other organisms which had found a way to survive in a cold, hostile environment without energy input from sunlight. Because life had been found to exist where it previously was thought unable to, many scientists began to ask questions as to whether or not this was where life may have originated on the earth.On the molecular level, the chances of life originating at deep sea thermal vents is not likely. It is known that organic molecules are unstable at high temperatures, and are destroyed as quickly as they are produced. It has been estimated that life could not have arisen in the ocean unless the temperature was less than 25oC, or 77oF.Supporters of this theory claim that the organic molecules at the thermal vents are not formed in 300oC temperatures, but rather in a gradient formed between the hydrothermal vent water, and the extremely cold water, 4oC (39.2oF), which surrounds the vent at the bottom of the ocean.The temperatures at this gradient would be suitable for organic chemistry to occur. Debates still remain, however, as to the gradient's effectiveness in producing organic compounds.
Quote from: "Hydra009"Evolution of novel traits: e. coli evolve to metabolize citrate
Quote from: "Smartmarzipan"What is Abiogenesis?
Quote from: "Colanth"Quote from: "Smartmarzipan"What is Abiogenesis?Anyone save the link to the youtube video showing how abiogenesis could have occurred? (It was posted on the forum not too long ago.) It definitely belongs here.
Quote from: "Brian37"Um all this detail means something to those who already accept it.I'd argue to Creationists who seem to be bloodthirsty vengeful people if they sat on a jury of a murder trial, would they accept DNA evidence to convict the accused. I'd bet my life that most of them would accept DNA evidence in a trial.I'd simply point out to these morons that they cant cherry pick science because DNA BACKS UP EVOLUTION. So if they deny evolution, then they should discount any DNA evidence in a murder trial when sitting on a jury.They use and love what science produces, but spit on it all the time.
Quote from: "AllPurposeAtheist"Science has been horifically destructive as well as beneficial to everyone. I view it more neutral. It's not like the football team the Scientist vs the Creationists.GOOOO TEAM! :)