I did not and apologies for the late response… I seem to never see these messages.
For those curious, Lynn Marguilis ”is best known for her theory on the origin of eukaryotic organelles and her contributions to endosymbiotic theory, which is now generally accepted fr how certain organelles were formed.”
ScienceDaily (Feb. 21, 2012) — Atmospheric oxygen really took off on our planet about 2.4 billion years ago during the Great Oxygenation Event. At this key juncture of our planet’s evolution, species had either to learn to cope with this poison that was produced by photosynthesizing cyanobacteria or they went extinct. It now seems strange to think that the gas that sustains much of modern life had such a distasteful beginning.
ScienceDaily (Jan. 24, 2012) — Organic chemists at the University of York have made a significant advance towards establishing the origin of the carbohydrates (sugars) that form the building blocks of life.
A team led by Dr Paul Clarke in the Department of Chemistry at York has re-created a process which could have occurred in the prebiotic world.
Working with colleagues at the University of Nottingham, they have made the first step towards showing how simple sugars — threose and erythrose — developed. The research is published in Organic & Biomolecular Chemistry.
The Khan Academy discusses Embryonic Stem Cells
“If you are against research that involves embryonic stell cells because of the destruction of embryos, on those same philosophical grounds, you should also be against in vitro fertilization because both of these involve the destruction of zygotes.”
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This is more developmental biology than ecology and evolution, but delves into the politics/philosophy surrounding current research and the forces both for and against it. It is wholly important to have a firm understanding of the science behind these issues before forming an opinion. Also, if you do not already know about the Khan Academy, check it out!
From Wikipedia, the free encyclopedia
Dollo’s law of irreversibility (also known as Dollo’s law and Dollo’s principle) is a hypothesis proposed in 1893[1] by French-born Belgian paleontologist Louis Dollo which states that evolution is not reversible. This hypothesis was first stated by Dollo in this way: “An organism is unable to return, even partially, to a previous stage already realized in the ranks of its ancestors.”[2] According to this hypothesis a structure or organ that has been lost or discarded through the process of evolution will not reappear in exactly the same form in that line of organisms.[3][4] According to Richard Dawkins, the law is “really just a statement about the statistical improbability of following exactly the same evolutionary trajectory twice (or, indeed, any particular trajectory), in either direction.”[5]Stephen Gould viewed the idea less strictly, suggesting that “irreversibility” forecloses certain evolutionary pathways once broad forms have emerged: “[For example], once you adopt the ordinary body plan of a reptile, hundreds of options are forever closed, and future possibilities must unfold within the limits of inherited design.”[6] It is readily observed that many taxa of gastropods have reduced shells, and some gastropods have even lost the coiling of their shell during the evolutionary process.[8] According to Gould’s interpretation of Dollo’s law, it would not be possible to re-gain a coiled shell after the coiling has been lost. Nevertheless, a few genera in the family Calyptraeidae may have changed their developmental timing (heterochrony) and gained back (re-evolution) a coiled shell from an uncoiled limpet-like shell.[8][9] Other exceptions to this law include the wings of stick insects,[10] the larval stages ofsalamanders,[10][11] lost toes in lizards,[12][13] and clavicles in non-avian theropod dinosaurs.[14] Also, a recent study on the evolution of the mandibular teeth of the frog Gastrotheca guentheri proposed its teeth have re-evolved using genetic structures already present, instead of re-evolving a whole new tooth blueprint.[15][16] Dr. John Wiens, who teaches in the Department of Ecology and Evolution at Stony Brook University, N.Y., studied the jaws of modern tree frogs for several years and compared them to fossils and DNA of over 170 amphibian species. He found that Gastrotheca guentheri, a species of tree frog native to Colombia and Ecuador, grew back teeth that had been “evolved away” millions of years ago.[17] The evolution of the peppered moth over the past 250 years also gives one pause when considering Dollo’s Law.
A recent study on the evolution of protein structure proposed a new mechanism for this effect. It examined a hormone receptor that had evolved from an ancestral protein that was able to bind twohormones to a new protein that was specific for a single hormone. This change was produced by two amino acid substitutions, which prevent binding of the second hormone. However, several other changes subsequently occurred, which were selectively neutral as they did not affect hormone binding. When the authors tried to revert the protein back to its ancestral state by mutating the two “binding residues”, they found the other changes had destabilized the ancestral state of the protein. They concluded that in order for this protein to evolve in reverse and regain its ability to bind two hormones, several independent neutral mutations would have to occur purely by chance with no selection pressure. As this is extremely unlikely, it may explain why evolution tends to run in one direction.[7]
[edit]Proposed mechanism
[edit]Proposed exceptions to Dollo’s law
Fossil of an Armored Dinosaur Hatchling: Youngest Nodosaur Ever Discovered
ScienceDaily (Sep. 27, 2011) — Researchers at the Johns Hopkins University School of Medicine with help from an amateur fossil hunter in College Park, Md., have described the fossil of an armored dinosaur hatchling. It is the youngest nodosaur ever discovered, and a founder of a new genus and species that lived approximately 110 million years ago during the Early Cretaceous Era. Nodosaurs have been found in diverse locations worldwide, but they’ve rarely been found in the United States. The findings are published in the September 9 issue of the Journal of Paleontology.
Please note our name change to the more couth http://ecoandevo.tumblr.com. We will now have a wider focus that encompasses the field of Ecology, along with all of your favorite Evolution facts, theories, news, and information.
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