Abiogenesis & Evolution

Lipids or RNA world?

The Woodstock of Evolution -- The World Summit on Evolution (ScientificAmerican.com): University of Massachusetts theoretical biologist Lynn Margulis, asked Antonio Lazcano, President of the International Society for the Study of the Origins of Life, 'In your opinion what came first, cells or the RNA world?' Lazcano answered: 'If you define a cell as a membrane-enclosed system, then lipids-enclosed systems assisted in the polymerization of molecules, which led to RNA. Lipids and cells came first, then the RNA world.'"

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capping by ancient eukaryotes

UB Department of Biological Sciences: Kiong Ho: "Initial analysis of the mRNA capping apparatus of T. brucei and the malarial parasite P. falciparum has illuminated an evolutionary connection to fungi rather than metazoans. T. brucei and P. falciparum encode a triphosphatase that is structurally and mechanistically similar to the fungal enzymes. RNA triphosphatase is an attractive drug target because the mechanism of cap formation is completely different from the metazoan host and metazoan species encode no recognizable homologue of the fungal/protozoan enzymes. Thus, a mechanism-based inhibitor against triphophatase should be highly selective for the parasite and have minimal effect on the human host or arthropod vector."

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ancient eukaryotic functions

UB Department of Biological Sciences: Kiong Ho: "Parasitic protozoa are causative agents of widespread human diseases, including malaria (caused by Plasmodium falciparum), African sleeping sickness (Trypanosome brucei), and Chagas' disease (Trypanosome cruzi). Because these parasites diverged early from the main branch of the eukaryotic lineage, their unusual mechanisms of gene expression reflect ancient eukaryotic functions that have been preserved to present. By studying the process of gene expression, not only may we learn about the evolution of higher eukaryotes, but we can also identify parasite specific processes that can be exploited as targets for novel therapeutic intervention."

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Cambrian Explosion

"Stratigraphic sections spanning the Vendian-Cambrian boundary show a broadly similar pattern whereby the key events are bracketed by the 600-million-year (Myr)-old Neoproterozoic glacial deposits (tillites) and in the succeeding Cambrian diverse metazoan assemblages, typified by abundant skeletons, diverse trace fossils, and Burgess Shale-type faunas (Fig. 1). One key development is a series of accurate radiometric determinations (1). The Vendian-Cambrian boundary is now placed at 543 Myr, and the duration (45 Myr) of the Cambrian is substantially shorter than once thought. The preceding Ediacaran faunas have an approximate age range of 565-545 Myr. Accordingly, the overall time-scale for discussion is a relatively protracted 65 Myr, although the principal events of evolutionary interest are probably more tightly bracketed (550-530 Myr) between the diverse Ediacaran faunas of latest Neoproterozoic age (2) and the Chengjiang Burgess Shale-type faunas (3). Correlations are also assisted by emerging schemes of chemostratigraphy (2, 4), notably with reference to strontium (87Sr) and carbon (13C)." Simon Conway Morris The Cambrian "explosion": Slow-fuse or megatonnage? PNAS April 25, 2000 vol. 97 no. 9 4426-4429



Science & Technology at Scientific American.com: The Woodstock of Evolution -- The World Summit on Evolution, held in the Galapagos Islands, revealed a science rich in history and tradition, data and theory, as well as controversy and debate: "Stephen Jay Gould's Wonderful Life stimulated a lot of new ideas about the Cambrian explosion of life, he continued, and it soon became clear that there were a huge variety of organisms difficult to classify, such as those in the Burgess Shale. But there are a number of Cambrian fossil beds, such as in China, where important phyla such as Chordata evolved. 'But what does all this diversity mean?' Fortey asked. 'There are today 30 living phyla. In the Cambrian, some claim that there were as many as 100 phyla, but the evidence does not support this. We now believe that morphological diversity did not explode as much as Gould originally suggested, although the explosion in evolutionary experimentation was real. By the time we get to the Cambrian, like at the Burgess Shale, the systems are very complex, such as trilobite eyes. Evolution was experimenting with many wondrous varieties, such as all the armor on the heads of trilobites.' "

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Homo Floresiensis: More Bones Support Mini Human Case

Scientific American.com: More Bones Support Mini Human Case: "Now Morwood, Brown and their colleagues say that various arm, leg, jaw, toe and finger bones as well as a scapula and vertebra were excavated in 2004, bringing the estimated number of individuals represented thus far at Liang Bua to nine and casting doubt on those alternative interpretations. Analysis of the second jaw shows that it is very similar to the first one. Both notably lack a chin, which is a unique characteristic of Homo sapiens, even those that suffer from microcephaly. And further study of the leg and arm bones confirm that H. floresiensis was about a meter tall and had long arms. Modern adult pygmies have legs and arms that are proportional to their short stature. 'We can now reconstruct the body proportions with some certainty,' the researchers write in the October 13 issue of Nature."

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. . . evolving since 10/06/06