第三章细胞的起源与进化.pptx

关于进化的讨论陈士超 副教授21世纪生命科学进展课程2009-9-221895年11月24日，在英国伦敦，这是很不平凡的一天。 这一天，伦敦众多市民涌向一家书店，争相购买一本刚出版的新书。这一书的第一版一千二百五十册在出版之日即全部售罄。许多读者因买不到它而悻悻然。原先不甚乐意承印它的出版商突然精神一振，又再版三千册，也很快卖光了。欧洲各国不少读者还要求邮购。这在当时确是罕见的。 这本轰动一时的新书就是《物种起源》。它是进化论的奠基人查理士·达尔文的头一部巨著。自然选择学说１、过度繁殖２、生存斗争３、遗传变异４、适者生存 过渡繁殖 地球上生物普遍具有很强的繁殖能力，都有依照几何比率增长的倾向。达尔文指出，象是一种繁殖很慢的动物，但是如果每一头雌象一生（30～90岁）产仔6头，每头活到100岁，而且都能进行繁殖的话，那么到750年以后，一对象的后代就可达到1900万头。照此计算，就是繁殖不是很快的动、植物，也会在短时期内产生大量后代而占满整个地球。但事实上，几万年来，象的数量也从没有增加到那样多，自然界里很多生物的繁殖能力都远远超过了象的繁殖能力，但各种生物的数量在一定的时期内都保持相对的稳定状态，这是为什么呢？达尔文因此想到了生存斗争。 七种脊椎动物和人的胚胎发育的比较when i sat for this sculpture, they told me it would never be placed on display!讨论： 人类进化未来lol! at least they toned down on the hair and made you look a bit more respectable! :DExactly! I shouldnt complain, looking as clean-cut as I do here.Complete Neandertal Mitochondrial GenomeSummaryA complete mitochondrial (mt) genome sequence was reconstructed from a 38,000 year-old Neandertal individual with 8341 mtDNA sequences identified among 4.8 Gb of DNA generated from 0.3 g of bone. Analysis of the assembled sequence unequivocally establishes that the Neandertal mtDNA falls outside the variation of extant human mtDNAs, and allows an estimate of the divergence date between the two mtDNA lineages of 660,000 ± 140,000 years. Of the 13 proteins encoded in the mtDNA, subunit 2?of cytochrome c oxidase of the mitochondrial electron transport chain has experienced the largest number of amino acid substitutions in human ancestors since the separation from Neandertals. There is evidence that purifying selection in the Neandertal mtDNA was reduced compared with other primate lineages, suggesting that the effective population size of Neandertals was small.On the cover: In 1997, the first mitochondrial sequence was retrieved from Neandertals (Krings et al., Cell 90, /cgi/content/abstract/134/3/1919–30). Now, advances in high-throughput sequencing are beginning to make genomic studies in Neandertals possible. In this issue, Green et al. (pp. /cgi/con