Evolution

BBC Education Evolution http://www.bbc.co.uk/education/darwin/index.shtml

Evolution theory and science

Eukaryotic Cells — the next evolutionary step

Evolution and the Nature of Science Institutes

Biology lessons: how do populations change over time?     

Cosmic Evolution

Just as biological evolution is the heart of modern biology, cosmic evolution is the heart of modern cosmology. For instructors to be confident in teaching science, it is helpful for them to appreciate the current understanding of the composition and development of the universe, especially the revolutionary changes that have taken place in our understanding over the last two decades. Biological evolution requires the products of cosmic evolution—the elements of which life is composed were formed in the cores of stars—and the two areas of science are thus crucially, and even inspiringly, connected.     

Cultural Evolution

SYNOPSIS. Culture is made possible by the existence of mechanismsof learning and communication. Because of it, we can profitfrom the experience and ideas of others. It is convenient toinclude in it tools, technologies, and all culturally transmittedbehaviors. At least from an evolutionary point of view, theyshare common mechanisms. It is also becoming increasingly clearthatanimals share with us potential for cultural adaptation, whichis however much more highlydeveloped in humans, as shown forinstance, by the extension of human brain areas that are involvedin control of hand and phonation organs. To understand how culture evolves one can make resort to modelsthat map reasonably well after the necessary substitutions,into those that havebeen useful in biology. A major differencethat one finds is in mechanisms of transmission, which are muchmore varied in culture than in biology. Parent-child (vertical)transmission is present in both. An "infectious" (horizontal)mechanism is characteristic of cultural transmission, but ispractically absent in the genetic case. Other mechanisms oftransmission are reviewed, along with their evolutionary consequences.The variety of these mechanisms can make culture extremely fastand flexible, and there are the great advantages of culturaladaptation vs. genetic adaptation by natural selection, or vs.physiological adaptations (which are relatively fast but highlyspecific: for instance, tanning under exposure to UV). But culturecan also be extremely conservative. Also, some cultural transmissionmechanisms allow heterogeneitybetween individuals to persist,others tend to make populations extremely homogeneous. The study of culture from an evolutionary point of view is young,but very promising.     

Mitochondrial Evolution

Viewed through the lens of the genome it contains, the mitochondrion is of unquestioned bacterial ancestry, originating from within the bacterial phylum α-Proteobacteria (Alphaproteobacteria). Accordingly, the endosymbiont hypothesis—the idea that the mitochondrion evolved from a bacterial progenitor via symbiosis within an essentially eukaryotic host cell—has assumed the status of a theory. Yet mitochondrial genome evolution has taken radically different pathways in diverse eukaryotic lineages, and the organelle itself is increasingly viewed as a genetic and functional mosaic, with the bulk of the mitochondrial proteome having an evolutionary origin outside Alphaproteobacteria. New data continue to reshape our views regarding mitochondrial evolution, particularly raising the question of whether the mitochondrion originated after the eukaryotic cell arose, as assumed in the classical endosymbiont hypothesis, or whether this organelle had its beginning at the same time as the cell containing it.In 1970, Lynn Margulis published Origin of Eukaryotic Cells, an influential book that effectively revived the long-standing but mostly moribund idea that mitochondria and plastids (chloroplasts) evolved from free-living bacteria via symbiosis within a eukaryotic host cell (Margulis 1970). The discovery in the 1960s of DNA within these organelles together with the recognition that they contain a translation system distinct from that of the cytosol were two of the observations that Margulis marshaled in support of the endosymbiont hypothesis of organelle origins. Indeed, throughout her career, Margulis forcefully argued that symbiosis is a potent but largely unrecognized and unappreciated force in evolution (Margulis 1981). Technological developments in DNA cloning and sequencing in the 1970s and 1980s opened the way to the detailed characterization of mitochondrial genomes and genes, and the generation of key molecular data that were instrumental in affirming a bacterial origin of the mitochondrial and plastid genomes, allowing researchers to pinpoint the extant bacterial phyla to which these two organelles are most closely related. Over the past several decades, numerous reviews have documented in detail the biochemical and molecular and cell biological data bearing on the endosymbiont hypothesis of organelle origins (Gray 1982, 1983, 1989a,b, 1992, 1993, 1999; Gray and Doolittle 1982; Wallace 1982; Cavalier-Smith 1987b, 1992; Gray and Spencer 1996; Andersson and Kurland 1999; Gray et al. 1999, 2001, 2004; Lang et al. 1999; Andersson et al. 2003; Burger et al. 2003a; Bullerwell and Gray 2004). Various endosymbiotic models proposed over the years have been comprehensively critiqued (Martin et al. 2001), while the debates surrounding the endosymbiont hypothesis have been recounted in an engaging perspective that traces the development of ideas regarding organelle origins (Sapp 1994). Within a historical context, the present article emphasizes more recent data and insights that are relevant to continuing questions regarding how mitochondria originated and have since evolved.     

Evolution,Cultural Evolution,and Epistemic Optimism

Acta Biotheoretica -     

Banning Evolution

Laws prohibiting the teaching of human evolution were in effect in some states for over 40 years during the twentieth century. While such laws have been ruled unconstitutional, the opposition to evolution which stimulated their adoption continues as a prominent feature of American culture.