WZ Lecture 6, Sept. 9

WZ Lecture 6, Sept. 9 - Macroevolution Biological Sciences...

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Unformatted text preview: Macroevolution Biological Sciences 120 Lecture 6, Sept.9 Wiebke Ziebis Chapter 24 continued What you need to know from last lecture: Some important events in the history of life Mass extinctions, followed by adaptive radiations Tree of life - 3 domains Phylogeny, systematics (using fossil, molecular and genetic data to infer evolutionary relationships Taxonomy, binomial nomenclature (Linnaeus) domain, kingdom, phylum, class, order, family, genus, and species Homology, Analogy, homoplasies Molecular systematics, aligning DNA segments using mathematical tools Biogeography, Fossil Record (Paleontology), Transitions The Biological Species Concept The biological species concept states that a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring; they do not breed successfully with other populations Gene flow between populations holds the phenotype of a population together Speciation The Mystery of Mysteries that captivated Darwin is speciation , the processby which one species splits into two or more new species.Speciation is responsible for the tremendous diversity of life. Speciation explains not only differences between species but also similarity between them (the unity of life). Speciation form a conceptual bridge between microevolution, changes over time in allele frequencies in a population, and macroevolution, the broad pattern of evolution over long time spans. Speciation , the origin of new species, is at the focal point of evolutionary theory Evolutionary theory must explain how new species originate and how populations evolve Microevolution consists of adaptations that evolve within a population, confined to one gene pool Macroevolution refers to evolutionary change above the species level Animation: Macroevolution Animation: Macroevolution Are organisms truly divided into units we call species? To answer this biologists not only compare the morphology but less obvious differences in physiology, biochemistry and DNA sequences. Tree of Life The modern tree of life is largely based on sequence comparisons of rRNA genes, which code for the RNA parts of ribosomes. Ribosomes are fundamental to the workings of the cell. rRNA genes have evolved so slowly that homologies between distantly related organisms can still be detected - making them useful for determining evolutionary relationships among deep branches in the history of life. What holds the gene pool of a species together, causing its members to resemble each other? Gene flow, - the transfer of alleles between populations ....
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WZ Lecture 6, Sept. 9 - Macroevolution Biological Sciences...

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