mcdb20lec8Su09

mcdb20lec8Su09 - Lecture 8 Brief Recap: Evolutionary...

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Lecture 8 Brief Recap: Evolutionary Mechanisms Evidence for Evolution Origin of life on Earth Macroevolution and BioDiversity Biological Species Concept Speciation Phylogenetic Taxonomy and the Tree of Life "Nothing in biology makes sense except in the light of evolution" Theodosius Dobzhansky (geneticist) 1973 “.. as a theory, evolution is as validated as Newton's Laws of Motion, and clearly as important for the understanding of the physical world. Yet, and paradoxically, evolution is either misunderstood or even adamantly denied by a large proportion of the (American) public.” Evolution Mutation Migration Genetic Drift Natural Selection (change in allele frequencies in a population) Mechanisms Founder Effect: Hobbits 5 Three Types of Natural Selection Five primary lines of evidence: 1. The fossil record 2. Biogeography 3. Comparative anatomy and embryology 4. Molecular biology 5. Laboratory and field experiments 1. The fossil record documents the process of natural selection.
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Gaps in the Fossil Record • Gaps should exist because: – Organisms quickly decay – Fossils are often damaged by the environment – Fossils are difficult to locate – Evolution probably wasn’t gradual over time 2. BioGeographic patterns of species’ distributions reflect their evolutionary histories. History Matters ! Who arrived first? ! Are numerous different habitats available? 3. Comparative anatomy and embryology reveal common evolutionary origins. Homologous Structures The human appendix serves no function. Why are we all born with one?
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Convergent Evolution Analogous structures all developed from different original structures. 4. Molecular biology reveals that common genetic sequences link all life forms. DNA Similarities and Differences ! The more distantly you and another individual are related, the more your DNA differs. ! The more distantly related two populations are, the more their DNA differs ! In Rhesus monkeys, 138/141 amino acids are the same as those found in human hemoglobin. Recency of Common Ancestry ! Estimates of evolutionary relatedness made from: •Comparative Anatomy •Embryology •The Fossil Record ! “Molecular Clocks” 5. Laboratory and field experiments enable us to watch evolution in progress. Changes in the Frequency of the Various Alleles The Origin and Diversification of Life on Earth Learning Objectives Be able to describe how: ! Life on earth most likely originated from nonliving materials. ! Species are the basic units of biodiversity. ! Evolutionary trees help us conceptualize and categorize biodiversity. ! An overview of the diversity of life on earth.
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mcdb20lec8Su09 - Lecture 8 Brief Recap: Evolutionary...

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