Evolution

Evolution - Life and Evolution A view from Earth Science...

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Unformatted text preview: Life and Evolution A view from Earth Science What is Life? “textbook definition” • Metabolism – Homeostasis • • • • • Organization Reproduction/Growth Adaptation/Evolution Response to stimuli etc. Taxonomy versus Phylogeny • Taxonomy: The classification of organisms Taxonomy versus Phylogeny • Phylogeny: The study of the (evolutionary) relationships between groups of organisms • commonly depicted as a tree Species basic unit of taxonomy and phylogeny Biological Species Concept • a population of organisms capable of interbreeding and producing fertile offspring Genetic Species Concept • Based on the similarity of DNA in a population – % similarity • Reveals interrelatedness on a molecular scale Genetic Species Concept background terms • Deoxyribonucleic acid (DNA) – blueprint of life • Gene: a specific segment of DNA that encodes for a specific purpose • Genome: the entire genetic code of an organism http://www.ncbi.nlm.nih.gov/About/primer/genetics_genome.html Do you see a problem for Earth Science?? Morphologic Species Concept • Based on similarity of appearance • morphology = shape Traditional Phylogenetics for Earth Scientists • “The Expert Opinion” – “B looks more similar to A than C” – Problem: very subjective... Modern Phylogenetics for Earth Scientists • Cladistics – based on parsimony • define characters • construct tree using parsimony – Removes a certain degree of subjectivity Willi Hennig Cladistics and Parsimony • The hypothesis that requires the fewest assumptions is the best. • Assumes the minimal number of evolutionary changes occurred to infer phylogenetic relationships. branch branch branch node node sis gr ter ou p r te sis oup gr last common ancestor clade 1 4 limbs jaws Monophyletic clade = a species and all of its descendants clade 2 4 limbs jaws Monophyletic clade = a species and all of its descendants not a clade 4 limbs jaws Polyphyletic does not include all the descendants, thus not a real clade The E Word Evolution Change through time Darwinian Evolution (modern synthesis version) • “Descent with modification via natural selection” • Diversity of life arose through a branching pattern of evolution and common descent rant alert XXX Survival of the Fittest? Survival of the minimally fit! XXX rant alert Darwinian Evolution (modern synthesis version) • “Descent with modification via natural selection” • Diversity of life arose through a branching pattern of evolution and common descent Descent • Genes are specific segments of DNA that encode for a particular purpose • Genes are passed from one generation to the next – the next generation inherits the genes of the past generations Decent with Modification • Genetic Drift – genes are not necessarily perfectly passed from one generation to the next...mistakes happen. Decent with Modification • Changes in Geonotype lead to changes in Phenotype over generations – Genotype: your genetic code – Phenotype: the manifestation of your genetic code • e.g., what you look like... Genetic Drift Mechanism • Random Mutation – accidental changes in DNA • DNA fails to copy accurately – beneficial (some) – neutral (most) – harmful (some) Genetic Drift Mechanism • Random Mutation – accidental changes in DNA • DNA fails to copy accurately – beneficial (some) – neutral (most) – harmful (some) Genetic Drift Contributing Factors • Geographic isolation Dude! Que pasa? ? Natural Selection • Environmental factors** provide selection pressure for advantageous traits – those with “advantageous” mutations are favored over those with neutral or harmful mutations – **temperature, climate, nutrient availability, competition, etc., etc., etc. Evidence for Descent with Modification via Natural Selection • Genetics • Artificial Selection • The Fossil Record – Homology – Analogy Common Descent Genetics • All life on Earth (that we know of) is DNAbased • Unravelling DNA reveals all organisms share a common ancestor – LUCA The Universal “Tree of Life” Bacteria Archaea Eukaryotes The Universal “Tree of Life” Bacteria Archaea Eukaryotes Last Universal Common Ancestor (LUCA) The Universal “Tree of Life” Bacteria Archaea Eukaryotes YOU ARE HERE Artificial Selection • Humans consciously select for or against particular features in organisms. Unintentional Artificial Selection • Humans unconsciously select for or against particular features in organisms. – classic example: antibiotic resistance in pathogenic bacteria The fossil record • Homology • Analogy Homology • Similar characters inherited from a common ancestor that also had that character – examples arm bones Homology • Example: vestigial organs Analogy and Convergent Evolution • Characters with separate evolutionary origins that are superficially similar because they evolved to serve the same function. – Analogies are the result of convergent evolution Convergent Evolution • Organisms not closely related independently evolve similar traits • They have adapted to similar environments. Convergent Evolution Significance • Environmental conditions repeat over time • thus, similar shapes evolve multiple times throughout geologic history Fossil record and transitional forms • Taxonomy versus phylogeny – splitters vs. lumpers • Soft parts versus hard parts/becoming a fossil • The nature of the geologic record • MANY examples of transitional forms at higher taxonomic levels Nature of the Rock Record A B A up to 10 m/ka (1-10) B up to .4 m/ka (.02-.4) C C up to 0.003 m/ka (.001-.003) time is relative to frame of reference Misconceptions about evolution • "Evolution is like a climb up a ladder of progress; organisms are always getting better." • "Natural selection involves organisms 'trying' to adapt." • "Natural selection gives organisms what they 'need.'" Are you superior to Shewanella? • Lives aerobically and/or anaerobically • Lives on nitrite, nitrate, thiosulfate, iron, manganese, uranium, and other things Misconceptions about the evidence for evolution • "Evolution is 'just' a theory." • "Gaps in the fossil record disprove evolution." • "The theory of evolution is flawed, but scientists won't admit it." • "Evolution is not science because it is not observable or testable." Misconceptions about teaching evolution • "Teachers should teach 'both sides' and let students decide for themselves." • "Evolution is itself 'religious,' so requiring teachers to teach evolution violates the First Amendment." Misconceptions about the implications of evolution • "Evolution leads to immoral behavior. If children are taught that they are animals, they will behave like animals." • "Evolution supports the idea that 'might makes right' and rationalizes the oppression of some people by others." ...
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