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AP Biology 2/28/13

AP Biology 2/28/13. Chp.25 ~ Phylogeny & Systematics (& Chp.26~Review the Origin of Life, Dating Fossils). Phylogeny: the evolutionary history of a species. Systematics : the study of biological diversity in an evolutionary context The fossil record :

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AP Biology 2/28/13

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  1. AP Biology2/28/13 • Chp.25 ~ Phylogeny & Systematics • (& Chp.26~Review the Origin of Life, Dating Fossils)

  2. Phylogeny:the evolutionary history of a species • Systematics: • the study of biological diversity in an evolutionary context • The fossil record: • The ordered arrangement of fossils (generally within strata of sedimentary rock)

  3. The fossil record • Sedimentary rock: rock formed from sand and mud that once settled on the bottom of seas, lakes, and marshes • Dating: • Relative~ geologic time scale; sequence of species • Absolute~ radiometric dating; age using half-lives of radioactive isotopes

  4. Review: The Origin of Life • Early earth atmosphere • CO2, CH4, NH4 • Very little oxygen • Water • Lightning

  5. Miller-Urey Experiment (1953) • Simulated early earth conditions and added electricity (“lightning”) • Successfully created organic compounds (amino acids)

  6. It is believed that RNA was present before DNA • RNA can replicate itself • RNA can catalyze reactions • Therefore, RNA could have existed as an early form of life before DNA • After RNA was present, any organisms who developed the ability to use DNA and proteins would have been selected for, since they are superior to RNA RNA World Hypothesis

  7. The first cells were probably • Prokaryotic • Primary heterotrophs (eat their food) OR • Maybe simple autotrophs (make their own food) • By the time of the first cell, there would have been many organic compounds in the environment for the cells to “eat” The First Cells

  8. Biogeography: the study of the past and present distribution of species • Pangaea-250 mya • Geographic isolation-180 mya

  9. Extinctions are always occurring at a low rate (background rate) • Occasionally, mass extinction events will happen when many more species will go extinct than normally • Example: • Permian (250 million years ago): • 90% of marine animals; Pangaea merge • ***Human Impact on Ecosystems & Species Extinction Rates*** Extinctions

  10. Mass extinction • Cretaceous(65 million years ago): death of dinosaurs, 50% of marine species; low angle comet (maybe?)

  11. Phylogenetics • The tracing of evolutionary relationships (phylogenetic tree) • Use Linnaean Classification • Binomial nomenclature • Homo sapiens

  12. Phylogenetic Trees • CladisticAnalysis: taxonomic approach that classifies organisms according to the order in time at which branches arise along a phylogenetic tree (cladogram) • Clade: each evolutionary branch in a cladogram

  13. Analyzing the distribution of these derived characters can provide insight into vertebrae phylogeny 0 = character is absent 1 = character is present

  14. Phylogenies • Types: • Monophyletic: single ancestor that gives rise to all species in that taxon and to no species in any other taxon; legitimate cladogram • Polyphyletic: members of a taxa are derived from 2 or more ancestral forms not common to all members; does not meet cladistic criterion • Paraphyletic: lacks some descendants of the common ancestor; does not meet cladistic criterion

  15. Sorting homology vs. analogy... • Homology: • likenesses attributed to common ancestry • (shared ancestry) • Analogy: • likenesses attributed to similar ecological roles and natural selection (convergent evolution) Constructing a Cladogram

  16. Convergent evolution: • species from different evolutionary branches that resemble one another due to similar ecological role • Does not show an evolutionary relationship • When species develop similar adaptations because of similar environments • Dolphins and sharks • Flying insects and birds Convergent Evolution

  17. Analogy – Convergent Evolution • These structures are analogous, because they did not come from a common ancestor but were evolved separately

  18. Coevolution • Species evolve together because of some relationship • Predator/Prey or Parasite/Host: • “Evolutionary arms race” • Symbiotic relationships • Flowers (Plants ) and pollinators (insects, bats, birds) Patterns of Evolution

  19. Humans and chimpanzees last had a common ancestor about 6 million years ago • The genus Homo evolved approximately 2 million years ago and included several species (although only Homo sapiens is still alive) • Anatomically modern human is approximately 200,000 years old Human Evolution

  20. Bipedalism (walk upright) • “Lucy” – nearly complete skeleton of Australopithecus afarensis – 3 million years ago • Large brain, good reasoning skills, tool-making (not exclusively human) • Extended childhood • Speech (hyoid bone) Human Traits (not exclusive to Homo sapiens)

  21. According to this phylogeny, humans are most closely related to chimpanzees (Genus Pan). (split ~ 6 mya) The ancestor of gorillas branched off earlier in evolution (~8 mya). Pongo = Orangutan Hylobates = gibbons

  22. Ancestor or subspecies of H. erectus • Lake Turkana, Kenya (“Turkana Boy”) discovered by Richard Leakey • Used tools Homo ergaster

  23. Phylogenetic Trees/Cladograms Practice

  24. Mass Extinctions

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