4 - Biology 1001 Spring 2008 (B. Fall), Class notes, topic...

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Biology 1001 Spring 2008 (B. Fall), Class notes, topic #4—Evidence for evolution Preparation: complete the reading assignment in your text (Freeman, Biological Science, 2 nd ed.): pp. 22-23, 496-503, 561-563, 639-640. Learning objectives: 1. Appreciate the diversity of evidence that has persuaded virtually all biologists of the fact of evolution. 2. Learn some techniques scientists use to determine both relative and absolute ages of fossils. 3. Describe some general patterns in the fossil record and conditions that can lead to fossilization. 4. Distinguish homologous from analogous structures. 5. Understand some basic patterns of biogeography that are explained by evolution. Notes: I. Evidence for evolution is provided by a wide variety of sources: fossils; comparative anatomy and embryology (structural and developmental homologies); biogeography (patterns of geographic distribution of organisms); phylogenetic patterns; plant and animal breeding (artificial selection); and, more recently, comparative biochemistry (molecular homologies). These sources provide overwhelming evidence that species change over time, and that species are descended, with modification, from ancestral ones, creating hierarchical patterns of relatedness. II. Fossils are remains or other evidence of past life, and include unaltered remains, mineralized remains, casts and molds, and trace fossils (e.g., footprints, tracks, feces). A. Three general kinds of rocks include: sedimentary, igneous, metamorphic. Sedimentary rocks (e.g., limestone, shale) form from layers of sediments (deposited by water, wind) and may contain fossils; igneous rocks form from molten material (e.g., granite, volcanic ash), and may be useful for radiometric dating of strata and associated fossils. B. Fossilization of a particular organism is a very improbable event. Steps include burial after death; fossilization after burial; discovery after fossilization. The fossil record is very biased (non- random), and some groups are much better represented as fossils than others. Those most likely to become fossils include: organisms with hard parts; inhabit aquatic habitats where they are more likely to be rapidly buried by sediments; belong to large population; lived more recently. C. Dating fossils 1. Relative dating methods involve establishing chronological relationships (older/younger)— younger sediments lie above older ones (the principle of superposition ) unless subsequently deformed. Index fossils are distinctive fossils used to correlate sedimentary layers of similar age in different regions. The geologic timetable (eras, periods, epochs; see Fig. 26.9 in text) originated in the early 1800s and was based on characteristic fossil components of strata (layers) and relative time. 2.
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This note was uploaded on 04/21/2008 for the course BIOL 1001 taught by Professor Fall during the Spring '08 term at Minnesota.

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4 - Biology 1001 Spring 2008 (B. Fall), Class notes, topic...

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