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Unformatted text preview: B1AA3 Jan. 11/2007 Scientific Method Hypothetico-deductive thinking --Science as a process Strong Inference Falsification Exercise The Brother Tom Fallacy Evidence for micro-evolution by natural selection: guppy life history Scientific Method Hypothetico-deductive thinking Science as a process. Hypothesis Inductive Reasoning educated guess proposed as tentative answer to a specific question or problem Prediction Deductive Reasoning inferring from hypothesis a premise which must be true if the hypothesis is correct. Figures 1.19, 1.20 Strong Inference. Falsification of all other competing hypotheses. Platt 1964 published in Science Hypothesis Testing Exercise $50,000.00 from NSERC to support your first grant to test the following hypothesis: Hyp. 1: ALL VOWELS HAVE EVEN NUMBERS ON THEIR OPPOSITE SIDES. At $25,000.00 per card which two would be most revealing to turn over in an attempt to falsify the hypothesis? Conclusion after selecting the two best (A and 7) = hypothesis supported, not falsified Repeat process to test Hyp 2: ALL CONSONANTS HAVE ODD NUMBERS ON THEIR OPPOSITE SIDES. Conclusion after selecting the best two (K and 4) = Hypothesis falsified strong result contrast with hypothesis support (beware that predictions and experiment must be fair and appropriate to allow falsification) BROTHER TOM (slides) problem of pet hypotheses. Example 1 : Reznick (and Endler) study. Inductive reasoning/predictions/strong experimental evidence for evolution of life history features (life schedule of growth and reproduction) Figures from another source OBSERVATIONS in natural pools in Trinidad: Guppy predators: Killifish preferentially feed on small guppies Pike cichlids preferentially feed on large guppies Exp.1 Bring guppies from different populations with different life histories into the laboratory in identical, predator-free environments and monitor. Results: --several generations raised in lab no measurable shift in life history Hyp. 2. Feeding preferences of different predators caused contrasting life histories in different guppy populations to evolve by natural selection. Prediction: Prediction: Life histories of members of the same populations will diverge when placed under different predator regimes Experiment: Transfer guppies from pool with Pike cichlids (predators of large guppies) to pool with Killifish and no guppies....
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