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Transcript
Theory of Evolution & Microevolution Chapter 13 Evolution • Darwin and his theory • Evolution Evidence Charles Darwin Natural Theology • Based on a literal view of the Genesis Story • Earth 6,000 yrs old • No new species • No physical changes (valleys, mountains) Putting Darwin in the context of his time Important people • • • • Linnaeus Lamarck Malthus Lyell Linnaeus • • • • • • Studying biology to reveal a divine plan Developed modern taxonomy Made Binomials: Homo sapiens Based groupings on morphology Did not believe in evolution, Taxonomy data would later provide some of best evidence Lamarck • Got the genetics wrong • Stressed acquired traits-(wrong) – Giraffes stretched their necks – Babies had longer necks • But- said species evolved to be better suited to environment – right! Malthus • British economist studied Paris after the revolution • Limited resources • Excess population growth • Struggle to survive, • competion among individuals • Survival of the richest Malthus • Darwin was influenced by Thomas Malthus’s Essay on the Principle of Population (1798) – Populations increase geometrically, while food supply increases only arithmetically Fig. 2.6 Lyell • • • • • • British geologist. Following Hutton’s work Earth is old Valleys formed by erosion Mountains by uplifting Slow processes over LONG periods of time Fig. 2.13 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 5 year voyage of the Beagle British Isles North America Europe Western Isles North Atlantic Ocean Asia Canary Islands Cape Verde Islands Marquesas Society Islands Africa Indian Ocean Keeling South America Galápagos Islands Valparaiso Straits of Magellan Cape Horn Bahia North Pacific Ocean Philippine Islands Islands Madagascar Ascension St Helena Rio de Janeiro Montevideo Buenos Aires Mauritius Bourbon Island Equator Australia Friendly Islands Sydney Cape of Good Hope Port Desire South Atlantic Falkland Islands Ocean Tierra del Fuego King George’s Sound Hobart New Zealand Evidence that Made Darwin think.. • The variation among organisms in a population • Biogeography – where species are found around the globe • Fossil record • Comparative morphology – Linnaeus's classification • Artificial Selection • Geology and the age of the earth • Malthus and economic theory • Lamarck’s theory and adaptations Evolution- Just a Theory? • Theory vs. Law vs. Dogma Terms: • • • • Theory – explain a process Law- describes a phenomenon, a formula Dogma is not testable – beliefs Science is limited to things we can measure, test. • Hypothesis – is an “educated” guess to explain a problem, Scientific Method • • • • • • Problem, observation Background information, literature search Hypothesis based on previous work Experiment to test hypothesis Analyze results If hypothesis supported – publish a paper. Darwin’s Theory • Populations have inherent variation among individuals. • These traits are heritable • Resources in the environment are limited • Populations have a greater fertility than their environment can sustain. • Populations would grow exponentially, but most remain stable in size. A population of Liguus fascitus Variation in shell coloration patterns Darwin’s Theory continued: • There is a struggle to survive among the offspring called Natural Selection. • The survivors are better fit • Fitness is the ability to have more offspring (frequency of genes in the genepool). Natural Selection • “struggle “ or competition does not have to be a fight to death • May just be as simple as a seed germinating earlier and getting established first. It produces 120 seeds. A later germinating plant makes only 50 seeds. • “Fitness” is the success rate of the offspring in future generations. Fig. 2.7 Some Evidence for Evolution • Microevolution- antibiotic, pesticide resistance – Artificial selection • Fossil record • Biochemical comparisons – Protein sequences – DNA, gene comparisons • • • • Morphological comparisons Embryology Biogeography Genetically modified organisms Fig. 2.9 Fig. 2.5 Fig. CO 2 Fig. 2.10 Evolution in progress around us: • Antibiotic resistance • Herbicide, Pesticide resistances • New disease threats (AIDS, SARS, Ebola, West Nile Virus) • Climate change • Introduced species • Biotechnology ??? Fig. 2.8 Darwin and Human Evolution • Published “Descent of Man” in 1871 • Wasn’t first to hypothesis our relation to apes • caused more popular criticism of his general theory All made by Artificial Selection from wild mustard Artificial Selection: human designed breeding of plants and animals for desired traits by selecting which individuals get to reproduce. backbone pelvic girdle coccyx (bones where many other mammals have a tail) thighbone attached to pelvic girdle small bone attached to pelvic girdle Missing Links Galapagos Finches • Specialization to different feeding sources may have diversified the species. Sexual Selection Directional Selection modifies Beak depth during drought periods Fig. 2.16 Fig. 2.15 Homologous features • Derived from a common ancestor • Often do not have similar functions • Changes in the timing of genes forming body parts can alter their over-all shape. adult proportions in infant chimpanzee adult proportions in infant human 4 3 early reptile 21 5 21 3 4 pterosaur 1 chicken 2 3 1 2 bat 3 4 1 5 porpoise 2 4 3 5 penguin 2 1 2 3 4 5 3 human Analogous Features • Have same functions ( by convergence) • Do not have a common ancestry • Are not derived from the same ancestral feature Butterfly and Bird • No bones in butterfly, not from common ancestor • Structures not related Ecotypes • Populations that adapted to local environmental conditions. • Still one species – inter-fertile • Can form clines – serial ecotypes along a gradient – Common garden experiment (e.g. elevation and yarrow) • Need to preserve local adaptations in plants – In Botanical garden they always list source of plant Ecotypes forming a cline Fig. 23.8 Convergent Evolution • Sometimes unrelated species may superficially look alike • Both species have adapted to similar habitats. • Evolution comes up with similar adaptations to the conditions • Does not mean they are closely related Convergent Evolution Ocotillo North America Allauidia Madagascar Fig. 13.9b