BISC208 02 11 2014 Office hours 10 12 wolf hall 240 Lectures on Tuesdays and Fridays E text 24383390 Science begins with observations and the formulation of hypotheses that can be tested and that will be rejected if significant contrary evidence is found Science is a method for seeking casual explanation Hypotheses Controlled experiments Comparative o Discovery science Making observations Asking questions Forming hypotheses Making predications Testing predictions To test one of these hypotheses one needs to determine what would happen if the hypothesis is correct If the hypothesis is correct what would happen under future conditions Requires making a deduction if then thinking Crucial step when the cause can t be observed directly can only observe its predicted consequences The result of making a deduction in setting up an experiment is called a prediction an if then statement Dr Deborah Allen deallen udel edu Office hours in Wolf 240 after lecture class from 10 12 or by appointment Dr Meredith Biedrzycki mlbiedrz udel edu 420 D ISEL Mr Scott Jacobs ssjacobs udel edu Evidence for Evolution text module 2 7 02 11 2014 Evolution change over time Line of Evidence 1 When biologists began to compare the morphology anatomical structure of organisms they discovered interesting similarities and differences vestigial structures the useless parts we observe today must have functioned in ancestral organisms Comparative Morphology Analyses of the structure of living and extinct organisms comparative morphology are based on comparisons of characteristics that are similar in two species because of genes they inherited from a common ancestor homologous traits o a Homology Vertebrate forearms the bat wing mouse forearm and human arm are homologous structures as all are composed of similar bones inherited from a recent common ancestor o b Analogy The wings of bats butterflies and birds evolved independently not from a recent common ancestor But they have a similar function flight and so are analogous Vestigial and Atavistic Structures Humans o Muscles for wiggling ears Boa constrictors o Hip bones and rudimentary hind legs Manatees o Fingernails on their fins Blind cave fish o Nonfunctional eyes a Whales evolved from terrestrial ancestors with four legs But in whales the hips and hindlimbs are reduced to small bones with no function b Snakes evolved from lizards with four legs But in primitive snakes the remnants of hindlimbs persist forelimbs are absent c The human appendix is a vestigial structure reduced from the cecum of primate ancestors which was involved in digestion of significant plant material Molecular Techniques and Embryology Early embryos of related species are often similar but morphological differences appear as the embryos grow and develop their adult forms Developmental Similarities Strong anatomical evidence supporting evolution comes from comparisons of how organisms develop Early vertebrate embryos possess pharyngeal pouches that develop into o In humans glands and ducts o In fish gill slits These shared templates reflect the historical continuity between the organisms The Fossil Record Earth is billions of years old Fossils in different layers of rock sedimentary rock strata show evidence of gradual change over time The fossil record documents continuity in morphological characteristics evidence of ongoing change in biological lineages evolutionary sequences of ancestral organisms and their descendants Dating often uses radioisotopes Absolute dating age of fossils is estimated by rates of radioactive decay Relative dating position of the fossil in the sediment Isotopes like U238 transform at precisely known rates into nonradioactive forms The rate of decay is known as an isotope s half life Morphological Series we see the same pattern of development in the fossil record that we see in morphology Biogeography Studies of the world distribution of plants and animals Global explorations provided naturalists with thousands of unknown plants and animals Some species found in similar habitats in different areas resembled each other SUMMARY The fossil record The geographical distribution of living species Homologous structures of living organisms Similarities in early development It s going on around us We can make it happen artificially Evidence of Evolution 02 11 2014 Biological Evolution Biological evolution occurs in populations when specific processes cause the genomes of organisms to differ from those of their ancestors ultimately observable as changes in frequencies of heritable allelic forms of genes These genetic changes and the phenotypic modifications they cause are the products of evolution A population of organisms includes all individuals of a single species that live together in the same place and time Two Levels of Evolutionary Change Microevolution o Describes small scale genetic changes in populations o Responds to shifting environmental circumstances o Example a shift in bill size of a finch species Macroevolution o Describes larger scale evolutionary changes in species and more inclusive groups o Results from gradual accumulation of microevolutionary changes Evolutionary Biology Since Darwin Genetic variation is the basis of evolution the study of population genetics links the ideas of Mendel and Darwin A unified theory of evolution modern synthesis integrates data from biogeography comparative morphology comparative embryology paleontology and taxonomy Modern synthesis focuses on the gradual processes of evolutionary change within populations Agents of Microevolution Processes that foster microevolutionary change Mutation Gene flow Genetic drift Natural selection Biogeography Biogeography studies of the world distribution of plants and animals Some species found in similar habitats in different areas resembled each other Different animals on different continents but similar adaptations to shared environments Island biogeography organisms may differ from related ones on mainland Darwin s finches for example Evolution Natural Selection 02 11 2014 What is Evolution Biological evolution simply put is descent with modification This definition encompasses small scale evolution changes in frequency of allelic forms of genes in a population from one generation to the next and largescale evolution the descent of different species from a common ancestor over many generations Agents of Evolution Processes that foster evolutionary change are o Gene flow o Genetic drift o
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