BSC 2011 Unit III Study Guide Plato God created all things 1 Essentialism Idealism everything had a constant perfect essence Ideal species do not change no new species Aristotle all living things are xed in a linear hierarchy Before evolution was suggested in 350 BC Natural Theology study of nature to better understand God s plan Carolus Linnaeus 1750 sought to discover order and classify the diversity of life to better understand God s plan Created the classi cation system Before evolution was suggested in 350 BC Catastrophism proponents usually accepted a divine creation believed that the earth was young fossil records re ect extinctions due to catastrophes not evolution George Curvier Uniformitarianism mechanisms of geologic changes are constant over time the same processes are operating today as in the past Earth is very old Charles Lyell Lamarck earlier species 2 Evolution species change over time and new species arise by the modi cation of ex beak of nch Microevolution gradual evolution of traits within a population of a species over time Macroevolution evolution of an entirely new species 3 Arti cial Selection new species created from common ancestor via selective ex arrive at new species of nch breeding by humans ex fancy pigeons Comparative Anatomy comparing the anatomy of different organisms supports the idea of descent with modi cation from a common ancestor ex comparing limb bones despite their function Homologous structure Geology geological features arise by slow gradual processes over long periods of time Paleontology study of fossils preserved evidence of previously living things reveals mostly changes over time Comparative Embryology early embryos of diverse but related groups share many features as development proceeds embryonic forms diverge and become more similar to adults of their own species ex insect wing vs bird wing ex Rhesus monkey has 95 of the same amino acids as humans 4 Molecular Biology can provide evidence for evolution through protein and DNA sequence comparisons 5 Analogous structures same function but evolved independently Homologous structures common evolutionary origin but whose function may have changed adapted over time Vestigial Structures remnants of once functional ancestral structures 6 Darwin found it intriguing how there were 14 different nches that evolved from a common mainland ancestor each adapted to suit the conditions of their various islands ex human appendix tail bone goose bumps ex forelimbs in humans birds whales cats Variety of nch beak size was what helped Darwin formulate his hypothesis 7 Process by which populations evolve via natural selection within a population more offsprings are produced that can survive to reproduce leads to competition for limited resources and struggle for existence genetic variation exists in all organisms some of this variation effects an individuals ability to survive and reproduce who survives is not random ttest individuals produce more offspring and contribute more of their genes to the next generation results in a change in the gene composition from one generation to the next with favorable characteristics accumulating over time Genetic variation is required for evolution because it is the key factor for the ttest to survive and have a species evolve without it there would not be a difference or change in a species therefore no evolution takes place 8 Darwin s views differed from Lamarck s from that his theories made natural selection the key factor for evolution instead Lamarck s inheritance of acquired characteristics was a faulty mechanism therefore discredited 9 Populations evolve not individuals 10 There must be genetic variation for natural selection to occur because that s the The meaning of this phrase is that individuals in a population vary some are better able to survive and reproduce given a particular set of environmental conditions these individuals generally survive and produce more offspring thus passing their advantageous traits on to the next generation overtime the population changes only way the ttest individuals will survive in the long run This phrase means that the better adapted overpower survival therefore decreasing variation in species 11 Natural selection eliminated variation 12 Mechanisms that act to maintain genetic variation in a populaton Genetic mechanism meiosis and sexual reproduction crossing over independent assortment diploidy and dominance heterozygotes recessive alleles are not expressed but random gamete fusion remain in population pool epistasis can hide dominant allele from natural selection Selection mechanism some maintain rather than eliminate variation polymorphism when more than one form of a trait is evident among individuals in a population Balancing selection when natural selection maintains 2 phenotypic forms in a population aka balanced polymorphism Disruptive selection in patchy environments maintains a balanced polymorphism Frequency dependent selection tness of a genotype depends on its frequency in the population ex dark and light mice rare genotypes have a selective advantage helps maintain genetic diversity helps prevent usual elimination of rare phenotypes by genetic drift mechanisms 13 Selectively neutral variation genetic variation and polymorphism can be Heterozygote advantage when heterozygous genotypes have higher tness than either homozygote therefore both alleles are maintained maintained in a population when nucleotide variations alleles do not affect tness or reproductive success gene pool the total number of alleles of every individual in an interbreeding population allele frequency the frequency of an allele relative to that of other alleles of the same gene in a population genotype frequency the frequency that a particular allele arises within a species phenotype frequency a ratio stating that number of times a speci c phenotype occurs in a population in a single generation gene xation the increase of the frequency of a gene by genetic drift until no other allele is preserved in a speci c nite population when only one allele is present in a population therefore all homozygous 14 Hardy Weinberg Theorem developed principles for studying gene inheritance in populations that are not evolving to provide a comparative basis for studying populations that are evolving Conditions for population to be HW not evolving large randomly mating population no immigration mutation or selection no natural selection no net change in
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