Change over time of the genetic composition of a population○Decent of modern organisms with modification from preexisting organisms○Evolution: 2 main ideas•Accumulation of inherited characteristics that enhance organisms' ability to survive in specific environments ○Evolutionary adaptation•Everyone is differentVariation○Some people lose Competition○2 things needed for evolution•What is evolution and adaptationBodies of living organisms are modified through the use or disuse of partsUse & disuse○These modifications are inherited by offspringInheritance of acquired characteristics○Lamarck•Pre-Darwinian theory of evolutionCatastrophes caused extinct species & strata Catastrophism○Cuvier (catastrophism)•Slow natural forces (wind, water, earthquakes, volcanoes) caused geological formations (not catastrophes) Gradualism ○The mechanisms of change are constant over timeUniformitarianism○Observations of geological formations + rates processes occur = earth much older than a few thousand years ○Hutton (gradualism) & Lyell (uniformitarianism)•Catastrophism, Gradualism & UniformitarianismDarwin and Wallace developed the theory independently•Voyage of the HMS Beagle○Darwin•British naturalist in Indonesia○Wallace •Evolution by Natural SelectionThe unequal survival and reproduction of organisms due to environmental forces, resulting in the preservation of favorable adaptations•Process "selects" from what is available in the gene pool•Natural SelectionCh. 22 Descent with Modification: A Darwinian View of lifeMonday, June 09, 201410:53 AM E1 Notes Page 1Process "selects" from what is available in the gene pool•New characteristics are not created on demand•Selective breeding of organisms to encourage the occurrence of desirable traits•Provides evidence for natural selection•Artificial SelectionLadder of nature○Aristotle's scala naturae•Evolution not about climning "ladder of nature" from lower to higher•Evolution is a "bush" with lineages branching from one another•Trees vs. Scala NaturaeConcept 22.3 Evolution is supported by an overwhelming amount of scientific evidence Structures or other attributes in different species that resemble each other structurally, but not necessarily functionally, because of common ancestry○Homologous •Structures that are similar in function but NOT in structure and developmental and evolutionary origin ○Analogous•Homologous & Analogous StructuresAll vertebrates share similar developmental genes○Differences arise by some genes being switched on or off at varying times during development ○Vertebrate Embryos•DNA is universal genetic material○All life forms use approximately the same 20 amino acids to make proteins○All use ATP as the primary form of cellular energy ○All use RNA and ribosomes to make protein ○Biochemistry & Molecular Biology•Homologous structures: Similarity between 2 organisms, structures, or molecules due to independent evolution along similar lines rather than descent from a common ancestor○Similar in function, but not in structure□Ex. Bat wing and butterfly wing Analagous structures are the result of convergent evolution○Convergent evolution•Convergent EvolutionShow change in organisms through time•Past organisms differ from present-day organisms○Many species have become extinct○Oldest species are in the deepest layers of strata ○Change in types of organisms •Fossil Record E1 Notes Page 2One common misconception about evolution is that individual organisms evolve during their lifetime•Evolutionary processes (eg natural selection) acts on individuals, but populations evolve •The smallest unit of evolutionConcept 23.1: genetic variation makes evolution possibleMutation•Sexual recombination•2 main processes produce genetic variationSource of new alleles and genesChanges in nucleotide sequence of DNA○Mutations•Change in one nucleotide base in a gene○Point mutation•Delete, disrupt, or rearrange many genes on a chromosome○Chromosomal mutations•Duplication of whole segments of a chromosome○Gene duplications•Mutation(crossing over during prophase 1 of meiosis)○In sexually reproducing organisms, sexual recombination produces most of the variability in each generation •Sexual RecombinationEg flower color in pea plantsClassified on an either-or basis○Discrete characters•Eg height, weightVary along a continuum within a population○Quantitative characters•Variation within a populationConcept 23.2: The Hardy - Weibnberg equation can be used to test whether a population is evolvingA group of individuals of the same species living in a certain defined area○Population•PopulationsDescribes a population that is not evolving (ie, allele frequencies don't ○H-W equilibrium•Hardy-Weinberg EquilibriumCh. 23 The Evolution of PopulationsMonday, June 09, 201411:54 AM E1 Notes Page 3Describes a population that is not evolving (ie, allele frequencies don't change) ○No mutations○Large population size○No gene flow○No natural selection○Random mating ○5 assumptions behind H-W equilibrium•p = frequency of allele 1; q = frequency of allele 2○p + q = 1○Allele frequencies•P2 = frequency of homozygous dominant○q2= frequency of homozygous recessive○2pq = frequency of heterozygotes○p2+ 2pq + q2= 1 (H-W equation)○Genotype frequencies•Allele & Genotype FrequenciesConcept 23.3: Natural selection, genetic drift, and gene flow can alter allele frequencies in a populationStatistically, the smaller a sample, the greater the chance of deviation from a predicted result •With small population sizes, allele frequencies can fluctuate unpredictably from one generation to the next•Tends to reduce genetic variation •Genetic DriftGenetic additions to or subtractions from a population resulting from the movement of fertile individuals or gametes•Migration among populations •Tends to reduce variation among populations over time •Gene flowDifferential success in the reproduction of different phenotypes resulting from their interactions with the environment •Natural selectionThe contribution an individual makes to the hene pool of the next generation, relative to the contribution of other individuals ○Fitness•Evolutionary FitnessFavors individuals at one end of a phenotypic range○Directional•Favors individuals at both extremes of a phenotypic range○Disruptive•Favors
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