Introduction to Evolution and the Scientific ProcessEvolution by Natural SelectionNylon1935- inventedA novel, non-organic material1975- nylon eating bacteria discoveredMalariaKills 3 million each year17th century- Quinine20th century- Chloroquine21st century- Quinine and othersShow things develop across time, evolution of resistanceEvolutionMean change, literally “unfolding”Charles Darwin- evolution is “descent with modification”Process: Contemporary species have arisen from a succession of ancestorsMechanism: natural selection (Darwin famous for)Species has branches which branch off from the original ancestral lineNatural selection: a population of organisms can change over successive generations if individuals having certain heritable traits that make them more likely to survive and successfully reproduce, leave more offspring than organism with traits that hinder their existenceEvolution of “super bugs”If:Variation: individuals in a population (a group of organisms of the same species living together in the same geographic area) vary in character valuesDifferential Fitness (relative ability of an organism to survive and reproduce): individuals with different character values have different propensities to survive and reproduceThen:Selection: the frequencies of individuals with different character values will changeAnd if:Inheritance: the character values of parents and offspring are correlatedThen:Evolution: Frequencies of individual with different character values will change between generationsAdditional conditions:Struggle for existence: many more individuals must be born than can survive for this process to work efficientlyEX: BeetlesVariation (different colors)Differential fitness (predators eats individuals with certain traits i.e. white)Selection (environmental pressure, mostly non-white beetles left)Inheritance (reproduction of survivors)Evolution (next generation of beetles has higher frequency of traits that enhance survival and reproductive fitness/higher differential fitness)Evolution is a historical process and does not entail:DirectionalityUnfolding of any predetermined patternsInaccurate: Evolution is JUST a theoryThe common use of the term theory implies speculation or assumption that has not been verified or has limited proofThe scientific definition of a theory is a set of statements devised to explain a group of facts or phenomena, has been repeatedly tested, is widely accepted, and can be used to make predictions about natural phenomenaLaw: an established principle thought to be universal and invariable (based of empirical evidence)Darwin’s accomplishmentsEstablishing the fact of evolutionProposing a theory of natural selection to explain the mechanism of evolutionIs there a conflict between evolution & religion?Can coexistReligion doesn’t belong in science class because can’t be tested with the scientific processEvolution deals with the origin of species NOT the origin of lifeHistoryEvolution was around before Darwin, he put the theory togetherDarwin’s theory requires:Time for gradual change to occur overEver present mechanism is now and has always been operatingMany more individuals born than surviveVariation: “population” thinkingCharacters are heritable (later demonstrated by Mendel)BuffonStudied fossils and suggested similar environments, different regions have distinct plants and animalsEarth is older than was thought (iron cooling)Similarities between particular fossils and living animals, but not exactly alikeConcluded that types of animals not “created” for specific types of environmentEarth much older than 6,000 yearsFossil forms are ancient versions of living speciesLamarckSuggested explanation for Buffon’s finding was live evolvedHypothesis: Progress towards increasing biological complexity (evolutionary process) caused by acquired inherited characters (mechanism) > incorrectHuttonUniformatarianism: the same natural laws and processed that operate today have always operated in past and apply everywhere in the universeLyellGradualism: small changes over long periods of time can have big resultsMalthusInterested in population sixe and its increase or decrease in response to various factorsPopulations SHOULD grow exponentially, but there are malfusion parameters (food sources, water, etc.) which checks human population growth when widespread mortality occursWallaceDecided Malthus’ theories must also be true for other organismAsked what allowed some to survive?Darwin5 year journey on the HMS BeagleGalapagos Islands had specific animal species’ with slight variationsMay or may not have borrowed from WallaceAchieved four things:Documented the fact of evolution beyond reasonable doubtProposed natural selection as the first plausible explanation for adaptationIntroduced population thinking to biologyPresented testable hypothesesSee lecture slides for summary of historyMicroevolutionary ProcessesMicroevolution (small)The change in gene frequencies of a population from one generation to the nextOften associated with adaptationMacroevolution (big)The descent of different species from a common ancestor over many generationsMajor changes in history of lifeOrigin of new speciesMicroevolution: change of gene frequencies over timeGene frequency- the frequency of occurrence of an allele in relation to that of other alleles of the same gene in a populationPopulationAdaptationAnalyzing gene frequenciesAllele- an alternative form of a geneGene- a discrete unit of hereditary info consisting of a specific nucleotide sequence in DNAGenotype- the genetic makeup of an organismPhenotype- the expressed trait of an organismH-W- Equilibrium (when a population is NOT evolving)Allele and genotype frequencies do not change over generationsTypes of natural selectionDirectional selectionNatural selection that favors individuals on one end of a trait rangeStabilizing selectionNatural selection that favors intermediate variants by acting against individuals with extreme traits, stabilizes meanDiversifying selectionNatural selection that favors individuals with extreme over intermediate trait valuesCould be beginning process leading to speciation (two new species)Sexual selectionNatural selection on traits related to obtaining mates for sexual reproductionGenetic drift: a change in the gene frequencies of a population from one generation to the next due to chance, operates more often in small populationsBottleneck effectGenetic drift resulting
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