Descent with Modification: A Darwin View of LifeThe first “convincing” case of evolution was published by Charles Darwin in 1859Evolution is the transformation of life forms on earth over timeDescent with modificationEvolution is change over timeA change in the frequency of the alleles of a populationMutation which favors one allele over anotherMutation which creates a new allele that is favoredChange over a time period of generationsFor bacteria: a day or twoFor humans: maybe 200-300 yearsEvidence of evolutionChanges in phenotypesLook at the DNA(genotype)This is the fastest wayDarwin’s Ideas Were Opposed by Western PhilosophyCreationismAll species were created exactly as they exist todayMost popular hypothesisEuropean CultureCould be either strictly biblical or involve continual creationFossils and a Record of ChangeFossils are preserved remnants or impressions of an organism or something related to an organism that lived in the pastA succession of organisms is seen in the fossil recordThe differences between fossils and living species are profoundThese results were not used to support evolutionCatastrophismA theory, which states that the major changes in the earth’s crust are the result of catastrophic events rather than gradual process of changeA French anatomist, Georges Curvier, founded the Science of Paleontology in the late 1700sThe study of fossilsCurvier explained the layers of different species were caused by separate catastrophic eventsGeological Gradualism: The predecessor of evolutionIn the late 1700’s a, Hutton, proposed that the large changes seen in the fossil records were the result of uniformitarianism.The principle that profound change is the cumulative product of slow, continuous process.This was the first indication that the changes seen on earth were usually slowIf the changes were slow, then the theological timeline of 6000 years must be in errorChampioned by Hutton and CurvierPre-Darwinian Theory of EvolutionLamarck placed fossils in an evolutionary contextLamarck compared modern species to the fossil record and identified several line of descent consisting of a succession of:Older fossils younger fossils modern speciesin 1809 Lamarck’s comprehension model was publishedLamarck envisioned many “ladders” of evolution, which organisms could “climb”The least complex organisms at the bottom of the ladders were spontaneously generated.The complexity of organisms increased in a “march toward perfection” and the most complex organisms were at the top of the ladderThe mechanism of change involved two principles:Use and disuseUse it or lose it philosophyAcquired traits can be passed along to the next generationThese ideas turned out to be wrongDarwin and the VoyageCharles Darwin (1809-1882) was born the year Lamarck published his work on evolutionDarwin was a nationalistHe sailed on the voyage of the Beagle (1831)Observed that South American organisms differed form European formsSpecies of finches in Galapagos Islands were unique but resembled species of South AmericaDarwin’s work was preceded by the work of Wallace whose work in complete agreement with the hypotheses championed by DarwinThis work prompted a hesitant Darwin to complete the work he began years earlierDarwin’s observations lead to The Origin of Species published in 1859Was a much more detailed book. This is why we hear about Darwin and not WallaceDarwin used a tree as a metaphor for the history of lifeAt each branch or fork the species have a common ancestorSimilar species have branched recentlySpecies with greater differences branched long agoMost branches are dead endsNatural SelectionDarwin’s book focused on the role of natural selection in adaptationDarwin’s observations and their inferencesObservation 1: Populations have potential for exponential growthObservation 2: Population size is normally stableInference 1: survival is a struggle, only a fraction will surviveObservation 3: Traits are variable among individuals of a populationInference 2: Survival is not usually random, but is largely dependent upon heritable traitsSurvival of the fittestObservation 4: Most of those variable traits can be inheritedInference 3:Unequal survival of individuals will lead to gradual change in populationNatural Selection is the differential success in the reproduction of different phenotypes resulting from the interaction of organisms with their environmentNature picks the phenotypes that will surviveThe result of natural selection is the adaptation of organisms to their environmentThis adaptation is evolutionNatural selection occurs from the interaction between the environment and the variability of the populationVariations arise by chance (mutations)Environmental factors are defined by criteriaNatural selection is insured by and excess of offspring and variation in the populationSmall changes accumulated each generation can resultThe Evolution of PopulationsEvolution and PopulationEvolution is the change in gene frequencies in the populationPopulation is a localized group of individuals that belong to the same biological speciesThe smallest relevant evolutionary unitIndividuals don’t evolveEvolution measured by change in populationEvolution acts only on heritable traitsPopulations Show VariationsSome variation is the result of heritable changes (mutation and/or genetic recombination) and some variations is non-heritableVariation Between PopulationsPopulation of the same organism can show variations. This population variation can often be geographic. The variation between populations can be discrete or continualFrequently continual variation in a population will exist as a clineCline- a graded variation in a trait that parallels a gradient in the environmentThe Integration of Darwinism (evolution) and MendelismWhen the field of evolution (and the study of populations) merged with genetics, the science of population genetics was formedPopulation is the unit of evolutionNatural selection is the primary mechanism for evolutionary changePopulation Genetics is the study of how populations change genetically over timeA Population Has a Genetic Structure Defined By Its Gene PoolThe genes in a population make up the gene pool for that populationGene Pool is the total aggregate of genes in a population at any one timeAll the alleles at all loci for all individuals in a populationMost alleles in the gene pool will be combined to produce the next generationIf you add up all the
View Full Document
Unlocking...