Chapter 14The Unifying theme of BiologyEvolution, or the change over time in the characteristics of populationEvolution by Natural Selection is a unifying theme for all biologyNatural Selection:Drives evolutionIndividual advantageous traits are going to live longer and produce more offspringActs on variation already presentLeads to changes of the genetic makeup of a populationContributors to evolutionary thinking (Cuvier, Darwin, Lyell, Lamarck)Charles Darwin The main ideas of evolution were not widely accepted until after Darwin published On the Origin of Species in 1859.“Father of Evolution”During natural selection, individuals with advantageous straits (that are heritable) survive longest and produce most offspring.Noticed different islands were home to distinct, yet similar animalsServed as the official naturalist on the HMS Beagle during a 5 year expedition around the worldObserved things like:Snakes with vestigial hind limbsPenguins use their wings to paddle not flySnakes with no rattle still vibrate tailsJean Baptiste LamarckObservation:Older fossils are simpler than younger onesYounger fossils were more like current speciesHypothesis:Individuals acquire characteristics through use or disuse of body partsThese acquired characteristics are passed onAcquired characteristics are not inheritedGeorge CuvierFrench paleontologist. Accounted for extinct species while preserving the notion of a single creation by GodCatastrophismMultiple catastrophes in a short period produced many layers of rock and destroyed many speciesKnown: Flooding rivers put down sediment layers and volcanoes put down basalt.Charles Lyell-Suggested that the forces that formed layers of rock and sediment are due to the same forces occurring today and that they happened repeatedly over long periods of time.Uniformitarianism- Earth present landscape was produced by past action of the same gradual geologic process that we observe today.Theory of Evolution- Four postulates about populations1. Individual members of a population differ from one another in many ways2. At least some of these differences are due to heritable traits (can be passed from parent to offspring)3. In each generation, some individuals survive and reproduce and some do not4. individuals with advantageous traits survive the longest and leave the most offspring:NATURAL SELECTION!!Postulate 1: Individuals in a population varyVariation is the result of random mutationsEach organisms exact DNA sequence is uniquePostulate 2: Traits are passed on to offspringDarwin and Wallace had no proof except the observation that offspring resemble their parents.Mendel’s later work demonstrated that heritable traits can be passed from parent to offspringPostulate 3: some individuals fail to survive and reproducePostulate 4: Survival and reproduction are not determined by chance.Survival depends on characteristics of an individualNatural Selection- individuals with the most advantageous characteristics survive the longest and produce the most offspringModifies populations over timeAffects whether of not an individual survives to reproduce but eventually has consequences for the population as a whole“Survival of the fittest”Evidence of evolution: fossils comparative anatomy, embryological similarities, biochemical and genetic analysis1. Fossils provide evidence of evolutionary change over time2. Comparative Anatomy evidence of descent with modificationHomologous, Analogous, and Vestigial Structures3. Embryological Similarity suggests common ancestryRelated organisms undergo similar embryonic developmentEx. All vertebrate embryos develop tails and gill slits (Fig. 14.11)Only some retain gills/tails as adults4. Biochemical and genetic analysis reveal relatedness among diverse groupsBiochemical Similarities between all cellsDNA is the genetic materialRNA and ribosomes for protein synthesisUse most of the same 20 amino acidsUse ATP as a cellular energy carrierMolecular HomologiesSimilar DNA sequences in genes that encode for similar proteins (Ex. Cytochrome c gene)Homologous, Analogous, and Vestigial StructuresHomologous StructuresSimilar internal anatomy with different functionsi.e. Bat wing and a mouse armHomologous structures have similar anatomy presumably because the organisms descended from common ancestryVestigial StructuresNo purposeTailbone/wisdom teeth/ arrector Pilli muscleAnalogous StructuresSame function but different internal anatomyi.e. Bat wing and butterfly wingSome anatomical similarities result from convergent evolutionThrough natural selection, structures that serve similar functions resemble one anotherBe able to identify Homologous, analogous, and vestigial structures (Figs. 14.8-14.10)Study of guppies in Trinidad – Dull v. Brightly-colored guppies (different selective forces)Guppies in streams on the island of Trinidad shown in Fig. 14.14Upstream-too shallow for predatorsBrightly colored male guppies are selectedDownstream- predators presentDull-colored male guppies are selectedPredators act as a agent for natural selectionBrightly colored males are eaten before they can reproduceAnole Lizards in the BahamasAnole lizard leg size changes in response to a different environmentOriginal population- longer thicker legs favored greater speed, but less agilityScientists released these lizards in an environment where agility was important14 years later the lizard population had developed shorter thinner legsRandom or non-random variations of individuals; individuals favored by natural selection1. Variation in population upon which natural selection works, are caused by mutations (random)2. Natural Selection favors organisms that are best suited for a particular environment (not random)a trait that is advantageous under one set of conditions may be disadvantageous under different conditionsArtificial SelectionThe breeding of domestic plants and animals to produce specific desirable features.QUESTIONS FOR CHAPTER 141. How did Cuvier, Lyell, Lamarck, Darwin and Wallace contribute to evolutionary thinking?Cuvier accounted for extinct species while preserving the notion of a single creation by God.Catastrophism – multiple catastrophes in a short period produced many layers of rock and destroyed many species.Lyell suggested that the forces that formed layers of rock and sediment are due to the same natural forces occurring today and that they happened repeatedly over long periods of time.Uniformitarianism – Earth present landscape was
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