3Charles Darwin HMS Beagle Born in England in 1809 LT 1HMS BeagleBorn in England in 1809A Naturalist (studied nature)Took a 5yr voyage on a ship called the HMS Beagle to study the organisms encountered on the journeyTraveled to the Galapagos Islands near S. AmericaHere he made many observations about the organisms he saw there; including tortoises and finches
4Darwin’s Observations Each island of the Galapagos have a different climate.Found that tortoises had different shells depending on the island they inhabitedFound that finches had different beaksHe also found fossils similar to living organisms and some like he had never seen before
5The Ride HomeAfter leaving the Galapagos Islands, Darwin had a few questions.Why do organisms have differences based on their habitat?Why had so many species disappeared?How are they related to those still living?Were similar organisms formerly the same species?
7LT 2Other Old Dead DudesDarwin, being a good scientist, studied the works of other scientists in and outside of his field.MalthusHMS BeagleEconomistDarwinHuttonLamarckNaturalistLyellGeologists
8What everyone else thought What Darwin ConcludedCharles DarwinWhat everyone else thoughtFrom Hutton and Lyell:If the Earth can change, can life also change?Geological processes take a long time, therefore the Earth must be old.From Malthus:That organisms will have more offspring than will die and this will lead to competition.Not all offspring live so what makes some survive and othersdie?The Earth was made as it was now and did not changeThe Earth is only a few thousand years oldOrganisms don’t change**Darwin’s conclusions caused a BIG buzz**
10That Other Guy Jean Baptiste Lamarck All living things change over timeLiving things descend from other living thingsOrganisms adapt to their environmentSelective USE or DISUSE of organs will cause organisms to gain or lose the trait during their lifetimeTraits lost or gained will be passed onto the organism’s offspring.Loss or acquisition of a trait is to move toward being perfect and better suited for their environmentsJean Baptiste Lamarck
13Darwin’s IdeaKnowing that his ideas were not going to be well received, Darwin wrote a book called On the Origin of Species, but did not publish it for a long time.His idea was…Natural Selection (nature “selects” organisms to survive based on the most favorable trait for the environment)Every species has variations within a trait and the variations are IMPORTANTSome of the traits were inheritableThose organisms that have favorable traits (ADAPTATIONS) will survive and go on to have more offspring (FITNESS)SURVIVAL OF THE FITTESTOver many generations, an adaptation could spread throughout the entire species.In this way, according to Darwin, evolution by natural selection would occur.
15Noodle Worms Post “Noodle Worm Lab” we can say… Variations do exist within the population(green, orange, white worms)-Where did it come from? Why Genetics, silly!Some worms did struggled to survive.Those that did live were best suited or “most fit” and possess a color characteristic that makes them more likely to survive.Those that survived can pass their characteristic to the next generations (a.k.a descending with modifications)
16Variations So do variations exist in all populations? How do they go from parent to offspring?MeiosisCells copy DNACrossing over events take placein Prophase IFertilization from SEXUAL reproductionEgg + SpermIndividual sets of chromosomes combine to form offspring with features unique from either parent
18Variations Mutations Give new genetic material to the gene pool By Chance, radiation, and chemicalsGive new genetic material to the gene poolGenetic DriftMigration/Gene FlowAll of these forces change GENOTYPES, PHENOTYPES, and determine the amount of GENETIC VARIATION
20VariationsGene pool – all members of an interbreeding population who bring genetic variety to the population.So all the BB, Bb, or bbin the buffalo herd Relative frequency – percentage of time a particular allele appears in the gene pool compared to other allelesWhat is the % of B’s to the % of b’s in the buffalo herd
22Putting It All Together Evolution(Darwin)1859Genetics(Mendel)Mid 1800’sDNA(Watson & Crick)1963Current Understanding of Biological Evolution
23Putting It All Together Okay, then…so,Based on the Mouse WS and the Moths Activity,Evolution – a change in the relative frequency of alleles in a population over timeEvolutionary fitness – the success with which an individual can pass their traits to the next generationTherefore, POPULATIONS, NOT INDIVIDUALS, evolve
24Putting It All Together Evolution NEVER acts DIRECTLY on ONE GENE.Evolution works on the entire organismIf the organism has evolutionary fitness andReproduces = gene(s) in the gene poolDoes not reproduce = NO gene(s) in the gene pool
25NS on a Single Gene Trait Single gene trait – one gene controls a trait.Only two phenotypes (Widow’s peak or no widow’s peak)Three genotypes (WW, Ww or ww)Two alleles (W and w) in this exampleNatural selection can work oneach phenotype and changethe allelic frequency
26NS on a Polygenic TraitPolygenic Trait- when a trait is controlled by more than one geneA range of phenotypes (a bell curve)Many genotypesAt least two alleles per geneNatural selection effect is morecomplexfitness of individual close oncurve is similarfitness of individuals furtherapart is varied. This is whereNS can act.
27NS on a Polygenic Trait Three Effects on Phenotypes Directional Selection - when one end of the curve has higher fitness than the middle or other end of the curve*Shifts thecurve leftor right*Peccaries eat cacti. Cacti with fewer spines are eaten first. Thus, the cacti with more spines fair better . NS moves the curve toward cacti that make many spines
28NS on a Polygenic Trait2. Stabilizing Selection – when individuals in the middle of the curve have higher fitness than those on the ends. *Narrows the graph*Peccaries continue to eat the cacti with few spines (left of graph). A parasitic insect lays its eggs at the cacti spine base and therefore loves cacti with lots of spines (right of graph). Both extremes are NOT fit. Being in the middle is best
29NS on a Polygenic Trait3. Disruptive Selection – when individuals at the upper and lower ends of the curve have higher fitness *Creates 2 peaks in graph /phenotype*A road through the desert brings tourists that love to pick cacti as souvenirs. Too few spines on the cacti look bad and too many spines are hard to pick. Thus, cacti with spine numbers in the middle are picked.
30Other Factors of Evolutionary Change 4. Genetic DriftVariation(crossing over, meiosis, sexual reproduction, and mutations)5. MigrationNatural SelectionNote…NS does not create variation, it just works on itEvolutionary Change
31Genetic DriftLT 6Genetic drift – is evolution BY CHANCE!; changes in a population that result from random chance or “luck”Luck ≠ evolutionary fitnessLuck ≠ “better”Affects all populationsNatural selection produces adaptations, Genetic Drift does notGenes of one generation do not wind up in identical ratios in the next generation, but…it’s still evolution!
32Genetic Drift By random chance, the brown frogs die Their genes are thus unable to be passed to the next generationThus the gray and greens are the only ones able to mate and pass on genes.Variation is thereby decreased
33Genetic Drift Effects of Genetic Drift: A decrease in variation within a population/change in the relative frequencyMay decrease a populations ability to respond to selection pressuresActs FASTER and is more DRAMATIC in small populationsVery bad for rare or endangered speciesCan cause new species to emerge
34Genetic DriftPopulation bottleneck – a decrease in population size for at least one generationCauses a decrease in variationWorse for small populations (even if for a short time)Makes responding to selective pressures harderCauses:OverhuntingEnvironmental Disaster (hurricane, flood, etc)Habitat Destruction
35Genetic DriftFounder Effect – when a portion of an original population breaks off and form a new population.Also decreases variability because the small group may not be equally representative of the larger population’s variability
36When does this happen? Under what conditions? Hardy-WeinburgLT 7Recall that evolution -is the change in the relative frequency of alleles in a population over time.VersusGenetic equilibrium - No evolution – no changes in the relative frequencyWhen does this happen? Under what conditions?
37Hardy-WeinburgA: The relative frequency of alleles in a population will remain constant UNLESS 1 or more factors cause the frequency to change.Five Conditions for GE:Random Matingequal opportunity for all member to produce young.This is rarely random!The population is largethis decrease the effects of genetic drift
38Hardy-Weinburg No immigration or emigration No mutations Immigration = new individuals move in and bring new alleles and varietyEmigration = individuals leave the population and take allelic variety with themNo mutationsNo natural selectionAll genotypes have equalprobability for survival
39Hardy-Weinburg p2 + 2pq + q2 = 1 p + q = 1 Where p = dom. allele freq For some populations these conditions are met, or nearly met, for long periods of time.Conditions met = genetic equilibriumConditions not met = evolutionThere are two equations that can be used to show changes.p2 + 2pq + q2 = 1p + q = 1Where p = dom. allele freqand q = rec. allele freq
40Geologic Time & Evidence for Evolution LT9-13Please see the Guided Reading Posted to the website for the answers and “notes” for Geologic Time and Evidence for Evolution (LT 9-13)
41CladogramsLT9-13Let’s see one madeCladogram – a diagram that shows evolutionary relationships among groupsBased on phylogeny (the study of evolutionary relationships)Sometimes called a phylogenic tree (although the two vary slightly)Cladistics - the practice of looking at “innovations,” or newer features, that serve some kind of purposeDerived characteristics – new features that appear in later generations but not earlier ones
42Cladogram1. ______ Wings 2. ______ 6 Legs 3. ______ Segmented Body 4. ______ Double set ofwings 5. ______ Jumping Legs 6. ______ Crushingmouthparts 7. ______ Legs 8. ______ Curly Antennae
43CladogramsTo make a cladogram, you must first look at the animals you are studying and establish characteristics that they share and ones that are unique to each group. For the animals on the table, indicate whether the characteristic is present or not. Based on that chart, create a cladogram like the one pictured above.CellsBackboneLegsHairOpposable ThumbsTigerSlugFrogCatfishHuman
45Extinction 99% of all life that has ever existed is now extinct LT1599% of all life that has ever existed is now extinctmass extinctions have occurred many times in the Earth’s historyExtinctions indicate…Organisms who were selected against by natureA failure to adaptA collapse in an organism’s environment they could not help
46ExtinctionWhat becomes of those organisms that live (evolutionarily speaking, of course)?When large groups of organisms die, it leaves habitats and niches open for others to move into.New habitats can also have new selective pressures that will work on organisms.This could cause evolution within a species ORAdaptive radiation – a species has evolved from a common ancestor into diverse forms that live in different ways
47Types of EvolutionLT16A. Divergent Evolution-when selective pressures cause two species to form (think speciation)B. Convergent Evolution-takes place when species of different ancestry begin to share similar traits because of a shared environment or other selection pressure.C. Co-evolution- organism of different species but have a close relationship and evolve together
48Rates of EvolutionLT17Darwin believed evolution was a SLOW process; Gradualism Modern Biologist think that some evolution is slow and other times long periods of equilibrium are followed by RAPID evolution-Punctuated Equilibrium