2 BIOLOGY EOC BENCHMARKSC.912.L Describe the conditions required for natural selection, including: overproduction of offspring, inherited variation, and the struggle to survive, which result in differential reproductive success.
4 Convergent Evolutiondifferent organisms that live in similar environments become more alike in appearance and behavior.environment selects similar adaptations in unrelated species.Organisms develop analogous structures (same function, but different origins)
5 Coevolution two species evolve together. There is a mutual evolutionary influence between two species.The species have a symbiotic relationship (interaction between members of two populations).Example: - Birds and flowers
6 Divergent Evolutionancestral species gives rise to a number of new species that are adapted to different environmental conditions and are less alike.Often occurs when a species colonizes a new environment.Also known as adaptive radiation.
7 THE EVOLUTIONS OF POPULATIONS THERE ARE FOUR MECHANISMS THAT CAN GIVE RISE TO EVOLUTION:MUTATIONGENETIC DRIFTMIGRATION (Gene Flow)4.NATURAL SELECTIONGreatly and quickly seen in isolated populations like those on islands.- Allele frequency will change over generations; situations/ENV willfavor one allele over another- Those populations at equilibrium are not evolving- Species with more genetic diversity will adapt better to environmental changes
8 GENETICS OF WHITE BENGAL TIGERS In nature, White Bengal tigers arises from the mating of two Bengal tigers with recessive genes for the white color of fur. The gene is recessive has the effect that offspring (cubs / kittens) only become white if they inherit the recessive gene from both parents.It is the same principle as with brown and blue eyes. The inbreeding producing all these White tigers is neither good nor healthy for the tigers. In nature White tigers have, at least theoretically as there probably arent any, a less chance of surviving than normal colored tigers due to their lack of camouflage compared to the normal Yellow Tigers.Below is a very simplified illustration (Fig 1) of how the transfer of genes coding for fur color works. Consider to yellow Bengal Tigers mating. If they are both carriers of the recessive gene there's a 25 percent chance that their cubs will be white. If a white and a yellow Bengal tiger mates there's a 50 percent chance that the offspring will be white. The chances of getting more White tigers can be enhanced by letting tigers that are related mate. This is however the definition of inbreeding.
9 THE EVOLUTIONS OF POPULATIONS TIGER POPULATIONAllele frequencies:Proportion of orange fur-pigment alleles in the populationProportion of white fur-pigment alleles in the populationEvolution is a change in the allele frequencies of a population over time. For example, a change in the proportion of pigment alleles in the population of tigers means that evolution has occurred.
10 MUTATION #1 A mutation can create a new allele in an individual. When this happens, the population experiences a change in its allele frequencies and, consequently, experiences evolution.#1EVOLUTIONARY CHANGE: MUTATIONMECHANISMSOFEVOLUTIONMutagenDNANormal base-pair sequenceMutated base-pair sequenceNormal proteinMutated proteinDespite mutation’s vital role in the generation of variation, mutations almost always cause early death or lower the reproductive success of an organism.NormalphenotypeMutatedphenotype
11 Mutations Are rare because you have self correcting enzymes Natural Process that produces genetic diversityNot all mutations are badSome won’t affect the body at allBlood types/ear lobesSome are advantageous(thumb)Brain Pop: Genetic Mutations
12 COMPUTER ACTIVITY: Sex and the Single Guppy The purpose of this activity is to analyze how guppy populations change over time. The simulation activity allows you to start with a pool of guppies and your choice of predators, you will be able to watch what happens to your guppy population and how the introduction of predators can affect the guppy's appearance. The simulation will help you understand what pressures drive guppy evolution.
13 MECHANISM FOR EVOLUTION - GENETIC DRIFT population can experience random changes in allele frequency that do not influence reproductive success which leads to evolutionPOPULATION BEFOREGENETIC DRIFTAllele frequencies:cleft chin (dominant)smooth chin (recessive)Neither allele is related to reproductive success. Inheritance is based solely on chance.REPRODUCTIONIn this example, a heterozygous couple (Cc) could have two children that are homozygous recessive (cc), causing an increase in the proportion of recessive alleles in the population.POPULATION AFTER GENETIC DRIFTThere are now more recessive alleles in the population than before.FIXATIONGenetic drift leads to fixation when an allele’s frequency becomes 100% in a population. If this occurs, there is no longer genetic variation for the gene.
14 GENETIC DRIFT - FOUNDER EFFECT The founding members of a new population can have different allele frequencies than the original source population and, consequently, the new population experiences evolution.SOURCE POPULATIONAllele frequencies:5 digits per hand(recessive)>5 digits per hand(dominant)A group of individuals may leave a population and become the founding members of a new, isolated population.AMISHNEWLY FOUNDED POPULATIONThe new population will be dominated by the genetic features present in the founding members.
16 GENETIC DRIFT - BOTTLENECK EFFECT Occasionally, famine or disease or rapid environmental change may cause the deaths of a large, random proportion of the individuals in a population.SOME CATASTROPHESOURCE POPULATIONEXTREME AND RAPID ENVIRONMENTAL CHANGENEW POPULATIONThe new population will be dominated by the genetic features present in the surviving members.All cheetahs living today can trace their ancestry back to a dozen or so individuals that happened to survive a population bottleneck about 10,000 years ago!Unless more individuals are introduced to the population, mating options will be limited thus decreasing variation in the gene pool (decreasing genetic diversity).
18 #3MECHANISMSOF EVOLUTIONMIGRATIONAfter a group of individuals migrates from one population to another, both populations can experience a change in their allele frequencies and, consequently, experience evolution.MIGRATION (GENE FLOW)1 BEFORE MIGRATIONTwo populations of the same species exist in separate locations. In this example, they are separated by a mountain range.Population 1Population 2
19 #3MECHANISMSOF EVOLUTIONMIGRATIONAfter a group of individuals migrates from one population to another, both populations can experience a change in their allele frequencies and, consequently, experience evolution.MIGRATION (GENE FLOW)2 MIGRATIONA group of individuals from Population 1 migrates over the mountain range.Population 1Population 2
20 #3MECHANISMSOF EVOLUTIONMIGRATIONAfter a group of individuals migrates from one population to another, both populations can experience a change in their allele frequencies and, consequently, experience evolution.MIGRATION (GENE FLOW)3 AFTER MIGRATIONThe migrating individuals are able to survive and reproduce in the new population and they may experience evolutionary changes from population 1.Population 1Population 2
21 #4 3 Conditions that must occur for Natural Selection Mechanism of EvolutionNatural Selection#41. VARIATION OF A TRAIT IN A POPULATIONThe tiniest dog in a litter has reduced differential reproductive success. Its more robust siblings prevent access to the food it needs to grow and thrive.2. The trait must be inheritable3. One version of the trait must be in greaterabundance than a different version of the trait.
22 Natural Selection There is indirect and direct evidence of I. Indirect – we find it, not witness itII. Direct – we are witness to the development ofWill be seen when there is:Over populationInheritance variationStruggle for survival (abiotic factors too)Evidence:Fossils EmbryosComparative Anatomy 5. BiogeographyAdaptation Field/lab Experiments
23 ? How long can a fruit fly survive without food? “SURVIVAL OF THE FITTEST”—ONLY THE ‘BEST’ FLY WILL SURVIVE AND BE ABLE TO REPRODUCE AND PASS IT’S GENES ON TO THE NEXT GENERATION.IT IS THEN SAID TO BE ‘FIT’-THIS IS NATURAL SELECTION.
24 AVERAGE STARVATION RESISTANCE The average fruit fly can survive about 20 hours without food.Number of fliesGENETICALLY‘UNFIT’” FLYA MORE GENETICALLY ‘FIT’ FLYHours until starvation
25 THE EXPERIMENT1 INITIAL SETUPStart with a cage that contains a large number of fruit flies (5,000), and remove the food.= 500 fruit flies2 TESTING STARVATION RESISTANCEWait until 80% of the flies starve to death, then return the food to the cage. Record the average starvation-resistance time.Food removedFood returnedEggsOnly the most starvation-resistant flies live to lay eggs.New generationCan fruit flies evolve so that they can resist starvation longer? Canwe see Natural Selection at work? (YES)?3 START NEW GENERATIONAfter the surviving flies eat a bit, collect the eggs those flies lay and transfer them to a new cage.
26 THE RESULTS GENERATION 1 Average starvation resistance: 20 HR. Number of fliesHours until starvationGENERATION 2Average starvation resistance: 23 HR.Number of fliesHours until starvationExperiment continues through 60 generations.GENERATION 60Average starvation resistance: 160 HR.---this is evolution (change) at workNumber of fliesOver many generations of natural selection, the population changes! The flies now resist starvation much longer.Hours until starvation
27 Natural SelectionIndividuals with favorable traits are more likely to leave more offspring better suited for their environmentExample:English pepperedmoth (Biston betularia)Peppered Moth Lab
31 BIOGEOGRAPHY: HONEYCREEPERS--- Evidence of NS: AdaptionThe honeycreepers of Hawaii have adapted to a wide range of habitats, yet still closely resemble a finch-like shared ancestor found nearly 2,000 miles away---the major difference is the bill .BIOGEOGRAPHY: HAWAIIAN HONEYCREEPERSMainland finch(probablesharedancestor)’Akeke’ehoneycreeperMaui Parrotbillhoneycreeper’I’iwihoneycreeperBIOGEOGRAPHY: HONEYCREEPERS---A MODERN DAYDARWIN’S FINCHSCENARIO
32 Evidence of NS: biogeography Sugar glider Numbat Tasmanian wolf BIOGEOGRAPHY: AUSTRALIAN MARSUPIALS AND THEIR PLACENTAL COUNTERPARTSAUSTRALIAN MARSUPIALSSugar gliderNumbatTasmanian wolfPLACENTAL COUNTERPARTSGray squirrelGiant anteaterGray wolfThough less related to each other than you are to a shrew, these marsupials and their placental counterparts (both mammals) have come to resemble each other as natural selection has adapted them to similar habitats.
33 EVOLUTION BY NATURAL SELECTION: A SUMMARY 1 VARIATIONFOR A TRAITDifferent traits are present in individuals of the same species2 HERITABILITYTraits are passed on from parents to their children.3 DIFFERENTIAL REPRODUCTIVE SUCCESSIn a population, individuals with traits most suited to reproduction in their environment generally leave more offspring than individuals with other traits.MECHANISMSOF EVOLUTIONNATURAL SELECTIONWhen these three conditions are satisfied, the population’s allele frequencies change and, consequently, evolution by natural selection occurs.
34 Running speed in rabbits can vary from one individual to the next. NATURAL SELECTION IN NATURERunning speed in rabbits can vary from one individual to the next.1 VARIATION FOR A TRAITSpeedThe trait of running speed is passed on from parents to their offspring.2 HERITABILITYIn a population, rabbits with slower running speeds are eaten by the fox and their traits are not passed on to the next generation.3 DIFFERENTIALREPRODUCTIVE SUCCESS
35 EVOLUTION OF ANTIBIOTIC RESISTANCE When first used as medicine in the 1940s, penicillin was uniformly effective in killing the bacterium Staphylococcus aureus. Today, natural selection has led to an increase in antibiotic-resistant alleles, and humans are increasingly at risk from untreatable Staphylococcus infections.(this is ongoing evolution taking place right now )Most of the Staphylococcus is killed.StaphylococcusVery little of the Staphylococcus is killed.PenicillinKill zone1940sToday
36 A single species of grass is planted on a golf course A single species of grass is planted on a golf course. On the putting greens, it is cut very frequently / on the fairways it is cut only occasionally / in the rough it is almost never cut at all.EVOLUTION IN PROGRESS: GREEN GRASS ON A GOLF COURSEOver the course of only a few years, grass plants from the same stock had developed into three distinct populations as a result of the frequency at which they were cut.RoughFairwayPutting greenSELECTIVEPRESSUREMonthly mowingscheduleLIFE IS SHORTSO MUSTREPRODUCERAPIDLYWITH LARGESEEDPRODUCTIONSEXUALMATURATIONSLOWESTSLOWRAPIDSEEDPRODUCTIONLOWESTLOWHIGH