February 13 B Day• Test: Chapters 18, 19, 20Coming up……………• Parade of Kingdoms due 2/23

- Don’t wait until the last minute, study each chapter – there will be multiple quizzes and a test at the end.

•Be ready for the Drosophila lab and the Transformation lab so we can start as soon as the live materials are in - highlight important points.

EVOLUTION & EVOLUTION & SPECIATIONSPECIATION

• PopulationPopulation: : a a localized group of localized group of individuals belonging individuals belonging to the same speciesto the same species

• SpeciesSpecies: : a group of a group of populations whose populations whose individuals have the individuals have the potential to interbreed potential to interbreed and produce fertile and produce fertile offspringoffspring

• Gene poolGene pool: : the total the total aggregate of genes in aggregate of genes in a population at any a population at any one timeone time

• Population geneticsPopulation genetics: : the study of genetic the study of genetic changes in changes in populationspopulations

• Modern synthesis/neo-Modern synthesis/neo-DarwinismDarwinism

““Individuals are selected, Individuals are selected, but populations evolve.”but populations evolve.”

Gene PoolGene PoolCombined Combined

genetic info. of genetic info. of all membersall members

Allele frequency Allele frequency is # of times is # of times alleles occuralleles occur

Variation in Variation in PopulationsPopulations2 processes can 2 processes can

lead to this:lead to this:

MutationsMutations - -change in DNA change in DNA sequencesequence

Gene ShufflingGene Shuffling – – from sexual from sexual reproductionreproduction

Genetic Drift changes Genetic Drift changes populations…….populations…….•Random change in allele Random change in allele

frequency causes an allele to frequency causes an allele to become commonbecome common

MicroevolutionMicroevolution• The Bottleneck The Bottleneck

EffectEffect: type of : type of genetic drift genetic drift resulting from a resulting from a reduction in reduction in population (natural population (natural disaster) such that disaster) such that the surviving the surviving population is no population is no longer genetically longer genetically representative of the representative of the original populationoriginal population

MicroevolutionMicroevolutionFounder Effect:Founder Effect: a cause a cause of genetic drift of genetic drift attributable to attributable to colonization by colonization by a limited a limited number of number of individuals from individuals from a parent a parent populationpopulation

MicroevolutionMicroevolution• Gene FlowGene Flow: :

genetic exchange genetic exchange due to the due to the migration of fertile migration of fertile individuals or individuals or gametes between gametes between populations populations (reduces (reduces differences differences between between populationspopulations

MicroevolutionMicroevolution• Nonrandom matingNonrandom mating: inbreeding and : inbreeding and

assortive mating (both shift assortive mating (both shift frequencies of different genotypes)frequencies of different genotypes)

MicroevolutionMicroevolution

• Natural Natural SelectionSelection: : differential differential success in success in reproduction; reproduction; only form of only form of microevolution microevolution that adapts a that adapts a population to its population to its environmentenvironment

SPECIATION - formation new SPECIATION - formation new speciesspecies

- - AnagenesisAnagenesis (phyletic evolution): (phyletic evolution): accumulation of heritable accumulation of heritable changes changes

- Cladogenesis (branching evolution): budding of new species from a parent species that continues to exist (basis of biological diversity))

Evolution of PopulationsEvolution of Populations

Occurs when Occurs when there is a there is a change in change in relative relative frequency of frequency of allelesalleles

• Tempo Tempo of speciation: gradual vs. of speciation: gradual vs. divergence in rapid bursts; Niles divergence in rapid bursts; Niles Eldredge and Stephen Jay Gould Eldredge and Stephen Jay Gould (1972); helped explain the non-(1972); helped explain the non-gradual appearance of species in the gradual appearance of species in the fossil recordfossil record

Punctuated Punctuated equilibriumequilibrium

Population variationPopulation variation• Polymorphism:Polymorphism:

coexistence of 2 coexistence of 2 or more distinct or more distinct forms of forms of individuals individuals (morphs) within (morphs) within the same the same populationpopulation

• Geographical Geographical variation:variation: differences in differences in genetic structure genetic structure between between populations (cline)populations (cline)

VariationVariation PreservationPreservation

• Prevention of natural Prevention of natural selection’s reduction of selection’s reduction of variationvariation

• DiploidyDiploidy 2nd set of 2nd set of chromosomes hides chromosomes hides variation in the variation in the heterozygoteheterozygote

• Balanced polymorphismBalanced polymorphism 1- 1- heterozygote advantage heterozygote advantage (hybrid vigor; i.e., (hybrid vigor; i.e., malaria/sickle-cell malaria/sickle-cell anemia); anemia); 2- frequency 2- frequency dependent selection dependent selection (survival & reproduction (survival & reproduction of any 1 morph declines of any 1 morph declines if it becomes too if it becomes too common; i.e., common; i.e., parasite/host)parasite/host)

Sexual selectionSexual selection•Sexual Sexual

dimorphismdimorphism: : secondary sex secondary sex characteristic characteristic distinctiondistinction

•Sexual selectionSexual selection: : selection selection towards towards secondary sex secondary sex characteristics characteristics that leads to that leads to sexual sexual dimorphismdimorphism

Natural Natural SelectionSelection

• Shifts to Shifts to middle rangemiddle range

• Shifts to Shifts to 2 extremes2 extremes

• Shifts to Shifts to 1 extreme1 extreme

Fitness: contribution an individual makes to the gene pool of the next generation

Conditions needed for Genetic Conditions needed for Genetic

EquilibriumEquilibrium

Hardy-Weinberg EquationHardy-Weinberg Equation• p=frequency of one allele (A); p=frequency of one allele (A);

q=frequency of the other allele (a); q=frequency of the other allele (a); p+q=1.0p+q=1.0 (p=1-q & q=1-p) (p=1-q & q=1-p)

• P2=frequency of AA genotype; P2=frequency of AA genotype; 2pq=frequency of Aa plus aA genotype; 2pq=frequency of Aa plus aA genotype; q2=frequency of aa genotype; q2=frequency of aa genotype; p2 + 2pq p2 + 2pq + q2 = 1.0+ q2 = 1.0

AS NEW SPECIES EVOLVE, AS NEW SPECIES EVOLVE, POPULATIONS BECOME POPULATIONS BECOME REPRODUCTIVELY ISOLATED REPRODUCTIVELY ISOLATED (gene pools are isolated)(gene pools are isolated)

REPRODUCTIVE ISOLATIONREPRODUCTIVE ISOLATION – – MEMEBERS OF 2 POPULATIONS MEMEBERS OF 2 POPULATIONS CANNOT INTERBREED & CANNOT INTERBREED & PRODUCE FERTILE OFFSPRING.PRODUCE FERTILE OFFSPRING.

Table 23.1aTable 23.1a

Table 23.1bTable 23.1b

TigonTigonResult of male tiger and female lion mating incaptivity. Offspring are infertile.

Separated both geographically and ecologically.

LigerLigerResult of male lion and female tiger mating in captivity. Offspring are infertile.

Fig. 23.6Fig. 23.6

Four species of leopard frogs: differ in their mating calls. Hybrids are inviable.

These squirrels living on opposite sides of the Grand Canyon demonstrate allopatric speciation.

•Sympatric:Sympatric: reproductively isolated reproductively isolated subpopulation in the midst of its subpopulation in the midst of its parent population (change in parent population (change in genome); polyploidy in plants; genome); polyploidy in plants; cichlid fishescichlid fishes

Evidence of EvolutionEvidence of Evolution1.1. Fossil RecordFossil Record

2.2. Geographic Distribution of Living Geographic Distribution of Living SpeciesSpecies

3.3. Homologous Body structuresHomologous Body structures

4.4. Similarities in EmbryologySimilarities in Embryology

Evidence of Evidence of EvolutionEvolution

Fossil Record Fossil Record provides provides evidence that evidence that living things have living things have evolvedevolved

Fossils show the Fossils show the history of life on history of life on earth and how earth and how different groups different groups of organisms of organisms have changed have changed over timeover time

Rat like common ancestor

Mammalia

Placental mammals

Marsupial Mammals

Sugar Glider

Flying Squirrel

Convergent Evolution

andAnalogous Structures

Big Question!!!Big Question!!!

How did life arise on the big blue planet??How did life arise on the big blue planet?? Scientists attempt to answer this Scientists attempt to answer this question scientifically.question scientifically.

Relative Relative Dating Dating

versus versus Absolute Absolute DatingDating

Relative DatingRelative Dating• Can determine Can determine

a fossil’s a fossil’s relative agerelative age

• Performed by Performed by estimating estimating fossil age fossil age compared with compared with that of other that of other fossilsfossils

• Drawbacks – Drawbacks – provides no provides no info about age info about age in yearsin years

Absolute datingAbsolute dating• Can determine the Can determine the

absolute age in absolute age in numbersnumbers

• Is performed by Is performed by radioactive dating radioactive dating – based on the – based on the amount of amount of remaining remaining radioactive radioactive isotopes remainisotopes remain

• Drawbacks - part of Drawbacks - part of the fossil is the fossil is destroyed during destroyed during the testthe test

Carbon-14 DatingCarbon-14 Dating

Fossil FormationFossil Formation

A cosmic explosion that hurled matter and in all A cosmic explosion that hurled matter and in all directions created the universe 10-20 billion years directions created the universe 10-20 billion years agoago Evidence Evidence

it explains why distant galaxies are traveling it explains why distant galaxies are traveling away from us at great speeds away from us at great speeds Cosmic radiation from the explosion can be Cosmic radiation from the explosion can be observedobserved

The Big Bang theory probably will never be The Big Bang theory probably will never be proven; consequentially, leaving a number of tough, proven; consequentially, leaving a number of tough, unanswered questions. unanswered questions.

Big Bang TheoryBig Bang Theory

What was early earth like?What was early earth like?Earth was Hot!!Earth was Hot!!Little or no oxygenLittle or no oxygenGasses in atmosphere:Gasses in atmosphere:

Hydrogen cyanide (poison to you!)Hydrogen cyanide (poison to you!)Hydrogen sulfideHydrogen sulfideCarbon dioxideCarbon dioxideCarbon monoxideCarbon monoxideNitrogenNitrogenwaterwater

So how did the earth So how did the earth get oxygen?get oxygen? Some of that oxygen was generated by Some of that oxygen was generated by photosynthetic cyanobacteriaphotosynthetic cyanobacteria

Some came from the Some came from the chemical chemical separationseparation of water molecules into of water molecules into oxygen and hydrogen.oxygen and hydrogen.

Oxygen drove some life Oxygen drove some life forms to extinction forms to extinction Others evolved ways of Others evolved ways of using oxygen for respirationusing oxygen for respiration

How did life begin?How did life begin?Miller and Urey’s Miller and Urey’s Experiment Experiment Passed sparks Passed sparks through a mixture of through a mixture of hydrogen methane hydrogen methane ammonia and waterammonia and water This produced This produced amino acids – the amino acids – the building blocks of lifebuilding blocks of life

Miller’s Miller’s experiment experiment suggests that suggests that lightning could lightning could have produced have produced amino acidsamino acids

How can simple amino How can simple amino acids result in life?acids result in life?

There are 3 theoriesThere are 3 theories

11. Formation of microspheres. Formation of microspheres Large organic molecules can Large organic molecules can sometimes form tiny proteinoid sometimes form tiny proteinoid microspheresmicrospheres Store and release energy, selectively Store and release energy, selectively permeable membranes, may have permeable membranes, may have acquired more characteristics of living acquired more characteristics of living cellscells

22ndnd Hypothesis for Life Hypothesis for LifeEvolution of RNA to DNAEvolution of RNA to DNA• RNA was assembled RNA was assembled from simple organic from simple organic molecules in a molecules in a primordial soupprimordial soup

• RNA was able to RNA was able to replicate itself and replicate itself and eventually form DNAeventually form DNA

• Not scientifically Not scientifically proven to be possibleproven to be possible

33rdrd Theory of Life Theory of LifeEndosymbiotic theoryEndosymbiotic theoryeukaryotic cells eukaryotic cells arose from living arose from living communities formed communities formed by prokaryotic by prokaryotic organismsorganismsAncient prokaryotes Ancient prokaryotes entered primitive entered primitive eukaryotic cells and eukaryotic cells and remained there as remained there as organellesorganelles