EVOLUTION & SPECIATION VOCABULARY REVIEW EVOLUTION – CHANGE OVER TIME EVOLUTION – CHANGE OVER...

EVOLUTION & EVOLUTION & SPECIATIONSPECIATION

VOCABULARY REVIEWVOCABULARY REVIEW

• EVOLUTIONEVOLUTION – CHANGE OVER TIME – CHANGE OVER TIME

• NATURAL SELECTIONNATURAL SELECTION - - INDIVIDUALS BETTER ADAPTED INDIVIDUALS BETTER ADAPTED TO THE ENVIRONMENT ARE ABLE TO THE ENVIRONMENT ARE ABLE TO SURVIVE & REPRODUCE.TO SURVIVE & REPRODUCE.– A.K.A. “SURVIVAL OF THE FITTEST”A.K.A. “SURVIVAL OF THE FITTEST”

Charles DarwinCharles Darwin

• Wrote in 1859Wrote in 1859: “On the Origin of Species by “On the Origin of Species by Means of Natural Selection”Means of Natural Selection”

• Two main points:Two main points:

1.1. Species were not created in their present Species were not created in their present form, but evolved from ancestral species.form, but evolved from ancestral species.

2.2. Proposed a mechanism for evolution:Proposed a mechanism for evolution: NATURAL SELECTIONNATURAL SELECTION

Natural SelectionNatural Selection• IndividualsIndividuals with favorablefavorable traitstraits are more

likely to leave more offspring better suited for their environmentenvironment.

• Also known as “Differential Reproduction”“Differential Reproduction”

• Example:Example:

English peppered moth (English peppered moth (Biston betularia))

- light and dark phases- light and dark phases

http://tidepool.st.usm.edu/crswr/peppermoths.html

Darwin’s 5 points

1. Population has variations. 2. Some variations are favorable. 3. More offspring are produced than

survive4. Those that survive have favorable

traits. 5. A population will change over time.

Artificial SelectionArtificial Selection

• The selective breedingselective breeding of domesticated plants and animals by man.

• Question:Question:

What’s the ancestor of the domesticated dog?

• Answer:Answer: WOLFWOLF

Evidence of EvolutionEvidence of Evolution

1.1. Biogeography: Biogeography:

Geographical distribution of species.Geographical distribution of species.

2. Fossil Record:2. Fossil Record:

Fossils and the order in which they Fossils and the order in which they appear appear in layers of sedimentary rock in layers of sedimentary rock (strongest (strongest evidence).evidence).

NEW VOCABULARYNEW VOCABULARY

• POPULATIONPOPULATION – GROUP OF – GROUP OF INDIVIDUALS OF SAME SPECIES INDIVIDUALS OF SAME SPECIES THAT INTERBREEDTHAT INTERBREED

• GENE POOLGENE POOL – COMMON GROUP – COMMON GROUP OF OF ALL GENES PRESENT IN A ALL GENES PRESENT IN A

POPULATIONPOPULATION

Gene PoolGene PoolCombined Combined

genetic info. genetic info. of all of all membersmembers

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

a. Bottleneck Effecta. Bottleneck Effect

• Genetic driftGenetic drift (reduction of alleles in a population) resulting from a disasterdisaster that drastically reduces reduces population sizepopulation size.

• Examples:Examples:

1.1. EarthquakesEarthquakes

2.2. Volcano’sVolcano’s

• Genetic drift can cause big losses of genetic variation for small populations. It reduces genetic variation.

• Population bottlenecks occur when a population’s size is reduced for at least one generation.

• This is illustrated by the bags of marbles shown below, where, in generation 2, an unusually small draw creates a bottleneck

• Reduced genetic variation means that the population may not be able to adapt to new selection pressures, such as climatic change or a shift in available resources, because the genetic variation that selection would act on may have already drifted out of the population.

• An example of a bottleneck:

Northern elephant seals have reduced genetic variation probably because of a population bottleneck

humans inflicted on them in the 1890s. Hunting reduced their population size to as few as 20 individuals

at the end of the 19th century. Their population has since rebounded to over 30,000—but their genes still

carry the marks of this bottleneck: they have much less genetic variation than a population of southern

elephant seals that was not so intensely hunted.

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

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

• Non-random matingNon-random mating: inbreeding and assortive : inbreeding and assortive mating (both shift frequencies of different mating (both shift frequencies of different genotypes)genotypes)

• Assortative mating occurs when individuals select mates non-randomly from within their population, on the basis of a trait that both they and their mates express.

Founder EffectFounder Effect

• Genetic driftGenetic drift resulting from the colonizationcolonization of a new location by a small number of individuals.

• Results in random changerandom change of the gene pool.


1.1. Islands (first Darwin finch)Islands (first Darwin finch)

Five Mechanisms of MicroevolutionFive Mechanisms of Microevolution

1.1. Islands (first Darwin finch)Islands (first Darwin finch)

2. Gene Flow:2. Gene Flow:

TThe gain or loss of allelesgain or loss of alleles from a population by the movementmovement of individuals or gametes.

• Immigration or emigrationImmigration or emigration.

• Gene FlowGene Flow: : genetic exchange genetic exchange due to the due to the migration of migration of fertile individuals fertile individuals or gametes or gametes between between populations populations (reduces (reduces differences differences between between populations)populations)


3. Mutation:3. Mutation:

Change in an organism’s DNA thatChange in an organism’s DNA thatcreates a new allele.creates a new allele.

4. Non-random mating:4. Non-random mating:

The selection of mates other thanThe selection of mates other thanby chance.by chance.

5. Natural selection:5. Natural selection:

Differential reproduction.Differential reproduction.

Modes of ActionModes of Action

• Natural selectionNatural selection has three modesthree modes of action:

1.1. Stabilizing selectionStabilizing selection

2.2. Directional selectionDirectional selection

3.3. Diversifying selectionDiversifying selection

Number ofIndividuals

Size of individualsSmall Large

1.1. Stabilizing SelectionStabilizing Selection

• ActsActs upon extremesextremes and favorsfavors the intermediateintermediate.



2.2. Directional SelectionDirectional Selection

• FavorsFavors variants of one extremeone extreme.



GreyhoundsBred for speed

3.3. Diversifying SelectionDiversifying Selection

• FavorsFavors variants of opposite extremesopposite extremes.



SpeciationSpeciation

• The evolutionevolution of new species.

Reproductive BarriersReproductive Barriers

• Any mechanismmechanism that impedesimpedes two species from producing fertile and/or viable hybrid offspringfertile and/or viable hybrid offspring.

• Two barriers:Two barriers:

1.1. Pre-zygotic barriers Pre-zygotic barriers

prevent fertilizationprevent fertilization

2.2. Post-zygotic barriersPost-zygotic barriers

prevents fertilized egg from prevents fertilized egg from developing into a fertile adultdeveloping into a fertile adult

1.1. Pre-zygotic BarriersPre-zygotic Barriers

a. Temporal isolation:a. Temporal isolation:

Breeding occurs at different times for different species.

b. Habitat isolation:b. Habitat isolation:

Species breed in different habitats.

c. Behavioral isolation:c. Behavioral isolation:

Little or no sexual attraction between species.

1.1. Pre-zygotic BarriersPre-zygotic Barriers

d. Mechanical isolation:d. Mechanical isolation:

Structural differences prevent gamete exchange.

e. Gametic isolation:e. Gametic isolation:

Gametes die before uniting with gametes of other species, or gametes fail to unite.

2.2. Post-zygotic BarriersPost-zygotic Barriers

a. Hybrid inviability:a. Hybrid inviability:

Hybrid zygotes fail to develop or fail to reach sexual maturity.

b. Hybrid sterility:b. Hybrid sterility:

Hybrid fails to produce functional gametes.

c. Hybrid breakdown:c. Hybrid breakdown:

Offspring of hybrids are weak or infertile.

• One oft-cited example of a postzygotic mating barrier occurs when horses and donkeys,

• two different species, interbreed to produce mules. Mules, as a hybrid offspring, are generally robust organisms. However, the genetic incompatibility of the horse and the donkey result in sterility in the mule.

• Because mules are infertile, gene flow between the horse and donkey is effectively blocked, even though they are able to produce hybrid offspring.

• 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

Sexual selectionSexual selection• Sexual Sexual

dimorphismdimorphism: : secondary sex secondary sex characteristic characteristic distinctiondistinction

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

• Sexual dimorphism is a phenotypic difference between males and females of the same species.

http://en.wikipedia.org/wiki/Phenotype

http://en.wikipedia.org/wiki/Species

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

Generation 1: 1.00 not resistant0.00 resistant

Resistance to antibacterial soap

How natural selection works


mutation!




Phenotype Phenotype ExpressionExpression•Depends on Depends on

how many how many genes genes control that control that traittrait

Single-Gene vs. Polygenic Single-Gene vs. Polygenic TraitsTraitsSingle-GeneSingle-Gene::

2 Distinct 2 Distinct PhenotypesPhenotypes

PolygenicPolygenic::

Many PhenotypesMany Phenotypes

(EG: tongue rolling)

Allele Frequencies

Natural Selection Genetic Drift

Single Gene Traits

PolygenicTraits

Directional Selection

Stabilizing Selection

Disruptive Selection

Natural Selection on Polygenic Natural Selection on Polygenic TraitsTraits

• Shifts to Shifts to

middle rangemiddle range


2 extremes2 extremes


1 extreme1 extreme

Conditions needed for Genetic Conditions needed for Genetic

EquilibriumEquilibrium

Hardy-Weinberg PrincipleHardy-Weinberg Principle

• The conceptconcept that the shuffling of genesshuffling of genes that occur during sexual reproduction, by itself, cannot changecannot change the overall genetic makeup of a population.


• This principleprinciple will be maintained in nature only if all fivefive of the following conditions are met:

1.1. Very large populationVery large population

2.2. Isolation from other populationsIsolation from other populations

3.3. No net mutationsNo net mutations

4.4. Random matingRandom mating

5.5. No natural selectionNo natural selection


• Remember:Remember:

If these conditions are met, the population is at equilibriumequilibrium.

• This means “No Change” or “No “No Change” or “No Evolution”.Evolution”.

MacroevolutionMacroevolution

• The origin of taxonomic groups higher higher than the species levelthan the species level.

MicroevolutionMicroevolution

• A change in a population’s gene poolpopulation’s gene pool over a secession of generations.

• Evolutionary changesEvolutionary changes in species over relatively brief periods of geological timegeological time.


1. Genetic drift:1. Genetic drift:

Change in the gene pool of a Change in the gene pool of a small small population due to chance.population due to chance.

• Two examples:Two examples:

a. Bottleneck effecta. Bottleneck effect

b. Founder effectb. Founder effect

SPECIATIONSPECIATION• THE THE FORMATION OF NEW SPECIESFORMATION OF NEW SPECIES

• AS NEW SPECIES EVOLVE, AS NEW SPECIES EVOLVE, POPULATIONS BECOME POPULATIONS BECOME REPRODUCTIVELY ISOLATEDREPRODUCTIVELY ISOLATED

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

3 ISOLATING 3 ISOLATING MECHANISMS……..MECHANISMS……..• BEHAVIORAL ISOLATION-BEHAVIORAL ISOLATION- CAPABLE OF CAPABLE OF

BREEDING BUT HAVE DIFFERENCES IN BREEDING BUT HAVE DIFFERENCES IN COURTSHIP RITUALS (EX. COURTSHIP RITUALS (EX. MEADOWLARKS)MEADOWLARKS)

• GEOGRAPHICAL ISOLATIONGEOGRAPHICAL ISOLATION – SEPARATED – SEPARATED BY GEOGRAPHIC BARRIERS LIKE RIVERS, BY GEOGRAPHIC BARRIERS LIKE RIVERS, MOUNTAINS, OR BODIES OF WATER (EX. MOUNTAINS, OR BODIES OF WATER (EX. SQUIRREL)SQUIRREL)

• TEMPORAL ISOLATIONTEMPORAL ISOLATION – 2 OR MORE – 2 OR MORE SPECIES REPRODUCE AT DIFFERENT SPECIES REPRODUCE AT DIFFERENT TIMES.TIMES.

Table 23.1aTable 23.1a

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

Separated both geographically and ecologically.

LigerLiger

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

Table 23.1bTable 23.1b

Fig. 23.6Fig. 23.6

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

Allopatric SpeciationAllopatric Speciation

• Induced when the ancestralancestral population becomes separatedseparated by a geographical geographical barrier.barrier.


Grand Canyon and ground squirrels

These squirrels live on opposite sides of the Grand Canyon. This is an example of allopatric speciation.

Hawaiian HoneycreepersHawaiian Honeycreepers

FOUNDER SPECIES

An example of adaptive radiation – these species all diverged from a common ancestor (founder species)

Adaptive RadiationAdaptive Radiation

• Emergence of numerous speciesEmergence of numerous species from a common ancestorcommon ancestor introduced to new and diverse environments.


Darwin’s FinchesDarwin’s Finches

SPECIATION IN DARWIN’SSPECIATION IN DARWIN’S

FINCHESFINCHES• SPECIAITON IN THE GALAPAGOS SPECIAITON IN THE GALAPAGOS

FINCHES OCCURRED BY: FINCHES OCCURRED BY:

- - FOUNDINGFOUNDING OF A NEW POPULATION, OF A NEW POPULATION, - - GEOGRAPHIC ISOLATION GEOGRAPHIC ISOLATION which led to which led to -- -- REPRODUCTIVE ISOLATIONREPRODUCTIVE ISOLATION and and

CHANGES IN THE NEW POPULATION’S CHANGES IN THE NEW POPULATION’S GENE POOL due to COMPETITION.GENE POOL due to COMPETITION.

Evidence of EvolutionEvidence of Evolution

1.1. 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 evidence provides evidence that living things that living things have evolvedhave evolved

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

Convergent EvolutionConvergent Evolution

• SpeciesSpecies from different evolutionary branchesevolutionary branches may come to resemble one another if they live in very similar environments.very similar environments.


1.1. Ostrich (Africa) and Emu (Australia).Ostrich (Africa) and Emu (Australia).

2.2. Sidewinder (Mojave Desert) andSidewinder (Mojave Desert) and

Horned Viper (Middle East Desert)Horned Viper (Middle East Desert)

Rat like common ancestor

Mammalia

Placental mammals

Marsupial Mammals

Sugar Glider

Flying Squirrel

Convergent Evolution

andAnalogous Structures

Review

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 Drawbacks - part of the fossil is of 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 oxygen

Gasses in atmosphere:Gasses in atmosphere:

Hydrogen cyanide (poison to you!)Hydrogen cyanide (poison to you!)

Hydrogen sulfideHydrogen sulfide

Carbon dioxideCarbon dioxide

Carbon monoxideCarbon monoxide

NitrogenNitrogen

waterwater

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 theory

eukaryotic cells eukaryotic cells arose from living arose from living communities formed communities formed by prokaryotic by prokaryotic organismsorganisms

Ancient prokaryotes Ancient prokaryotes entered primitive entered primitive eukaryotic cells and eukaryotic cells and remained there as remained there as organellesorganelles

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