Dispatch—Explain thiscladogram
Practice Evolution Quiz
•http://tinyurl.com/3nmb6gm
Problem 3
•If you observe a population and find that16% show the recessive trait, you knowthe frequency of the aa genotype. Thismeans you know q2. What is q for thispopulation?
Evolution of populations
•Evolution = change in allele frequenciesin a population
–hypothetical: what conditions would causeallele frequencies to not change?
–non-evolving population
REMOVE all agents of evolutionary change
1.very large population size (no genetic drift)
2.no migration (no gene flow in or out)
3.no mutation (no genetic change)
4.random mating (no sexual selection)
5.no natural selection (everyone is equally fit)
5 Agents of evolutionary change
Mutation
Gene Flow
Genetic Drift
Selection
Non-random mating
Application of H-W principle
•Sickle cell anemia
–inherit a mutation in gene coding forhemoglobin
•oxygen-carrying blood protein
•recessive allele = HsHs
–normal allele = Hb
–low oxygen levels causesRBC to sickle
•breakdown of RBC
•clogging small blood vessels
•damage to organs
–often lethal
Sickle cell frequency
•High frequency of heterozygotes
–1 in 5 in Central Africans = HbHs
–unusual for allele with severedetrimental effects in homozygotes
•1 in 100 = HsHs
•usually die before reproductive age
Why is the Hs allele maintained at such highlevels in African populations?
Why is the Hs allele maintained at such highlevels in African populations?
Suggests some selective advantage ofbeing heterozygous…
Suggests some selective advantage ofbeing heterozygous…
Malaria
Single-celled eukaryote parasite(Plasmodium) spends part of itslife cycle in red blood cells
Single-celled eukaryote parasite(Plasmodium) spends part of itslife cycle in red blood cells
1
2
3
Heterozygote Advantage
•In tropical Africa, where malaria is common:
–homozygous dominant (normal)
•die or reduced reproduction from malaria: HbHb
–homozygous recessive
•die or reduced reproduction from sickle cell anemia: HsHs
–heterozygote carriers are relatively free of both: HbHs
•survive & reproduce more, more common in population
Hypothesis:
In malaria-infectedcells, the O2 level islowered enough tocause sickling whichkills the cell & destroysthe parasite.
Hypothesis:
In malaria-infectedcells, the O2 level islowered enough tocause sickling whichkills the cell & destroysthe parasite.
Frequency of sickle cell allele& distribution of malaria
Hardy-Weinberg lab pod cast
•http://www.youtube.com/watch?v=KmqgZvUoq3k
Lab—Part A
Taster
NonTaster
PTC
Control
Non-Tasters=Homo recessive (aa)
Tasters=Homo Dominant (AA) or Heter (Aa)
Figure out the p2 and 2pq for our class
Results and Discussion
•5 Hardy Weinberg calculations
•Show work—organzied part A-E
•Discussion: In part A evolution did/did nothappen because…. In part B…. In part C
•Explain WHY, use terms
Part B—Testing an idealPopulation
Initial Class Frequencies GG____ Gg____ gg___
My initial genotype ___
F1____
F2_____
F3_____
F4_____
F5______
Final Class Frequencies
GG____ Gg____ gg ___
Part C—Selection (homo recessiveselected against)
Initial Class Frequencies GG____ Gg____ gg___
My initial genotype ___
F1____
F2_____
F3_____
F4_____
F5______
Final Class Frequencies
GG____ Gg____ gg___
Part D—Heterozygous Advantage(Homo dom—may die of maleria (flip coin; homorecessive—die of sickle cell)
•Initial Class Frequencies GG____ Gg 24/48gg___
•My initial genotype ___
•F1____
•F2_____
•F3_____
•F4_____
•F5______
Final Class Frequencies
•GG 16/48 Gg 32/48 gg 0/48
Part E—Genetic Drift (break into 3smaller populations—makehypothesis)
•Initial Class Frequencies GG____ Gg____gg___
•My initial genotype ___
•F1____
•F2_____
•F3_____
•F4_____
•F5______
Final Class Frequencies
Frequencies GG____ Gg____ gg___
Macroevolution: the origin of new taxonomic groupsMacroevolution: the origin of new taxonomic groups
•Speciation: the origin of new species•Speciation: the origin of new species
•1- Anagenesis (phyletic evolution):accumulation of heritable changes•1- Anagenesis (phyletic evolution):accumulation of heritable changes
•2- Cladogenesis (branching evolution):budding of new species from a parent species thatcontinues to exist (basis of biological diversity)
What is a species?What is a species?
•Biological species concept(ErnstMayr): a population or group ofpopulations whose members have thepotential to interbreed and produce viable,fertile offspring (genetic exchange ispossible and that is genetically isolatedfrom other populations)•Biological species concept(ErnstMayr): a population or group ofpopulations whose members have thepotential to interbreed and produce viable,fertile offspring (genetic exchange ispossible and that is genetically isolatedfrom other populations)
How and why do new species originate?How and why do new species originate?
•Species are created by a series ofevolutionary processes•Species are created by a series ofevolutionary processes
–populations become isolated–populations become isolated
•geographically isolated•geographically isolated
•reproductively isolated•reproductively isolated
–isolated populationsevolve independently–isolated populationsevolve independently
Dispatch—Draw and explainModes of speciation(based on how gene flow is interrupted)Dispatch—Draw and explainModes of speciation(based on how gene flow is interrupted)
•Allopatric: “other country”populations segregated by ageographical barrier; can result inadaptive radiation (island species)•Allopatric: “other country”populations segregated by ageographical barrier; can result inadaptive radiation (island species)
•Sympatric: “same countryreproductively isolatedsubpopulation in the midst of itsparent population (change ingenome); polyploidy in plants;cichlid fishes•Sympatric: “same countryreproductively isolatedsubpopulation in the midst of itsparent population (change ingenome); polyploidy in plants;cichlid fishes
Reproductive Isolation (isolation of gene pools), IReproductive Isolation (isolation of gene pools), I
•Prezygotic barriers: impede mating betweenspecies or hinder the fertilization of the ova•Prezygotic barriers: impede mating betweenspecies or hinder the fertilization of the ova
•Habitat (snakes; water/terrestrial)•Habitat (snakes; water/terrestrial)
•Behavioral (fireflies; mate signaling)•Behavioral (fireflies; mate signaling)
•Temporal (salmon; seasonal mating)•Temporal (salmon; seasonal mating)
•Mechanical (flowers; pollination anatomy)•Mechanical (flowers; pollination anatomy)
•Gametic (frogs; egg coat receptors)•Gametic (frogs; egg coat receptors)
Habitat isolationHabitat isolation
•Species occur in same region, but occupy different habitats so rarelyencounter each other•Species occur in same region, but occupy different habitats so rarelyencounter each other
–reproductively isolated–reproductively isolated
2 species of garter snake, Thamnophis, occur insame area, but one lives in water & other isterrestrial
2 species of garter snake, Thamnophis, occur insame area, but one lives in water & other isterrestrial
lions & tigers couldhybridize, but they livein different habitats:
lions in grasslands
tigers in rainforest
lions & tigers couldhybridize, but they livein different habitats:
lions in grasslands
tigers in rainforest
Temporal isolationTemporal isolation
•Species that breed during different times of day, different seasons, ordifferent years cannot mix gametes•Species that breed during different times of day, different seasons, ordifferent years cannot mix gametes
–reproductive isolation–reproductive isolation
Eastern spotted skunk (L)& western spotted skunk(R) overlap in range buteastern mates in latewinter & western mates inlate summer
Eastern spotted skunk (L)& western spotted skunk(R) overlap in range buteastern mates in latewinter & western mates inlate summer
Behavioral isolationBehavioral isolation
•Unique behavioral patterns & rituals isolate species•Unique behavioral patterns & rituals isolate species
–identifies members of species–identifies members of species
–attract mates of same species –attract mates of same species
•courtship rituals, mating calls•courtship rituals, mating calls
•reproductive isolation•reproductive isolation
Blue footed boobies mate onlyafter a courtship display uniqueto their species
Blue footed boobies mate onlyafter a courtship display uniqueto their species
Mechanical isolationMechanical isolation
•Morphological differences can prevent successful mating•Morphological differences can prevent successful mating
–reproductive isolation–reproductive isolation
Even in closely related speciesof plants, the flowers oftenhave distinct appearances thatattract different pollinators.These 2 species of monkeyflower differ greatly in shape &color, therefore cross-pollination does not happen.
Even in closely related speciesof plants, the flowers oftenhave distinct appearances thatattract different pollinators.These 2 species of monkeyflower differ greatly in shape &color, therefore cross-pollination does not happen.
Plants
sympatric speciation?
Mechanical isolationMechanical isolation
•For many insects, male &female sex organs ofclosely related species donot fit together, preventingsperm transfer•For many insects, male &female sex organs ofclosely related species donot fit together, preventingsperm transfer
–lack of “fit” between sexual organs:hard to imagine for us… but a big issue for insects with different shaped genitals!–lack of “fit” between sexual organs:hard to imagine for us… but a big issue for insects with different shaped genitals!
Damsel fly penises
Animals
Gametic isolationGametic isolation
•Sperm of one species may not be able to fertilize eggs of anotherspecies•Sperm of one species may not be able to fertilize eggs of anotherspecies
–mechanisms–mechanisms
•biochemical barrier so sperm cannot penetrate egg•biochemical barrier so sperm cannot penetrate egg
–receptor recognition: lock & key between egg & sperm–receptor recognition: lock & key between egg & sperm
•chemical incompatibility•chemical incompatibility
–sperm cannot survive in female reproductive tract–sperm cannot survive in female reproductive tract
Sea urchins release sperm &eggs into surrounding waterswhere they fuse & formzygotes. Gametes of differentspecies— red & purple —areunable to fuse.
Sea urchins release sperm &eggs into surrounding waterswhere they fuse & formzygotes. Gametes of differentspecies— red & purple —areunable to fuse.
Gametic isolationGametic isolation
•Sperm of one species may not be able to fertilize eggs of anotherspecies•Sperm of one species may not be able to fertilize eggs of anotherspecies
–mechanisms–mechanisms
•biochemical barrier so sperm cannot penetrate egg•biochemical barrier so sperm cannot penetrate egg
–receptor recognition: lock & key between egg & sperm–receptor recognition: lock & key between egg & sperm
•chemical incompatibility•chemical incompatibility
–sperm cannot survive in female reproductive tract–sperm cannot survive in female reproductive tract
Sea urchins release sperm &eggs into surrounding waterswhere they fuse & formzygotes. Gametes of differentspecies— red & purple —areunable to fuse.
Sea urchins release sperm &eggs into surrounding waterswhere they fuse & formzygotes. Gametes of differentspecies— red & purple —areunable to fuse.
Reproductive Isolation, IIReproductive Isolation, II
•Postzygotic barriers: fertilization occurs, but thehybrid zygote does not develop into a viable, fertileadult•Postzygotic barriers: fertilization occurs, but thehybrid zygote does not develop into a viable, fertileadult
•Reduced hybrid viability (frogs; zygotes fail todevelop or reach sexual maturity)•Reduced hybrid viability (frogs; zygotes fail todevelop or reach sexual maturity)
•Reduced hybrid fertility (mule; horse x donkey;cannot backbreed)•Reduced hybrid fertility (mule; horse x donkey;cannot backbreed)
•Hybrid breakdown (cotton; 2nd generationhybrids are sterile)•Hybrid breakdown (cotton; 2nd generationhybrids are sterile)
Reduced hybrid viabilityReduced hybrid viability
•Genes of different parent species mayinteract & impair the hybrid’s development•Genes of different parent species mayinteract & impair the hybrid’s development
Species of salamandergenus, Ensatina, mayinterbreed, but mosthybrids do not completedevelopment & those thatdo are frail.
Species of salamandergenus, Ensatina, mayinterbreed, but mosthybrids do not completedevelopment & those thatdo are frail.
Mules are vigorous,but sterile
Reduced hybrid fertilityReduced hybrid fertility
•Even if hybrids are vigorousthey may be sterile•Even if hybrids are vigorousthey may be sterile
–chromosomes of parents may differ in number or structure & meiosis inhybrids may fail to produce normal gametes–chromosomes of parents may differ in number or structure & meiosis inhybrids may fail to produce normal gametes
Donkeys have 62chromosomes
(31 pairs)
Horses have 64chromosomes
(32 pairs)
Mules have 63 chromosomes!
Hybrid breakdownHybrid breakdown
•Hybrids may be fertile & viable in firstgeneration, but when they mate offspringare feeble or sterile•Hybrids may be fertile & viable in firstgeneration, but when they mate offspringare feeble or sterile
In strains of cultivated rice,hybrids are vigorous but plantsin next generation are small &sterile.
On path to separate species.
In strains of cultivated rice,hybrids are vigorous but plantsin next generation are small &sterile.
On path to separate species.
