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D2: Species and Speciation 5 hours. D.2.1Define allele frequency, gene pool. Allele frequencyAllele frequency –% of certain allele (variation of a gene)

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Presentation on theme: "D2: Species and Speciation 5 hours. D.2.1Define allele frequency, gene pool. Allele frequencyAllele frequency –% of certain allele (variation of a gene)"— Presentation transcript:

1 D2: Species and Speciation 5 hours

2 D.2.1Define allele frequency, gene pool. Allele frequencyAllele frequency –% of certain allele (variation of a gene) in the population for a certain locus/gene Gene poolGene pool –All genetic info of reproducing members of the population –Variation

3 D.2.2State that evolution involves a change in allele frequency in a populations gene pool over a number of generations. Mutation introduces new allelesMutation introduces new alleles Old alleles die outOld alleles die out Advantageous survivesAdvantageous survives Change in allele freq = evolutionChange in allele freq = evolution –SEVERAL generations!

4 D.2.3Discuss the definition of the term species. Xref- species Organisms have similar physiological and morphological characteristicsOrganisms have similar physiological and morphological characteristics Ability to interbreed, produce fertile offspringAbility to interbreed, produce fertile offspring Genetically distinct from other speciesGenetically distinct from other species Common phylogenyCommon phylogeny Not exactly that simple, but good enough for now!Not exactly that simple, but good enough for now!

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7 D.2.4Describe three examples of barriers between gene pools. Examples include SEPARATE POPULATIONS...MAY LEAD TO SPECIATIONSEPARATE POPULATIONS...MAY LEAD TO SPECIATION geographical isolationgeographical isolation –Physical barriers (land, water formation) prevent males/females from meeting & interbreeding populations are separated hybrid infertilityhybrid infertility –2 nd generation unlikely –Genetic barrier between species temporal isolationtemporal isolation –Incompatible time frames for mating (flowers blooming/seasons; hibernations; migrations) behavioural isolationbehavioural isolation –Lifestyle, habits incompatible with other population –Courtship displays

8 D.2.5Explain how polyploidy can contribute to speciation. Xref- Meiosis / 10.1 Avoid examples involving hybridization as well as polyploidy, such as the evolution of wheat.Avoid examples involving hybridization as well as polyploidy, such as the evolution of wheat. 3n, 4n, 5n, etc.3n, 4n, 5n, etc. Cell division mistakes, chromosomes dont separate completelyCell division mistakes, chromosomes dont separate completely Common in plantsCommon in plants Extra chroms plant more vigorousExtra chroms plant more vigorous Replication errors more commonReplication errors more common 2 populations could evolve at different rates b/c of difference in ploidy2 populations could evolve at different rates b/c of difference in ploidy Could lead to speciationCould lead to speciation

9 D.2.6Compare allopatric speciation, sympatric speciation. Speciation: the formation of a new species by splitting of an existing species.Speciation: the formation of a new species by splitting of an existing species. Sympatric: in the same geographical area Temporal, behavioural isolationSympatric: in the same geographical area Temporal, behavioural isolation –Pheromones, mating calls, etc. may be changed slightly, allow for mates or not Allopatric: in different geographical areas geographic isolationAllopatric: in different geographical areas geographic isolation –2 pops separated, evolve separately –If allowed to mingle in future, may not be able to interbreed...new species SawFly (Tenthredo livida) Snow geese (Chen caerulescens) Pin and thrumb primroses (Primula vulgaris) Fertilisat ion

10 Zedonk Genetic Hybrid inviability Hybrid offspring die Hybrid infertility Hybrids survive but are incapable of producing gametes

11 D.2.7Outline the process of adaptive radiation. Rapid evolution from 1 (or a few) species into moreRapid evolution from 1 (or a few) species into more Slightly diff niches, more successfulSlightly diff niches, more successful Natural selectionNatural selection Speciation event(s) (isolation)Speciation event(s) (isolation) EX-finches, lemursEX-finches, lemurs Lemurs once widespread b/c no competition (apes, monkeys)Lemurs once widespread b/c no competition (apes, monkeys) –Lots phenotypic diversity –Some better adapted to certain niches, led to adaptive radiation –Apes, monkeys...outcompete lemurs, so lemurs not found

12 Mechanisms of speciation Isolation of a population so that it cannot breed freely with others is necessary Geographic Ecological Behavioural Mechanical/anatomic al Physiological Genetic Madagascar Google earth Ringtailed lemurs (Lemur catta) © 2008 Paul Billiet ODWSODWS

13 D.2.8Compare convergent evolution, divergent evolution. Convergent –Not a recent common ancestor –2 species or characteristics look similar –Australia & N America: marsupials vs placentals –Wings (bat, bird); bioluminescence (bacteria, fungi) Divergent –Recent common ancestor –Less similar over time

14 D.2.9Discuss ideas on the pace of evolution including gradualism and punctuated equilibrium. Gradualism: small, continuous, slow change from one form to anotherGradualism: small, continuous, slow change from one form to another –Fossil record –Present day examples –P. 429 diagrams Punctuated equilibrium: long periods without appreciable change and short periods of rapid evolutionPunctuated equilibrium: long periods without appreciable change and short periods of rapid evolution –Response to change in environment Volcanic eruptions and meteor impacts affecting evolution on EarthVolcanic eruptions and meteor impacts affecting evolution on Earth –65mya...dinosaurs extinct; mammals survived –Until a big environmental change, little/no change in fossil record

15 Evolution of new species Two possible ways from gradualism PHYLETIC TRANSFORMATION ALLOPATRIC SPECIATION © 2008 Paul Billiet ODWSODWS

16 PHYLETIC TRANSFORMATION Gradual accumulation of small genetic variations preserved by natural selection A whole population imperceptibly to evolve in to a new species Impossible to draw a clear line between the end of the first species and the beginning of its descendant species There would be a long period of intermediate forms © 2008 Paul Billiet ODWSODWS

17 ALLOPATRIC SPECIATION Geographical or reproductive isolation of a part of the population would allow it to evolve in a different direction Possibly more rapidly than the main population If the isolated population is small, it might be very difficult to find fossils of the intermediate stages © 2008 Paul Billiet ODWSODWS

18 Species W Species X Species Y Species ZSpecies Y Allopatric speciation of Species W into species X due to the isolation of a small population of Species W Allopatric speciation of species Y into species Z due to the isolation of a small population of species Y Phyletic transition of species W into Species Y due to the slow gradual accumulation of mutations in Species W Evolution Time © 2008 Paul Billiet ODWSODWS

19 THE PUNCTUATED EQUILIBRIUM MODEL They observed that the fossil record gives a different picture for the evolution They claim that there were long periods of stasis (4- 10 million years) involving little evolutionary change Then occasional rapid formation of new species As little as 5, ,000 years Stephen J Gould Niles Eldredge © 2008 Paul Billiet ODWSODWS

20 Evolution Time Rapid speciation Stasis Species W Species X Species Y Species Z © 2008 Paul Billiet ODWSODWS

21 Problems... Fossil evidence is the only evidence of either theoryFossil evidence is the only evidence of either theory Not all characteristics of a species are present in fossil recordNot all characteristics of a species are present in fossil record Not necessarily proof of phylogenyNot necessarily proof of phylogeny

22 NATURAL SELECTION AT THE LEVEL OF THE ALLELE Biston betularia Sickle cell anemia

23 D.2.10Describe one example of transient polymorphism. Polymorphisms = many shapes (phenotypes)Polymorphisms = many shapes (phenotypes) Industrial melanism: peppered mothIndustrial melanism: peppered moth –Biston betularia –Peppered (grey) –Melanic (black) –Pre-Industrial Revolution: advantageous to be grey, camouflaged on tree bark –Ind. Rev. soot on trees, black bark; black ptypes survived (more fit) –Natural selection! –Clean Air Act…grey more fit –Temporary change TRANSIENT polymorphism

24 D.2.11Describe sickle-cell anemia (SCA) as an example of balanced polymorphism. Xref- SCA-4.1.4; malaria 2/more alleles of population are not transient and changing. Theyre stabilized by natural selection. Sickle-cell anemia –Balanced polymorphism –Heterozygotes have advantage in malarial regions Hb A Hb S More fit than either homozygote AA = very susceptible to malaria SS = sickle cell, but resistant to malaria AS = some sickled cells, but usually not anemic; K- deficient sickled cells kills Plasmodium parasite –S Selected for & selected against... balanced


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