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D2: Species and Speciation

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1 D2: Species and Speciation
5 hours

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

3 Mutation introduces new alleles Old alleles “die out”
D.2.2 State that evolution involves a change in allele frequency in a population’s gene pool over a number of generations. Mutation introduces new alleles Old alleles “die out” Advantageous  survives Change in allele freq = evolution SEVERAL generations!

4 D.2.3 Discuss the definition of the term species. Xref- species- 5.1.1
Organisms have similar physiological and morphological characteristics Ability to interbreed, produce fertile offspring Genetically distinct from other species Common phylogeny Not exactly that simple, but good enough for now!



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

8 Cell division mistakes, chromosomes don’t separate completely
D.2.5 Explain how polyploidy can contribute to speciation. Xref- Meiosis / 10.1 Avoid examples involving hybridization as well as polyploidy, such as the evolution of wheat. 3n, 4n, 5n, etc. Cell division mistakes, chromosomes don’t separate completely Common in plants Extra chroms  plant more vigorous Replication errors more common 2 populations could evolve at different rates b/c of difference in ploidy Could lead to speciation

9 D.2.6 Compare allopatric speciation, sympatric speciation.
Speciation: the formation of a new species by splitting of an existing species. Sympatric: 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 isolation 2 pops separated, evolve separately If allowed to mingle in future, may not be able to species Snow geese (Chen caerulescens) SawFly (Tenthredo livida) Fertilisation Pin and thrumb primroses (Primula vulgaris)

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

11 D.2.7 Outline the process of adaptive radiation.
“Rapid” evolution from 1 (or a few) species into more Slightly diff niches, more successful Natural selection Speciation event(s) (isolation) EX-finches, lemurs 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
Madagascar Google earth Isolation of a population so that it cannot breed freely with others is necessary Geographic Ecological Behavioural Mechanical/anatomical Physiological Genetic Ringtailed lemurs (Lemur catta) © 2008 Paul Billiet ODWS

13 D.2.8 Compare convergent evolution, divergent evolution.
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 Gradualism: small, continuous, slow change from one form to another
D.2.9 Discuss ideas on the pace of evolution including gradualism and punctuated equilibrium. Gradualism: 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 evolution Response to change in environment Volcanic 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 ODWS

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 ODWS

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 ODWS

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

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 ODWS

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

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

Sickle cell anemia Biston betularia

23 D.2.10 Describe one example of transient polymorphism.
Polymorphisms = many “shapes” (phenotypes) Industrial 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 p’types survived (more fit) Natural selection! Clean Air Act…grey more fit Temporary change  TRANSIENT polymorphism

24 D.2.11 Describe 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. They’re stabilized by natural selection. Sickle-cell anemia Balanced polymorphism Heterozygotes have advantage in malarial regions HbAHbS 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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