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Macroevolution: speciation Tuesday 11/5/13. Finish up microevolution lecture…… What is a species? Biological Species Concept pre- & post-zygote barriers Speciation Rate of Speciation Allopatric & Sympatric Speciation adaptive radiation

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Macroevolution: speciation Tuesday 11/5/13

  • Finish up microevolution lecture……

  • What is a species?

    • Biological Species Concept

      • pre- & post-zygote barriers

  • Speciation

    • Rate of Speciation

    • Allopatric& Sympatric Speciation

      • adaptive radiation

    • Understanding Evolutionary Relationships

      • phylogenies / cladograms

      • taxonomy


fig 27.21

  • So, what is a species?

  • when is it subspecies vs. full species?


Biological Species Concept

  • defines species based

  • NOTE: Can not be applied in all context!!

    • Scientists rely on other criteria when

    • hybridization does occur

      • if populations interbreed and produce young, are they always considered the same species?


fig 27.20


Prezygotic Barriers:

  • ecological / habitat isolation

  • temporal isolation


Prezygotic Barriers:

  • behavioral isolation

    • differences in

    • only mate with the individuals


Prezygotic Isolating Mechanisms:

  • Mating is attempted but not successful:

  • mechanical isolation

  • gametic isolation --

    • receptors on

    • chemical signaling

    • sperm might


Postzygotic Mechanisms:

prevents proper function of zygotes once formed:

  • hybrids not reproductively successful due to:

  • zygote mortality

  • hybrid sterility

    • hybrids


Postzygotic Mechanisms:

prevents proper function of zygotes once formed:

  • F2 fitness  reduced fitness of hybrid’s offspring

  • NOTE: Hybridization does occur, despite isolating mechanism (though typically rarely).

  • If hybrids are less fit, or their offspring are less fit,


Rate of Speciation:

fig 27.22

  • Gradualism:

  • Punctuated equilibrium:


Patterns of Speciation:

  • Nonbranchingevolution (anagenesis):

  • Branching evolution (cladogenesis):


How does speciation occur?

Allopatric Speciation:

  • divergence between populations

  • if barrier

  • speciation occurs if & when



Adaptive Radiation in Isolate Population

  • speciation in allopatry

  • new species colonize other island(s) - (2)


Example of adaptive radiation:

--

Hawaiian Honeycreepers:


Sympatric Speciation

  • new species emerges within parent population

  • (1) reproductive barriers emerge due to changes in chromosome #

  • polyploidy--

  • for example -- allopolyploidy - (seen in plants)

    • hybridization

    • hybrid has

    • chromosomes double

    • four copies

    • reproductive barrier


fig 27.18

Sympatric speciation(2) resulting from diversifying selection

  • if mating with other

  • unless

  • assortative mating -


  • Phylogenies -- hypotheses about evolutionary relationships

    • Phylogeny -

      • more closely related -->

      • assumption more similar -->

    Systematics: -

    figure 25.8


    • Shared Derived Character:

    • Outgroup:

    notochord pharyngeal slits

    • Use of OUTGROUP - helps to determine primitive vs. derived


    Reading the phylogenetic tree:

    fig 27.23

    • branch points –

      • who is most closely related to whom…..


    Homologous vs. Analogous Traits:

    • Divergences from a common ancestor may result in variation in traits, and blur the lines of descent

    • Convergent evolution


    Homologous vs. Analogous Traits:

    • Homology

    • Remember:

  • Analogy


  • Calibrating the cladogram(phylogeny) with a molecular clock:

    • molecular data can help determine evolutionary relationships

    • information from fossil records

    • molecular clock:

    fig 27.24


    • Domains:

    • Bacteria

    • Archaea

    • Eukarya

    fig 27.26


    Taxonomy:

    naming & classifying of species and groups of species

    • Hierarchical classification

    • Latin (scientific) name:


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