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Chapter 24: The Origin of species

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Chapter 24: The Origin of species-Macroevolution = the origin of new taxonomic groups Speciation = origin of new species Anagenesis vs. Cladogenesis – PowerPoint PPT presentation

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Title: Chapter 24: The Origin of species


1
Chapter 24 The Origin of species
  • -Macroevolution the origin of new taxonomic
    groups
  • Speciation origin of new species
  • Anagenesis vs. Cladogenesis

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I. What is a Species?
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1. Species Concepts
  1. Ecological Species Concept defines a species
    based on its niche
  2. Pluralistic Species Concept factors that make
    species vary
  3. Morphological Species Concept unique structural
    features
  4. Genealogical Species Concept unique genetic
    history / one tip on the branching tree of life
  5. Biological Species Concept potential to
    interbreed and produce viable, fertile offspring
    / hinges on reproductive isolation or barriers

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2. Isolation Barriers
  • Reproductive Barrier any factor that impedes 2
    species from producing fertile, viable offspring
  • Prezygotic hinder fertilization of ova
  • - habitat iso live in different habitats
  • - behavioral iso signals and behaviors
  • - temporal iso different times of day or year
  • - mechanical iso anatomical incompatibility
  • - gametic iso gametes dont fuse

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2. Isolation Barriers
  • Postzygotic Barriers prevents hybrid zygote
    from developing
  • - Reduced Hybrid Viability aborted embryo
  • - Reduced Hybrid Fertility sterile offspring /
    meiosis failure
  • - Hybrid Breakdown viable F1, F1s produce
    sterile or feeble offspring

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II. How is a Species Made?
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1. Allopatric Speciation
  • Speciation takes place in populations with
    geographically separate ranges
  • Mountain range, land bridge, land production
  • Increases when a population is small and isolated
  • Can be observed in ring species where bottom
    organisms cant breed

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1. Allopatric Speciation
  • Adaptive Radiation many diversely adapted
    species from a common ancestor
  • Both pre and post zygotic barriers may evolve
    from allopatric speciation

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Sweet Video
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2. Sympatric Speciation
  • Speciation takes place in geographically
    overlapping populations
  • Result from chromosomal change, non-random mating
  • Polyploid Speciation in Plants
  • - extra sets of chromosomes
  • - autopolyploid more then 2 sets
  • - allopolyploid 2 species make a polyploid
    hybrid

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Autopolyploid
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Allopolyploidy
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2. Sympatric Speciation
  • Animals and Sympatric Speciation
  • - Genetic factors cause dependence on resources
    not used by parents
  • - Preferences for mates color or looks
    (non-random mating) / cause behavioral isolation

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3. Speed of Speciation
  1. Gradualism small changes over time
  2. Punctuated Equilibrium rapid change and then no
    change

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III. Speciation to Macroevolution
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1. Evolution Novelties Come From Older Structures
  1. Eye Spots ---- Eyes
  2. Exaptations structures that evolve in one
    context but become co-opted for another function
    / ex. Hollow bones

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2. Evo-Devo
  • Looking at evolution biology and development of
    organisms together
  • Genes that control development play a major role
    in macroevolution
  • Allometric Growth growth rates at different
    times during development / change the growth
    rates a little (genes) and it can really change
    the adult / Type of heterochrony
  • Heterochrony evolutionary change in the rate or
    timing of developmental events / salamander feet
  • - paedomorphosis reproductive development
    accelerates compared to somatic development /
    adults retaining juvenile ancestral traits
  • Homeotic Genes determine basic features where
    things develop / Hox gene changes leg buds
  • Kinda Sweet Video

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Allometric Growth
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Heterochrony
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Hox Gene
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3. Trends
  • Trends ? goal or end point
  • Bush growing in all directions not just one
  • Species selection idea that the species that
    endure the longest and generate the greatest
    number of new species determine the direction of
    evolutionary trends / people argue that it is
    gradual changes that cause the trends not numbers
    of individuals
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