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

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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