Chapter 14- Origin of Species

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Chapter 14- Origin of Species

• Adaptive radiation
• Allopatric speciation
• Behavioral isolation
• Biological species concept
• Ecological species concept
• Gametic isolation
• Genealogical species concept
• Gradualist model
• Habitat isolation
• Hybrid breakdown
• Hybrid inviability

• Hybrid sterility
• Mechanical isolation
• Morphological species concept
• Polyploidy cells
• Punctuated equilibrium
• Reproductive barrier
• Speciation
• Sympatric speciation
• Taxonomy
• Temporal isolation

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Something to remember

• Most of the time evolution is gradual, sometimes
  though it can be observed over several
  generations

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Speciation

• Evolution of a new species
• Biological species concept- population or group
  of populations whose members can interbreed and
  produce fertile offspring
• Ring species- forms a ring around geographic
  feature (may cause speciation)

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Speciation cont

• Morphological species concept- classify species
  by measureable phenotypic traits
• Genealogical species concept- defines species by
  a set of organisms with unique genetic history
• Ecological species concept- idendifies by
  ecological niche (role in env)

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Reproductive barriers

• Keep species separate
• Can cause speciation
• Ex mosquitoes in London Underground

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Prezygotic reproductive barriers

• Prevents mating
• Temporal isolation- mating/flowering occurs at
  different times/seasons
• Habitat isolation- populations live in different
  habitats and dont meet
• Behavioral isolation- no attraction between sexes
• Mechanical isolation- genitalia structure/flowers
  differs, prevents copulation
• Gametic isolation- gametes die before uniting

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Postzygotic reproductive barriers

• Prevents development of fertile adults
• Hybrid inviability- zygotes fail to develop or
  reach sexual maturity
• Hybrid sterility- dont produce functional
  gametes
• Hybrid breakdown- offspring of hybrids are weak
  or infertile

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Geographic isolation

• Causes speciation
• Allopatric speciation
• Ex lakes dry up into smaller lakes, fish cant
  move from one to another
• Ring species sometime end up as new species
• Occurs when gene pool changes to create a
  reproductive barrier
• More likely to happen in small, isolated pops

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Geographic isolation cont

• Galapagos finches
• Adaptive radiation- evolution of many species
  from a common ancestor due to new environments

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Sympatric speciation

• Reproductive isolation develops and new species
  arise without geographic separation
• Widespread in plants
• Accident in meiosis produces cells with extra
  chromosome sets
• Polyploid cells- cells that has more than 2 sets
  of chromosomes
• 2n gametes can self-fertilize and produce a 4n
  plant
• Production of a 4n cell is an instant speciation
  event, because it now cant reproduce with parent
  species
• Ex strawberries
• 2n gamete fused with 1n gamete produces 3n which
  is sterile b/c odd chromosomes cant form
  homologous pairs

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Sympatric speciation cont

• Chemicals can be used to induce these errors to
  hybridize plants
• Ex yield of wheat with resistance of rye
• Polyploid crops oats, potatoes, bananas,
  peanuts, barley, plums, apples, sugarcane,
  coffee, wheat, cotton, strawberries
• 25-50 of plant species are polyploid

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Tempo of speciation
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Tempo of Speciation cont

• Gradualist- populations evolve gradually as they
  become adapted to new environments
• Very few fossil sequences show the steady
  accumulation of small changes
• Punctuated equilibrium- long periods of little
  change with abrupt episodes of speciation
• although evolution is jumpy when viewed as a
  whole its relatively steady