Chapter 24: The Origin of Species

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Chapter 24 The Origin of Species

• What is a species?
• A population whose members can interbreed in
  nature and
• produce viable, fertile offspring
• aka.reproductive isolation
• What kinds of barriers keep different species
  isolated so they cannot mate?
• Figure 24.4
• Prezygotic barriers before mating /or zygote
  is formed
• Postzygotic barriers after zygote is formed

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Figure 24.4 Reproductive Barriers
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Chapter 24 The Origin of Species

• What is a species?
• What kinds of barriers keep different species
  isolated so they cannot mate?
• How are new species created?
• Allopatric speciation
• when a geographic barrier isolates a population
  blocks gene flow
• ex. mountain range emerging, new river dividing a
  field, island
• Sympatric speciation
• intrinsic factors such as chromosomal changes
  (plants) or
• non-random mating alter gene flow

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Figure 24.5 Two main modes of speciation
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Chapter 24 The Origin of Species

• What is a species?
• What kinds of barriers keep different species
  isolated so they cannot mate?
• How are new species created?
• Allopatric speciation
• when a geographic barrier isolates a population
  blocks gene flow
• ex. mountain range emerging, new river dividing a
  field, island
• Adaptive radiation
• evolution of many diversely adapted species from
  a
• common ancestor
• Seen on islands
• Sympatric speciation
• intrinsic factors such as chromosomal changes
  (plants) or
• non-random mating alter gene flow

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Figure 24.12 Adaptive radiation
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Chapter 24 The Origin of Species

• What is a species?
• What kinds of barriers keep different species
  isolated so they cannot mate?
• How are new species created?
• Allopatric speciation
• when a geographic barrier isolates a population
  blocks gene flow
• ex. mountain range emerging, new river dividing a
  field, island
• Adaptive radiation
• evolution of many diversely adapted species from
  a
• common ancestor
• Seen on islands
• Sympatric speciation
• intrinsic factors such as chromosomal changes
  (plants) or
• non-random mating alter gene flow
• ex. oats, cotton, tobacco, potatoes, wheat
• Autopolyploidy
• An individual has more than 2 chromosome sets
  derived from
• a single species from an error in meiosis

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Figure 24.8 Sympatric speciation by
autopolyploidy in plants
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Chapter 24 The Origin of Species

• What is a species?
• What kinds of barriers keep different species
  isolated so they cannot mate?
• How are new species created?
• Allopatric speciation
• when a geographic barrier isolates a population
  blocks gene flow
• ex. mountain range emerging, new river dividing a
  field, island
• Adaptive radiation
• evolution of many diversely adapted species from
  a
• common ancestor
• Seen on islands
• Sympatric speciation
• intrinsic factors such as chromosomal changes
  (plants) or
• non-random mating alter gene flow
• Autopolyploidy
• An individual has more than 2 chromosome sets
  derived from
• a single species from an error in meiosis
• Allopolyploidy
• 2 different species produce the polyploid hybrid

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Figure 24.9 One mechanism for allopolyploid
speciation in plants
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Sympatric speciation non-random mating
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Chapter 24 The Origin of Species

• What is a species?
• What kinds of barriers keep different species
  isolated so they cannot mate?
• How are new species created?
• What is the difference between gradualism
  punctuated equlibrium?

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Figure 24.13 Two models for the tempo of
speciation
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Chapter 24 The Origin of Species
5. What other mechanisms can influence
evolution/speciation?
DEVELOPMENTAL FACTORS
A) Differences in allometric growth (proportional
growth of body structures)
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Chapter 24 The Origin of Species
5. What other mechanisms can influence
evolution/speciation?
DEVELOPMENTAL FACTORS
A) Differences in allometric growth (proportional
growth of body structures)
B) The expression of homeotic genes (which
determine the body plan of an organism) may
change through mutation.
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