The Origin of Species Chapter 24The Species Problem

Modes of Speciation The Tempo of Speciation

Gradualism Punctuated Equilibrium

Morphological

Ecological

Phylogenetic

Biological

Autopolyploidy

Polyploidy

Prezygotic Postzygotic

Reduced Hybrid fertility

Reduced Hybrid viability

Temporal

Gametic Hybrid breakdown

Behavioral

Mechanical

Allopolyploidy

Sympatric Allopatric

Habitat

CD Activity (old)

Are ligers a species?

“It’s a liger”

Hybrid Zones

Reinforcement

Fusion

Stability

Reproductive Isolation

Original Population

Allopatric SpeciationSympatric Speciation

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“It’s a liger”

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“bred for its skills and magic”

http://www.youtube.com/watch?v=CD6vpheUoPE

napoleon-dynamite-clip8.mov

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Autopolyploid Speciation

Allows the formation of a new species from one parental plant.Step 1 Step 5Step 2 Step 6Step 3 Step 4

Note: Autopolyploid contains 2X the amount of Chromosomes than original species

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Allopolyploid Speciation

Allows the formation of a new species of plant with starting with 2 different plants of different chromosome number

Step 1

Step 1 Step 2 Step 3

Note: Allopolyploid contains the sum total the chromosomes of the 2 parental species 4 + 6 + 10

The Gradualism Model of Evolution

The Punctuated Equilibrium Model of Evolution

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Many slow changes over time form a new species

New species emerge quickly (punctuated) but change little over long periods (equilibrium)

Populations in different habitats do not interact

No attraction between males and females

Mating or flowering in different times

Sex organs structures prevent reproduction

Gametes fail to interact Fertilized

zygotes fail to develop

Hybrids do not make functional gametes

Hybrids have reduced health

Prezygotic Barriers Postzygotic Barriers

Temporal GameticBehavioral Mechanical HabitatReduced

Hybrid FertilityReduced

Hybrid ViabilityF2 Hybrid

Breakdown

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A. harrisi A. leucurus

Grand Canyon

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North Rim South Rim

Strengthening reproductive barriers…hybrids cease to form

Weakening reproductive barriers…the 2 species fuse

Continued production of hybrid individuals

Possible Outcomes for Hybrids in a Hybrid Zone

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Example of Reinforcement in Hybrid Zones

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