1. The Origin of Species Chapter 24 The Species Problem Modes of Speciation The Tempo of Speciation GradualismPunctuated Equilibrium Morphological Ecological Phylogenetic Biological Autopolyploidy Polyploidy PrezygoticPostzygotic Reduced Hybrid fertility Reduced Hybrid viability Temporal Gametic Hybrid breakdown Behavioral Mechanical Allopolyploidy SympatricAllopatric Habitat CD Activity (old) Are ligers a species? “It’s a liger”It’s a liger Hybrid Zones Reinforcement Fusion Stability Reproductive Isolation

2. Original Population Allopatric SpeciationSympatric Speciation Slide 1

3. “It’s a liger”liger Slide 1 “bred for its skills and magic” http://www.youtube.com/watch?v=CD6vpheUoPE

4. Slide 1 Autopolyploid Speciation Allows the formation of a new species from one parental plant. Step 1Step 5Step 2Step 6Step 3Step 4 Note: Autopolyploid contains 2X the amount of Chromosomes than original species

5. Slide 1 Allopolyploid Speciation Allows the formation of a new species of plant with starting with 2 different plants of different chromosome number Step 1 Step 2Step 3 Note: Allopolyploid contains the sum total the chromosomes of the 2 parental species 4 + 6 + 10

6. The Gradualism Model of Evolution The Punctuated Equilibrium Model of Evolution Slide 1 Many slow changes over time form a new species New species emerge quickly (punctuated) but change little over long periods (equilibrium)

7. 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 TemporalGameticBehavioralMechanicalHabitat Reduced Hybrid Fertility Reduced Hybrid Viability F2 Hybrid Breakdown Slide 1

8. A. harrisi A. leucurus Grand Canyon Slide 1 North Rim South Rim

9. 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 Slide 1

10. Example of Reinforcement in Hybrid Zones Slide 1