Chapter 24 The Origin of Species Question? What is a species? Comment - Evolution theory must also explain how species originate. Two Concepts of Species Morphospecies Problem Where does extensive phenotype variation fit? Two Schools Biological Species Key Points Heaven Scent an F1 hybrid between 2 species, but sterile. Speciation Requires: Reproductive Barriers Main Types of Barriers Prezygotic - Types Habitat Isolation Behavioral Isolation Temporal Isolation Mechanical Isolation Gametic Isolation Postzygotic Types Reduced Hybrid Viability Reduced Hybrid Fertility Hybrid Breakdown Modes of Speciation Allopatric Speciation Example Another Example Conditions Favoring Allopatric Speciation Conditions Favoring Allopatric Speciation Result Adaptive Radiation Mechanism When the Environment Saturates Sympatric Speciation Plants Polyploid Types Autopolyploid Allopolyploid Animals Gradualism Evolution Gradualism Predicts: Problem Punctuated Evolution Punctuated Equilibrium Predictions Predictions Possible Mechanism Comment Origin of Evolutionary Novelty Ex - Homeosis Gene Duplications Future of Evolution ? Look for new theories and ideas to be developed, especially from new fossil finds and from molecular (DNA) evidence. Evolutionary Trends Evolution is not goal oriented. It does not produce “perfect” species. Remember – species survive because of their adaptations. They don’t adapt to survive. Summary Be able to discuss the main theories of what is a “species”. Know various reproductive barriers and examples. Summary Know allopatric and sympatric speciation. Be able to discuss gradualism and punctuated equilibrium theories. Summary Recognize various ideas about the origin of evolutionary novelties.