Upload
jessie-smith
View
219
Download
2
Tags:
Embed Size (px)
Citation preview
Chapter 24The 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.