The Origin of Species

1
The Origin of Species

• Chapter 24
• Biology Campbell Reece

2
What is a species?

• Biological species concept
• Reproductive isolation

3
What is a species?
4
Prezygotic Barriers

• What are prezygotic barriers?
• Habitat isolation
• Behavioral isolation

5
Habitat and Behavioral Isolation
6
Prezygotic Barriers

• Temporal isolation
• Mechanical isolation
• Gametic isolation

7
Temporal, Mechanical Gametic Isolation
8
Postzygotic Barriers

• What are postzygotic barriers?
• Reduced hybrid viability
• Hybrid breakdown

9
Reduced Hybrid Viability Hybrid Breakdwon
10
Postzygotic Barriers

• Reduced Hybrid Fertility

11
Reproductive Barriers
12
Modes of Speciation

• Allopatric speciation
• Sympatric speciation

13
Conditions for Allopatric Speciation

• More likely if the population is both small and
  isolated
• Barrier has to be significant enough to not be
  crossable
• They must become different enough that they can
  no longer interbreed

14
Adaptive Radiation

• What is it?
• Especially common on island chains such as the
  Galapagos and the Hawaiian Islands

15
Sympatric Speciation in Plants

• When meiosis goes wrong

16
Sympatric Speciation in Animals

• Polyploid speciation in animals?
• Dependent on different resources
• Nonrandom mating

17
Punctuated Equilibrium vs. Gradualism
18
Microevolution vs. Macroevolution

• Microevolution
• Macroevolution