Campbell et al. Chpt. 24

1
The Origin of Species
Campbell et al. Chpt. 24
2
Microevolution leads
to changes
within populations
Macroevolution leads to great
phenotypic changes
resulting in distinctive lineages
(e.g.
species)
3

• Diversity of life
• What is a species?
• How does speciation occur?
• Rate of evolution

4
1. Diversity of Life
5
1. Diversity of Life
1. Diversity of Life
Cambrian Explosion (Burgess shell)
Part of giant experiment called life
6
1. Diversity of Life
Diversity increased over time
7
1. Diversity of Life
with some interruptions
8
1. Diversity of Life
9
1. Diversity of Life
10
1. Diversity of Life
Hobbits - human tree just got bushier
still. Homo floresiensis from 18,000 years ago,
1m high
11
1. Diversity of Life
12
1. Diversity of Life
Species basic unit
Continuous lineage - information passed through
genes
13
1. Diversity of Life

• 1.4 million species described

• ca. 10 million estimated

14
1. Diversity of Life

• 1.4 million species described
• ca. 10 million estimated
• many extinct species

Large diversity of species - speciation must be
a
common event
15

• Diversity of life
• What is a species?
• How does speciation occur?
• Rate of evolution

16
2. Species Concepts
I. Morphological Species Concept
Species are similar in their appearance
17
2. Species Concepts
I. Morphological Species Concept - sometimes hard
to apply
Two different species
One single species
18
2. Species Concepts
I. Morphological Species Concept - sometimes gets
it wrong
19
2. Species Concepts
II. Biological Species Concept
Two individuals of the same species interbreed
with another in the wild and produce viable and
fertile young
20
2. Species Concepts
II. Biological Species Concept - problems

• Fossils - how do we know if they interbreed?
• Good species can sometimes produce hybrid
• Asexual organisms

21
2. Species Concepts
II. Biological Species Concept - problems
22
2. Species Concepts
III. Cohesion Species Concept
Adaptive landscape
23
2. Species Concepts
IV. Phylogenetic Species Concept
Species lineage between successive speciation
events
24

• Diversity of life
• What is a species?
• How does speciation occur?
• Rate of evolution

25
3. Speciation
Process of speciation
Parent species
26
3. Speciation
I. Establishing a barrier

• Geographical separation
• Breed at different times
• Different courtship display
• etc

Species are prevented from mating with each
other- pre-zygotic barriers
27
3. Speciation
II. Population divergence
Can be caused by any of the 5 causes
of evolution Example Artificial selection of
domesticated animals
28
3. Speciation
II. Population divergence
Example Ring species
Herring/Lesser Black-backed Gull
29
3. Speciation
II. Population divergence
Genetic subdivision Example Mice on
Madeira
30
3. Speciation
III. Sexual incompatibility
Offspring from matings between groups are not
viable or fertile - post-zygotic barriers
31
3. Speciation
Example Picture-winged fruit fly (Rhagoletis)
32
3. Speciation
Example Picture-winged fruit fly (Rhagoletis)
1. Barrier 2. Divergence
Witnessed speciation!
33

• Diversity of life
• What is a species?
• How does speciation occur?
• Rate of evolution

34
4. Rate of Evolution

• Gradualism (Darwin) - steady accumulation of
  small
• changes over long periods of time

• Rapid bursts of fast changes

35
4. Rate of Evolution
Example Radiolaria
Punctuated Equilibrium (Eldrige Gould) - long
periods of stasis interrupted by short
periods of rapid change
36
(No Transcript)
37
Can speciation events be replicated?
THE END
38
1. Diversity of Life
39
2. Species Concepts
40
4. Rate of Evolution
Example Radiation of Darwin Finches on Galapagos