1 campbell et al. chpt. 24 the origin of species
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Campbell et al. Chpt. 24
The Origin of Species
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Microevolution leads to changes leads to changes within populationswithin populations
Macroevolution leads to great phenotypic changes resulting in distinctive lineages
(e.g. species)
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• Diversity of life
• What is a species?
• How does speciation occur?
• Rate of evolution
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1. Diversity of Life
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1. Diversity of Life
Part of giant experiment called life
1. Diversity of Life
Cambrian Explosion (Burgess shell)
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1. Diversity of Life
Diversity increased over time…
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1. Diversity of Life
… with some interuptions
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1. Diversity of Life
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1. Diversity of Life
Bushy tree
Evolution does not follow an inbuilt direction!
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1. Diversity of Life
“Hobbits” - human tree just got bushier still.Homo floresiensis from 18,000 years ago, 1m high
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1. Diversity of Life
Species = basic unit
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1. Diversity of Life
Species = basic unit
Speciation - rise of new species
Continuous lineage - informationpassed through genes
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1. Diversity of Life
• 1.4 million species described
• ca. 10 million estimated
• many extinct species
(about 90% of all species that ever lived are extinct)
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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
Understanding how this diversity arose is a central question in evolutionary biology
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• Diversity of life
• What is a species?
• How does speciation occur?
• Rate of evolution
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2. Species Concepts
I. Morphological Species Concept
Species are similar in their appearance
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2. Species Concepts
I. Morphological Species Concept - sometimes hard to apply
Two different species One single species
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2. Species Concepts
I. Morphological Species Concept - sometimes gets it wrong
New Zealand moa (extinct): females much bigger than males
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2. Species Concepts
II. Biological Species Concept
Two individuals of the same species interbreed withanother in the wild and produce viable and fertile young
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2. Species Concepts
II. Biological Species Concept - problems
•Fossils - how do we know if they interbreed?
•“Good” species can sometimes produce hybrid
•Asexual organisms
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2. Species Concepts
II. Biological Species Concept - problems
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2. Species Concepts
III. Cohesion Species Concept
Adaptive landscape
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2. Species Concepts
IV. Phylogenetic Species Concept
Species = lineage between successive speciation events
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• Diversity of life
• What is a species?
• How does speciation occur?
• Rate of evolution
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3. Speciation
Process of speciation
Parentspecies
I. Barrier
2 separate species
III. Don’t interbreedII. Diverge
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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
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3. Speciation
II. Population divergence
Can be caused by any of the 5 causes ofevolutionExample: Artificial selection of domesticated animals
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3. Speciation
II. Population divergence
Example: Ring species Herring/Lesser Black-backed Gull
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3. Speciation
II. Population divergence
Genetic subdivisionExample: Mice on Madeira
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3. Speciation
III. Sexual incompatibility
Offspring from matings between groupsare not viable or fertile- post-zygotic barriers
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1. Barrier
3. Speciation
Example Picture-winged fruit fly (Rhagoletis)
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3. Speciation
Example Picture-winged fruit fly (Rhagoletis)
Witnessed speciation!
1. Barrier2. Divergence3. Don’t interbreed
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• Diversity of life
• What is a species?
• How does speciation occur?
• Rate of evolution
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4. Rate of Evolution
• Gradualism (Darwin) - steady accumulation of small changes over long periods of time
• Rapid bursts of fast changes
• Stasis - no changes over long periods of time
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4. Rate of Evolution
Example: Radiolaria
Punctuated Equilibrium (Eldrige & Gould) - long periods of stasis interrupted by short periods of rapid change
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Can speciation events be replicated?
Play again the tape
THE END
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1. Diversity of Life
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2. Species Concepts
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4. Rate of Evolution
Example: Radiation of Darwin Finches on Galapagos