Causes of Evolution Ruedi Nager Campbell et al. Chapter 23.
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Transcript of Causes of Evolution Ruedi Nager Campbell et al. Chapter 23.
Causes of Evolution
Ruedi Nager
Campbell et al. Chapter 23
William PaleyWilliam PaleyDESIGNDESIGN
Darwin & WallaceDarwin & WallaceEVOLUTIONEVOLUTION
T H E O R I G I N O F S P E C I E S
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1.1 x 1030 possibilities = 3.6 x 1022 years
• How do we recognise evolution?
• What causes evolution?
• Does evolution lead to perfection?
What is evolution?
Decent with modification
What is evolution?
We can redefine evolution as a change over time
Trait value
Time t Time t+x
Low High
• How do we recognise evolution?
• What causes evolution?
• Does evolution lead to perfection?
Causes of Evolution
There are 5 causes ‘The accidental toolkit’:
• Natural selection• Genetic drift• Mutation• Gene flow• Nonrandom mating
Causes of Evolution
1. Natural Selection
There are 3 important points:
• Variation
• Differential success
Causes of Evolution
1. Natural Selection
There are 3 important points:
• Variation
• Differential success
• Inheritance
Over time there will be mainly white individuals
Causes of Evolution
1. Natural Selection
Fitness
Differences in reproductive success
- relative contribution to the next generation • survival • access to mates • breeding success
Causes of Evolution
1. Natural SelectionExample: the peppered moth
Coloration is a camouflage:
Causes of Evolution
1. Natural SelectionExample of the industrial melanism of the peppered moth
% b
lack
for
m
1800 1900 2000
Causes of Evolution
2. Genetic DriftRandom changes in the frequency of traits to chance factors
Occurs under 2 conditions: founder effect bottleneck effect
Causes of Evolution
2. Genetic Drift
Founder effect - when a new population is a small sample of a large population
King George III
Example: Porphyria
1 / 80,000
1 / 8,000
Causes of Evolution
2. Genetic Drift
Bottleneck effect - when only a small fraction of the population survives that is no longer representative
Example: Lions living in the Ngorogoro
1960 1975 1990
Num
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Before crash
RARE
Causes of Evolution
2. Genetic Drift
Bottleneck effect - when only a small fraction of the population survives that is no longer representative
Example: Lions living in the Ngorogoro
1960 1975 1990
Num
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of l i
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50
After crash
COMMON
Causes of Evolution
3. Mutation
Changes in an organism’s DNA
Hopeful monsters
Probably of little importance
Causes of Evolution
4. Gene Flow
Changes due to movement from one place to another
20% RED
+ 2 REDS 27% RED
Causes of Evolution
5. Nonrandom Mating
Individuals with particular traits are more likely to mateSexual Selection
Boys fight Boys look fetching
Causes of Evolution
5. Nonrandom Mating
Boys fight - inter-sexual competition
The winner will mate
Causes of Evolution
5. Nonrandom Mating
Boys look fetching - intra-sexual competition
The male with the best ornament will be chosen
• How do we recognise evolution?
• What causes evolution?
• Does evolution lead to perfection?
Does Evolution lead to Perfection
Does the ability to perform improve? - ADAPTATION
Just-so-stories
The elephant’s child
Does Evolution lead to Perfection
How do we know there is an ADAPTATION?
Adaptation happens only by selection, all other changes are like a lottery
Bill size
For
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Does Evolution lead to Perfection
The course of evolution depends on:
• Historical constraints
• Existing variation
• Compromise
• ‘Accidental toolkit’
The Tale of the Monkey
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11020
The Tale of the Monkey
Natural Selection Edits Variation
Variation is the fuel of evolution- next
Evolution is not the work of a designer, but the work of a tinkerer.