causes of evolution ruedi nager campbell et al. chapter 23
TRANSCRIPT
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Causes of Evolution
Ruedi Nager
Campbell et al. Chapter 23
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William PaleyWilliam PaleyDESIGNDESIGN
Darwin & WallaceDarwin & WallaceEVOLUTIONEVOLUTION
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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
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• How do we recognise evolution?
• What causes evolution?
• Does evolution lead to perfection?
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What is evolution?
Decent with modification
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What is evolution?
We can redefine evolution as a change over time
Trait value
Time t Time t+x
Low High
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• How do we recognise evolution?
• What causes evolution?
• Does evolution lead to perfection?
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Causes of Evolution
There are 5 causes ‘The accidental toolkit’:
• Natural selection• Genetic drift• Mutation• Gene flow• Nonrandom mating
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Causes of Evolution
1. Natural Selection
There are 3 important points:
• Variation
• Differential success
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Causes of Evolution
1. Natural Selection
There are 3 important points:
• Variation
• Differential success
• Inheritance
Over time there will be mainly white individuals
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Causes of Evolution
1. Natural Selection
Fitness
Differences in reproductive success
- relative contribution to the next generation • survival • access to mates • breeding success
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Causes of Evolution
1. Natural SelectionExample: the peppered moth
Coloration is a camouflage:
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Causes of Evolution
1. Natural SelectionExample of the industrial melanism of the peppered moth
% b
lack
for
m
1800 1900 2000
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Causes of Evolution
2. Genetic DriftRandom changes in the frequency of traits to chance factors
Occurs under 2 conditions: founder effect bottleneck effect
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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
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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
ons
100
50
Before crash
RARE
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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
ber
of l i
ons
100
50
After crash
COMMON
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Causes of Evolution
3. Mutation
Changes in an organism’s DNA
Hopeful monsters
Probably of little importance
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Causes of Evolution
4. Gene Flow
Changes due to movement from one place to another
20% RED
+ 2 REDS 27% RED
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Causes of Evolution
5. Nonrandom Mating
Individuals with particular traits are more likely to mateSexual Selection
Boys fight Boys look fetching
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Causes of Evolution
5. Nonrandom Mating
Boys fight - inter-sexual competition
The winner will mate
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Causes of Evolution
5. Nonrandom Mating
Boys look fetching - intra-sexual competition
The male with the best ornament will be chosen
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• How do we recognise evolution?
• What causes evolution?
• Does evolution lead to perfection?
![Page 25: Causes of Evolution Ruedi Nager Campbell et al. Chapter 23](https://reader036.vdocuments.site/reader036/viewer/2022081802/5515cb0455034693758b4ae7/html5/thumbnails/25.jpg)
Does Evolution lead to Perfection
Does the ability to perform improve? - ADAPTATION
Just-so-stories
The elephant’s child
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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
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Does Evolution lead to Perfection
The course of evolution depends on:
• Historical constraints
• Existing variation
• Compromise
• ‘Accidental toolkit’
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The Tale of the Monkey
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The Tale of the Monkey
Natural Selection Edits Variation
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Variation is the fuel of evolution- next
Evolution is not the work of a designer, but the work of a tinkerer.