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Published byJake Vaughan Modified over 11 years ago
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Causes of Evolution Ruedi Nager Campbell et al. Chapter 23
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William Paley DESIGN Darwin & Wallace EVOLUTION
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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
Time t Time t+x Low High Trait value We can redefine evolution as a change over time
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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
Differences in reproductive success Fitness - relative contribution to the next generation • survival • access to mates • breeding success
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Causes of Evolution 1. Natural Selection Example: the peppered moth
Coloration is a camouflage:
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Causes of Evolution 1. Natural Selection
Example of the industrial melanism of the peppered moth % black form
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Causes of Evolution 2. Genetic Drift
Random 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
Before crash RARE Bottleneck effect - when only a small fraction of the population survives that is no longer representative Example: Lions living in the Ngorogoro Number of lions 100 50
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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 100 After crash Number of lions 50 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 mate Sexual 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?
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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? Foraging efficiency Bill size Adaptation happens only by selection, all other changes are like a lottery
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Does Evolution lead to Perfection
Existing variation The course of evolution depends on: Historical constraints Compromise ‘Accidental toolkit’
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The Tale of the Monkey
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The Tale of the Monkey 1 10 20 Natural Selection Edits Variation
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Evolution is not the work of a designer, but the work of a tinkerer.
Variation is the fuel of evolution - next
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