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Causes of Evolution Ruedi Nager Campbell et al. Chapter 23.

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Presentation on theme: "Causes of Evolution Ruedi Nager Campbell et al. Chapter 23."— Presentation transcript:

1 Causes of Evolution Ruedi Nager Campbell et al. Chapter 23

2 William Paley DESIGN Darwin & Wallace EVOLUTION

3

4 1.1 x possibilities = 3.6 x years

5 How do we recognise evolution? What causes evolution? Does evolution lead to perfection?

6 What is evolution? Decent with modification

7 What is evolution? We can redefine evolution as a change over time Trait value Time t Time t+x Low High

8 How do we recognise evolution? What causes evolution? Does evolution lead to perfection?

9 Causes of Evolution There are 5 causes The accidental toolkit: Natural selection Genetic drift Mutation Gene flow Nonrandom mating

10 Causes of Evolution 1. Natural Selection There are 3 important points: Variation Differential success

11 Causes of Evolution 1. Natural Selection There are 3 important points: Variation Differential success Inheritance Over time there will be mainly white individuals

12 Causes of Evolution 1. Natural Selection Fitness Differences in reproductive success - relative contribution to the next generation survival access to mates breeding success

13 Causes of Evolution 1. Natural Selection Example: the peppered moth Coloration is a camouflage:

14 Causes of Evolution 1. Natural Selection Example of the industrial melanism of the peppered moth % black form

15 Causes of Evolution 2. Genetic Drift Random changes in the frequency of traits to chance factors Occurs under 2 conditions: founder effect bottleneck effect

16 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

17 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 Number of lions Before crash RARE

18 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 Number of lions After crash COMMON

19 Causes of Evolution 3. Mutation Changes in an organisms DNA Hopeful monsters Probably of little importance

20 Causes of Evolution 4. Gene Flow Changes due to movement from one place to another 20% RED + 2 REDS 27% RED

21 Causes of Evolution 5. Nonrandom Mating Individuals with particular traits are more likely to mate Sexual Selection Boys fightBoys look fetching

22 Causes of Evolution 5. Nonrandom Mating Boys fight - inter-sexual competition The winner will mate

23 Causes of Evolution 5. Nonrandom Mating Boys look fetching - intra-sexual competition The male with the best ornament will be chosen

24 How do we recognise evolution? What causes evolution? Does evolution lead to perfection?

25 Does Evolution lead to Perfection Does the ability to perform improve? - ADAPTATION Just-so-stories The elephants child

26 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 Foraging efficiency

27 Does Evolution lead to Perfection The course of evolution depends on: Historical constraints Existing variation Compromise Accidental toolkit

28 The Tale of the Monkey

29 The Tale of the Monkey Natural Selection Edits Variation

30 Variation is the fuel of evolution - next Evolution is not the work of a designer, but the work of a tinkerer.


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