Causes of Evolution Ruedi Nager Campbell et al. Chapter 23

William Paley DESIGN Darwin & Wallace EVOLUTION

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

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 Differences in reproductive success Fitness - relative contribution to the next generation • survival • access to mates • breeding success

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

Causes of Evolution 1. Natural Selection Example of the industrial melanism of the peppered moth % black form 1800 1900 2000

Causes of Evolution 2. Genetic Drift Random 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 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 1960 1975 1990 Number of lions 100 50

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 1960 1975 1990

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 mate Sexual 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? Foraging efficiency Bill size Adaptation happens only by selection, all other changes are like a lottery

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

The Tale of the Monkey

The Tale of the Monkey 1 10 20 Natural Selection Edits Variation

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