Lec141 – Evolution
L1 – The History of Evolution
Science:
1. Identify problem + raise question
2. Collect data by observation or experiment
3. Generate hypothesis
4. More data of hypothesis rejected
History:
Aristotle: 300BC -> Life arises of nothing
Francesco Redi 1668 experiment: -> life comes from existing life
1. compared covered + uncovered meat
2. flies only emerged from uncovered meat as flies had access to meat + laid eggs
Charles Darwin 1809-1882
On the Origin of Species by Means of Natural Selection 1859
Alfred Russel Wallace 1823-1913
Independently came up with same idea
Joint paper with Darwin in 1858
Darwinian Evolution
• Did not work in isolation
1. Beagle voyages -> Galapagos Islands in S. America
• Observed finches with variations in morphologies eating different types of foods
➔ Different morphology -> better at eating different foods -> to reduce competition
2. Bred pigeons + plants
Selected parents -> particular traits in offspring
Darwin’s Inspiration:
1. Carl Linnaeus’s classification scheme:
Some species more similar than others
Invented binomial nomenclature
2. Charles Lyell 1797-1875
Principles of Geologist -> rock formation taken long time to form
➔ Evolution had the time needed to work
3. Thomas Malthus 1766-1834
Essay on the Principle of Population -> More offspring produced than survive -> creates competition
Religious Opposition:
Church = powerful
Creation myths accepted
Thomas Huxley = Darwin’s Bulldog
Argued in meetings with bishops + sceptics -> Darwin avoids conflicts
Neo-Darwinism:
Darwin did not know genetic + heritability mechanism
Darwin’s ideas + advanced genetic understanding
1. Gregor Mendel 1822-1884
Austrain monk -> showed traits heritable in peas
Work unnoticed in his lifetime
,2. Ronals Fisher 1890-1962
English statistician
The Genetical Theory of Natural Selection 1930
➔ Maths in Neo-Darwinism
3. James Watson + Francis Crick:
Discover DNA structure 1953 = double helix allows replication
4. Sewall Wright 1889-1988
Evolution and the Genetics of Populations
Basis for modern population genetics
The Modern View:
1. George Williams
Selection acts on individuals not populations
Individuals compete against each other + Only succeed if reproduce themselves
2. Richard Dawkins
Selection acts at gene level bodies are genes way of reproducing
Genes grouped into individual organism
Evolution:
• Some variation is heritable so offspring resemble parents
• More offspring produced than can be maintained by resources -> Competition
➔ Limiting resource drives competition
Evolution = Ongoing + dynamic
Successful: surviving long enough to reproduce
Selection: individuals live or die depending on the presence/magnitude of the trait which influences
the outcome of competition
Evolution: results in adaptation or changes in gene pool
Gene pool: traits within population
Selection pressures vary in time + space
Organisms do not aim to fit a niche -> evolution = blind
Organisms do not aim to become more human-like
L2 - Evidence for Evolution
Direct experiment, biogeography, fossil, homology, embryology, comparative behaviour +
biochemistry, hierarchal organisation of life
1. Direct Experiment – Guppies
Native to S. America
Intense male competition + external fertilisation
Females prefer to mate with males with more spots
Large predator = Crenicichila alta = eats adults
Small predator = rivulus hartii = eats yound
Pools with LP have males with less orange + spotty
Predation risk increased -> less sexual competition among males
, John Endler’s Experiment:
1) Artificial pools with guppies
After generations – spot number increased
2) Add SP = eats random young males -> spots slightly greater than control
3) Add LP = eats orange + spotty males -> decreases number of spots
➔ Direct evidence for evolutionary change over short timescale
➔ Effect of predation reduces colouration in population through natural selection
2. Biogeography: distribution of biological organisms
Living organisms not distributed as widely as their potential evidence
Similar organisms occur in different continents
➔ Distribution make sense due to continental drift after Pangaea 250MYA
o E.g. Ratites (ostrich, Rhea, Emu..) from common ancestor but separated due to
continental split
o Oceanic islands = few but endemic species -> resemble mainland species e.g.
marine iguana of Galapagos, giant tortoise
o Madagascar separated from continents in middle of Pangaea -> species had
more time to evolve -> endemic
o New Zealand split from Gondwana before mammals evolved -> only
native/immigrant mammals = bats, cetaceans, seals
Convergent Evolution: similar available niches -> same advantageous characteristics
3. Fossil Record
Direct + fragmentary record of evolution
Most remains of hard parts of organisms buried in sediments
Common in aquatic environments
1) Soft parts eaten + rots
2) Sediment settles over hard parts
3) Mould in sediment layer
4) Minerals from water deposit inside of mould -> cast
5) Erosion or land movement reveals fossil
Stratigraphy: Layers of sediment can be aged -> time estimate of when fossil was formed
Evolution is continuum e.g. liassic oysters -> hard to determine when new species
Archaeopteryx fossil -> animal = feathers, teeth, boned tail = avian + reptiles
4. Homology, Vestigial Structures + Homoplasy
Homologous characteristics: similar structures from common ancestor
Analogous characteristics: similar appearance + function but fundamentally different + from
separate evolutionary origins
5. Embryology
Similarities among vertebrate embryos e.g. gill slits, tail
6. Comparative behaviour + biochemistry
Comparative behaviour: greater similarity = more closely related
Biochemistry: DNA + Haemoglobin structure differences -> phylogenetic trees
DNA contains record of evolutionary change -> mutations change genes -> family trees =
how different organisms are
Evolution results from continuous changes in genetic composition
Closely related organisms have less genetic differences
L1 – The History of Evolution
Science:
1. Identify problem + raise question
2. Collect data by observation or experiment
3. Generate hypothesis
4. More data of hypothesis rejected
History:
Aristotle: 300BC -> Life arises of nothing
Francesco Redi 1668 experiment: -> life comes from existing life
1. compared covered + uncovered meat
2. flies only emerged from uncovered meat as flies had access to meat + laid eggs
Charles Darwin 1809-1882
On the Origin of Species by Means of Natural Selection 1859
Alfred Russel Wallace 1823-1913
Independently came up with same idea
Joint paper with Darwin in 1858
Darwinian Evolution
• Did not work in isolation
1. Beagle voyages -> Galapagos Islands in S. America
• Observed finches with variations in morphologies eating different types of foods
➔ Different morphology -> better at eating different foods -> to reduce competition
2. Bred pigeons + plants
Selected parents -> particular traits in offspring
Darwin’s Inspiration:
1. Carl Linnaeus’s classification scheme:
Some species more similar than others
Invented binomial nomenclature
2. Charles Lyell 1797-1875
Principles of Geologist -> rock formation taken long time to form
➔ Evolution had the time needed to work
3. Thomas Malthus 1766-1834
Essay on the Principle of Population -> More offspring produced than survive -> creates competition
Religious Opposition:
Church = powerful
Creation myths accepted
Thomas Huxley = Darwin’s Bulldog
Argued in meetings with bishops + sceptics -> Darwin avoids conflicts
Neo-Darwinism:
Darwin did not know genetic + heritability mechanism
Darwin’s ideas + advanced genetic understanding
1. Gregor Mendel 1822-1884
Austrain monk -> showed traits heritable in peas
Work unnoticed in his lifetime
,2. Ronals Fisher 1890-1962
English statistician
The Genetical Theory of Natural Selection 1930
➔ Maths in Neo-Darwinism
3. James Watson + Francis Crick:
Discover DNA structure 1953 = double helix allows replication
4. Sewall Wright 1889-1988
Evolution and the Genetics of Populations
Basis for modern population genetics
The Modern View:
1. George Williams
Selection acts on individuals not populations
Individuals compete against each other + Only succeed if reproduce themselves
2. Richard Dawkins
Selection acts at gene level bodies are genes way of reproducing
Genes grouped into individual organism
Evolution:
• Some variation is heritable so offspring resemble parents
• More offspring produced than can be maintained by resources -> Competition
➔ Limiting resource drives competition
Evolution = Ongoing + dynamic
Successful: surviving long enough to reproduce
Selection: individuals live or die depending on the presence/magnitude of the trait which influences
the outcome of competition
Evolution: results in adaptation or changes in gene pool
Gene pool: traits within population
Selection pressures vary in time + space
Organisms do not aim to fit a niche -> evolution = blind
Organisms do not aim to become more human-like
L2 - Evidence for Evolution
Direct experiment, biogeography, fossil, homology, embryology, comparative behaviour +
biochemistry, hierarchal organisation of life
1. Direct Experiment – Guppies
Native to S. America
Intense male competition + external fertilisation
Females prefer to mate with males with more spots
Large predator = Crenicichila alta = eats adults
Small predator = rivulus hartii = eats yound
Pools with LP have males with less orange + spotty
Predation risk increased -> less sexual competition among males
, John Endler’s Experiment:
1) Artificial pools with guppies
After generations – spot number increased
2) Add SP = eats random young males -> spots slightly greater than control
3) Add LP = eats orange + spotty males -> decreases number of spots
➔ Direct evidence for evolutionary change over short timescale
➔ Effect of predation reduces colouration in population through natural selection
2. Biogeography: distribution of biological organisms
Living organisms not distributed as widely as their potential evidence
Similar organisms occur in different continents
➔ Distribution make sense due to continental drift after Pangaea 250MYA
o E.g. Ratites (ostrich, Rhea, Emu..) from common ancestor but separated due to
continental split
o Oceanic islands = few but endemic species -> resemble mainland species e.g.
marine iguana of Galapagos, giant tortoise
o Madagascar separated from continents in middle of Pangaea -> species had
more time to evolve -> endemic
o New Zealand split from Gondwana before mammals evolved -> only
native/immigrant mammals = bats, cetaceans, seals
Convergent Evolution: similar available niches -> same advantageous characteristics
3. Fossil Record
Direct + fragmentary record of evolution
Most remains of hard parts of organisms buried in sediments
Common in aquatic environments
1) Soft parts eaten + rots
2) Sediment settles over hard parts
3) Mould in sediment layer
4) Minerals from water deposit inside of mould -> cast
5) Erosion or land movement reveals fossil
Stratigraphy: Layers of sediment can be aged -> time estimate of when fossil was formed
Evolution is continuum e.g. liassic oysters -> hard to determine when new species
Archaeopteryx fossil -> animal = feathers, teeth, boned tail = avian + reptiles
4. Homology, Vestigial Structures + Homoplasy
Homologous characteristics: similar structures from common ancestor
Analogous characteristics: similar appearance + function but fundamentally different + from
separate evolutionary origins
5. Embryology
Similarities among vertebrate embryos e.g. gill slits, tail
6. Comparative behaviour + biochemistry
Comparative behaviour: greater similarity = more closely related
Biochemistry: DNA + Haemoglobin structure differences -> phylogenetic trees
DNA contains record of evolutionary change -> mutations change genes -> family trees =
how different organisms are
Evolution results from continuous changes in genetic composition
Closely related organisms have less genetic differences
