First year SBC174 Evolution course - week 2 1. NeoDarwinism/ModernSynthesis 2. Major transitions in Evolution 3. Geological Timescales 4. Some drivers of evolution

1. Mini-summary of week 1

2. Specific Questions/Comments
In 1800s, fossils showed species that no longer existed:
Some (e.g. Cuvier): !
Catastrophism: Fossils show extinct species (due to major,
sudden, catastrophic events).
Geologists (Hutton, Lyell):
Uniformitarianism: Changes in nature are gradual.

3. 3 Schools of evolutionary thought
• Linneaus: each species was separately
created.
• Lamarck: characteristics acquired by an
individual are passed on to offspring.
•Darwin & Wallace: evolution as
descent with modification.

4. Evolution by Natural Selection
• There is inherited variation within species.!
• There is competition for survival within species.!
• Genetically inherited traits affect reproduction or survival. Thus the
frequencies of variants change.
Evolutionary fitness:
A measure of the ability of genetic material to perpetuate itself
in the course of evolution. Depends on the individual’s ability to
survive, the rate of reproduction and the viability of offspring.!
(Not just numbers of offspring!)

5. Darwin’s evidence for evolution
1. The Fossil Record
2. Comparative Anatomy
3. Comparative Embryology
4. Vestigial Structures
5. Domestication (artificial selection)

6. Paperback 596 pages !
(11 Aug 2005)!
!
Publisher: Oxford University Press!

8. Natural selection leads to adaptive
change
• But environmental conditions change:
What was advantageous yesterday may be a disadvantage today.
Evolution=change doesn’t only
occur by natural selection!!
!
• Also: !
• genetic drift!
• (sexual selection)!
• artificial selection (selective breeding)!
• mutation

10. “Neo-Darwinism”
or
“The Modern Synthesis”
The same thing... but with better understanding of
how things work.
• Darwin’s Theory of Evolution by Natural Selection (1859)!
• Mendel’s Laws of Heredity (1866, 1900; see SBS 008)!
• Cytogenetics (1902, 1904 - )!
• Population Genetics (1908; see Lectures 7-12) !
• Molecular genetics (1970s- ; see SBS 633/210 and Lecture 6)
•More stuff since then (cultural evolution, epigenetics, etc...)

11. Gregor Mendel
(1822-1884)
Austrian Monk,!
"father of genetics"
Worked out the basic
laws of inheritance:!
1. Segregation !
2. independent
assortment
Published “Experiments on Plant Hybridization” in 1865/1866

12. J.B.S. Haldane (1892-1964)
“The Causes of Evolution” (1932)
first major contribution
explaining natural selection
in terms of mathematical
consequences of mendelian
genetics.
modern evolutionary
synthesis
With Fisher and Wright, one of the founders of population genetics.
Hybridization & speciation
Great science populariser

13. J.B.S. Haldane (1892-1964)
• “The Creator, if He exists, has a special preference for beetles.”
(observing that 25% of known species are beetles)!
• coined the word “clone” (from the Greek word for twig) in his speech
“Biological Possibilities for the Human Species of the Next Ten
Thousand Years” (1963),!
•“Now my own suspicion is that the Universe is not only queerer than we
suppose, but queerer than we CAN suppose”

14. R.A. Fisher (1890-1962)
Major contributions:!
• Statisticts (lots) - e.g.
Analysis of Variance!
• Experimental Design!
• Theory of population
genetics!
• 1930 book: ” The Genetical
Theory of Natural Selection.”

15. Theodosius Dobzhansky
(1900-1975)
“Nothing in Biology makes sense
except in the light of evolution”. !
!
Genetics and the Origin of
Species, published in 1937.
Combined:!
• lab work with study of variation in the wild!
• European & US research cultures

16. Ernst Mayr (1904-2005)
• Definition of species!
• How species evolve

17. William D. Hamilton (1936 - 2000)
Explained weird (i.e. unequal)
sex ratios
Explained how natural selection
acts on social behaviour (“kin
selection”)
relatedness * benefit > cost

18. John Maynard-Smith (1920-2004)
Most widely known for
•applying game theory to
evolutionary biology
•two-fold cost of sex:
1. finding a mate!
2. only have babies

19. 1976
• Dawkins summarized popularized the kin selection arguments of W.
D. Hamilton, George R. Price and John Maynard Smith

20. Summary/overview

21. EVOLUTION!
“descent with modification”

22. Patterns and processes in
evolutionary thought
New
hypotheses
New
understanding
of evolutionary!
processes
New
research
New
findings/
observations

23. EVOLUTION!
“descent with modification”
• Fossil record!
• Dating methods!
• Molecular evolution!
• Molecular clocks!
• Population genetics
New
understanding
of evolutionary!
processes
• Mechanisms!
• Environmental drivers!
•climate!
•continental drift!
•extinctions...
New
hypotheses
The Modern Synthesis
New
research
New
findings/
observations

24. What next?
• Epigenetics!
• Cultural transmission!
• Niche construction
“Extended Evolutionary Synthesis” ?
• Evodevo!
• Comparative genomics!
• Systems Biology
“Postmodern Synthesis” ?

26. Schedule
1. Major transitions in evolution
2. Geological timescales!
3. Major geological drivers of evolution !
4. Recent major extinction events

27. Major transitions?
1. Smaller entities coming together to form larger entities. (e.g.
eukaryotes, multicellularity, colonies...)!
2. Smaller entities become differentiated as part of larger entity. (e.g.
organelles, anisogamy, tissues, castes...)!
3. Smaller entities are often unable to replicate without the larger
entity. (e.g. organelles, tissues, castes...).!
4. The smaller entities can disrupt the development of the larger entity,
(e.g. Meiotic drive, parthenogenesis, cancer...)!
5. New ways of transmitting information arise (e.g. DNA-protein,
indirect fitness...)
Maynard Smith and Szathmary 1995

28. Major transitions: early life
1953 Miller-Urey “primitive soup”
experiment
350° vs 0°
➔ organic molecules

29. Major transitions: early life
•Organic molecules ≠ Life!
•Early life:!
•Hereditary replication!
•Compartmentalization!
!
• First hereditary information?

30. Phylogenetic Tree of Life
Bacteria
Green
Filamentous
Spirochetes bacteria
Gram
positives
Proteobacteria
Cyanobacteria
Planctomyces
Bacteroides
Cytophaga
Thermotoga
Aquifex
Archaea Eukaryota
Halophiles
Methanosarcina
Methanobacterium
Methanococcus
T. celer
Thermoproteus
Pyrodicticum
Entamoebae Slime
molds Animals
Fungi
Plants
Ciliates
Flagellates
Trichomonads
Microsporidia
Diplomonads
last universal common
ancestor (LUCA)
Woese 1990 tree based on ribosomalRNA sequences

31. Major transitions: early life
•Organic molecules ≠ Life!
•Early life of simple replicators:!
•Hereditary replication!
•Compartmentalization!
!
• First hereditary information?!
•Probably RNA: Genetic information (that can be copied)
+ Enzymatic activity.
•Amino-acids (initially as co-factors)!
•DNA (much more stable than RNA)!
• Linkage of replicators (chromosomes)

32. Major transitions: Prokaryote to Eukaryote
Prokaryotic cell
Cell membrane
infoldings
Cell membrane
Cytoplasm
Nucleoid
(containing DNA)
Endomembrane system
Nuclear membrane
Endoplasmic reticulum
Nucleus
Proteobacterium
Mitochondria
Cyanobacterium
Chloroplasts
Mitochondrion
†
†
†
1 A prokaryote grows in size
and develops infoldings in its
cell membrane to increase its
surface area to volume ratio.
2 The infoldings eventually pinch off
from the cell membrane, forming
an early endomembrane system.
It encloses the nucleoid, making a
membrane-bound nucleus.
This is the first eukaryote.
3
5 Some eukaryotes go on to acquire additional
endosymbionts—the cyanobacteria, a group
of bacteria capable of photosynthesis.
They become chloroplasts.
Ancestor of plants and algæ
Ancestor of animals, fungi,
and other heterotrophs
First eukaryote
The aerobe's ability to use
oxygen to make energy be-comes
an asset for the host,
allowing it to thrive in an in-creasingly
oxygen-rich environ-ment
as the other eukaryotes
go extinct. The proteobacterium
is eventually assimilated and
becomes a mitochondrion.
Some eukaryotes go on to ac-quire
additional endosymbionts
— the cyanobacteria, a group of
bacteria capable of photosynthe-
Anaerobic (oxygen using) proteo- sis. They become chloroplasts.
bacterium enters the eukaryote,
either as prey or a parasite, and
manages to avoid digestion. It
becomes an endosymbiont, or a
cell living inside another cell.

33. Major transitions: sex
• See later lectures Week .

34. Major transitions: multicellularity

35. Major transitions: multicellularity
Green algae: Inspiration for what may have occurred: Volvocales

36. Major transitions: multicellularity
Green algae: Inspiration for what may have occurred: Volvocales

37. e.g.: artificial selection for
multicellularity in S. cerevisiae yeast
Ratcliff et al 2012

38. Major transitions: multicellularity
Green algae: Inspiration for what may have occurred: Volvocales

39. Volvox
Somatic cells
Gonidia

40. Major transitions:
eusociality
• Solitary lifestyle -- Eusociality!
1. Reproductive division of labor !
2. Overlapping generations (older
offspring help younger offspring)!
3. Cooperative care of young!
Eg: ants, bees, wasps, termites. But also:
naked mole rats, a beetle, a shrimp...

41. Major transitions: eusociality !
• Hamilton’s rule: genes for altruism increase in frequency when:
r ₒ C
indirect fitness benefits to the receiver (B) ,
reduced by the coefficient of relatedness (r) !
Hamilton, 1964
B
between altruist receiver,
exceeds costs to the altruist (C).
•General framework: Kin selection: can favor the reproductive success
of an organism's relatives (ie. indirect fitness), even at a cost to the
organism's own survival and reproduction.

42. © Alex Wild others

43. Similar diversity of lifestyles!

44. Atta leaf-cutter ants
© National Geographic

45. Atta leaf-cutter ants
© National Geographic

46. Atta leaf-cutter ants
© National Geographic

48. Oecophylla Weaver ants
© ameisenforum.de

49. © ameisenforum.de
Fourmis tisserandes

50. © ameisenforum.de
Oecophylla Weaver ants

51. © wynnie@flickr © forestryimages.org

52. Tofilski et al 2008
Forelius pusillus

53. Forelius pusillus hides the nest entrance at night
Tofilski et al 2008

54. Forelius pusillus hides the nest entrance at night
Tofilski et al 2008

55. Forelius pusillus hides the nest entrance at night
Tofilski et al 2008

56. Forelius pusillus hides the nest entrance at night
Tofilski et al 2008

57. Forelius pusillus hides the nest entrance at night
Avant
Workers staying outside die
« preventive self-sacrifice »
Tofilski et al 2008

58. Dorylus driver ants: ants with no home
© BBC

59. Animal biomass (Brazilian rainforest)
Mammals
Birds
Reptiles
Other insects Amphibians
from Fittkau Klinge 1973
!
Earthworms
!
!
Spiders
Soil fauna excluding
earthworms,
ants termites
Ants termites

60. Schedule
1. Major transitions in evolution!
2. Geological timescales
3. Major geological drivers of evolution !
4. Recent major extinction events

61. “Complexity of life” didn’t
increase linearly.
2. Geological time scales
Defined by changes in flora and fauna (seen in fossil record).
Eon Era Period Epoch!

62. Geological timescales: Eon Era
Period Epoch
4550 Ma:
Hominids
Mammals
Land plants
Animals
Multicellular life
Eukaryotes
Prokaryotes
Hadean
Archean
Proterozoic
Paleozoic
Mesozoic
Cenozoic
4527 Ma:
Formation of the Moon
4.6 Ga
4 Ga
3.8 Ga
3 Ga
2.5 Ga
2 Ga
First vertebrate land animals
1 Ga
542 Ma
251 Ma 65 Ma
ca. 4000 Ma: End of the
Late Heavy Bombardment;
first life
ca. 3500 Ma:
Photosynthesis starts
ca. 2300 Ma:
Atmosphere becomes oxygen-rich;
ca. 380 Ma:
ca. 530 Ma:
Cambrian explosion
750-635 Ma:
Two Snowball Earths
230-65 Ma:
Dinosaurs
2 Ma:
First Hominids
Ma = Million years ago
Ga = Billion years ago
Eon
Eon
Eon
Era
Era
Era
Phanerozoic!
Eon

63. End of Proterozoic biota
Dickinsonia

64. Geological timescales: Eon Era
Period Epoch
4550 Ma:
Hominids
Mammals
Land plants
Animals
Multicellular life
Eukaryotes
Prokaryotes
Hadean
Archean
Proterozoic
Paleozoic
Mesozoic
Cenozoic
4527 Ma:
Formation of the Moon
4.6 Ga
4 Ga
3.8 Ga
3 Ga
2.5 Ga
2 Ga
First vertebrate land animals
1 Ga
542 Ma
251 Ma 65 Ma
ca. 4000 Ma: End of the
Late Heavy Bombardment;
first life
ca. 3500 Ma:
Photosynthesis starts
ca. 2300 Ma:
Atmosphere becomes oxygen-rich;
ca. 380 Ma:
ca. 530 Ma:
Cambrian explosion
750-635 Ma:
Two Snowball Earths
230-65 Ma:
Dinosaurs
2 Ma:
First Hominids
Ma = Million years ago
Ga = Billion years ago
Eon
Eon
Eon
Era
Era
Era
Phanerozoic!
Eon

65. Biodiversity during the Phanerozoic
All Genera
Well-Resolved Genera
Long-Term Trend
The “Big 5” Mass Extinctions
Other Extinction Events
542 500 450 400 350 300 250 200 150 100 50 0
5
4
3
2
1
0
Millions of Years Ago
Thousands of Genera
Cm O S D C P T J K Pg N
Cambrian

66. Trilobites
Cambrian to late permian
17,000 known species!

67. Biodiversity during the Phanerozoic
All Genera
Well-Resolved Genera
Long-Term Trend
The “Big 5” Mass Extinctions
Other Extinction Events
542 500 450 400 350 300 250 200 150 100 50 0
5
4
3
2
1
0
Millions of Years Ago
Thousands of Genera
Cm O S D C P T J K Pg N
Cambrian
Permian Triassic Jurassic

68. Geological timescales: Eon Era
Period Epoch
4550 Ma:
Hominids
Mammals
Land plants
Animals
Multicellular life
Eukaryotes
Prokaryotes
Hadean
Archean
Proterozoic
Paleozoic
Mesozoic
Cenozoic
4527 Ma:
Formation of the Moon
4.6 Ga
4 Ga
3.8 Ga
3 Ga
2.5 Ga
2 Ga
First vertebrate land animals
1 Ga
542 Ma
251 Ma 65 Ma
ca. 4000 Ma: End of the
Late Heavy Bombardment;
first life
ca. 3500 Ma:
Photosynthesis starts
ca. 2300 Ma:
Atmosphere becomes oxygen-rich;
ca. 380 Ma:
ca. 530 Ma:
Cambrian explosion
750-635 Ma:
Two Snowball Earths
230-65 Ma:
Dinosaurs
2 Ma:
First Hominids
Ma = Million years ago
Ga = Billion years ago
Eon
Eon
Eon
Era
Era
Era
Phanerozoic!
Eon

69. Early Permian mammal-like reptiles
Dimetrodon!
(sub-class Synapsida = “mammal-like reptiles”)

70. Geological timescales: Eon Era
Period Epoch
4550 Ma:
Hominids
Mammals
Land plants
Animals
Multicellular life
Eukaryotes
Prokaryotes
Hadean
Archean
Proterozoic
Paleozoic
Mesozoic
Cenozoic
4527 Ma:
Formation of the Moon
4.6 Ga
4 Ga
3.8 Ga
3 Ga
2.5 Ga
2 Ga
First vertebrate land animals
1 Ga
542 Ma
251 Ma 65 Ma
ca. 4000 Ma: End of the
Late Heavy Bombardment;
first life
ca. 3500 Ma:
Photosynthesis starts
ca. 2300 Ma:
Atmosphere becomes oxygen-rich;
ca. 380 Ma:
ca. 530 Ma:
Cambrian explosion
750-635 Ma:
Two Snowball Earths
230-65 Ma:
Dinosaurs
2 Ma:
First Hominids
Ma = Million years ago
Ga = Billion years ago
Eon
Eon
Eon
Era
Era
Era
Phanerozoic!
Eon

71. Life
Earth
Eukaryotes
Homo sapiens: 5 meters
Whitechapel: Dinosaurs extinct
NHM: first tetrapod
Hammersmith: Cambrian explosion

72. Schedule
1. Major transitions in evolution!
2. Geological timescales!
3. Major geological drivers of evolution
4. Recent major extinction events

73. 3. Major geological drivers of evolution
Conditions on earth change.
•Tectonic movement (of continental plates)!
•Vulcanism!
•Climate change!
•Meteorites

74. Plate tectonics
2 1
3
4 5

75. Crustal plates and continental drift

76. Recmeonvt ecmonetnintse..n. tal
LAURASIA
GONDWANA
Triassic 200
TETHYS
Equator Mya
SEA
Pangaea - single
supercontinent

77. Fossil distribution
Gondwana

78. Earthquakes
• Some tectonic movement is violent.!
•E.g. 2004 Sumatra earthquake tsunami...

79. Vulcanism
• Local climate change (e.g. thermal vents, hot springs...)!
•Global climate change: Emission of gasses particles.!
•New geological barriers (migration...)!
•New islands (“Malay archipelago”,
Galapagos... Hawaii... )
Deccan traps
Eyjafjall
ajokull

80. Climate change
(since Cambrian)