Sbc174 evolution 2014 week2

Mini-summary of week 1

Specific Questions/Comments

Geologists (Hutton, Lyell):Uniformitarianism: Changes in nature are gradual.

In 1800s, fossils showed species that no longer existed:

Some (e.g. Cuvier): !Catastrophism: Fossils show extinct species (due to major, sudden, catastrophic events).

3 Schools of evolutionary thought

• Lamarck: characteristics acquired by an individual are passed on to offspring.

• Linneaus: each species was separately created.

• Darwin & Wallace: evolution as descent with modification.

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.

(Not just numbers of offspring!)

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.!

1. The Fossil Record2. Comparative Anatomy3. Comparative Embryology4. Vestigial Structures5. Domestication (artificial selection)

Darwin’s evidence for evolution

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

!

• Also: !• genetic drift!• (sexual selection)!• artificial selection (selective breeding)!• mutation

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!!

“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...)

Gregor Mendel (1822-1884)

Worked out the basic laws of inheritance:!1. Segregation !2. independent

assortment

Austrian Monk,!"father of genetics"

Published “Experiments on Plant Hybridization” in 1865/1866

http://en.wikipedia.org/wiki/Genetics

http://en.wikipedia.org/wiki/Experiments_on_Plant_Hybridization

J.B.S. Haldane (1892-1964)

With Fisher and Wright, one of the founders of population genetics.

first major contribution explaining natural selection in terms of mathematical consequences of mendelian genetics.

“The Causes of Evolution” (1932)

modern evolutionary synthesis

Great science populariserHybridization & speciation

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”

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.”

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

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

William D. Hamilton (1936 - 2000)

Explained how natural selection acts on social behaviour (“kin selection”)

relatedness * benefit > cost

Explained weird (i.e. unequal) sex ratios

John Maynard-Smith (1920-2004) Most widely known for

•two-fold cost of sex:

•applying game theory to evolutionary biology

1. finding a mate!2. only � have babies

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

1976

http://en.wikipedia.org/wiki/Kin_selection

http://en.wikipedia.org/wiki/W._D._Hamilton

http://en.wikipedia.org/wiki/George_R._Price

http://en.wikipedia.org/wiki/John_Maynard_Smith

Summary/overview

EVOLUTION!“descent with modification”

Patterns and processes in evolutionary thought

New hypotheses

New understanding of evolutionary!

processes

New research

New findings/

observations

• Fossil record!• Dating methods!• Molecular evolution!• Molecular clocks!• Population genetics

• Mechanisms!• Environmental drivers!

•climate!•continental drift!•extinctions...

The Modern Synthesis

EVOLUTION!“descent with modification”

New hypotheses

New understanding of evolutionary!

processes

New research

New findings/

observations

What next?• Epigenetics!

• Cultural transmission!

• Niche construction

“Extended Evolutionary Synthesis” ?

• Evodevo!

• Comparative genomics!

• Systems Biology

“Postmodern Synthesis” ?

Schedule

1. Major transitions in evolution

2. Geological timescales!

3. Major geological drivers of evolution !

4. Recent major extinction events

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

http://en.wikipedia.org/wiki/Eukaryote

Major transitions: early life

1953 Miller-Urey “primitive soup” experiment

350° vs 0°

➔ organic molecules


•Organic molecules ≠ Life!•Early life:!

•Hereditary replication!•Compartmentalization!!

•First hereditary information?

Phylogenetic Tree of Life

BacteriaGreen

FilamentousbacteriaSpirochetes

Grampositives

ProteobacteriaCyanobacteria

Planctomyces

BacteroidesCytophaga

Thermotoga

Aquifex

HalophilesMethanosarcina

MethanobacteriumMethanococcus

T. celerThermoproteus

Pyrodicticum

Entamoebae Slimemolds Animals

Fungi

PlantsCiliates

Flagellates

Trichomonads

Microsporidia

Diplomonads

Archaea Eukaryota

last universal common ancestor (LUCA)

Woese 1990 tree based on ribosomalRNA sequences


•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)

Major transitions: Prokaryote to Eukaryote

Prokaryotic cell

Cell membrane infoldings

Cell membrane

Cytoplasm

Nucleoid(containing DNA)

Endomembrane system

Endoplasmic reticulumNuclear membrane

Nucleus

Proteobacterium

Mitochondria

Cyanobacterium

Chloroplasts

Mitochondrion

†

†

†

1 A prokaryote grows in size and develops infoldings in its cell membrane to increase itssurface 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-sis. They become chloroplasts.Anaerobic (oxygen using) proteo-

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.

Major transitions: sex

•See later lectures Week .

Major transitions: multicellularity

Major transitions: multicellularityGreen algae: Inspiration for what may have occurred: Volvocales

http://en.wikipedia.org/wiki/Volvocales

e.g.: artificial selection for multicellularity in S. cerevisiae yeast

Ratcliff et al 2012

Major transitions: multicellularityGreen algae: Inspiration for what may have occurred: Volvocales

http://en.wikipedia.org/wiki/Volvocales

VolvoxSomatic cells

Gonidia

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...

Hamilton, 1964

Major transitions: eusociality!

• Hamilton’s rule: genes for altruism increase in frequency when:

indirect fitness benefits to the receiver (B) ,

B

exceeds costs to the altruist (C).

> Cr ₒ

reduced by the coefficient of relatedness (r) !between altruist & receiver,

•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.

Similar diversity of lifestyles!

© National Geographic

Atta leaf-cutter ants

Oecophylla Weaver ants

© ameisenforum.de

© ameisenforum.de

Fourmis tisserandes

© ameisenforum.de

Oecophylla Weaver ants

Tofilski et al 2008

Forelius pusillus

Tofilski et al 2008

Forelius pusillus hides the nest entrance at night

Avant

Workers staying outside die« preventive self-sacrifice »

Tofilski et al 2008

Forelius pusillus hides the nest entrance at night

Dorylus driver ants: ants with no home

© BBC

Animal biomass (Brazilian rainforest)

from Fittkau & Klinge 1973

Other insects AmphibiansReptiles

Birds

Mammals

!Earthworms

!!

Spiders

Soil fauna excluding earthworms,

ants & termites

Ants & termites

Schedule

1. Major transitions in evolution!

2. Geological timescales

3. Major geological drivers of evolution !


“Complexity of life” didn’t increase linearly.

2. Geological time scalesDefined by changes in flora and fauna (seen in fossil record).

Eon > Era > Period > Epoch!

4550 Ma:

HominidsMammalsLand plantsAnimalsMulticellular lifeEukaryotesProkaryotes

Hadean

Arch

eanProterozoic

Paleozoic

Mesozoic

Cenozoic

4527 Ma:Formation of the Moon

4.6 Ga

4 Ga

3.8 Ga

3 Ga

2.5 Ga

2 Ga

1 Ga

542 M

a

251 Ma65 Ma ca. 4000 Ma: End of the

Late Heavy Bombardment;first life

ca. 3500 Ma:Photosynthesis starts

ca. 2300 Ma:Atmosphere becomes oxygen-rich;

750-635 Ma:Two Snowball Earths

ca. 530 Ma:Cambrian explosion

ca. 380 Ma:First vertebrate land animals

230-65 Ma:Dinosaurs

2 Ma:First Hominids

Ga = Billion years agoMa = Million years ago

Eon

Eon

Eon

EraEra

Era

Phaneroz

oic!

Eon

Geological timescales: Eon > Era > Period > Epoch

End of Proterozoic biota

Dickinsonia

4550 Ma:


Hadean

Arch

eanProterozoic

Paleozoic

Mesozoic

Cenozoic


4.6 Ga

4 Ga

3.8 Ga

3 Ga

2.5 Ga

2 Ga

1 Ga

542 M

a








230-65 Ma:Dinosaurs

2 Ma:First Hominids


Eon

Eon

Eon

EraEra

Era

Phaneroz

oic!

Eon


50100150200250300350400450500 0542

0

1

2

3

4

5

Millions of Years Ago

Thou

sand

s of

Gen

era

Cm O S D C P T J K Pg N

Biodiversity during the PhanerozoicAll Genera

Well-Resolved GeneraLong-Term Trend

The “Big 5” Mass Extinctions

Other Extinction Events

Cambrian

Trilobites

Cambrian to late permian17,000 known species!

50100150200250300350400450500 0542

0

1

2

3

4

5

Millions of Years Ago

Thou

sand

s of

Gen

era

Cm O S D C P T J K Pg N

Biodiversity during the PhanerozoicAll Genera

Well-Resolved GeneraLong-Term Trend

The “Big 5” Mass Extinctions

Other Extinction Events

Cambrian

Permian Triassic Jurassic

4550 Ma:


Hadean

Arch

eanProterozoic

Paleozoic

Mesozoic

Cenozoic


4.6 Ga

4 Ga

3.8 Ga

3 Ga

2.5 Ga

2 Ga

1 Ga

542 M

a








230-65 Ma:Dinosaurs

2 Ma:First Hominids


Eon

Eon

Eon

EraEra

Era

Phaneroz

oic!

Eon


Dimetrodon!(sub-class Synapsida = “mammal-like reptiles”)

Early Permian mammal-like reptiles

4550 Ma:


Hadean

Arch

eanProterozoic

Paleozoic

Mesozoic

Cenozoic


4.6 Ga

4 Ga

3.8 Ga

3 Ga

2.5 Ga

2 Ga

1 Ga

542 M

a








230-65 Ma:Dinosaurs

2 Ma:First Hominids


Eon

Eon

Eon

EraEra

Era

Phaneroz

oic!

Eon


Earth

Life

Eukaryotes

Homo sapiens: 5 meters

Whitechapel: Dinosaurs extinct

NHM

: first tetrapod

Ham

mersm

ith: Cam

brian explosion

Schedule

1. Major transitions in evolution!

2. Geological timescales!

3. Major geological drivers of evolution


3. Major geological drivers of evolution

•Tectonic movement (of continental plates)!

•Vulcanism!

•Climate change!

•Meteorites

Conditions on earth change.

Plate tectonics

12

354

Crustal plates and continental drift

Recent continental movements...

TETHYS SEA

LAURASIA

GONDWANA

EquatorTriassic 200 Mya

Pangaea - single supercontinent

Fossil distribution

Gondwana

Earthquakes

•Some tectonic movement is violent.!

•E.g. 2004 Sumatra earthquake & tsunami...

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

Eyjafjallajokull

Climate change(since Cambrian)

Sbc174 evolution 2014 week2

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