FUNDAMENTALS OF EARTH SCIENCE I

FALL SEMESTER 2018

Origin and Evolution of Life I & 2“Therefore I should infer from analogy that probably all the organic
beings which have ever lived on this earth have descended fromsome one primordial form…”
On the Origin of Species (Charles Darwin, 1859)✶ What is Life?
■

Characteristics of cellular life
Growth■ Reproduction■ Capacity to evolve■ Nutrients (C, H, O, N, P, S)■ Information-carrying, replicating molecule (RNA, DNA)■ Membrane-bound vesicle■■

Basic requirements of life (Earth’s like)
Liquid water■ Organic molecules■ Energy (chemical reactions, light)■■

Chemical signature■

System out of equilibrium (e.g. O2, left-handed amino acids)✶ What is life?
■• Life basic constituents

C, H, O, N, P, S

C

Carbon has 4 electrons on its outer shell and can form 4bonds with other elements (including itself), as well as
double or even triple bonds.
Carbon atoms form the backbone of organic molecules.

H H
H C C H
H H

EthaneCarbon dioxide

O

Hydrogen cyanide

C

O

H

C

N

✶ What is life?

• Life basic constituents

Abundances of elements in the Solar System✶ What is life?
1. The prokaryotic cell

• Life basic constituents■The cell is the basic unit of life.

Organisms are either unicellular or
Bacteria and Archaea multicellular.
(Unicellular organisms)
Organisms can be classified into 2 groups
based on cell characteristics: prokaryotes andeukaryotes.
Fungi, algae, plants
and animals

Lack a nucleus and other internal
membrane-bound structures

2. The eukaryotic cell

Illust.: Mariana Ruiz Villarreal (Wikipedia)

Evolution by natural selection (Charles Darwin, 1809-1882 – Alfred Russel Wallace, 1823-1913)★ Evolution = process by which organisms
descend from other -different- preexisting
forms (ancestors) through modifications.

Genetic variations: organisms within thesame species show variations in morphology,
physiology* and behavior .

Inheritance: some of these traits can be
inherited by offspring.

Natural selection: If these traits are

Darwin’s sketch of the evolutionary tree of life
* Physiology refers to the functions of livingorganisms and their parts (e.g. nutrition,
movement, reproduction).

beneficial to the organism and increase thechance of survival and reproduction, they will
have more chance to be passed on to offspring- they will be “selected”.
Selective pressure: any phenomenon thatcan reduce the ability of an individual toproduce viable offspring, for example, climatechange, introduction of new predator, newdisease…
Time: over time, selective pressure can change
the genetic make-up of a population and leadto the emergence of a new species

Time

Gradualism

Punctuated equilibrium

Darwin (1859)

Gould and Eldredge (1972)

Present

Slow, gradualevolution

Rapid
evolution with long
periods of stasis

Morphology
Extinction
Speciation

How to reconstruct the evolutionary tree of life?
The fossil record

Phylogenetics

Need to know therate at which
X Ma “Molecularmutations occur!
clock”

Sereno (1999)

Biology, Life on Earth 9th ed.

The amount of differences in DNA orproteins between extant groups is afunction of the time elapsed since they
diverged from a common ancestor.

✶ What is life?

• The 3 domains of life
Prokaryotes

Eukaryotes

Biochemical differences (cell wall structure, genetic material)
Archaea share somesimilarities with Eukarya= EVOLUTIONARY TREE OF LIFE
Modified from Understanding Earth✶ What is life?

• Life strategies: sources of energy and C*

PHOTOSYNTHESISCHEMOSYNTHESIS

1 and 3 = PHOTOTROPHS

2 and 4 = CHEMOTROPHS* Organisms performing photosynthesis but needing another source of C than CO2(ex: carnivorous plants)✶ What is life?

• Life strategies: sources of energy and C

Redox reactions are involved in many important biological processes:■

Photosynthesis: synthesis of large organic molecules from CO2 using
sunlight as the source of energy.

■

Chemosynthesis: synthesis of large organic molecules using the energy
released by inorganic chemical reactions.

■

Cellular respiration: redox reactions with production of energy■

Fermentation (anaerobic cellular respiration): redox reactions in whichorganic molecules serve both as e- donor and e- acceptor, resulting in the
production of energy.

✶ What is life?

• Examples of metabolic pathways

Photoautotrophs

Chemoheterotrophs(plants, cyanobacteria, phytoplankton)(animals, some bacteria, yeast)

Cox et al. (2005)
Wikipedia

Photoheterotrophs(carnivorous plants, some bacteria)!

Yeast (alcoholic fermentation)!

Wikipedia

Wikipedia→ Bacteria
used forNat. Geo.
waste- microbiologyonline.org.uk
Davies (2005)
Chemoautotrophs
water(sulfide-oxidizing bacteria)
treatment
CO2 + 4H2S + O2 → CH2O + 4S + 3H2O
Chemosynthesis performed by bacteria
generates food for tubeworms
Riftia pachyptila
NOAA

Asao and Madigan(2005)
Noah Elhardt (wiki)✶ The first cell
Environmental conditions of the early Earth:■

The Earth formed 4.56 Gyr ago along with the other planets of the Solar
System.

■Meteorite impacts very intense at the beginning of Earth's history anddecreased until 3.9 Gyr (Hadean Eon). Meteorite impacts released a lot of heat.

■

As the Earth cooled down, water vapor condensed
into oceans (oldest sedimentary rocks dated >3.95
Gyr from Canada and ~3.8 Gyr from Greenland).

■Sun fainter than today (less solar heat) but
evidence of liquid water and life… young faintSun paradox■

The primitive atmosphere was possibly composedof hydrogen, nitrogen, carbon dioxide, and water
vapor. NO OR VERY LITTLE FREE OXYGEN (O2)!
→
Environmental conditions at the beginning ofEarth’s history very different from today!

3.8 Gyr sedimentary rocks from Greenland
Mojzsis et al. (1996)✶ The first cell

• Evidence from the geological record

PALEONTOLOGICAL■

Biotic origin

Abiotic origin

Morphological evidence (microfossils andmacroscopic texture, such as microbial mats)!

abiotic origin!

abiotic origin

MINERALOGICAL■

Biomineralization
Berkeley.ac.edu

GEOCHEMICAL■

Biological fractionation of stable isotopes■

Biomarkers = large molecules resulting from biological activity, such! contaminationas polypeptids, triterpenes, steranes
preservation! contamination

Livage (2009)✶ The first cell

• Evidence from the geological record

Biominerals

Indirect precipitationof pyrite (FeS2) by sulfatereducing bacteria

Calcification:
Ca2+ + 2HCO3-

CaCO3 + CO2 + H2OPhotosynthesis:
6H2O + 6CO2 + sunlight → C6H12O6 + 6O2

e.g.: Magnetotactic bacteria

e.g.: Cyanobacteria
Understanding EarthMechanisms of stromatolite formation
SUNLIGHT

Formation of a newbacterial mat

Upward migration of
Cyanobacteria

Sedimentation

Seawater
Bacterial mat

A

Sediment layer

B

C

D

Calcification:
Ca2+ + 2HCO3Photosynthesis:

CaCO3 + CO2 + H2O
6H2O + 6CO2 + sunlight → C6H12O6 + 6O2

✶ The first cell

• Evidence from the geological record

Biological fractionation of stable isotopes
Biological processes result in stable isotope
fractionation (e.g. C, S, N, and Fe):e.g. Photosynthesis→ organic carbon enriched in light 12C→ inorganic carbon depleted in light 12C

By analyzing the isotopic
composition of carbon andother elements in a rocksample, we can knowwhether biological activity
was involved or not.

✶ The first cell■■■

• When did life begin?

Iron and carbon isotope ratios suggest the existence of biologicalactivity as early as 3.8 Gyr, and perhaps even earlier!
~3.5-Gyr old mineralized
microbial mats(stromatolites) andmicrofossils werediscovered in Australia.
Multiple evidence(morphological and isotopic)
supporting the existence ofvarious kinds of microbes
around 3.4-3.2 Gyr (first halfof the Archean).

Understanding Earth

The geological record enables us to set a minimum age for the existence of life.
LIFE EMERGED POSSIBLY BEFORE 3.8 Gyr AND WAS VERY LIKELY PRESENT BY 3.4 Gyr✶ The first cell

• When did life begin?

~3.5-Gyr old mineralized microbial mats (stromatolites) and microfossils were discovered in Australia

Schopf (1993)

Van Krakendonk (2006)

Picture of the metamorphosed sedimentary (ormetasedimentary) rocks analyzed in this study✶ The first cell

• When did life begin?

A

C

B

A)

3.4 Gyr bacteria from Australia(probalby characterized by asulfur-based metabolism, Wacey et al., 2011 )B)

3.4 Gyr rolled-up microbial matfrom South Africa (probably
formed by anoxigenic photosynthetic bacteria, Tice andLowe, 2004 )C)

3.2 Gyr unidentified prokaryotes from South Africa(Javaux et al., 2010)

DD) 3.2 Gyr thermophylic filamentous bacteria from Australia(Rasmussen, 2000).

✶ The Great Oxygenation Event* (GOE)*or Great Oxidation Event
Atmospheric oxygen shows a sharp rise between 2.45-2.32 Gyr

GOE

TIME
From Canfield (2005)✶ The Great Oxygenation Event• Evidence from the geologic record
Examples of evidence suggesting an abrupt rise of atmospheric O2:
1. Redox sensitive elements:
Occurrence of fluvial deposits containing
minerals that would not be stable underoxidizing conditions (e.g.: uraninite, pyrite,and siderite) are rare after 2.3 Gyr.

2.7 Gyr Witwatersrand conglomerate

Uraninite = UO2
Pyrite = FeS2
Siderite = FeCO3
The rounded pebbles in this 2.7 Gyr conglomerateindicate that they were deposited in a stream.
The presence of the pyrite flakes and uraninite
suggests reducing (anaerobic) conditions.

Natural Museum of
Humbolt State Univ.

2. Banded Iron Formations (BIFs):
Banded iron formations are laminated rocks characterized by an alternation of
Si-rich and Fe-rich laminations. Fe-rich laminations are rich in iron oxide(Fe2O3). They are widespread in the Archean and early Proterozoic.

The Iron oxide was deposited when
the anoxic ocean waters (rich indissolved Fe2+) mixed with O2-richwaters (“mass rusting”).

Once the oxidation process wascompleted, O2 started to increase andresulted in the GOE.

Encyclopedia Britannica

Rare BIFs

Abundant BIFs

Modified from Sessions et al. (2009)✶ The Great Oxygenation Event• Origin of O2

Rise in O2 probably linked to the emergence of photosynthetic cyanobacteria
6H2O + 6CO2 + sunlight → C6H12O6 + 6O2■

The timing of the first appearance of cyanobacteria in the fossil record iscontroversial. The earliest, unambiguous occurrence of cyanobacteria is in~2.15 Gyr old rocks from Canada.

■

The existence of older stromatolites (very similar to present-day Shark Bay
stromatolites) suggest that the origin of cyanobacteria may be much older
than 2.15 Gyr (see 3.5 Gyr stromatolites from Australia)■

The geological record and genetic studies suggest that cyanobacteria
originated after anoxygenic photosynthetic bacteria and after various otherbacteria using different metabolic pathways.

B

C

D

(A) 1.9 Gyr cyanobacteria from Canada (Hoffman, 1976), (B) 3.4 Gyr stromatolite from
Western Australia (Allwood et al., 2006), (C) modern stromatolites from Shark Bay, Australia(from britannica.com), and (D) cross section of a modern stromatolite from Shark Bay (fromphysorg.com).

Mechanisms of stromatolite formation
SUNLIGHT
Sedimentation

Formation of a newbacterial mat

Upward migration of
Cyanobacteria

Seawater
Bacterial mat

A

Sediment layer

B

C

D

Calcification:
Ca2+ + 2HCO3Photosynthesis:

CaCO3 + CO2 + H2O
6H2O + 6CO2 + sunlight → C6H12O6 + 6O2

Schirmeister et al. (2011)✶ The Great Oxygenation Event■• Consequences

GOE also called Great Oxygenation Crisis because O2 was toxic foranaerobic bacteria ! likely resulted in First mass extinction!

■■

Emergence of aerobic respiration ! the energetic advantage ofusing O2 as an oxidizing agent in aerobic respiration enabled theevolution of more complex forms of life.

The selective pressure resulting from the GOE related to the toxicityof O2 for anaerobic bacteria may have led to the emergence of the
eukaryotic cell (see Endosymbiont Hypothesis)✶ The Eukaryotic Cell■

Oldest occurrence of fossils of eukaryotes in 1.8 Gyr-old rocks from China

A

B

35 µm

D
100 µmC

A)

1.4 Gyr eukaryote from Canada(Butterfield, 2005),

B)

1.5 Gyr eukaryote from Australia(Javaux et al., 2001),

C)

1.5 Gyr eukaryote from Australia(Knoll et al., 2006), andD) 1.8 Gyr eukaryote from China(Lamb et al., 2009)

35 µm

30 µm

✶ Multicellularity• Advantages■

In a predator-prey relationship, being larger means a greater ability
to engulf preys that are comparatively smaller. Also, larger cells haveless chance to be ingested.

■

Growing larger means more exchange of matter between cell andexterior ! area/volume ratio decreases rapidly ! limit to
growth! ! solution = multicellularity■

Advantages of being multicellular is the specialization of body parts,
additional level of protection (replacement of damaged cells), growthdoes not affect metabolism of individual cells (just add new cells).

Surface of a sphere S = 4 πr23
4πrVolume of a sphere V =3

The ratio S/V drops
rapidly as the size of thesphere increases!

S/V = 3/r

The ratio S/V is inversely proportional
to the size of the sphererDistance tocenter (r)

1.0

2.0

4.0

Surf. area (S)

12.6

50.3

201.1

Volume (V)

4.2

33.5

268.1

S/V

3.0

1.5

0.75

✶ Multicellularity• Evidence from the geological record

2.1 Gyr fossil of a macroscopicorganism from Gabon whose affinity
is uncertain. It may be a multicellular
eukaryote or a bacterial colony.

Scale bars = 5 mm(from El Albani et al., 2010)

1.56 Gyr fossils of a macroscopic
multicellular eukaryotes from the
Gaoyuzhuang Formation in China.
Scale bars on left panel: 5 cm (ina,b,g), 20mm (in c), 40mm (in d) and5mm(in e,f). Scale bars on rightpanel: 100 mm (in d), 20 mm (in e).

(from Zhu et al., 2016)

(A) 1.2 Gyr multicellular red algae Bangiomorpha pubescens from arctic Canada(Butterfield, 2000), (B) 1.6 Gyr problematic Grypania spiralis from India (Butterfield,
2009)✶ Ediacara biota (575-542 million years ago)■■■■

Earliest diverse populations of large, complex multicellular animals
Mostly sessile (fixed), soft-bodied organisms
Bilateral or radial symmetry
High diversity
Short-lived episode in the history of life!

Locally, up to 3000 or 4000
individuals per m2!
Highly productive ecosystem!!!

From Narbonne (2005)

Ediacara biota “reported from nearly 30 localities on 5 continents” (Narbonne, 2005)

End of Proterozoic glaciations
Snowball Earth?

Snowball Earth?

From Narbonne (2005)

2 cm

2 cm

0.25 cm

5 cm

2 cm

2 cm

2 cm

2 cm

2 cm

Probable tracks left by an organism (indicates that motile forms possibly existed at that time)
From Narbonne (2005)✶ The Cambrian Radiation of Life (540 million years ago)

Pc

CambrianOrdov.

S Dev.

Carb.

Perm. Tr. Jurassic

Cret.

Tert.

Age (Ma)

Paleozoic Era

Mesozoic Era Ceno.

■
■
■

■

■

Major biological diversification
All known phyla present in the Early Cambrian
For some early Cambrian fossils, the link with extant taxa
is difficult to establish
Roots of diversification in the Precambrian (Cnidaria,
Porifera)
Major innovation: shell, carapace
Opabinia (arthropod)
Vauxia (sponge)
Louisella (priapulid worm)
Anomalocaris (arthropod?)

Gould (1994, Scientific American 271 (4))

Permian

Carboniferous

Devonian
SilurianOrdovician

Cambrian

Precambrian

Porifera(sponges)

Cnideria (modern anemones, jellyfish, corals)

Roots of diversification in the Precambrian

Briggs and Fortey (2005)

Hallucigenia

Possible triggering factors
1. Environmental factors• End of Proterozoic glaciations• Rise of O2• Change in ocean chemistry promoting biomineralization
2. Genetic factors• Emergence of key developmental genes (without which certain adaptations
would not be possible)

3. Ecological factors• Adaptations related to predation-prey relationship (shell, carapace,pelagism, body parts improving mobility, sensory organs…)! Coevolution – groups of organisms can affect each other’s evolution- As a prey, you tend to evolve traits to escape predators- As a predator, you tend to evolve traits to catch preyse.g. Think about a mollusk, like a slug. It may evolve a shell to protect itself.
Predators may in turn evolve specialized tools to break or drill that shell (e.g.
crab’s claws, carnivorous snail’s radula).

Simoes et al. (2006)✶ End-Permian mass extinction

250 Myr ago

Pc

CambrianOrdov.

S Dev.

Carb.

Perm.

Age (Ma)

Tr.

Jurassic

Cret.

Tert.

% of taxa
extinct

End-Ordovician

End-Devonian

End-Permian

Families

20-26

21-22

50-57

22-23

15-16

Genera

50-60

47-57

70-83

40-53

40-50

Species

85

70-80

85-96

76

76

End-Triassic End-Cretaceous

Lethiers (1998)

Sketch of the sea bed insouthern China before (a)and after (b) the enPermian mass extinction. A
marine fauna of 100 or
more species is reduced to
4 or 5. From Benton andTwitchett (2003).

●

Most severe mass extinction●~90% of all species went extinct!

●

Marine and continental life affected

Family Therapsidae(includes ancestors ofmammals)

Gorgonopsians

Arthropod

Trilobites

Wignall (2001)✶ End-Permian mass extinction• Possible causes

Supercontinent Pangaea

Less shallow marine environment increased competition for resources

NB: Meteorite impact
Evidence for end-Permian impact has been published by several authors but
the effect of the impact on the environment (and the existence of the impact
itself) is controversial.
Cocks and Torsvisk(2006)

Catastrophic Volcanic eruption

2,000,000 km3 Siberian flood basalts formed
within 1 Myr ~250 Myr ago (= world’s largest
continental flood basalt province!)
Wignall (2001)✶ End-Permian mass extinction• Effects on environment

Catastrophic volcanic eruptions in Siberia released massive amounts of CO2
and SO2 in the atmosphere (+ some Cl and F).

●

Short-lived global cooling due to the presence of dust and sulfate aerosols in theatmosphere (SO2 + water → sulfate aerosols)●

Acid rains (H2SO4, HCl, HF)●

Long-term global warming caused by greenhouse gas CO2

Examples of extreme consequences of global warming:• Ocean anoxia
Global warming lowers O2 solubility and slows down the thermohaline
circulation.
• Catastrophic release of Methane in the atmosphere
Large amounts of CH4 present in deep-sea sediments and high-latitude
permafrost as CH4 hydrate (stable at high P and low T).
Methane hydrate

Increased T may induce
melting of CH4 hydrate.
The release of CH4 in theatmosphere may further
enhance global warming,
creating a positive
feedback loop!
Tokyo Gas

Credit: R. Simmon/R. Rohde/NASA

U.S. Department of StateNASA

The Daily Yomiuri
NASA“Work toward prospective drilling for methane hydrate began at sea about 70
kilometers off Atsumi Peninsula, Aichi Prefecture, on Tuesday morning…
…The operation marks the first-ever attempt to drill into the ocean floor for theenergy source.”
The Daily Yomiuri (February 15, 2012)

BIOGENIC METHANE
Organic matter settles at the bottom of the ocean and is decomposedby microorganisms through fermentation. Methanogen Archaea use
the byproducts of fermentation (acetate, H2, and CO2) to obtain energy.
Two main pathways:
Acetate fermentation:
CH3OOH→ CH4 + CO2 + NRG

Anaerobic respiration using H2 as e- donor and CO2 as e- acceptor:
4H2 + CO2→ CH4 + 2H2O + NRG

THERMOGENIC METHANE
Product of metamorphism of org. C-rich deposits.

✶ End-Cretaceous mass extinction

65 Myr ago

Pc

CambrianOrdov.

S Dev.

Carb.

Perm. Tr. Jurassic

Age (Ma)

Cret.

Tert.

% of taxa
extinct

End-Ordovician

End-Devonian

End-Permian

Families

20-26

21-22

50-57

22-23

15-16

Genera

50-60

47-57

70-83

40-53

40-50

Species

85

70-80

85-96

76

76

End-Triassic End-Cretaceous

Lethiers (1998)

Dinosaurs

Ammonites

●
●
●

●

~75% of all species went extinct
Marine and continental life affected
Very abrupt extinction

The end-Cretaceous(K-T or K-Pg
boundary)
associated with athin, distinctive
sedimentary layerthat can be traced
worldwide.

By Kirk Johnson (Denver Museum of Nature and Science)BirdsSereno (1999)

Monotremata
Mammals laying eggs
Mammalian(e.g. Platypus)
OrdersPlacentalia

Evolution of Mesozoic and major extant mammal groups
Luo (2007)

Marsupialia

Without the extinction ofdinosaurs 65 Myr ago, theevolution of mammals would
probably have been a very
different story. “The Age ofMammals” is the namesometimes given to the
Cenozoic Era.

✶ End-Cretaceous mass extinction • Large meteorite impact●

A 10km-large meteorite impacted theEarth 65 Myr ago.

●

Main Evidence
An iridium peak at the K-T boundaryaround the world. Iridium abundanceis very low in the Earth’s crust andmantle, and comparatively very highin chondritic meteorites.

●

30 cm

Other lines of evidence
shocked quartz, tektites, nanodiamonds…

Alvarez et al. (1980)

Iridium abundance (ppb)●End-Cretaceous
paleogeography

Candidate crater for the K/T impact:
Chicxulub crater, Yucatan peninsula, Mexico

http://www2.nau.edu/rcb7/globehighres.html

Relief-shaded gravity anomaly data

Sharpton et al. (1993)✶ End-Cretaceous mass extinction • Consequences●

Nitric and sulfuric acid rains (months or years; global)■
Atmosphere is shock-heated and nitric oxide is produced
The site of the Chicxulub is rich in anhydrite (CaSO4)*. Hence, sulfur■
rich vapor was injected in the atmosphere due to the impact.

●

Short-lived global cooling (months or years; global)■
Sunlight is masked by dust and sulfate aerosols*: impact on
photosynthesis (collapse of primary producers) and surface
temperatures●

Long-term global warming (decades; global)
CO2, CH4, and water released by the impact and CO2 produced by■
wildfires might have caused global warming after dust and aerosols
had settled.

●Wildfires (extent debated)■
Affecting an area maybe aslarge as the American
continent●

Ozone destruction (years, global)
O3 destroyed by heat and Cl■
and Br from the vaporized
projectile.

●

Local and regional effects:■
Powerful earthquake (>11)■
Gigantic tsunami (1-km high)■Heat pulse (10,000 oC at impact
site)

?

Toon et al. (1997)

Nature, vol. 471, 51-57 (2011)