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ID1006 > Red Earth, Green Earth > Flashcards

Red Earth, Green Earth Flashcards

1
Q

How does life affect the environment?

A

Creates an entropy/free energy gradient which causes a thermodynamic desiquilibrium

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2
Q

How does Lovelock propose thermodynamic desiquilibrium could be a bioindicator?

A

Earth’s atmosphere is a lot further from equilibrium that non-living planets

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3
Q

What are the main eons?

A

Hadean, Archean, Proterozoic, Phanoic

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4
Q

What was the earth’s atmospheric composition before life?

A
  • Mostly composed of volcanic gases (H2, H2O, CO2, N2, SO2, H2S)
  • 0.8 bar of moderatley inert N2
  • Higher CO2 and H2 (interior is more radioactive)
  • Extremely trace levels of O2
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5
Q

How do methanogens metabolise and how might this solve the ‘faint young sun’ problem?

A

4H2 + CO2 –> CH4 + 2H2O

Produced methane which is a more powerful greenhouse gas than CO2

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6
Q

How did anoxygenic photosynthesis also contribute to methane production?

A

2H2 + CO2 + hv –> CH2O + H2O

fermentation: 2CH2O –> CH4 + CO2

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7
Q

How would Earths surface have looked during high methane atmosphere concentrations?

A

Hazy

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8
Q

How does the water splitting centre work?

A

Uses 4 Mn and 1 Ca atom as well as the energy from 4 photons to release 4 e- from H2O

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9
Q

When is oxygenic photosynthesis believed to have evolved?

A

2.7 Ga, no convincing evidence past 3 Ga

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10
Q

Name 3 points of evidence for an environment lacking in oxygen

A
  1. Rounded sidenite/uranite/pyrite suggest long term transport, would usually have been dissolved in oxygenated water
  2. Dissolved O2 would have converted Fe2+ to Fe+3. Ancient soils have little Fe and modern soils have a lot of Fe3+
  3. Banded iron formations 3-1.8 Ga require Fe2+ in the oceans + a local oxidant
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11
Q

What is the “smoking gun” for the great oxidation event?

A

Farquhar (2000)

  • A isotope 33S only forms in an oxygen free atmosphere and was discovered to be ubiquitous in sulfur bearing sediments
  • No 33S after 2.3 Ga
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12
Q

How are eukaryotes different to prokaryotes?

A
  • Larger, more complicated cells (have a nucleus containing DNA)
  • Require O2
  • Much more information can be passed to the next generation of eukaryotes
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13
Q

What are achritarchs and when did they begin to appear?

A
  • Small non acid-soluble organism that cannot otherwise be accounted for
  • Usually spherical with some surface markings
  • 2 Ga
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14
Q

What are tappania and bengiamorpha pubescens believed to be?

A
  • Tappania (1.5 Ga) has an cytoskeleton, believed to be a fungus
  • Bengiamorpha pubescens (1 Ga) is a sexually reproducing multicellular algae
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15
Q

When are the 3 snowball earth and glaciation events?

What evidence is there for this?

A

700 Ma, 640 Ma, 580 Ma

  • Glacial tills indicate ice flow
  • Dropstones dropped in ocean sediment possibly transported by ice
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16
Q

What are glaciation events associated with?

A

A second increase in atmospheric oxygen to 21%

17
Q

What were the causes and consequences of the neoproterozoic revolution?

A
  • Rise in oxygen, glaciation events, tectonics and colonisation of the land by rock weathering organisms
  • Resulted in animals!
18
Q

Why is diversity believed to have increased hugely during the Cambrian explosion?

A
  • High levels of oxygen?
  • Origin of eyes allowed for predator prey relationships and the beginning of the modern food web
  • Origin of shells, so possibly a conservation bias
19
Q

What is GOBE?

A

Great Ordovician Biodiversification Event

Advent and diversification of marine invertebrates

20
Q

How is tectonic forcing possibly linked to an increase in biodiversity?

A
  • During Ordovician greatest continental dispersal of the Paleozoic
  • Differences in latitude and changes in currents
  • Cause massive geographical differentiation of faunas
21
Q

When do the following begin to appear?

  1. Fish
  2. Insects
  3. Amphibians
  4. Reptiles (amneotic eggs)
  5. Plants and gynosperms
A

1 + 2. Denovian

  1. Mid paleozoic
  2. Mid-late paleozoic
  3. Late ordovician, late paleozoic
22
Q

What are the 5 big mass extinction events?

A
  1. Late Ordovician
  2. Late Denovian
  3. Late Permian (Great Dying)
  4. Late Triassic
  5. Late Creataceous (KT)
23
Q

Which mass extinction event was the most severe?

A

Late Permian, 95% of species disappear

24
Q

What are the 3 proposed causes of the Late Permian extinction event?

A
  1. Widespread volcanism
  2. Oxygen depletion
  3. Sulfide build-up
25
Q

Name 3 biological events of the Mesozoic era?

A
  1. Dinosaurs became dominant
  2. Both mammals diversify and birds evolve
  3. Advent and diversification of angiosperms in the cretaceous
26
Q

What were the 4 inital hypothesese for the KT (Cretaceous-Tertiary) extinction event?

A
  1. Volcanism
  2. Disease
  3. Ozone destruction for nearby supernovae
  4. Climate change
27
Q

What evidence is there for the KT extinction being caused by a comet impact?

A
  1. Iridium rains down at a constant rate as “cosmic dust” however at time of KT extinction levels 100* the normal
  2. Evidence for impact and massive wildfires seen worldwide in the few centimetres of stratigraphy that represent this time

ID1006 (12 decks)

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