Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

GEO1211: Earth System Sciece: History of Our Planet > Deep time: Lectures 9-13 > Flashcards

Deep time: Lectures 9-13 Flashcards

1
Q

What era is the rise of plants associated with? (The other eras within the associated eon that are not related are the Mesozoic and Cenozoic)

A

Within the Phanerozoic eon, the PALEOZOIC era. This consists of Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian periods (542-250 Ma)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What was the planet like before plants?

A
  1. Atmosphere - less O2, CO2 around 15x present atmosphere level, 7 degrees warmer
  2. Oceans more anoxic
  3. Land uninhabited except for few anthropods (sandstone tracks 550 Ma), most life in water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the name of the tree used to plot out plant evolution?

A

Phylogenetic Tree

  • 1st photosynthesizing cyanobacteria engulfed by eukaryotes (2 Ga) creating first eukaryotic algae
  • Formed 1st multi-cellular sea-weeds and algae (water-bound)
  • 1st land-plants non-vascular bryophytes (e.g. liverwort, moss)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What were the earliest land plants? In what period?

A

Bryophytes: non-vascular plants in the Ordivician period, ~470 Ma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What evidence is there for the first land plants?

A

Cryptospores:
- Sudden change to new kind of these spores

Trilete spores

  • Dated at 445 Ma, ‘Y’ marking
  • Hardy spores, groups of 4 connected spores = resistance to dessication (extreme dryness)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What types of plants followed non-vascular plants? In what period? What evidence?

A

Mid-Silurian = vascular plants (425 Ma)

  • Fossils from 425 Ma
  • Structure implies tubing; maintenance of internal water pressure (homiohydric); remaining upright
  • No leaves or roots

Late-Silurian = leaves and roots

  • Fossils 420 Ma, larger 30cm plants
  • V small leaves (microphylls), roots
  • Like modern-day clubmosses
  • Evidence of giant fungi (prototaxites) 420-370 Ma (multiple C isotopes, multiple food sources)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What plants followed vascular plants? In what period and using what evidence?

A

Early-Devonian = Rynier Chert

  • Exceedingly well-preserved ecosystem 410 Ma (Aberdeen)
  • Complex; plant-fungi symbiosis, rock weathering, nutrient recycling

Mid-Devonian = first trees

  • ~385 Ma, up to 8m high (Wattieza stump, Gilboa, 1870s)
  • Lacked proper leaves

Late-Devonian - first forests

  • Archaeopteris ~375 Ma
  • Proper leaves, large 1.5m diameter trunks, 10m high
  • Source of organic carbon; enhanced weathering greatly
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What were the consequences of plant evolution?

A

Amplification of weathering/factors

  • Bcos they accelerate rate at which nutrients released (P has no gaseous form; rock breaking function)
  • By a factor of 10 (even earliest non-vascular mosses 2-9)

Global

  • Phosphorus leak to oceans; increasing ocean productivity –> organic C burial –> O2 increase
  • Less CO2 = cooling

CO2 & climate

  • Models; CO2 nearly constant at 16x PAL without plants
  • Plants HALVE CO2 to 8x PAL (allowing glaciation threshold to be met)
  • Earlier glaciations not explained by CO2 model predictions (too high)

Glaciations:

  • 300 Ma (Permo-Carboniferous) = by first forests
  • 450 Ma (Ordivician) = by first plants
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What were the constraints on oxygen?

A

Combustion sensitivity - less energy for ignition when O high. If lower than 15%, fires cannot start!

Lower limit = 15-17% (charcoal record 400 Ma)
Upper limit = 25-30% (abundant forests 350 Ma, fires can’t have been too frequent otherwise trees wouldn’t survive)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

By what mechanism/process did O increase and become regulated in the ocean? What does this point to?

A

Ocean-based regulator:

  • BEFORE PLANTS; system would counter a O drop
  • Anoxic waters promote P recycling –> increased productivity (cyanobacteria) –> CO2 burial
  • For every P, 250 C buried!

Plants double source of O to atmosphere = above 17% –> more fires

Points towards land-based regulator:

  • Veg limited by fires so O decreases
  • Photo-respiration may occur if O too high (Rubisco favouring O instead of CO2)
  • C-P ratios; fires redistribute P when biomass burned, washed into oceans BUT ocean material results in less burial than land = less burial = less O2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe oxygen level research on the Carboniferous-Permian (360-250 Ma)

A

Swamp environments (sinking continents) = coal deposits (dead matter, organic C)

  • 30-35% O peak predicted
  • V high O levels = giant insects (Meganeura dragonfly)
  • 10x size today, but 20-20% O too small
  • Other explanation: no larger competitors, filling ecological niche later occupied by flying reptiles/birds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe oxygen level research on the Mesozoic (250-65 Ma)

A
  • Dinosaurs so large because of high O levels?
  • Some predict low O at 12%
  • Recent studies = abundant charcoal throughout Mesozoic (espec. Jurassic period) - models wrong!
  • O couldn’t drop below 15%
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What role did O play in animal evolution? Did it enable intelligent life?

A

Rising O triggered evolution of placental mammals?
BUT abundant charcoal suggests O actually higher than present, declined during Cenezoic

Brain function suffers at around 15% Oxygen (one settlement 11%)
- Charcoal record = many fires = O not below 17% so…
NO, INTELLIGENT LIFE NOT HELD BACK BY LACK OF O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Name the 5 key extinctions. What are the two main ones?

A
  1. End Ordovician
  2. Late Devonian
  3. End Permian = BIGGY
  4. End Triassic
  5. End Cretaceous = SECOND BIGGY
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe the End Permian extinction - evidence and aftermath.

A

250 Ma

  • 61% families extinct
  • Evidnece: plant mutagnesis (mutated plants, exposure to UV from ozone depletion)
  • Loss of forests for 5Myr in records
  • Lystrosaurus shovel lizard survived!!

Aftermath:

  • Oscilation of C cycle and ocean anoxia for 5 Myrs
  • ~10 Myr recovery of ecosystems
  • ~100 Myr recovery of global biodiveristy
  • Shift in marine ecological state: increased mobile animals and predators
  • Mammals and flowering gymnosperms replaced reptiles and non-flowering
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the proposed causes of the P-Tr extinction?

A

Impact? - REJECTED

  • Shocked quartz, buried crater, fullerenes (extraterrestrial isotopes)
  • Not reproducable, lack of iridium

Volvanic? -CLEAR

  • Siberian Traps LIP - 2 Mkm3 of lava = 1.6 M km2 covered, 3000m deep
  • V short timescale, 60kyrs
  • Release of CO2, melting of org. matter in crust = CH4 and CO2 (13-C depleted material)
  • Temp rise of 10 degrees

Ocean acidification?

  • More C dissolved, carbonic acid, H dissolves
  • CaCO3 shells inhibited; shells lacking from record

Anoxia?

  • Lack of larger fossils suggests lack of O
  • Euxinic waters = rise of hydrogen sulphide
  • Why? Fast basalt weathering = more P = increased O demand
  • Temp rise reduces oxygen solubility = less O dissolved in ocean
17
Q

Describe the K-P extinction - evidence and aftermath.

A

60% genera extinct, rapid
Unusual selectivity e.g. large dinos extinct, not smaller burrowing ones
- Evergreen suffered more than higher-lat deciduous veg

Aftermath:

  • Origination rates rapidly increase; empty ecological niches filled
  • Diversity of mammals rose; espec. size since dinos gone

LAND DIVERSITY (mammals) OVERTAKES MARINE FOR 1ST TIME IN PHANEROZOIC

18
Q

What are potential causes of the K-P extinction?

A

Impact event (CONVINCING)

  • Ir-rich sediment
  • 180km wide crater dated 65 Ma, Mexico

Volcanic (LIKELY)

  • Deccan Trap LIP; 800 kyr basalt outpouring; 365k km3
  • Increased planet vulnerability (warming)

Strangeglove ocean

  • Species loss of 90% for marine phytoplankton
  • Acidification? Impact/eruption aerosols blocked out Sun, prohibiting photosynthesis…

Bio pump collapse

  • C transfer to ocean stops; suggested by dorp in C isotopic ratio
  • 40-60% drop in CaO within ocean sediments
  • 2-3x increase in atmospheric CO2, combined with eruptoins = dramatic CO2 rise and warming
19
Q

Describe the Cenozoic Era and what is the PETM?

A

Divided into 2 periods = Tertiary and Quaternary

Tertiary split into Paleocene (65-55 Ma) and Eocene (55-34 Ma)

Spike in temp between these two eras = Paleo-Eocene Thermal Maximum (PETM) = +5 degrees warming within 20 kyrs

20
Q

How has the PEMT been reconstructed?

A

C and O isotopes…
- Suddent warmth in Cenozoic record identified through 13-C enriched oceans and 13-C depleted land biomass = large injection of C (and much burial)
- Later cooling trend linked to declining CO2
- Fossils (foraminifera) CaCO3 shells = 16-O in shells indicates warming temps
(at warmer temps, oceans have more 16-O bcos of melted ice and high energy evaporation of 18-O. In colder periods, 16-O is preferentially evaporated and later precipitated to form ice, so oceans are 18-O enriched)

21
Q

What has the PEMT been linked to?

A

Diversification of mammals:

  • Mammals 150g-1kg at end of Mesozoic
  • Not bcos of O rise (charcoal) = Ecological explanation = first orders
    1. Even-toed ungulates (e.g. pigs)
    2. Odd-toed ungulates (e.g. horses)
    3. Primates (e.g. lemurs, apes…us)
22
Q

What evidence is there for the PEMT?

A

Ocean acidification:

  • Mass CO2 injection = carbonic acid
  • Less CaCO3 shells (dissolved in acid)
  • Would require ~2000 GtC (100k yr recovery)

C cycle perturbation:

  • 2 negative shifts in 13-C 1k yrs long, 20k yrs apart
  • Suggests large release of 13-C depleted C from org matter or CH4

Source of much 12-C?

23
Q

How has the PEMT been explained - the driving mechanism?

A

Volcanic trigger:

  • Released CO2 and thermogenic methane (org C from crust cooked into gasses, out gassed)
  • Possible bcos of opening N Atlantic 56.1 Ma
  • 5-10 M km3 basalts deposited

Methane hydrates:

  • Trapped CH4 gas in frozen water lattice
  • Form under high pressure and cold temps
  • PETM = warming of surface ocean = destabilisation og methane hydrates = outgassing of methane –> positive feedback
  • Sediment avalanches decreasing pressures = more CH4 escape

= 1,500-4,500 GtC of CH4 released!

24
Q

Describe the PEMT recovery. What can be learnt from this?

A

Potential for methane hydrates to be distabilised in the present (1000-10,000 GtC)

Humanity burning so much C, could reach similar levels of PETM so need to be careful

Especaially bcos of ~100,000 recovery from ~1000 GtC

25
Q

When was the first Antarctic glaciation? What does this mark?

A

33 Ma - boundary between Eocene into the Oligocene (within Tertiaty period)
Thawing of it marks Oligocene-Miocene boundary (24 Ma)

26
Q

What formed the Himalayas and Tibetan Plateau? What are the implications of the Himalayan Uplift? What are the problems with the hypothesis?

A

India into Asia collision (~20 Ma in Miocene)

Increased weathering, decreased atmospheric CO2, cooling -neg feedback (reduced Si weathering –> steady state of CO2 balance)

Org. C burial - increased, removal of CO2, cooling, Si weathering suppression

Problems: poor preservation in records
In fact, global erosion roughly constant psat 10 Myrs (cooler, drier climate = less rain = less erosion?)
CO2 stable

27
Q

How has the Cenozoic climate been reconstructed? What has it shown?

A

Stable CO2 for last 24 Myrs

  • Linked to temp
  • Peak warmth 50 Ma in early Eocene
  • Cooling and CO2 decline
  • Issues with CO2 record though e.g. 34 Ma Antarctic ice sheet (E-O boundary) not followed

Fossil stomata - CO2 declines = more holes

Phytoplankton - C isotopes

Ancient soils - C isotopes

Foraminifera - O isotopes

28
Q

Describe Miocene CO2 levels. Why so stable?

A

23-5.3 Ma

Stability - burial, CO2 starvation, slowed weathering

29
Q

Describe the rise of grasslands.

A

3 phases:

  1. Eocene/Oligocene 33 Ma – desert grasslands; cooling planet = less moisture = drier conditions
  2. Early Miocene 17 Ma – ungulates (horse, antelopes) = diversification enabled by co-evolution
  3. Late Miocene 7 Ma – C4 grasses; most plants are C3 but evolution of more hardy grasses that concentrated CO2 in themselves (C4) = greater distribution
30
Q

What can be said of evolution within the Pliocene?

A
  1. 3-2.58 Ma
    - 1st widespread savannah biomes in tropics
    - Pivotal role in ancestry; 4-limbed, tree dependent creatures forced to evolve upright
    - Last 5 Myrs of climate = decreasing trend in temp, with shorter and longer ice-age cycles - got progressively longer

GEO1211: Earth System Sciece: History of Our Planet (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions