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Dinosaurs > Lecture 20: Extinction > Flashcards

Lecture 20: Extinction Flashcards

1
Q

Whats the definition of extinction

A

The birth rate of an organism does not keep up with the death rate

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2
Q

What is a Background extinction?

A

Less dramatic than mass extinctions, slower and longer. 95% of all extinctions are accounted for by BG extinctions

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3
Q

What are the causes for a background extinction?

A

Depletion of resources in habitat, Competition for food and space, changes in climate, development of mountain ranges, habitat destruction through fire, river migration, drying of wetland, eruption of Volcanoes

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4
Q

What is a mass extinction?

A

Large numbers of species and types of species go extinct. Effect MUST take place on a global scale, happens over a short period of geological time

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5
Q

Times Of mass extinctions

A 
Late ordovician (438ma)
Late Devonian (380 Ma)
Permian (245ma)
Late Triassic (208ma)
Cretaceous/tertiary (65ma)
Today?
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6
Q

Modern extinction crisis

A

We are losins species 1000 to 10000 times the background rate (aka dozens every day)
99% of species are at risk from human activity

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7
Q

Permian Extinction 250 Ma ago

A

Most severe mass extinction
96% of all species died & 52% of all families
over 2 mill years
Glaciation-sea level drop, reduced amount of shelf space
Large volcanic eruptions siberia/arctic

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8
Q

Triassic Extinction 200 ma ago

A

two phases, flood basalts of the Central Atlantic magmatic province
loss of 76% of marine and terrestial species
20% of families
Opening of ecological niches for the dinosaurs to thrive

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9
Q

Problems with extinctions

A

Incompleteness of fossil record, incompleteness or sedimentary record, resolution

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10
Q

Effect of sampling

A

Biostratigraphic ranges, last appearance datums and species dissapear at different levels in different areas

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11
Q

The K/T event: early studies focused on?

A

Dinosaurs- were they too big? too stupid? too undesexed to survive? too constipated? or too weird?

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12
Q

The early theories

A 
Suffered competition for food sources from mammals and insects
poisoned by plants
slaughtered by plagues
wiped out by shocked climatic change
By extraterrestial catastrophes
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13
Q

Problems with the early theories

A 
Other groups went extinct
some groups survived
Multitude of data: 
-environmental changes
geochemical changes
-land and sea
-decline and replacement of fossil groups
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14
Q

Groups with losses or total disappearance

A

Land animals: dinosaurs, pterosaurs, some birds, some families of marsupial mammals
In the sea: mososaurs, plesiosaurs, some ray finned dish, amonites and belemintes, rudist clams, certain mollusks, inoceramid bivalves
Plankton, over half of various groups

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15
Q

Survivors

A

Most land plants, insects, snails, frogs, salamanders, turtles, lizards, snakes, crocodiles, placental mammals, Marine invertebrae (starfish, sea urchin, mollusks, many fish)

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16
Q

Causes of exctinction

A

What was the earlth like at the end of the cretaceous? Intense tectonic acitivity, formation of Rocky mountains and andes, in europe Alps and volcanisms

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17
Q

Signs of Volcanism

A

Extensive sea floor spreading at pacific rim, development of volcanic arcs, huge basalt flows

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18
Q

Deccan traps in India

A

Flood basalts (volcanic rock)
60-65 mya
large amounts of volatile gas
-carbon dioxide, sulfur oxide and nitric oxide
-temperature change, damage of ozone layer-acid rain

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19
Q

What causes cooling?

A

Greenhouse is delayed
SO2 oxidizes in atmosphere to SO3
Sulphur trioxide is primary agent for acid rain
Micro droplets of sulphuric acid
Droplets are smaller than wavelength of light- Photons that meet a dropletmight be returned to space
ice formation- drop in sea level- hardgrounds and incised river valleys

20
Q

Continental configuration- similar to that of todays, except for

A

Exceptions:
-Land bridge connected North America and Asia
Africa was isolated
South america was connected to anartica/australia by most southern tip
-india in the middle of the indian ocean

21
Q

Oceans

A

High sea level throughout cretaceous, regression towards the end, new oceanic crusts cooled and subsided, epeiric seas dried out

22
Q

What was the climate

A

Warm during cretaceous, Greenhouse effect, CO2 to atmosphere due to tectonics, cooling and seasonality started during 2nd half of period, drop of 5 degrees

23
Q

Asteroid impact

A

Gubbio section in italy, 3 layers in marine sediment

24
Q

Iridium Layer

A

Element of the platinum group, rare in earth surface material, higher concentration in earth core and METEORITES (so evidence)
much higher concentration at Gubbio. Over 100 sites are discovered with iridium anomalies

25
Q

Shocked Quartz as an indicator for an impact

A

Quartz crystals where the crystal structure has been shattered, found in sediments marking the K/T boundary, caused my meteorites smashing into earth

26
Q

Microtektites (evidence)

A

Are small droplets of silica rich glass, material of meteorites, thrown up into atmosphere in a molten state, becoming solid after cooling and falling back to earth

27
Q

Search for the impact site

A

haiti: sequence of glass–> 1 M thick, rich in sulfur, resulting from molten continental crust and evaporites
Yucatan peninsula: in 1991 a bowl shaped structure was found, 180 km in diameter and drilling revealed shocked quartz, sequence formed between continental crust and evaporite deposits
Chixclub crater 65mil

28
Q

immediate regional effects

A

Blast wave, base surge, Tsunamis, vaporization of water, vaporization of rock, earthquake

29
Q

Short term global effects (days to weeks)

A

Global distribtution of ejecta and global wildfires

30
Q

Long term global effects (months to years)

A

Global darkness, acid rain, greenhouse effect

31
Q

What was the impact?

A

Tsunami, evidence at the gulf coast at the K/T boundary. Relased by impact? Short term global warming, release of large amounts of energy in form of heat (increase of 30 degrees for 30 days) Global wildfires (soot rich horizons found in Europe and New Z.) rich in carbon
Acid rain and nitric acid rain
rapid heating of atmosphere
long term global cooling
blockage of sunlight (lasting 3 months or longer)

32
Q

Long term global warming

A

Most of biomass gets exterminated, Biomass decease amount of CO2, no biomass= increase in Co2 in atmosphere= greenhouse effect

33
Q

Link to biological record

A

The clay layer is one true signal of a catastrophic impact

34
Q

Iridium clay layer reflects 3 months around the world

A

effects on biota have to be studied in
oceans
atmosphere
land

35
Q

Paleoenvironmental change

A

Animals thrived in epeiric seas, these dried up due to lower sea levels, lack of easily accessible fossil record on land sections

36
Q

Formanifera

A

Benthic, Planktic, large abundance and short biostratigraphic ranges

37
Q

Primary productivity

A

Measured by carbon Isotopes, measured on bnthic and planktic foraminifera. Primary productivity broke down at K/T boundary

38
Q

Importance of palynology

A

-palynoflora: spores and pollen

Megaflora; leaves etc.

39
Q

Terrestial record

A

In Montana, North dakota and Wyoming:
Pollen extinction at iridium
followed by abundant ferns
followed by new assemblage of flowering plants

40
Q

Terrestial record in Canada:

A

A series of 5 major pollen changes related to different latitudes, series of extinctions related to climate changes, not only at K/T boundary

41
Q

Vertebraes

A

Research from montana; 150,00 specimens were collected around boundary
Aquatic animals survival-90%
Land animals-10%

42
Q

Dinosaurs

A

Decline of dinosaurs took place over 7 Million years before boundary but acceleration in the final 0.3 million years, competition of mammals

43
Q

Problems with post extinction dino research

A

Study conducted on a family level, genera and species could have dropped out earlier. North america was one of the last localities for Dinosaurs

44
Q

arguments for asteroid impact

A

1) global impact? yes
2) independent of climatic zones? yes, bivalves become extinct
3) gradual decline or shock?
evidence of gradual decline of lineages in mammals argue against impact

45
Q

Marine life

A

Marine animals depending on primary productivity became extinct but marine animals surving on detritus (remains of dead organims) survived

  • scavengers
  • suspension feeders
  • often benthic
46
Q

Terrestial Life

A

Aquatic animals survived
lakes adn wetlands act as sinkholes for detritus
large role of primary productivity

47
Q

Why were mammals survivors?

A

Removal or dinosaurs triggered radiation of mammals, creation of ecological oppurtunities, mammal paleontologists argue against asteroid theory

Dinosaurs (15 decks)

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