Extinctions 1

Question 1

What is extinction?

Answer 1

An expected process that is natural and shows change through time.
Extinction rate should match rate of new biodiversity. Balance of biodiversity.

Question 2

What causes change from Paleozoic to Mezosoic?

Answer 2

Incoming of distinct new species usually defines a new period, but the change between Permian to Jurrasic is so huge they made a whole new era (mesozoic)
They (without realizing it) were identifying mass extinction and evolution.

Question 3

What effect would plate tectonics have on biodiversity over time?

Answer 3

Biodiversity is number of species NOT individuals on the planet.
Plate tectonics: the more fragmented, the higher the biodiversity on the planet! Due to climatic variation, variable food supply, barriers to migration and changes in oceanic circulation.

Question 4

How would global biodiversity change through time

Answer 4

1. Supercontienent Rodina (750Ma) fragments. First high diveristy biota after the snowball.
2. Fragmentation continues through lower paleozoic and biodiversity increases.
3. Upper paleozoic fragmentation goes in reverse. ie. formation of old red sandstone in late devonian (diversity drops with series of extinction pulses)
4. Formation of Pangea (end of permian) massive drop in global biodiversity
5. Fragmentation of pangea during mesozoic and diversity increases again (with a few hiccups)
6. Today continents are rich and randomly dispersed.

Question 5

What are sudden changes referred to as?

Answer 5

Mass extinction events.

Other extinction events/changes are ‘first order’ which dont account for the large rapid drops.

Question 6

What classifies a mass extinction event?

Answer 6

30% of all species extinct. Broad range of ecologies
Short sudden. Gradualists say 0.5-1million years, catastrophists say between 1-100 years.
Can be classified by severity
Major (50% families, 96% species)
Intermeidate (30 families, 50 spcies)
Minor (10 families, 30 species)

Question 7

What are the last five major mass extinctions recognized in the last 500MA

Answer 7

Late ordovician
Late Devonian
Late Permian
Lake Triassic
Cretaceous/Paleogene

possibly entering the 6th

Question 8

What are the causes of mass extinctions?

Answer 8

1. biologial/competition/predation/pathogens being introduced. creatures occupying the same niche. i.e. newzealand ground dwelling bird fauna.
2. Earth based, related to place movement (climate/ocean cirucation and volcanic activity)
3. Comets and extra-terrestrial impacts
4. Combo of many factors is most reliable cause.

Question 9

What are the fragments of odovician continents?

Answer 9

Gondwanaland (africa and south america)
Laurentia (north america)
Avalonia (southern britain, atlantic canada, coastal USA)
Baltica (NW eurasia)

Gondwanaland is moving towards south pole and ice begins to grow on it where north african sahara desert is.

Question 10

What was the ordovician like?

Answer 10

Tropical paradise with high biodiversity. Greenhouse planet.
Ancient ecosystmes were not primitive.

extinction starts in last stage of ordovician, the Hirnantian. where 85% of all species perished. starts 445ma

Question 11

What are oxygen isotopes and how are they used?

Answer 11

O16-18. Used to read glacial periods.
o16 is the lightest, it is what is evaporated from oceans to create rain. When it is cold, instead of going back to oceans the rain stays on land in the form of ice. This increases relative 018 in the oceans! Recorded in brachiopods (shell structures)
oxygen is not radioactive, just a stable isotope that can be counted relatively.

have you looked at examinable required reading on website???

Question 12

What is the 1st pulse of the ordovician extinction? hirnantian glaciation

Answer 12

445 Ma, tropical fauna’s hit hard first, 50/70 tabulate nd rugose corals are extinct. Golder water creatures migrate northwards and tropical creatures had nowhere to go! Glaciation caused a rapid drop in sea level too (seen as erosion surface in ordivician sediements)
Deep canyons in river systems. water on land tries to come to equilibrium with level of the sea!
Water is withdrawn from the shelf, so its colder and loss of habitat.

Question 13

What is the 2nd pulse of ordovician extinction?

hirnantian glaciation

Answer 13

End of glacial period. Sea levels and temperatures RISE.

Not as severe as the 1st, but those who had adapted to the cold now die off.

Question 14

Why didn’t Gondwanaland get ice earlier if it sat on the south pole for longer?

Answer 14

Closure of Iapetus Ocean - The Caledonides Mountain building Period.
- Development of Appalachian and Caledonian mountain belts when Avalonia and Baltica collide (later collide with Launentia).

The ocean was removed by subduction, same process for andes mountains (edge of continental margin)

Ocean closes through silurian and finally closes in Devonian forming Laurussia (euramerica) . Ocean suture line runs through northern england and ireland.

The EROSION OF THE RISING MOUNTAIN CHAIN would drawdown co2 to cause silicate weathering, and a possible drop in volcanic activity.

net drawdown of co2 cause rapid glaciation

Question 15

What is the Niarbyl Fault Ilse of Man?

Answer 15

Suture line between laurenia and avalonia. Visible representation of closing iapetus ocean. Has been heavily eroded.
Same thing happened in north america explaining paleozoic fossils.

Question 16

What is the mystery of fossils?

Answer 16

triobites on either side of the suture line were different, indicated welding of the ocean together. Avalonian assemblange and laurentian fauna)

Question 17

What was a problem with the hirnantian glaciation?

Answer 17

it was very short compared to others, but it was the most severe.
So either it should have been longer or today we should be having greater extincitions.

Question 18

Who was Brian Thomas and what was his theor

Answer 18

Gamma Ray bursts hypothesis (GRB)
First detected in 1967

Found gamma rays coming from the sky not earth’s surface (checking for nuclear weapons)

Fairly common, lasting microseconds to minutes.
Intergalactic origin- found all over the sky not just in ‘milky way’ edge.

Question 19

What causes GRB?

Answer 19

Death of hypergiant star.
Around 300 solar masses, short life of 3 million years.
when they die, 100x energy of a supernova.
Create black holes, and 2 jets of plasma.
This happens every billion years within range of earth.

Question 20

How does a GRB effect earth?

Answer 20

Ozone layers deplete.
Penetrate more UV to the surface, maybe account for extinction of trilobites (Bruce LIeberman)
Kills of young planktonic embryos, and kills of microplankton which are the base of the food chain.

Cause formation of nitrogen oxides (smog) causing global dimming, possibly initiating the hirnantian glaciation. Nitrogen gases could be dissolved in rainwater producing an acid rain.

Question 21

What is the evidence for GRBs and hirnatian glaciation?

Answer 21

none at all!

what really happened probably was that the organisms were adapted to facing any change in environment so there were more casualties than usual.

Question 22

Who were Raup and Sepkoski? what did they think?

Answer 22

They used statistics to determine there are extinctions (minor or mass) every 26M years. There is a downturn in biodiversity every 26m years. Nothing on earth has a 26m/y period, so looked upwards.
Thought there were impacts every 26 m/y from the Oort cloud.

Question 23

What are the possibilites of getting comets from the oort cloud every 26m/years?

Answer 23

1) gravitation kicks from
- nemesis (companion star, rotates around each other), small red dwarf star
-maybe a black hole?
2) Planet x: there is another planet, maybe a gas giant that’s orbit every 26m/years causes flood of comets into our solar system
3) movement through the galactic plane.
- since the galaxy is concentrated in a flat way, most of the ‘stuff’ is in the center. when our solar system rotates around the center of the galaxy, it oscillates up and down through this concentrated part. EVERY 26M/YEARS.
so we think that every time it gets to the middle, the ‘stuff’ is pulled into our solar system.

Question 24

Are we in danger from comets from the oort cloud??

Answer 24

We were in danger zone 1 m years ago, but rocks take 1 myears to get here, there was a comet that hit jupiter (shoemaker levy 9 in 1994) which would have decimated earth if it hadn’t hit jupiter.
but the data isn’t super reliable, because its statistics.