Pg. 66EXTINCTIONS

Natural Disasters of epic proportions

5 mass extinctions on Earth - know geologic periods and ages of these events

Pg. 661)Ordovician about 458 million years agoa.) marine life on sea floor and near surface.

Reef builders hit hard, few reefs survive into Silurian time.

*Why ? glaciation at that time = cool temperatures

A good link explaining more

ADD Gondwana (large landmass) was near the south poleat that time. Plate tectonics????More or less glaciers?

????Sea level change results?

Reef builder and warm water species most profoundly effected WHY?

Pg. 662) DevonianAbout 375 million years ago A good link explaining causeFauna included similar to Ordovician and fishes.

a) marine life hit hard but land plants not affected

b)Reefs had a hey-day in the Devonian but were decimated again in LATE Devonian.

Reefs small for over 200 million years.

*Why? crisis not sudden - took millions of years and is attributed to global cooling.

Similar to Ordovician- Plate Tectonics

Pg. 663)Permian 260 million years ago

Good link with explanationa.) greatest mass extinction of life on earth.

75-90% of all marine species expired!

b) Terrestrial vertebrates hit hard!

c) Plants seem to be immune - this may be related to

reproductive strategies (only need a small part to survive – cuttings, seeds)

ADD A number of things probably contributed-timing1.) Slow event - occurring over millions of years

Pg. 663)Permian CONTINUED ADDA number of things probably contributed-timing2.) Pangaea formed and changed…

a.) the amount of warm shallow oceans-DECREASED

b.) large climate CONTRAST-interior of the continent was way hot/dry and opposite

near shore similar to Australia but even more so.c.) more competition

3.) Sea-Level falla.) spreading at mid-ocean ridge slowed-less

volume in the oceanb.) this caused the volume of ocean basins to

be decreased=shoreline moving seawardc.) how effect #2???

ND pg. 438 fig. 15.16

Pg. 663)Permian CONTINUED ADDA number of things probably contributed-timing 4.) Siberian Traps (warm the climate or did it?)

a.) massive amount of flood basaltsb.) possible COUP DE GRACE?c.) huge release of CO2 and other

Greenhouse gasses

Pg. 674) Triassic About 240 million years ago

a) Amphibians and mammal-like reptiles suffered

great losses.b) 20% of marine invertebrates families

(groups) gone.ADDCauses: all have problems explaining1.) gradual climatic/sea level change theory?-

then why abrupt extinction?2.) impact?-no impact crater found3.) Break up of Pangea-Central Atlantic

Magmatic Province (CAMP)-lots of volcanic emissions- Greenhouse effect-not cooling

*Cooling the culprit?Added new open niches for dinos to fill.

Pg. 67 5) Cretaceous BEEN HEREAbout 65 million years ago

a) All dinosaurs go extinct. Large reptiles living in ocean

gone too.

b) Extinctions affect marine life.Tropical hit the hardest

c) Heavy loss of low-latitude flora of N. America.

d) fern spike in N. A. = ferns are good invader species spread over barren surfaces

Pg. 67 5) Cretaceous CONTINUED BEEN HERE

*Why? - Impact? or Climate?

Impact evidence - crater, iridium, shocked quartz, tektites, tsunami deposits.

Climate evidence – some say extinctions may be gradual - not sudden. Significant volcanic eruptions at this time (Deccan Traps)- could change climate HOW???

ADDWhich is considered stronger argument? WHY?

Pg. 67-68EVIDENCE PATTERNS IN EXTINCTIONS USED TO DETERMINE CAUSEEVIDENCE1) Land and sea affected (sea often more so).

2) Tropical taxa (groups of critters) eliminated/trashed.

3) If taxa had extended range from tropics to higher lat. they become compressed

(tropical wiped out and others migrate)

4) Shallow ocean shelf affected more than deep ocean.

Pg. 67-68EVIDENCE PATTERNS IN EXTINCTIONS – USED TO DETERMINE CAUSE continuedEVIDENCE5) In groups like fish - freshwater and marine

marine suffer more extinctions. Marine adapted to narrower temp. tolerance.

6) Plants appear immune compared to animals.WHY?

7) Some groups experience repeated extinctions (invertebrates: trilobites, ammonites).

8) Some believe periodicity to extinctions - every 26 million years. (resolution problem).

Pg. 68 POSSIBLE CAUSE*All come down to climate change*

1) Global cooling - fits with: a) compression of species

b) tropical go first seem to be very sensitive totemp changes (reefs demise)

c) shelf water life goes vs. deep ocean WHY?

d) terrestrial life can adapt (more mobile) betterthan marine so possibly have higher probability of survival

Pg. 68 POSSIBLE CAUSE-continued*All come down to climate change* Cause of global cooling?1) Glacial Event - timing doesn’t always fit when it was cold still had critters around.

2) Plate tectonics - changes ocean circulation as cont. move = cooling

3) Carbon Dioxide shortage?Devonian - plants explode and use CO2.

Could this cause a cooling? WHY/HOW?

Opposite of global warming?

Pg. 68 POSSIBLE CAUSE-continued*All come down to climate change* Cause of global cooling?

4) Volcanic Eruptions - gas in atmosphere block light - also cause acid rain which could change ocean geochemistry maybe cause problems on land also

5) Impact = nuclear winter - break down food chains

Pg. 692) Global Warming?

a) modern example1982-83 El Nino entire species of clam dies - off coast of SA

Well - OK but that is local how about global?

Warming events don’t match with species compressionpattern

ANY COMMENTS???

Pg. 693) Habitat Loss - Changing sea levels affect marine creatures

doesn’t explain terrestrial (land critters).

Sea level changes due to plate tectonics(sea floor spreading>) and glacial events.

AGAIN ND pg. 438 Fig. 15-16

Impacts?? Could cause lots of global loss of habitat.

Pg. 694)Disease - consider dinosaur extinction. Sea

level lowered and provided land bridges. Problems?? Kind of like our airlines today. Allows transmission of diseases.

Some evidence…

a.) Fungal proliferation caused a suppressedimmune system

b.) CT reveal tumors in certain species ofdinosaurs (duckbills)

Avian Flu and humans?

Pg. 695)Predation? - possible cause for an interesting

extinction of large Pleistocene mammalsTwo ideas for the Pleistocene mammals example: 1.) Changing climate Problems? Too slow.

a.) many large animals went extinct and no plantsb.) mammals should not be so heavily impacted WHY?c.) glacial retreat should provide more habitatd.) there were no equivalent extinctions during earlier phases of ice age.

2.) human radiation (immigration)? Problems? a.) Calculations show not enough humans to cause the problem. EXPLANATION: Ok then what if they decreased another keystone species?

Pg. 69Predation? continuedADD3.) Another idea for Pleistocene mammal loss.Those little mammoths found on islands ....hmm…

Wrangel IslandGood explanation of the ideaMammoths migrated to island and then rising

sealevel isolated them. Through about 500 generations those that were smaller were more “successful”. WHY?

BUT they seem to have survived out there longer than other populations of mammoths. So….?

POINT:Concept of hyperdisease hypothesis We should expect to see evidence of…..

disease in the last generations of mammoths