Pg. 66

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Pg. 66 EXTINCTIONS Natural Disasters of epic
proportions 5 mass extinctions on Earth - know
geologic periods and ages of these events
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Pg. 66 1)Ordovician about 458 million years
ago a.) 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 pole at that time. Plate
tectonics ????More or less glaciers? ????Sea
level change results? Reef builder and warm
water species most profoundly effected WHY?
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• Pg. 66
• 2) Devonian
• About 375 million years ago
• A good link explaining cause
• Fauna included similar to Ordovician and fishes.
• a) marine life hit hard but land plants not
  affected
• 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

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Pg. 66 3)Permian 260 million years ago Good
link with explanation a.) 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-timing 1.) Slow event - occurring
over millions of years
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Pg. 66 3)Permian CONTINUED ADD A number of things
probably contributed-timing 2.) 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 fall a.) spreading at
mid-ocean ridge slowed-less volume in the
ocean b.) this caused the volume of ocean basins
to be decreasedshoreline moving seaward c.)
how effect 2??? ND pg. 438 fig. 15.16
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Pg. 66 3)Permian CONTINUED ADD A number of things
probably contributed-timing 4.) Siberian Traps
(warm the climate or did it?) a.) massive amount
of flood basalts b.) possible COUP DE
GRACE? c.) huge release of CO2 and other
Greenhouse gasses
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Pg. 67 4) Triassic About 240 million years
ago a) Amphibians and mammal-like reptiles
suffered great losses. b) 20 of marine
invertebrates families (groups)
gone. ADD Causes all have problems
explaining 1.) gradual climatic/sea level change
theory?-then why abrupt extinction? 2.)
impact?-no impact crater found 3.) 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.
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Pg. 67 5) Cretaceous BEEN HERE About 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
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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??? ADD Which is considered stronger
argument? WHY?
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Pg. 67-68 EVIDENCE PATTERNS IN EXTINCTIONS USED
TO DETERMINE CAUSE EVIDENCE 1) 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.
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Pg. 67-68 EVIDENCE PATTERNS IN EXTINCTIONS
USED TO DETERMINE CAUSE continued EVIDENCE 5) 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).
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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 to temp changes
(reefs demise) c) shelf water life goes vs.
deep ocean WHY? d) terrestrial life can adapt
(more mobile) better than marine so possibly have
higher probability of survival
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Pg. 68 POSSIBLE CAUSE-continued All come down
to climate change Cause of global cooling? 1)
Glacial Event - timing doesnt 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?
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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
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Pg. 69 2) Global Warming? a) modern
example 1982-83 El Nino entire species of clam
dies - off coast of SA Well - OK but that is
local how about global? Warming events dont
match with species compression pattern ANY
COMMENTS???
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Pg. 69 3) Habitat Loss - Changing sea levels
affect marine creatures doesnt explain
terrestrial (land critters). Sea level changes
due to plate tectonics (sea floor spreadinggt) and
glacial events. AGAIN ND pg. 438 Fig.
15-16 Impacts?? Could cause lots of global loss
of habitat.
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• Pg. 69
• 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 suppressed
• immune system
• b.) CT reveal tumors in certain species of
• dinosaurs (duckbills)
• Avian Flu and humans?

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• Pg. 69
• Predation? - possible cause for an interesting
• extinction of large Pleistocene mammals
• Two ideas for the Pleistocene mammals example
• 1.) Changing climate Problems? Too slow.
• a.) many large animals went extinct and no
  plants
• b.) mammals should not be so heavily impacted
  WHY?
• c.) glacial retreat should provide more habitat
• d.) 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?

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Pg. 69 Predation? continued ADD 3.) Another idea
for Pleistocene mammal loss. Those little
mammoths found on islands ....hmm Wrangel
Island Good explanation of the idea Mammoths
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.? POINTConcept of hyperdisease hypothesis
We should expect to see evidence of.. disease
in the last generations of mammoths