Pg. 66 EXTINCTIONS Natural Disasters of epic proportions 5 mass extinctions on Earth - know geologic periods andgeologic periods ages of these events

Pg. 66 1)Ordovician about 458 million years ago a.) marine life on sea floor and near surface.marine life Reef builders hit hard, few reefs survive into Silurian time. *Why ? glaciation at that time = cool temperatures A good link explaining morelink ADD Gondwana (large landmass) was near the south pole at that time. Plate tectonicsPlate tectonics ????More or less glaciers? ????Sea level change results? Reef builder and warm water species most profoundly effected WHY?

Pg. 66 2) DevonianDevonian About 375 million years ago A good link explaining causelink Fauna included similar to Ordovician and fishes.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 TectonicsPlate Tectonics

Pg. 66 3)Permian 260 million years ago Good link with explanationlink a.) greatest mass extinction of life on earth % 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

Pg. 66 3)Permian CONTINUED ADD A number of things probably contributed-timing 2.) Pangaea formed and changed…Pangaea a.) the amount of warm shallow oceans-DECREASEDamount 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 decreased=shoreline moving seaward c.) how effect #2??? ND pg. 438 fig

Pg. 66 3)Permian CONTINUED ADD A number of things probably contributed-timing 4.) Siberian Traps (warm the climate or did it?)Siberian Traps a.) massive amount of flood basalts b.) possible COUP DE GRACE? c.) huge release of CO 2 and other Greenhouse gasses

Pg. 67 4) TriassicTriassic 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(CAMP)- *Cooling the culprit? Added new open niches for dinos to fill.

Pg. 67 5) CretaceousCretaceous 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

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???(Deccan Traps)- ADD Which is considered stronger argument? WHY?

Pg 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 toextended range from tropics higher lat. they become compressed (tropical wiped out and others migrate) 4) Shallow ocean shelf affected more than deep ocean.

Pg 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).periodicity to extinctions

Pg. 68 POSSIBLE CAUSE *All come down to climate change* 1) Global cooling - fits with: a) compression of speciescompression 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 marineso 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 = coolingocean circulation 3) Carbon Dioxide shortage? Devonian - plants explode and use CO 2. Could this cause a cooling? WHY/HOW? Opposite of global warming?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. 69 2) Global Warming? a) modern example 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 compression pattern ANY COMMENTS???

Pg. 69 3) 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 Impacts?? Could cause lots of global loss of habitat.

Pg. 69 4)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?

Pg. 69 5)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?

Pg. 69 Predation? continued ADD 3.) Another idea for Pleistocene mammal loss. Those little mammoths found on islands....hmm…little mammoths 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….? POINT:Concept of hyperdisease hypothesishyperdisease hypothesis We should expect to see evidence of….. disease in the last generations of mammoths