ESYS 150 LECTURE 17 THE GREAT DYINGS

1. ESYS 150 LECTURE 17THE GREAT DYINGS Extinctions and Geologic Time Species Extinction and the Fossil Record Mass Extinctions during the Phanerozoic Possible Causes Examples of Extinctions

2. EXTINCTIONS AND GEOLOGICAL TIMEUNDERSTANDING EXTINCTIONSMammoths Mammoths very different from Elephants. Once there were many. Now they have gone extinct. Cuvier 1786 argued that this showed extinctions occurred. He noticed that fossils appeared and then died out in sedimentary sequences

3. EXTINCTIONS AND GEOLOGICAL TIMEUNDERSTANDING EXTINCTIONSLaw of Superposition Fossils (bones, shells) made abrupt first appearances and then disappeared. In a non-overturned sequence of rocks the lower beds are the oldest. Clearly first appearance of fossils and their disappearance can be used to classify beds. In 1799 William Smith published a list of the sedimentary strata in England and the contained fossils

4. EXTINCTIONS AND GEOLOICAL TIMEUNDERSTANDING EXTINCTIONSGeological maps and time scale Smith argued that unique fossil assemblages indicated specific intervals of sedimentary strata. (Law of Faunal Assemblages) He used the strata to identify strata of similar age and constructed first geological map in 1815. Geologists all over the world classified and divided vertical columns based on their differing fossil assemblages. By 1841 they had compiled a standard geological column for the world based on fossils. This was the first geological time scale. This has been been refined and quantified using radiometric dating of associated igneous rocks

5. EXTINCTIONS AND GEOLOGICAL TIMEBRIEF HISTORY OF LIFE Three major branches of life: Archaea, Bacteria and Eukarya (plants animals). 3.85 Billion years ago Archaea were alive reproducing and evolving getting energy from breaking chemical bonds of molecules. 3.5 Billion years ago photosynthetic bacteria removed CO2 and combined it with water to give off oxygen. Lead to radical change in composition of Atmosphere. Initially organism reproduced by a simple division of their cells. 1 billion years ago sexual reproduction appeared. The mixing pf genetic material speeded up evolutionary change by thousands of times.

6. EXTINCTIONS AND GEOLOGICAL TIMEEARLY LIFE During early history organism lived below the surface in the oceans and within the sediments. When O2 given off during photosynthesis built up into a large volume, some was altered to O3 which built a shield from Sun’s lethal ultra violet radiation. With the protective atmospheric cover multi-cellular life came onto the surface of the planet. 670 million years ago have the oldest multi-cellular animal life 544 million year ago have huge burst of evolutionary change.

7. EXTINCTIONS AND GEOLOGICAL TIMEGEOLOGICAL TIME SCALE

8. EXTINCTIONS AND GEOLOGICAL TIMEGEOLOGICAL TIME SCALEExplanation of names EON PHANEROZOIC Revealed life PRE-CAMBRIAN Pre first stage Phan. HADEAN Eon of “Hell” ERA Cenozoic New life Mesozoic Middle life Paleozoic Old Life Proterozoic Early Life Archean Ancient era

9. EXTINCTIONS AND GEOLOGICAL TIMEGEOLOGICAL TIME SCALEExplanation of names PERIOD QUATERNARY Fourth Period TERTIARY Third Period CRETACEOUS Chalk Deposits JURASSIC Jura Mountains TRIASSIC Three fold division PERMIAN Perm CARBONIFEROUS Coal beds DEVONIAN Devon, UK SILURIAN Celtic tribe ORDIVICIAN Celtic tribe CAMBRIAN Roman name Wales

10. EXTINCTIONS AND GEOLOGICAL TIMEHISTORY OF LIFEFamilies with mineralized hard parts through time Overall trend has been increase in diversity and abundance with time. But have had major setbacks and reorganizations. Have times at which up to 50% have died off. To understand this have to look at the species level.

11. SPECIES AND THE FOSSIL RECORDPARTIAL HIERARCHY OF LIFE: EXAMPLE HUMANS Linneaus in 18th century laid out classification shown above. Species is a population that can breed freely and produce viable offspring. Share a common pool of genetic material (genome). As genes mutate and are recombined in sexual reproduction, geographically segregated populations develop differences that create a new species. This is the process of evolution wherein changes of the genetic pool lead to the origins of a new species.

12. SPECIES AND THE FOSSIL RECORDSPECIESMass Extinctions Species subject to many environmental changes. Some survive others die out. Most species extinct. Only 0.1% around today. Each species is non recurring. Extinctions clear out living space for the surviving or new organisms Constant elimination of the old and refilling of space by the new creates the incredible variety of life today. Background extinctions occur at a moderate rate. Mass extinctions fast but relatively uncommon. Following a mass extinction the Earth take on a completely different appearance as the survivors are joined by new species.

13. SPECIES AND THE FOSSIL RECORDTHE TROPICAL REEF EXAMPLEExtinctions of the tropical reefs A tropical coral reef. Today built by scleractinian (stony or hard) corals along with framework building Created shelters where numerous other species survive. Fossil record shows how much these have changed through time.

14. SPECIES AND THE FOSSIL RECORDTHE TROPICAL REEF EXAMPLEGeological column and reef building organisms Six major successions of reef building organisms. After each mass extinction of the entire reef, there was along period before other creature could fill the environmental void Species are different in each reef phase.

15. MASS EXTINCTIONS: PHANEROZOICEXTINCTION PATTERNSMarine invertebrates and protozoans versus time. Extinction occurs on species level. Too many to plot extinctions with time. Operate at the level of genus. Plot % extinctions versus geological time. % extinctions = number extinctions / number of genera alive at that time. % extinctions has declined with time but there are still some huge excursions Excursion correlate with divisions in geological time scale.

16. MASS EXTINCTIONS:PHANEROZOICEXTINCTION PATTERNSGeological time scale showing the mass extinctions. Size of arrow indicates magnitude of extinction. Note how the largest ones correlate with the divisions in the geological time scale. Statistical analysis shows that every 100 million years have event that removes 65% of the species. Every 10 million years have an event that removes 30% of the species.

17. POSSIBLE CAUSES MASS EXTINCTIONSOVERVIEW Plate tectonics and Sea level changes Volcanic Climate change Extra terrestrial Biological Multiple

18. POSSIBLE CAUSES MASS EXTINCTIONSPLATE TECTONICSSurface elevation as a percentage of the Earth’s area 71% of present earth ocean, 29% land. Sea level rise could decrease percentage to 20%, a sea level drop could increase it to 35% Area of continent very dependent on height of sea level

19. POSSIBLE CAUSES MASS EXTINCTIONSPLATE TECTONICSIncrease in spreading rates During Cretaceous there was a major increase in spreading rates. Ocean volume increases and water spills out on to the continents flooding them

20. POSSIBLE CAUSES MASS EXTINCTIONSPLATE TECTONICS Numbers and sizes of continents When continents combined in super continent of Pangea increased likely area of harsh interior would reduce # species Continental Position and Glaciation When continents near the pole continents buried in great ice sheets. Puts great pressure on species.

21. POSSIBLE CASUES MASS EXTINCTIONSSEA-LEVEL CHANGESSea-level changes past 130 million years Melt all the glaciers: sea-level will rise by 70m 20,000 years age during last ice age had three times as much ice on the continents. Sea-level was dropped by 140m. Rapid shifts in sea-level can cause big shifts in the area of land covered by water. Add this to seafloor spreading effects can have large change

22. POSSIBLE CAUSES MASS EXTINCTIONS VOLCANIC CAUSES Outpouring flood basalts Changes atmospheric conditions, goes very cold then warm. Leads to great stress on species. CLIMATE CHANGES Changing Atmosphere or Wind Patterns Species find it very difficult to deal with cooling and drying. Again leads to great stress on the species.

23. POSSIBLE CAUSES MASS EXTINCTIONSEXTRA-TERRESTRIAL CAUSESMeteorite/Asteroid impact Large body hits Earth. Striking causes fires, tsunami, acid rain Then huge dust cloud that blocks out sunlight for months or years. Becomes very cold Dust remains aloft. Eventually creates a greenhouse rise in temperature. Very traumatic for species

24. POSSIBLE CAUSES MASS EXTINCTIONSBIOLOGICAL CAUSES Space area effects: Reduction in area causes species to go extinct Random extinction In a random walk, will run up against an absorbing boundary. This boundary extinction Predation and Epidemic Disease Viruses or “Homo Sapiens” MULTIPLE CAUSES To produce a mass extinction need multiple causes.

25. EXMPLES OF MASS EXTINCTIONSSUMMARY Ordovician Devonian Permian* Triassic Cretaceous* Quaternary

26. EXAMPLES OF MASS EXTINCTIONSPERMIANSiberian Flood Basalts End of Permian Due to formation of super continent reduced inland seas. Interior land masses had very rugged climate. Ocean composition different due to disappearance of the polar seas Siberian Flood basalts (251 Ma) Basalts flooded over land, released huge amounts methane, water, CO2, Caused very cold winter followed by long period of Greenhouse warming. Result Left impoverished global fauna and only the hardy warm blooded creatures survived. New species eventually included the Dinosaurs

27. EXAMPLES OF MASS EXTINCTIONSCRETACEOUSWhat happened: Dinosaurs to Mammals At end of Cretaceous had developed a wide diversity of species. Included mollusks, bivalves, snails ammonites, fishes, crocodiles, rodents and dinosaurs. At end of the Cretaceous 35% genera and 65% of species died off in a very short time. They were replaced by flowering plants and Mammals Interesting to note that the new mammals took over the same roles as the Dinosaurs

28. EXAMPLES OF MASS EXTINCTIONS CRETACEOUS Dinosaurs to Mammals Mammals took over the role of the Dinosaurs. Flowering plants took over the dominant role of the flowerless seed plants (conifers an example).

29. EXAMPLES OF MASS EXTINCTIONSCRETACEOUSWhat caused the extinctions Sea level change During last 18 my of Cretaceous seas retreated, climate cooled Vegetation changed, animal life declined. Deccan Traps Flood Basalt Massive flood basalts cover most of west central India. Came out in less than I million years 65.5 Ma. Produced major drop in temperature followed by warming. Chicxulub Impact Impact hit northern Yucatan, Mexico 65 Ma. Worst case scenario have 10 km asteroid blasts hole 60 km deep and 100 - 200 km in diameter. Huge earthquake, massive tsunami, 1000 km radius fireball. Acid rain followed by year long winter due to dust blocking suns rays. When dust settled greenhouse gases still aloft creates very warm temperatures. Devastating effect upon species.

30. EXAMPLES OF MASS EXTINCTIONSQUATERNARYMass extinctions due predation of humans American species that went extinct 12000 - 8000 BP Humans arrived in the America’s 13000 years ago and immediately a large number of species went extinct. As human population increases the number of species of animal decreases