History of Life on Earth - PowerPoint by historyman

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									History of Life on Earth
Yes, we are now admitting that it
could occur elsewhere.
Biological Evolution

   Genetic change over time
   Some rapid
    – Microevolution
    – Can be seen in one generation
   Some slow
    – Macroevolution
    – Takes many generations
How old is the earth?

   Study of sedimentary rock strata
   Radioisotope decay
    – % of final stable element
    – Determination of half-life
So what is a half-life?
http://www.carolina.com/chemistry/experiments/halflife.asp


   Half life is the time it takes half of the sample to
    decay
   Polonium-214                0.164 second
   Oxygen-15                   2 minutes
   Bismuth-212                 60.5 minutes
   Sodium-24                   15 hours
   Iodine-131                  8 days
   Phosphorus-32               14.3 days
   Cobalt-60                   5.3 years
   Hyrogen-3                   12.3 years
   Carbon-14                   5,730 years
   Plutonium-239               24,110 years
   Uranium-238                 4.5 billion years
How old is the earth?
Cont.
   Paleomagnetic dating
    – Based on movement of magnetic poles
    – Sedimentary and volcanic rock record
      changes in poles
        We’re over due for a pole change
        Pole drift is being monitored

   Continental drift
Earth is Always Changing
   Continental drift
    – Plate tectonics
           Crust on a fluid mantle
    – Geography changes and climate changes
           Mass extinctions
           Mass diversification
   Atmospheric changes
   Started out with H2O, CO2 , CH4 , and O3
   Oxygen creating bacteria first started changing our
    atmosphere
    – Early photosynthetic bacteria
    – Became cyanobacteria
Earth is Always Changing
cont.
   An early oxygen atmosphere would
    have prevented the formation of life as
    we know it
    – Oxygen reacts with organics and causes
      them to break down
    – Cells have mechanisms to handle oxygen
      safely
    – Plant production of oxygen made animal
      life possible
Earth is Always Changing
cont.
   The climate is never stable
    – It’s always global warming or cooling
    – If we’re not covered in ice, we’re toasty hot
          Changes in earth orbit and ocean currents can cause
           changes
    – We’ve never had global climatic homeostasis
          But humans sure would like it to be
    – As we warm earth’s politics will change
Earth is Always Changing
cont.
   Volcanoes
    – Usually short term changes
    – Unless it’s a really big volcano or a period
      of intense volcanic activity
    – Did you know that Yellow Stone National
      Park is a huge caldera?
          And it’s getting warmer
Earth is Always Changing
cont.
   External influences
    – We are always being hit by meteors
    – Not just the one at the end of the
      Cretaceous period
Fossil Record
   Good tool
    – Shows progression of evolution
    – Shows radiation of species
   Not excellent tool
    – Has holes
    – Some places just don’t form fossils well
    – Some species just don’t form fossils well
   Vocab word
    – Biota
           All living species in a particular region
   Extinction is the fate of all species
Walk Through History

   Precambrian > 600 mya
    – First O2 appears in atmosphere
    – Earliest life forms
    – Simple
    – In the sea
    – Advent of soft-bodies invertebrates
Walk Through History
Paleozoic
   Cambrian                   Ordovician
    – 550 to 500 mya            – 500 to 450 mya
    – Oxygen nears              – Brachiopods and
      current levels              mollusks
    – Gondwana is largest       – Mass extinction due
      land mass                   to climate change
    – Arthropods form           – Sea levels and
                                  temperature
                                  dropped
Walk Through History
Paleozoic cont.
   Silurian                   Divonian
    – 450 to 400 mya            –   400 to 350 mya
    – Northern continents       –   Shelled organisms
      form                      –   Fish evolution
    – Marine animals            –   Mosses
      leave the sea floor       –   Ferns
    – Land plants appear        –   Insects
    – First terrestrial         –   Amphibians
      arthropods
                                –   Mass extinctions
                                        Meteorites?
Walk Through History
Paleozoic cont.
   Carboniferous           Permian
    –   350 to 300 mya       –   300 to 250 mya
    –   Swamp forests        –   Pangea formed
    –   Flying insects       –   Earth cooled
    –   Reptiles             –   Glaciations
                             –   Meteorite hit
                             –   96% extinction
Walk Through History
Mesozoic
   Triassic                          Jurassic
    –   250 to 200 mya                 – 200 to 150 mya
    –   Pangea breaks up               – 2 large continents
    –   Inertebrates diversify                 Laurasia in north
    –   Conifers and seed plants               Gondwana in south
    –   Reptile radiation              –   Ray-finned fish
    –   Dinosaurs                      –   Salamanders
    –   Birds                          –   Flying reptiles
    –   Mass extinction                –   Angiosperms
            Meteor
Walk Through History
Mesozoic cont.
   Cretaceous
    – 150 to 50 mya
    – Sea invertebrates increase
    – Dinosaurs increase
    – Angiosperms increase
    – Mass extinction
         Meteor
Walk Through History
Cenozoic
   Tertiary                 Quarternary
    – 50 to 2 mya             – 2 mya to present
    – Earth dries and         – Pleistocene
      cools                         Lots of glaciation
    – Grasslands spread             Hominid evolution
    – Mammals diversify       – Holocene
                                    Recent times
Rates of Change

   Slow                        Gradual
    – Living fossils             – Records show
    – Adaptations ride out         massive changes
      the environmental            through time
      changes                          Horses used to be
                                        the size of cocker
    – Change very little                spaniels and have
          Gingko                       toes
           Sharks
       
                                Rapid
          Horseshoe crab
          Nautilus              – House finches in US
Rates of Extinction Vary
   Mass extinctions occur during rapid
    environmental changes
   Some lineages gradually fade out
    – Elephants
   Stable environments
    – Low extinction
    – Low evolution
   Changing environments
    – High extinction
    – High evolution

								
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