PowerPoint Presentation - Mass Extinctions

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PowerPoint Presentation - Mass Extinctions Powered By Docstoc
         By Michael Davis
         Josh Shindler
         Andrew Baldwin
What’s a mass extinction?
• a sharp decrease in the number of species in a
    relatively short period of time.
•    There different ways a mass extinction can
    occur including…
•   Asteroids
•   Comets
•   Global warming
•   Ice age
•   And more…
     How many mass extinctions have
     there been?
   Ordovician-Silurian Extinction
• 439 million years ago
• Caused by a drop in sea level as glaciers
  formed, then by rising sea levels as
  glaciers melted.
• Killed about 25% of marine families
• Killed 60% of marine genera
      Late Devonian extinction
  • About 364 million years ago
  • Not clear if it is 2 large mass extinctions or
    a series of small extinctions
  • About 22% of marine families were killed
  • About 57% of the genera were killed
  • Suggested that a asteroid impact was the
    prime cause
Permian-Triassic extinction
 • Most likely due to volcanic eruption,
 • an asteroid impact
 • or a near by super nova.
•   Informally called the “Great Dying”
•   Occurred about 251 million years ago
•   It was the most severe extinction
•   96% of all marine species were killed
•   70% of terrestrial vertebrate were killed
•   the extinction took a few million years
•   Normal levels of biodiversity did not become
    present until 6 million years after the end of the
 End Triassic extinction

Power Point Template
  • 199 million to 214 million years ago
  • caused by massive floods or lava erupting
    from central Atlantic province – an event
    that triggered the opening of the Atlantic
  • The volcanism may have lead to deadly
    global warming
  • 22% of Marine families
  • 52% of marine genera
  • Vertebrate deaths unknown
     Cretaceous-Tertiary extinction
 • No one knows exactly how this Mass
    Extinction happened and why it happened
    at such a rapid rate. Scientists have many
    theories but it boils down to about one
    major one and a few others due to
    Occoms razor.
• The first and the most favored theory is
 that an asteroid hit somewhere in the golf
 of Mexico in the Yucatan Peninsula 65
 million years ago. The Asteroid impact is
 site is called the Chixclub and is
 approximately 200 Kilometers across
 making the asteroid itself about 9 miles
  • caused Forest fires to start and ignited
     volcanic eruptions all over the glob as well
     as tidal waves, severe storms that would
     eliminated all sunlight. It would be six
     months before sunlight would reach the
     ground after such a blow. The dinosaurs,
     even in their prime, stood no chance
     without sunlight and plant life, ending the
     dinosaurs 165 million year reign.
  • One of the other theories is that climate change
      killed all of the plant eating dinosaurs due to
      lack of food from the climate change. The
      cretaceous period was tropical and so were
      almost 50 percent of the plants. If the
      temperature was to change drastically the plant
      eater’s food would slowly dwindle. With the
      plant eaters becoming extinct the carnivores
      would soon run out of food as well.
  • Volcanic eruptions have also been
      theorized to have killed of the dinosaurs.
      When volcanoes erupt they send clouds of
      dust, sulfuric acid, and poisonous gas that
      would have made it impossible to breath.
      This would result in the blocking of
      sunlight and a severe climate change.
      This would have been nearly impossible to
      survive in this environment
• Which do you think killed the dinosaurs????
The Big Five
• Ordovician-Silurian extinction - 439 million
    years ago,
•   Late Devonian extinction - 364 million years
•   Permian-Triassic extinction - 251 million
    years ago
•   End Triassic extinction, - 199 million to 214
    million years ago
•   Cretaceous-Tertiary extinction, about 65
    million years ago
    The sixth mass extinction?
    • This extinction is referred to as the
       Holocene extinction. This is named after
       what geologists call the period we as
       humans have been in. The immense
       amount of extinction during this period of
       plants and mammals has constituted is as
       a mass extinction to many scientists. The
       extinctions include birds, mammals,
       reptiles, and amphibians.
• This extinction is thought to have started once
 Homo sapiens started dispersing outward from
 Africa on the land bridges, hunting and
 gathering was the start of the extinctions
 induced by man. Today approximately 1,000
 species out of the worlds 10,000 are on the
 verge of extinction. There is no conclusive
 evidence but it is estimated that since Homo
 sapiens began hunting and gathering some
 500,000 – 1,000,000 species have become
 extinct, from over hunting, population, and
 most importantly pollution.
• What do you think, are we in the midst of
   a mass extinction???

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