A Quick Look at the History of Life on Earth Part 2 - PowerPoint PPT Presentation

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A Quick Look at the History of Life on Earth Part 2


Paleozoic Highlights the move to land Life moved from the sea to land during the middle of the Paleozoic Era. - First bacteria and fungi make soil ... – PowerPoint PPT presentation

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Title: A Quick Look at the History of Life on Earth Part 2

A Quick Look at the History of Life on Earth Part
  • The Phanerozoic Eon
  • Including the Paleozoic, Mesozoic and Cenozoic

Paleozoic Era
  • Paleozoic old life
  • - bounded by two major events in life history
  • - begins with the Cambrian explosion
  • -ends with the Permian
  • extinction over 90 of life
  • disappeared 250mya

The Cambrian Explosion
  • a seemingly sudden appearance of large numbers of
    multicellular organisms in the fossil record.
  • - Rocks older than this appeared to have no
    fossils (because they are too small to see, and
    because the multicellular organisms didnt have
    hard parts to preserve.
  • Most types of multicellular organisms present
    today appeared at this time.
  • Many other groups of organisms appeared and then
    went extinct during
  • this period
  • Successful forms tended to be large with shells
    or exoskeletons for support

Other Paleozoic Highlights
  • Early Paleozoic dominated by marine invertebrates
  • Appearance and evolution of fish during the
    middle period of the Paleozoic first fish had
    no jaws and cartilage skeletons
  • - Jaws developed
  • - cartilage skeletons give way to bones.

Paleozoic Highlights continued
  • Major change in vertebrates tetrapods (animals
    with 4 limbs) appear in the mid-Paleozoic.
  • - First as paired fins on fish, then later as
  • Amphibians and reptiles appeared.
  • - Reptiles were not common until the
    next era, the Mesozoic.

Paleozoic Highlights the move to land
  • Life moved from the sea to land during the middle
    of the Paleozoic Era.
  • - First bacteria and fungi make soil
  • - followed by plants
  • - then arthropods (insects, etc.)
  • - finally vertebrates.
  • Large areas of swamp vegetation from this period
    were converted into coal after being buried and

Paleozoic Highlights- the move to land
  • Why now?
  • - The oceans had been the only shield life had
    against UV light
  • - UV light damages DNA and
  • threatens life
  • - by the mid Paleozoic, oxygen in the upper
    atmosphere formed ozone (O3)
  • - ozone blocks out much of the suns UV
    light making life on land possible

Permian Extinction-the Dramatic End of
the Paleozoic Era
  • Largest mass extinction in earth
  • history - 250mya
  • 90 of species disappeared
  • Multiple ideas exist about the cause
  • - massive volcanic eruptions in Siberia
    lasting 1 million yrs coincided with the
  • - climate change
  • - evidence for both global warming and
    glaciation exists
  • The mass extinction cleared the way for the rise
    of the dinosaurs
  • during the Mesozoic era

Mesozoic Era 250mya 65mya
  • Mesozoic middle life
  • Age of the dinosaurs
  • - reptiles were the largest animals on land
    and in the sea during this period.
  • major diversification of flowering plants late in
    the Mesozoic.
  • Supercontinent Pangea breaks into many continents
    allowed speciation to occur in many different
  • Birds and mammals appear but arent prominent.
  • Ends with a mass extinction Cretaceous

Cretaceous Extinction
  • Thought to have resulted from a large asteroid
    striking the earth
  • - drove huge amounts of dust to into the
    atmosphere and blocked out sunlight reducing
  • - reduced primary productivity
  • - Evidence to support
  • - worldwide layer of iridium found at
    correct age in rocks
  • very rare in earth rocks common in
  • meteors, asteroids, comets etc.
  • - massive impact crater found off of
  • the Yucatan penninsula of Mexico
  • - 100 mi in diameter
  • - correct age

Cenozoic Era- 65mya - present
  • Cenozoic New Life
  • Mammals become the dominant life form on land.
    An adaptive radiation that took advantage of the
    sudden loss of dinosaurs.
  • Another large group evolves the grasses.
  • Adaptive radiation of birds and flowering plants.
  • Fish, amphibians and reptiles dont change much
    during the Cenozoic.
  • Geologically, continents that had been separated
    started to collide Africa with Europe, North
    America with South America, India with Asia
  • Hominids appear 5 mya
  • modern humans (genus Homo)2 mya
  • - Homo Sapiens approx 200,000 ya

Cenozoic Life
  • Earth forms 4.6 billion years ago
  • Solid surface forms 4 billion years ago
  • Life starts (?) 3.8 billion years ago
  • Age of Bacteria Archaean era
  • Oxygen atmosphere develops 2 billion years ago.
  • Eukaryotes develop. Proterozoic era
  • Edicarian life 650 million years ago. First
    multicellular life, forms unknown today
  • Cambrian explosion most current life forms
    appear 550 million years ago
  • Paleozoic era 550 250 million years ago.
    Marine invertebrates, fishes, amphibians,
    invasion of the land. Coal formation.
  • Permian mass extinction 250 million years ago.
    95 of all life dies end of Paleozoic
  • Mesozoic 250-65 million years ago. Age of the
    dinosaurs (reptiles). Mammals, birds, and
    flowering plants appear
  • Cretaceous mass extinction asteroid hits the
    Earth, killing much of life, including the
  • Cenozoic era 65 million years ago till present.
    Mammals dominant
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