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Earth Science

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Begun 4.56 billion years ago (the birth of Earth until the start of the ... They are born alive (except platypus and spiny anteater babies who hatch from eggs. ... – PowerPoint PPT presentation

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Title: Earth Science


1
Chapter 13
  • Earth Science

2
The Precambrian
  • The Precambrian
  • Begun 4.56 billion years ago (the birth of Earth
    until the start of the Cambrian Over 4 billion
    years. This is 88 of the age of Earth.
  • Most Precambrian rocks do not contain fossils
  • Many rocks of this age are metamorphosed and
    deformed or extremely eroded.
  • Lots of missing layers and missing data.

3
  • Most Precambrian rock is buried deep under
    younger strata.
  • Large continental cores composed of Precambrian
    rock exist on every continent.
  • These are called shields

4
The evolution of Earths atmosphere
  • The evolution of Earths atmosphere
  • The atmosphere we breathe today consists of N, O2
    and a small amount of Ar and CO2 and H2O.
  • Earths original atmosphere was similar to the
    gases released in volcanic eruptions, CO2, H2O, N
    and other trace gases but NO O2.

5
  • Because the planet was cooling, the water vapor
    condensed to form clouds.
  • It began to rain, the rain continued to evaporate
    but as Earth cooled more, the water began to fill
    low areas, forming the oceans.
  • This reduced the water vapor in the air. It also
    reduced the CO2 because it became dissolved in
    the water.
  • The first life forms did not need O2.

6
  • Later, plants evolved that used photosynthesis
    and released O2.
  • Plants put O2 in our atmosphere.
  • At first, the Fe on earth began to react with the
    free O2. once the free Fe finished reacting,
    oxygen began to accumulate. This happened about
    2.5 BYA. We know this because of fossils of
    ocean organisms that require oxygen to live.

7
  • The most common Precambrian fossils are
    stromatolites.
  • These are algae colonies that layered calcium
    carbonate and grew in the uppermost layer. There
    are organisms living today that are similar to
    stromatolites.
  • Most Precambrian organisms preserved in rock are
    microscopic. These organisms are similar to
    bacteria existing today.

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  • Precambrian plants date back to about 3.5 BYA.
    Precambrian animals date back to the late
    Precambrian, about 2 BYA.
  • Most animal fossils are trace fossils, like
    trails and worm holes.

10
  • Modern, living stromatolites

11
  • The Paleozoic
  • This era comprises the most recent 540 million
    years.
  • The Paleozoic is the longest Era after the
    Precambrian.
  • Earth began to be home to many animals with hard
    body parts. Therefore there are lots of fossils
    dating from the Paleozoic.

12
Before Pangaea
  • The continents were arranged as two major
    continents with Gondwanna (Africa, South America,
    Antarctica) around the South Pole, and North
    America, Europe and what is now Siberia clustered
    together, forming Laurasia, somewhere at the
    equator. There were no living things on
    N.America during this time. An orogeny occurred,
    which eventually produced the Appalachian
    Mountains.

13
  • Trilobites lived during the Cambrian period.
  • There were more than 600 types of these animals.
  • During the Ordovician period, brachiopods were
    the dominant animals.
  • Brachiopods are now extinct except for one group.
  • Cephalopods began to appear during the
    Ordovician.
  • These included squid and octopus ancestors

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  • Cephalopods

16
  • Late Paleozoic
  • This is when Ancestral North America collided
    with Africa to form Pangaea.
  • The Appalachian Mountains were the result.
  • Plants adapted to survive at the waters edge,
    then to move farther from the water.
  • Early plants had no leaves.

17
  • By the late Devonian, fish had developed lungs to
    assist their breathing with gills.
  • There were lobe finned fish that lived on mud
    flats.
  • By the end of the Devonian there were true
    amphibians that existed.
  • The amphibians quickly diversified because they
    had no competition from other land animals.
  • Tropical swamps existed in the late Pennsylvanian
    which created our coal deposits.

18
  • The Great Paleozoic Extinction
  • The creation of Pangaea, the distribution of land
    and water had an effect on the world climate.
  • Vast areas of the northern continents became
    elevated above sea level
  • Vast areas became drier
  • 75 of land amphibians disappeared

19
  • Much of the marine life did not adapt and survive
    with 80-95 disappearing. This was the mother
    of all extinctions. The cause is uncertain. We
    know at least 2 million cubic km of lava flowed
    across Siberia. Sunlight could have been
    blocked, high concentrations of S gas forming
    H2SO4 could have poisoned life on land and in the
    sea. Life almost died out altogether.

20
  • Trilobites became extinct
  • Most brachiopods
  • Some corals
  • This set the stage for the survivors forming new
    biological communities that were more diverse
    than their predecessors.

21
  • The Mesozoic
  • Lasted 183 million years. Dicvided into three
    periods, Triassic, Jurassic and Cretaceous.
  • Marked the beginning of the breakup of Pangaea
  • Dinosaurs became dominant on land.
  • They were the major animal group for 100 million
    years.
  • Very few marine fossils found from the Triassic.
  • Shallow seas covered much of western North
    Amerida. The shallow seas created swamps which
    produced our coal deposits.

22
  • The breakup of Pangaea
  • A rift developed between eastern US and west
    coast of Africa.
  • This developed the Atlantic Ocean
  • New animals included reptiles with a shelled egg.
  • Water dwelling stage (like tadpole) was
    eliminated.

23
  • Some dinosaurs were carnivores, some herbivores
  • One group of reptiles began to fly (pterosaurs)
  • One group became very proficient (we have fossil
    remains of feathered Archaeopteryx) led to the
    evolution of birds.
  • Another group became sea dwellers (plesiosaurs
    and ichthyosaurs)
  • At the end of the Mesozoic there was another
    extinction event. The dinosaurs and the marine
    pleiosaurs and the pterosaurs died out.

24
  • Scientists believe that this was caused by a
    large meteorite colliding with Earth which caused
    huge quantities of dust to block out the sun.
  • Plants died.
  • Herbivores died.
  • Carnivores that ate the herbivores died.
  • Smaller animals probably survived because they
    needed less food than huge dinosaurs.

25
  • The Cenozoic
  • This means era of recent life
  • Dominant animals were the mammals.
  • Dominant plants were flowering plants.
    Angiosperms replaced gymnosperms

26
  • The evolution of flowering plants strongly
    influenced the development of birds and mammals.
  • Birds fed on seeds and fruits
  • Grasses developed during the middle Tertiary
    which allowed the success of Grazing animals that
    fed on the grasses.

27
  • Mammals had developed about the same time that
    dinosaurs emerged but they were small and
    primitive.
  • By the end of the Mesozoic, dinosaurs and other
    reptiles were gone.
  • The fossil record shows the replacement of the
    reptiles by mammals.

28
  • Mammals are different from reptiles.
  • They are born alive (except platypus and spiny
    anteater babies who hatch from eggs. These are
    very primitive mammals called monotremes)
  • They are warm blooded and can survive in cold
    regions. Hair insulates their bodies.
  • They can search for food anytime or any season
  • Their hearts and lungs are better developed.

29
  • Because there were many open niches, mammals
    developed rapidly.
  • They increased in size
  • Brain size increased
  • Teeth specialized to accommodate a particular
    diet
  • Limbs specialized to adapt to life in a
    particular environment.

30
  • Many large mammals became extinct at the end of
    the Pleistocene.
  • These included Mastodon, mammoth, giant beavers,
    saber toothed cats, large ground sloths, some
    horses, camels, giant bison.
  • The reason is not clear, these groups had
    survived several major glacial advances and
    interglacial periods.
  • One hypothesis is that humans hunted these
    mammals, selecting large forms. This is not
    accepted by all scientists.

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