earth science ch. 14—geologic...
TRANSCRIPT
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Earth Science
Ch. 14—Geologic Time
What is geologic time?
• The division of Earth’s history into time
units back to 4.6 b.y.a.
• Usually based on the life-forms that lived
during certain periods
• May be based on other criteria such as
geologic events.
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4 Major Subdivisions
of Geologic Time
• Eon
• Eras
• Periods
• Epochs
Eons
• Longest subdivision of time
• Based on the abundance of certain fossils.
• Divided into eras
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Eras
• Based on worldwide changes in types of
fossils present.
– For example, the end of the Mesozoic Era—
many kinds of invertebrates, birds, mammals,
and reptiles became extinct.
• Subdivided into periods.
Periods
• Units of geologic time characterized by
types of life existing worldwide at the time
and geologic events (e.g. plate tectonics &
mountains).
• May be divided into smaller time periods
called epochs (Only Cenozoic Era)
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Epochs
• Also characterized by differences in life-forms.
• Some differences can vary from continent to
continent.
• Used only for Cenozoic Era, otherwise, they are
simply referred to as early, middle, late.
• Why are we able to subdivide the Cenozoic Era
and generally, not the others.
What about your life?
• Could you subdivide your life into Eons,
Eras, Periods, and Epochs?
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Organic Evolution
• Changes in species over time.
• Pepper Moths
Napoleon Dynamite!!!!!!
http://www.ilovenapoleondynamite.com/na
poleon_dynamite_video_liger.php
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What is a species?
• A group of organisms that normally reproduce among themselves and produce fertile offspring.
• Ex. Dogs reproduce with dogs
• Some organisms of different species can breed, but the offspring are infertile.
– Ex. Lion and Tiger
• They produce a Tigon, Liger, or Tiglon
• Typically, they would never breed in the wild.
LIGER VIDEO
LIGER VIDEO 2
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Other Examples
Natural Selection• Charles Darwin—1831-
1836– Sailed around the world in
the HMS Beagle
– He proposed “survival of the fittest”
– As species breed, those with traits necessary will reproduce and survive, AND those without the traits needed would die off.
– Eventually, you’re only left with those traits necessary.
– A new species may be formed.
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Earth’s Early History
• PRECAMBRIAN TIME (4.6 byo-544 myo)
– The longest part of Earth’s history
– It includes three Eons
• Hadean Eon
• Archean Eon
• Proterozoic Eon
– Some Facts:
• The oldest rocks are about 4 byo.
Why so little is known about
Precambrian Time
• Precambrian rocks have been deeply
buried.
• Rocks have been altered by
heat/pressure.
• Most Precambrian organisms lacked hard
parts.
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Precambrian Time—early life
• Cyanobacteria—blue-green algae thought to be one of the earliest life forms on Earth.
Early Life
• Scientists study ancient Stromatolites (layered mats formed by cyanobacteria)
• They appeared 3.5 byo
• They contained chlorophyll which they used for photosynthesis.
• They were crucial in forming our oxygen rich atmosphere.
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Precambrian Time—early life• The ozone layer began
to develop (Blocking UV rays)
– It was needed to protect organisms
• The first invertebrates appeared towards the end of Precambrian Time.
Precambrian
Time• Edicara Hills—southern
Australia
– Scientists discovered animals similar to today’s jellyfish, worms, & soft corals.
– They became known as the Edicaran Fauna:
• Rangea
• Spriggina
• Cyclomedusa
• Dickensonia
• Edicaran animals were bottom dwellers
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Phanerozoic Eon
• Following Precambrian Time is the
Phanerozoic Eon:
– Paleozoic Era
– Mesozoic Era
– Cenozoic Era
The Paleozoic Era
• “Era of Ancient Life”
• 544-248 mya
• Organisms began to develop hard parts.– Ex. Shells
• Warm shallow seas covered most of the Earth.– Most life was marine
– Brachiopods & crinoids were common
• Vertebrates (animals with backbones) evolved.
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Paleozoic Era
• First vertebrates—fishlike creatures
without jaws.
• The Paleozoic Era is broken into 7 periods
Paleozoic
Era
• 7 Periods
– Cambrian Period
– Ordovician Period
• Trilobites Develop
• Marked by the beginning of the Appalachians
• First vertebrates (jawless fish)
– Silurian Period
• First land plants
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Paleozoic Era
• Devonian Period
– Fish became dominant
– Plant life developed on land
– Animals began to move to
land
• Who were the first land
animals?
– Amphibians
Paleozoic Era
• Mississippian Period– Amphibians were dominant
– They had a dual life
– They returned to the water to lay their eggs
– First insect
• Pennsylvanian Period– Shallow seas began to withdraw
– Reptiles evolved• They had eggs with a membrane
• They laid their eggs on land
• They had skin with scales which helped prevent fluid loss.
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Paleozoic Era
• Permian Period
– End of the Era
• Mass extinctions from changes in the environment or plate tectonics
• Pangea formed
• Mountain building caused the seas to dry out and deserts to form.
– Mass extinctions
• More than 90% of marine species went extinct.
• 70% of land species died off
Paleozoic Era
• Other Hypotheses for mass extinction
– Volcanoes
– Large asteroid or comet colliding 248 mya.
– Multiple events
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The Mesozoic Era
• “Era of Middle Life”
• Mesoszoic Era (3 Min)
• Began 248 mya
• Broken into three periods
– Triassic Period (248-208 mya)
– Jurassic Period (208-144 mya)
– Cretaceous Period (144-65 mya)
Mesozoic Era
• Pangaea broke apart into 2 masses
– Laurasia (North America, Europe, Asia)
– Gondwandaland (South America, Africa, Antarctica, Australia, India)
– They broke apart further later.
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Mesozoic Era
• Reptiles evolved into archosaurs “ruling lizard”– Common ancestor of crocodiles, dinosaurs, & birds
– All have gone extinct except birds and crocodiles
• First dinosaurs appeared
Dinosaurs• So, what do we know about the
dinosaurs?
• First small dinosaurs appeared in the triassic period
– Foot Prints
• They were far apart (they were fast)
• Some as fast as 65 mph
– Nurtured Young
– Ex. Maisaura “good mother dinosaur”
• Built nest
• Cared for young
– Bone Structure
• In exothermic (cold blooded), their bones are like rings
• In endothermic (warm blooded) their bones are not like rings
• Some dinosaurs don’t have rings!!!
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Mammals
• First mammals appeared in the Triassic
period
– warm blooded (endothermic)
– hair
– females produce milk
– Note: some lay eggs
• What are some examples
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Egg Layers
• Some mammals are egg
layers
• All are monotremes
– Two species of “spiny ant
eaters”
– Duck-Billed Platypus
Birds
• appeared during Jurassic Period (After the dinosaurs)
• Archaeopteryx
– wings/feathers like bird
– teeth/claws like meat eater
– probably shared ancestor with birds
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Gymnosperms
• First appeared in Cretaceous Period, but
evolved now.
– Non flowering plants
– Ex. Ginko, Pines
Angiosperms
• Flowering
Plants
– Ex. Maple,
Oak
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End of the Mesozoic Era• Ended 65 mya
• Major extinctions: land and marine species
• Including dinosaurs
• ABC NEWS CARNEGIE--DINOSAURS (3 Min)
• Hypothesis include: meteor, comet, & volcanoes
• Plants died, resulting in animal death
• Not everything died
• All organisms around today are descendants of the survivors
The Cenozoic Era
• “Era of recent Life”
• This era is broken into two periods:
– Tertiary Period (Began 65 mya)
• This was a time of mountain building
– Alps (Europe)
– Andes (South America)
– Himalaya (India collided with Asia)
– This may have triggered the ice ages
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Cenozoic Era
• Mammals evolved further
• Expanding grasslands—favored grazing
eaters such as horses, camels, deer, and
elephants
• Many mammals became larger
• Some mammals changed to live in the sea
(whales and dolphins)
Cenozoic Era
• Australia and South America separated from Antarctica
• Species became isolated & evolved separately
• Ex. Australia’s marsupials
• Quarternary Period (Began 1.8 mya)– Homo sapiens is estimated to have appeared
140,000 years ago.
– Evidence suggests early hominids were hunters.