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The geologic time scale began when _______________________
and goes on until __________________________.
At the end of each era a ______________________________
occurred, many kinds of organisms died out, although there were
other extinctions going on during each period of geologic time.
Using the fossil record, paleontologists have created an idea
of the different types of common _________________ in each
____________________ period.
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The geologic time scale is a record of the major events and diversity
of life forms present in Earth’s history.
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-Few fossils because the life forms were softbodied and had no _________________________.
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-There was a rise of simple organisms such as
jellyfish and sea worms by the end of the era.
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-Began with simple life forms such as
________________ and simple _____________.
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Biological Events:
-5 major events occurred during this era:
(1) the formation of the Sun and light
(2) the creation of the Earth
(3) the creation of the atmosphere through
____________________ out-gassing
(4) the creation of the _______________.
(5) the creation of ___________.
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-The Precambrian Era is Earth's ___________ era
of time.
- It began with the creation of the Earth around
_______ billion years ago.
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Time Span:
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Geological Events:
Precambrian Era
Precambrian Era
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-The mass ____________________ that ended the
era caused most marine invertebrates as well as
amphibians to disappear.
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Biological Events:
Plant Life
-Early land plants included simple ______________,
____________, and then cone-bearing plants.
-By the end of the era, ___________ plants were
common.
Paleozoic Era
Animal Life
-Began with the early ___________________, such
as trilobites and brachiopods
- Continued to develop early vertebrate _________,
arachnids and insects
- Later came the first amphibians, and near the era’s
end the ____________________ became dominant.
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Geological Events:
Paleozoic Era
Geological Events:
Mesozoic Era
Time Span:
-_______________________ were the dominant
animals of this era, including the various dinosaurs.
-Small mammals and _____________ also appeared.
-Toward the end of the era, _______________ plants
appeared and the kinds of mammals
_______________________.
-The mass extinction that ended the era caused the
__________________________ to become extinct.
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Mesozoic Era
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Biological Events:
1. What is the geologic time scale?
Cenozoic Era
Time Span:
2. How does the geologic time scale further our
understanding about the biodiversity on our planet?
3. What is the oldest era? How long did it last?
What was happening during this era?
-New mammals appeared while others became
extinct.
* Mammals had to evolve to ____________
to different environments.
-The diversity of life forms increased.
-Flowering plants became __________ common.
4. How did the mass extinctions lead way to new
forms of life?
5. Imagine you time-traveled to the Paleozoic era
and had to describe to a friend what you saw. Write
at least 3 sentences describing it. Be as creative as
possible and write in complete sentences.
- Many mountain ranges formed
* Examples: Alps in __________________,
Himalayas in __________________ &
Rocky Mountains in the ______________.
Cenozoic Era
7. Which era would you most like to visit and why?
Include at least three reasons in your answer. Write
in complete sentences!
-__________________ are also part of the most
recent period of this era.
Divisions of Geologic Time
Geological Events:
 Eras are subdivided into periods.
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Biological Events:
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can be used to illustrate the vastness of
___________ involved in and to show
the diversity of __________ evident
across geologic time.
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 Various models, diagrams, and pictures
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 Periods are subdivided into epochs.