Download Geologic Time: Studying Earth`s History and the Evolution

Geologic Time:
Studying Earth’s History and
the Evolution of Life
I. The Early Earth
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The Earth and our solar system formed approx.
4.6 billion years ago.
The early Earth was hot and volatile; as it cooled
off the oceans filled with water and the
atmosphere formed.
The early atmosphere was composed of
primarily CO2; the earliest one-celled organisms
that carried on photosynthesis gradually
converted it into and oxygen-rich atmosphere.
The Early Earth From Space
The Early Earth’s Surface
What is the Geologic Time Scale?
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It is a relative time scale based on fossil
evidence.
Geologic time is split into smaller units:
Eons→Eras→Periods→Epochs
Present day is located at the top of the chart (0
million years ago) and events go farther back
in time as you look towards the bottom of the
scale.
II.Geologic Maps
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Geologists study the geologic time scale for
many reasons; one of them being that they
want to relate what we find out about the age of
the rocks to construct geologic maps.
The Generalized Bedrock Geology Map (Pg.
3 ESRT) and the Generalized Landscape
Regions of New York State Map (Pg.2
ESRT) can be used with the geologic time scale
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to determine the age of the bedrock throughout
New York State.
They also can provide general information about
local rock types, the ages of bedrock, types of
fossils likely to be found, and the geologic
history of your community.
IV. The Columns on the Time Scale
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Life on Earth: Gives information about
what life forms lived on Earth from the
beginning until the present day.
As you look down the column, keep in
mind that life gets simpler as we go back
in time.
Example:
Humans→Mammals→Dinosaurs→Reptiles→
Amphibians→Fish→
Soft-bodied marine organisms
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Rock Record in NYS: Lists information about
which time periods are represented by rocks in
NYS.
Time Distribution of Fossils: Lists several
index fossils that are represented in NYS.
Each fossil at the bottom of the chart has a
letter that corresponds to the group of animals
that fossil belongs to and the time when the
animal lived on Earth.
The bar a fossil sits on represents the group of
animals it belongs to, and the length of the bar
represents the length of time the group of
animals lived on Earth.
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Important Geologic Events in New
York:
This column lists major changes to the
landscape regions in New York State.
An OROGENY is a period of mountain
building. The major orogenies in NY are
listed, indicating times of crustal uplift.
Inferred Positions of Earth’s
Landmasses:
There are five diagrams that show the
movement of Earth’s landmasses over time.
Pay special attention to the time periods
each diagram represents and where North
America is in relation to the equator.
Evolution
One of the most important facts
illustrated by the Geologic Time Scale
is the evolution of life forms over
time.
 Life has continually evolved, or
changed, from very simple life forms
to more complex life forms over time.
 Life on earth continues to evolve.
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How do animals change over time?
Scientists are not sure how life began on Earth.
They know that life on Earth began before the
Cambrian Period, but early life forms were onecelled simple creatures that lived in water.
Geologists believe that many forms of life may
have existed in the Precambrian but they had no
hard parts (shells or bones) and therefore left no
fossils.
As scientists studied the fossil record they found
that more complex organisms developed as time
went on, and that many organisms disappeared
from the fossil record completely.
Explanation for Evolution
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Scientists looked for an answer that would
explain why certain members of a species
went extinct, while others seemed to
thrive.
They found that within each species there
are individual variations in size, shape,
and other traits, or characteristics.
Charles Darwin is the scientist credited
with proposing the Theory of Organic
Evolution.
What did Darwin Say?
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Darwin proposed that individuals within a
species that have traits that better adapt them
to their environment will survive longer and have
more offspring.
Their offspring inherit their desirable
characteristics and are able to survive in the
environment too.
Eventually, an increasing number if individuals in
a species will possess the desirable traits.
The number of individuals who do not have the
desirable traits will decrease, as they can’t
survive as well in the environment.
Examples of Natural Selection