Fossils 8-2.2
8-2.2 -- Summarize how scientists study Earth’s past environment and
diverse life-forms by examining different types of fossils (including molds,
casts, petrified fossils, preserved
and carbonized remains of plants and animals, and trace fossils).
Falcon Focus
• HOW DO SEDIMENATRY ROCKS
FORM?
• Essential Question: WHY DO SCIENTISTS
STUDY FOSSILS FROM MILLIONS OF YEARS
AGO?
REBUS
FOSSILS
Clues to Earth’s Past Creatures
and Environment
SC Standard 8-2.2
Summarize how scientists study
Earth’s past environment and
diverse life forms by examining
different types of fossils.
STEPS TO FOSSIL
FORMATION
• AS YOU LOOK AT THE VIDEO, SEE IF
YOU CAN FIGURE OUT THE STEPS TO
FOSSIL FORMATION
http:///wwww.youtube.comatch?v=3rkGu0BItKM
Fossil Formation
In the first step of fossil formation an
animal or plant must die in or near water
or near enough to fall in shortly after death.
In the following example a trilobite has died
of old age on the bottom of the sea.
Bacteria consume the soft body parts but
leave the hard exoskeleton intact.
2nd Step: Sedimentation
As time passes sediments bury
the exoskeleton. The faster this
happens the more likely
fossilization will occur. Land and
mud slides definitely help. River
deltas are also good for quick
accumulation of sediments. This
further insulates our trilobite from
decomposition. Now we have
fossil formation in progress.
3rd Step: Permineralization
As the sediments continue to pile on, the lower
layers become compacted by the weight of the
layers on top. Over time, this pressure turns the
sediments into rock.
If mineral-rich water percolates down
through the sediments, the fossil formation
process has an even better chance of
preserving our ancient animal. Some of the
minerals stick to the particles of sediment,
effectively gluing them together into a solid
mass. In time the entire shell is replaced
leaving rock in the exact shape of the
trilobite or animal. That is fossil formation
at work.
4th Step: Uplift
As the continental plates move around
the earth, crashing into each other,
mountains are formed. Former sea
floors are lifted up and become dry
land. This is exactly what has
happened to our trilobite in the picture
below. Now fossil formation is
complete but our trilobite is buried
under hundreds or even thousands of
feet of rock! Thanks to the
movement of the plates, (mountain
building or sea floors lifting up),
our trilobite or fossil will come
closer to the surface and nearer to
discovery by paleontologist.
Luckily nothing stays the same.
5th Step: Erosion at work
Fossil formation is revealed by
weathering and erosion. Wind,
rain, freeze and thaw, even
earthquakes will help force the
trilobite out of its burial ground and
out into the light. If he or she is
lucky enough, the trilobite will
reveal itself in time to be spotted by
a rock-hunter or fossil-digger. Who
knows? It could even be YOU!
QUESTIONS
1. What do you know about fossils? (WHAT
ARE FOSSILS)
•
2. What might be some ways that fossils are
formed?
•
3.How old do you think fossils are?
•https://www.youtube.com/watch?v=ClJ5lwl_w
M0&authuser=0
What is a fossil?
• A fossil is the
preserved remains
or traces of an
organism that lived
in the past
• Usually fossils are
more than 10,000
years old
What do fossils tell us about
Earth’s past?
• Fossils are clues
to:
– The diversity of
living things
throughout Earth’s
history
– Past climate and
surface changes
– Changes that have
occurred with
organisms over time
Who studies fossils?
• Paleontology is the
study of fossils
• Scientists who
study fossils are
called
paleontologists
How are fossils classified?
• Fossils are
classified by how
they are formed
• 6 Types of fossils:
–
–
–
–
–
–
Mold fossil
Cast fossil
Petrified fossil
Preserved fossil
Carbonized fossil
Trace fossil
The Fossil Record
• Millions of fossils have been collected
and studied from all over the world
• Provides evidence of the history of
life on Earth
• Shows that different groups of
organisms have changed over time
http://www.abc.net.au/beasts/fossilfun/burial/default.htm
QUESTIONS
• Explain what fossils reveal about extinct
species.
•
• How can fossils be used to tell us about the
environment during a certain time?
GRAPIC ORGANIZER
• NAME THAT FOSSIL
• BASED ON THE INFORMATION AND
PICTURE YOU HAVE, AS A GROUP
SEE IF YOU CAN PUT THE CORRECT
DEFINITION AND ILLUSTRATION IN
THE CORRECT FOSSIL COLUMN.
http:///wwww.youtube.comatch?v=3rkGu0BItKM
Mold Fossil
• Forms when:
– Sediments bury an
organism
– Sediments change
into rock by
pressure
– The organism
decays
– Leaves a cavity or
hollow in the shape
of the organism
Cast Fossil
• Forms when:
– A mold is filled with
sand or mud
– Sediments harden
into the shape of
the organism
Mold and Cast Fossils
• Most common form of
fossils
• Most fossils form
when sediment buries
a dead organism
• Organism most likely
lived in or near quiet
water (swamp, lake,
shallow sea)
Petrified Fossil
• Also called
permineralized
fossil
• Forms when:
minerals soak into
the buried remains,
replacing the
remains, and
changing them into
rock.
CLOSURE
• Compare two fossil types
•
• Of the three fossil types, Which do you
think are more commonly found and
why?
FALCON FOCUS
• Two scientists, Fred and Liz, were working at a dig site to
find fossils. They both had just gotten their degrees in
Geology and were very excited to start work.
• Fred had suspected that Liz wasn't who she said she was,
mostly because she messed up terms and almost seemed
to lack some basic skills in excavation and classification
of fossils. One day Liz was looking at a well-preserved
fossil when Fred walked in. He decided to test her and
asked, "What kind of rock is that preserved in?" She
answered back, "Igneous of course!" He then knew that
she didn't have a degree in Geology and told the boss
who, of course, fired her. What answer should she have
given? WHY?
EQ
• WHAT THINGS DO FOSSILS TELL
US ABOUT THE PAST?
GRAPIC ORGANIZER PART 2
• NAME THAT FOSSIL
• BASED ON THE INFORMATION AND
PICTURE YOU HAVE, AS A GROUP
SEE IF YOU CAN PUT THE CORRECT
DEFINITION AND ILLUSTRATION IN
THE CORRECT FOSSIL COLUMN.
http:///wwww.youtube.comatch?v=3rkGu0BItKM
Trace Fossils
• Forms when:
– Mud or sand
hardens to stone
where a footprint,
trail, or burrow of
an organism was
left behind
– http://www.youtube
.com/watch?v=9y7m
IJ1-Uh0
Dino Tracks
Carbonized Fossils
• Form when:
– Organisms or parts
are pressed
between layers of
soft mud or clay
– Mud or clay hardens
– Squeezes almost all
the decaying
organism away
– Leaves the carbon
imprint in the rock
Preserved Fossil
• Forms when:
– Entire organisms or
parts of organisms
are prevented from
decaying
– Trapped in rock,
ice, tar, or amber
QUESTIONS
• How might plants or animals be preserved in their true form
instead of in a cast or mold?
•
• What do you think is the benefit of a preserved organism over
JUST a cast or mold of the organism?
•
• Watch clip from Jurassic Park describing preserved fossils
•
• https://www.youtube.com/watch?v=iMsJe3TymqY
QUESTIONS
• What might preserved fossils add to the
study of the Earth's past the other fossils
would not?
•
• Why are carbonized fossils useful when
studying the past?
QUESTIONS
• CONNECT HOW THE FORMATION
OF SEDIMENTARY ROCK EFFECTS
THE FORMATION OF FOSSILS.
•
• What might happen to fossils when they
are exposed to heat and pressure within
the earth?
•
HOMEWORK
• STUDENTS WILL DRAW CARTOON STRIP
ABOUT THE FORMATION AND DISCOVERY
OF A FOSSIL
Falcon Focus
• List the Earth layers in order from the
least dense to more dense. (Include their
state of matter)
Essential Question:
• WHAT ENVIRONMENTAL FACTORS
CONTRIBUTE TO FORMING DIFFERENT
TYPES OF FOSSILS?
REBUS
INTRO
• Match the fossil type with the correct
environmental factors present when they
were formed
•
• What is the difference between cast and
mold fossils?
•
• Students will do a scavenger hunt to
identify the 6 types of fossils
• Students will complete the fossil lab by interacting with
the different types of fossils
•
• Which fossils do you think are probably most common
based on how they are formed?
•
• Which fossil type involves minerals in its formation?
•
HOMEWORK
• STUDY FOR QUIZ
FALCON FOCUS
– DURING THE SUBDUCTION ZONE,
WHICH CRUST SINKS AND WHY?
EQ
• WHY IS STUDYING FOSSILS IMPORTANT
TO OUR WORLD TODAY?
REBUS
• What might trace fossils reveal about organisms
that other fossils would not?
•
• How can trace fossils be used to learn about the
living conditions of organisms?
•
• Students will watch Bill Nye clip on Fossils and
write a reflection on which extinct species they
would bring back if they could and the effect it
would have on modern life in their notebooks
QUICK REVIEW
QUIZ TIME
Ticket out the Door
• Name the key words for each one of the
fossils.
• 1. Trace
• 2. Mold
• 3. Cast
• 4. Petrified
• 5. Carbonized
• 6. Preserved
Test Your Skills
Which of the following
is least likely to be
found as a fossil?
a.
b.
c.
d.
Clam shell
Shark tooth
Dinosaur bone
Jellyfish imprint
Test Your Skills
Fossils are usually
found in _______?
a.
b.
c.
d.
Desert land
Mud
Sedimentary rock
Rocks formed inside
volcanoes
Test Your Skills
Fossils of animals
found in the La
Brea tar pits are
examples of what
kind of fossils?
a.
b.
c.
d.
Carbon film
Mold fossil
Preserved remains
Petrified fossil
Test Your Skills
Marine fossils have been found in
exposed rock layers in South
Carolina. Which of the following
is the best interpretation of this
discovery?
A. Marine organisms evolved from
land-dwelling organisms.
B. Parts of South Carolina were
once covered by water.
C. These organisms could live both
in water and on land.
D. They were carried by humans to
South Carolina.
Test Your Skills
Select the correct letter for the choices that
are all definitely fossils.
A.
B.
C.
D.
Egyptian Mummy, Ancient Pottery, Worm
burrows in sandstone
Imprints of rain drops, Trilobite shells,
Mud cracks
Dinosaur tracks, Mammoth found in ice,
Seashells found in limestone
Stone Age tools, Giant shark teeth,
Seashells found on a beach
Test Your Skills
Using the choices below,
identify the fossils formed
by petrification.
A. Dinosaur tracks, Black
outline of a plant leaf
B. Rock-like wood, Rock-like
Brachiopod shell
C. Mud-filled shape of a
gastropod shell, Mammoth
droppings
D. Insect in amber, Hollow
cavity shaped like a trilobite
Review Check On Fossils
Mini-Lab Time
1.
2.
3.
4.
5.
Creating a mold and cast fossil
Creating a trace fossil
Creating a carbonized fossil
Creating a petrified fossil
Demonstrating a preserved fossil