Fossils
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Printed: November 20, 2013
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C ONCEPT
Concept 1. Fossils
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Fossils
Lesson 11.1: True or False
Name___________________ Class______________ Date________
Write true if the statement is true or false if the statement is false.
_____ 1. People have been discovering fossils for thousands of years.
_____ 2. In ancient times, fossils inspired legends of mythical creatures.
_____ 3. Fossilization is a fairly common occurrence.
_____ 4. There is virtually no fossil record of organisms that lacked hard parts such as bones or shells.
_____ 5. A dead organism is less likely to become a fossil if it is buried by sediments.
_____ 6. Because of difficulties of preservation, only a few thousand fossils have ever been discovered.
_____ 7. The least common type of fossilization is the preservation of soft tissues.
_____ 8. Some insects have been perfectly preserved in amber.
_____ 9. Fossils of marine organisms found on land show that the land was once covered by a sea.
_____ 10. Rocks containing the same index fossils are about the same age.
Lesson 11.1: Critical Reading
Name___________________ Class______________ Date________
Read this passage based on the text and answer the questions that follow.
How Fossils Form
A fossil is any preserved remains or traces of once-living organisms. Fossils include body fossils, which are
fossilized remains of body parts, and trace fossils, which include burrows, tracks, feces, or other traces left by
an organism. Collections of fossils that are found together are known as fossil assemblages.
The process of a once-living organism or its traces becoming a fossil is called fossilization. It most often occurs
when the remains or traces are buried by sediments and then gradually change to rock. Fossilization is very rare.
Only a tiny percentage of the organisms that have ever lived have become fossils. Usually, it is only the hard parts
of organisms that are fossilized. The fossil record consists almost entirely of the shells, bones, or other hard parts of
animals. Mammal teeth are much more resistant than bones, so a large portion of the mammal fossil record consists
of teeth. The shells of marine organisms are also common. Organisms that lack hard parts, from bacteria to jellyfish,
rarely become fossils.
Quick burial is almost always necessary for an organism to be fossilized because most decay and fragmentation
occur when remains are exposed at the surface. Marine animals that die near a river delta may be buried rapidly
by river sediments. A storm at sea may shift sediment on the ocean floor, covering a body and helping to preserve
its skeletal remains. In general, quick burial is rare on land, so fossils of land organisms are less common than
fossils of marine organisms. However, land organisms are sometimes buried by mudslides, volcanic ash, or sand in
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a sandstorm. They may also be buried by mud in lakes, swamps, or bogs. Rarely, they may be buried by tar in tar
pits or the ice of glaciers.
Questions
1. What is a fossil? Distinguish between body fossils and trace fossils.
2. Why is fossilization rare?
3. What factors make fossilization more likely?
Lesson 11.1: Multiple Choice
Name___________________ Class______________ Date________
Circle the letter of the correct choice.
1. “Dragon bones” found in China 2000 years ago were probably
a.
b.
c.
d.
unusually shaped rocks.
dinosaur fossils.
bones of lizards.
pillow lava.
2. Coprolites are
a.
b.
c.
d.
fossilized feces.
extinct sea organisms.
minerals found in replacement fossils.
any fossilized traces of once-living organisms.
3. Which statement about fossils is false?
a.
b.
c.
d.
Only a tiny percentage of organisms becomes fossils.
Soft-bodied organisms are the least likely to become fossils.
Quick burial is almost always essential for remains to become fossils.
Land organisms are more likely to become fossils than marine organisms.
4. Complete preservation is possible if an organism is buried in
a.
b.
c.
d.
tar.
mud.
tree sap.
any of the above
5. Petrified wood forms because of
a.
b.
c.
d.
compression.
replacement.
permineralization.
none of the above
6. Compression is most common for fossils of
a.
b.
c.
d.
leaves.
teeth.
bones.
shells.
7. Fossils can provide clues about
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a.
b.
c.
d.
Concept 1. Fossils
past climates.
plate tectonics.
extinct species.
all of the above
Lesson 11.1: Matching
Name___________________ Class______________ Date________
Match each definition with the correct term.
Definitions
_____ 1. most common method of fossilization
_____ 2. space in rock left behind when an organism or part of an organism decays
_____ 3. hardened ancient tree sap
_____ 4. any preserved remains or traces of an ancient organism
_____ 5. type of fossil that forms when a mold fills in with sediments
_____ 6. common, widespread fossil that can be used to identify the ages of rocks
_____ 7. any process by which fossils form
Terms
a. permineralization
b. cast
c. fossilization
d. mold
e. amber
f. fossil
g. index fossil
Lesson 11.1: Fill in the Blank
Name___________________ Class______________ Date________
Fill in the blank with the appropriate term.
1.
2.
3.
4.
5.
6.
7.
The preserved remains of an organism’s body parts is called a(n) __________ fossil.
A preserved burrow, track, or other evidence of an organism’s life is called a(n) __________ fossil.
__________ is the process in which water deposits minerals within the remains of a buried organism.
A(n) __________ of organic remains forms when the remains are compressed by high pressure.
The best form of evidence about the history of life on Earth is __________.
Organisms that make good index fossils are widespread and existed for a(n) __________ period of time.
For a fossil that forms by __________, the original bone or shell dissolves and is replaced by different
minerals.
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Lesson 11.1: Critical Writing
Name___________________ Class______________ Date________
Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.
Compare and contrast two different methods of fossilization.
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