Name:
Date:
4.2 Fossil Reading
Period:
Intro
Fossils tell scientists a lot about the world around us. Much of our
knowledge of the past comes from fossils, as well as our knowledge
about the future. Without fossils, concepts like evolution and
continental drift would not have as much support.
Intro
1. What do fossils tell scientists?
To begin with fossils are preserved remains of dead animals. There
are 4 main types of fossils: mold, cast, trace, and body fossils. This
article will discuss mold and cast fossils, the type of fossils found in
sedimentary rocks. These fossils provide scientists with a lot of
information about Earth’s history.
3. What are fossils?
Mold fossils
Mold fossils are fossils that show the shape of the overall animal
body. Mold fossils are usually hollow. Mold fossils form when dirt
buries an animal quickly and turn to rock. The animal inside gives
the rock around it the same shape. Then the animal decomposes
(bacteria breakdown the animal) until the animal disappears. All
that is left is a hollow rock in the shape of the animal it surrounded.
Cast fossils:
Cast fossils are rock fossils that filled the mold fossils. The first steps
of cast fossilization are the same as mold fossilization. The animal
dies and is quickly buried by dirt sediments. The dirt sediments
become solid rock and surround the dead animal. The dead animal
then decomposes (bacteria breakdown the animal) and there is a
hollow rock mold in the shape of the animal (this is a mold fossil).
Water with minerals fills the hollow mold. The minerals crystalize
and form a different rock in the shape of the animal inside the mold.
Bones frequently are the last things to decompose; so many cast
fossils are rocks in the shape of bones.
2. What concepts are supported by fossil evidence?
4. What are the four types of fossils?
Mold Fossils
5. What do mold fossils show?
6. How are mold fossils made?
Cast Fossils
7. What is similar between cast fossils and mold fossils?
8. What is the final step of cast fossil formation that makes them different from
mold fossils?
Information cast and mold fossils give scientists.
Both case fossils and mold fossil tell scientists about the body of the
animal. They give scientists an idea of the size and shape of the body
as well as how the bodies move.
Information cast and mold fossils give scientis:
9. What do cast and mold fossils tell scientsis?
Fossil evidence about evolution
Fossils give scientists strong evidence for evolution. When scientists
look at fossils, they notice that most of the animals on earth today
are not found under ground as fossils. Most of the fossils found are
different from the animals found on earth today. This leads
scientists to believe that some of the animals found as fossils
evolved to become the animals on earth today (some animals went
extinct and never evolved). There are enough fossils of some lines
evolution that scientists can see each step of the animal’s evolution.
Fossil evidence about evolution
10. What do scientists notice about the fossils underneath the ground and the
animals on earth?
This picture shows fossils
evidence of the evolution
of the whale. You can see
the evolution of the
whale in each fossil step
as parts of its body
evolved to be better
adapted to the
environment.
The fossil on the bottom
was found in the oldest
rocks closest to the
earth’s core. The whale
on top was found in the
newest rocks closest to
the earth’s surface.
11. What does the picture to the left show and how do the fossils prove
evolution? **** 3 sentences******
12. Which fossils are the oldest?
Classwork to Homework
Name:
Date:
4.2 Fossil Reading
Fossil evidence of continental drift
Fossils give scientist great evidence of continental drift, the slow
movement of continents around our globe. According the geological
(rock) and fossil evidence, our planet used to have one big super
continent, Pangea. Through continental drift, the super continent
Pangea broke into smaller continents that spread around the globe.
Fossils provide evidence for continental drift because fossils of the
same, land-walking animal, are found on two separate continents.
These animals had no way of crossing the large ocean of our planet
today. The animals died while Pangea was a super continent, buried,
and then turned to fossils. Then the continents separated through
continental drift, separating the fossils. The only way fossils of the
same land animal could be found on two different continents is if the
continents with fossils inside
When the
continents were
together in
Pangea, the
dinosaurs were
able to walk from
one continent to
the other. The
animals died, and
were buried. Then
the continents
separated,
separating their
fossils. Now
fossils of the same
animal are found
on continents very
far apart
Relative Dating
Scientists are able to tell how old the earth is by looking at
sedimentary rocks and other rocks in layers. Sedimentary rocks
form layers. The layers on the bottom are the oldest and the layers
on top are the youngest.
Period:
Fossil evidence of continental drift
13. What is continental drift?
14. What was Pangaea?
15. What did continental drift do to Pangaea?
16. Why are million year old fossils of land walking animals found on different
continents separated by large oceans? ****3 sentences*****
17. What does the picture on the left show? ****3 sentences******
Relative dating
18. How do scientists use sedimentary rocks for relative dating?
Fossil evidence of changing environments
Scientists get their knowledge about the environment in the past
through fossils they find in sedimentary rocks. The scientists can
figure out hold old a fossil is by looking at how deep the fossil is
buried and what layer of rock they found the fossil in. The deeper
the fossil, the older the fossil. The closer to the surface the fossil, the
younger the fossil. By looking at the fossil in a certain layer of rock,
they can tell what the environment used to be like at that time.
Fossil Evidence of changing environments
19. How can scientists tell how old a fossil is?
Conclusion examples scientists draw from fossils
In some parts of California, scientists have found fossils of fish.
California today is above ground today, but scientists concluded that
California must have been under water at some time in Earth’s
history if there are fish fossil trapped in the rocks. Scientists can
also learn about the weather of the past by looking at the fossils of
the animals in the sedimentary rock. Scientists know the latest iceage lasted from 110,000 years ago to 12,000 years ago because they
find fossils of wooly mammoths, saber tooth tigers, and other ice-age
animals in rocks that age. Scientists can also tell if a cold
environment once was warmer. In Antarctica, the coldest part of
planet, are fossils of reptiles that lived in warm environments. This
means that Antarctica must not have always been in the very cold
South Pole and must have been warm at some point in Earth’s
history.
Conclusion Examples scientists draw from fossils
21. What do scientists conclude when they find fossils of fish in California?
20. How do scientists learn about the environment in the past?
22. How do scientists know the ice age lasted from 110,000 to 12,000 years
ago?
23. How do scientists know Antarctica must have been a warm environment at
some point in earth’s history?
Classwork to Homework
Name:
Date:
4.2 Fossil Reading
Period:
Classwork to Homework