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 FormationIn 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.

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.

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.

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!

QUESTIONS1. 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_wM0&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=9y7mIJ1-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 SkillsWhich of the

following is least likely to be found as a fossil?

a. Clam shellb. Shark toothc. Dinosaur boned. Jellyfish imprint

Test Your Skills

Fossils are usually found in _______?

a. Desert landb. Mudc. Sedimentary

rockd. 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. Carbon filmb. Mold fossilc. Preserved

remainsd. Petrified fossil

Test Your SkillsMarine 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 SkillsSelect the correct letter for the choices

that are all definitely fossils. A.     Egyptian Mummy, Ancient Pottery,

Worm burrows in sandstoneB.   Imprints of rain drops, Trilobite shells,

Mud cracksC.   Dinosaur tracks, Mammoth found in

ice, Seashells found in limestone

D.   Stone Age tools, Giant shark teeth, Seashells found on a beach

Test Your SkillsUsing the choices below,

identify the fossils formed by petrification.

 A. Dinosaur tracks, Black

outline of a plant leafB. Rock-like wood, Rock-like

Brachiopod shellC. 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 Time1. Creating a mold and cast fossil2. Creating a trace fossil3. Creating a carbonized fossil4. Creating a petrified fossil5. Demonstrating a preserved fossil