6-1 notes fossils & evolution chapter 6, lesson 1

6-1 NotesFossils & Evolution

Chapter 6, Lesson 1

Evidence for Evolution• Evolution (the transformation over a long

period of time from one species into another) is a fact.

Evidence for Evolution• Evolution accurately and scientifically

explains facts observed in the world.

Evidence for Evolution• Evolution is a theory just like the sun-

centered system of Copernicus and Galileo is also a theory. It took over 200 years for people to accept it, but we now know it is true.

What Are Fossils?• Fossils are the naturally preserved remains,

imprints, or traces of organisms that lived long ago.

What Are Fossils?• Includes bones, shells, and footprints.

• Microfossils can only be seen under a microscope.

What Are Fossils?• They determine:

• the relationships among organisms• the approximate times when life first appeared

on Earth• when organisms became extinct

What Are Fossils?

• A paleontologist is a scientist who studies fossils.

How Are Fossils Formed?

• Decomposition (breaking down into substances that can be used by other organisms) is part of an organism’s life cycle.

How Are Fossils Formed?

• For an organism to become a fossil, it must be protected from decomposers, scavengers, and environmental factors.

Permineralization• When substances inside the tiny spaces of

dead organisms decompose, water seeps into the empty spaces and deposits minerals, and preserves them.

• This process, permineralization, forms a strong, rock-like fossil.

Petrified Fossil

Replacement• Only the hard parts of an organism are

replaced by minerals in replacement.

• Only the shape of the original organism remains.

Carbonization• When a dead organism is quickly buried

under conditions without oxygen, the elements of the living tissue are removed, leaving behind just the element Carbon.

• A thin, usually black, carbon film remains and is compressed by sediment, preserving the image of the organism on a rock.

Molds and Casts• With mold and cast fossils, no parts of the

original organism remain.

• Molds are imprints from an organism, such as a shell or the skin of an animal.

• A mold looks like a hollow impression of the organism.

Cast Mold

Molds and Casts• A cast is created when molds fill in with

sediment that hardens into rock.

• A cast looks like a stone 3D version of the organism.

Cast Mold

Original Material• Organisms preserved in materials such as

amber, tar, and ice are called original material fossils.

• They are rare and provide much information because none of the hard or soft structures have been altered or replaced.

Original Material• The 3 types are tar, amber (sap), and ice.

Tar Amber (sap) Ice

What Do Fossils Tell Us?• Much of the evidence for evolutionary

relationships comes from fossils.

What Do Fossils Tell Us?

• Scientists also study fossils to understand some processes and rates of evolution.

What Do Fossils Tell Us?

• Fossils provide a record of different organisms that lived in the past.

Relative Fossil Ages• Generally, younger fossils are in shallow

sedimentary rock layers and older fossils are in deeper layers.

Relative Fossil Ages• Fossils can be compared by their age

relative to each other (relative age) and the changes to species can be documented.

Species and Environmental Changes

• The fossil record is a timeline showing all the known fossils and their placements in rock formations.

Species and Environmental Changes

• The fossil record is evidence of the evolution of plants and animals, and their extinction.

Species and Environmental Changes

• There are not always “transitional fossils” - a fossil that gives us information about a transition from one species to another.

Species and Environmental Changes

Species and Environmental Changes

• Not EVERYTHING gets fossilized, and many fossils are destroyed because of plate tectonics.

• This causes gaps in the fossil record.

Species and Environmental Changes

It’s NOT like there is a video camera recording EVERYTHING.

It’s more like a still camera taking snapshots.

Species and Environmental Changes

• Not a SINGLE fossil is in the wrong place and the wrong time.

There are no rabbit fossils in the Precambrian time.

If we did find rabbit fossils in the Precambrian time, we could disprove evolution.

Species and Environmental Changes

• Fossils provide evidence of how life and environmental conditions have changed throughout time.

Species and Environmental Changes

• Scientists use fossils to determine how organisms lived, what they ate, and what kind of environment they lived in.

1. What describes the deposit of minerals into the tiny spaces that have decomposed in an organism?

A permineralization

B decomposition

C replacement

D molds

6.1 Fossils and Evolution

1. A

2. B

3. C

4. D

2. What describes the preservation of the impression of an organism if no parts of the organism remain?

A carbonization

B replacement

C molds or casts

D original material

6.1 Fossils and Evolution

1. A

2. B

3. C

4. D

3. What are the most commonly found fossils?

A original material

B hard structures

C soft structures

D footprints

6.1 Fossils and Evolution

1. A

2. B

3. C

4. D

4. What does a paleontologist study?

A DNA

B classification of organisms

C fossils

D embryos

1. A

2. B

3. C

4. D

5. What does the depth of a fossil in the rock layer tell us about the fossil?

A how old it is

B how it died

C how it evolved

D how it lived

1. A

2. B

3. C

4. D