1. Bellringer 11/21/13
What is a fossil?

2. Topic: Fossil Evidence of Evolution
EQ: How do fossils form?

3. Take a look!

4. Evidence supporting evolution
Fossil record
shows change over time
Anatomical record
comparing body structures
homology & vestigial structures
embryology & development
Molecular record
comparing protein & DNA sequences
Artificial selection
human caused evolution

5. Fossil record Layers of rock contain fossils
new layers cover older ones
creates a record over time
fossils show a series of organisms have lived on Earth
over a long period of time

6. What is a fossil?
The preserved remains or traces of an organism that lived in the past
Can be formed from a bone, tooth, shell, or other part of an organism

7. How do fossils form?
Most fossils form when organisms that die become buried in sediments (particles of soil and rock)

8. Fossil Formation
Only the hard parts of an organism (bones, shells, and teeth) generally form fossils because the soft parts are broken down too quickly.
Most fossils are formed when an organism is quickly buried by sediments.

9. Types of Fossils Mold – impression of an organism in a rock.
Cast – a fossil copy of an organism in a rock.
Trace Fossil – preserved evidence of the activity of an organism.
Original Material – Tissues are preserved in ice, tar, and amber.

10. What are petrified fossils?
A fossil formed when minerals replace all or part of an organism

11. How are mold and casts related to fossils?
Mold – A type of fossil formed when shell or other hard part of an organism dissolves, leaving an empty space in the shape of the part
Cast – A type of fossil that forms when a mold becomes filled in with minerals that then harden

12. What are trace fossils?
Preserved evidence of the activity of an organism.

13. How else are remains preserved?
Original Remain
Entire organisms, such as the huge elephant-like mammoths have been preserved in ice
Bones and teeth have been preserved in tar pits
Insects and other organisms can become stuck in sticky sap. The sap then hardens forming amber

14. How do you determine a fossil’s age?
Relative dating
Radioactive dating

15. What is relative dating?
A technique used to determine which of two fossils is older
Can only be used when the rock layers have been preserved in their original sequence

16. What is radioactive dating?
A technique used to determine the actual age of a fossil
The rocks that fossils are found near contain radioactive elements, scientists use these elements to determine decay (half-life)

17. What are radioactive elements?
Unstable elements that decay, or break down, into different elements

18. What is half-life?
The time it takes for half of the atoms in a sample to decay
Scientists can compare the amount of a radioactive element in a sample to the amount of the element into which it breaks down

19. Fossils help scientists piece together information about Earth’s past
What do fossils reveal?
Fossils help scientists piece together information about Earth’s past
The millions of fossils that scientists have collected are called the fossil record

20. What is the Geological Time Scale?
Scientist have used the ages of rocks and fossils to create a “calendar” of Earth’s history that spans 4.6 billion years
Scientists have divided this large time period into smaller units called eras and periods sometimes called the Geologic Time Scale

22. What are the theories on how fast does Evolution Occur?
Gradualism – Evolution occurs slowly but steadily
Punctuated Equilibrium – Species evolve during short periods of rapid change

23. When is a species extinct?
A species is extinct if no members of that species are still alive