1. The Fossil Record
Sect. 6.2 and 6.3

2. Evidence of evolution
Fossils, patterns of early development, and similar body structures all provide evidence that organisms have changed over time.

3. Evidence of Evolution Homologous Body Structures
Turtle
Homologous Body Structures
Structures that have different mature forms but develop from the same embryonic tissues
e.g. Wing of bat, human arm, leg of turtle
Alligator
Bird

4. Homologous Body Structures

5. Vestigial Organs traces of homologous organs in other species
Organ that serves no useful function
e.g. Appendix

6. Evidence of Evolution Similarities in Embryology
In their early stages of development, chickens, turtles and rats look similar, providing evidence that they shared a common ancestry.

7. Primate Bone structure

8. Embryological development

11. Evidence of Evolution Geographic Distribution of Living Species
Similar animals in different locations were the product of similar lines of descent

13. The Fossil Record
Most fossils form when organisms that die become buried in sediments.

14. Fossil Formation SG

15. KEY CONCEPT Specific environmental conditions are necessary in order for fossils to form.

16. Fossils can form in several ways.
Permineralization occurs when minerals carried by water are deposited around a hard structure.

17. A natural mold forms when flowing water removes all of the original tissue, leaving an impression.
The cast is the copy of the shape of the organism that makes the mold.

18. Trace fossils record the activity of an organism.

19. Amber-preserved fossils are organisms that become trapped in tree resin that hardens after the tree is buried.

20. Preserved remains form when an entire organism becomes encased in material such as ice.

21. Specific conditions are needed for fossilization.
Only a tiny percentage of living things became fossils.

22. Relative vs. Absolute Dating

23. Relative Dating Can determine a fossil’s relative age
Performed by estimating fossil age compared with that of other fossils
Drawbacks – provides no info about age in years

24. Radiometric dating provides an accurate way to estimate the age of fossils.
Relative dating estimates the time during which an organism lived.
It compares the placement of fossils in layers of rock.
Scientists infer the order in which species existed.

25. Absolute dating Also known as radioactive dating
Can determine the absolute age in numbers
Is performed by radioactive dating – based on the amount of remaining radioactive isotopes remain
Drawbacks - part of the fossil is destroyed during the test

26. Index fossils are another tool to determine the age of rock layers.
Index fossils can provide the relative age of a rock layer.
existed only during specific spans of time
occurred in large geographic areas
Index fossils include fusulinids and trilobites.

27. history based on major past events.
KEY CONCEPT The geologic time scale divides Earth’s
history based on major past events.

28. The geologic time scale organizes Earth’s history.
The history of Earth is represented in the geologic time scale.
100
250
550
1000
2000
PRECAMBRIAN TIME
Cyanobacteria
This time span makes up the vast majority of Earth’s history. It includes the oldest known rocks and fossils, the origin of eukaryotes, and the oldest animal fossils.

29. Eras last tens to hundreds of millions of years.
consist of two or more periods
three eras: Cenozoic, Mesozoic, Paleozoic

31. Periods last tens of millions of years.
most commonly used units of time on time scale
associated with rock systems.
Epochs last several million years.