1. The Age of Earth
Ch 19.2
Biology

2. State Standard:
8e. Students know how to analyze fossil evidence with regard to biological diversity, episodic speciation, and mass extinction.

3. Objectives: What is the fossil record?
What information does the fossil record provide?
What is the geologic time scale and how is it organized?

4. A. Fossils and Ancient Life
The fossil record provides evidence about the history of life on Earth.
It provides evidence for:
How different groups of organisms have changed over time
The geographical distribution of organisms
Timelines - when they lived helps to chronicle Earth’s biodiversity
99% of all species that have ever lived on Earth have become extinct, which means the species died out.

5. B. The Fossil Record
Fossils form when the remains of the organism is preserved.
Organisms or their parts are rapidly buried in sedimentary rock.

6. B. The Fossil Record
2. Index fossils are easily recognized and lived for a very short time. They live in specific layers so we can find them in different geographic locations and date the layer.
3. Paleontologists determine the ages of fossils using 2 techniques:
Relative Dating
Radioactive Dating

7. C. Dating Methods
Relative Dating – age is determined by comparing its placement with that of fossils in other layers of rock.
2. Radioactive Dating – calculating the age of a sample based on the amount of remaining radioactive isotopes it contains.

8. D. Geologic Time Scale
Scientists use divisions of this scale to represent evolutionary time.
Precambrian time covers 88% of Earth’s beginnings.
Since then, the basic divisions of the geologic time scale are eras and periods.
Eras are divided into Periods.
Mass extinctions are used to mark the division of geologic time.
Large extinctions divide eras, while smaller scale extinctions mark divisions between periods.

9. Review: What happens after an extinction?
D. Geologic Time Scale
Recent
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
Era
Period
Time
(millions of years ago)
290 – 245
363–290
410–363
440–410
505–440
544–505
650–544
Vendian
1.8–present
65–1.8
145–65
208–145
245–208
Quarternary
Tertiary
Cretaceous
Jurassic
Triassic
Oldest
Speciation can occur, biodiversity can result, niches and opportunities open up for organisms who may not have been as well adapted before the extinction occurred….
Thought: Extinctions occur and leave traces from which we determine geologic time.
Review: What happens after an extinction?

10. Geologic Time Scale:  Compares Era time Shows 
Era/Period Divisions and Events

11. Objectives: What is the fossil record?
The fossilized remains of living things buried in earths layers
What information does the fossil record provide?
Timelines, changes in species over time, biodiversity, speciation, and graphical locations of living things
What is the geologic time scale and how is it organized?
The timeline of earth’s living things. Divided into eras and periods, which were determined (marked) by mass extinctions.