1. THE HISTORY OF LIFE
SC STANDARD B-5 Students will demonstrate an understanding of the basis of evolution

2. CN: page 54 notebook
Topic: The History of Life
EQ: What are the 4 important patterns of macroevolution?

3. FOSSILS Paleontologist: scientists who study fossils
Fossil Record: information about past life, including the structure of organisms, what they ate, in what environment they lived, & order in which they lived
FOSSILS

4. This species lived 7700 years ago
The fossil record provides evidence about the history of life on Earth.
It also shows how different groups of organisms, have changed over time.
Extinct: term used to describe a species that has died out
This species lived years ago

5. Lists of Extinct Animals
Lists of Extinct Animals

6. Formation of any fossil depends on a precise combination of conditions
How Fossils Form

7. Why is the fossil record described as an incomplete record of life’s history?
Evolution of Whales

8. Interpreting Fossil Evidence
Erosive forces cut through sedimentary rock wearing away the youngest layers first, exposing any fossils embedded in them.
Interpreting Fossil Evidence

9. Paleontologists reconstruct extinct species from few fossil bits to entire bodies. They look for similarities & differences with living organisms

10. In relative dating, the age of a fossil is determined by comparing its placement in the layers of sedimentary rock
Relative Dating

11. Relative Dating

12. Index fossils: distinctive fossil used to compare relative ages of fossils

13. half-life: is the length of time required for 50% of the sample of radioisotopes to decay
radioactive dating: calculating the age of a fossil based on the remaining radioactive isotopes
assumption is: the amount of C-14, for example, has remained constant
C-14 can only be used for fossils <60,000 yrs because of its short half-life (not enough specimen left to measure)
Radioactive Dating

14. Radioactive Decay of K-40

15. Geologic Time Scale

16. Geologic evidence suggests that Earth formed over millions of years
Process began ~4.6 billion years ago
This process involved multiple collisions and temperatures so high anything solid melted
While melted substances arranged themselves by densities
Less dense substances floated to surface and gradually cooled forming Earth’s crust
Formation of Earth

17. Earth’s Early Atmosphere
Hydrogen & Nitrogen formed early atmosphere
hydrogen cyanide
carbon dioxide
carbon monoxide
sulfide
water
~ 4 billion years ago Earth had cooled enough to allow 1st solid rocks to form
still being bombarded by comets, asteroids, etc.
too hot for water to exist in liquid form
Earth’s Early Atmosphere

18. Oceans covered most of planet
~ 3.8 billion years ago Earth’s surface cooled down enough for water to stay in liquid phase
Oceans covered most of planet
Oceans brown due to dissolved iron
Oldest sedimentary rock deposited in water

19. The 1st Organic Molecules
Miller & Urey tried to reproduce conditions on early Earth in a lab:
CH4 , H2 , NH3 , H2O in a flask to represent early atmosphere
passed electric shocks through it to simulate lightening
Over a few days several amino acids began to accumulate
Results suggests how mixtures of organic cpds necessary for life could have arisen from simpler cpds present on primitive Earth
The 1st Organic Molecules

20. Proposes that eukaryotic cells arose from living communities formed by prokaryotic organisms
Mitochondria
Chloroplasts
Endosymbiotic Theory