1. The History of Life
Chapter 17

2. 17-1 The Fossil Record
What is the name for a scientist who studies fossils?
Fossil Record provides evidence of the history life on Earth.
Infer structure of organisms
What they ate
Environments they lived in
Fossils are found in specific layers of rock.
Able to date the age of ancient organisms.

3. Fossil Evidence
Identify and compare anatomical structures between fossils and living organisms.
Age of a fossil is determined by two techniques.
1. Relative Dating
2. Radioactive Dating

4. Relative Dating
Compares fossils with others found in various layers of rock.
Oldest layers on bottom
Index fossils
Used for comparison
Found in specific layers of rock in different
locations.

5. Radioactive Dating Radioactive decay to determine age of fossils.
Decay is measured as HALF-LIFE
the time for half of the radioactive atoms in a sample to decay

6. Radioactive Dating
Different radioactive elements have different half-lives.
Carbon 12  most common and does not decay
Carbon 14  radioactive
Has half-life of 5730 Years
More C-12 compared to C-14 = older fossil

7. Carbon-14 Decay

8. Geologic Time Scale Precambrian Time  Eras  Periods
Represents evolutionary time.
Precambrian Time 
Eras 
Periods
Cenozoic – Age of
Mammals
65 mya to present

9. 17-2 Earth’s Early History
Birth of planet took place over 100 million years
Collisions with other large objects
Produced tremendous amount of heat
How did the first organic molecules form?
Miller and Urey Experiment

10. Origins of Earth and Early Life
periment+Animation&Form=VQFRVP#view=detail&mid=CDF A CDF A

11. Question of the DAY
Radioactive Uranium-232 has a half-life of approximately 70 years. The Chernobyl Nuclear Power Plant Disaster in released high levels of radiation into nearby surrounding areas including the town of Pripyat.
What year would see a reduction in radiation to 25% of the original level of uranium-232?

12. 17-3 Evolution of Multicellular Life
Precambrian Time- 90% of Earth’s history
Life only existed in the seas
Simple anaerobic life  photosynthetic life  aerobic life
Prokaryotes  Eukaryotes  Multicellular organisms
Do not write anything down from the next slides!
Key points will be highlighted for you!

13. Paleozoic Era Carboniferous Period – reptiles and giant insects
Cambrian Period – Cambrian Explosion
Invertebrates, brachiopods, arthropods (trilobites)
Devonian Period – Plants adapt to drier areas
Insects
Age of Fishes – jaws, bony skeletons, scaled bodies
SHARKS!!!
First land animals – amphibians
Carboniferous Period – reptiles and giant insects
plant remains  coal
Mass Extinction – 95% of life extinct

14. Mesozoic Era Dominance of dinosaurs and flowering plants
Triassic Period – Age of Reptiles
225 mya  first dinosaurs
First mammals very small
Jurassic Period – Dinosaurs ruled Earth
Archaeopteryx appeared – first birds
Fossils show skulls/teeth of dinos but body and feathers of birds
Cretaceous Period – T. rex and flying reptiles
Flowering plants produced seeds enclosed in fruit
EXTINCTION EVENT

15. Cenozoic Era Quaternary Period – Ice Ages Ocean levels drop 100 meters
Age of Mammals
Mammals evolve to live in different environments
Tertiary Period – Earth warm and mild
Whales and dolphins evolve
Grasses provide food source for grazing mammals
Quaternary Period – Ice Ages
Ocean levels drop 100 meters
20,000 years ago – climate warms
Mammals such as bats, cattle, mammoths common
200,000 years ago – first fossils of Homo sapiens in Africa

16. NOVA The Missing Link http://www.youtube.com/watch?v=GOKW_7KajCU
How does information presented to you in the video clip provide evidence of evolution?

17. 17-4 Patterns of Evolution
What is macroevolution?
1. Extinction
Most researchers look for a single massive event – Asteroid striking Earth at Chicxulub Crater, Mexico
Extinction of dinosaurs
Ecosystems collapse due to natural factors (earthquakes, volcanoes)
Organisms still able to compete
Food webs destroyed Disrupts energy flow

18. Adaptive Radiation
adaptive radiation: multiple species evolve from a single species
also known as divergent evolution
Darwin’s Finches

19. Convergent Evolution
convergent evolution: different species evolve to have similar appearances and behaviors

20. Coevolution
Process in which two species evolve in response to changes in each other over time
Plant adaptation = animal adaptation

21. Punctuated Equilibrium vs Gradualism
punctuated equilibrium: involves long periods of stability that are interrupted by episodes of rapid change
gradualism: evolution occurs slow and steady over a long period of time