1. C 14- The History of Life Pp

2. Contents
14-1 The Record of Life
14-2 The Origin of Life

3. 14-1 The Record of Life
Early earth probably hot with colliding meteorites & radioactive minerals
By 4.4 BYA cooled enough for water to condense & lightening storms

4. History in Rocks Oldest rocks 3.9BY
Fossils offer clues to extinct life
95% species extinct
Paleontologists study ancient life, climate, & geography

5. Fossil Formation
Organisms are buried in sand, mud or clay & compressed & hardened into fossils.

6. Relative Dating
Top layers are most recent while deeper layers are older.

7. Radiometric Dating
Uses radioactive isotopes & half-life to determine age of rock or other organic matter

8. A Trip Through Geologic Time
Geologic Time Scale
Divided into 4 large sections between mass extinctions
Earth formation 4.6BYA

9. Precambrian Life Resembled modern cyanobacteria
Stromatolites show existence of photosynthetic organisms early on
First prokaryotic life; later eukaryotic

10. Diversity During Paleozoic
Cambrian explosion brought teeming ocean life
Fishes with backbones, ferns & seeded plants appeared
Amphibians & reptiles appear

11. Life in the Mesozoic Geologic changes
Early mammals appear during this age of reptiles
Birds evolve
Mass extinction of 2/3 species 65 MYA

12. Changes During Mesozoic
Continental drift
Supercontinent broke up & drifted
Plate tectonics explains how the plates move
Affects climate change

13. The Cenozoic Era Age of mammals Primate appear
Modern humans appear 200,000YA

14. 14-2 The Origin of Life Early ideas
Spontaneous generation- nonliving things produce life
Francesco Redi disproved this

15. Pasteur’s Experiments
Louis Pasteur used a crook neck flask to boil a nutrient broth. Air could get in but microorganisms could not.
Biogenesis became accepted in biology after that.

16. The Origin of Life Modern Ideas
Simple organic molecules formed, then more complex molecules like protein, carbohydrates & nucleic acids
Alexander Oparin hypothesized life began in the ocean

17. The Origin of Life
Stanley Miller & Harold Urey (1953) tested Oparin’s idea by simulating early conditions on Earth in the lab.
Amino acids, sugar & other small organic molecules were produced

18. Formation of Protocells
Stanley Fox 1992
Large ordered structure with a membrane that carries out some life activities such as growth and division

19. The Evolution of Cells Anaerobic prokaryotes Heterotrophs
Autotrophs evolved
Archaebacteria prokaryotic extremophiles

20. Photosynthesizing Prokaryotes
Release oxygen from water
Concentration of oxygen in atmosphere increases
Aerobes evolve
Ozone layer formed & allowing eukaryotes to evolve

21. Endosymbiont Theory Proposed by Lynn Margulis in 1960s
Eukaryotes evolved through a symbiotic relationship between prokaryotes
Chloroplasts & mitochondria have ribosomes