1. Origins of Life Early Idea: Spontaneous Generation
The idea that non-living material can produce life—Life magically appears!
Examples
Meat produces maggots
Mud produces fish (mudskippers)
Grain produces mice

2. Origins of Life
Francesco Redi disproved the theory of spontaneous generation in 1668
Experiments with rotting meat

3. Origins of Life
Also during this time, scientists were just beginning to use microscopes…
They were able to see that microorganisms were EVERYWHERE!
Even though Redi was able to disprove the theory of spontaneous generation, many scientists thought that microorganisms arose spontaneously from a “vital force” in the air

4. Origins of Life Louis Pasteur
Disproved the spontaneous generation of microorganisms
Experiments with broth

5. Origins of Life
Pasteur’s experiments showed that microorganisms do not arise from the broth alone even in the presence of air
Biogenesis became the accepted theory about the origin of life
Biogenesis is the idea that living organisms only come from other living organisms

6. How Did Life Begin On Earth?
Currently, there is no way to know for certain how life began on Earth.
Scientists have developed theories about the origins of life, using the scientific method to test hypotheses about conditions on early Earth.
Only about 1% of all known species exist today
99% are extinct!

7. How Did Life Begin On Earth?
Early Earth
Very Hot
Meteorite Collisions
Volcanoes
Very little oxygen
Atmosphere made of H2O Vapor, CO2, Nitrogen gas, Methane & Ammonia

8. How Did Life Begin On Earth?
Ingredients for Life: Before life can occur, you need the molecules of life
1st: Formation of simple organic molecules
2nd: Organization into complex organic molecules
Proteins/Carbohydrates/Nucleic Acids/Lipids
So… How did this happen in such a harsh environment?

9. How Did Life Begin On Earth?
Alexander Oparin (1930’s)
Life began in the oceans
Sun, lightening & heat caused chemical reactions producing organic molecules
These molecules washed into the ocean forming primordial soup

10. How Did Life Begin On Earth?
Miller & Urey (1953)
Tested Oparin’s theory by simulating conditions on early Earth in a lab
Mixture of H2O vapor, ammonia, methane, and hydrogen gasses were zapped with electrodes
Cooled gasses condensed in flask
After a week, several kinds of amino acids, sugars, and other small organic molecules were present in the flask

11. How Did Life Begin On Earth?
The next steps in the origin of life were the formation of complex organic molecules and cells.
Sidney Fox – produced protocells by heating solutions of amino acids
Protocells – a large ordered structure, enclosed by a membrane, that carries out some life activities, such as growth and division.

12. The First True Cells
First forms of life were prokaryotes that likely evolved from protocells
Anaerobic Heterotrophs
Later, early prokaryotes evolved to be able to make their own food
These were similar to archaebacteria and used chemosynthesis to produce their food

13. The First Photosynthetic Prokaryotes
Likely the next kind of organisms to have evolved were:
Able to use sun to make glucose
Produced OXYGEN, which changed Earth’s atmosphere
Lightening + Oxygen = Ozone Layer formation

14. The First Eukaryotes The Endosymbionic Theory Lynn Margulis – 1960’s
Eukaryotes evolved from prokaryotes
Evolved b/c of symbiotic relationships between early prokaryotic bacteria (mitochondria & chloroplasts)

15. The Record Of Life
Paleontologists – scientists who study ancient life, often using fossil evidence
Uses fossils to determine look and characteristics of the organism, as well as the climate and geography of the area.
Fossils – evidence of an organism that lived long ago
typically found in sedimentary rock
compressed clay/sand/mud

16. The Record Of Life Different kinds of fossils: Trace Casts Imprints
Petrified
Molds
Amber
Frozen
Trace Fossil
Cast Fossil
Imprint Fossil
Mold Fossil
Amber Fossil
Frozen Fossil

17. The Record Of Life Fossil Aging
Relative Dating – The deeper the fossil, the older it is.
Radiometric Dating – Uses radioactive isotopes to determine specific ages of fossils.
Potassium-40: used for really old fossils
Carbon-14: used for fossils less than 50,000 years old

18. Geologic Time Scale Chronology, or calendar, of the Earth’s history.
Based on evidence from rocks
Organized according to living organisms of the time period
4 different eras

19. Time Line of Earth’s History
4.6 billion ybp – Earth forms
hot/volcanoes/meteors/ancient atmosphere
3.9 billion ybp – Earth cools
water vapor condenses. Millions of yrs of rainstorms create oceans
billion ybp – Precambrian Era
First organisms appear, photosynthesizing organisms add OXYGEN to atmosphere
3.5 billion ybp – unicellular prokaryotes
1.8 billion ybp – eukaryotic organisms develop
544 million ybp – multicellular eukaryotes (sponges & jellyfish)

20. Time Line of Earth’s History
540 million ybp – Paleozoic Era
Animals & plants appeared
500 million ybp – first vertebrates
430 million ybp – first land plants
390 million ybp – first amphibians
300 million ybp – first reptiles
250 million ybp – mass extinction

21. Time Line of Earth’s History
245 million ybp – Mesozoic Era
Age of the Dinosaurs
245 million ybp – Triassic Period
225 million ybp: first dinosaurs
210 million ybp: first mammals
208 million ybp – Jurassic Period
150 million ybp: first birds
144 million ybp – Cretaceous Period
135 million ybp: continents broke apart & began to drift
66 million ybp: mass extinction of dinosaurs

22. Time Line of Earth’s History
66 million ybp – Cenozoic Era
Era in which we now live
30 million ybp – Primates appear
200,000 ybp – Modern Humans Appear