1. Warm Up Evo 3
1.) How old is the Earth? 2.) During what Era did modern Humans evolve? 3.) The half life of Bismuth-214 is 20 minutes. If you started out with 100 molecules of Bismuth in your sample and walked away for 1 hour, how much Bismuth-214 would you expect to have left?

2. Section 14.2 Summary – pages 380-385
Origins: The Early Idea
In the past, the ideas that decaying meat produced maggots, mud produced fishes, and grain produced mice were reasonable explanations for what people observed occurring in their environment.
spontaneous generation—the idea that nonliving material can produce life.
Section 14.2 Summary – pages

3. Section 14.2 Summary – pages 380-385
Spontaneous generation is disproved
In 1668, an Italian physician, Francesco Redi, disproved a commonly held belief at the time—the idea that decaying meat produced maggots, which are immature flies.
Redi’s well-designed, controlled experiment successfully convinced many scientists that maggots, and probably most large organisms, did not arise by spontaneous generation
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4. Section 14.2 Summary – pages 380-385
Pasteur’s experiments
In the mid-1800s, Louis Pasteur designed an experiment that disproved the spontaneous generation of microorganisms.
Pasteur set up an experiment in which air, but no microorganisms, was allowed to contact a broth that contained nutrients.
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5. Section 14.2 Summary – pages 380-385
Pasteur’s experiments
The flask’s S-shaped neck allowed air to enter, but prevented microorganisms from entering the flask.
Each of Pasteur’s broth-filled flasks was boiled to kill all microorganisms.
Microorganisms soon grew in the broth, showing that they come from other microorganisms.
Pasteur tilted a flask, allowing the microorganisms to enter the broth.
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6. Section 14.2 Summary – pages 380-385
Simple organic molecules formed
In the 1930s, a Russian scientist, Alexander Oparin, hypothesized that life began in the oceans that formed on early Earth.
He suggested that energy from the sun, lightning, and Earth’s heat triggered chemical reactions to produce small organic molecules from the substances present in the atmosphere.
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7. Section 14.2 Summary – pages 380-385
Simple organic molecules formed
Then, rain probably washed the molecules into the oceans to form what is often called a primordial soup.
In 1953, two American scientists, Stanley Miller and Harold Urey, tested Oparin’s Hypothesis
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8. Section 14.2 Summary – pages 380-385
Simple organic molecules formed
Entry for hydrogen, methane, and ammonia gases
Electrode
High voltage source
Condenser for cooling
Boiling water
Solution of organic compounds
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9. Section 14.2 Summary – pages 380-385
The formation of protocells
The work of American biochemist Sidney Fox in showed how the first cells may have occurred.
Fox produced protocells by heating solutions of amino acids.
A protocell is a large, ordered structure, enclosed by a membrane, that carries out some life activities, such as growth and division.
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10. Section 14.2 Summary – pages 380-385
The Evolution of Cells
Fossils indicate that by about 3.4 billion years ago, photosynthetic prokaryotic cells existed on Earth.
But these were probably not the earliest cells.
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11. Section 14.2 Summary – pages 380-385
The first true cells
The first forms of life may have been:
prokaryotes that evolved from a protocell.
Anaerobic (no oxygen on Earth yet)
Heterotrophs, eating amino acids in oceans
Later evolved to do photosynthesis when food supplies became limited
These first autotrophs were probably similar to present-day archaebacteria.
Section 14.2 Summary – pages

12. The first true cells
Archaebacteria (ar kee bac TEER ee uh) are prokaryotic and live in harsh environments, such as deep-sea vents and hot springs.
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13. Section 14.2 Summary – pages 380-385
The endosymbiont theory
Complex eukaryotic cells probably evolved from prokaryotic cells.
The endosymbiont theory proposed by American biologist Lynn Margulis in the early 1960s, explains how eukaryotic cells may have arisen.
The endosymbiont theory proposes that eukaryotes evolved through a symbiotic relationship between ancient prokaryotes.
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14. Section 14.2 Summary – pages 380-385
The endosymbiont theory:
1. A prokaryote ingested some aerobic bacteria. The aerobes were protected and produced energy for the prokaryote.
3. Some primitive prokaryotes also ingested cyanobacteria, which contain photosynthetic pigments.
2. Over a long time, the aerobes become mitochondria, no longer able to live on their own.
4. The cyanobacteria become chloroplasts, no longer able to live on their own.
Cyanobacteria
Chloroplasts
Aerobic bacteria
Mitochondria
Plant cell
Prokaryote
Animal Cell
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15. Section 14.2 Summary – pages 380-385
The endosymbiont theory
Support for endosymbiont theory:
1.) chloroplasts and mitochondria have their own DNA that is different than the DNA in the host cell.
2.) both chloroplasts and mitochondria reproduce independently of the cells that contain them.
3.) we now find photosynthetic animals!
Section 14.2 Summary – pages