1. 1 Explain What does Miller and Urey’s experiment tell us about the organic compounds needed for life Predict You just read that life arose from nonlife billions of years ago. Could life arise from nonlife today- why 2 Review What does the endosymbiontic theory propose Explain According to this theory how did mitochondria evolve

2. Ch 19 History of Life
19.3 Earth’s Early History

3. Early Earth 4.6 billion years old Started off much hotter
Evidence of high methane, carbon dioxide, ammonia, water vapor, and hydrogen concentrations
Went through multiple heating and cooling cycles
High heat often helps chemical reactions.

4. The First Organic Molecules
1953 Miller and Urey
Tried to replicate early Earth conditions
Produced 21 amino acids.

5. Miller and Urey’s ideas on the composition of the early atmosphere were incorrect
New experiments based on current ideas of the early atmosphere have produced similar results.

6. Microspheres Tiny bubble of large organic molecules Not cells
Have selectively permeable membranes
Can store and release energy.

7. “RNA World” Hypothesis
RNA evolved before DNA
Small chunks could form from simple molecules
RNA sequences help DNA replicate
RNA sequences process messenger RNA
RNA sequences catalyze chemical reactions
Some can grow and replicate on their own.

8. “RNA World” Hypothesis

9. Early atmosphere similar to a volcano.

10. Production of Free Oxygen
2.2 billion years ago photosynthetic bacteria were common
Produced oxygen combined with iron in the oceans
Iron oxide sank to ocean floor and formed large deposits (is the iron we mine today)
Oceans changed color from brown to blue-green.

11. Oxygen gas began to accumulate in the atmosphere
Ozone layer formed
Skies turned blue
Oxygen concentrations continued to rise.

12. Endosymbiotic Theory
Prokaryotic cells entered ancestral eukaryotes and began living inside them.

13. Mitochondria evolved from endosymbiotic prokaryotes that were able to use oxygen to generate energy-rich ATP.

14. Chloroplasts evolved from endosymbiotic prokaryotes that had the ability to photosynthesize.

15. Modern Evidence
Mitochondria and chloroplasts have ribosomes whose size and structure closely resemble those of bacteria
Mitochondria and chloroplasts, like bacteria, reproduce by binary fission when cell undergoes mitosis.

16. Significance of Sexual Reproduction
Sped up evolutionary change because sexual reproduction increases genetic variation.

17. Which gas is most abundant in Earth’s atmosphere today
Which gas is most abundant in Earth’s atmosphere today? What percent of that gas may have been present in the early atmosphere
Which gas was probably most abundant in the early atmosphere
Where did the water in today’s oceans probably come from