1. Life’s Origin and Early Evolution
Chapter 20

2. 20.1 In the Beginning . . .
Knowledge of modern ___________________ and ___________________ are the basis for scientific ___________________ about early events in Earth’s history

3. Ongoing Star Formation
The Eagle ______________, photographed by the Hubble space telescope

4. Early Earth

5. Stanley Miller’s Experiments

6. 20.2 How Did Cells Emerge?
We will never know for sure how the first ___________________ came to be, but we can investigate the possible steps on the road to ___________________

7. Possible Origins of Complex Organic Compounds
Clay templates on _________________ flats; iron-sulfide rocks at hydrothermal vents on the ___________________ floor

8. Models for Protocells
_______________________________ vesicles and ___________________ -coated clay

9. formation of protein–RNA systems, evolution of DNA
living cells
membrane-bound proto cells
self-replicating system enclosed in a selectively permeable, protective lipid sphere
enzymes and other proteins
DNA
RNA
formation of protein–RNA systems, evolution of DNA
formation of lipid spheres
Figure 20.6
Laboratory-formed models for protocells that may have preceded the emergence of cells. (a) Selectively permeable vesicles with an outer membrane of proteins were formed by heating amino acids, then wetting the resulting protein chains. (b) RNA-coated clay (stained red) enclosed in a simple membrane composed of fatty acids and alcohols (green). Mineral-rich clay promotes the assembly of such vesicle-like forms and catalyzes the formation of RNA strands from free nucleotides. (c) One hypothesis for steps that led from lifeless chemicals to living cells.
spontaneous formation of lipids, carbohydrates, amino acids, proteins, nucleotides under abiotic conditions
Fig. 20-6c, p. 321

10. Fossil Prokaryotic Cells

11. The Rise of Eukaryotes
Oldest eukaryotic fossils: __________________ years

12. Origins of Nucleus, ER, and Golgi Body
The ___________________ and ____________ may have arisen through modification of infoldings of ___________________

13. Evidence of Endosymbiosis

14. 20.5 Time Line for Life’s Origin and Evolution

15. Lessons of Chile’s Atacama Desert
What we learn about life on Earth informs our ideas about the possibility of life ___________________

16. Major Events in the History of Life