1. Fig. 2-CO, p. 40

2. Fig. 2-1, p. 41

3. Fig. 2-2, p. 42

4. Fig. 2-3, p. 43

5. A nebula (a large, diffuse gas cloud of gas and dust) contracts under gravity. As it contracts, the nebula heats, flattens, and spins faster, becoming a spinning disk of dust and gas. Star will be born in center. Planets will form in disk. Warm temperatures allow only metal/rock “seeds” to condense in the inner solar system. Hydrogen and helium remain gaseous, but other materials can condense into solid “seeds” for building planets. Cold temperatures allow “seeds” to contain abundant ice in outer solar system. Terrestrial planets are built from metal and rock. Solid “seeds” collide and stick together. Larger ones attract others with their gravity, growing bigger still. The seeds of gas giant planets grow large enough to attract hydrogen and helium gas, making them into giant, mostly gaseous planets; moons form in disks of dust and gas that surround the planets. Terrestrial planets remain in inner solar system. Gas giant planets remain in outer solar system. “Leftovers” from the formation process become asteroids (metal/rock) and comets (mostly ice). Not to scale

6. Fig. 2-4, p. 44

7. Fig. 2-5, p. 45

8. Fig. 2-6, p. 45

9. Fig. 2-7a, p. 46

10. Fig. 2-7b, p. 46

11. Lighter matter and silicates Iron

12. Fig. 2-7c, p. 46

13. Fig. 2-8, p. 46

14. Fig. 2-9, p. 47

15. Fig. 2-10a, p. 48

16. Fig. 2-10b, p. 48

17. Fig. 2-11, p. 49

18. 100 Methane, ammonia 75 Atmosphere unknown 50 Nitrogen Water Concentration of Atmospheric Gases (%) 25 Carbon dioxide Oxygen 0 4.5 4 3 2 1 Time (billions of years ago)

19. Fig. 2-12, p. 50

20. Fig. 2-13a, p. 50

21. Fig. 2-13b, p. 50

22. Fig. 2-14, p. 51

23. Fig. 2-15, p. 51

24. Billions of years ago 13 Big bang Billions of years ago 4.6 Earth forms 11 First gal axies form 4.2 Ocean forms Millions of years ago 3.8 Oldest dated rocks 800 3.6 First evidence of life Solar nebula begins to form 5.5 2 Oxygen revolution begins Millions of years ago 66 End of dinosaurs First fishes appear 510 4.6 50 First marine mammals Earth forms 0.8 Ocean and atmosphere reach steady state (as today) Pangaea breaks apart 210 End of dinosaurs Today 0 66 Today 3 Humans appear Today 3.5 Sun's output too low for liquid-water ocean 5 The sun swells, planets destroyed Billions of years in the future First animals arise

25. Box 2-1a/b, p. 52

26. Box 2-1c, p. 53

27. Box 2-1d, p. 53

28. Box 2-1e, p. 54

29. Box 2-1f, p. 54

30. Box 2-1g, p. 55

31. Box 2-1h, p. 55