Chapter #4 The Earth's Geological Record and the Earliest Life.


1. According to the age of the rocks that were deposited during the time of the dinosaurs, when did the dinosaurs exist on the Earth? What is this time period called? (page 55)

2. How far back in time from the present do fossils of species with hard parts such as bones and shells date? (page 56) What is the name given to this era?

3. Describe the process by which scientists are able to determine the age of rocks. (Page 57)

4. How old are the oldest rocks that have ever been found on Earth? (page 58)

5. The Earth's history following its formation through 4.0 b.y.a. can be divided into what three major eons? (page 59)

6. What events do the large peaks in Figure 4.4 signify? What are some possible causes of these events? When did the most significant of these events occur? (page 60)

7. How are the findings in the "Burgess shale" of British Columbia significant to changing the belief that life on Earth originated during the Cambrian period. How do life forms found in "Burgess shale" differ from those of the Cambrian period? (page 61)

8. How old does evidence exist for multi-cellular life that contains carbon? (page 61)

9. What is the name given to the period from 2.5 b.y.a. to the end of the pre-Cambrian period 570 m.y.a. ? (page 61)

10. Describe the difference in atmospheric composition of CO2 and O2 that appears across the (somewhat arbitrary) boundary between the Archaean and the Proterozoic periods. What other geological process appears to have underwent a dramatic increase around the time of this boundary? (page 61)

11. What mineral evidence is there to support the increased oxygen levels occurring approximately 2 b.y.a. ? (page 62 - 63)

12. What life forms and biological process are thought to have produced the increase quantities of oxygen? (page 63)

13. Describe the process by which the amount of C02 in the atmosphere is controlled by the ocean and volcanism. (page 63)

14. How does the rate of formation of carbonates in the ocean affect the atmospheric concentrations of C02? Describe how ocean and atmosphere's temperature act as a feedback mechanism for the rate of carbonate formation. (page 63- 65)

15. What are the three lines of evidence that tell us about the earliest know life on Earth? (page 66 &endash; 69)

16. By examining the amount of different isotopes in an object it is possible to estimate its age and whether or not biological activity is taking place. Describe in detail how the amounts of isotopes are used to make these determinations. (57, 58 and 69)