1. Ferrous iron is ________?

. iron 2 and dissolves readily in water

2. 10. What are the 2 current carbon sinks?

carbonate formation and oxygenic photosynthesis

3. To the nearest billion, how long did the earth exist prior to the existence of an atmosphere in which molecular oxygen was plentiful?

3

4. Which 13C (‰) value represents thermogenic methane?

-40 ‰

5. The Goldilocks Hypothesis describes how earth's temperature has remained relatively constant since its formation as greenhouse gas concentration has __________ and solar luminosity has _____________ over time.

decreased; increased

6. ___________ is the main mechanism by which populations adapt and evolve.

natural selection

7. The background rate of extinction is approximately which of the following?

1 out of every 1 million species goes extinct each year.

8. Which mass extinction event resulted in an estimated loss of 90-95% of all marine species? A. the current sixth mass extinction due to human activity

Permian extinction

9. A temperate forest _________________.

. contains deciduous trees that lose their leaves in the winter