Sample Quiz 5 answers

1-B

2-D

3-E

4-C

5-C

6-B

7-C

8-D

9-C

10-A

11-C

12-D

13-D

14-inputs to atmosphere total 6.3+2.2= 8.5GtC, of which the atmosphere is retaining 3.3 GtC and the oceans are taking up 2.4 GtC. Thus a total of 3.3+2.4=5.7GtC is accounted for of the 8.5GtC going in, but that means 8.5-5.7=2.8GtC is unaccounted for as part of the so-called “missing sink”. Around 2000, the prevailing wisdom was that it was going into temperate N. Hemisphere forests (N. America and China), or into the southern Ocean, but now recent evidence suggests much of it may be going into tropic rain forests related to CO₂ fertilization or secondary regrowth in areas that were deforested.

15-

Example 1: Photosynthesis is the main component of primary production, and it requires the C from CO2 as a primary nutrient, but productivity also requires other nutrients such as N. Thus primary production is a major sink for N and C in their respective biogeochemical cycles.

Example 2: when fossil fuels are combusted they contain lots of C, but they also contain some N. Both will go into the atmosphere when the fuel is burned

16- No. During the full glacial 20,000 years ago, a continental ice sheet covered much of N. America as far south as St. Louis. Therefore, the remaining forest was compressed into latitudes below this

17-Yes. 7-8 GtC is currently entering the atmosphere from f-f burning each year, but around 200 GtC per year enter the atmosphere from respiration+decomposition on land +evasion from the ocean. Thus f-f inputs are less than 5% of the natural inputs. So, why then are we concerned with it?

18- Mexico has a broader base, with a greater fraction of individual in the pre-reproductive age classes (primed for rapid population growth). The US distribution is more uniform with reduced fraction of individuals in pre-reproductive age classes and a higher fraction in post-reproductive age classes.

19-productivity/oxygen production/biodiversity/genetic storehouse/tropical pharmacy/C storage

20- forest to agriculture; farmland to highways; etc.

21- birth rate, death rate, immigration/emigration (known as dispersal), sex ratio, age distribution

22. consult your notes from 4/13 and the 2 essays you were required to read.

23-20 years (use “rule of 70”)