Chapter 25 Pre-Class Assignment

Over the last several decades, what have researchers discovered about atmospheric CO2 levels?

They have increased.

The _____ cycle deals with geological processes and carbon reservoirs, some of which have been built up (or take place) over a period of millennia. In contrast, the _____ cycle involves biological processes that are carried out on a daily and/or seasonal basis.

long-term carbon; short-term carbon

Recall that in the northern hemisphere, atmospheric CO2 levels are highest in early spring and lowest in early fall. What accounts for this seasonal fluctuation in atmospheric CO2 levels?

photosynthesis

The rate of respiration _____ throughout the year.

remains more or less constant

Photosynthesis _____ the atmosphere, whereas respiration _____ the atmosphere.

removes CO2 from; introduces CO2 to

Photosynthesis and respiration both play a major role in the _____ carbon cycle, and can affect atmospheric CO2 levels on a seasonal or annual basis.

short-term

Which of the following processes is responsible for the changes scientists observed in atmospheric concentrations of 12C, 13C, and 14C over the last 200 years?

the burning of fossil fuels

Which of the following processes INCREASES the amount of CO2 in the atmosphere? (Select all that apply.)

volcanic eruptions respiration

Photosynthesis and respiration affect atmospheric CO2 levels on a _____ timescale, whereas volcanic eruptions affect atmospheric CO2 levels on a _____ timescale.

yearly; century