Section 2.2 – The Carbon Cycle - Check your understanding questions
Page 51 - Questions 1 to 7
1. What three elements are carbohydrates made from?
Carbohydrates are made from carbon, oxygen, and hydrogen.
2. Make a table with two columns. In the first column list the processes that add CO2 to the atmosphere. In the
second, list things that help remove CO2 from the atmosphere.
See table below:
CO2 is added to the atmosphere by:
CO2 is removed from the atmosphere by
- Burning wood
- Planting trees
- Driving cars, buses, trucks, trains
- Burning coal
- Heating buildings with oil or gas
- Using a fossil-fuelled barbecue
3. What are the reactants and products in the equation for photosynthesis?
The reactants of photosynthesis (what goes into the equation) are water, energy, and carbon dioxide. The
products of photosynthesis are carbohydrates and oxygen.
4. What are the reactants and products in the equation for cellular respiration?
The reactants of cellular respiration are carbohydrates, and oxygen. The products of cellular respiration are
water, carbon dioxide, and energy (ATP).
5. What actions could you take yourself to help reduce the CO2 levels in the atmosphere?
To reduce carbon dioxide levels in the atmosphere you can:
o Plant trees or other types of producers
o Walk or bike to school instead of taking the bus or getting a ride
o Carpool
o Recycle or reusing items rather than throwing away products and buying new ones.
6. The carbon dioxide levels in Biosphere II (described at the beginning of the chapter) decreased each day and
increased each night. Suggest an explanation for this pattern. Why do carbon dioxide levels not fluctuate in the
same way in Earth’s atmosphere?
The carbon dioxide levels in Biosphere II decreased each day because the level of photosynthesis increased
during day-light (light reactions), making use of available carbon dioxide. At night, when photosynthesis is less
efficient, carbon dioxide increased. Carbon dioxide levels do not fluctuate in the same way in the Earth’s
atmosphere because the entire Earth is never completely in darkness. Also, carbon dioxide is absorbed by many
more plants and released by many more animals than could exist in Biosphere II.
7. Explain how extensive deforestation could increase the global temperature.
Extensive deforestation releases massive quantaties of carbon dioxide into the atmosphere, more it the trees
are burned to clear the land. Average global temperatures can increase because the extra carbon dioxide traps
heat energy from the Sun (like a thermal blanket over the Earth).