Biogeochemical Cycles

The Carbon Cycle

1. Name two ways that carbon (usually in the form of CO2) enters the atmosphere.

  • burning of fossil fuels for energy and electricity

  • respiration from plants and animals

2. What process uses CO2 from the atmosphere?

  • Photosynthesis

3. What organisms carry out this process?

  • plants, algae, and bacteria

4. Wastes and dead organisms must be broken down in order for their components to be used again. What organisms in the cycle carry out this process?

  • DECOMPOSITION

    • carried out by fungi, bacteria, worms

5. What would happen if decomposition did not occur?

  • CO2 would not be recycled into the atmosphere

    • would not allow the cycle to continue, CO2 must be returned so that the cycle continues

  • there would be waste, and the world would be unlivable

6. Not all dead organisms are acted on by decomposers. Instead of being immediately recycled, the carbon from some organisms is kept in a type of long-term storage, or carbon sink. Answer the questions below about this long-term storage.
a. List three materials that contain this stored carbon

  1. Coal

  2. Oil

  3. Peat

b. What is the collective term for these three materials

Fossil Fuels

c. How do modern humans use these carbon stores?

  • Humans burn fossil fuels for energy and electricity

    • everyday use, dependence on the burning of fossil fuels

  • Production in Industry

d. How does our use of these carbon stores affect the amount of CO2 in the atmosphere

  • we are overusing and burning too much fossil fuels leading to an increase in CO2 concentration levels

  • High levels of CO2 in our environment are one of the leading causes of Climate Change and Global Warming

7. What is another way human activity is increasing the amount of atmospheric CO2 and what are the potential global effects of these changes in CO2 levels?

  • Deforestation - Causing the excess release of CO2 of plants into the environment

  • Climate change is caused by biodiversity being affected

    • Loss of forests= a loss of habitat = loss of species → an unbalanced ecosystem, extinction

  • Sea Level Rise- Ice and snow are melting leading to the sea level rising and continuing to increase the rate

Model 2: The Nitrogen Cycle

8. In what ways is N2 gas removed from the atmosphere

  • Through Nitrogen Fixation

    • when nitrogen is taken from the atmosphere and it is “fixed” by adding hydrogens or hydrogens to make it into more usable compounds for plants (ex. ammonia, ammonium)

9. Name 3 types of bacteria involved in the nitrogen cycle

  1. Nitrogen-fixing bacteria

  2. Nitrifying bacteria

  3. Decomposing fungi

10. By what process are animal wastes, urine, and dead organisms converted to other nitrogen-containing compounds?

  • Deamination

    • converting into ammonia or ammonium compounds

11. What do the denitrifying bacteria do?

  • they convert the nitrates into atmospheric nitrogen (N2)

  • Turning the nitrogen oxides back into nitrogen gas using nitrate reductase

Model 3: The Water Cycle

12. What is the largest reservoir of water on earth?

  • the ocean

13. Name two ways in which water is converted to vapour.

  1. Evaporation

  2. Transpiration

14. How does water return to the oceans from the land?

  • surface runoff (sideward)

  • percolation (downward)

15. Rain, sleet and snow are examples of what?

  • Precipitation

16. If the air contains high levels of pollutants what effect might this have on water quality?

  • quality of water will lower and become worse, quality of water won’t be as clean or healthy

    • water won’t be safe or healthy to drink, can lead to disease or illness of human beings and any organisms

  • affect on the life of biodiversity, plants on land or in water will be destructed

  • Pollution of water (streams, lakes, oceans)

17. like the other cycles, the water cycle is a “closed system.” What does that say about the importance of keeping the water on earth free from pollution?

  • we cannot replace our water if it’s polluted

  • we recycle our water, meaning we must take care of it or else it will become unusable

  • once any source of water is polluted, the whole water system is affected

Which process(es) of the water cycle – precipitation, evaporation, condensation, run-off, percolation or transpiration might contribute to the addition of pollutants to rivers, lakes and oceans? Why?

  • precipitation and runoff

    • they bring the polluted water from land back into the ocean → our source of water

  • precipitation takes water and drops it (in the form of rain and snow) into other parts of the world, risking this spread and pollution of water elsewhere

  • runoff collects the pollutants from underground or on land and pollutes the ocean / our water supply

To continually use the same area of land for agriculture, some farmers apply fertilizers to improve the level of nitrates in the soil. An alternative to intensive use of fertilizer is to plow the roots of the leguminous plants back into the soil and leave the area unplanted for a season. Why would a farmer plow this type of plant roots back into the soil and what would be the benefit of turning over the soil and leaving the old plant roots?

  • A farmer would plow this type of plant root since these legumes convert nitrogen oxides back into atmospheric nitrogen (N2 gas)

    • → for plant use

  • Leaving the old plant roots can allow the nitrates to be replaced

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