Biogeological CyclesName______

Global Geography

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Answer the following questions in point form (for your notes – not to pass in).

Define each of the four spheres:

  • lithosphere: the Earth’s crust and materials (soil, rocks, minerals) that form it
  • hydrosphere: all the water on Earth
  • atmosphere: all of the gases in the air
  • biosphere: all life on Earth

Define nutrient cycle:

  • the processes that recycle key nutrients through the four spheres

What percentage of the world’s total carbon supply is involved in the carbon cycle, and where is the rest stored?

  • only 1% moves through the carbon cycle, the other 99% is stored in sedimentary rock or the oceans

What natural process removes carbon from the atmosphere?

  • carbon is removed from the atmosphere by photosynthesis

What are the three natural processes that return CO2 to the atmosphere?

  • carbon is returned to the atmosphere by volcanic activity, plant respiration and animal respiration

What human activities return CO2 to the atmosphere?

  • apart from respiration, humans return carbon to the air when they burn fossil fuels (combustion) or through industrial activity

Explain why burning tropical rainforests has two effects on increasing carbon dioxide levels in the air.

  • tropical rainforests remove CO2, so levels increase when the forest is gone…plus burning the waste material releases CO2

Explain why global warming is linked to carbon dioxide.

  • carbon dioxide allows light to enter to warm the Earth, but traps heat and slows its release

What percentage of our air is nitrogen?78%

Why is “free nitrogen” not part of living things?

  • Living things can only use nitrogen in the form of ammonia or nitrates

Describe the natural process for “fixing” free nitrogen into ammonia and nitrates:

  • bacteria on the roots of legumes (alfalfa, peas beans) convert nitrogen from the air into ammonia or nitrates

Using Figure 3.8, identify the second natural process where nitrogen “fixation” occurs.

  • blue-green algae in the oceans also fix nitrogen

Using Figure 3.8, what other process is used by humans to “fix” nitrogen?

  • humans fix nitrogen in industrial processes that produce fertilizer

Suggest at least three ways that the nitrogen cycle is similar to the carbon cycle. MANY ANSWERS POSSIBLE

  • only natural processes remove these nutrients from the air
  • both nutrients are essential for all life
  • both nutrients can be returned to the air by volcanic activity
  • both nutrients pass through all four spheres

Where does most of the oxygen in our atmosphere come from?

  • photosynthesis of algae in the oceans (90%)and other plants

*I feel the term respiration is misleading…only photosynthesis releases O2

Why are farmlands now almost as productive as forests?

  • advances in farming techniques (fertilizer, cultivation, crop selection and irrigation)

Refer to Figure 3.9. How is ozone in the upper atmosphere different from “normal” oxygen, O2?

  • ozone is made of 3 oxygen atoms, but “normal” oxygen has only 2