Question

12 how does the release of large amounts of phosphorus by humans cause problems?
the nitrogen cycle
for questions 13–15, circle the letter of the correct answer.
13 most of the nitrogen on earth is located in the
a biosphere.
b geosphere.
c atmosphere.
d hydrosphere.
14 which of the following crops increases the amount of usable nitrogen in soil?
a corn
b wheat
c legumes
d tomatoes
15 the haber - bosch process enabled people to
a fix nitrogen artificially.
b clean up nitrogen pollution.
c create natural nitrogen.
d acquire nitrogen from plants.
16 name two ways nitrogen can be fixed naturally for plant use.
17 what happens to nitrogen during the process of denitrification?
skill builder organize information
18 fill in the compare/contrast table with information about the different biogeochemical cycles.
carbon cycle phosphorus cycle nitrogen cycle

Explanation:

1. Excessive phosphorus release by humans can cause eutrophication in water - bodies. Phosphorus is a limiting nutrient in many ecosystems. When large amounts are added, it can lead to over - growth of algae and other aquatic plants, depleting oxygen levels and harming aquatic life.
2. Most of the nitrogen on Earth is in the atmosphere (about 78% of the atmosphere is nitrogen gas).
3. Legumes have symbiotic relationships with nitrogen - fixing bacteria in their root nodules, which convert atmospheric nitrogen into a form usable by plants, thus increasing soil nitrogen.
4. The Haber - Bosch process is an artificial nitrogen - fixing process that converts atmospheric nitrogen and hydrogen into ammonia.
5. Lightning and nitrogen - fixing bacteria in the soil or in symbiotic relationships with plants (like legumes) are two natural ways nitrogen is fixed for plant use.
6. During denitrification, nitrate (NO₃⁻) is converted back into nitrogen gas (N₂) or nitrous oxide (N₂O) by bacteria in anaerobic conditions, returning nitrogen to the atmosphere.
7. For the table, the carbon cycle involves processes like photosynthesis, respiration, decomposition, and combustion; the phosphorus cycle is mainly a sedimentary cycle with weathering, runoff, and uptake by plants; the nitrogen cycle has processes such as nitrogen fixation, nitrification, denitrification, and assimilation.

Answer:

1. Excessive phosphorus causes eutrophication in water - bodies, harming aquatic life.
2. C. atmosphere
3. C. legumes
4. A. fix nitrogen artificially
5. Lightning; nitrogen - fixing bacteria in soil or with legumes
6. Nitrate is converted into nitrogen gas or nitrous oxide and returned to the atmosphere.
7. Information about carbon, phosphorus, and nitrogen cycles can be filled in the table based on their respective processes (photosynthesis, respiration, weathering, nitrogen fixation etc.)