24 Questions
What is a major source of phosphate found in waterways?
Agricultural runoff
What is a unique characteristic of phosphorus in the ecological system?
It is one of the most limiting elements
What is the primary role of phosphorus in the human body?
Supporting vertebrate skeletons
What is the primary pool of sulfur in terrestrial environments?
Soil Organic Matter (SOM)
What is the result of aerobic biological transformations in the sulfur cycle?
Sulfides are converted to sulfate
What is the role of sulfur-oxidizing bacteria in the sulfur cycle?
Converting sulfides to sulfate
How many groups of sulfur-oxidizing bacteria are mentioned in the text?
5
What is the result of anaerobic biological transformations in the sulfur cycle?
Sulfates are converted to sulfides
What is the process that converts atmospheric nitrogen into a usable form?
Nitrogen Fixation
What type of organisms are primarily responsible for Nitrogen Mineralization?
Decomposers, such as bacteria and fungi
What is the process by which nitrogen is converted from ammonia to nitrate?
Nitrification
What happens to the nitrogen that is fixed by nitrogen-fixing bacteria?
It is incorporated into protein and other organic compounds
What is the result of excess nitrogen fertilizer in aquatic ecosystems?
Nutrient over-enrichment
What is the process by which nitrogen is converted from nitrate back into atmospheric nitrogen?
Denitrification
What is the purpose of nitrogen-fixing bacteria in ecosystems?
To provide nitrogen to plants
What is the impact of excess nitrogen in drinking water?
It can lead to cancer and respiratory distress
What is the result of nitrogen fixation?
Breakage of N2 bonds
What is the process called when oxygen is added to form nitrogen oxides?
Nitrification
What is the process by which nitrogen is converted back into its atmospheric form?
Denitrification
What is the term for the process of converting organic nitrogen into ammonia?
Ammonification
What is the term for the process by which plants take in nitrogen from the soil?
Assimilation
What is the role of soils in the nitrogen cycle?
Soils are the source of nitrogen for plants
What is the result of human activities on the phosphorus cycle?
A change in the rate of phosphorus cycling
What is unique about the phosphorus cycle compared to other biogeochemical cycles?
It does not involve a gas phase
Study Notes
Nitrogen Cycle
- Humans impact the nitrogen cycle by releasing nitrogen forms into the atmosphere, contributing to:
- Smog (nitric oxide, NO)
- Greenhouse gases (nitrous oxide, N2O)
- Acid Rain (nitrogen oxides)
- Key processes in the nitrogen cycle:
- Nitrogen fixation (breaking N2 bonds)
- Nitrification (adding oxygen to form nitrogen oxides)
- Denitrification (converting nitrogen back to atmospheric N2)
- Ammonification (mineralization/waste conversion by decomposers)
- Assimilation (uptake by producers)
Phosphorus Cycle
- Definition: The phosphorus cycle describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere.
- Phosphorus cycle processes:
- Rocks release phosphates through weathering
- Plants absorb phosphate ions from soil
- Phosphate is transferred to animals through the food chain
- Animals release phosphate through waste
- Decomposition returns phosphate to the soil
- Phosphate is reused by plants or incorporated into rocks
- Human impact on the phosphorus cycle:
- Cutting tropical rainforests
- Using agricultural fertilizers
- Facts about phosphorus:
- Element number 15
- Does not include a gas phase
- One of the most limiting elements in ecological systems
- Involved in energy transfer and genetic information in DNA
- Highly reactive, often found in combined forms
- Important for vertebrates, 80% found in teeth and bones
Sulfur Cycle
- Major pools of sulfur:
- Lithosphere (largest amounts)
- Soil Organic Matter (SOM) in terrestrial environments
- Biological transformations:
- Aerobic sulfur-oxidizing bacteria convert sulfides to sulfate
- Anaerobic sulfate-reducing bacteria convert sulfate to sulfides
- Microbial sulfur transformations:
- 5 groups of sulfur-oxidizing bacteria (e.g., Green and Purple Sulfur bacteria)
- Human impact on the sulfur cycle:
- Burning fossil fuels
- Using synthetic nitrogen fertilizers
- Cultivating legumes
Nitrogen Fixation and Human Impact
- Nitrogen fixation: breaking atmospheric nitrogen into usable forms (NH3 or NH4+)
- Human activities that fix nitrogen:
- Burning fossil fuels
- Using synthetic nitrogen fertilizers
- Cultivating legumes
- Nitrification: adding oxygen to nitrogen to form nitrite and nitrate
- Denitrification: removing nitrogen from ecosystems and converting it back to atmospheric N2
- Human impact on ecosystems:
- Excess nitrogen from fertilizers can contaminate surface water and groundwater
- Excess nitrogen in drinking water can lead to cancer and respiratory distress
- Excess nitrogen in surface waters can lead to:
- Nutrient over-enrichment
- Fish kills
- Harmful algal blooms
- Species shifts in aquatic and land ecosystems
Learn about the nitrogen cycle, its processes, and its impact on the environment, including the formation of smog, greenhouse gases, and acid rain.
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