Nitrogen Cycle and Human Impact

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is a major source of phosphate found in waterways?

Agricultural runoff (correct)

Laundry detergents

Sulfur-oxidizing bacteria

Terrestrial environments

What is a unique characteristic of phosphorus in the ecological system?

It is a major element in the atmosphere

It is one of the most limiting elements (correct)

It is a major component of the hydrosphere

It is a reactive element in the lithosphere

What is the primary role of phosphorus in the human body?

Regulating body temperature

Maintaining a strong immune system

Supporting vertebrate skeletons (correct)

Energy transfer and genetic information

What is the primary pool of sulfur in terrestrial environments?

Soil Organic Matter (SOM) Signup and view all the answers

What is the result of aerobic biological transformations in the sulfur cycle?

Sulfides are converted to sulfate Signup and view all the answers

What is the role of sulfur-oxidizing bacteria in the sulfur cycle?

Converting sulfides to sulfate Signup and view all the answers

How many groups of sulfur-oxidizing bacteria are mentioned in the text?

5 Signup and view all the answers

What is the result of anaerobic biological transformations in the sulfur cycle?

Sulfates are converted to sulfides Signup and view all the answers

What is the process that converts atmospheric nitrogen into a usable form?

Nitrogen Fixation Signup and view all the answers

What type of organisms are primarily responsible for Nitrogen Mineralization?

Decomposers, such as bacteria and fungi Signup and view all the answers

What is the process by which nitrogen is converted from ammonia to nitrate?

Nitrification Signup and view all the answers

What happens to the nitrogen that is fixed by nitrogen-fixing bacteria?

It is incorporated into protein and other organic compounds Signup and view all the answers

What is the result of excess nitrogen fertilizer in aquatic ecosystems?

Nutrient over-enrichment Signup and view all the answers

What is the process by which nitrogen is converted from nitrate back into atmospheric nitrogen?

Denitrification Signup and view all the answers

What is the purpose of nitrogen-fixing bacteria in ecosystems?

To provide nitrogen to plants Signup and view all the answers

What is the impact of excess nitrogen in drinking water?

It can lead to cancer and respiratory distress Signup and view all the answers

What is the result of nitrogen fixation?

Breakage of N2 bonds Signup and view all the answers

What is the process called when oxygen is added to form nitrogen oxides?

Nitrification Signup and view all the answers

What is the process by which nitrogen is converted back into its atmospheric form?

Denitrification Signup and view all the answers

What is the term for the process of converting organic nitrogen into ammonia?

Ammonification Signup and view all the answers

What is the term for the process by which plants take in nitrogen from the soil?

Assimilation Signup and view all the answers

What is the role of soils in the nitrogen cycle?

Soils are the source of nitrogen for plants Signup and view all the answers

What is the result of human activities on the phosphorus cycle?

A change in the rate of phosphorus cycling Signup and view all the answers

What is unique about the phosphorus cycle compared to other biogeochemical cycles?

It does not involve a gas phase Signup and view all the answers

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