The Carbon and Nitrogen Cycles Quiz

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Questions and Answers

How does tree removal impact the hydrologic cycle?

It enhances groundwater recharge.

It can lead to increased runoff and decreased transpiration. (correct)

It decreases evaporation rates.

It increases water retention in the soil.

Which of the following processes releases carbon into the atmosphere?

Respiration (correct)

Burial and sedimentation

Photosynthesis

Carbon sequestration

What role does photosynthesis play in the carbon cycle?

It pulls carbon from the atmosphere to create organic matter. (correct)

It converts organic carbon into fossil fuels.

It releases carbon into the atmosphere.

It facilitates the exchange of CO2 between oceans and the atmosphere.

What is a long-term outcome of burial and sedimentation in the carbon cycle?

Long-term sequestration of carbon in geological formations. Signup and view all the answers

Which transformation of carbon occurs during the extraction and combustion of fossil fuels?

Release of organic carbon as CO2. Signup and view all the answers

What is the main process through which atmospheric nitrogen is converted into forms usable by producers?

Nitrogen fixation Signup and view all the answers

What is the sequence of conversions in the nitrification process?

NH4+ → NO2- → NO3- Signup and view all the answers

What product results from denitrification that ultimately re-enters the atmosphere?

Nitrogen gas Signup and view all the answers

Which process involves the breakdown of waste into ammonia and inorganic compounds?

Mineralization Signup and view all the answers

Which organisms are primarily responsible for the process of nitrification?

Prokaryotes Signup and view all the answers

Which of the following human activities has a significant impact on the nitrogen cycle?

Use of fertilizers Signup and view all the answers

What is the primary form in which phosphorus exists in ecosystems?

Phosphate (PO43-) Signup and view all the answers

Which abiotic process can convert atmospheric nitrogen into usable forms?

Lightning Signup and view all the answers

Which of the following forms of nitrogen is produced during biosynthesis by producers?

Ammonium Signup and view all the answers

Which of these is a major source of phosphate in the phosphorus cycle?

Phosphate rocks (e.g., Ca(H2PO4)2) Signup and view all the answers

What process describes the increase in productivity in aquatic ecosystems due to phosphorus influx from human activities?

Cultural eutrophication Signup and view all the answers

How do plants primarily uptake phosphorus in terrestrial ecosystems?

By absorbing phosphate from the soil Signup and view all the answers

What happens to excess phosphate (PO43-) in terrestrial ecosystems?

It is removed via runoff and leaching Signup and view all the answers

What causes phosphorus to precipitate and become sediment in well-oxygenated aquatic ecosystems?

Binding with calcium or iron Signup and view all the answers

What is one of the key reservoirs for phosphorus in the ecosystem?

Hydrosphere Signup and view all the answers

Which of the following processes releases phosphates into aquatic systems from terrestrial ecosystems?

Soil erosion Signup and view all the answers

Which organic materials are primarily leached out of organic matter during decomposition?

Organic salts and sugars Signup and view all the answers

What role do large detritivores play in decomposition?

They macerate organic matter into small pieces to increase surface area. Signup and view all the answers

Which factor has the least effect on the rate of decomposition?

Wind speed Signup and view all the answers

In which environment is the rate of decomposition typically the fastest?

Tropical regions Signup and view all the answers

What portion of biomass does dead plant matter typically represent in temperate hardwood forests?

5% Signup and view all the answers

What is the primary source of nutrients in terrestrial ecosystems?

Organic matter in the soil Signup and view all the answers

What process involves the physical and chemical alteration of rock material near the Earth's surface?

Weathering Signup and view all the answers

Which of the following nutrients can be obtained from the atmosphere in terrestrial ecosystems?

Nitrogen Signup and view all the answers

Which factor is NOT mentioned as influencing the rate of weathering?

Wind speed Signup and view all the answers

How is the rate of weathering commonly estimated in a watershed?

By analyzing nutrient movement Signup and view all the answers

Which of the following processes contributes to nutrient recycling in forests?

Decomposition by fungi Signup and view all the answers

What is one method to measure nutrient inputs and outputs in an ecosystem?

Assessing watershed nutrient balance Signup and view all the answers

Which of the following best describes the outcome of nutrient leaching in terrestrial ecosystems?

Lowers nutrient availability Signup and view all the answers

Study Notes

The Carbon Cycle

Carbon moves within the cycles of Earth's systems (hydrosphere, atmosphere, biosphere, lithosphere).
Six major transformations influence this movement: photosynthesis, respiration, exchange, burial and sedimentation, extraction, and combustion.
Photosynthesis removes CO2 from the atmosphere to make sugars.
Respiration releases carbon to the atmosphere as CO2 and CH4.
CO2 can be exchanged between aquatic ecosystems and the atmosphere, with little net transfer over time.
Burial and sedimentation can lock carbon away for millions of years.
Extraction and combustion release organic carbon into the atmosphere as CO2.

Human Impact on the Carbon Cycle

Human activities, particularly extraction and combustion, have caused a significant increase in carbon levels.
The current concentration of CO2 is approximately 35% higher than the peak concentration in the past 400,000 years.

Nitrogen Cycles

Nitrogen is an important component of amino acids and nucleic acids, and it is abundant in the atmosphere.
Reservoirs include the hydrosphere, atmosphere, biosphere, and lithosphere.
Five major transformations: nitrogen fixation, nitrification, assimilation and mineralization, denitrification.

Nitrogen Fixation

Nitrogen fixation transforms atmospheric nitrogen into usable forms for producers.
Biological fixation is carried out by cyanobacteria and some bacteria, converting N2 into NH3.
Abiotic processes like lightning and combustion can also produce NO3- in the atmosphere.

Nitrification

Nitrification converts ammonium (NH4+) into nitrite (NO2-) and then nitrate (NO3-).
It is carried out by prokaryotes.
Nitrosomonas and Nitrosococcus convert NH4+ to NO2-, while Nitrobacter and Nitrococcus convert NO2- to NO3-.

Assimilation and Mineralization

Producers incorporate NH4+ and NO3- into their tissues (assimilation).
Consumers assimilate nitrogen through ingestion or excrete it as waste.
Waste is broken down into ammonia and inorganic compounds (mineralization).

Denitrification

Denitrification converts NO3- back into nitrogen gas (N2).
It occurs in anaerobic environments, where NO3- is converted to NO2- and then NO.
Additional reactions produce N2O and eventually N2.

Human Impacts on the Nitrogen Cycle

Human activities have nearly doubled nitrogen inputs to terrestrial ecosystems.
This is mainly due to fertilizers, nitrogen-fixing crops, and combustion of fossil fuels.
Excess nitrogen can affect ecosystems, impacting productivity and species richness.

Phosphorus Cycles

Phosphorus is essential for bone and shell formation, nucleic acids, and ATP.
Phosphorus is a limiting nutrient for both aquatic and terrestrial ecosystems.
It cycles through the hydrosphere, biosphere, and lithosphere, with limited presence in the atmosphere.

Phosphorus Cycling

Phosphorus exists primarily as phosphate (PO43-), and it is taken up by plants and excreted by animals through urine.
Phosphate rocks are a major source of phosphate.
They are formed through precipitation in ocean water and later exposed through geological forces and weathering.
In terrestrial ecosystems, phosphate can be tightly bound to soil or taken up by plants.
Excess phosphate can be released through runoff and leaching, entering aquatic systems.

Phosphorus in Aquatic Ecosystems

In aquatic ecosystems, phosphate is taken up by producers.
Well-oxygenated waters promote the binding of phosphate with calcium and iron, leading to precipitation and sedimentation.
Phosphate is slowly converted back into calcium phosphate rocks.

Human Impacts on the Phosphorus Cycle

Human activities have increased phosphorus levels in aquatic systems, leading to eutrophication.
Cultural eutrophication is the increase in productivity caused by human activities, such as excessive fertilizer use and wastewater discharge.

Nutrient Cycles in Terrestrial Ecosystems

Most nutrients in terrestrial ecosystems are generated from organic matter in the soil.
Nutrients are lost through leaching and runoff, and these losses must be balanced by inputs to maintain ecosystem function.
Some nutrients, like nitrogen and carbon, can be obtained from the atmosphere, while others, like phosphorus, come from the weathering of bedrock.

Weathering

Weathering is the physical and chemical alteration of rock material near the Earth’s surface.
It is a slow process, but it is a significant source of nutrients for terrestrial ecosystems.
The rate of weathering can be determined by measuring nutrient inputs and outputs in a watershed.

Rate of Weathering

The rate of weathering varies geographically, influenced by temperature, precipitation, and soil conditions.
For example, acidic soils increase the rate of weathering.

Breakdown of Organic Matter

Organic matter in terrestrial ecosystems is broken down in four ways:
- Leaching: soluble materials are removed from organic matter.
- Large detritivores: consume dead organic matter.
- Fungi: break down woody components and leaves.
- Bacteria: decompose all types of organic matter.

Factors Affecting Decomposition

Several factors influence the rate of decomposition, including temperature, pH, moisture, and the chemical composition of organic matter.
Decomposition is typically faster in warmer, wetter environments, like the tropics.
The amount of dead plant matter varies across ecosystems, being higher in temperate coniferous forests and lower in tropical rainforests.

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Test your knowledge on the carbon and nitrogen cycles, including the transformations that influence carbon movement in Earth's systems. Explore how human activities have impacted these cycles and the implications for our environment. Understand the connections between these fundamental biogeochemical cycles.