A4 - Biogeochemical Cycles

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Questions and Answers

What is the primary process through which bacteria convert nitrogen gas into ammonia in the nitrogen cycle?

Ammonification

Denitrification

Nitrogen fixation (correct)

Nitrification

What is one major consequence of melting snow and ice in relation to albedo?

Increased absorption of light and radiation (correct)

Increased reflection of sunlight

Reduced atmospheric CO2 levels

Decreased global temperatures

How do animals obtain nitrogen for their biological needs in the nitrogen cycle?

Through direct absorption from the soil

By consuming other animals

Through the atmospheric nitrogen directly

By eating plants (correct)

What major role do the oceans play in the carbon cycle?

They are the largest carbon sink in the biosphere Signup and view all the answers

What process converts excess nitrates in the soil back into atmospheric nitrogen?

Denitrification Signup and view all the answers

What results from the reaction of SO2 with CO2 and water vapor in the atmosphere?

Formation of sulfuric acid Signup and view all the answers

How do decomposers contribute to the sulfur cycle?

By returning sulfur to soil and atmosphere after decomposition Signup and view all the answers

What is a significant source of sulfur emissions due to human activities?

Burning of fossil fuels Signup and view all the answers

What is the main reason phosphorus is essential for organisms?

It is necessary for bones and teeth Signup and view all the answers

In what form do plants primarily absorb phosphorus from water?

Phosphate (PO43−) Signup and view all the answers

What environmental impact can excess nitrates and phosphates cause?

Algal blooms in water bodies Signup and view all the answers

What term describes the movement of water through soil particles?

Percolation Signup and view all the answers

What is not a function of sulfur in living organisms?

Composed of nucleic acids Signup and view all the answers

What is the primary role of water in biogeochemical cycles?

It acts as a universal solvent and facilitates hydrogen bonding. Signup and view all the answers

Which biogeochemical cycle involves the slow cycling of carbon?

The carbon cycle involving fossil fuel deposits Signup and view all the answers

Which human activity is known to increase CO2 levels in the atmosphere?

Mining fossil fuels Signup and view all the answers

What role do carbon sinks play in the carbon cycle?

They contain and store carbon for extended periods. Signup and view all the answers

How does energy relate to matter in maintaining homeostasis in ecosystems?

The balance of energy and matter is crucial for ecosystem stability. Signup and view all the answers

How do fossil fuels relate to the carbon cycle?

They represent a slow cycling process of carbon accumulation. Signup and view all the answers

What is a consequence of clearing vegetation on carbon dioxide levels?

It increases CO2 levels in the atmosphere. Signup and view all the answers

Which of the following cycles is closely linked to carbon through biological processes?

The oxygen cycle through cellular respiration and photosynthesis. Signup and view all the answers

Study Notes

Biogeochemical Cycles

Biogeochemical cycles are the cyclical movement of chemical elements and compounds between biotic and abiotic components of ecosystems.
Chemicals are constantly recycled in ecosystems.
Water plays a key role in biogeochemical cycles due to its chemical and physical properties, notably its ability to act as a universal solvent and its hydrogen bonding.
Key cycles include carbon, oxygen, nitrogen, phosphorus, and sulfur.

Necessity of Cycles

Limited matter in ecosystems necessitates constant recycling of chemicals.
Essential nutrients are obtained from the recycling of matter through both biotic and abiotic components.
The main biogeochemical cycles are oxygen, carbon, nitrogen, sulfur, and phosphorus cycles.

The Carbon Cycle

Carbon cycles rapidly and slowly.
Rapid cycling involves processes like photosynthesis, respiration, combustion, and ocean uptake.
Slow cycling includes processes like weathering and the formation and decomposition of fossil fuels.
Carbon sinks like trees, fossil fuels, oceans, and limestone rock store carbon for long periods.

Human Impacts on the Carbon Cycle

Mining fossil fuels increases atmospheric carbon dioxide (CO2).
Deforestation increases CO2.
The greenhouse effect traps heat from the sun.
Increased atmospheric CO2 causes global warming.
Global warming increases the average temperature on Earth.
Increased CO2 levels in oceans cause ocean acidification.

The Nitrogen Cycle

Nitrogen (N2) makes up 78.1% of Earth's atmosphere.
Organisms need nitrogen to produce proteins and DNA.
Atmospheric nitrogen cannot be used directly by organisms.
Nitrogen fixation converts atmospheric nitrogen into ammonia (NH3), which can be used by plants.
Plants convert ammonia into nitrates.
Animals obtain nitrogen by eating plants or other animals.
Excess nitrates are converted back into atmospheric nitrogen by denitrification.

The Phosphorus Cycle

Phosphorus is essential for bones, teeth, and cellular materials like DNA and ATP.
Does not cycle in the atmosphere, mostly found in soil and water.
Phosphorus is stored in rocks and released through weathering and erosion .
Key part of the phosphorus cycle is percolation and leaching, affecting water cycles.

The Sulfur Cycle

Sulfur is found in rocks, coal, and oil.
Volcanic activity, geologic uplift, and burning fossil fuels release sulfur dioxide (SO2).
Sulfates are returned to Earth through acid precipitation.
Bacteria enable plants to use sulfates.
Decomposition returns sulfur to soil.
Some sulfur is redeposited in rocks.

Acid Decomposition

Acid deposition (also called acid rain) occurs when sulfur released into the atmosphere reacts with water to form sulfuric or sulfurous acid.
This can alter pH and leach nutrients from soil.
Human activities release significantly more sulfur than natural processes.

Eutrophication

Eutrophication is excessive nutrient (especially phosphorus) input into a body of water.
It leads to algal blooms, reducing light penetration and oxygen levels.
Dead organisms cause the release of more nutrients and organic materials, which further depletes oxygen.
This results in the death of aquatic organisms (hypoxia).
Decomposers then proliferate, reducing oxygen levels even further.

Energy and Matter Transfer

Energy is involved in every step of biogeochemical cycles.
Water and energy link biogeochemical cycles through ecological interactions.

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Description

Explore the major biogeochemical cycles that govern the movement of chemical elements within ecosystems. This quiz covers essential cycles such as carbon, nitrogen, and water, highlighting their processes and importance in recycling nutrients. Test your knowledge on how these cycles contribute to the ecological balance.