Environmental Science: Biogeochemical Cycles

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Questions and Answers

Which of the following correctly describes a feature of the nitrogen biogeochemical flow?

It is exclusively utilized by plants.

It is primarily found in oceans.

It has been surpassed in planetary boundaries. (correct)

It has remained stable within planetary boundaries.

What is the main form in which phosphorus is commonly found?

In soils as nitrogen compounds.

In rocks as phosphates. (correct)

In freshwater as dissolved ions.

As a gas in the atmosphere.

Which type of feedback amplifies the initial input, continuing in one direction?

Neutral feedback loops.

Homeostatic feedback.

Positive feedback loops. (correct)

Negative feedback loops.

What phenomenon serves as an example of a positive feedback loop in climate change?

Melting permafrost releasing methane or CO2. Signup and view all the answers

In the short-term carbon cycle, which process returns carbon dioxide back to the atmosphere?

Decomposition. Signup and view all the answers

Which component acts as the largest reservoir for carbon?

Sedimentary rocks. Signup and view all the answers

How does weathering of rocks influence atmospheric carbon dioxide levels?

It removes carbon dioxide from the atmosphere. Signup and view all the answers

What role do keystone species play in ecosystems?

They regulate feedback processes within the ecosystem. Signup and view all the answers

What is the primary role of nitrogen-fixing bacteria in the nitrogen cycle?

To convert atmospheric nitrogen into ammonium or nitrate Signup and view all the answers

Which process directly results in the atmospheric nitrogen being converted into nitrate in the nitrogen cycle?

Nitrification Signup and view all the answers

In which environment do methanobacterium typically release methane gas?

Wet areas lacking oxygen Signup and view all the answers

What significant event is associated with the increase of oxygen in Earth's atmosphere 2.3 billion years ago?

The Great Oxygenation Event Signup and view all the answers

Which of the following reservoirs holds the largest percentage of nitrogen on Earth?

Atmosphere Signup and view all the answers

Which of the following is a method through which nitrogen is fixed naturally, aside from bacteria?

Lightning Signup and view all the answers

What effect does anoxia have on the carbon cycle?

Sequesters carbon by reducing decomposition Signup and view all the answers

Which of the following compounds can plants directly access as nitrogen sources?

Ammonia (NH₄⁺) and Nitrates (NO₃⁻) Signup and view all the answers

Which gas contributes the least to the Greenhouse Effect due to its properties?

Nitrogen Signup and view all the answers

What effect does longwave radiation have on carbon dioxide?

It causes CO2 to vibrate vigorously. Signup and view all the answers

Which method of heat transmission involves the movement of warm air to cooler regions?

Convection Signup and view all the answers

How does the uplift of the Himalayas affect the carbon cycle?

It introduces fresh rock that enhances chemical weathering. Signup and view all the answers

What significant shift in climate conditions happened over the last 50 million years?

From very warm climates of the Cretaceous to glacial climates of the Pleistocene Signup and view all the answers

Which gas is noted for having nine different types of vibrations, contributing to its impact on the greenhouse effect?

Methane Signup and view all the answers

What is the role of chemical weathering in the long-term carbon cycle?

It captures carbon, reducing its presence in the atmosphere. Signup and view all the answers

Which of the following is NOT a method by which heat is transmitted?

Evaporation Signup and view all the answers

Study Notes

Planetary Boundaries

Nitrogen is the biogeochemical flow that has been surpassed in planetary boundaries

Phosphorus Cycle

Important for freshwater systems
Mostly found in rocks as phosphates

Feedback

Negative feedback counters initial input (e.g. body temperature regulation through sweating and shivering)
Positive feedback amplifies initial input (example: melting permafrost releasing methane and CO2, further increasing temperatures)
Keystone species are crucial for the health of an ecosystem

Carbon Cycle

Carbon has 4 electrons in its outer shell allowing for easy bonding, especially with itself
Carbon forms chains, creating glucose, and is found in rocks and shells as calcium carbonate
Short-term carbon cycle:
- CO2 in the atmosphere is absorbed by photosynthesis and released through cellular respiration, decomposition, and animal waste
- Human activities have moved coal, a long-term carbon store, into the short-term cycle
Long-term carbon cycle:
- Carbon is stored in sedimentary rocks as the largest reservoir
- Weathering of rocks removes carbon dioxide from the atmosphere
Keeling Curve: Shows seasonal variations in CO2 concentrations

Anoxia (No Oxygen)

Leads to carbon sequestration due to lack of decomposition
Photosynthesis by organisms like duckweeds removed CO2 from the atmosphere, resulting in an 80% drop

Ultraviolet Radiation

Higher energy radiation is more damaging
UV-C is the most damaging, but the Ozone layer protects us
The Ozone layer was created by photosynthesis as a byproduct
Great Oxygenation Event (2.3 Billion Years Ago) initiated the formation of the Ozone

Key Events in Earth's History

First producers, cyanobacteria
Aerobic eukaryotes
Plastid endosymbiosis
Algae
Cambrian explosion
Land plants

Great Rusting Event

Occurred when iron reacted with oxygen

Archaea

Ancient bacteria found in Yellowstone
Deep-sea mining threatens archaea biodiversity

Methane

Produced in landfills, rice fields, and oxygen-deprived areas
Released by methanobacterium archaea

Mass Extinctions

Not excessive in Earth's history

Interacting Spheres

Hydrosphere: Liquid and frozen water
Lithosphere: Earth's mantle, crust, and core
Atmosphere: Gases around air
Biosphere: All living organisms

Soil

A mix of inorganic and organic matter

Reservoirs

Different capacities for holding things (e.g., money in a bank, nitrogen in the atmosphere)

Nitrogen

Most limiting nutrient for food production
78% of the atmosphere is Nitrogen (N2)
Nitrogen-fixing bacteria (e.g., in legume roots) break the triple bond of N2 converting it to ammonia (NH4)
Plants can only access nitrates (NO3) and ammonia (NH4)
Cyanobacteria are also nitrogen-fixing!

Fluxes

Rates of exchange between reservoirs (e.g., gallons per year)

Nitrogen Cycle

Nitrogen fixation: Atmospheric nitrogen (N2) converted to ammonium (NH4+) or nitrate (NO3-) by nitrogen-fixing bacteria, lightning, and industrial processes
Nitrification: Ammonium (NH4+) is oxidized to nitrate (NO3-) by nitrifying bacteria

Carbon Dioxide

Vibrates, absorbing and re-radiating longwave radiation
Oxygen and Nitrogen do not absorb longwave radiation
Methane has 9 different vibration modes, absorbing more longwave radiation
Greenhouse Effect: Water vapour absorbs IR wavelength range, while Nitrogen and Oxygen have little to no absorption

Heat Transmission

Radiation: Heat transfer through electromagnetic waves
Conduction: Heat transfer through direct contact
Convection: Heat transfer through the movement of fluids

Greenhouse Effect

Certain atmospheric components contribute to the Greenhouse Effect, absorbing and re-emitting longwave radiation

Long-Term Carbon Cycle and Climate

The amount of heating affects long-term climate
Tectonic plate movement influences the rate of carbon release from the Earth's interior
Uplift of the Himalayas 50 million years ago increased chemical weathering, pulling more carbon into the slow carbon cycle
This shift resulted in the transition from a warm Cretaceous period to a glacial Pleistocene period, effectively resetting Earth's thermostat

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Description

This quiz covers key concepts from environmental science related to biogeochemical cycles, including the nitrogen and phosphorus cycles, carbon cycles, and feedback mechanisms in ecosystems. Understand how these cycles impact freshwater systems and the planet's boundaries. Explore the roles of keystone species and the significance of feedback in environmental stability.