2.3 Biogeochemical Cycles (DP IB Environmental Systems & Societies (ESS): SL): Flashcards
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Define biogeochemical cycle.
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Define biogeochemical cycle.
A biogeochemical cycle is a natural process that circulates a chemical element, keeping it available to living organisms.
Name three examples of biogeochemical cycles.
Three examples of biogeochemical cycles are the carbon cycle, the nitrogen cycle and the hydrological cycle.
How can deforestation disrupt the carbon cycle?
Deforestation disrupts the carbon cycle by reducing the number of trees available to absorb carbon dioxide from the atmosphere.
Define a store in a biogeochemical cycle.
A store, such as the ocean or soil, is a reservoir in which an element is held for a period of time.
Define a sink in a biogeochemical cycle.
A sink is a part of a cycle where an element accumulates over time because total input is greater than total output.
Define a source in a biogeochemical cycle.
A source is a part of a cycle that releases an element because total output is greater than total input.
Give an example of a natural carbon sink.
Fossil fuel deposits are an example of a natural carbon sink.
Give an example of a natural carbon source.
Volcanic eruptions, which release large amounts of carbon dioxide, are an example of a natural carbon source.
True or False?
Stores, sinks and sources in biogeochemical cycles can only ever be natural, never artificial.
False.
Stores, sinks and sources can be either natural or artificial.
A store is in equilibrium when the uptake of an element is by its release.
A store is in equilibrium when the uptake of an element is balanced by its release.
Name four human activities that can disrupt biogeochemical cycles.
Human activities such as burning fossil fuels, deforestation, urbanisation and agriculture can disrupt biogeochemical cycles.
Define organic carbon stores.
Organic carbon stores, such as organisms and fossil fuels, hold carbon within carbon-containing compounds like carbohydrates and hydrocarbons.
Define inorganic carbon stores.
Inorganic carbon stores, such as the atmosphere, soils and oceans, hold carbon in non-living forms such as carbon dioxide and carbonates.
Define residence time of a carbon store.
Residence time is the average length of time that a carbon atom remains within a particular store.
True or False?
Without human interference, the residence time of carbon in fossil fuels would be measured in just a few years.
False.
Without human interference, the residence time of carbon in fossil fuels would be measured in hundreds of millions of years.
Which process transfers carbon from the atmosphere into plants as organic compounds?
Photosynthesis transfers carbon from the atmosphere into plants as organic compounds.
Which process releases carbon dioxide back into the atmosphere from both plants and animals?
Cellular respiration in both plants and animals releases carbon dioxide back into the atmosphere.
By which process is carbon returned to the soil in an animal's waste products?
Carbon is returned to the soil through defecation.
Define fossilisation in the carbon cycle.
Fossilisation is the process by which the carbon in dead organisms is converted, over millions of years under pressure, into fossil fuels such as coal, oil and gas.
Which process releases the carbon stored in fossil fuels back into the atmosphere as carbon dioxide?
Combustion (burning fossil fuels) releases the carbon stored in them back into the atmosphere as carbon dioxide.
Define carbon sequestration.
Carbon sequestration is the process of capturing atmospheric carbon dioxide and storing it in a solid or liquid form.
A carbon store is in equilibrium when the absorption of carbon is by its release, as in a tree where photosynthesis balances respiration.
A carbon store is in equilibrium when the absorption of carbon is balanced by its release, as in a tree where photosynthesis balances respiration.
Why does a young forest ecosystem act as a carbon sink?
A young forest acts as a carbon sink because photosynthesis exceeds respiration, leading to a net uptake of carbon dioxide.
True or False?
Forest destruction, such as through fire or deforestation, causes an ecosystem to act as a carbon store.
False.
Forest destruction causes an ecosystem to act as a carbon source, releasing stored carbon back into the atmosphere.
Define fossil fuels in terms of carbon storage.
Fossil fuels, such as coal, oil and gas, are stores of carbon with virtually unlimited residence times, formed when past ecosystems acted as carbon sinks.
True or False?
When fossil fuels are burned, they act as a carbon sink.
False.
When burned, fossil fuels become carbon sources, releasing stored carbon back into the atmosphere as carbon dioxide.
Which regenerative farming techniques help soil act as a carbon sink?
Regenerative techniques such as crop rotation, cover cropping and no-till farming help soil act as a carbon sink by increasing organic matter.
Which farming practices cause agricultural soil to act as a carbon source?
Practices such as draining wetlands, monoculture farming and intensive tillage cause agricultural soil to act as a carbon source.
A sustainably managed forest acts as a carbon sink, but a forest that is clear-cut or managed unsustainably can become a carbon .
A sustainably managed forest acts as a carbon sink, but a forest that is clear-cut or managed unsustainably can become a carbon source.
How does carbon dioxide enter the ocean from the atmosphere?
Carbon dioxide enters the ocean by dissolving in sea water.
True or False?
Oceans are currently absorbing carbon dioxide faster than humans are releasing it by burning fossil fuels.
False.
Humans are releasing carbon dioxide at a faster rate than oceans can absorb it, causing atmospheric CO2 levels to rise.
How does rising ocean temperature affect the ocean's ability to act as a carbon sink?
Rising ocean temperatures reduce the ocean's ability to act as a carbon sink.
Define ocean acidification.
Ocean acidification is the lowering of seawater pH caused by increased concentrations of dissolved carbon dioxide.
How does ocean acidification affect molluscs and corals?
Ocean acidification reduces calcium carbonate deposition in mollusc shells and coral skeletons, weakening them and increasing vulnerability to predators.
Ocean acidification can lead to smaller and less reef structures.
Ocean acidification can lead to smaller and less diverse reef structures.
Give two examples of low-carbon technologies used to reduce carbon emissions.
Low-carbon technologies include renewable energy sources such as solar and wind power, and energy-efficient practices such as better insulation.
What is the essential step in reducing carbon emissions from fossil-fuel burning?
Transitioning to cleaner energy sources such as renewables is essential to reducing carbon emissions from fossil-fuel burning.
Define BECCS (bioenergy with carbon capture and storage).
BECCS produces energy from biomass while capturing and storing the resulting carbon dioxide emissions underground.
Why must bioenergy crops be cultivated sustainably to help reduce carbon emissions?
Bioenergy crops must be cultivated sustainably, without causing deforestation, so that they genuinely absorb carbon dioxide as they photosynthesise.
Sustainable agricultural practices such as crop rotation and cover cropping reduce soil , helping soils act as carbon sinks.
Sustainable agricultural practices such as crop rotation and cover cropping reduce soil disruption, helping soils act as carbon sinks.
Define UN-REDD.
UN-REDD is a UN programme that prevents deforestation and promotes sustainable forest management in developing countries.
How does reforestation help capture carbon from the atmosphere?
Reforestation captures carbon by planting trees on deforested or degraded land, which absorb CO2 through photosynthesis and store it in biomass and soil.
Define carbon capture and storage (CCS).
Carbon capture and storage (CCS) is an artificial sequestration technology that captures CO2 emissions from industrial processes and injects them underground for long-term storage.
How does ocean fertilisation help increase carbon dioxide absorption by the oceans?
Ocean fertilisation adds nutrients such as nitrogen, phosphorus and iron to stimulate phytoplankton growth, which absorb carbon dioxide through photosynthesis.
True or False?
Increasing ocean upwellings has no effect on carbon dioxide absorption by phytoplankton.
False.
Increasing ocean upwellings brings nutrient-rich deep water to the surface, promoting phytoplankton growth and enhancing carbon dioxide absorption.
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