3.8.8Additional lessons
The Carbon Cycle — IB Biology SL Revision Notes & Topical Questions
5 min read 4 parts Lesson 98 of 142
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 4Stores and Fluxes
The carbon cycle is the set of processes that transfer carbon between living organisms, the atmosphere, the oceans, soils and rocks.
Carbon stores
- Carbon stores Pools such as the atmosphere, oceans, living organisms, soil, peat and fossil fuels each hold a different amount of carbon.
Fluxes
- Fluxes Processes that move carbon between stores, including photosynthesis, respiration, decomposition, dissolving and combustion.
Organic carbon
- Organic carbon Carbon in the biomass of living things, as carbohydrates, lipids and proteins, and in dead remains.
Inorganic carbon
- Inorganic carbon Carbon dioxide in the atmosphere and hydrogencarbonate ions in the oceans.
Diagrams
- Diagrams Carbon cycle diagrams use boxes for stores and labelled arrows for fluxes, and may show land, sea or both.
| Flux | From | To |
|---|---|---|
| Photosynthesis | Atmosphere or ocean | Producers |
| Feeding | Producers | Consumers |
| Respiration | Organisms | Atmosphere or ocean |
| Decomposition | Dead matter | Soil and atmosphere |
| Combustion | Fuels and biomass | Atmosphere |
Part 2 of 4Sinks and Sources
Sinks and Sources
Carbon sink
- Carbon sink A store that takes up more carbon than it releases, such as growing forests, oceans, peat and fossil deposits.
Carbon source
- Carbon source A process or store that releases carbon into the atmosphere, such as combustion, respiration and decay.
Net uptake
- Net uptake If photosynthesis exceeds respiration in an organism or ecosystem, there is net uptake of carbon dioxide.
Net release
- Net release If respiration exceeds photosynthesis, as in most animals, there is net release of carbon dioxide.
Long-term storage
- Long-term storage Dead plant matter that does not fully decay may form peat or fossil fuels, which hold carbon for thousands to millions of years.
Part 3 of 4Combustion and the Keeling Curve
Complete combustion of a hydrocarbon gives carbon dioxide and water, for example CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l).
1
Burning coal, oil and natural gas releases carbon that has been locked up for millions of years as carbon dioxide.
2
Peat and biomass also release carbon dioxide when burned, with peat taking longer to re-form than wood.
3
Charles Keeling began measuring atmospheric carbon dioxide at Mauna Loa in Hawaii in 1958.
4
The record shows a regular yearly zigzag, as photosynthesis in the northern hemisphere reduces carbon dioxide in spring and summer.
5
Added to this seasonal pattern is a steady upward trend, caused largely by human combustion of fossil fuels.
Part 4 of 4Exam Checklist & Tips
3.8.8 – Key Points for the Exam
- Carbon sink A store that absorbs and holds more carbon than it releases.
- Carbon source A process or store that releases carbon dioxide to the atmosphere.
- Flux The movement of carbon from one store to another.
- Combustion Burning of a fuel in oxygen, releasing carbon dioxide and energy.
- Keeling curve The long-term record of atmospheric carbon dioxide concentration measured at Mauna Loa.
Common Mistakes
- Treating an organism as only a sink or only a source; plants both take up and release carbon dioxide.
- Explaining the Keeling curve's yearly wave by fossil fuel use rather than seasonal photosynthesis.
- Mixing up organic and inorganic carbon forms.
- Saying fossil fuels are renewable on human timescales.
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