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Ecology - Climate Change

Grade 11IBBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The Greenhouse Effect: Greenhouse gases (GHGs) absorb and re-radiate long-wave infrared radiation (IRIR) reflected from the Earth's surface, trapping heat in the atmosphere.

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Major Greenhouse Gases: The two most significant GHGs are carbon dioxide (CO2CO_2) and water vapor (H2OH_2O). Other gases with lower concentrations but significant warming potential include methane (CH4CH_4) and nitrous oxide (N2ON_2O).

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Short-wave vs. Long-wave Radiation: The sun emits short-wave radiation (ultraviolet and visible light). The Earth absorbs this and re-emits it as long-wave radiation (infrared/heat).

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Correlation between CO2CO_2 and Temperature: Historical data from ice cores shows a strong positive correlation between atmospheric CO2CO_2 concentrations and global temperatures over the last 400,000400,000 years.

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Ocean Acidification: Increased atmospheric CO2CO_2 leads to more CO2CO_2 dissolving in oceans. This reacts with water to form carbonic acid (H2CO3H_2CO_3), lowering the pHpH.

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Threats to Coral Reefs: Acidification reduces the concentration of carbonate ions (CO32−CO_3^{2-}), which are essential for calcifying organisms to build calcium carbonate (CaCO3CaCO_3) skeletons.

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The Precautionary Principle: An ethical theory suggesting that if an action has a risk of causing harm to the public or the environment, the burden of proof that it is not harmful falls on those taking the action.

📐Formulae

CO2+H2O⇌H2CO3⇌H++HCO3−CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons H^+ + HCO_3^-

H++CO32−→HCO3−H^+ + CO_3^{2-} \rightarrow HCO_3^-

Ca2++CO32−→CaCO3Ca^{2+} + CO_3^{2-} \rightarrow CaCO_3

pH=−log⁡10[H+]pH = -\log_{10}[H^+]

💡Examples

Problem 1:

Explain why an increase in atmospheric CO2CO_2 leads to a decrease in the rate of calcification in marine organisms such as reef-building corals.

Solution:

Increased CO2CO_2 dissolves in seawater to form H2CO3H_2CO_3. This dissociates into H+H^+ and HCO3−HCO_3^-. The H+H^+ ions then react with free carbonate ions (CO32−CO_3^{2-}) to form more bicarbonate (HCO3−HCO_3^-).

Explanation:

Because the H+H^+ ions 'compete' for the CO32−CO_3^{2-} ions, there is a lower concentration of carbonate available for corals to react with Ca2+Ca^{2+} to form the CaCO3CaCO_3 needed for their exoskeletons.

Problem 2:

Compare the impact of CH4CH_4 and CO2CO_2 on the greenhouse effect based on their warming potential and atmospheric persistence.

Solution:

While CH4CH_4 has a much higher global warming potential (roughly 2020 times that of CO2CO_2), CO2CO_2 is present in much higher concentrations and remains in the atmosphere for a significantly longer duration.

Explanation:

The total impact of a greenhouse gas depends on its ability to absorb long-wave radiation and its abundance/lifetime in the atmosphere.

Climate Change - Revision Notes & Key Diagrams | IB Grade 11 Biology