krit.club logo

Ecology - Climate change

Grade 12IBBiology

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

🔑Concepts

•

The Greenhouse Effect: Greenhouse gases (GHGs) absorb and re-radiate long-wave (infrared) radiation towards the Earth, maintaining the planet's temperature. Without this, Earth's average temperature would be approximately −18∘C-18^{\circ}C.

•

Major Greenhouse Gases: The most significant GHGs are carbon dioxide (CO2CO_2) and water vapor (H2OH_2O). Other gases with lesser impact but higher warming potential per molecule include methane (CH4CH_4) and nitrogen oxides (N2ON_2O).

•

Radiation Types: The Earth receives short-wave radiation (UV and visible light) from the Sun. This energy is absorbed and re-emitted as long-wave radiation (infrared/heat).

•

Impact of Greenhouse Gases: The warming impact of a gas depends on its ability to absorb long-wave radiation and its atmospheric concentration (determined by rate of release and persistence).

•

Industrialization and CO2CO_2: There is a strong positive correlation between rising atmospheric CO2CO_2 concentrations and global temperatures. The industrial revolution increased CO2CO_2 levels primarily through the combustion of fossil fuels (coal, oil, and gas).

•

Ocean Acidification: Approximately 25%25\% of anthropogenic CO2CO_2 is absorbed by the oceans. This leads to a decrease in ocean pHpH and a reduction in the concentration of carbonate ions (CO32−CO_3^{2-}), which are essential for calcifying organisms like corals and mollusks to build CaCO3CaCO_3 shells.

📐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−→CaCO3 (Calcification process)Ca^{2+} + CO_3^{2-} \rightarrow CaCO_3 \text{ (Calcification process)}

pH=−log⁡10[H+]pH = -\log_{10}[H^+]

💡Examples

Problem 1:

Explain the chemical process by which increased atmospheric CO2CO_2 levels lead to the inhibition of shell formation in marine organisms.

Solution:

When atmospheric CO2CO_2 increases, more CO2CO_2 dissolves in seawater: CO2+H2O→H2CO3CO_2 + H_2O \rightarrow H_2CO_3. This carbonic acid dissociates into H+H^+ and HCO3−HCO_3^-, lowering the pHpH. The increased H+H^+ ions react with available carbonate ions: H++CO32−→HCO3−H^+ + CO_3^{2-} \rightarrow HCO_3^-.

Explanation:

This reaction reduces the concentration of free carbonate ions (CO32−CO_3^{2-}). Marine organisms require these ions to react with calcium to form calcium carbonate (CaCO3CaCO_3) for their shells and exoskeletons. Lower CO32−CO_3^{2-} availability makes calcification energetically difficult or causes existing structures to dissolve.

Problem 2:

Compare the impact of CH4CH_4 and CO2CO_2 on global warming.

Solution:

CH4CH_4 has a global warming potential roughly 3030 times higher than CO2CO_2 on a per-molecule basis, but CO2CO_2 has a much higher atmospheric concentration (>400> 400 ppm compared to ≈1.9\approx 1.9 ppm for CH4CH_4).

Explanation:

Even though methane is a more 'potent' greenhouse gas due to its molecular structure and ability to absorb specific infrared wavelengths, carbon dioxide remains the most significant contributor to anthropogenic global warming due to its massive abundance and long residence time in the atmosphere.

Climate change - Revision Notes & Key Diagrams | IB Grade 12 Biology