IB DP Biology- C4.2 Transfers of energy and matter - IB Style Questions For SL Paper 2 - FA 2025

(a)
Carbon’s versatility stems from its ability to:
• Form four covalent bonds with other atoms .
• Form strong bonds with other carbon atoms, as well as other non-metallic elements .
• Form long, unbranched or branched chains .
• Form single, double, or triple bonds .
• Form ring structures .

(b)
Carbon is transferred through several key processes:
• Photosynthesis (Carbon Fixation): Producers (plants) absorb \(\text{CO}_2\) from the atmosphere or water .
• Feeding: Carbon is passed along food chains as organic molecules when consumers eat other organisms .
• Respiration: All living organisms (producers, consumers, decomposers) release \(\text{CO}_2\) back into the environment through cellular respiration .
• Decomposition: Decomposers (saprotrophs) break down dead organic matter, returning carbon to the soil or atmosphere .
• Combustion: Burning of organic matter (like fossil fuels or biomass) releases stored carbon into the atmosphere as \(\text{CO}_2\) .

(c)
Anthropogenic activities increase the concentration of greenhouse gases (like \(\text{CO}_2\) and methane) in the atmosphere, which enhances the natural greenhouse effect, trapping more heat and raising the Earth’s temperature. Key activities include:
• Burning of fossil fuels: Combustion of coal, oil, and natural gas releases vast amounts of stored \(\text{CO}_2\) .
• Deforestation: Removing forests reduces an important \(\text{CO}_2\) sink (less photosynthesis) and often releases \(\text{CO}_2\) through burning .
• Agriculture: Raising livestock (like cattle) releases methane, and the use of certain fertilizers releases nitrous oxides .

Impacts of this warming include:
• Melting of land ice and sea-level rise .
• Loss of polar habitats and reduction in albedo (reflectivity) from ice loss .
• Disruption of ocean currents and nutrient upwelling .
• Coral reef habitat destruction due to bleaching (from heat) and ocean acidification (from dissolved \(\text{CO}_2\)) .
• Species migrating poleward or to higher altitudes to escape warming.