Ecosystems and Biodiversity

Where this fits in the syllabus

Grade 11 · Term 3

Key points to revise

Revise Ecosystems and Biodiversity fast with concise, exam-ready key points

About O/L Science: O/L Science integrates physics, chemistry, and biology into a single subject across Grade 10 and 11.

• Food web: multiple interconnected food chains; energy flows producer → consumer
• Trophic levels: producers (T1), primary consumers (T2), secondary (T3), tertiary (T4)
• Carbon cycle: photosynthesis (CO₂→ organic C); respiration/combustion (organic C → CO₂)
• Nitrogen cycle: fixation → nitrification → assimilation → denitrification
• Biodiversity: species richness + evenness; high diversity → more resilient ecosystem

Must know

• Only ~10% energy passes to each trophic level
• Carbon cycle: photosynthesis (fixes C), respiration/combustion (releases C)
• Nitrogen cycle: fixation (lightning, bacteria) → nitrification → uptake → denitrification
• Biodiversity: variety of species; high diversity = resilient ecosystem
• Threats: deforestation, pollution, overfishing, invasive species, climate change

Source: NIE O/L Science Grade 11 — Unit 7: Ecosystems

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In the Syllabus