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Syllabus

Ecosystem

ICSE · Class 12 · Biology

Complete topic list for Ecosystem in ICSE Class 12 Biology. Key concepts, sub-topics, and what to focus on for board exams.

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A flowchart illustrating the sequential and simultaneous steps involved in the decomposition of detritus: fragmentation, leaching, catabolism, humification, and mineralisation.
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4 Topics · ICSE Class 12 Biology

Topics in Ecosystem

1

  • Ecosystem: coined by G. Tansley, 1935 = biotic + abiotic components interacting together
  • EP Odum (1962): basic functional unit of ecology
  • Forbes & Mobius (1877): first described ecosystem concept (called biotic community)
2

  • Biotic components: (1) Producers/Autotrophs — green plants, algae, cyanobacteria; fix solar energy via photosynthesis; (2) Consumers/Heterotrophs — herbivores (primary), carnivores (secondary, tertiar
  • Abiotic components: temperature, water (H2O), light (sunlight), humidity, wind, pH, mineral elements, topography
  • Pond ecosystem: abiotic (water, CO2, O2, minerals); producers (phytoplankton, algae, Chara, Hydrilla); consumers (zooplankton, insects, fish, frogs, birds); decomposers (bacteria, fungi in bottom sedi
3

  • PAR (Photosynthetically Active Radiation) = wavelengths 400-700 nm; only 2-10% of total solar radiation used by plants
  • Gross Primary Productivity (GPP) = total rate of photosynthesis = total energy fixed per unit area per unit time
  • Net Primary Productivity (NPP) = GPP − Respiration (R) = energy available to consumers
4

  • Decomposition = breakdown of dead organic matter (detritus) into inorganic nutrients
  • Step 1 — Fragmentation: detritivores (earthworms, millipedes, woodlice) break detritus into smaller pieces — increases surface area
  • Step 2 — Leaching: water-soluble inorganic and organic nutrients move into soil below

Chapter Syllabus

Ecosystem is part of the ICSE Class 12 Biology syllabus. It covers the core concepts and topics prescribed by the board for the 2026 academic year.

Frequently Asked Questions

What are the important topics in Ecosystem for ICSE Class 12 Biology?
Key topics in Ecosystem include Decomposition Steps in Sequence, Carbon Cycle — Simplified, Biotic Components of an Ecosystem. These are the concepts ICSE Class 12 examiners draw on most — study them first, then practise related questions.
How to score full marks in Ecosystem — ICSE Class 12 Biology?
Understand the core concepts first, then work through the 60 practice questions available for this chapter. Revise formulas and definitions regularly, and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

More resources for Ecosystem

All 15 chapters — ICSE Class 12 Biology Syllabus

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