Chapter Overview & Weightage
- Marks in Boards: 6–10 marks (usually 1–2 questions + diagram/case)
- Repeated Topics: Productivity (primary, secondary), decomposition, energy flow, nutrient cycles (carbon, nitrogen, phosphorus), ecological pyramids, succession (primary & secondary), ecosystem services.
- Difficulty: Moderate • Heavy on diagrams (energy pyramid, nutrient cycle) & processes.
- Trend (2021–2025): 1 diagram-based (5 marks) on ecological pyramid/nutrient cycle + 1 long answer (5 marks) on energy flow/decomposition + MCQs on productivity/succession.
Most Important & Repeated Questions (2021–2025)
- Repeated 5–6 times: Draw and explain ecological pyramids (number, biomass, energy) with examples. (5 marks)
- Repeated 4–5 times: Explain energy flow in an ecosystem. Draw labelled diagram. (5 marks)
- Repeated 4 times: Describe the carbon cycle with diagram. (3–5 marks)
- Repeated 3–4 times: What is decomposition? Explain role of decomposers & detritivores. (3 marks)
- Repeated 3 times: Differentiate primary and secondary productivity. Factors affecting productivity. (3 marks)
- Repeated 3 times: Explain ecological succession (primary & secondary) with example (e.g., bare rock → lichen → forest). (5 marks)
- Repeated 2–3 times: Describe phosphorus cycle. Why is it sedimentary? (3 marks)
- Assertion-Reason (2023–2025): Assertion: Energy flow in ecosystem is unidirectional. Reason: 10% law of energy transfer. (Both true, reason explains – repeated 2x)
Important Keywords & Concepts to Memorize
- Ecosystem, productivity (primary, secondary, net, gross), decomposition (fragmentation, leaching, catabolism, humification, mineralization), detritivores, standing crop, energy flow (unidirectional, 10% law), food chain (grazing, detritus), food web, ecological pyramids (upright/inverted – number, biomass, energy), nutrient cycling (gaseous/sedimentary – carbon, nitrogen, phosphorus), succession (primary/secondary, seral stages, climax community), ecosystem services (pollination, global climate regulation).
Exam Strategy for Chapter 14 (2026 Boards)
- Focus: Diagrams (ecological pyramid, carbon cycle, energy flow) – practice 4 daily
- High-scoring: Energy flow + 10% law (5 marks) + labelled pyramid
- Time: 8–10 minutes per 5-mark question (diagram + explanation)
- Tip: Label 6–8 parts in every diagram (producers, consumers, decomposers) – neatness = full marks
- Repeated: Nutrient cycles (carbon/nitrogen/phosphorus) – 3–5 marks
This is Chapter 14 complete PYQ analysis.
If you want Chapter 15 or any other chapter, just say the chapter number or name.