Chapter Overview & Weightage
- Marks in Boards: 6–10 marks (usually 1–2 questions + diagram/case)
- Repeated Topics: Organism adaptations (desert, aquatic, high altitude), population attributes (density, natality, mortality), population growth models (exponential, logistic), life history variation, population interactions (predation, competition, parasitism, commensalism, mutualism).
- Difficulty: Moderate • Heavy on adaptations, growth curves & interactions.
- Trend (2021–2025): 1 diagram (population growth curves – 3 marks) + 1 long answer (5 marks) on adaptations/interactions + MCQs on population parameters.
Most Important & Repeated Questions (2021–2025)
- Repeated 5–6 times: Explain exponential and logistic growth models with graphs. (5 marks)
- Repeated 4–5 times: Describe adaptations of organisms in desert & aquatic environments. (5 marks)
- Repeated 4 times: What are population attributes? Explain natality, mortality, immigration & emigration. (3 marks)
- Repeated 3–4 times: Explain population interactions: predation, competition, parasitism, commensalism, mutualism with examples. (5 marks)
- Repeated 3 times: Describe adaptations of high altitude plants & animals (e.g., reduced RBC size in humans). (3 marks)
- Repeated 3 times: What is life history variation? Explain r & K selection strategies. (3 marks)
- Repeated 2–3 times: Explain age pyramids & their significance in population studies. (3 marks)
- Assertion-Reason (2023–2025): Assertion: Logistic growth shows S-shaped curve. Reason: It is limited by carrying capacity. (Both true, reason explains – repeated 2x)
Important Keywords & Concepts to Memorize
- Organism adaptations (desert – CAM photosynthesis, kangaroo rat; aquatic – air bladders; high altitude – increased RBC, large lungs), population attributes (density, natality, mortality, immigration, emigration), population growth (exponential, logistic, J-shaped, S-shaped), carrying capacity, age pyramids (expanding, stable, declining), life history variation (r-selection vs K-selection), population interactions (predation – prey defense; competition – Gause's principle; parasitism – endoparasite/ectoparasite; commensalism; mutualism – lichens, mycorrhiza), amensalism, allelopathy.
Exam Strategy for Chapter 13 (2026 Boards)
- Focus: Growth curves (exponential vs logistic) + labelled graphs – practice 4 daily
- High-scoring: Adaptations in desert/aquatic/high altitude (5 marks) + population interactions table
- Time: 8–10 minutes per 5-mark question (diagram + explanation)
- Tip: Draw S-shaped & J-shaped curves neatly – label carrying capacity
- Repeated: Predation & competition examples (2–3 marks)
This is Chapter 13 complete PYQ analysis.
If you want Chapter 14 or any other chapter, just say the chapter number or name.