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Our Environment — Question 4

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Question 4

What will happen if we kill all the organisms in one trophic level?

Answer

In a food chain, organism at each trophic level is responsible for flow of energy. If we kill all the organisms in one trophic level this flow of energy would stop, creating an imbalance in the ecosystem. It will result in increase in population of organisms at previous trophic level and decrease in population of organisms at next trophic level. If all primary consumers die, the number of plants will increase immensely and the secondary consumers will die due shortage of food.

For example, in the given food chain,

Plants → Deer → Lion

if all deer and other herbivores die, the number of plants will increase and animals like lion will die due to starvation as there will be no herbivores left.

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Science | Chapter 13: Our EnvironmentWeb Content

Chapter 13: Our Environment — Quick Revision Guide

Introduction

Our environment is a complex web of living and non-living components. This chapter covers ecosystems, food chains, energy flow, ozone layer depletion, and waste management.

Key Points at a Glance

  1. Ecosystem: biotic (producers, consumers, decomposers) + abiotic (temperature, water, soil, light)
  2. Food chain: linear energy transfer; Grass → Grasshopper → Frog → Snake → Hawk
  3. Trophic levels: T1 (producers), T2 (primary consumers), T3, T4; usually 4–5 levels max
  4. 10% law (Lindeman): only 10% energy transfers to next level; rest lost as heat in life processes
  5. Food web: interconnected chains; more stable; if one species declines, alternatives exist
  6. Biological magnification: non-biodegradable chemicals (DDT) concentrate at higher trophic levels
  7. Ozone (O3) in stratosphere absorbs UV; CFCs deplete ozone; Montreal Protocol (1987) limits CFCs
  8. Biodegradable waste: broken down by microorganisms; composting, vermicomposting, biogas
  9. Non-biodegradable waste: persists; plastic, glass, DDT; reduce, reuse, recycle
  10. Problems: biomagnification, plastic pollution, e-waste toxicity, air pollution from burning waste

Real-World Connections

Banning single-use plastic reduces pollution; composting reduces landfill load; ozone layer is slowly recovering; understanding food chains helps conservation; DDT ban protected bird populations.

Quick Self-Test (5 Questions)

  1. What is the most important concept you learned from this chapter?
  2. Can you write three key equations/formulae from this chapter from memory?
  3. Draw a labelled diagram relevant to this chapter without looking at your notes.
  4. Explain one real-world application of a concept from this chapter.
  5. What is one common mistake students make in this chapter, and how can you avoid it?

Further Study

  • NCERT Textbook Chapter 13
  • NCERT Exemplar Problems
  • Bright Tutorials Detailed Notes: ch13-our-environment.html
  • Bright Tutorials Practice Questions: ch13-our-environment.html
  • Previous Year CBSE Board Papers

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