Question 2
What is the role of decomposers in the ecosystem?
The microorganisms, comprising bacteria and fungi, that break-down the dead remains and waste products of organisms are called decomposers. They break-down the complex organic substances into simple inorganic substances that go into the soil and are used up once more by the plants. Thus they help to clean up by decomposing dead remains and also maintain the nutrient cycle by returning the plant nutrients back into the soil.
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
- Ecosystem: biotic (producers, consumers, decomposers) + abiotic (temperature, water, soil, light)
- Food chain: linear energy transfer; Grass → Grasshopper → Frog → Snake → Hawk
- Trophic levels: T1 (producers), T2 (primary consumers), T3, T4; usually 4–5 levels max
- 10% law (Lindeman): only 10% energy transfers to next level; rest lost as heat in life processes
- Food web: interconnected chains; more stable; if one species declines, alternatives exist
- Biological magnification: non-biodegradable chemicals (DDT) concentrate at higher trophic levels
- Ozone (O3) in stratosphere absorbs UV; CFCs deplete ozone; Montreal Protocol (1987) limits CFCs
- Biodegradable waste: broken down by microorganisms; composting, vermicomposting, biogas
- Non-biodegradable waste: persists; plastic, glass, DDT; reduce, reuse, recycle
- 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)
- What is the most important concept you learned from this chapter?
- Can you write three key equations/formulae from this chapter from memory?
- Draw a labelled diagram relevant to this chapter without looking at your notes.
- Explain one real-world application of a concept from this chapter.
- 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