# Decay and Decomposition
All living organisms eventually die. Decomposition is the breakdown of dead organisms by bacteria and fungi, recycling nutrients back into the ecosystem. Without decomposers, nutrients would remain locked in dead matter.
1. The Role of Decomposers
Decomposers (bacteria and fungi) feed on dead organisms and waste:
- Break down complex molecules into simpler ones
- Release mineral ions back into soil → absorbed by plants
- Essential for nutrient cycling
- Part of every food chain/web (detritivores feed on dead matter too)
2. Factors Affecting Rate of Decay
| Factor | Effect |
|---|---|
| Temperature | Warm (optimum ~25-45°C) → enzymes work faster → faster decay |
| Moisture | Moist conditions → decomposers more active |
| Oxygen | Aerobic decomposition is faster; anaerobic is slower |
| Number of decomposers | More decomposers → faster breakdown |
| Surface area | Smaller pieces → faster decay |
3. Composting
Compost is decomposed organic matter used to enrich soil.
How to make good compost:
- Mix green (nitrogen-rich) and brown (carbon-rich) materials
- Keep moist (not waterlogged)
- Turn regularly to aerate (provides O₂)
- Decomposers generate heat → speeds up process
Why compost is useful:
- Recycles garden and kitchen waste
- Adds nutrients to soil
- Improves soil structure
- Reduces landfill waste
4. Biogas Production
Anaerobic decomposition can produce biogas (mostly methane, CH₄).
- Organic waste placed in sealed container (biogas generator)
- Bacteria break it down without oxygen
- Methane collected and used as fuel
- Remaining material used as fertiliser
Advantages
- Renewable energy source
- Reduces waste in landfill
- Reduces greenhouse gas emissions
5. Preserving Food
Food preservation slows down decomposition:
| Method | How It Works |
|---|---|
| Refrigeration | Low temperature slows enzyme activity |
| Freezing | Very low temperature; stops decomposition |
| Canning | Sealed container; no oxygen or microorganisms |
| Drying | Removes moisture needed by decomposers |
| Salting/sugaring | Draws water out by osmosis |
| Vinegar (pickling) | Low pH kills/inhibits bacteria |
| Vacuum packing | Removes oxygen |
6. Practice Questions
- Why are decomposers important in ecosystems?
- Describe three factors that affect the rate of decomposition.
- Explain how composting recycles nutrients.
- How does a biogas generator work?
- Explain why food lasts longer in a refrigerator than at room temperature.
Want to check your answers and get step-by-step solutions?
Summary
- Decomposers (bacteria, fungi) break down dead matter → recycle nutrients
- Faster decomposition: warm, moist, aerobic conditions
- Composting: controlled decomposition for gardening
- Biogas: methane from anaerobic decomposition → renewable fuel
- Food preservation: slows/prevents decomposition