UPSC Prelims 2013 · Question 3 of 99
UPSC Prelims 2013 question on Decomposers Food Chain
- ExamUPSC CSE
- Year2013
- PaperGeneral Studies Paper I
- SubjectEnvironment and Ecology
- TopicEcology and Ecosystem
- DifficultyHard
- TypeDirect
With reference to food chains in ecosystems, which of the following organisms are known as decomposers?
1. Virus
2. Fungi
3. Bacteria
Select the correct answer using the codes given below.
Show answer
Answer: B. 2 and 3 only
Verdict
Correct Answer: 2 and 3 only
Analysis
Decomposers are organisms that break down dead organic matter into simpler substances and recycle nutrients in an ecosystem. They are mainly active in the detritus food chain.
Statement by statement
1. Virus — Incorrect
Viruses are obligate intracellular parasites.
They require a living host cell for replication and do not independently carry out metabolic activities.
They do not break down dead organic matter, so they are not decomposers.
2. Fungi — Correct
Fungi are important decomposers in ecosystems.
They secrete enzymes that break down complex organic matter such as cellulose, lignin, wood and leaf litter.
They absorb nutrients after decomposition.
3. Bacteria — Correct
Bacteria are major microscopic decomposers found in soil and water.
They break down dead plants, animals and waste materials.
They also help in mineralization by converting organic matter into inorganic nutrients usable by plants.
Extra UPSC info
* Decomposers are also called saprotrophs.
* They form the base of the detritus food chain.
* Fungi are especially important in breaking down tough plant materials like wood and leaves.
* Bacteria help recycle nutrients such as nitrogen, carbon and phosphorus.
* Detritivores like earthworms physically fragment dead matter, while decomposers chemically break it down.
* Humification leads to the formation of humus, which acts as a nutrient reservoir in soil.
How to crack it
Fungi and bacteria are decomposers because they chemically break down dead organic matter, while viruses are not decomposers.
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