UPSC Prelims 2013 Q31: Environment & Ecology – Ecosystems & Ecology Concepts
With reference to food chains in ecosystems, consider the following statements:
1. A food chain illustrates the order in which a chain of organisms feed upon each other.
2. Food chains are found within the populations of a species.
3. A food chain illustrates the numbers of each organism which are eaten by others.
Which of the statements given above is/are correct?
- (a) 1 only
- (b) 1 and 2 only
- (c) 1, 2 and 3
- (d) None
Answer: (a) 1 only
Explanation
Food chains in ecosystems
| Statement | Verdict | Reason |
|---|---|---|
| 1. A food chain illustrates the order in which a chain of organisms feed upon each other | Correct | This is the definition |
| 2. Food chains are found within the populations of a species | Incorrect | A food chain links different species, not members of one species |
| 3. A food chain illustrates the numbers of each organism which are eaten by others | Incorrect | Numbers are shown by a pyramid of numbers, not a food chain |
Related terms:
| Term | Meaning |
|---|---|
| Food chain | Who eats whom, in a single line |
| Food web | Many food chains linked together |
| Trophic level | Position in the chain: producer, primary consumer and so on |
| Ecological pyramid | Shows number, biomass or energy at each level |
Types of food chain: grazing (starts with green plants) and detritus (starts with dead matter).
Answer: (a) 1 only.
Why each option is right or wrong
- (a) CORRECT. Only statement 1 correctly describes a food chain.
- (b) Incorrect. Food chains are not found within one species.
- (c) Incorrect. Statements 2 and 3 are false.
- (d) Incorrect. Statement 1 is true, so 'None' is wrong.
Key point
Food chain: order of feeding among different species. Numbers are shown by ecological pyramids; linked chains form a food web.
Remember
Food chain shows who eats whom, not how many.
Common mistakes
- Confusing a food chain with a pyramid of numbers.
- Thinking a food chain can exist inside one species.
- Forgetting the two kinds: grazing and detritus chains.
Exam tip
Chain = order of feeding. Pyramid = quantity at each level.
Sources
- NCERT Class XII — Biology (Ecosystem: food chains and ecological pyramids)
- NCERT Class X — Science, Ch 13 (Our Environment)