UPSC Prelims 2014 · Question 60 of 100
UPSC Prelims 2014 question on Food Chain Sequence
- ExamUPSC CSE
- Year2014
- PaperGeneral Studies Paper I
- SubjectEnvironment and Ecology
- TopicEcology and Ecosystem
- DifficultyHard
- TypeChronology
Which one of the following is the correct sequence of a food chain?
Show answer
Answer: A. Diatoms-Crustaceans-Herrings
Verdict
The answer is diatoms, then crustaceans, then herrings. Energy flows from producer to primary consumer to secondary consumer.
Analysis
Diatoms are photosynthetic phytoplankton and occupy the producer level. Small crustaceans, that is zooplankton such as copepods, graze on that phytoplankton and form the primary consumer level. Herrings are small fish that feed on zooplankton and sit at the secondary consumer level. The other three options either place a consumer before the producer or place the larger fish before its prey, both of which reverse the direction of energy flow.
Source
Educational material on marine food chains.
How to crack it
A food chain is always written in the direction energy travels, so the producer must come first and body size generally increases along the chain. Apply the size rule as a quick sanity check: diatoms are microscopic, crustaceans are small, herrings are fish, and only one option preserves that ascending order. This works for any marine food chain question because the plankton to zooplankton to small fish to large fish ladder is standard.
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