UPSC Prelims 2017 · Question 9 of 99
UPSC Prelims 2017 question on Biological Oxygen Demand
- ExamUPSC CSE
- Year2017
- PaperGeneral Studies Paper I
- SubjectEnvironment and Ecology
- TopicEcology and Ecosystem
- DifficultyEasy
- TypeDirect
Biological Oxygen Demand (BOD) is a standard criterion for
Show answer
Answer: C. Pollution assay in aquatic ecosystems
Verdict
The answer is pollution assay in aquatic ecosystems. Biological Oxygen Demand measures organic pollution in water.
Analysis
Biological Oxygen Demand is the quantity of dissolved oxygen required by aerobic microorganisms to break down the organic material present in a given water sample. Because sewage and organic effluent feed those microorganisms, a heavily polluted water body registers a high BOD, and the measure is therefore a standard indicator of organic pollution load. It has nothing to do with oxygen in blood, oxygen production in forests or oxygen availability at altitude, all of which concern free oxygen rather than microbial demand for it.
Source
NCERT Class XII Biology, Chapter 16.
How to crack it
Unpack the term, since demand implies a requirement by something living and biological identifies that something as microorganisms, so the measure can only concern a medium where microbes decompose organic matter. Keep BOD paired with Chemical Oxygen Demand, which uses a chemical oxidant and therefore captures a wider range of pollutants, because UPSC tests the contrast between the two as often as either alone.
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