NEET 2016 Phase 1 · BiologyPrevious Year Question
A river with an inflow of domestic sewage rich in organic waste may result in:
Answer: (D) Death of fish due to lack of oxygen.. Answer: (4) Death of fish due to lack of oxygen.
- A.Drying of the river very soon due to algal bloom.
- B.Increased population of aquatic food web organisms.
- C.An increased production of fish due to biodegradable nutrients.
- D.Death of fish due to lack of oxygen.✓
Correct Answer
(D) Death of fish due to lack of oxygen.
Solution & Explanation
Answer: (4) Death of fish due to lack of oxygen. Solution: Domestic sewage rich in organic waste raises the BOD; aerobic microbes consume the organic matter and deplete dissolved oxygen in the water. With oxygen exhausted, fish and other aquatic organisms die. The greater the BOD of the waste water, the more its polluting potential, so options suggesting increased fish or food-web growth are wrong. NCERT Reference: Ch 8, p.154, line 30 — "The greater the BOD of waste water, more is its polluting"
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