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WAEC Biology 2006 Question 47

Question 47

Pollution

Which of the following orders correctly represents the trend in eutrophication?

  1. A.Lack of oxygen → Death of aquatic organisms → Massive algal growth
  2. B.Excess nitrates and phosphates → Massive algal growth → Lack of oxygen → Death of aquatic organisms
  3. C.Heavy mineralization → Lack of oxygen → Massive algal growth
  4. D.Excess nitrates and phosphates → Lack of oxygen → Massive algal growth → Death of aquatic organisms
Show the answer and explanation

Answer: B (Excess nitrates and phosphates → Massive algal growth → Lack of oxygen → Death of aquatic organisms)

Explanation

Extra nutrients cause algae to grow rapidly; when they die, decomposers use up the oxygen and fish and other organisms die.