A list of different stages that occur in the process of eutrophication is given.
- reduction in dissolved oxygen
- increase in nitrate ions
- death of organisms requiring dissolved oxygen
- growth of producers
- increased aerobic respiration by decomposers
- death of producers followed by their decomposition
What is the correct order in which these processes occur during eutrophication?
A) 1 → 3 → 5 → 2 → 6 → 4
B) 2 → 4 → 1 → 6 → 5 → 3
C) 2 → 4 → 6 → 5 → 1 → 3
D) 5 → 1 → 3 → 6 → 2 → 4
▶️ Answer/Explanation
Ans: C
Correct sequence of eutrophication:
- 2 → Increase in nitrate ions: Fertilizer runoff introduces excess nitrates.
- 4 → Growth of producers: Algae/phytoplankton bloom due to excess nutrients.
- 6 → Death of producers: Algae die when nutrients are depleted.
- 5 → Increased aerobic respiration by decomposers: Bacteria decompose dead algae, consuming oxygen.
- 1 → Reduction in dissolved oxygen: Oxygen levels drop due to decomposition.
- 3 → Death of oxygen-dependent organisms: Fish and other aerobic organisms die from hypoxia.
Thus, the correct order is 2 → 4 → 6 → 5 → 1 → 3 (Option C).
The flow chart describes the process of eutrophication.
What should be at step X and step Y in the flow chart?
▶️ Answer/Explanation
Ans: B
The correct sequence for eutrophication is:
X: Increased nitrate/phosphate levels (from fertilizers/sewage)
Y: Death of aquatic organisms (due to oxygen depletion)
This matches option B. The process begins with nutrient enrichment (X), leading to algal blooms that block sunlight. When algae die, decomposers use up oxygen, causing hypoxia and organism death (Y).