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Which of the following is absent in polluted water : -
A
Hydrilla
B
Water hyacinth
C
Larva of stone fly
D
Blue green algae
Detailed Solution
Some organisms can live only in clean, well oxygenated water, so their presence or absence indicates the quality of water.
Stonefly larvae (and mayfly nymphs) need high dissolved oxygen and are very sensitive to pollution. They disappear from polluted water, so they are indicators of clean water.
Water hyacinth (Eichhornia) and blue green algae grow abundantly in polluted, nutrient-rich (eutrophic) water, and Hydrilla also tolerates such water.
So the larva of the stone fly is absent in polluted water.
Stonefly larvae (and mayfly nymphs) need high dissolved oxygen and are very sensitive to pollution. They disappear from polluted water, so they are indicators of clean water.
Water hyacinth (Eichhornia) and blue green algae grow abundantly in polluted, nutrient-rich (eutrophic) water, and Hydrilla also tolerates such water.
So the larva of the stone fly is absent in polluted water.