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Question
Harmful activity of blue green algae is
Harmful activity of blue green algae is
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Solution
The correct option is A Water bloom
BGA are prokaryotic organisms that exhibit algal morphology. Heterocyst is transparent thick walled empty cell which is present in intermittent position in filaments of BGA. They are the site of nitrogen fixation and contain nitrogenase, multisubunit enzyme complex, which catalyzes reduction of inert atmospheric nitrogen to biologically useful ammonia. Thus, they are nitrogen fixers, not the denitrifiers that carry out the final step in returning nitrogen back to the atmospheric reservoir. Denitrification bacteria reduce the nitrates into nitrogen. Option A is incorrect. Since, BGA increase the nitrogen content of soil by nitrogen fixation, they increase the soil fertility; option D is incorrect. A soil with pH value above 7 is known as alkaline soil. BGA prefer neutral to alkaline soil for nitrogen fixation and decrease the alkalinity of soil. Option C is incorrect. Water bloom constitutes layer of planktonic cyanobacteria/BGA, on the surface of waters rich in nutrients such as phosphate. Death of these BGA is followed by their decomposition by other bacteria which in turn leads to oxygen depletion and the death of other aquatic life forms. Thus, the correct answer is option B.
BGA are prokaryotic organisms that exhibit algal morphology. Heterocyst is transparent thick walled empty cell which is present in intermittent position in filaments of BGA. They are the site of nitrogen fixation and contain nitrogenase, multisubunit enzyme complex, which catalyzes reduction of inert atmospheric nitrogen to biologically useful ammonia. Thus, they are nitrogen fixers, not the denitrifiers that carry out the final step in returning nitrogen back to the atmospheric reservoir. Denitrification bacteria reduce the nitrates into nitrogen. Option A is incorrect. Since, BGA increase the nitrogen content of soil by nitrogen fixation, they increase the soil fertility; option D is incorrect. A soil with pH value above 7 is known as alkaline soil. BGA prefer neutral to alkaline soil for nitrogen fixation and decrease the alkalinity of soil. Option C is incorrect. Water bloom constitutes layer of planktonic cyanobacteria/BGA, on the surface of waters rich in nutrients such as phosphate. Death of these BGA is followed by their decomposition by other bacteria which in turn leads to oxygen depletion and the death of other aquatic life forms. Thus, the correct answer is option B.
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