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Environmental Issues — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYEnvironmental Issues5 Marks
Question
  1. The graph below represents the growth patterns of two types of aquatic organisms over a brief period of time in a water body, surrounded by agricultural land, extensively supplied with fertilisers. Identify the organisms that would represent: (i) A and (ii) B.
  2. State the reason for such a change in the water body and also write the term given to it.
✓

Answer

  1.  
  1. A. Planktonic Algae (algal growth): Due to large amount of nutrient free floating algae develops in lake (a water body).
  2. B. Fishes: Due to decrease in D.O. the fishes and other aquatic organisms die.
  1. Eutrophication (Algal bloom): The eutrophication is defined as the natural ageing of a lake (water body) by biological enrichment of its water." The reason for it is: a young water body (lake) has cold, clear, life supporting water. When it is supplied by fertilizers or some nutrient such as phosphorous as well as nitrogen are introduced in it; the growth of aquatic organisms takes place. Then the microbes consume lot of $O_2$.

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