12th Class Biology Sample Paper Biology - Sample Paper-15

  • question_answer
    (i) How ozone hole will affect our lives?
    (ii) Algal bloom is result of accelerated eutrophication. Explain.
    (iii) How is solid waste management being carried out?
    Or
    (i) State the consequences of the following components on the ecosystem.
    (a) all producers are removed.
    (b) all organisms of herbivore level are eliminated.
    (c) all top carnivores population is removed.
    (ii) Ecosystem services are the products of ecosystem process. Comment.

    Answer:

    (i) Depletion in the concentration of ozone over a restricted area as over Antarctica is called ozone hole. Depletion of ozone is due to action of sunlight over pollutants which release chemicals that destroy ozone. Thinning of ozone shield will increase the amount of UV-B radiation reaching the earth. These will result in skin cancer and more persons becoming blind.
    (ii) Cultural or Accelerated eutrophication is nutrient enrichment of water bodies due to human activities like passages of sewage, industrial effluents and runoff form fertilised fields rich in nitrates and phosphates. Nutrients present in sewage, agriculture wastes and fertilisers cause dense growth of plants and planktonic algae. They also supports a good number of animals. The excess growth of planktonic algae that causes colouration of water is called algal bloom.
    (iii) Methods of solid waste disposal There are following methods of solid waste disposal.
    (a) Open burning it involves burning of municipal waste in open dumps to reduce volume but the unburnt piled waste serves as breeding ground for rats and flies.
    (b) Sanitary landfills These are the areas, where wastes are dumped in a depression or trench after compaction and covered with dirt. These have been adopted as an alternative to open burning dumps. But seepage of chemicals from these landfills can pollute underground water resources.
    Or
    (i) (a) Removal of all producers will reduce primary production in the ecosystem. Hence, no biomass will be available to the successive/higher trophic level or heterotrophic organisms.
    (b) Elimination of all organisms of herbivore level results into an increase in primary productivity and biomass of producer. Carnivorous animals will not survive due to unavailability of herbivores.
    (c) Removal of cornivores also disturbs the ecosystem as it will result in huge increase in number of herbivores which will finish plants (producers) causing desertification.
    (ii) Healthy ecosystems are the base for a wide range of economic, environmental and aesthetic goods and services. Ecosystem processes, e.g. healthy forest ecosystem purifies air and wastes, mitigate droughts and floods, cycle nutrients. It generates fertile soils, provides wildlife habitat, maintains biodiversity, pollinate crops, provides storage site for carbon. It also provides aesthetic, cultural; and spiritual values.


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