4th Class Science Plants Question Bank Plants

  • question_answer                         The given graph shows different levels of oxygen in the air at different times in a park. Which point (W, X, Y or Z) on the graph, shows the level of oxygen in the air at night?

    A)  W                               

    B)  X                    

    C)  Y                    

    D)         Z

    Correct Answer: C

    Solution :

    Plants give out\[C{{O}_{2}}\]and take in\[{{O}_{2}}\]during respiration whereas they give out\[{{O}_{2}}\]and take in \[C{{O}_{2}}\]during photosynthesis. At daytime photosynthesis exceeds respiration hence\[{{O}_{2}}\]is released but at night photosynthesis stops and \[C{{O}_{2}}\]is released from plants. That is why level of oxygen will decline during night. In the given graphs, 'Y' shows concentration of \[{{O}_{2}}\]in the air at night.


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