SPM Biology 2018


9. Diagram 9.1 shows two human activities. Activity P and Activity Q that contribute to global warming.

Rajah 9.1 menunjukkan dua aktiviti manusia, Aktiviti P dan Aktiviti Q yang menyumbang kepada pemanasan global.

(a) Explain how these activities can cause global warming.

Terangkan bagaimana aktiviti tersebut boleh menyebabkan pemanasan global.

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(b) (i) Diagram 9.2 shows a graph of the world forest cover. The graph shows the changes of the world forest cover from the years 1990 to 2010. Suggest reasons why these changes happened to the world forest cover.

Rajah 9.2 menunjukkan sebuah graf litupan hutan. Graf menunjukkan perubahan litupan hutam dunia daripada tahun 1990 hingga 2010. Cadangkan sebab mengapa berlakunya perubahan kepada litupan hutan dunia.

(b) (ii) Describe the importance features of tropical rainforest.

Huraikan kepentingan ciri-ciri hutan hujan tropika.

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Answer ( 1 )


    9. a) Activity P is deforestation. Deforestation releases a lot of dust and carbon dioxide (CO2) into the air. Moreover, due to excessive logging, the number of trees would be lessened and thus carbon dioxide cannot be effectively removed from the atmosphere by photosynthesis. 

    Furthermore, Activity Q increases the concentration of CO2 in the atmosphere due to the combustion of fossil fuels used for car petrol. 

    Both these activities increases the release greenhouse gases such as CO2. An increase in the concentration of greenhouse gases, results in the greenhouse effect. Some solar radiation from sunlight gets reflected back into space, however most of it gets absorbed by the Earth.  Furthermore, due to the greenhouse gases, infrared radiation gets re-radiated back onto the Earth’s surface. Heat which is released also gets trapped in the atmosphere by these greenhouse gases. These processes, warm up the Earth and atmosphere. Resulting in the overall increase in the Earth’s and atmosphere’s average temperature, causing global warming to occur.


    b) i) One main reason for the reduction in world forest cover would be deforestation. Excessive logging for the use of wood in industries such as the production of furniture or paper. Moreover, due to the rise in world population numbers, forests get cleared for agricultural purposes to make more food and get cleared to build housing areas. Furthermore, air pollution by industries causes acid rain which affects the fertility of the soil due to leaching minerals. Acid rain also destroys photosynthetic tissues of plants and the roots of forest plants may get damaged.


    ii) Tropical rainforests are important as they provide a habitat for flora and fauna. Furthermore, they provide biological products such as food and medicine. Pharmaceutical industries may use products found in rainforests to make medicinal products. They are important areas for research as well. Rainforests also act as a carbon sink by absorbing an enormous amount of carbon dioxide from the atmosphere for photosynthesis. In return they release a lot of oxygen into the air. Thus, they help with the reduction of air pollutants like carbon dioxide. Another importance is that they act as water catchment areas.

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