Biology
Give scientific reasons for the following statements:
(i) Use of CFC is banned in many countries.
(ii) We cannot distinguish colours in moonlight.
(iii) Balsam plants wilt during mid-day even if the soil is well watered.
(iv) Carbon monoxide is highly dangerous when inhaled.
(v) A person after consuming alcohol walks clumsily.
Pollution
ICSE 2014
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Answer
(i) Chlorofluorocarbons (CFC) are one of the major causes for ozone depletion. Hence they are banned in many countries.
(ii) Cone cells in the retina are responsible for colour vision. They are functional only in bright light. Moon light is unable to stimulate the cone cells. However, the rod cells respond to dim light. Hence, we can see in moon light but cannot distinguish colours.
(iii) In case of balsam plants, the rate of transpiration during mid-day exceeds the rate of absorption of water by the roots. The cells therefore lose turgidity. In the evening or during the night, the stomata are constricted and the temperature is not very high. Therefore, there is no loss of water through transpiration, and the turgidity of the leaves is re-acquired.
(iv) Haemoglobin has very strong affinity for Carbon Monoxide forming a stable compound Carboxyhaemoglobin (HbCO). This cuts down the capacity of the blood of transporting Oxygen, sometimes resulting in death. Hence, Carbon monoxide is highly dangerous when inhaled.
(v) Alcohol affects the cerebellum part of the brain which is responsible for muscular co-ordination. So after consuming alcohol the cerebellum is unable to coordinate muscular movements properly resulting in the person walking clumsily.
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