NCERT VI Social Sciences

Answer the following questions.

(a) Name the constituents of air and give their proportion in air.
(b) Of what use is carbon dioxide to plants?
(c) What is meant by nitrogen fixation? How does it happen?
(d) Which measures are necessary for arresting pollution?
(e) What ill-effects of pollution are being seen?
(f) What function does an observatory perform?



(i) Nitrogen-78.08% Oxygen-20.95% Argon-0.93% Carbon dioxide-0.038% Krypton-0.0001% Helium-0.0005% Hydrogen-0.00005% Neon-0.0018% Xenon-0.000009% (ii)Carbon dioxide is used by the plants to make their food by the process of photosynthesis whereby the green plants make their own food with the help of water, sunlight and carbon dioxide and give out oxygen which is used for the process of respiration by animals. (iii)Nitrogen fixation is a chemical process in which atmospheric nitrogen is assimilated into organic compounds in living organisms and in nitrogen cycle. (iv)Plants designed 10 years or before or by lowly equipped designs are sure cases for detailed study. For prevention generous use of scrubbers & filters will be necessary. It is said that a routine check will reduce 10%, a minor modification will reduce 15-20% and a thorough overhauling of the system will reduce more than 30% of power consumption and pollution creation. (v)Acidification Eutrophication Ground-level ozone Particulate matter (vi)An observatory is a location used for observing terrestrial or celestial events. Astronomy, climatology/meteorology, geology, oceanography and volcanology are examples of disciplines for which observatories have been constructed.