(a) What would happen if all the green plants disappear from the earth?
(b) If a plant is releasing carbon dioxide and taking in oxygen during the day, does it mean that there is no photosynthesis occurring? Justify your answer.

(a)  All the life forms on earth depend on plants directly or indirectly. Green plants provide food and oxygen to all other living organisms. If they disappear from the Earth, all other organisms will die due to starvation and lack of oxygen for respiration.

(b) If a plant is releasing carbon dioxide and taking in oxygen during the day, it does not mean that there is no photosynthesis taking place. Photosynthesis takes place only in the presence of light and hence, oxygen is released by plants only during the day. Plants carry out respiration throughout the day and night like other living beings. Hence, they keep on emitting carbon dioxide all the time.