Oxygen Cycle

Q.

Why does all the oxygen of atmosphere not get used up?

1. There is enough oxygen for all the organisms.

2. Not all organisms consume oxygen.

3. The carbon dioxide released by living organisms reacts with air to produce oxygen.

4. The balance of oxygen and carbon dioxide in the atmosphere is maintained by plants and animals.

Q. By which natural process is the oxygen of air renewed?

Q.

Which of the choices can best fit in the boxes I and II given below?

1. I - carbon dioxide, II - oxygen

2. I - oxygen, II - respiration

3. I - respiration, II - carbon dioxide

4. I - respiration, II - oxygen

Q.

Oxygen cycle maintains the air composition on the earth.

1. True
2. False

Q. In Plants, respiration occurs
(a) during the day only.
(b) during the night only.
(c) during day and night.
(d) only when photosynthesis does not take place.

Q.

Oxygen is returned to the atmosphere mainly by:

1. Burning of fossil fuel

2. Respiration

3. Photosynthesis

4. Fungi

Q. why green leaves and other green parts of a plant are not used to demonstrate the process of respiration

Q.

Oxygen is returned to the atmosphere mainly by___.

1. Respiration

2. Thunder storm

3. Photosynthesis

4. Burning of fossil fuels