Question

The estimated production of oxygen by photochemical dissociation of water in the stratosphere is 1.5 g per metre sq. per year and by photosynthesis about ____ gm per sq. metre per year.
A. 500
B. 260
C. 300
D. 650

Answer 1

Hint: During photosynthesis water molecules break down by the photons of sunlight and form oxygen, which is then released to the atmosphere. This oxygen then helps in the survival of the whole animal world and also helps in aerobic respiration.

Step by step answer:The atmosphere or air layer around the earth is divided into certain spheres, these are – troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
The troposphere is the layer that starts from the earth’s surface and the exosphere is the farthest surface of air. The oxygen concentration decreases as the atmospheric layers are increased by the height – it means the troposphere has the highest concentration of oxygen and the exosphere has the lowest concentration of oxygen. In the region of earth’s stratosphere, an ozone layer is present, which protects the earth from the UV rays and cosmic rays that can enter the earth. But due to greenhouse gases, holes are seen in the ozone layer that results in global warming and climate change. By the photochemical dissociation of water, 1.5 g per metre sq. per year of oxygen is released to the stratospheric air.
The main biological procedure of oxygen production in photosynthesis. In this process, about 260 gm per sq. metre per year of oxygen is released in the atmosphere.
Thus, the correct answer is option B. 260 gm per sq. metre per year.

Note: In the atmosphere, the oxygen molecule is released by the process of photosynthesis and moves from troposphere to exosphere. In the stratosphere, photodissociation takes place where a chemical compound is broken by photons.