People, animals and plants on the earth are absorbing oxygen and spitting out carbon dioxide all the time. Factories are even more large consumers of oxygen and carbon dioxide. In the long run, won't the earth run out of oxygen?
In the 19th century, British physicist Thomson Kelvin said with great concern: "with the development of industry and the increase of population, 500 years later, all the oxygen on the earth will be used up, and mankind will tend to perish!" Facts have proved that this concern is completely superfluous, and the earth will not run out of oxygen. Swiss scientist scheniber once did such an experiment: he collected the green leaves of many plants, soaked them in water and put them under the sun. The leaves soon kept spitting out small bubbles, and sheniper collected the gas with a test tube. What are these gases? When scheniber threw a piece of lighted wood into the test tube, the wood burned violently and gave a dazzling light. This means that there is oxygen in the test tube, because only oxygen can help combustion. Then, sheniper put carbon dioxide into the water. He found that the more carbon dioxide passed in, the more oxygen the green leaves emitted.
Shebney came to this conclusion: it turns out that under the sun, green plants will absorb carbon dioxide in the air and chemically react with the water inhaled from the roots to synthesize the nutrients they need and release oxygen at the same time, which is called "Photosynthesis". The total amount of oxygen released by plants through photosynthesis is about 20 times more than the oxygen required for respiration. In this way, oxygen will not be reduced in the air, and the oxygen content will always be maintained at 21%. At the same time, carbon dioxide is often maintained at 0.03%.
To sum up, the photosynthesis of plants will absorb carbon dioxide and release oxygen. We have a continuous supply of oxygen for breathing, but the reduction of plants will affect human survival. Therefore, we should protect plants.