Explanation: Plants play a vital role in the Earth's ecosystem, particularly in the production of oxygen through the process of photosynthesis. Photosynthesis is a biochemical process in which plants use sunlight, water, and carbon dioxide to produce glucose and oxygen. The chemical equation for photosynthesis is:
\[ 6CO_2 + 6H_2O + light \rightarrow C_6H_{12}O_6 + 6O_2 \]
This equation shows that for every six molecules of carbon dioxide and six molecules of water, plants produce one molecule of glucose and six molecules of oxygen. The oxygen produced during photosynthesis is released into the atmosphere, which is essential for the survival of most living organisms, including humans, as it is required for cellular respiration.
If all plants were to vanish from Earth, the primary source of atmospheric oxygen would be eliminated. This would lead to a significant decrease in the oxygen levels in the atmosphere, which would have catastrophic effects on life on Earth. Most organisms, including humans, rely on oxygen for respiration, and a drastic reduction in oxygen levels would result in widespread suffocation and death.
While plants do absorb carbon dioxide during photosynthesis, they also release carbon dioxide during respiration. Therefore, the absence of plants would not result in the complete disappearance of carbon dioxide from the atmosphere. Other sources, such as volcanic activity and human activities, also contribute to carbon dioxide levels. Similarly, hydrogen is not a significant component of the atmosphere produced by plants. Hydrogen is primarily found in water and organic compounds, and its levels in the atmosphere are not significantly influenced by the presence or absence of plants.
Air is a mixture of gases, including nitrogen, oxygen, carbon dioxide, and others. While the absence of plants would affect the oxygen levels, it would not eliminate air entirely. Nitrogen, which makes up about 78% of the atmosphere, would still be present, along with other gases. However, the reduction in oxygen levels would have severe consequences for life on Earth.
In conclusion, the correct answer is that if all plants were to vanish from Earth, there would be no oxygen. This is because plants are the primary producers of oxygen through photosynthesis, and their absence would lead to a significant decrease in atmospheric oxygen levels, which is essential for the survival of most living organisms.