Video Transcript
Which of the following charts shows the correct chemical composition of the
atmosphere?
The atmosphere is the layer of gases that surrounds the solid Earth. It provides protection from harmful solar rays and enables organisms to respire. The atmosphere formed over 4.5 billion years ago when the Earth first formed. It is thought that the atmosphere formed from gases from volcanic eruptions. Because of this volcanic activity, the early atmosphere initially contained high
quantities of carbon dioxide. As the oceans formed, they absorbed carbon dioxide, reducing its levels in the
atmosphere.
When photosynthesis started occurring, the percentage of carbon dioxide was further
decreased and the proportion of oxygen in the atmosphere increased. Presently, the air in the atmosphere is composed primarily of nitrogen, which makes
up 78 percent of the atmosphere. 21 percent of the atmosphere is composed of oxygen gas. The remaining one percent is made up of other gases, including carbon dioxide, argon,
hydrogen, and water vapor just to name a few.
So, in conclusion, the chart that shows the correct chemical composition of the
atmosphere is the chart shown in answer choice (B).
