Final answer:
The atmosphere is the gaseous layer that surrounds the Earth and contains a mixture of gases, including nitrogen and oxygen. The troposphere is the lowest level of the atmosphere and plays a role in the Earth's climatic system.
Step-by-step explanation:
The atmosphere is the gaseous layer that surrounds the Earth. It is composed of a mixture of gases, including nitrogen (77 percent), oxygen (21 percent), and minor elements (1 percent) such as argon, helium, carbon dioxide, and water vapor. The atmosphere extends over three hundred miles above the Earth's surface and is divided into layers, with the troposphere being the lowest level responsible for the Earth's climatic system.