Answer in Science (Guide Questions in LT 1):
1.) These layers are the troposphere, stratosphere, mesosphere and thermosphere.
2.) Without the atmosphere life as we know it would not be possible. The oxygen and carbon dioxide in the lower layers of the troposphere (that touches Earth) allow life to exist as organisms can respire and plants can photosynthesise. The atmosphere also helps to keep the Earth warm by trapping solar energy.
Answer in Science (LT 2):
3.) A greenhouse works by converting light energy into heat energy. Light rays from the sun enter the greenhouse, where they are absorbed by plants and objects and converted to heat
4.) When the Sun's energy reaches the Earth's atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases
5.) The added greenhouse gases absorb the heat. They then radiate this heat. Some of the heat will head away from the Earth, some of it will be absorbed by another greenhouse gas molecule, and some of it will wind up back at the planet's surface again. With more greenhouse gases, heat will stick around, warming the planet.
