| A | B |
|---|
| Volcanos change the atmosphere _____. | by adding large quantities of gas |
| CFC's are responsible for ______. | destroying the ozone layer |
| ______is very rare, is found in the atmosphere, is rare among other planets, and allows us to survive? | oxygen |
| The ozone layer protects us by _______. | blocking UV radiation |
| The most abundant gas in our atmosphere is ________. | nitrogen |
| _______ are a major source of oxygen in the Earth's atmosphere. | plants |
| Plants are able to provide oxygen through _______. | photosynthesis |
| _______happens in the troposphere. | Weather |
| The ozone layer is located in the ____. | stratosphere |
| The four layers of the atmosphere are divided by _____. | temperature differences |
| What happens to the temperature in the stratosphere? | it increases |
| The aurora borealis takes place in the ______. | thermosphere |
| Ozone forms ______when it reacts with automobile exhaust. | smog |
| Photosynthesizing cyanobacteria add ______ to the atmosphere. | oxygen |
| ________was the main cause of the atmosphereic changes that occurred during the Precambrian time period. | Vocanic outgassing |
| The hydrosphere consists of ________. | water |
| Too much exposure to ________causes skin cancer. | ultraviolet radiation |
| The thermosphere feels _____. | cold |
| The temperature in the thermosphere is cold because_______ | the hot molecules are far apart. |
| Nitrogen makes up ______ percent of the atmosphere. | 78 |
| Oxygen makes up ____ percent of the atmosphere. | 21 |
