Answer to Question 1
Carbon enters the atmosphere though the respiration of all living things as carbon dioxide. Volcanic eruptions and the burning of fossil fuels also send carbon back to into the atmosphere.
An increase of carbon dioxide into the atmosphere creates an increase in surface temperatures. This is due to the greenhouse effect.
Photosynthetic organisms capture sunlight to fix carbon dioxide into organic molecules that can be used.
When primary consumers eat producers, they are able to obtain and use some of the converted carbon. It can be incorporated into an animal's body for growth. Some of the carbon will be respired out or excreted by the organism.
Dissolved organic carbon is excreted back into seawater. Then the whole cycle starts over again.
Answer to Question 2
A