Carbon Cycle Review

1. What are ways humans contribute to the carbon cycle?

2. What types of organisms uses carbon dioxide and produces oxygen?

3. What process is used by the organisms talking in the carbon dioxide?

Nitrogen Cycle Review

1. How does nitrogen become usable on earth?

2. How do nitrogen-fixing bacteria on root nodules function in the nitrogen cycle?

3. What organisms are involved in the movement of nitrogen between the air and soil, and then back to the air?

please help

Carbon Cycle

1. Humans are moving more carbon into the atmosphere from other parts of the Earth system. More carbon is moving to the atmosphere when fossil fuels, like coal and oil, are burned. More carbon is moving to the atmosphere as humans get rid of forests by burning the trees.

2. Plants produce oxygen, a gas that animals and other living things need. Animals and other living things produce carbon dioxide, a gas that plants need to make their own food. Plants make their own food from sunlight in a process called photosynthesis.

3. This process is called photosynthesis. The word photosynthesis comes from Greek words that mean “putting together by light.” During photosynthesis, algae and plants use sunlight to convert carbon dioxide and water into “food” or sugar (glucose) and oxygen.

Nitrogen Cycle

1. The molecules of nitrogen in the atmosphere can become usable for living things when they are broken apart during lightning strikes or fires, by certain types of bacteria, or by bacteria associated with bean plants. ... When organisms die, their bodies decompose bringing the nitrogen into soil on land or into ocean water.

2. The symbiotic nitrogen-fixing bacteria invade the root hairs of host plants, where they multiply and stimulate formation of root nodules, enlargements of plant cells and bacteria in intimate association. Within the nodules the bacteria convert free nitrogen to ammonia, which the host plant utilizes for its development.

3. Still other bacteria, called denitrifying bacteria, convert some of the nitrates in soil back into nitrogen gas in a process called denitrification. The process is the opposite of nitrogen fixation. Denitrification returns nitrogen gas back to the atmosphere, where it can continue the nitrogen cycle.

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