The Carbon Cycle

Why is Carbon important? All living things are made of carbon!!! Calcium carbonate (CaCO3) makes up animal skeletons Carbon Dioxide gas which makes photosynthesis and respiration work together

Carbon Does Not Stay Still – It Is On the Move! In the atmosphere, carbon is attached to some oxygen in a gas called carbon dioxide. Plants use carbon dioxide and sunlight to make their own food and grow. The carbon becomes part of the plant. Animals consume plants. The carbon becomes part of the animal. Plants that die and are buried may turn into fossil fuels made of carbon like coal and oil over millions of years. When humans burn fossil fuels, most of the carbon quickly enters the atmosphere as carbon dioxide.

PHOTOSYNTHESIS + → + (C6H12O6 ) (CO2) (H2O) (O2) Using light energy, plants combine carbon dioxide (CO2) from the atmosphere and water (H20) to form sugar and oxygen in the process of photosynthesis. + → + sunlight (C6H12O6 ) (CO2) (H2O) (O2) What is Sugar (Glucose) Used For? 1. Source of energy 2. Building block for other compounds such as proteins, oils, and starches.

RESPIRATION In respiration, the compounds containing carbon (the organic compounds) are broken down, and carbon dioxide is released. Plants, animals, and microorganisms all carry out respiration!

IS THE CARBON-OXYGEN CYCLE BALANCED? The Carbon-Oxygen cycle is out of balance. There is more carbon dioxide being released into the atmosphere than is being removed.

COMBUSTION Most of the carbon dioxide is produced during the process of burning called combustion. When compounds containing carbon (wood, coal, or oil) are burned, the carbon is chemically combined with oxygen, and carbon dioxide is released.

The use of carbon dioxide by plants during photosynthesis is a much slower process. As a result of the imbalance between these two processes, the level of carbon dioxide in the atmosphere is increasing.

“Even if human emissions of CO2 magically dropped to zero, the gas already in the air would linger for many centuries, trapping heat. Global temperatures would continue to creep upward until the ocean depths reached equilibrium with the heated air, until biological systems finished adapting to the new conditions, and until Arctic icecaps melted back to their own equilibrium”

Decomposers When organisms die, decomposers break down the carbon compounds in their bodies, and carbon dioxide is returned to the atmosphere. During decomposition (decay), other chemicals are also returned to the soil or released into the air. One of these chemicals is nitrogen.

The Nitrogen Cycle

NITROGEN Plants and animals need nitrogen to make amino acids (proteins) The atmosphere is about 78% nitrogen gas, but plants and animals cannot use nitrogen directly from the air.

How Do Plants Get Nitrogen? Special bacteria, in the soil and water, must change or “fix” nitrogen gas (N2) into nitrogen fertilizers (NO3-) or ammonium ions (NH4+) that plants can use. These bacteria are called nitrogen-fixers. N=N → 2NH3

Nitrogen Fixers Most nitrogen-fixing bacteria live in little houses, or nodules, on the roots of plants called legumes. Legumes - members of a large family of plants that include peas, beans, alfafa, and clover. Convert nitrogen gas to ammonia

Nitrogen Fixers Mutualistic Relationship The plants provide food and cover for the bacteria, and the bacteria convert nitrogen gas into fertilizer for the plant.

How Do Animals Get Nitrogen? Animals get nitrogen from plants or from other plant-eating animals, in the form of protein. Animals must eat protein to get our nitrogen requirements! We can’t breathe in nitrogen.

How is Nitrogen Recycled? Bacteria in the soil (legumes) convert Nitrogen gas into ammonia. Other bacteria convert nitrogen to nitrates/nitrites. These nitrites get used by producers to make proteins. Consumers then eat the plants reusing the nitrogen to make their proteins. Nitrogen is recycled by special bacteria (legumes) that break down the nitrogen compounds (proteins) in dead plants and animals, and in animal wastes.

If plants do not use the nitrogen compounds as fertilizer, special forms of bacteria may recycle it. These bacteria convert the unused fertilizer into nitrogen gas and release it into the atmosphere.

All natural ecosystems depend upon bacteria to keep the nitrogen cycle going!

Lightning and the Nitrogen Cycle Lightning plays a small role in the nitrogen cycle. The high temperature and pressure from lightning combines nitrogen and oxygen (nitrogen oxides) in the atmosphere. The “fixed” nitrogen, (which is dissolved in the rain making nitrates) enters the soil