1. Carbon & Nitrogen Cycles

2. Recycling Matter All things living are made of matter
Total amount of matter on Earth is limited, so it must be recycled again and again for living things to survive
Both carbon and nitrogen get exchanged and recycled between living things and their environment

3. Carbon Cycle Carbon is the building block of all organic compounds
Ex: proteins, lipids, CHO’s, and nucleic acids
Sources of carbon form existing in abiotic world include:
- carbon dioxide gas
- bicarbonate (HCO3) dissolved in water
- fossil fuels
- carbonate rocks (limestone)
- dead organic matter in soil
- methane from wetlands, landfills, livestock

4. Carbon Cycle Steps of the carbon cycle
1. Plants take in carbon dioxide from the atmosphere to use in photosynthesis
2. Plants and animals release carbon dioxide into the atmosphere through cellular respiration
2b. Decomposers will break down dead plants and animals and release carbon and carbon dioxide into the soil- adds to carbon cycle

5. Carbon Cycle

7. Human Interaction
Humans contribute to the carbon cycle also in a process of combustion or burning.
Combustion uses oxygen to break down organic molecules to obtain the energy they contain
-results in release of carbon dioxide that accumulates in the atmosphere
*Scientists fear this will create widespread “greenhouse effect” that will lead to global warming

8. Nitrogen Cycle
Nitrogen, like carbon, is important in building organic compounds such as proteins and nucleic acids
78% of the Earth’s atmosphere is nitrogen gas, but most organisms cannot use this form of nitrogen to make the molecules they need.

9. Nitrogen Cycle
Steps of the nitrogen cycle: 1. Nitrogen in the atmosphere enters the soil. 2. Bacteria in the soil and on plant roots change nitrogen gas into a form that plants can use : Nitrogen fixation -convert N2 into ammonia (NH3) Nitrification -convert ammonia to Nitrates (NO3) and nitrites (NO2) proteins

10. Nitrogen Cycle
Steps (continued): 3. Animals get the nitrogen they need by eating plants or other animals that eat plants 4. Decomposers break down dead plants and animals to release nitrogen gas back into the atmosphere -convert nitrates into N2 gas (denitrification)

11. Nitrogen Cycle

12. Nitrogen Cycle
Without bacteria to fix nitrogen most plants would not be able to get nitrogen into usable form
Some plants have developed a mutualistic relationship with bacteria
- bacteria live on the plant roots and get nutrients
- plant gets fixed nitrogen from the bacteria
Ex: beans, peas, and alfalfa