1. Carbon, Nitrogen & Phosphorus Cycles Ch. 5.2

2. Carbon Cycle
The carbon cycle is the recycling of carbon between living and non-living things.
Carbon is found in all organic matter.
- Carbohydrates (Sugar, Glucose)
- Lipids (Fats + Oils)
- Proteins
- Genetic Material (DNA)

3. What role do plants play in the carbon cycle?
Carbon (especially in the form of CO2) can be found in all 4 of the spheres we talked about earlier…

4. Carbon cycle Carbon in the Biosphere
Plants use CO2 for photosynthesis.
Animals exhale CO2 back to the atmosphere.
Decomposing organisms return carbon to the soil (lithosphere).
Consumers obtain carbon from the carbohydrates in the producers they eat.

5. Carbon cycle Carbon in other spheres
CO2 is absorbed into Earth’s oceans.
Carbon deposits from millions of years ago form fossil fuels deep in the lithosphere.
Many scientists agree that CO2 in the atmosphere is a cause of global warming.

6. Nitrogen cycle, cont.

7. The Nitrogen Cycle
Over 75% of the gas in the atmosphere is Nitrogen (formula is N2). All living organisms need Nitrogen to make proteins, but N2 is not a usable form.
- Think about chewed gum… It’s still gum, but nobody wants to chew it anymore. You want a fresh package of gum instead.

8. Nitrogen cycle, cont.
Only a few species of bacteria can “fix” atmospheric nitrogen (N2) a different form that organisms can actually use. These guys are “nitrogen-fixing” bacteria.
Lightning can also act as a CATALYST for converting N2 to a usable form.

9. Decomposers and the Nitrogen Cycle
Nitrogen stored within the bodies of living things is returned to the nitrogen cycle once those organisms die. Decomposers are doing this.
Some bacteria in the soil actually converts the usable nitrogen back into N2. Wish they’d not do that so we can have more usable nitrogen, but whatever…

10. The Phosphorus Cycle
Phosphorus is an element that is part of many molecules that make up the cells of living organisms.
- DNA
- RNA
- ATP (the energy molecule)
Plants get the phosphorus they need from soil and water.
Animals get phosphorus by eating plants or other things that have eaten plants.

11. Phosphorus Cycle

12. Fertilizers and the Nitrogen and Phosphorus Cycles
Fertilizers, which people use to stimulate and maximize plant growth, contain both nitrogen and phosphorus.
Excessive amounts of fertilizer can enter terrestrial and aquatic ecosystems through runoff.
Excess nitrogen and phosphorus can cause rapid growth of algae.
Excess algae can deplete an aquatic ecosystem of important nutrients such as oxygen, on which fish and other aquatic organisms depend.