1. The Cycling of Materials
Chapter 5
Section 2

2. The Cycling of Materials
THINK: What will happen to the next ball point pen you buy?
You will probably use it until its ink supply runs out and then throw it away.
The plastic and steel the pen is made of will probably never be reused.

3. The Cycling of Materials
Three natural cycles by which materials are used:
Carbon Cycle
Nitrogen Cycle
Phosphorus Cycle

4. The Carbon Cycle Carbon makes up all organisms
Proteins
Fats
Carbohydrates
The carbon cycle is a process by which carbon is cycled between the atmosphere, land, water, and organisms.

5. The Carbon Cycle – Short-term
Carbon enters a short-term cycle in an ecosystem when producers convert CO2 in the atmosphere into carbohydrates during photosynthesis.
When, consumers eat producers, they obtain carbon from the carbohydrates

6. The Carbon Cycle – Short-term
As consumers break down food during cellular respiration, some of the C is released back into the atmosphere as CO2
Organisms that make their own food through photosynthesis also release carbon dioxide during cellular respiration

7. The Carbon Cycle – Long-term
Some carbon enters a long-term cycle
For example, some of the carbon may be converted to carbonate, which makes up the hard parts of shells and bones
These do not break down easily
Over millions of years, these carbonate deposits have formed huge limestone rocks
Limestone is one of the largest carbon reservoirs on Earth.

8. The Carbon Cycle – Long - term
Carbohydrates in organisms are converted into fats, oils, and other molecules that store energy
This stored carbon may be released into the soil or air after the organism dies
These molecules can form deposits of coal, oil, and natural gas underground
Fossil Fuels

9. How do humans affect the carbon cycle?
Burning of fossil fuels greatly contributes to the amount of carbon dioxide in the atmosphere
In 2000, vehicles were the source of one-third of all carbon dioxide emitted in the United States
Forest Fires also contribute
The amount of CO2 in the atmosphere has been steadily increasing

10. How do humans affect the carbon cycle?
Increased levels of CO2 may contribute to Global Warming – an overall increase in the temperature of the Earth
What happens to all of the remaining carbon dioxide?
An estimated billion metric tons is dissolved into the ocean
Plants use the remaining CO2

11. Carbon Cycle

12. The Nitrogen Cycle
All organisms need nitrogen to build proteins, which are used to build new cells
Nitrogen makes up 78% of the gases in the atmosphere yet most organisms cannot use atmospheric nitrogen.
Instead, it must be altered or “fixed” by nitrogen-fixing bacteria

13. The Nitrogen Cycle
Nitrogen Cycle – a process in which nitrogen is cycled between the atmosphere, bacteria, and other organisms.

14. The Nitrogen Cycle
Nitrogen-fixing bacteria live in nodules on the roots of plants called legumes
Beans, peas, clovers
Bacteria use sugar provided by the legumes to produce nitrogen-containing compounds such as nitrates
The excess nitrogen is released into the soil

15. Decomposers and the Nitrogen Cycle
Decomposers are essential as they break down wastes and return the nitrogen that these wastes contain to the soil
Nitrogen cycles between organisms and the soil and is constantly reused

16. The Nitrogen Cycle

17. The Phosphorus Cycle
The Phosphorus Cycle is the movement of phosphorus from the environment to organisms and then back to the environment.
This cycle is slow and does not normally include the atmosphere because phosphorus rarely occurs as a gas.

18. The Phosphorus Cycle
Phosphorus reaches the soil and water in several ways:
When rocks erode, small amounts of phosphorus dissolve as phosphate
When excess phosphorus is excreted in waste from organisms
When organisms die and decompose

19. The Phosphorus Cycle

20. Fertilizers Fertilizers contain both Nitrogen and Phosphorus
Excess fertilizer in an aquatic ecosystem or nearby waterway can cause a rapid and overabundant growth of algae
Algal bloom – a dense, visible patch of algae that occurs near the surface of water.
Deplete the oxygen creating “dead zones”

21. Acid Precipitation
When we burn fuel, nitric oxide is released into the atmosphere
Combines with oxygen and water vapor in the atmosphere to form nitric acid – ACID RAIN!