1. Biogeochemical Pathways
Water Cycle
Carbon Cycle
Nitrogen Cycle
Phosphorus/Mineral Cycle

2. Water Cycle
Continuous movement of water into the air, onto land, and then back to water sources

3. Sources and Examples of Water
Solid
Polar ice caps, glaciers, icebergs
Liquid
Precipitation (rain, sleet, snow, hail): large droplets of water
Surface water: lakes, ponds, streams, rivers, oceans
Ground water
Condensation: water vapor that forms droplets on dust
Gas
Evaporation/ water vapor: liquid water heated by the sun and rises into the atmosphere
Transpiration: evaporation from leaves

4. Water Cycle: Human Impacts
Dams
Irrigation
Cooling
Ground water
Surface water

5. Water Cycle

6. Carbon Cycle
The process by which carbon is cycled between the atmosphere, land, water, and organisms.
Carbon is an essential component of proteins, fats, carbohydrates, and DNA which make up all organisms.

7. Carbon Cycle
Producers converts carbon dioxide (CO2) in the atmosphere into glucose (carbohydrates) during photosynthesis.
Consumers convert glucose that they obtain from eating producers into CO2 during cellular respiration.
Organisms that produce their own food through photosynthesis also release CO2 during cellular respiration.

8. Sources and Examples of Carbon
Decaying organisms
Combustion: the burning of fossil fuels
Respiration
Limestone
Oceans

9. Importance of Carbon
Carbon may be converted into carbonates which make up the hard parts of bones and shells.
They are not easy to break down.
After millions of years, carbonate deposits produce large formations of limestone rocks, which is one of the largest carbon sinks or carbon reservoirs on Earth.

10. Importance of Carbon
Some carbohydrates in organisms are converted into fats, oils, and other molecules that store energy.
When an organism dies, carbon can be released into the soil or air.
The stored carbon left over from the bodies of plants and animals that died millions of years ago can form fossil fuels (coal, oil, and natural gas) underground.

11. Carbon Cycle: Human Impacts
When we burn fossil fuels (combustion), it releases carbon into the air.
Natural burning of wood and forest fires as well as deforestation release carbon into the air.
Excess carbon is thought to cause climate change.

12. Carbon Cycle

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

14. Examples and Sources of Nitrogen
Animal waste
Fertilizers
Atmosphere (~ 78% nitrogen), but unusable to most living organisms
It’s like being thirsty at
The beach….you are surrounded by water and can’t drink
It! It’s not in a form that is usable!

15. Examples and Sources of Nitrogen
So, nitrogen must be fixed, or altered before organisms can use it!
Nitrogen-fixing bacteria on the root nodules of legumes

16. Nitrogen-Fixing Bacteria
Nitrogen fixing bacteria are bacteria that can fix atmospheric nitrogen into chemical compounds that organisms can use.
ALL other organisms depend upon these bacteria to supply nitrogen that they can use!
These bacteria live in nodules on roots of plants called legumes (beans, peas, clover)
The sugars in legumes produce compounds called nitrates. The left over nitrogen fixed by the legumes is released into the soil.

18. The root of a legume! See the nodules?
The nitrogen fixing bacteria
are in those nodules!

19. Nitrogen Cycle
Plants that DO NOT have nitrogen fixing bacteria get usable nitrogen from the soil.
Animals get nitrogen by eating plants and animals that have usable nitrogen in them.
Nitrification: The process of making
nitrogen into a form that is useful to plants

20. Nitrogen Cycle
Decomposers break down waste, leaves, plants and animals and return nitrogen back to the soil.
Some of the nitrogen returned back to the soil by decomposers get converted into nitrogen gas and goes back to the atmosphere.

21. Nitrogen Cycle Nitrogen is a key component in our cells.
Nitrogen helps to build proteins!

22. Nitrogen Cycle: Human Impacts
Fertilizers with nitrogen can cause eutrophication.
Erosion of nitrogen rich topsoil when vegetation is cleared.
Burning fossil fuels releases nitrogen oxides which is a cause of acid rain.

23. Nitrogen Cycle

24. Phosphorus/Mineral Cycle
The movement of phosphorus from the environment to organisms and back to the environment.

25. Examples and Sources of Phosphorus
Phosphorus enters ecosystems when rocks erode and dissolve in the water or soil.
Phosphorus can also be added through:
Animal waste
Decomposition
Runoff
fertilizers

26. Phosphorus Cycle
Phosphorus helps make up our DNA and is essential to from our bones and teeth!

27. Phosphorus Cycle Plants get phosphorus from the soil and water.
Animals get phosphorus by eating plants or other animals

28. Phosphorus Cycle: Human Impacts
Fertilizers with phosphorus can cause eutrophication.
Erosion of phosphorus rich topsoil when vegetation is cleared.

29. Phosphorus Cycle: Human Impacts

30. Phosphorus Cycle