1. Biogeochemical Cycles: the exchange of matter through the biosphere
Water Cycle
Nitrogen Cycle
Carbon Cycle

2. Water Cycle

3. Water Cycle All living organisms require fresh water
Freshwater constitutes only about 3% all water on Earth

4. Water Cycle
Evaporation: water molecules break free from oceans and lakes
Purifies water
Transpiration: a process in which water evaporates from the surface of plants

5. Condensation: H2O molecules rise in the atmosphere—cool—slow down
Falls to Earth as precipitate (rain, snow, etc)
Percolation: water is purified through filtration when it trickles through loose soil

6. H2O carried from lakes to oceans by streams, run-off (on ground) flows into lakes and oceans, ground water travels under ground to oceans
H2O is also given off by living organisms—transpiration, perspiration, urination

7. Run off: water on the surface
that usually occurs when the land
is saturated or melting occurs
Ground water: water under the ground
that occurs when rain
infiltrates the soil

8. Nitrogen Cycle

9. Nitrogen Cycle
All living organisms need nitrogen to make proteins (for growth and repair)
The atmosphere is 78% nitrogen gas (N2) but plants and animals cannot use N2 in this form

10. Nitrogen must be “fixed” to oxygen in order for plants to absorb it and to benefit an ecosystem
. Nitrification: the capture and conversion of nitrogen into a form that is useable by plants

11. How is Nitrogen Fixed into a Usable Form?
Nitrogen is “fixed” in the following ways:
5-10% of N2 is “fixed” by lightning
Lightning splits bonds between N2 and N bonds with O2
90% of N2 is “fixed” by bacteria found in the roots of legumes (pea, soybean, peanut plants)

12. Man “fixes” nitrogen in fertilizer and introduces it to the ecosystem

13. Plants use these nitrogen compounds (specifically nitrates NO3) to make protein
Animals eat plants and use the plants’ protein to make their own protein
Animal passes waste or dies and releases nitrogen compounds into the soil

14. Nitrogen compounds go back into the soil where bacteria break it back into N2 gas
Denitrification: the process of (different) bacteria breaking down nitrogen compounds (such as ammonia) back into N2 gas (no longer useable for plants)

15. Carbon Cycle

16. Carbon Cycle Carbon Dioxide gas (CO2) is in the atmosphere
Large reserves in oceans—dissolved in
limestone deposits

17. Plants take in CO2 during photosynthesis
6 CO2 + 6 H2O + (light) → C6H12O6 + 6 O2
6 carbon dioxide + 6 molecules of water produce one molecule of sugar + 6 molecules of oxygen

18. Animals take in O2 and glucose and give off CO2 and H2O
CO2 goes back into the atmosphere
Cellular respiration

19. Plant dies and is buried for millions of years
Fossil fuels form
Man extracts and burns fossil fuels releasing CO2 into the atmosphere