1. Nutrient Cycles
Lesson #5

2. Nutrient Cycles
Nutrients are chemicals required for plant and animal growth as well as other life processes.
Salts, amino acids, sugars, vitamins, etc.

3. Where are nutrients found?
Nutrients can be found just about anywhere.
Examples: land (soil), ocean, atmosphere, living organisms
These locations are called stores.
Nutrients can stay in a store for a short time or long time, and everywhere in between.

4. Nutrient Cycles
Nutrient cycles describe the flow of nutrients in and out of stores as a result of biotic and abiotic processes.
The three main nutrient cycles are:
Carbon Cycle
Nitrogen Cycle
Phosphorus Cycle

5. Carbon Cycle Carbon is the key element in all living things
Carbohydrates - source of energy
Proteins - structural parts of bodies
Fats/Lipids - insulation, long term energy store

6. Where do we find Carbon? Sources of Carbon Atmosphere Oceans
All living things
Fossil fuels
and many more places!

7. Where do we find Carbon?
Carbon reservoir – store carbon and release it slowly
Carbon sink – reservoirs that absorb more carbon than they release (ex. Oceans)

8. What is the Carbon Cycle?
The carbon cycle describes the process where carbon is recycled through ecosystems
Mostly through photosynthesis and cellular respiration.
Products of one are reactants for the other.
These processes keep the balance of O2 and CO2 in the biosphere.

9. Photosynthesis

10. Photosynthesis
Carbohydrates formed are passed through food chains and food webs.
Decomposition releases carbon into the soil
Carbon can be stores as fossil fuels and marine sediments

11. Cellular Respiration

12. Cellular Respiration Carbon is released back into the atmosphere
Carbon is also released from combustion of fossil fuels
Oxygen is also cycled through photosynthesis and cellular respiration

14. Nitrogen and Phosphorus Cycle
Lesson #3

15. Nutrient Cycles The three main nutrient cycles are: Carbon Cycle
Nitrogen Cycle
Phosphorus Cycle

16. Nitrogen Cycle
All living things need nitrogen to form nucleotides (DNA and RNA) and amino acids (proteins).
Nitrogen gas makes up 78% of the atmpsohere, but most organisms can’t break the strong bonds of N2 molecules so the nitrogen cycle is needed.

17. First Step - Nitrogen Fixation
A process carried out by nitrogen-fixing bacteria found in nodules on the roots of legumes such as peas, peanuts, and soybeans.
On average there is 100 lightening strikes worldwide per second, 8 million per year. National Severe Storms Laboratory

18. First Step - Nitrogen Fixation
Also in cyanobacteria and in lichens
Plants and bacteria have a symbiotic relationship
Nitrogen (N2) is fixed (combined with H2) to give ammonia (NH3)
Excess ammonia is dissolved in water as ammonium (NH4+) ions.
On average there is 100 lightening strikes worldwide per second, 8 million per year. National Severe Storms Laboratory

19. Second Step - Nitrification
A process where nitrate (NO3-) ions are produced from ammonium by bacteria in soils
Plants need both NH4+ ions and NO3- ions to grow
Plants use nitrates to make amino acids and DNA.
Animals get amino acids by digesting plant proteins and nucleic acids, and remake their own proteins and DNA.

20. Third Step - Denitrification
When organisms produce waste or die and decompose, the material are broken down to release ammonium and nitrates.
Anaerobic bacteria convert ammonium and nitrate back to nitrogen gas.
This process speeds up in low oxygen, acidic environments such as peat bogs

22. Nutrient Cycles The three main nutrient cycles are: Carbon Cycle
Nitrogen Cycle
Phosphorus Cycle

23. Phosphorus Cycle
Phosphates are important molecules in living things DNA and RNA have sugar phosphate backbones.
Animals have phosphates in shells, bones and teeth.
Cell membranes are made of phospholipids (fat molecules)
Energy in all organisms stored in ATP (adenosine triphosphate).

24. Phosphorus Cycle
All phosphate originates from weathering of sedimentary and metamorphic rocks.
There is no phosphate in the atmosphere!
Phosphate ions dissolve in water, get absorbed by producers then eaten by consumers.

25. Short Cycle
When organisms die and decompose the phosphates are released and dissolve in water and are available to producers again.

26. Long Cycle
When organisms die and decompose in the ocean, the phosphates and other elements sink to the bottom and are covered in sediments
These sediments eventually become sedimentary rocks and the phosphates remain trapped until a geological event exposes them to weathering.

27. Human Impact on the Phosphorus Cycle
Human activities add phosphate to ecosystems in several ways
Commercial fertilizers
Animal manure used to enrich soil
Output from sewage treatment plants and industrial waste