1. Nutrient Cycles
Chapter 16: Ecosystems

2. I. Biogeochemical Cycles
a. a.k.a. nutrient cycles
b. Nature does not throw anything away
c. Cycle – the path from nonliving environments to living organisms and then back to the nonliving environments again
d. Energy and nutrients move through the trophic levels together.

3. I. Biogeochemical Cycles
e. Energy and nutrients move differently through the biosphere
f. Nutrients are used over and over by living systems – recycled!
g. Recycled nutrients include: water, carbon, nitrogen, sulfur, calcium, & phosphorus

4. II. The Water Cycle
a. Begins with water vapor in the atomosphere condensing and falling to the ground as rain or snow
b. Condensation – changing from a vapor (gas) form into a liquid or solid form
c. Some water is stored as ground water – water retained beneath the surface of the Earth that supplies wells and springs

5. II. The Water Cycle
d. Remaining water is heated by the sun and re-enters the atmosphere through evaporation and transpiration
Evaporation – changing from liquid form into gas (vapor) form
Transpiration – the evaporation of water from plant leaves

6. II. The Water Cycle

7. III. The Carbon Cycle
a. The movement of carbon through the environment
b. Carbon dioxide in the air or dissolved in water is used by photosynthetic plants to build organic molecules
c. Carbon atoms return to the air and water three main ways:
i. Respiration – the use of oxygen to make organic molecules during cellular respiration; carbon dioxide is a by-product of this reaction

8. III. The Carbon Cycle
c. Carbon atoms return to the air and water three main ways:
ii. Combustion – the burning of carbon stored in wood or fossil fuels (coal, oil, and natural gas)

9. III. The Carbon Cycle
c. Carbon atoms return to the air and water three main ways:
iii. Erosion – the breakdown of limestone which releases stored carbon; limestone is formed from the shells of dead organisms built into sediments over millions of years

10. III. The Carbon Cycle

11. IV. The Nitrogen Cycle
a. The movement of nitrogen through the environment.
b. The atmosphere is about 78% nitrogen gas
c. Nitrogen – needed to build proteins (muscle is protein) and nucleic acids
d. Nitrogen fixation – changing free N2 in the atmosphere into compounds; soil microorganisms combining nitrogen with hydrogen to form ammonia

12. IV. The Nitrogen Cycle
e. The nitrogen cycle has four important stages:
i. Assimilation – absorption and incorporation of nitrogen into organic compounds by plants
ii. Ammonification – the production of ammonia by bacteria during the decay of organic matter
iii. Nitrification – the production of nitrate from ammonia
iv. Denitrification – the conversion of nitrate into nitrogen gas

13. IV. The Nitrogen Cycle

14. V. The Phosphorus Cycle
a. Phosphorus – essential parts of both ATP and DNA; present in soil and rock as calcium phosphate, which dissolves in water to form phosphate ions
b. Phosphate is absorbed by plant roots which is the eaten by animals and reused

15. The Phosphorus Cycle