Chapter 13: Energy and Nutrients

1. Chapter 13: Energy and Nutrients Section 13-3: Nutrient Cycles

2. What are NUTRIENTS? • Any substance that can be used for energy or to make living tissues. • Autotrophs manufacture carbohydrates, lipids, and proteins from chemical nutrients like water, carbon dioxide, nitrogen, phosphorus, and potassium.

3. Nutrients • Heterotrophs get their nutrients from eating other organisms because they cannot manufacture their own • Once consumed, nutrients can be broken down, rearranged, or used (including vitamins and minerals) • Nutrients move through trophic levels like energy

4. Nutrient Cycles • Unlike energy, nutrients CAN be recycled • Nutrients that are available in fixed quantities on Earth are passed from one organism to the another and from one part of the biosphere to another in pathways called nutrient cycles. • Energy flows in one direction, but nutrients can be incorporated into living tissues or given off in waste.

5. The Water Cycle

6. The Nitrogen Cycle • Refer to textbook 294 • Nitrogen gas makes up 80% of our atmosphere • In living things, it is found in amino acids and nucleic acids • The nitrogen cycle is the process of converting atmospheric nitrogen (N2) into usable forms for living things

7. Step 1: Nitrogen Fixation • Atmospheric nitrogen gas (N2) is converted into forms that producers can use in a process called nitrogen fixation • Nitrogen fixation can be carried out by bacteria and by lightening • Nitrogen can also be added to the soil directly through the use of fertilizers

8. Step 2: Absorption by autotrophs • The fixed nitrogen is absorbed by autotrophs • Autotrophs use the nitrogen to make amino acids

9. Step 3: Transfer to heterotrophs • Heterotrophs get nitrogen from the food they eat • Use this nitrogen to produce their own proteins

10. Step 4: Nitrogen returned to soil • Given off in the wastes of animals and reused by plants. • When an organism dies, decomposers (bacteria) break down its tissues and returns the nitrogen to the soil • Plants can then use the nitrogen, and the cycle begins again

11. Step 5: Denitrification • Nitrogen is returned to the atmosphere by denitrification • Bacteria in the soil convert “fixed” nitrogen back into nitrogen gas (N2)

12. The Carbon Cycle • Refer to textbook page 295 • There are three sources of carbon on Earth: • In the atmosphere as CO2 • In the oceans as dissolved CO2 • Underground as coal, petroleum, and calcium carbonate rock.

13. Step 1: CO2 enters the atmosphere • Released by organisms as a byproduct of respiration • Volcanic eruptions give off vaporized calcium carbonate rocks • Fossil fuels are burned • Terrestrial plants are burned • Diffuses from oceans (in equilibrium)

14. Step 2: CO2 removed from atmosphere • Autotrophs remove CO2 from atmosphere through photosynthesis • It gets incorporated into sugars

15. Step 3: CO2 is stored underground • When organic matter is buried underground for millions of years it is converted to coal, oil, gas • These are fossil fuels

16. Oceans and Carbon • Marine autotrophs remove CO2 from the water by photosynthesis • CO2 is returned to the water by respiration of marine organisms • Carbon as calcium carbonate makes up the shells of plankton and is found in coral, clams, oysters