1. Check In HW and Set Up 5 Yeast Dilutions

2. Sentinel Species?

8. Warwick E. Kerr

10. Sentinels of Global Warming?

11. Biogeochemical Cycles

12. How do biogeochemical cycles reflect the 1 st law of thermodynamics?

13. Nutrient Cycles Materials necessary to build tissues and carry out essential life functions Examples: Carbon, Phosphorus, Nitrogen

14. HYDROLOGIC CYCLE Evaporation Condensation Powered by solar radiation

16. Primary Productivity v. Rainfall

17. Carbon Cycle Appx. 49,000 metric gigatons of carbon on Earth and in atmosphere 71% in ocean 22% fossilized 3% in dead matter 2% in live matter 1% in atmosphere

19. Mutualism & The Carbon Cycle Photosynthesis “fixes” gaseous carbon (in form of CO 2 ) into a more stable form (glucose/C 6 H 12 O 6 ) Cellular Respiration releases carbon in form of CO 2

20. A Precarious Balance CO 2 is only a small fragment of the atmosphere (0.04%) Less than 2% of the world’s CO 2 comes from burning fossil fuels YET, the carbon cycle is rapidly becoming unbalanced in its ability to absorb the increases in CO 2

22. NITROGEN CYCLE 78% of atmosphere is DIATOMIC NITROGEN (N 2 ) N 2 is essentially useless to living organisms as the triple covalent bonds between nitrogen atoms make it chemically inert To “liberate” nitrogen it must be chemically reacted with other atoms

23. ABIOTIC NITROGEN FIXATION High energy reactions like lightning and vulcanism can break the triple bonds of N 2 Liberated nitrogen reacts with oxygen to create Nitrate (NO 3 ) and Nitrite (NO 2 )

24. BIOTIC NITROGEN FIXATION Rhizobium bacteria use the enzyme nitrogenase to break apart N2 in the absence of oxygen To isolate themselves from oxygen, Rhizobium live in nodules on legumes

27. Phosphorus & Algal Blooms Excess phosphorus in aquatic ecosystems allows for algal populations to increase drastically by raising the carrying capacity However, biological oxygen demand becomes too high and system crashes