1. How do ecosystems work? Part 2! Chapter 41

2. How does increased CO 2 cause global warming?  Greenhouse effect: Certain gases in the atmosphere (water vapor, methane, CO 2 ) absorb heat. More greenhouse gases  more trapped heat  Earth does need some greenhouse gases! Without any heat-absorbing molecules, the earth would be too cold for life! But we are now overheating the earth…

3. Some potential impacts of global warming  Melting of ice  sea level rise Some low-lying islands have already been inundated  Changes in weather patterns Droughts in some places, floods in others Shift in agricultural centers (loss of some, gain of others)  Increased hurricane intensity  Shifts in species distribution Example 1: Mosquitoes that carry Plasmodium (the malaria parasite)  How have they shifted? (Think about logically, considering they are found in warm climates…) Example 2: Penguins in the Antarctic

4. Focus: Antarctic penguins Gentoo penguins (Photo: B. Grunewald) Adelie penguins (Photo: K. Haberman) Chinstrap penguin (Photo: Shir Goldberg

5. Shift in penguin species on the Antarctic Peninsula

6. What can you do???  Overall, reduce use of fossil fuels.  Buy energy efficient appliances.  Line dry your clothes.  BUY LOCALLY! Shipping of products around the world uses a great deal of fossil fuels.  Buy certified organic food (minimal use of fertilizers that use fossil fuels to make.)  Invest in alternative, renewable energy.  Vote wisely…

7. Nitrogen cycle (preview)

8. Nitrogen cycle: Nitrogen fixation  The atmosphere is earth’s major nitrogen reservoir N2 gas not directly usable by producers  Nitrogen fixation converts N 2 to usable nitrogen forms (ammonia and nitrate) Lightning fixes nitrogen Bacteria fix nitrogen Humans fix nitrogen via chemical processing to make fertilizers or by burning fossil fuels.

9. Nitrogen cycle: Cycling through food webs  Primary producers take up ammonia and nitrate Convert to organic nitrogen (part of protein & DNA molecules)  Consumers feed on producers Gain organic molecules with nitrogen  Bacteria decompose dead organisms Convert back into inorganic forms that can be taken up by producers

10. Nitrogen cycle: Denitrification  Denitrifying bacteria convert nitrates and ammonia back into atmospheric nitrogen

11. Nitrogen cycle (review)

12. Phosphorous cycle (preview)

13. Phosphorous cycle: How does phosphorous enter ecosystems?  Phosphorous comes from rocks (reservoir for phosphorous)  Weathering of rocks and runoff moves phosphorous into ecosystems  Human-synthesized phosphorous (as phosphates) are also applied to crops

14. Phosphorous cycle: Cycling through food webs  Primary producers take up phosphorous Convert inorganic phosphates to organic phosphorous (part of protein, lipid & DNA molecules)  Consumers feed on producers (arrow missing in diagram!) Gain organic molecules with phosphorous  Bacteria decompose dead organisms Convert back into inorganic forms that can be taken up by producers

15. Phosphorous cycle: Loss of phosphorous from ecosystems  Phosphorous ends up in aquatic sediments (such as deep ocean) Will only be reintroduced with uplifting of mountains!

16. Phosphorous cycle (review)

17. Phosphorous and aquatic ecosystems  Agricultural and domestic runoff puts excessive amounts of phosphorous into aquatic ecosystems Intense blooms of phytoplankton Often these are toxic species Why? Dead zones: Too much phytoplankton at once  All dies at once  bacterial decomposition of excess phytoplankton reduces oxygen  animals die…  Clean Water Act (1977) Reduction of phosphate-based detergents has decreased this problem in some places