How do ecosystems work? Part 2! Chapter 41

How does increased CO2 cause global warming? Greenhouse effect: Certain gases in the atmosphere (water vapor, methane, CO2 ) 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…

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

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

Shift in penguin species on the Antarctic Peninsula

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…

Nitrogen cycle (preview)

Nitrogen cycle: Nitrogen fixation The atmosphere is earth’s major nitrogen reservoir N2 gas not directly usable by producers Nitrogen fixation converts N2 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.

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

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

Nitrogen cycle (review)

Phosphorous cycle (preview)

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

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

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!

Phosphorous cycle (review)

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