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)

Adelie penguins (Photo: K. Haberman)

Chinstrap penguin (Photo: Shir Goldberg

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