Transcript Lecture 33

I. Cycling (Chap 37.18-21)
A. Circular flow of nutrients, carbon, and water
B. Water cycle (34.17)
1. environmental
evaporation  water vapor  rain
2. organismal
a. root uptake
b. transpiration (evaporation from leaves)
- increased by sun and wind
c. responsible for some rain in dense forest ecosystems
3. ground water
- aquifers
- difficult to clean up
C. Carbon cycle (CO2)
1. photosynthesis
- use C in CO2 to build organic molecules
2. cellular respiration
- get energy by stripping C off of organic molecules
- CO2 returned to the atmosphere
3. combustion
- wood
- fossil fuels
C. Nitrogen cycle
1. abundant in atmosphere as N2
- must be “fixed” to NO3- or NH4+
- nitrogen-fixing soil bacteria
2. fertilizers
- manufactured types often exceed soil capacity
- potentially dangerous runoff
E. Phosphorus cycle
1. need P for
ATP, nucleic acids, phospholipids, bones
2. CaHPO4 in rocks and soil  PO43- in water
- taken up by producers
3. phosphate ion levels usually low in fresh water
- impacted by sewage, fertilizer, and pesticides
4.  phosphate  overgrowth of producers
a. overgrown organisms die
b. decomposers then overgrow and use up the O2
c. eutrophication
II. Weather Effects on Ecosystems (Chap 34.5)
II. Weather Effects on Ecosystems (Chap 34.5)
A. Latitudes and rainfall
1. six air masses
- cool air holds less water vapor
2. air rises from equator and moves toward poles
a. warm air loses water on the way up as it cools
b. cool air comes down, warms up, and soaks up water vapor
3. alternates every 30˚ of latitude
B. Ocean currents
- combination of prevailing winds, planet rotation, and solar heating
C. Elevation effects
- decrease of around 6˚C for every 1,000 meter increase
- can mimic effect of moving north or south from equator
D. Rain shadow
1. air cooled as it is forced to rise with a mountain
2. ability to hold water vapor is decreased
- results in precipitation
3. leeward side of mountain receives air devoid of moisture
- Death Valley
III. Ocean Ecosystems (Chapter 34.6)
A. Shallow waters
1. small part of the ocean
2. large number of species
3. includes intertidal region
4. estuaries
a. partly enclosed
- river mouths, coastal bays
b. intermediate salinity
c. very fertile
5. wetlands
- transition between aquatic and terrestrial ecosystems
B. Open ocean surface (pelagic zone)
1. most light is in first 100 meters (photic zone)
2. phytoplankton
a. microscopic algae
b. cyanobacteria
c. around 40% of earth’s photosynthesis
C. Sea floor (benthic zone)
1. not enough light for photosynthesis (aphotic zone)
2. many feed on organic “debris”
3. some are bioluminescent
- communication
- attract prey
4. hydrothermal vent communities
IV. Freshwater ecosystems (Chap 34.7)
A. Strong link to surrounding land
B. Depth zoning similar to oceans
- photic and aphotic zones
C. Overturns
- water is most dense at 4˚C