ecosystems energy flow 2. chemical cycles water, carbon, nitrogen 3. human effects on cycles
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Ecosystems Energy Flow 2. Chemical cycles water, carbon, nitrogen 3. Human effects on cycles eutrophication, acid rain. Ecosystem = community plus abiotic factors - Conditions (temp, light) Resources (water, nutrients) - PowerPoint PPT PresentationTRANSCRIPT
Ecosystems
1. Energy Flow
2. Chemical cycleswater, carbon, nitrogen
3. Human effects on cycleseutrophication, acid rain
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Ecosystem = community plus abiotic factors
- Conditions (temp, light) Resources (water, nutrients)
• Energy flows from the sun, through plants, animals, and decomposers, and is lost as heat
• Chemicals are recycled between air, water, soil, and organisms
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
•A terrarium ecosystem / Biosphere II
Figure 36.8
Chemical cycling(C, N, etc.)
Lightenergy
Chemicalenergy
Heatenergy
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 36.10
Tertiaryandsecondaryconsumers
Secondaryandprimaryconsumers
Primaryconsumers
Producers
(Plants, algae,phytoplankton)
Detritivores
(Prokaryotes, fungi,certain animals)
Wastes anddead organisms
Food webs
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Chemicals are concentrated in food chains by biological magnification
Figure 38.3B
DDT in water0.000003 ppm
DDT inzooplankton0.04 ppm
DDT insmall fish0.5 ppm
DDT inlarge fish2 ppm
DDT infish-eating birds25 ppm
DDT concentration:increase of10 million times
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Food chains/webs reveal the flow of energy
• 170 billion tons of biomass per year
Figure 36.11
Tertiaryconsumers
Secondaryconsumers
Primaryconsumers
Producers
10 kcal
100 kcal
1,000kcal
10,000 kcal
1,000,000 kcal of sunlight
Energy supply limits the length of food chains
Avg. 10% conversion of biomassto next level
Endothermic animals convert only 2%
Plants convert 30-85%
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Consequences:
• Low density of large carnivores
• a field of corn can support more vegetarians than carnivores.
Figure 36.12
Secondaryconsumers
Primaryconsumers
Producers
Humanvegetarians
Corn
Humanmeat-eaters
Cattle
Corn
TROPHIC LEVEL
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
– Water cycle
- Carbon cycle
– Nitrogen cycle
Chemicals are recycled between organic matter and abiotic reservoirs
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 36.14
Solarheat
Precipitationover the sea(283)
Net movementof water vaporby wind (36)
Flow of waterfrom land to sea(36)
Water vaporover the sea
Oceans
Evaporationfrom the sea(319)
Evaporationandtranspiration(59)
Water vaporover the land
Precipitationover the land(95)
Surface waterand groundwater
oceans
salt water = 97.5%
freshwater = 2.5%
ice capsand
glaciers1.97%
ground-water0.5%
lakes,rivers,
and soil0.03%
atmosphere0.001%
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Carbon is taken from the atmosphere by photosynthesis
– used to make organic molecules
returned to the atmosphere by cellular respiration, decomposers
Carbon cycle
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 36.15
CO2 in atmosphere
Cellular respiration
Higher-levelconsumers
Primaryconsumers
Plants,algae,
cyanobacteria
Photosynthesis
Wood andfossil fuels
Detritivores(soil microbes
and others) Detritus
Decomposition
Burning
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Nitrogen is plentiful in the atmosphere as N2
– But plants and animals cannot use N2
• Some bacteria in soil and legume root nodules convert N2 to compounds that plants can use:
ammonium (NH4+) and nitrate (NO3
–)
The nitrogen cycle relies heavily on bacteria
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Nitrogen (N2) in atmosphere
Amino acidsand proteins in
plants and animalsAssimilationby plants
Denitrifyingbacteria
Nitrates(NO3
–)
Nitrifyingbacteria
Detritus
Detritivores
Decomposition
Ammonium (NH4+)
Nitrogenfixation
Nitrogen-fixingbacteria in soil
Nitrogen-fixingbacteria in root
nodules of legumes
Nitrogenfixation
76%naturallyoccurring
24%naturallyoccurring
24%human-caused
58%human-caused
46%available
54%used
AtmosphericCO2concentration
Terrestrialnitrogenfixation
Accessiblesurfacewater
Human impact on chemical cycles
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Environmental changes caused by humans can unbalance nutrient cycling over the long term– Example: acid rain
– Sulfur dioxide, nitrogen oxides create strong acids when dissolved in rain water.
– Low pH kills aquatic life, leaches nutrients from soil
– Calcium deficiency affects everything in food chain: plants, insects, birds. Weak egg shells.
eutrophication • Algal bloom can cause a lake to lose its species diversity
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
– Human-caused eutrophication wiped out fisheries in Lake Erie in the 1950s and 1960s
Figure 36.19B
– classic experiments on eutrophication led to the ban on phosphates in detergents
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
What are the limits to human alteration of chemical cycles and habitats?
• What should the limits be?
• How do we set priorities for what we value in the natural world?
Aesthetic, economic, conservation, humans