ecosystem ecology. ecosystem: the organisms in a particular area and the physical environment with...
TRANSCRIPT
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ECOSYSTEM ECOLOGY
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Ecosystem:
• The organisms in a particular area and the physical environment with which they interact.
(Abiotic factors: energy, water, carbon, nitrogen, phosphorous)
• All the biotic and abiotic factors in a community.
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Fig. 55-4
Microorganismsand other
detritivores
Tertiary consumers
Secondaryconsumers
Primary consumers
Primary producers
Detritus
Heat
SunChemical cycling
Key
Energy flow
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Energy Flow through Ecosystems
• Energy flows through ecosystems as organisms capture and store energy, then transfer it to organisms that eat them.
• These organisms are grouped into trophic levels...
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Trophic Levels:
Route of energy flow
- food chain
- food web
- pyramid of numbers
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Pyramid of Numbers
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Question:
“Why are big fierce animals rare?”
Charles Elton, 1927
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Answer:
Because of the way energy flowsthrough communities...
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Ecosystem Energy Budgets:
Primary Productivity (PP)
Secondary Productivity (SP1, SP2…)
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• Photosynthesis powers primary productivity.
Primary Productivity (PP)
• The annual productivity of an area is determined primarily by sunlight, temperature, and moisture.
• Rate at which energy or biomass is produced per unit area by plants (primary producers)
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Which of these ecosystems accounts for the largest amount of Earth’s primary productivity?
A) Tundra
B) Savannah
C) Salt marsh
D) Open ocean
E) Tropical rainforest
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Figure 56.5
Figure 56.5
Distribution of Primary Terrestrial Production Worldwide
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Positive Correlation Between Productivity and Sunlight
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Positive Correlation Between Productivity and...
Precipitation Temperature
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Net
pri
mar
y p
rodu
ctio
n (g
/m2 ·
yr)
Fig. 55-8
Tropical forest
Actual evapotranspiration (mm H2O/yr)
Temperate forest
Mountain coniferous forest
Temperate grassland
Arctic tundra
Desertshrubland
1,5001,00050000
1,000
2,000
3,000·
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Secondary Productivity (SP1, SP2…)
• rate of production of new biomass from PP by heterotrophic organisms (primary and secondary consumers)
• positively correlated with rainfall...
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Fig. 55-10
Primaryproducers
100 J
1,000,000 J of sunlight
10 J
1,000 J
10,000 J
Primaryconsumers
Secondaryconsumers
Tertiaryconsumers
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Where does all the energy go???
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Fig. 55-9
Cellularrespiration100 J
Growth (new biomass)
Feces
200 J
33 J
67 J
Plant materialeaten by caterpillar
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Ecological Efficiency:
Percent of energy transferred from one trophic level to the next.
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Three categories of transfer efficiency are required to predict energy flow from PP toSP1 to SP2...
1) consumption efficiency
2) assimilation efficiency
3) production efficiency
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1) consumption efficiency (CE)
% of total productivity at one trophic levelthat is consumed by the next highest level
(remainder not eaten)
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Green World Hypothesis
• Plants have many defenses against herbivores
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2) assimilation efficiency (AE)
% of ingested food energy that is assimilated(i.e. digested), and thus potentially availablefor growth, reproduction
(remainder lost as feces)
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AE is higher in carnivores (~80%) than in herbivores (20-50%). WHY?
A) Carnivores chew their food more.B) Herbivores chew their food more.C) Plant tissues are not as easy to digest
as meat.D) Meat is not as easy to digest as plant
tissues.
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Elephant dung
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3) production efficiency (PE)
% of assimilated energy that is incorporated into new biomass (growth, reproduction)
(remainder lost as respiratory heat)
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PE of endotherms (<10%) is lower than PE of ectotherms (30-40%). WHY?
A) Because endotherms have feathers and fur.
B) Because endotherms move more quickly than ectotherms.
C) Because ectotherms move more quickly than endotherms.
D) Because ectotherms get energy from the sun.
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• SP1 is the % of PP that is incorporated at the next highest trophic level…
• SP2 is the % of SP1 that is incorporated at thenext highest trophic level…
This is NEVER 100%.
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And that is why big fierceanimals are rare!
• Energy loss at each trophic level limits thelength of a food chain...
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Atmosphere
Lithosphere Hydrosphere
Living Organisms
+Detritus
Biogeochemical Cycles
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• In studying cycling of water, carbon, nitrogen, and other chemicals, ecologists focus on four factors:
– Biological importance of each chemical– Major reservoirs for each chemical– Forms in which each chemical is available or used
by organisms– Key processes driving movement of each chemical
through its cycle
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• Water is essential to all organisms
• 97% in the oceans
• 2% in glaciers and polar ice caps
• 1% in lakes, rivers, and groundwater
The Water Cycle
• Evaporation, transpiration, condensation, precipitation, and movement through surface and groundwater
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• Carbon-based organic molecules are essential to all organisms
• Carbon reservoirs include fossil fuels, soils, solutes in oceans, plant and animal biomass, and the atmosphere
The Carbon Cycle
• CO2 taken up via photosynthesis and released via respiration
• Volcanoes and burning of fossil fuels contribute CO2 to atmosphere (2.9 B metric tons/yr)
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CO2
CO
2 con
cen
trat
ion
(p
pm
)
Temperature
1960300
Ave
rage
glo
bal
tem
per
atu
re (
ºC)
1965 1970 1975 1980Year
1985 1990 1995 2000 200513.6
13.7
13.8
13.9
14.0
14.1
14.2
14.3
14.4
14.5
14.6
14.7
14.8
14.9
310
320
330
340
350
360
370
380
390 Greenhouse Gases and Global Warming
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Global Temperature Changes
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• Nitrogen is a component of amino acids, proteins, and nucleic acids
• Main reservoir of nitrogen is in atmosphere (N2)
• N2 converted to NH3 via nitrogen-fixing bacteria
The Nitrogen Cycle
• NH3 decomposed to NH4+, which can be decomposed to NO3
– by nitrifying bacteria; both assimilated by plants
• Denitrifying bacteria convert NO3– back to N2
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How Bears Feed Salmon to the Forest
• The run of salmon leads to a major flow of nutrients into estuaries and coastal watersheds
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• Bears catch salmon in river and consume them in forest; on average, half the carcass is not eaten.
• Bears’ fat tissue is virtually nitrogen-free, so most of nitrogen in salmon protein is excreted as urine and feces.
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• Measurements of nitrogen isotope ratios in tree rings shows that nitrogen from salmon is incorporated into trees and enhances their growth
• Nitrogen 14 from atmosphere• Nitrogen 15 from salmon