54 ecosystems
TRANSCRIPT
-
8/14/2019 54 Ecosystems
1/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
PowerPoint Lectures for Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Chapter 54
Ecosystems
-
8/14/2019 54 Ecosystems
2/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Overview: Ecosystems, Energy, and Matter
An ecosystem consists of all the organismsliving in a community
As well as all the abiotic factors with whichthey interact
-
8/14/2019 54 Ecosystems
3/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Ecosystems can range from a microcosm, such
as an aquarium To a large area such as a lake or forest
Figure 54.1
-
8/14/2019 54 Ecosystems
4/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Regardless of an ecosystems size
Its dynamics involve two main processes:energy flow and chemical cycling
Energy flows through ecosystems
While matter cycles within them
-
8/14/2019 54 Ecosystems
5/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 54.1: Ecosystem ecology emphasizes
energy flow and chemical cycling Ecosystem ecologists view ecosystems
As transformers of energy and processors of matter
-
8/14/2019 54 Ecosystems
6/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Ecosystems and Physical Laws
The laws of physics and chemistry apply to
ecosystems Particularly in regard to the flow of energy
Energy is conserved
But degraded to heat during ecosystemprocesses
-
8/14/2019 54 Ecosystems
7/83Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Trophic Relationships
Energy and nutrients pass from primary
producers (autotrophs) To primary consumers (herbivores) and then to
secondary consumers (carnivores)
-
8/14/2019 54 Ecosystems
8/83Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Energy flows through an ecosystem
Entering as light and exiting as heat
Figure 54.2
Microorganismsand other
detritivores
Detritus
Primary producers
Primary consumers
Secondaryconsumers
Tertiaryconsumers
Heat
Sun
Key
Chemical cycling
Energy flow
-
8/14/2019 54 Ecosystems
9/83Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Nutrients cycle within an ecosystem
-
8/14/2019 54 Ecosystems
10/83Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Decomposition
Decomposition
Connects all trophic levels
-
8/14/2019 54 Ecosystems
11/83Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Detritivores, mainly bacteria and fungi, recycleessential chemical elements
By decomposing organic material and returningelements to inorganic reservoirs
Figure 54.3
-
8/14/2019 54 Ecosystems
12/83Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 54.2: Physical and chemical factors
limit primary production in ecosystems Primary production in an ecosystem
Is the amount of light energy converted tochemical energy by autotrophs during a giventime period
-
8/14/2019 54 Ecosystems
13/83Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Ecosystem Energy Budgets
The extent of photosynthetic production
Sets the spending limit for the energy budgetof the entire ecosystem
-
8/14/2019 54 Ecosystems
14/83Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Global Energy Budget
The amount of solar radiation reaching the
surface of the Earth Limits the photosynthetic output of ecosystems
Only a small fraction of solar energy
Actually strikes photosynthetic organisms
-
8/14/2019 54 Ecosystems
15/83Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Gross and Net Primary Production
Total primary production in an ecosystem
Is known as that ecosystems gross primaryproduction (GPP)
Not all of this production
Is stored as organic material in the growingplants
-
8/14/2019 54 Ecosystems
16/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Net primary production (NPP)
Is equal to GPP minus the energy used by theprimary producers for respiration
Only NPP
Is available to consumers
-
8/14/2019 54 Ecosystems
17/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Different ecosystems vary considerably in their netprimary production
And in their contribution to the total NPP on Earth
Lake and stream
Open oceanContinental shelf
Estuary
Algal beds and reefsUpwelling zones
Extreme desert, rock, sand, ice
Desert and semidesert scrubTropical rain forest
SavannaCultivated land
Boreal forest (taiga)
Temperate grassland
Tundra
Tropical seasonal forest
Temperate deciduous forestTemperate evergreen forest
Swamp and marsh
Woodland and shrubland
0 10 20 30 40 50 60 0 500 1,000 1,500 2,000 2,500 0 5 10 15 20 25
Percentage of Earths netprimary production
Key
Marine
Freshwater (on continents)
Terrestrial
5.20.30.10.1
4.7
3.53.32.92.7
2.41.8
1.71.6
1.5
1.31.00.4
0.4
125360
1,500
2,500
5003.090
2,200
900600
800600
700
1401,600
1,2001,300
2,000250
5.61.2
0.90.1
0.040.9
22
7.99.1
9.6
5.4
3.50.6
7.1
4.93.8
2.30.3
65.0 24.4
Figure 54.4ac
Percentage of Earthssurface area
(a) Average net primaryproduction (g/m 2 /yr)
(b) (c)
-
8/14/2019 54 Ecosystems
18/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Overall, terrestrial ecosystems
Contribute about two-thirds of global NPP andmarine ecosystems about one-third
Figure 54.5
180 120 W 60 W 0 60 E 120 E 180
North Pole
60 N
30 N
Equator
30S
60 S
South Pole
-
8/14/2019 54 Ecosystems
19/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Primary Production in Marine and FreshwaterEcosystems
In marine and freshwater ecosystems Both light and nutrients are important in
controlling primary production
-
8/14/2019 54 Ecosystems
20/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Light Limitation
The depth of light penetration
Affects primary production throughout thephotic zone of an ocean or lake
-
8/14/2019 54 Ecosystems
21/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Nutrient Limitation
More than light, nutrients limit primary
production Both in different geographic regions of the
ocean and in lakes
-
8/14/2019 54 Ecosystems
22/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
A limiting nutrient is the element that must be
added In order for production to increase in a
particular area
Nitrogen and phosphorous
Are typically the nutrients that most often limitmarine production
-
8/14/2019 54 Ecosystems
23/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Nutrient enrichment experiments
Confirmed that nitrogen was limiting phytoplanktongrowth in an area of the ocean
EXPERIMENT Pollution from duck farms concentrated near Moriches Bay adds both nitrogen and phosphorus to the coastal water off Long Island. Researchers cultured the phytoplankton Nannochloris
atomus with water collected from several bays.
Figure 54.6
Coast of Long Island, New York. The numbers on the map indicatethe data collection stations.
L o n g I s
l a n d
G r e a t S o u
t h B a y
Shinnecock
BayMoriches Bay
Atlantic Ocean
30 21
19
151154
2
-
8/14/2019 54 Ecosystems
24/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.6
(a) Phytoplankton biomass and phosphorus concentration (b) Phytoplankton response to nutrient enrichment
GreatSouth Bay
MorichesBay
ShinnecockBay
Startingalgal
density
2 4 5 11 30 15 19 21
30
24
18
12
6
0
Unenriched control
Ammonium enrichedPhosphate enriched
Station number
P h y t o p
l a n
k t o n
( m i l l i o n s o f c e
l l s p e r m
L )
876543210
2 4 5 11 30 15 19 21
87
654
3210
I n o r g a n
i c p
h o s p
h o r u s
( g a
t o m s
/ L )
P h y t o p
l a n
k t o n
( m i l l i o n s o
f c e
l l s / m L )
Station number
CONCLUSION Since adding phosphorus, which was already in rich supply, had no effect onNannochloris growth, whereas adding nitrogen increased algal density dramatically, researchersconcluded that nitrogen was the nutrient limiting phytoplankton growth in this ecosystem.
Phytoplankton
Inorganicphosphorus
RESULTS Phytoplankton abundance parallels the abundance of phosphorus in the water (a). Nitrogen,however, is immediately taken up by algae, and no free nitrogen is measured in the coastal waters. Theaddition of ammonium (NH 4
+ ) caused heavy phytoplankton growth in bay water, but the addition of
phosphate (PO 43 +
) did not induce algal growth (b).
-
8/14/2019 54 Ecosystems
25/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Experiments in another ocean region
Showed that iron limited primary production
Table 54.1
-
8/14/2019 54 Ecosystems
26/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The addition of large amounts of nutrients tolakes
Has a wide range of ecological impacts
-
8/14/2019 54 Ecosystems
27/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
In some areas, sewage runoff
Has caused eutrophication of lakes, which canlead to the eventual loss of most fish species fromthe lakes
Figure 54.7
-
8/14/2019 54 Ecosystems
28/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Primary Production in Terrestrial and WetlandEcosystems
In terrestrial and wetland ecosystems climaticfactors
Such as temperature and moisture, affect
primary production on a large geographic scale
-
8/14/2019 54 Ecosystems
29/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The contrast between wet and dry climates
Can be represented by a measure calledactual evapotranspiration
-
8/14/2019 54 Ecosystems
30/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Actual evapotranspiration
Is the amount of water annually transpired by plantsand evaporated from a landscape
Is related to net primary production
Figure 54.8Actual evapotranspiration (mm H 2O/yr)
Tropical forest
Temperate forest
Mountain coniferous forest
Temperate grassland
Arctic tundra
Desertshrubland
N e
t p r i m a r y p r o
d u c t
i o n
( g / m 2 / y r )
1,000
2,000
3,000
0500 1,000 1,5000
-
8/14/2019 54 Ecosystems
31/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
On a more local scale
A soil nutrient is often the limiting factor in primaryproduction
Figure 54.9
EXPERIMENT Over the summer of 1980, researchers addedphosphorus to some experimental plots in the salt marsh, nitrogento other plots, and both phosphorus and nitrogen to others. Someplots were left unfertilized as controls.
RESULTS
Experimental plots receiving justphosphorus (P) do not outproducethe unfertilized control plots.
CONCLUSION
L i v e ,
a b o v e - g r o u n
d b i o m a s s
( g d r y w
t / m
2 )
Adding nitrogen (N)boosts net primaryproduction.
300
250
200
150
100
50
0June July August 1980
N + P
N only
Control
P only
These nutrient enrichment experimentsconfirmed that nitrogen was the nutrient limiting plant growth inthis salt marsh.
-
8/14/2019 54 Ecosystems
32/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 54.3: Energy transfer between trophiclevels is usually less than 20% efficient
The secondary production of an ecosystem
Is the amount of chemical energy inconsumers food that is converted to their ownnew biomass during a given period of time
d i ffi i
-
8/14/2019 54 Ecosystems
33/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Production Efficiency
When a caterpillar feeds on a plant leaf
Only about one-sixth of the energy in the leaf is used for secondary production
Figure 54.10
Plant materialeaten by caterpillar
Cellular respiration
Growth (new biomass)
Feces 100 J
33 J
200 J
67 J
-
8/14/2019 54 Ecosystems
34/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The production efficiency of an organism
Is the fraction of energy stored in food that isnot used for respiration
T hi Effi i d E l i l P id
-
8/14/2019 54 Ecosystems
35/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Trophic Efficiency and Ecological Pyramids
Trophic efficiency
Is the percentage of production transferredfrom one trophic level to the next
Usually ranges from 5% to 20%
P id f P d i
-
8/14/2019 54 Ecosystems
36/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Pyramids of Production
This loss of energy with each transfer in a food chain
Can be represented by a pyramid of net production
Figure 54.11
Tertiaryconsumers
Secondaryconsumers
Primaryconsumers
Primaryproducers
1,000,000 J of sunlight
10 J
100 J
1,000 J
10,000 J
P id f Bi
-
8/14/2019 54 Ecosystems
37/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Pyramids of Biomass
One important ecological consequence of lowtrophic efficiencies
Can be represented in a biomass pyramid
-
8/14/2019 54 Ecosystems
38/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Most biomass pyramids
Show a sharp decrease at successively higher trophic levels
Figure 54.12a
(a) Most biomass pyramids show a sharp decrease in biomass atsuccessively higher trophic levels, as illustrated by data froma bog at Silver Springs, Florida.
Trophic level Dry weight
(g/m2
)
Primary producers
Tertiary consumers
Secondary consumers
Primary consumers
1.5
11
37809
-
8/14/2019 54 Ecosystems
39/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Certain aquatic ecosystems
Have inverted biomass pyramids
Figire 54.12b
Trophic level
Primary producers (phytoplankton)
Primary consumers (zooplankton)
(b) In some aquatic ecosystems, such as the English Channel,a small standing crop of primary producers (phytoplankton)supports a larger standing crop of primary consumers (zooplankton).
Dry weight(g/m 2)
21
4
P id f N b
-
8/14/2019 54 Ecosystems
40/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Pyramids of Numbers
A pyramid of numbers
Represents the number of individualorganisms in each trophic level
Figure 54.13
Trophic level Number of individual organisms
Primary producers
Tertiary consumers
Secondary consumers
Primary consumers
3
354,904
708,624
5,842,424
-
8/14/2019 54 Ecosystems
41/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The dynamics of energy flow throughecosystems
Have important implications for the humanpopulation
Eating meat
Is a relatively inefficient way of tappingphotosynthetic production
-
8/14/2019 54 Ecosystems
42/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Worldwide agriculture could successfully feedmany more people
If humans all fed more efficiently, eating onlyplant material
Figure 54.14
Trophic level
Secondaryconsumers
Primaryconsumers
Primaryproducers
The Green World Hypothesis
-
8/14/2019 54 Ecosystems
43/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Green World Hypothesis
According to the green world hypothesis
Terrestrial herbivores consume relatively littleplant biomass because they are held in checkby a variety of factors
-
8/14/2019 54 Ecosystems
44/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Most terrestrial ecosystems
Have large standing crops despite the largenumbers of herbivores
Figure 54.15
-
8/14/2019 54 Ecosystems
45/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The green world hypothesis proposes severalfactors that keep herbivores in check
Plants have defenses against herbivores
Nutrients, not energy supply, usually limit
herbivores Abiotic factors limit herbivores
Intraspecific competition can limit herbivore
numbers Interspecific interactions check herbivore
densities
-
8/14/2019 54 Ecosystems
46/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 54.4: Biological and geochemicalprocesses move nutrients between organic andinorganic parts of the ecosystem
Life on Earth
Depends on the recycling of essential chemicalelements
Nutrient circuits that cycle matter through anecosystem
Involve both biotic and abiotic components andare often called biogeochemical cycles
A General Model of Chemical Cycling
-
8/14/2019 54 Ecosystems
47/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
A General Model of Chemical Cycling
Gaseous forms of carbon, oxygen, sulfur, andnitrogen
Occur in the atmosphere and cycle globally
Less mobile elements, including phosphorous,potassium, and calcium
Cycle on a more local level
-
8/14/2019 54 Ecosystems
48/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
A general model of nutrient cycling
Includes the main reservoirs of elements andthe processes that transfer elements betweenreservoirs
Figure 54.16
Organicmaterialsavailable
as nutrients
Livingorganisms,detritus
Organic
materialsunavailableas nutrients
Coal, oil,peat
Inorganicmaterialsavailable
as nutrients
Inorganicmaterials
unavailableas nutrients
Atmosphere,soil, water
Mineralsin rocksFormation of
sedimentary rock
Weathering,erosion
Respiration,decomposition,excretion
Burningof fossil fuels
Fossilization
Reservoir a Reservoir b
Reservoir c Reservoir d
Assimilation,photosynthesis
-
8/14/2019 54 Ecosystems
49/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
All elements
Cycle between organic and inorganicreservoirs
Biogeochemical Cycles
-
8/14/2019 54 Ecosystems
50/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Biogeochemical Cycles
The water cycle and the carbon cycle
Figure 54.17
Transportover land
Solar energy
Net movement of water vapor by wind
Precipitationover ocean
Evaporationfrom ocean
Evapotranspirationfrom land
Precipitationover land
Percolationthroughsoil
Runoff andgroundwater
CO 2 in atmosphere
Photosynthesis
Cellular respiration
Burning of fossil fuelsand wood Higher-level
consumersPrimaryconsumers
DetritusCarbon compoundsin water
Decomposition
THE WATER CYCLE THE CARBON CYCLE
-
8/14/2019 54 Ecosystems
51/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Water moves in a global cycle
Driven by solar energy
The carbon cycle
Reflects the reciprocal processes of photosynthesis and cellular respiration
-
8/14/2019 54 Ecosystems
52/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The nitrogen cycle and the phosphorous cycle
Figure 54.17
N2 in atmosphere
Denitrifyingbacteria
Nitrifyingbacteria
Nitrifyingbacteria
Nitrification
Nitrogen-fixingsoil bacteria
Nitrogen-fixingbacteria in rootnodules of legumes
Decomposers
Ammonification
Assimilation
NH3 NH4+
NO 3
NO 2
Rain
Plants
Consumption
Decomposition
Geologicuplift
Weatheringof rocks
Runoff
SedimentationPlant uptakeof PO 43
Soil
Leaching
THE NITROGEN CYCLE THE PHOSPHORUS CYCLE
-
8/14/2019 54 Ecosystems
53/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Most of the nitrogen cycling in naturalecosystems
Involves local cycles between organisms andsoil or water
The phosphorus cycle
Is relatively localized
Decomposition and Nutrient Cycling Rates
-
8/14/2019 54 Ecosystems
54/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Decomposition and Nutrient Cycling Rates
Decomposers (detritivores) play a key role
In the general pattern of chemical cycling
Figure 54.18
Consumers
Producers
Nutrientsavailable
to producers
Abioticreservoir
Geologicprocesses
Decomposers
-
8/14/2019 54 Ecosystems
55/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The rates at which nutrients cycle in differentecosystems
Are extremely variable, mostly as a result of differences in rates of decomposition
Vegetation and Nutrient Cycling: The Hubbard
-
8/14/2019 54 Ecosystems
56/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Vegetation and Nutrient Cycling: The HubbardBrook Experimental Forest
Nutrient cycling Is strongly regulated by vegetation
-
8/14/2019 54 Ecosystems
57/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Long-term ecological research projects
Monitor ecosystem dynamics over relativelylong periods of time
The Hubbard Brook Experimental Forest
Has been used to study nutrient cycling in aforest ecosystem since 1963
-
8/14/2019 54 Ecosystems
58/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The research team constructed a dam on thesite
To monitor water and mineral loss
Figure 54.19a
(a) Concrete dams and weirs built across streams atthe bottom of watersheds enabled researchers tomonitor the outflow of water and nutrients from theecosystem.
-
8/14/2019 54 Ecosystems
59/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
In one experiment, the trees in one valley werecut down
And the valley was sprayed with herbicides
Figure 54.19b(b) One watershed was clear cut to study the effects of the loss
of vegetation on drainage and nutrient cycling.
-
8/14/2019 54 Ecosystems
60/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Net losses of water and minerals were studied
And found to be greater than in an undisturbed area
These results showed how human activity
Can affect ecosystems
Figure 54.19c(c) The concentration of nitrate in runoff from the deforested watershed was 60 times
greater than in a control (unlogged) watershed.
N i t r a
t e
c o n c e n
t r a
t i o n
i n r u n o f f
( m g
/ L )
Deforested
Control
Completion of tree cutting
1965 1966 1967 1968
80.060.040.020.0
4.03.02.01.0
0
-
8/14/2019 54 Ecosystems
61/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 54.5: The human population isdisrupting chemical cycles throughout thebiosphere
As the human population has grown in size
Our activities have disrupted the trophicstructure, energy flow, and chemical cycling of ecosystems in most parts of the world
-
8/14/2019 54 Ecosystems
62/83
Agriculture and Nitrogen Cycling
-
8/14/2019 54 Ecosystems
63/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
g g y g
Agriculture constantly removes nutrients fromecosystems
That would ordinarily be cycled back into the soil
Figure 54.20
-
8/14/2019 54 Ecosystems
64/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Nitrogen is the main nutrient lost throughagriculture
Thus, agriculture has a great impact on thenitrogen cycle
Industrially produced fertilizer is typically usedto replace lost nitrogen
But the effects on an ecosystem can be
harmful
Contamination of Aquatic Ecosystems
-
8/14/2019 54 Ecosystems
65/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
q y
The critical load for a nutrient
Is the amount of that nutrient that can beabsorbed by plants in an ecosystem withoutdamaging it
-
8/14/2019 54 Ecosystems
66/83
-
8/14/2019 54 Ecosystems
67/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Sewage runoff contaminates freshwater ecosystems
Causing cultural eutrophication, excessivealgal growth, which can cause significant harmto these ecosystems
Acid Precipitation
-
8/14/2019 54 Ecosystems
68/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Combustion of fossil fuels
Is the main cause of acid precipitation
-
8/14/2019 54 Ecosystems
69/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
North American and European ecosystemsdownwind from industrial regions
Have been damaged by rain and snow containingnitric and sulfuric acid
Figure 54.21
4.6
4.64.3
4.14.3
4.6
4.64.3
Europe
North America
-
8/14/2019 54 Ecosystems
70/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
By the year 2000
The entire contiguous United States was affected byacid precipitation
Figure 54.22
Field pH 5.3
5.25.35.15.25.05.14.95.04.84.94.74.84.64.74.54.64.44.54.34.4< 4.3
-
8/14/2019 54 Ecosystems
71/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Environmental regulations and new industrialtechnologies
Have allowed many developed countries toreduce sulfur dioxide emissions in the past 30years
Toxins in the Environment
-
8/14/2019 54 Ecosystems
72/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Humans release an immense variety of toxicchemicals
Including thousands of synthetics previouslyunknown to nature
One of the reasons such toxins are so harmful Is that they become more concentrated in
successive trophic levels of a food web
-
8/14/2019 54 Ecosystems
73/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
In biological magnification
Toxins concentrate at higher trophic levelsbecause at these levels biomass tends to be lower
Figure 54.23
C o n c e n
t r a
t i o n o
f P C B s
Herringgull eggs124 ppm
Zooplankton0.123 ppm
Phytoplankton0.025 ppm
Lake trout4.83 ppm
Smelt1.04 ppm
-
8/14/2019 54 Ecosystems
74/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
In some cases, harmful substances
Persist for long periods of time in anecosystem and continue to cause harm
Atmospheric Carbon Dioxide
-
8/14/2019 54 Ecosystems
75/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
One pressing problem caused by humanactivities
Is the rising level of atmospheric carbondioxide
Rising Atmospheric CO 2
-
8/14/2019 54 Ecosystems
76/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Due to the increased burning of fossil fuels andother human activities
The concentration of atmospheric CO 2 has beensteadily increasing
Figure 54.24
C O
2 c o n c e n
t r a
t i o n
( p p m
)
390
380
370
360
350
340
330
320
310
3001960 1965 1970 1975 1980 1985 1990 1995 2000 2005
1.05
0.90
0.75
0.60
0.45
0.30
0.15
0
0.15
0.30
0.45
T e m p e r a
t u r e v a r i a
t i o n
( C )
Temperature
CO 2
Year
How Elevated CO 2 Affects Forest Ecology: The
-
8/14/2019 54 Ecosystems
77/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
FACTS-I Experiment
The FACTS-I experiment is testing how elevated CO 2
Influences tree growth, carbon concentration in soils,and other factors over a ten-year period
Figure 54.25
The Greenhouse Effect and Global Warming
-
8/14/2019 54 Ecosystems
78/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The greenhouse effect is caused byatmospheric CO 2
But is necessary to keep the surface of theEarth at a habitable temperature
-
8/14/2019 54 Ecosystems
79/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Increased levels of atmospheric CO 2 aremagnifying the greenhouse effect
Which could cause global warming andsignificant climatic change
Depletion of Atmospheric Ozone
-
8/14/2019 54 Ecosystems
80/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Life on Earth is protected from the damagingeffects of UV radiation
By a protective layer or ozone moleculespresent in the atmosphere
-
8/14/2019 54 Ecosystems
81/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Satellite studies of the atmosphere
Suggest that the ozone layer has been graduallythinning since 1975
Figure 54.26
O z o n e
l a y e r
t h i c k n e s s
( D o b s o n u n
i t s )
Year (Average for the month of October)
350
300
250
200
150
100
50
01955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
-
8/14/2019 54 Ecosystems
82/83
Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The destruction of atmospheric ozone
Probably results from chlorine-releasingpollutants produced by human activity
Figure 54.27
1
2
3
Chlorine from CFCs interacts with ozone (O 3),forming chlorine monoxide (ClO) andoxygen (O 2).
Two ClO moleculesreact, formingchlorine peroxide (Cl 2O 2).
Sunlight causesCl2O 2 to breakdown into O 2 and freechlorine atoms.The chlorineatoms can beginthe cycle again.
Sunlight
Chlorine O 3
O 2
ClO
ClO
Cl2O 2
O 2
Chlorine atoms
-
8/14/2019 54 Ecosystems
83/83
Scientists first described an ozone hole
Over Antarctica in 1985; it has increased insize as ozone depletion has increased
(a) October 1979 (b) October 2000