Some of the chemical building blocks of life called macronutrients are required by organisms in large quantities Water Carbon Hydrogen Oxygen Nitrogen Phosphorous ID: 730363
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CYCLESofLIFESlide2
28.3 How Do Nutrients Cycle Within and Among Ecosystems?
Some of the chemical building blocks of life, called
macronutrients
, are required by organisms in large quantities
Water
–
Carbon
Hydrogen
–
Oxygen
Nitrogen
–
Phosphorous
Sulfur
–
CalciumSlide3
28.3 How Do Nutrients Cycle Within and Among Ecosystems?
Macronutrients
are required only in trace quantities
Zinc
–
Molybdenum
Iron
–
Selenium
Iodine
Nutrient cycles
, also called
biogeochemical cycles
, describe the pathways that macronutrients and micronutrients follow as they move from their major sources in the abiotic parts of ecosystems, called
reservoirs
, through living communities and back againSlide4
28.3 How Do Nutrients Cycle Within and Among Ecosystems?
The hydrologic cycle has its major reservoir in the oceans
The water cycle, or
hydrologic cycle
, is the pathway that water takes as it travels from its major reservoir—the oceans—through the atmosphere, to reservoirs in freshwater lakes, rivers, and groundwater, and then back again to the oceans Slide5
28.3 How Do Nutrients Cycle Within and Among Ecosystems?
The hydrologic cycle has its major reservoir in the oceans
(continued)
The hydrologic cycle would continue even if life on Earth disappeared because the biotic portion of ecosystems plays a small role in the hydrologic cycle
The oceans cover 70% of the Earth’s surface and contain more than 97% of Earth’s water
Solar energy evaporates water, and it comes back to Earth as precipitation Slide6
28.3 How Do Nutrients Cycle Within and Among Ecosystems?
The hydrologic cycle has its major reservoir in the oceans
(continued)
Of the water that falls on land
Some is absorbed by the roots of plants
Most evaporates from the soil, lakes, and streams
A portion runs back to the oceans
An extremely miniscule fraction is stored in the bodies of living organisms
Some enters natural underground reservoirs called
aquifersSlide7
28.3 How Do Nutrients Cycle Within and Among Ecosystems?
The hydrologic cycle has its major reservoir in the oceans
(continued)
The hydrologic cycle is crucial for terrestrial communities because it continually restores the fresh water needed for land-based life
Plant leaves can only take up carbon dioxide gas after it has dissolved in a thin layer of water coating the cells inside the leaf
The hydrologic cycle does not depend on terrestrial organisms, but they would disappear without itSlide8
reservoirs
Figure 28-6
The hydrologic cycle
reservoirs
processes
processes
precipitation
over land
water vapor in
the atmosphere
evaporation
from the land
and from the
leaves of plants
lakes and rivers
evaporation from
lakes and rivers
runoff
from rivers
and land
evaporation
from the
ocean
water in
the ocean
precipitation
over the ocean
extraction for
agriculture
groundwater,
includingaquifers
seepage through soil
into groundwaterSlide9
Animation: The Hydrologic CycleSlide10
28.3 How Do Nutrients Cycle Within and Among Ecosystems?
The carbon cycle has major reservoirs in the atmosphere and oceans
Carbon atoms form the framework of all organic molecules
The
carbon cycle
is the pathway that carbon takes from its major short-term reservoirs in the atmosphere and oceans, through producers and into the bodies of consumers, detritivores, and decomposers, and then back again to its reservoirsSlide11
28.3 How Do Nutrients Cycle Within and Among Ecosystems?
The carbon cycle has major reservoirs in the atmosphere and oceans
(continued)
Carbon enters communities through capture of carbon dioxide (CO
2
) during photosynthesis
Producers on land get CO
2
from the atmosphere
Aquatic producers get CO
2
dissolved in the water Slide12
28.3 How Do Nutrients Cycle Within and Among Ecosystems?
The carbon cycle has major reservoirs in the atmosphere and oceans
(continued)
Primary consumers eat producers and acquire carbon stored in their tissues
These herbivores release some of the carbon through respiration as CO
2
, excrete carbon compounds in their feces, and store the rest in their bodies, which may be consumed by higher trophic levels Slide13
28.3 How Do Nutrients Cycle Within and Among Ecosystems?
The carbon cycle has major reservoirs in the atmosphere and oceans
(continued)
All living things eventually die, and their bodies are broken down by detritivores and decomposers, whose cellular respiration returns CO
2
to the atmosphere and oceans
The complementary processes of uptake by photosynthesis and release by cellular respiration continually recycle carbon from the abiotic to the biotic portions of an ecosystem and back againSlide14
28.3 How Do Nutrients Cycle Within and Among Ecosystems?
The carbon cycle has major reservoirs in the atmosphere and oceans
(continued)
Much of Earth’s carbon is bound up in limestone rock, formed from calcium carbonate (CaCO
3
) deposited on the ocean floor in the shells of prehistoric phytoplankton
Fossil fuels
, which include coal, oil, and natural gas, are additional long-term reservoirs for carbonSlide15
28.3 How Do Nutrients Cycle Within and Among Ecosystems?
The carbon cycle has major reservoirs in the atmosphere and oceans
(continued)
These substances were produced from the remains of prehistoric organisms buried deep underground and subjected to high temperature and pressure
In addition to carbon, the energy of prehistoric sunlight is trapped in these deposits
When human beings burn fossil fuels to tap this stored energy, CO
2
is released into the atmosphere, with potentially serious consequencesSlide16
Animation: The Carbon CycleSlide17
Figure 28-7
The carbon cycle
reservoirs
processes
trophic levels
CO
2
dissolved
in the ocean
CO
2
in the
atmosphere
burning
fossil fuels
respiration
fire
consumers
producers
photosynthesis
fossil fuels
(coal, oil, natural gas)
detritivores
and decomposers
decompositionSlide18
28.3 How Do Nutrients Cycle Within and Among Ecosystems?
The nitrogen cycle has its major reservoir in the atmosphere
Nitrogen is a crucial component of proteins, many vitamins, nucleotides (such as ATP), and nucleic acids (such as DNA)
The
nitrogen cycle
is the pathway taken by nitrogen from its primary reservoir—nitrogen gas (N
2
) in the atmosphere—to much smaller reservoirs of ammonia and nitrate in soil and water, through producers, consumers, detritivores and decomposers, and back to its reservoirsSlide19
28.3 How Do Nutrients Cycle Within and Among Ecosystems?
The nitrogen cycle has its major reservoir in the atmosphere
(continued)
While nitrogen gas (N
2
) makes up 78% of the atmosphere, this form of nitrogen cannot be utilized by plants
Plants utilize nitrate (NO
3
) or ammonia (NH
3
) as their nitrogen source Slide20
28.3 How Do Nutrients Cycle Within and Among Ecosystems?
The nitrogen cycle has its major reservoir in the atmosphere
(continued)
N
2
is converted to ammonia by specific bacteria during a process called
nitrogen fixation
Some of these bacteria live in water and soil and convert the ammonia into nitrate that plants can directly use
Others live in symbiotic associations with plants called
legumes
, which include alfalfa, soybeans, clover, and peas Slide21
28.3 How Do Nutrients Cycle Within and Among Ecosystems?
The nitrogen cycle has its major reservoir in the atmosphere
(continued)
Some nitrogen is released in wastes and dead bodies
Decomposer bacteria convert this back to nitrate and ammonia in the soil or water, which is then available to plants
Denitrifying bacteria
break down nitrate, releasing N
2
back to the atmosphere Slide22
28.3 How Do Nutrients Cycle Within and Among Ecosystems?
The nitrogen cycle has its major reservoir in the atmosphere
(continued)
People significantly manipulate the nitrogen cycle, both deliberately and unintentionally
About 150 million tons of nitrogen-based fertilizer are applied to farms each year
The heat produced by burning fossil fuels combines atmospheric N
2
and O
2
, generating nitrogen oxides that form nitrates
Human activities now dominate the nitrogen cycle Slide23
Animation: The Nitrogen CycleSlide24
Figure 28-8
The nitrogen cycle
reservoirs
processes
trophic levels
burning
fossil fuels
N
2
in the
atmosphere
lightning
application of
manufactured fertilizer
producers
consumers
decomposition
ammonia and
nitrates in water
denitrifying
bacteria
detritivores
and decomposers
uptake by
producers
ammonia
and nitrates
in soil
nitrogen-fixing
bacteria in soil
and legume rootsSlide25
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Ancient peoples, with small populations and limited technology, had relatively little impact on nutrient cycles
As the human population grew and technology increased, people began to act more independently of natural ecosystem processes
The Industrial Revolution resulted in a tremendous increase in our reliance on energy stored in fossil fuels for heat, light, transportation, industry, and agricultureSlide26
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Fertilizer use on commercial farms grew exponentially
Human use of fossil fuels and chemical fertilizers has significantly disrupted the global nutrient cycles of nitrogen, phosphorus, sulfur, and carbonSlide27
Figure 28-10
An algal bloom in the Gulf of MexicoSlide28
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Overloading the nitrogen and phosphorus cycles damages aquatic ecosystems
Fertilizers are applied to farm fields to help satisfy the agricultural demands of a growing human population
Water dissolves and carries away some of the phosphate and nitrogen-based fertilizer
As water drains into lakes, rivers, and ultimately the oceans, these fertilizers can disrupt the delicate balance of food webs by overstimulating the growth of phytoplankton Slide29
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Overloading the nitrogen and phosphorus cycles damages aquatic ecosystems
(continued)
The phytoplankton die, and their bodies sink into deeper water and provide food for decomposer bacteria
The decomposers use up most of the available oxygen, and other aquatic organisms, such as invertebrates and fish, die, creating “dead zones” in many waters Slide30
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Overloading the sulfur and nitrogen cycles causes acid deposition
Burning of sulfur-containing fossil fuels, primarily coal, accounts for about 75% of all sulfur dioxide emissions worldwide
These two substances combine with atmospheric water and form nitric and sulfuric acids
Days later and often hundreds of miles from the source, these acids fall to Earth in rain or snow Slide31
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Overloading the sulfur and nitrogen cycles causes acid deposition
(continued)
This “acid rain”—more accurately called
acid deposition
—was first recognized in New Hampshire, where a sample of rain collected in 1963 had a pH of 3.7, about the same as that of orange juice
Acid deposition damages forests, can render lakes lifeless, and even eats away at buildings and statuesSlide32
Figure 28-11
Acid deposition is corrosiveSlide33
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Overloading the sulfur and nitrogen cycles causes acid deposition
(continued)
Many lakes and ponds in the Adirondack Mountains are too acidic to support fish
Acid rain also increases the extent to which organisms are exposed to toxic metals, such as aluminum, mercury, lead, and cadmium, which are far more soluble in acidified water Slide34
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Overloading the sulfur and nitrogen cycles causes acid deposition
(continued)
Acid conditions dissolve aluminum out of the soil into soil water and lakes, where it inhibits plant growth and kills fish
Calcium and magnesium, which are essential nutrients for all plants, are leached out of the soil by acid precipitationSlide35
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Overloading the sulfur and nitrogen cycles causes acid deposition
(continued)
Plants in acidified soil become weak and more vulnerable to infection and damage by insects
The decline has been shown to be caused by acid conditions, coupled with drought, insect attack, and climate change
About half of the red spruce and one-third of the sugar maples in the Green Mountains of Vermont have been killedSlide36
Figure 28-12
Acid deposition can destroy forestsSlide37
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Overloading the sulfur and nitrogen cycles causes acid deposition
(continued)
Since 1990, government regulations have resulted in substantial reductions in emissions of both sulfur dioxide and nitrogen oxides from U.S. power plants
Sulfur dioxide emissions are down about 40% and nitrogen oxide levels have been reduced by more than 50%
Air quality has improved, and rain has become less acidicSlide38
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Overloading the sulfur and nitrogen cycles causes acid deposition
(continued)
Damaged ecosystems recover slowly
Adirondack lakes are gradually becoming less acidic
If acid deposition is completely eliminated, eventually the lakes will return to their normal pH
Most aquatic life should then recover in 3 to 10 years, depending on the species
Forests will take much longer to recoverSlide39
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Interfering with the carbon cycle is warming Earth’s climate
Some of the energy from sunlight is reflected back into space by the atmosphere, and by Earth’s surface, especially by areas covered with snow or ice
Most sunlight strikes relatively dark areas of the surface and is converted into heat that is radiated into the atmosphere
Water vapor, CO
2
, and several
greenhouse gases
trap some of the heat in the atmosphereSlide40
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Interfering with the carbon cycle is warming Earth’s climate
(continued)
This is a natural process called the
greenhouse effect
, which keeps our atmosphere relatively warm and allows life on Earth as we know it
For Earth’s temperature to remain constant, the total amount of energy entering and leaving Earth’s atmosphere must be equalSlide41
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Interfering with the carbon cycle is warming Earth’s climate
(continued)
If atmospheric concentrations of greenhouse gases increase, more heat is retained than is radiated into space, causing Earth to warm
Greenhouse gases are increasing because people burn fossil fuels, releasing CO
2
Other important greenhouse gases include methane (CH
4
), released by agricultural activities and burning fossil fuelsSlide42
Figure 28-13
The greenhouse effect
volcanoes
forest
fires
power plants
and factories
homes and other
buildings
agricultural
activities
Heat is
radiated back into
the atmosphere
Some atmospheric heat is
retained by greenhouse gases
Most heat is radiated
into space
Sunlight energy
enters the atmosphere
Some energy
is reflected back
into space
Most sunlight strikes
Earth’s surface and is
converted into heat
vehicle
emissions
SunSlide43
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Burning fossil fuels is causing climate change
Since the mid-1800s, human societies have increasingly relied on energy from fossil fuels
As we burn fossil fuel in our power plants, factories, and cars, we harvest the energy of ancient sunlight and release CO
2
into the atmosphere
Burning fossil fuels accounts for about 80% to 85% of the CO
2
human activities release into the atmosphere annuallySlide44
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Burning fossil fuels is causing climate change
(continued)
A second source of added atmospheric CO
2
is
deforestation
, which destroys tens of millions of forested acres annually and accounts for 15% of CO
2
emissions
Deforestation occurs principally in the tropics as rain forests are cut and burned
Collectively, human activities release about 35 to 40 billion tons of CO
2
into the atmosphere annuallySlide45
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Burning fossil fuels is causing climate change
(continued)
Since 1850, atmospheric CO
2
has increased by 40%
This increase is from 280 ppm to 392 ppm, with a current annual increase of 2 ppm
A larger and growing body of evidence indicates that human release of carbon dioxide and other greenhouse gases has amplified the natural greenhouse effect, thereby altering the global climateSlide46
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Burning fossil fuels is causing climate change
(continued)
Surface temperature data, recorded from thousands of weather stations around the world and from satellites that measure temperatures over oceans, show that Earth has warmed by about 1
F (0.6
C) since 1970
The overall impact of increased greenhouse gases is now usually called
climate change
, which includes both global warming and many other effects on our climate and Earth’s ecosystemsSlide47
Figure 28-14
Global temperature increases parallel atmospheric CO
2
increases
390
380
370
360
350
340
330
320
310
CO
2
(ppm)
300
1960
1970
1980
1990
2000
2010
year
Atmospheric CO
2
Global surface temperature
1960
1970
1980
1990
2000
2010
year
58.1
57.9
57.7
57.6
14.2
14.3
14.4
14.5
14.1
14.0
13.9
13.8
57.4
57.2
57.0
56.8
global average temperature
F
CSlide48
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Burning fossil fuels is causing climate change
(continued)
Spring snow in the Northern Hemisphere is declining
Glaciers are retreating worldwide
The World Glacier Monitoring Service reports that about 90% of the world’s mountain glaciers are shrinking, and that this trend seems to be accelerating
Glacier National Park, Montana, now has only 25 glaciers remainingSlide49
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Burning fossil fuels is causing climate change
(continued)
Climate scientists predict that the warming atmosphere will cause more severe storms, including stronger hurricanes
Greater amounts of rain or snow will fall in single storms
More frequent and more prolonged droughts will occur
Increased CO
2
makes the oceans more acidicSlide50
Figure 28-15
Glaciers are melting
Muir Glacier, 1941
Muir Glacier, 2004Slide51
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Continued climate change will disrupt ecosystems and endanger many species
Predictions of continued climate change are based on sophisticated computer models developed and run independently by climate scientists around the world
As models improve, they match past climate with ever-greater accuracy, providing increasing confidence in their predictions for the futureSlide52
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Continued climate change will disrupt ecosystems and endanger many species
(continued)
The models provide evidence that natural causes cannot account for the recent warming
The models match the data only when human carbon emissions are included in the calculations
The Intergovernmental Panel on Climate Change (IPCC) predicted that even under the best-case scenario, the average global temperature will rise by at least 3.2
F (1.8
C) by the year 2100Slide53
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Continued climate change will disrupt ecosystems and endanger many species
(continued)
The IPCC’s high-level emissions scenario projects an increase of 7.2
F (4.0
C)
Thousands of species will change their ranges, moving away from the equator toward the poles or higher up mountainsides
Some plants and animals will find it easier to move than othersSlide54
Figure 28-16
Projected range of temperature increases
7.2
4.0
3.0
5.4
3.6
2.0
1.0
1.8
F
C
0.0
0.0
projected global temperature increase
2000
2020
2040
2060
2080
2100
yearSlide55
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Continued climate change will disrupt ecosystems and endanger many species
(continued)
It is highly unlikely that entire communities of organisms can just pack and move, intact
Some species will have nowhere to go
For example, the loss of summer sea ice is bad news for polar bears and other marine mammals that rely on ice floes as nurseries for their youngSlide56
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Continued climate change will disrupt ecosystems and endanger many species
(continued)
Some of the movement of species may have direct impact on human health
Many diseases, especially those carried by mosquitoes and ticks, are currently restricted to tropical or subtropical parts of the planet
These disease vectors will probably spread poleward as a result of warming temperatures, bringing their diseases, such as malariaSlide57
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Continued climate change will disrupt ecosystems and endanger many species
(continued)
Some of the movement of species may have direct impact on human health
(continued)
It may become so hot and dry in parts of the tropics that mosquitoes and some other insects may have shortened life spans, thus reducing vector-borne diseases in these regionsSlide58
28.4 What Happens When Humans Disrupt Nutrient Cycles?
Continued climate change will disrupt ecosystems and endanger many species
(continued)
Although computer models can predict temperature changes, no one can confidently predict the resulting overall effects on human health