41
~?
ECOSYSTEMS
Bye-Bye, Blue Bayou
OVERVIEW OF BIOGEOCHEMICAL CYCLES
THE NATURE OF ECOSYSTEMS
Overview of the Participants
Structure of Ecosystems
GLOBAL CYCLING OF WATER
The Hydrologic Cycle
The Water Crisis
THE NATURE OF FOOD WEBS
CARBON CYCLE
DDT IN FOOD WEBS
GREENHOUSE GASES, GLOBAL WARMING
STUDYING ENERGY FLOW THROUGH
ECOSYSTEMS
What Is Primary Productivity?
Ecological Pyramids
NITROGEN CYCLE
The Cycling Process
Human Impact on the Nitrogen Cycle
PHOSPHORUS CYCLE
ENERGY FLOW THROUGH SILVER SPRINGS
Interactive Exercises
Bye-Bye, Blue Bayou
[pp~730-731]
41.1. THE NATURE OF ECOSYSTEMS [pp.732-733]
41.2. THE NATURE OF FOOD WEBS [pp.734-735]
41.3. DDT IN FOOD WEBS [p.736]
~0':')
For additional practice, use the interactive vocabulary exercises linked with your BiologyNow CD-ROM~
Selected Words: herbivores [p.732], carnivores [p.732], parasites [p~732], omnivores [p~732], scavenger [p~732],
energy inputs [p.733], nutrient inputs [p.733], energy outputs [p~733], nutrient outputs [p.733], detrital food
webs [p.735], Silent Spring [p~736]
Boldfaced-Terms
[p~732]
primary producers _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.732] consumers
[p.732] detritivores _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Ecosystems 463
[p.732] decomposers
[p.733] ecosystem _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.733] trophic levels _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.733] food chain _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.733] food webs _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.735] grazing food web
[p.735] detrital food web _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.736] biological magnification --'-_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Short Answer
1. Describe the ecological and economic disaster that may be unfolding for the state of Louisiana and
many other regions of the world. [pp.730-731]
Matching
Match each of the following terms with the correct description.
2. ___ consumers [p.732]
3. - - - herbivores [p.732]
4. ___ carnivores [p.732]
5. _ _ parasites [p.732]
6. _ _ decomposers [p.732]
7. _ _ detritivores [p.732]
8. _ _ omnivores [p.732]
9. _ _ scavengers [p.732]
464 Chapter Forty-One
a. A type of consumer that dines on animals, plants,
fungi, protistans, and even bacteria
b. Live in or on a host and feed on its tissues
c. An array of organisms and their physical
environment, interacting through a one-way flow
of energy and a cycling of raw materials
d. A type of consumer that eats flesh
e. Heterotrophs that feed on the tissues, products,
and remains of other organisms
f. Eat particles of decomposing organic matter; the
crab is an example
g. Loss of energy and nutrients in an ecosystem
10. _ _ ecosystem [p.733]
h. A type of consumer that eats plants
i. Animal consumers that ingest dead plants, animals,
or both all of the time or some of the time; vultures,
termites, and hyenas are examples
j. Bacteria, protests, and fungi that degrade the
wastes and remains of all organisms to inorganic
compounds
k. Incoming sunlight energy and a delivery of
minerals to an ecosystem (such as a creek
delivering dissolved minerals to a lake)
11. _ _ energy and nutrient inputs [p.733]
12. _ _ energy and nutrient outputs [p.733]
Fill in the Blanks
All the organisms of an (13)
[p.733] can be classified by their functional roles in a hierarchy
of feeding relationships called (14)
[p.733] levels. A (15) _ _ _ _ _ _ _ _ _ _ __
[p.733] is a straight-line sequence of steps by which energy stored in autotroph tissues enters higher trophic
levels. In reality, it is more accurate to think of food chains cross-connecting with one another, as a
(16)
[p.733]. In most cases, the (17)
initially captured passes through no more than (18)
[p.734] that producers
[p.734] or (19)
[p.734]
trophic levels. All of the heat losses from an ecosystem represent a one-way flow of (20) _ _ _ _ __
[p.734] out of the ecosystem. 'There are two categories of food webs. In a (21)
food web, energy flows mostly into herbivores, carnivores, and then (22)
[p.735]
[p.735]. In a
(23)
[p.735] food web, energy from producers flows mainiy into detritivores and
(24)
[p.735]. 'The amount of energy that moves through the two kinds of food webs differs
among (25)
[p.735], and it often varies with the seasons. In most cases, however, most of
the energy stored in producer tissues moves through (26)
[p.735] food webs.
Choice
Questions 27-32 refer to the theoretical food web diagram that follows, where numbers represent organisms.
Organisms 1, 2, and 3 are producers, and arrows show the direction of energy flow. [pp.734-735]
_ _ _ _ 27. Which organism(s) is(are) decomposers?
a. 11, 13
b. 4
c. 1
d. 3,4
_ _ _ _ 28. Which organisms represent only the first trophic level?
a.5,1,6,3
b. 1,2,3,4
c. 1,2,3
d. 11,12
Ecosystems 465
~~~_
29. Which organisms represent only the second trophic level?
a.
5,6,7, 8
c. 1,6,7,8
b. 9,10,11
d. 9,6,7,8
_ _ _ _ 30. Which organisms represent only the third trophic level?
a. 9,10
~~~_
b. 4,10,11
c. 10, 11
d. 9,11
31. Which orgarusm(s) represent(s) only the fourth trophic level?
a. 12, 13
b. none
c. 12
d. 13
_ _ _ _ 32. Which organism(s) represent more than one trophic level?
a. 9,10,11
b. 10,11
c. 10,12, 13
d. 3,7,10
Short Answer
33. Define the term biological magnific'!.tion, cite an example of it, and tell what person was important in
identifying the harmful effects on wildlife of pesticide use. [p.736]
0
41.4. STUDYING ENERGY FLOW THROUGH ECOSYSTEMS [p.737]
41.5. ENERGY FLOW THROUGH SILVER SPRINGS [p.738]
Selected Words: gross primary production [p.737], net primary production [p.737], trophic level [p.737]
Boldfaced Terms
[p.737] primary productivity _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.737] net ecosystem production _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.737] biomass pyramid _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _~
[p.737] energy pyramid _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
466 Chapter Forty-One
Matching
Match each of the following terms with the correct description.
1. _ _ primary productivity [p.737]
.
d t' [737]
2.
gross pnmary pro uc IOn p.
---
a. All energy initially trapped by producers
b. illustrates how the amount of usable energy
d'IffillliS
. . h es as It
..IS transf erred through an
3. ___ net primary production [p.737]
4. _ _ net ecosystem production [p.737]
5. _ _ ecological pyramid [p.737]
c.
6. _ _ energy pyramid [p.737]
7. _ _ amount of energy transferred from
one trophic level to the next [p.738]
d.
e.
f.
g.
ecosystem; sunlight energy is captured at theiJase,
or first trophic level, and declines through
successive levels to its tip (top carnivores)
The fraction of trapped energy that producers
funnel into growth and reproduction
6 to 16 percent
The gross primary production minus the energy
used by producers and by detritivores and
decomposers in soil
The rate at which producers capture and store
energy in their tissues during a given interval; how
much energy is stored depends on the number of
producers and on the balance between energy
trapped by photosynthesis and the energy used by
aerobic respiration
A method that ecologists use to represent trophic
structure; primary producers are the base
Identification
Answer the questions by identifying the various energy components illustrated in the diagram. [p.737]
c:
8. Which component(s) best represent(s) the
gross primary production in this diagram?
9. Which best represent(s) the net primary
productivity?
sunlight
j
0
a. producers
j
j
b. energy used
in respiration
c. tissues produced
following energy use
in respiration
Fill in the B lanlcs
The long-term study of an aquatic system at Silver Springs was of a (10)
Given the amount of energy lost in organic wastes, only (11)
[p.738] food web.
[p.738] to (12) _ _ _ _ __
[p.738] percent of the energy entering one trophic level becomes available to organisms at the next level. Most
of the primaty producers in this small spring are aquatic (13)
are insects and small (14)
The original energy source, (16)
(17)
[p.738]. Most of the carnivores
[p.738]. The top carnivores are larger (15)
[p.738].
[p.738], is available all year. The spring's
[p.738] and decomposers cycle organic compounds from the other tropic levels.
The producers trapped (18)
[p.738] percent of the incoming solar energy, and only a
little more than a third of that amount became fixed in new plant biomass. The producers used more than
(19)
[p.738] percent of the fixed energy for their own metabolism. About (20) _ _ _ _ __
Ecosystems
467
[p.738] percent of the fixed energy was transferred to the herbivores, and most of this was used for
metabolism or transferred to detritivores and decomposers.
Of the energy that was transferred to herbivores, only (21)
next trophic level (carnivores). About (22)
[p.738] percent reached the
[p.738] percent of the energy in lower-level
carnivores flowed to the top carnivores.
41.6. OVERVIEW OF BIOGEOCHEMICAL CYCLES [p.739]
41.7. GLOBAL CYCLING OF WATER [pp.740-741]
Selected Words: hydrologic cycle [p.739], atmospheric cycles [p.739], sedimentary cycles [p.739]
Boldfaced Terms
[p.739] biogeochemical cycle ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~_
[p.739] nutrients ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~_
[p.740] hydrologic cycle
[p.740] watershed ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[p.741] salinization ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~_
[p.741] gronndwater
[p.741] desalinization ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~_
Complete the Table
1. Complete the following table by summarizing the functions of the three types of biogeochemical cycles.
[p.739]
Biogeochem.ical Cycle
a. Hydrologic cycle
b. Atmospheric cycles
c. Sedimentary cycles
468 Chapter Forty-One
General Function(s)
Matching
Match each of the following terms with the correct description.
2. _ _ hydrologic cycle [p.740]
3. _ _ watershed [p.740]
4. _ _ effects of deforestation [p.740]
5. _ _ desalinization [p.741]
6. _ _ heavy irrigation [pp.740-741]
7. _ _ groundwater contamination [p.741]
8. _ _ water pollution [p.741]
9. _ _ water wars [p.741]
10. _ _ salinization [p.741]
a. Caused by evaporation in regions where soil
drains poorly; stunts crops and decreases yields
b. Alters the suitability of land for agriculture;
commonly has high concentrations of minetal salts
c. Upheavals over water rights; regional, national,
and global planning for the future is long overdue
d. Driven by continual inputs of solar energy, Earth's
waters slowly move on a vast scale, from the ocean
into the atmosphere, to land, and back to the
ocean-the main reservoir
e. Inputs of sewage, animal wastes, and many toxic
chemicals from power-generating plants and
factories make water unfit to drink
f. Any region where precipitation flows into a single
stream or river; can be small or vast
g. Sediments and pesticides run off from fields into
water, along with phosphates and other nutrients
that promote algal blooms; pollutants accumulate
in lakes, rivers, and bays before reaching the ocean;
many cities all over the world still dump untreated
sewage into coastal waters
h. Causes an imbalance in the nutrient inputs and
outputs of watersheds
i. Removal of salt from seawater; the processes
require fossil fuels
41.8. CARBON CYCLE [pp.742-743]
41.9. GREENHOUSE GASES, GLOBAL WARMING [pp.744-745]
Selected Words: carbon-oxygen cycle [p.742], ancient aquatic ecosystems [p.742], greenhouse gases [p.744]
Boldfaced Terms
[p.742] carbon cycle _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.744] greenhouse effect
[p.745] global warming _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Ecosystems
469
Choice
Choose from the following:
a. carbon cycle
b. global warming
1. ___ Atmospheric molecules of carbon dioxide, water, nitrous oxide, methane, and
chlorofluorocarbons are among the main players [p.744]
2. ___ When photosynthetic autotrophs fix carbon, they lock billions of metric tons of carbon atoms in
organic compounds each year [p.742]
3. _ _ Another name for the carbon-oxygen cycle [p.742]
4. ___ Gases impede the escape of longer, infrared wavelengths from Earth into space [p.744]
5. ___ Carbon reservoirs ----+ atmosphere and oceans ----+ through organisms ----+ carbon
reservoirs; global movement [p.742-743]
6. _ _ The "greenhouse gases" [p.744]
7. ___ In ancient aquatic ecosystems, carbon became incorporated into the shells and other hard body
parts of many marine species [p.742]
8. ___ Carbon dioxide gas, or CO2, is the most abundant form of carbon in the atmosphere [p.742]
9. ___ Carbon dioxide gas is released as cells engage in aerobic respiration, when fossil fuels or forests
burn, and when volcanoes erupt [p.742]
,
10. ___ The increase in greenhouse gases may be a factor in a long-term rise in temperature near
Earth's surface [p.745]
11. ___ At present, deforestation, the burning of wood and fossil fuels, and other human activities
release more carbon into the atmosphere than can be cycled back to ocean reservoirs by natural
processes [p.743]
12. ___ Atmospheric carbon dioxide may be at its highest level since 420,000 years ago, and possibly at
its highest level since 20 million years ago [pp.745-746]
41.10. NITROGEN CYCLE [pp.746-747]
Boldfaced Terms
[p.746] nitrogen cycle _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.746] nitrogen fixation _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.747] ammonliication _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.747] nitrification _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.747] denitrification
--.
470 Chapter Forty-One
Matching
Match each of the following tenus with the correct description.
1. _ _ nitrogen [p.746]
2. _ _ nitrogen fixation [p.746]
3. _ _ on the roots of peas or other
legumes [p.746]
4. _ _ ammonification [p.747]
5. _ _ nitrogen in plant tissues [p.747]
6. _ _ nitrification [p.747]
7. _ _ denitrification [p.747]
S. _ _ human impact on the nitrogen
cycle [p. 747]
9. _ _ nitrogen scarcity [p.747]
10. _ _ nitrogen-fixing bacteria [p.746]
a. Moves through trophic levels of ecosystems and ends
up in nitrogen-rich wastes and remains
b. Deforestation and grassland conversion for agriculture
c. By this metabolic process, certain bacteria in soil split
all three bonds in gaseous nitrogen and then use the
atoms to form ammonia (NH3 )
d. Live in the soil, in aquatic habitats, and as
photosynthetic mutnalists in lichens
e. Travels in the atmosphere as N2
f. Certain bacteria convert nitrate or nitrite to gaseous
nitrogen 01' nitrogen oxide (NO,)
g. Bacteria and fungi break down nitrogenous materials,
forming ammonium
h. Farmers rotate crops and increasingly use
nitrogen-rich chemical fertilizers; plant responses to
high nitrogen levels vary
i. Rhizobium fonus nodules containing nitrogen-fixing
bacteria
j. Bacteria produce nitrite as a product when they strip
electrons from ammonia
41.11. PHOSPHORUS CYCLE [pp.74S-749]
Boldfaced Terms
[p.748] phosphorus cycle
[p.749] eutrophication _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Fill in the B lanles
lil the (1)
[p.74S] cycle, this element passes quickly through food webs as it moves from
land to ocean sediments and then slowly back to land. Earth's crust is the largest (2)
for (1). In rock formations, phosphorus occurs mainly as phosphate (3)
[p.74S]
[p.74Sj. Weathering
and soil erosion convey these ions into streams and rivers, and from there they eventnally become part
of the (4)
[p.74S] sediments. They fonu insoluble deposits on submerged continental
(5)
[p.74S]. Millions of years go by. As movements of cnistal plates uplift part of the
(6)
[p.74S], phosphates become exposed on drained land surfaces. Over time, weathering
and erosion release phosphates from exposed rocks once again.
All organisms use (7)
[p.74S] to synthesize ATP, phospholipids, nucleic acids, and
other compounds. Plants take up dissolved phosphates from soil (S)
them by eating plants; carnivores get them by eating (9)
[p.74S]. Herbivores get
[p.74Sj. Animals lose phosphate in
Ecosystems 471
I·
:1
I
urine and feces. Bacterial and fungal (10) _ _ _ _ _ _ [p.748] release phosphate from organic wastes
and remains, and then plants take them up again.
The (11)
[p.748] cycle helps move phosphorus and other minerals through ecosystems.
Of all minerals, phosphorus is most often the (12)
Only newly weathered, young soils are (13)
[p.748] factor in natural ecosystems.
[p.748] in phosphorus, and in aquatic habitats
most phosphorus is tied up in (14) _ _ _ _ _ _ [p.748]. Only a negligible amount of phosphorus occurs
in (15) _ _ _ _ _ _ [p.748] form, so little is lost to the atmosphere.
Especially in tropical and subtropical parts of developing countries, phosphorus is being depleted from
natural ecosystems that often have (16)
[p.748] soils. When trees are
harvested or land is cleared for agriculture, phosphorus is (17)
[pp.748-749]. Crop yields
[p.749]. In developed countries, after years of
start out low and soon become (18) "
(19) _ _ _ _ _ _ [p.749] applications, many soils have phosphorus overloads. Dissolved phosphorus
that gets into streams, rivers, lakes, and estuaries can promote destructive (20)
blooms. In many freshwater (21)
[p.749]
[p.749], nitrogen-fixing bacteria keep the nitrogen levels
high, so phosphorus becomes the (22) _ _ _ _ _ _ [p.749] factor. As aerobic decomposers bre;k down
the remains of algae, the water becomes depleted of the (23) _ _ _ _ _ _ [p.749] that fishes and other
organisms require.
The term (24) _ _ _ _ _ _ [p.749] refers to the nutrient emichment of any ecosystem that is
otherwise low in (25)
[p.749]. Phosphorus inputs, as from agriculture, accelerate it.
Self-Quiz
Are you ready for the exam? Test yourself on key concepts by taking the additional tests linked with your
BiologyNow CD-ROM.
__ 1.
eat only dead or
decomposing particles of organic matter.
[p.732]
a. Herbivores
b. Parasites
c. Detritivores
d. Carnivores
e. Omnivores
__ 2. An array of organisms and their physical
environment, interacting through a oneway flow of energy and a cycling of raw
materials, is a(n)
. [p.733]
a. population
b. ecosystem
c. community
d. biosphere
e. food web
472 . Chapter Forty-One
__ 3. The members of feeding relationships are
structured in a hierarchy, the steps of
which are called
. [p.733]
a. organism levels
b. energy source levels
c. eating levels
d. trophic levels
e. energy transfers
__ 4. A straight-line sequence of steps by which
energy that was originally stored in
autotroph tissues moves to higher trophic
levels is a(n)
. [p.733]
a. trophic level
b. food chain
c. ecological pyramid
d. food web
e. biochemical cycle
__ 5. In a
food web, energy
flows mostly into herbivores, then into
carnivores, and then into decomposers.
[p.735]
a. primary
b. detrital food web
c. grazing food web
d. trophic
e. both b and c
__ 6.
is a process whereby a
substance that degrades slowly, or not at
all, becomes more concentrated in
consumer tissues as it moves through ever
higher trophic levels. [p.736]
a. Ecosystem modeling
b. Nutrient input
c. The biogeochemical cycle
d. Biological magnification
e. Gross primary production
__ 8. In the carbon cycle, carbon enters the
atmosphere through _ _ _ _ _ _.
[p.742]
a. carbon dioxide fixation
b. aerobic respiration, fossil fuel and forest
burning, and volcanic eruptions
c. oceans and accumulation of plan~.
biomass
d. release of greenhouse gases
e. carbon reservoirs
__ 9. Ecosystems lose nitrogen to the alr
naturally via the activities of
_ _ _,-----. [p.747]
a. ammonifying bacteria
b. denitrifying bacteria
c. nitrogen-fixing bacteria
d. ion exchange bacteria
e. nitrifying bacteria
_
__ 7. Of the 1,700,000 kilocalories of solar
energy that entered an aquatic ecosystem
in Silver Springs, Florida, researchers
determined that about _ _ _ _ __
percent of incoming solar energy was
trapped by producers. [p.738]
a.1
b.10
c. 25
d.74
e.5
10.
is the nutrient enrichment
of any ecosystem that is otherwise low in
nutrients, a natural successional process.
[p.749]
a. Nitrification
b. Ion exchange
c. Ammonification
d. Eutrophication
e. Carbon fixation
Chapter Objectives/Review Questions
1. List the major culprits responsible for the dire predictions made for the future of Louisiana and planet
Earth. [pp.730-731]
2. Name and define the principal participants of an ecosystem. [p.732]
3. A(n)
is an array of organisms and their physical environment, all interacting through a
flow of energy and a cycling of materials. [p.733]
4. Explain why nutrients can be completely recycled but energy cannot. [p.733]
5. Members of an ecosystem fit somewhere in a hierarchy of energy transfers (feeding relationships)
called
levels. [p.733]
6. ,Distinguish between food chains and food webs. [p.733]
7. In most cases, the
that producers initially capture passes through no more than four or
five trophic levels. [p.734]
8. Compare grazing food webs with detrital food webs. Give an example of each. [p.734]
9. Describe how DDT damages ecosystems; discuss biological magnification. [p.736]
10. Distinguish among primary productivity, gross primary productivity, net primary production, and net
ecosystem production. [p.737]
11. Ecologists often represent the trophic structure as an ecological
. [p.737]
Ecosystems 473
\
\
12.
13.
14.
15.
16.
17.
18.
19.
20.
Explain what studies at Silver Springs, Florida, watershed have taught us about energy flow. [p.738]
Briefly describe the hydrologic cycle, atmospheric cycles, and sedimentary cycles. [p.739]
Define the terms desalinization, salinization and groundwater. [p.741]
The carbon cycle traces carbon movement from reservoirs in the
and oceans, through
organisms, and then back to reservoirs. [pp.742-743]
Certain gases cause heat to build up in the lower atmosphere, a warming action known as the
_ _:---:-----,-effect. [p.744]
Describe the chemical events that occur during nitrogen fixation, ammonification, nitrification, and
denitrification. [pp.746-747]
Be able to discuss various aspects of the human impact on the nitrogen cycle. [p.747]
Be able to trace the major steps in the phosphorus cycle. [pp.748-749]
is the name for nutrient enrichment of an ecosystem that is naturally low in nutrients.
[p.748]
Media Menu Review Questions
Questions 1 and 2 are drawn from the following InfoTrac College Edition article: "Be Fruitfui, Multiply,
and Lose Nitrogen." Anonymous. Global Environmental Change Report, October 25, 2002.
1. The good news is that rising concentrations of atmospheric
will
encourage growth of many agricultural crops. The bad news is that enhanced crop productivity may
come at the expense of
value.
2. Scientists found that higher levels of
enhanced plant responses; that is,
an increase was found in the number of flowers produced, fruit quantity and weight, and number of
seeds. Along with that, lower concentrations of
were found in the seeds than in those
grown at current levels of atmospheric _ _ _ _ _ _ _ _ _ _ __
Questions 3 and 4 are drawn from the following InfoTrac College Edition article: "Spring Forward: Warmer
Climates Accelerate Life Cycles of Plants, Animals." Sid Perkins. Science News, March 8, 2003.
3. With each spring season, the cycle of life begins anew, but because of a recent trend in _ _ _ _ __
_ _ _ _ _ _ , the cycle is changing.
4. Phenologists, who study organisms' responses to seasonal and climatic changes, have noted that the
annual cycles for many creatures are beginning
, on average, as global temperatures
Questions 5 and 6 are drawn from the following InfoTrac College Edition article: "Anthropogenic
Disturbances of the Terrestrial Water Cycle." Charles J. Vorosmarty and Dork Sahagian. Bioscience,
September 2000.
5. The terrestrial
cycle plays a central role in the climate, ecology, and biogeochemistry of
the planet.
6. By some accounts, irretrievable losses of water total 60 to 70 percent of all water withdrawn for all
purposes, and
alone accounts for 85 to 90 percent of this consumption.
Questions 7 and 8 are based on the FAQ section found at water.usgs.gov
7.
is the process by which microbes (generally bacteria) or plants transform a hannful
water contaminant into a nonharrnful substance, much as we turn sugar into carbon dioxide and water.
8. The presence of the bacterium Escherichia coli in water is a strong indication of recent
or
animal
contamination. Public water supplies are usually disinfected with _ _ _ _ __
Question 9 is based on "Ecosystems," found at www.enviroliteracy.org
9. There is general agreement on the importance of protecting biological
, especially
because
depend on the "services" provided by living organisms and _ _ _ _ __
474 Chapter Forty-One
Question 10 is based on "Global Warming." John Weier. April 8, 2002. Found at earth observatory.nasa.gov
emissions, then low-lying nations could be awash
10. If we don't curb our
in seawater, rain and drought patterns across the world could change, hurricanes could become
more frequent, and El Nilio events could become more intense. On the other hand, there are those,
some of whom are
, who believe that global warming will result in little more than
_ _ _ _ _ _ winters and
plant growth.
Integrating and Applying Key Concepts
1. In 1971, Diet for a Small Planet was published. Frances Moore Lappe, the author, felt that people in the
United States of America wasted protein and ate too much meal. She said, "We have created a national
consumption pattern in which the majority, who can pay, overconsume the most inefficient livestock
products [cattle] well beyond their biological needs (even to the point of jeopardizing their health),
while the minority, who cannot pay, are inadequately fed, even to the point of malnutrition." Cases of
marasmus (a nutritional disease caused by prolonged lack of food calories) and kwashiorkor (caused by
severe, long-term protein deficiency) have been found in Nashville, Tennessee, and on an Indian
reservation in Arizona, respectively. Lappe's partial solution to the problem was to encourage people to
get as much of their protein as possible directly from plants and to supplement that with less meat
from the more efficient converters of grain to protein (chickens, turkeys, and hogs) and with seafood
and dairy products.
Most of us realize that feeding the hungry people of the world is not just a matter of distributing
the abundance that exists-political, economic, and cultural factors are also involved. Yet it is still
worthwhile to consider applying Lappe's idea to our everyday living. Devise two full days of
breakfasts, lunches, and dinners that would enable you to exploit the lowest acceptable trophic levels to
sustain yourself healthfully.
Ecosystems 475