Chapter 48 Ecosystem Cloze Notes
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Overview: Ecosystems, Energy, and Matter
An __________________________ consists of all the organisms living in a community as well as all the abiotic
factors with which they interact
_________________________________ can range from a microcosm (a little world), such as an aquarium to a large
area such as a lake or forest
Regardless of an ecosystem’s size --its dynamics involve two main processes: __________________________ and
_______________________
Energy enters most ecosystems in the form of _____________________________.
It is converted to chemical energy by _____________________, passed to ______________________ in the organic
compounds of food and dissipated as heat
Energy flows through ecosystems while ______________________ cycles within them
Concept 54.1: Ecosystem ecology emphasizes energy flow and chemical cycling
Ecosystem ecologists view ecosystems as transformers of ______________________ and processors of
___________________
We can follow the transformation of energy by grouping the species in a community into _________________levels
of feeding relationships
Ecosystem and Physical Laws
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The laws of __________________ and_________________________ apply to ecosystems particularly in regard to
the flow of energy
The law of conservation of energy
Plants and other photosynthetic organisms convert solar energy to _________________, but the total amount of
____________________ does not change
The total amount of energy stored in organic molecules plus the amounts reflected and dissipated as heat must
equal the total solar energy intercepted by the plant
Second law of thermodynamics
Trophic Levles
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Trophic relationships determine the routes of _________________________ and chemical cycling in ecosystems.
Autotrophs, the _____________________________________ of the ecosystem, ultimately support all other
organisms.
Most autotrophs are photosynthetic _______________________________ that use light energy to synthesize sugars
and other organic compounds.
_____________________________________ are the primary producers in deep-sea hydrothermal vents.
____________________________ are at trophic levels above the primary producers and depend on their
photosynthetic output.
Herbivores that eat primary producers are called __________________________________
Carnivores that eat herbivores are called _____________________________________
Carnivores that eat secondary producers are called _________________________________
Another important group of heterotrophs is the __________________________, or __________________________
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They get energy from ______________________________, nonliving organic material such as the remains of dead
organisms, feces, fallen leaves, and wood.
Detritivores play an important role in ___________________________________.
__________________________ through an ecosystem entering as light and exiting as heat
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_________________________________________ within an ecosystem
Decomposition connects trophic levels
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The organisms that feed as __________________________________ form a major link between the primary
producers and the consumers in an ecosystem.
An ecosystem’s main decomposers are _______________________________________________.
_________________________________, mainly bacteria and fungi, recycle essential chemical elements
By decomposing organic material and returning elements to ________________________________
Concept 54.2: _________________________and _______________________factors limit primary production in
ecosystems
________________________________ in an ecosystem is the amount of light energy converted to chemical energy
by autotrophs during a given time period
An ecosystem’s energy budget depends on ___________________________________
Ecosystem Energy Budget
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The extent of _________________________________ sets the spending limit for the energy budget of the entire
ecosystem
The Global Energy Budget
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The amount of ___________________________ reaching the surface of the Earth limits the photosynthetic output
of ecosystems
Only a small fraction of solar energy actually strikes ________________________________________
Gross and Net Primary Production
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____________________________ in an ecosystem is known as that ecosystem’s gross primary production (GPP)
This is the amount of light energy that is converted into ___________________________ per unit time
Plants use some these molecules as fuel in their own _____________________________
Not all of this production is stored as organic material in the __________________________________
__________________________ (NPP) is equal to GPP minus the energy used by the primary producers for
respiration
Only NPP is available to _____________________________
Different ecosystems vary considerably in their __________________________________ and in their contribution
to the total NPP on Earth
Overall, __________________________________ contribute about ___________________ of global NPP and
______________________ecosystems about _______________________
Satellite images now
provide a means of
studying global
patterns of primary
production
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Primary Production in Marine and Freshwater
 _______________________________ are important in controlling primary production
Light Limitation
 The depth of ___________________________________ affects primary production throughout the photic zone of
an ocean or lake
Nutrient Limitation
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More than light, ________________________ limit primary production both in different geographic regions of the
ocean and in lakes
A __________________________ is the element that must be added
In order for production to increase in a particular area --_____________________________________ are typically
the nutrients that most often limit marine production
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___________________________________________ experiments confirmed that nitrogen was limiting
phytoplankton growth in an area of the ocean
Experiments in another ocean region showed that________________________ limited primary production
The addition of large amounts of nutrients to lakes has a wide range of _______________________________
In some areas, sewage runoff has caused ____________________________ (increase chemical nutrient added to an
ecosystem) of lakes, which can lead to the eventual loss of most fish species from the lakes
Algae
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Primary Production in Terrestrial and Wetland Ecosystem
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In terrestrial and wetland ecosystems climatic factors such as _________________________________, affect
primary production on a large geographic scale
The contrast between wet and dry climates can be represented by a measure called actual
_______________________________- which is the actually amount of water annually transpired by plants and
evaporated from a landscape.
Actual evapotranspiration increases with precipitation and with the amount of
________________________available to drive evaporation and transpiration
Actual evapotranspiration
Is the amount of ________________________________________by plants and evaporated from a landscape is
related to net primary production
On a more local scale
A ________________________________________ is often the limiting factor in primary production
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Concept 54.3: Energy transfer between trophic levels is usually less than ________________ efficient
The secondary production of an ecosystem is the amount of ____________________ in consumers’ food that is
converted to their own new _______________________ during a given period of time
Production Efficiency
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When a caterpillar feeds on a plant leaf only about one-sixth of the ____________________________in the leaf is
used for secondary production
The production efficiency of an organism is the fraction of ___________________________ in food that is not used
for respiration
Trophic Efficiency and Ecological Pyramids
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Trophic efficiency is the percentage of production _____________________ from one trophic level to the next
Usually ranges from _______________________________
In other words, 80-95% of the energy available at one trophic level is _____________________ transferred to the
next level
This loss is multiplied over the length of a _________________________.
Meaning only _______________________ of energy is transferred from one trophic level to the next – This is known
as the _____________________________
Pyramid Production
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This loss of _______________________with each transfer in a food chain can be represented by a pyramid of net
production
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Pyramids of Biomass
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One important ecological consequence of low trophic efficiencies can be represented in a
______________________
Most ______________________ narrow sharply from primary producers to top-level carnivores because energy
transfers are so inefficient.
Most biomass pyramids show a sharp _____________________________ at successively higher trophic levels
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Certain aquatic ecosystems have___________________________ biomass pyramids
This is because the producers
–phytoplankton – grow,
reproduce, and are
consumed by zooplankton so
rapidly that they never
develop a large standing crop
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Pyramids of Numbers
 A ______________________________________ represents the number of individual organisms in each trophic level
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The dynamics of _____________________ through ecosystems have important implications for the human
population
Eating meat is a relatively inefficient way of tapping _________________________________
Worldwide agriculture could feed many more people if humans all fed as ___________________________, eating
only plant material.
____________________________________________ could successfully feed many more people if humans all fed
more efficiently, eating only plant material
Green World Hypothesis
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According to the green world hypothesis: Terrestrial ____________________________ consume relatively little
plant biomass because they are held in check by a variety of factors
 Most terrestrial ecosystems have ______________________________________ despite the large numbers of
herbivores
 The green world hypothesis proposes several factors that keep herbivores in check
 __________________have defenses against herbivores
 ___________________, not energy supply, usually limit herbivores
 ________________________ limit herbivores
 _________________________ can limit herbivore numbers
 _________________________________ check herbivore densities
 Concept 54.4: Biological and geochemical processes move nutrients between _________________________ of the
ecosystem
 Life on Earth depends on the _______________________________of essential chemical elements
 Nutrient circuits that cycle matter through an ecosystem involve both biotic and abiotic components and are often
called ____________________________________
General Model of Chemical Cycling
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Gaseous forms of _____________________________________ occur in the atmosphere and cycle globally
Less mobile elements, including _____________________________________________ -- cycle on a more local level
A general model of nutrient cycling: Includes the main reservoirs of elements and the processes that transfer
elements between reservoirs (is defined by two characteristics: Whether it contains
_________________________________ and whether or not the materials are __________________ for use by
organisms )
 All elements cycle between _____________________________________________
Biogeochemical Cycle
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The water cycle and the carbon cycle
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Water moves in a global cycle driven by _______________________
The carbon cycle reflects the reciprocal processes of ______________________________________________
The nitrogen cycle and the phosphorous cycle
Nitrogen Cycle
Carbon Cycle
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Most of the nitrogen cycling in natural ecosystems involves local cycles between
______________________________
 The phosphorus cycle is relatively localized (does not go into the atmosphere (____________________________))
Decomposition and Nutrient Cycling Rates
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____________________________(_________________________) play a key role in the general pattern of
chemical cycling
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The rates at which ________________________________ in different ecosystems are extremely variable, mostly as
a result of differences in rates of __________________________
Decomposition takes an average of four to six years in the__________________________ forest, while in a
______________________________________ most organism material decomposes in a few months to a few years.
Nutrient cycling is strongly regulated by __________________________
Long-term ecological research projects
Monitor ecosystem dynamics over relatively long periods of time
The Hubbard Brook Experimental Forest has been used to study nutrient cycling in a forest ecosystem since 1963
The research team constructed a damn a deciduous forest with several valleys, drained by a small creek that is a
tributary of Hubbard Brook to monitor water and mineral loss
In one experiment, the trees in one valley were cut down and the valley was sprayed with herbicides
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Net losses of water and minerals were studied and found to be greater than in an undisturbed area
These results showed how __________________________________ can affect ecosystems
Concept 54.5: The human population is disrupting chemical cycles throughout the biosphere
As the human population has grown in size --our activities have disrupted the _____________________,
_____________________________, and __________________________ of ecosystems in most parts of the world
Nutrient Enrichment
 In addition to transporting nutrients from one location to another humans have added entirely new materials, some
of them __________________________, to ecosystems
Agriculture and Nitrogen Cycling
 Agriculture constantly removes _______________________ from ecosystems that would ordinarily be cycled back
into the_________________
 _________________________ is the main nutrient lost through agriculture thus, agriculture has a great impact on
the nitrogen cycle
 Industrially produced fertilizer is typically used to replace lost_____________________ but the effects on an
ecosystem can be harmful
Contamination to the aquatic ecosystem
 The _____________________________ for a nutrient is the amount of that nutrient that can be absorbed by plants
in an ecosystem without damaging it
 When excess nutrients are added to an ecosystem, the critical load is exceeded and the remaining nutrients can
contaminate groundwater and _______________________________________________________ ecosystems
 ________________________ contaminates freshwater ecosystems causing cultural eutrophication, excessive algal
growth, which can cause significant harm to these ecosystems, which leads to a _________________________
Acid Precipitation
 Combustion of __________________________ is the main cause of acid precipitation
 This lowers the __________________________________ and affects the soil chemistry of terrestrial ecosystems
 __________________________________ are leached from the soil with the decrease of pH.
 North American and European ecosystems downwind from _________________ have been damaged by rain and
snow containing __________________________________
With record
storms
occasionally
dropping rain as
acidic as pH 3.0
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By the year 2000 the entire contiguous United States was affected by ___________________________________
_____________________________________ and new industrial technologies have allowed many developed
countries to reduce sulfur dioxide emissions in the past 30 years
Toxins in the Environment
 Humans release an immense variety of ______________________ including thousands of synthetics previously
unknown 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 called _____________________________________
 Example: This is what caused the _____________________________ to be place on the Endanger Species List
 In biological magnification toxins concentrate at higher trophic levels because at these
levels_____________________tends to be lower
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In some cases, harmful substances persist for long periods of time in an ecosystem and continue to cause harm
Many toxins cannot be degraded by _______________________ and persist in the environment for years and
decades
 Example: _____________________________ (Shenandoah River)
Atomspheric Carbon Dioxide
 One pressing problem caused by human activities is the rising level of atmospheric _________________________
 Due to the increased burning of _____________________________ and other ____________________________
the concentration of atmospheric CO2 has been steadily increasing
 The FACTS-I experiment is testing how elevated CO2
 Influences tree growth, carbon concentration in soils, and other factors over a ten-year period
Greenhouse Effect and Global Warming
 The greenhouse effect is caused by atmospheric ______________
 CO2 causes the Earth retain some of the ____________________that would ordinarily escape the atmosphere but is
necessary to keep the surface of the Earth at a ________________________________
 Increased levels of atmospheric ________________ are magnifying the greenhouse effect which could cause
______________________________________ and significant _____________________________
Depletion of the Ozone Layer
 Life on Earth is protected from the damaging effects of ____________________ by a protective layer or ozone
molecules present in the atmosphere
 Satellite studies of the atmosphere suggest that the _________________________ has been gradually thinning since
1975
 The destruction of atmospheric ozone probably results from ________________________________ produced by
human activity
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Scientists first described an “___________________________” over Antarctica in 1985; it has increased in size as
ozone depletion has increased