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CHAPTER 7 ECOSYSTEMS AND NUTRIENT CYCLING
ENGINEERING
EARTH
A desert experiment gone awry
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ENGINEERING EARTH
A desert experiment gone awry
At the end of this
chapter you will know:
Learning
Outcomes
• Environmental factors
that affect the makeup
and distribution of
biomes
• Tolerance limits and
organization structure in
ecosystems
• Nutrient cycling and the
organisms responsible
for these functions
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ENGINEERING EARTH
A desert experiment gone awry
Case study: Eight scientists
spent two years in an artificial
environment known as
Biosphere 2.
Main
Concept
In addition to wanting to prove that survival in
an artificial, self-sustaining habitat was possible,
the purpose of this study was to gain a better
understanding of the complex interactions on
Earth, so we can make better decisions.
Ecosystems are complex
assemblages of living and
non-living components.
Many of the roles played
by the living organisms in
a system are irreplaceable.
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ENGINEERING EARTH
A desert experiment gone awry
We learn from
mistakes.
More than onethird of the flora
and fauna became
extinct.
Morning glory
vines took over
agriculture.
Cockroaches and crazy ants were thriving.
Trees failed to develop stress wood since
there was no wind.
A heavy diet of sweet potatoes left the
scientists orange.
Oxygen supplies became dangerously low.
TERMS TO KNOW:
Sustainable
Economics
Ecosystem services
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Organisms and their habitats form complex systems
TERMS TO KNOW:
Biospheres
Ecosystem
Habitat
Species
Niche
The scale of interactions
between organisms aids
human classification of
natural systems.
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Organisms and their habitats form complex systems
TERMS TO KNOW:
Biospheres
Ecosystem
Habitat
Species
Niche
The scale of interactions
between organisms aids
human classification of
natural systems.
7
Organisms and their habitats form complex systems
TERMS TO KNOW:
Biospheres
Ecosystem
Habitat
Species
Niche
The scale of interactions
between organisms aids
human classification of
natural systems.
7
Organisms and their habitats form complex systems
TERMS TO KNOW:
Biospheres
Ecosystem
Habitat
Species
Niche
The scale of interactions
between organisms aids
human classification of
natural systems.
7
Organisms and their habitats form complex systems
TERMS TO KNOW:
Biospheres
Ecosystem
Habitat
Species
Niche
The scale of interactions
All ecosystems are based
between organisms aids
on nutrient cycling and
human classification of
energysystems.
flow
natural
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Organisms and their habitats form complex systems
Biosphere 1 (The Earth) is materially closed but
energetically open. This means that energy
enters and leaves the system but biomass—the
plants and animals—do not.
Biomes fall into three broad categories based on
climate and determined by predominant plants.
Marine, freshwater, and terrestrial biomes are
further distinguished as ecosystems based on
interactions between specific biotic and abiotic
components.
TERMS TO KNOW:
Energy flow
Nutrient cycles
Biomass
Biome
To conduct field research in biological systems is
difficult due to our lack of control over the
interactions. In the Biosphere 2, scientists were
able to control and measure environmental
variables like oxygen and CO2 balances
periodically throughout their stay.
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Organisms and their habitats form complex systems
Biosphere 1 (The Earth) is materially closed but
energetically open. This means that energy
enters and leaves the system but biomass—the
plants and animals—do not.
Biomes fall into three broad categories based on
climate and determined by predominant plants.
Marine, freshwater, and terrestrial biomes are
further distinguished as ecosystems based on
interactions between specific biotic and abiotic
components.
TERMS TO KNOW:
Energy flow
Nutrient cycles
Biomass
Biome
To conduct field research in biological systems is
difficult due to our lack of control over the
interactions. In Biosphere 2, scientists were
able to manipulate and measure environmental
variables like oxygen and CO2 balances
periodically throughout their stay.
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Organisms and their habitats form complex systems
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Organisms and their habitats form complex systems
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Organisms and their habitats form complex systems
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Organisms and their habitats form complex systems
Biomes are specific types
of terrestrial ecosystems
with characteristic
temperature and
precipitation conditions.
Temperature decreases
when moving away from
the equator and with
increased elevation.
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Organisms and their habitats form complex systems
Mediterranean
scrub
Desert
Savanna
Tundra
Tropical
rainforest
Boreal
forest
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Organisms and their habitats form complex systems
Biosphere technology was developed
in the 1960s and 1970s as
preparation for space exploration.
Biosphere 2 remains the largest
enclosed ecosystem ever created.
Biosphere 2 houses several
biomes under one roof, each
contributing to overall
function.
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Organisms and their habitats form complex systems
Each biome required consideration
of the interactions between plant
and animal species as well as
careful assessment of nutrient
requirements for each organism.
Biosphere 2 houses several
biomes under one roof, each
contributing to overall
function.
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TERMS TO KNOW:
• Limiting factor
• Range of
tolerance
Living things survive within a specific range of
environmental conditions
Each biome required consideration of the interactions
between plant and animal species as well as careful
assessment of nutrient requirements.
Most desert biomes fluctuate from extreme cold at
night to high temperatures during the day. By
comparison, rainforests need consistently warm
temperatures.
Each organism must maintain homeostasis within a
narrow range. In Biosphere 2, tolerances needed to be
maintained within a closed system.
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Living things survive within a specific range of
environmental conditions
Populations have a range of
tolerance for each environmental
factor—light, water, salinity,
nitrogen.
Each species has an upper and
lower limit of tolerances beyond
which the organism cannot survive.
On the lower end of the spectrum
is the absolute minimum for
survival of a factor. This is where
limiting factors determine survival.
The optimal level is somewhere in
the middle and will vary somewhat
among individuals within a
population.
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Living things survive within a specific range of
environmental conditions
Populations have a range of
tolerance for each environmental
factor—light, water, salinity,
nitrogen.
Each species has an upper and
lower limit of tolerances beyond
which the organism cannot survive.
On the lower end of the spectrum
is the absolute minimum for
survival of a factor. This is where
limiting factors determine survival.
The optimal level is somewhere in
the middle and will vary somewhat
among individuals within a
population.
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Living things survive within a specific range of
environmental conditions
Populations have a range of
tolerance for each environmental
factor—light, water, salinity,
nitrogen.
Each species has an upper and
lower limit of tolerances beyond
which the organism cannot survive.
On the lower end of the spectrum
is the absolute minimum for
survival of a factor. This is where
limiting factors determine survival.
The optimal level is somewhere in
the middle and will vary somewhat
among individuals within a
population.
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Living things survive within a specific range of
environmental conditions
TERMS TO KNOW:
Limiting factor
Range of tolerance
In the beginning, things went
smoothly—carrots, broccoli,
spinach, kale, and other
vegetables had been planted
next to the human habitat,
and a few domestic animals
provided milk and meat. The
scientist got healthier at first.
Less light than anticipated led
to lower productivity than
needed.
Pests and disease began to cut
production, too.
The Biosphere ocean is still used for marine research.
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Nutrients such as carbon cycle through ecosystems
Nutrients cycle through and are stored in both biotic
(living) and abiotic (non-living) components of a system.
Reservoirs for CO2 include plants, oceans, and soil.
The producers use the stored CO2 from the atmosphere
to produce sugar while releasing oxygen.
TERMS TO KNOW:
Biotic
Abiotic
Reservoirs (or sinks)
Producer
Consumer
Cellular respiration
The sugar molecule represents
stored chemical energy that the
producer can use.
The consumer eats the plant and,
in so doing, releases the energy
from the sugar molecules
through cellular respiration.
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Nutrients such as carbon cycle through ecosystems
Carbon cycles in and out
of living things during
photosynthesis and
cellular respiration.
Carbon is transferred as
consumers and
decomposers eat other
organisms.
Some carbon is stored in
the bodies of organisms
and in oceans, soil, and
the atmosphere.
Overall, the carbon cycle
is balanced between
respiration and
photosynthesis.
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Nutrients such as carbon cycle through ecosystems
Carbon cycles in and out
of living things during
photosynthesis and
cellular respiration.
Carbon is transferred as
consumers and
decomposers eat other
organisms.
Some carbon is stored in
the bodies of organisms
and in oceans, soil, and
the atmosphere.
Overall, the carbon cycle
is balanced between
respiration and
photosynthesis.
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Nutrients such as carbon cycle through ecosystems
Carbon cycles in and out
of living things during
photosynthesis and
cellular respiration.
Carbon is transferred as
consumers and
decomposers eat other
organisms.
Some carbon is stored in
the bodies of organisms
and in oceans, soil, and
the atmosphere.
Overall, the carbon cycle
is balanced between
respiration and
photosynthesis.
7
Nutrients such as carbon cycle through ecosystems
Carbon cycles in and out
of living things during
photosynthesis and
cellular respiration.
Carbon is transferred as
consumers and
decomposers eat other
organisms.
Some carbon is stored in
the bodies of organisms
and in oceans, soil, and
the atmosphere.
Overall, the carbon cycle
is balanced between
respiration and
photosynthesis.
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Nutrients such as carbon cycle through ecosystems
In Biosphere 2,
oxygen and carbon
were off by such a
great amount that
the scientists found
themselves
constantly
exhausted.
The plants in Biosphere 2 were producing oxygen, but the excessive growth
of soil microbes used oxygen faster than the plants could replace it.
The reason was that
oxygen levels had
fallen to dangerously
low levels—levels
too low to extract
energy from the
food they were
eating.
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Nutrients such as carbon cycle through ecosystems
Nitrogen and phosphorus are two additional chemicals
that are essential for life.
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TERMS TO KNOW:
Nitrogen fixation
Phosphorus cycle
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Nutrients such as carbon cycle through ecosystems
Nitrogen is the most
abundant element in the
Earth’s atmosphere and is
needed to make proteins
and nucleic acids.
Plants cannot use nitrogen
directly from the
atmosphere but, rather,
must convert it into usable
forms through the nitrogen
cycle.
Nitrogen is needed by all living things to make
biological molecules like protein and DNA. It is
continuously moved in and out of organisms and the
atmosphere in a cycle dependent on soil bacteria.
During nitrogen fixation,
one form of nitrogen is
converted by bacteria to
another form that can be
taken up by the roots of
plants.
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Nutrients such as carbon cycle through ecosystems
Nitrogen is the most
abundant element in the
Earth’s atmosphere and is
needed to make proteins
and nucleic acids.
Plants cannot use nitrogen
directly from the
atmosphere but rather,
must convert it into usable
forms through the nitrogen
cycle.
Nitrogen is needed by all living things to make
biological molecules like protein and DNA. It is
continuously moved in and out of organisms and the
atmosphere in a cycle dependent on soil bacteria.
During nitrogen fixation,
one form of nitrogen is
converted by bacteria to
another form that can be
taken up by the roots of
plants.
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Nutrients such as carbon cycle through ecosystems
Nitrogen and phosphorus are two additional chemicals
that are essential for life.
TERMS TO KNOW:
Nitrogen fixation
Phosphorus cycle
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Nutrients such as carbon cycle through ecosystems
Phosphorus is needed by all organisms to make DNA. This is
a very slow cycle. There is no atmospheric component—it is
dependent only on the weathering of rock to release new
supplies into the water and soil. Once dissolved in water, the
phosphorus can be taken up by organisms.
Phosphorus passes
from inorganic to
organic form through
interaction with water
and organisms.
In Biosphere 2, the
phosphorus became
trapped in water
systems and polluted
aquatic habitats. Algal
mats absorbed much of
the excess phosphorus.
Once dried, the
minerals could be
reclaimed from the
algae.
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Nutrients such as carbon cycle through ecosystems
Another Biosphere 2 project
is experimentation to predict
the effects of climate shifts
on trees.
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Ecosystems are complicated, but learning how they
function will help us restore degraded ones
Lessons from Biosphere 2
The Earth is far more complicated than we imagined or could plan for.
A small change can set off a sequence of events that can degrade a system’s
capacity to support life.
Negative results can be just as informative as positive results.
We gained a greater understanding of carbon cycling.
Biosphere 2 is still used by scientists from around the world to study the effects of
an atmosphere loaded with CO2.
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PERSONAL CHOICES THAT HELP
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UNDERSTANDING THE ISSUE
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UNDERSTANDING THE ISSUE
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ANALYZING THE SCIENCE
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EVALUATING NEW INFORMATION
The Smithsonian: http://nationalzoo.si.edu/SCBI/MigratoryBirds/Coffee/default.cfm
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MAKING CONNECTIONS