Consider this segment of a food web: snails and grasshoppers eat paper plants; spiders eat grasshoppers; shrews eat snails and spiders; owls eat shrews. The shrew occupies in the trophic level of |
secondary and tertiary consumers |
Detritus |
dead animal, rotting log |
Primary producer |
living maple leaves |
Primary consumer/decomposer |
fungus, maggots, cricket |
Secondary consumer |
millipede, earthworm |
Both secondary and tertiary consumer |
robin, alligator lizard |
Carnivores are |
secondary consumers |
Approximately____% of the energy at one trophic level is passed on to the next trophic level |
5-10 |
Why is a diagram of energy flow from trophic level to trophic level shaped like a pyramid? |
most energy at each level is lost, leaving little for the next |
What provides your body with energy? |
fats |
Plants use___as a source of energy |
light |
What element is found in all organic compounds? |
carbon |
Plants obtain carbon from |
carbon dioxide |
What name is given to organisms that convert the carbon in organic compounds into carbon in carbon dioxide? |
decomposers |
Where do plants get the energy to make organic molecules? |
light |
What is not an organic molecule? |
minerals |
Where do plants get the carbon they use to make organic molecules? |
carbon dioxide |
Nitrifying bacteria convert___to____ |
ammonium….nitrites |
_____removes nitrogen from the atmosphere |
nitrogen fixation |
Assimilation is the |
uptake of nutrients into an organism |
Nitrogen fixation is the conversion |
of nitrogen to a form that plants can use |
Nitrification is the conversion |
of organic nitrogen-containing compounds to nitrites and nitrates |
Denitrifying bacteria convert____to____ |
nitrates…nitrogen gas |
What is an example of a nitrate |
NO3- |
What is an example of a nitrite |
NO2- |
In a biogeochemical cycle, a chemical element spends time in different places called |
reservoirs |
As a chemical element moves through a biogeochemcial cycle, it moves between "bio" and "geo". The "bio" in biogeochemical refers to biotic reservoirs, or |
living organisms |
The "geo" in biogeochemical refers to |
earth-specifically to the abiotic reservoirs where a chemical element can be found |
In the terrestrial carbon cycle, the abiotic reservoir from which living organisms directly obtain their carbon is |
the atmosphere |
Carbon moves from an abiotic reservoir to living organisms during the process of |
photosynthesis |
Carbon moves from living organisms to an abiotic reservoir during the process of |
cellular respiration |
Biogeochemical cycles are crucial to ecosystem function because |
nutrients and other life-sustaining molecules are in limited supply and must be continually recycled |
An ecosystem is unlikely to be limited by the supply of_____because it is obtained from the air |
carbon |
Ecosystem |
consists of all the organisms living in a community, as well as the abiotic factors with which they interact |
Ecosystems range fro a microcosm |
such as an aquarium, to a large area, such as a lake or forest |
Its dynamics involve two main processes |
energy flow and chemical cycling |
The first law of thermodynamics states that |
energy cannot be created nor destroyed, only transformed |
Energy enters an ecosystem |
as solar radiation, is conserve,d and is lost from organisms as heat |
The second law of thermodynamics states that |
every exchange of energy increases the entropy of the universe |
In an ecosystem, energy conversions |
are not completely efficient, and some energy is always lost as heat |
The law of conservation of mass states |
that matter cannot be created or destroyed |
Chemical elements are continually |
recycled with ecosystems |
Autotrophs build molecules |
themselves using photosynthesis or chemosynthesis as an energy source |
Heterotrophs depend on |
the biosynthetic output of other organisms |
Energy and nutrients pass from |
primary producers to primary consumers to secondary consumers to tertiary consumers |
Detritivores, or decomposers are |
consumers that derive their energy from detritus, nonliving organic matter |
In most ecosystems, primary production is the |
amount of light energy converted to chemical energy by autotrophs during a given time period |
In a few ecosystems chemoautotrophs |
are the primary producers |
The about of solar radiation reaching Earth’s surface limits |
the photosynthetic output of ecosystems |
Only a small fraction of solar energy |
actually strikes a photosynthetic organisms, and even less is of a usable wavelength |
Total primary production is known as the ecosystem’s |
gross primary production (GPP) |
Net primary production (NPP) is |
GPP minus energy used by primary producers for respiration |
NPP is expressed as |
energy per unit per unit time, or biomass added per unit area per unit time |
Only NPP is |
available to consumers |
Tropical rain forests, estuaries, and coral reefs are among |
the most productive ecosystems per unit area |
Net ecosystem production (NEP) is |
a measure of the total biomass accumulation during a given period |
NEP is gross primary production |
minus the total respiration of all organisms (producers and consumers) in an ecosystem |
In marine and freshwater ecosystems, |
both light and nutrients control primary production |
Light limitation |
depth of light penetration affects primary production in the photic zone of an ocean or lake |
A limiting nutrient is the |
element that must be added for production to increase in an area |
Nitrogen and phosphorous are the nutrients |
that most often limit marine production |
Upwelling of nutrient-rich waters in parts of the oceans |
contributes to regions of high primary production |
The addition of large amounts of nutrients to lakes has a |
wide range of ecological impacts |
In some areas, sewage runoff has caused |
eutrophication of lakes,which can lead to loss of most fish species |
In lakes, phosphorous limits cyanobacterial growth |
more often than nitrogen. This has led to the use of phosphate-free detergents |
On a more local scale, a soil nutrient is often |
a limiting factor in primary production |
In terrestrial ecosystems |
nitrogen is the most common limiting nutrient |
Phosphorous can also be |
a limting nutrient, especially in older soils |
Various adaptations help plants access limiting nutrients from soil |
some plants from mutualizes with nitrogen-fixing bacteria; many plants from mutualisms with mycorrhizal fungi-these fungi supply plants with phosphorous and other limiting elements; roots have root hairs that increases surface area; many plants release enzymes that increase the availability of limiting nutrients |
Secondary production of an |
ecosystem is the amount of chemical energy in food converted to new biomass during a given period of time |
When a caterpillar feeds on a leaf |
only about 1/6 of the leaf’s energy is used in secondary production |
An organisms’ production efficiency |
is the fraction of energy stored in food that is not used for respiration |
Production efficiency = |
net secondary production/ assimilation of primary production X 100% |
Trophic efficiency is the |
percentage of production transferred from one trophic level to the next; about 10% with a range of 5-20% |
Approximately .1% of chemical energy fixed by photosynthesis |
reaches a tertiary consumer |
Life depends on |
recycling chemical elements |
Biogeochemical cycles |
nutrient cycles in ecosystems involve biotic and abiotic components |
Gaseous carbon, oxygen, sulfur, and nitrogen occur |
in the atmosphere and cycle globally |
Less mobile elements such as |
phosphorus, potassium, and calcium cycle locally in terrestrial systems but more broadly when dissolved in aquatic systems |
In studying cycling of water, carbon, nitrogen, and phosphorous, ecologists focus on four factors |
each chemical’s biological importance; forms in which each chemical is available or used by organisms; major reservoirs for each chemical; key processes driving movement of each chemical through its cycle |
Water is essential to all organisms |
comprises large percent of most organisms |
Water is primarily used in |
liquid form, though it is found in liquid, gas, and solid forms |
The oceans 97% glaciers |
polar ice caps 2% lakes, river,s and groundwater 1% |
Carbon based organic molecules |
are essential to all organisms |
Photosynthetic organisms |
convert CO2 to organic molecules that are used by heterotrophs |
Reservoirs |
fossil fuels, soils and sediments, solutes in oceans, plant and animal biomass, the atmosphere, and sedimentary rocks |
Photosynthesis and respiration |
volcanoes and the burning of fossil fuels |
Main reservoir atmosphere (N2) |
plants use NH4+ or NO3-animals consume organic forms |
Phosphate (PO4-3-) |
is the most important inorganic form of phosphorus |
The largest reservoirs |
sedimentary rocks of marine origin, the oceans, and organisms |
The water cycle |
precipitation over ocean; movement over land by mind; evaporation from ocean; evapotranspiration from land; runoff and groundwater; precipitation over land; percolation through soil |
The carbon cycle |
burning of fossil fuels and wood; phytoplankton; consumers; decomposition; consumers; cellular respiration; photosynthesis; CO2 in atmosphere Carbon based organic molecules are essential to all organisms |
The nitrogen cycle |
component of amino acids, proteins, and nucleic acids |
The phosphorous cycle |
component of nucleic acids, phospholipids, and ATP |
Decomposers (detritivores) play a key role in |
general pattern of chemical cycling |
Rates at which nutrients cycle in different ecosystems |
vary greatly, mostly as a result of differing rates of decomposition |
The rate of decomposition is controlled by |
temperature, moisture, and nutrient availability |
Rapid decomposition results in |
relatively low levels of nutrients in the soil |
Cold and wet ecosystems store large amounts of |
undecomposed organic matter as decomposition rates are low |
They found at 60% of the precipitation |
exits through streams and 40% is lost by evapotranspiration |
Deforested site-water losses 30-40% |
greater than in control site nutrient loss also much greater |
Restoration ecology seeks to initiate or speed up |
the recovery of degraded ecosystems |
Strategies include physical reconstruction, bioremediation |
and augmentation of ecosystems processes |
Physical reconstruction |
gravel and clay mine site |
Bioremediation |
is the use of organisms (usually prokaryotes, fungi, or plants) to detoxify ecosystems |
These organisms can take up, and sometimes metabolize |
toxic molecules |
The bacterium can metabolize uranium and other elements to |
insoluble forms that are less likely to leach into streams and groundwater |
Biological augmentation |
uses organisms to add essential materials to a degraded ecosystem; nitrogen-fixing plants can increase the available nitrogen in soil; adding mycorrhizal fungi can help plants to access nutrients from soil |
Release animals at a site |
or establish corridors to help them reach a restored site |
The newness an complexity of restoration ecology require |
that ecologists consider alternative solutions and adjust approaches based on experience |
Kissimmee River, Florida |
filled in canal; restoring natural flow patterns to a riverine system |
Tropical dry forest, Costa Rica |
tree dispersed as seed by livestock; restoring tropical dry forest in former pasturelands |
Coastal Japan |
restoring seaweed and seagrass beds that have been reduced by development |
Maungatautari, New Zealand |
excluding exotic mammals from a reserve located on a forested volcanic cone |
Bio Ch. 55
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