Bio Ch. 55

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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


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


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?


Plants use___as a source of energy


What element is found in all organic compounds?


Plants obtain carbon from

carbon dioxide

What name is given to organisms that convert the carbon in organic compounds into carbon in carbon dioxide?


Where do plants get the energy to make organic molecules?


What is not an organic molecule?


Where do plants get the carbon they use to make organic molecules?

carbon dioxide

Nitrifying bacteria convert___to____


_____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


What is an example of a nitrite


In a biogeochemical cycle, a chemical element spends time in different places called


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


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



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


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


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

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