Ecosystem Energy Flow and Food Webs
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Questions and Answers

Approximately what proportion of the radiant energy entering an ecosystem is used in photosynthesis?

1%

Which pair best represents photosynthetic organisms?

  • Decomposer and consumer
  • Primary producer and heterotroph
  • Carnivore and herbivore
  • Primary producer and autotroph (correct)

    • They include bacteria but not fungi.

    True

    There is a one-way flow of energy through the food webs of ecosystems.

    <p>True</p> Signup and view all the answers

    A linear depiction of energy flow in an ecosystem is a(n) ______.

    <p>food chain</p> Signup and view all the answers

    Mice consumption of grasses is harmful to the grass population.

    <p>True</p> Signup and view all the answers

    Which trophic level would contain the lowest quantity of energy (kcal per m2)?

    <p>Tertiary consumers</p> Signup and view all the answers

    A food web is a more realistic depiction than a food chain because _____

    <p>organisms rarely eat just one kind of food</p> Signup and view all the answers

    The accompanying figure represents a _____

    <p>pyramid of biomass</p> Signup and view all the answers

    Pyramids of numbers are of limited usefulness because they do not indicate the biomass of the organisms at a given time.

    <p>True</p> Signup and view all the answers

    What key factor limits the number of trophic levels in an ecosystem?

    <p>Energy loss</p> Signup and view all the answers

    Biomass reduction from one trophic level to the next is approximately 50%.

    <p>True</p> Signup and view all the answers

    In an ecosystem, which measure of energy is the largest in amount or rate?

    <p>Gross primary productivity</p> Signup and view all the answers

    Net primary productivity represents _____

    <p>the amount of biomass in excess of that needed to support plant cell respiration</p> Signup and view all the answers

    Arrange the following from the ecosystem with the smallest average NPP to the ecosystems with the largest NPP: 5, 1, 2, 3, 4.

    <p>5, 1, 2, 3, 4</p> Signup and view all the answers

    The accompanying figure is a good illustration of _____

    <p>biological magnification</p> Signup and view all the answers

    In the accompanying figure, the gull has the highest concentration of DDT because it is at the top of the food chain.

    <p>True</p> Signup and view all the answers

    Organisms that eat plants exclusively are known as _____

    <p>herbivores</p> Signup and view all the answers

    An owl has a positive impact on the grass population.

    <p>False</p> Signup and view all the answers

    GPP, or Gross Primary Productivity, is _____

    <p>the total energy captured from the sun through photosynthesis</p> Signup and view all the answers

    The effect of DDT on birds is a result of which three characteristics of DDT?

    <p>Persistence, bioaccumulation, and biological magnification</p> Signup and view all the answers

    A pyramid of energy shows that energy decreases as one goes toward the apex of the pyramid.

    <p>True</p> Signup and view all the answers

    What is the third trophic level of a food chain?

    <p>Secondary consumers</p> Signup and view all the answers

    What ecosystem has the highest rate of primary productivity?

    <p>Algal beds and reefs</p> Signup and view all the answers

    The major components of Earth's atmosphere, from the lowest concentration to the greatest concentration, are _____

    <p>carbon dioxide, oxygen, and nitrogen</p> Signup and view all the answers

    Which process plays the most important role in the phosphorous cycle?

    <p>Erosion</p> Signup and view all the answers

    Which process is not involved in the hydrologic cycle?

    <p>Nitrification</p> Signup and view all the answers

    Transpiration is most closely associated with _____

    <p>terrestrial plants</p> Signup and view all the answers

    Dissolved phosphorus in aquatic ecosystems may return to the land via _____

    <p>birds eating fish and mollusks</p> Signup and view all the answers

    Which of the following processes restores nitrogen to the air?

    <p>Denitrification</p> Signup and view all the answers

    Fixation of carbon is accomplished by _____

    <p>photosynthetic organisms</p> Signup and view all the answers

    A primary source of carbon for photosynthetic organisms is _____

    <p>carbon dioxide in the atmosphere and water</p> Signup and view all the answers

    Which process does not return carbon to the atmosphere?

    <p>True</p> Signup and view all the answers

    Since 1750, which of the following has/have absorbed the most carbon dioxide from the atmosphere?

    <p>Oceans</p> Signup and view all the answers

    To date, humans have interfered with all of the biogeochemical cycles on Earth, but this interference has been of the greatest magnitude, in terms of human-induced changes in climate, in the _____

    <p>carbon cycle</p> Signup and view all the answers

    Fossil fuels, such as coal and oil, are derived from which biogeochemical cycle?

    <p>The carbon cycle</p> Signup and view all the answers

    The event in human history that changed the natural balance of the carbon cycle was the Industrial Revolution.

    <p>True</p> Signup and view all the answers

    The main steps of the nitrogen cycle are _____

    <p>nitrogen fixation, nitrification, assimilation, ammonification, and denitrification</p> Signup and view all the answers

    Which is the greatest sink of phosphorus?

    <p>Marine sediments</p> Signup and view all the answers

    Bacteria are most essential in the cycling of _____

    <p>nitrogen</p> Signup and view all the answers

    Nitrogen is a critical requirement for living organisms because it is a component of _____

    <p>nucleic acids and proteins</p> Signup and view all the answers

    Which step of the nitrogen cycle is not performed by most bacteria?

    <p>True</p> Signup and view all the answers

    Nitrogen-fixing bacteria convert gaseous nitrogen into _____

    <p>ammonia</p> Signup and view all the answers

    Plant roots absorb nitrate or ammonia and incorporate these compounds into plant proteins via the process of _____

    <p>assimilation</p> Signup and view all the answers

    Bacterial decomposition of organic nitrogen results in the production of _____

    <p>atmospheric nitrogen</p> Signup and view all the answers

    Denitrifying bacteria _____

    <p>convert nitrate into atmospheric nitrogen</p> Signup and view all the answers

    The enzyme nitrogenase is important in which part of the nitrogen cycle?

    <p>Nitrogen fixation</p> Signup and view all the answers

    How are bacteria important to the genus Rhizobium?

    <p>They provide fixed nitrogen to legumes.</p> Signup and view all the answers

    Which nutrient cycle does not have a gaseous phase?

    <p>Phosphorus cycle</p> Signup and view all the answers

    Which issue is least likely to have been the result of human impact on the nitrogen cycle?

    <p>El Niño-Southern Oscillation events</p> Signup and view all the answers

    During the cycling of phosphorus, which biological process is critical in cycling dissolved phosphorus?

    <p>Decomposition</p> Signup and view all the answers

    The 'sun's energy is produced by _____

    <p>nuclear fusion reactions</p> Signup and view all the answers

    On average, clouds and surfaces, especially snow, ice, and the ocean, immediately reflect away _____% of the solar radiation that falls on Earth.

    <p>30</p> Signup and view all the answers

    Solar radiation powers the hydrologic and other biogeochemical cycles.

    <p>True</p> Signup and view all the answers

    The primary reason that Earth experiences seasons is because of _____

    <p>Earth's tilt on its axis</p> Signup and view all the answers

    The Coriolis effect results in _____

    <p>the deflection of moving air due to the rotation of Earth</p> Signup and view all the answers

    The ultimate source of energy for the communities of the hydrothermal vents is provided by _____

    <p>chemoautotrophic prokaryotes</p> Signup and view all the answers

    In large measure, differences in _____ that are due to variations in the amount of _____ at different locations on Earth drive the circulation of the atmosphere.

    <p>rainfall; solar energy</p> Signup and view all the answers

    The clockwise gyre of surface ocean currents in the North Atlantic results in warmer water on Atlantic beaches of North America than Pacific beaches of the same latitude.

    <p>True</p> Signup and view all the answers

    Which of the following directly drives ocean surface circulation patterns?

    <p>Winds</p> Signup and view all the answers

    Drier climates tend to prevail in a rain shadow.

    <p>True</p> Signup and view all the answers

    What two abiotic factors are considered to most affect organisms?

    <p>Temperature and water</p> Signup and view all the answers

    Which process is NOT indirectly related to absorption of solar energy by the Earth's surface?

    <p>True</p> Signup and view all the answers

    The atmosphere performs several essential ecological functions. One of these is to _____

    <p>protect Earth from most ultraviolet radiation</p> Signup and view all the answers

    What is the least likely effect of fires on organisms?

    <p>Fire instigates the growth of shade-tolerant plants</p> Signup and view all the answers

    What did Stephen Carter and his team from the University of Madison-Wisconsin study?

    <p>Tipping points for endangered food webs</p> Signup and view all the answers

    Study Notes

    Ecosystem Energy Flow

    • Approximately 1% of radiant energy entering an ecosystem is utilized in photosynthesis.
    • Photosynthetic organisms include primary producers and autotrophs.
    • Energy flows through ecosystems in a one-way manner, represented by food chains and webs.

    Food Chains and Food Webs

    • A food chain is a linear depiction of energy flow in an ecosystem.
    • Organisms in food chains typically don't consume solely one type of food, leading to the complexity of food webs.
    • Tertiary consumers possess the lowest energy quantity within a trophic level.
    • Secondary consumers represent the third trophic level.

    Biomass and Productivity

    • Biomass typically decreases by roughly 50% from one trophic level to the next.
    • Gross Primary Productivity (GPP) measures the total energy captured by photosynthesis within an ecosystem.
    • Net Primary Productivity (NPP) is the biomass produced after energy used in respiration is accounted for.

    Ecological Pyramids

    • Pyramids of biomass visually represent the distribution of energy at different trophic levels.
    • Pyramids of numbers are less informative as they don't indicate biomass.

    Nutrient Cycling

    • Key cycles include carbon, nitrogen, and phosphorus cycles.
    • Transpiration, primarily associated with terrestrial plants, plays a critical role in nutrient cycling.
    • The largest sinks of carbon dioxide are the oceans and marine sediments.
    • Nitrogen fixation converts gaseous nitrogen into ammonia through bacteria, crucial for the nitrogen cycle.

    Human Impact and Environmental Changes

    • The Industrial Revolution significantly altered the balance of the carbon cycle.
    • Human activity has massively influenced biogeochemical cycles, with notable effects on the carbon cycle.
    • The phosphorus cycle lacks a gaseous phase, making its cycling different from others.

    Climate and Environmental Conditions

    • Earth experiences seasons due to its axial tilt.
    • Average albedo reflects about 30% of solar radiation back into space.
    • Drier climates occur in rain shadow areas, impacted heavily by temperature and water as abiotic factors.

    Ocean Currents and Weather Patterns

    • Ocean surface circulation patterns are directly influenced by wind.
    • The Coriolis effect alters moving air due to Earth's rotation, affecting climate and weather systems.
    • Differences in rainfall and solar energy contribute to atmospheric circulation.

    Research and Ecological Studies

    • Tipping points in endangered food webs were studied by researchers to understand ecological sustainability.
    • The effect of fires on ecosystems includes the promotion of growth among shade-tolerant plants.

    Other Concepts

    • Chemoautotrophic prokaryotes are the primary energy source in hydrothermal vent communities.
    • DDT’s impact on bird populations is explained by its persistence, bioaccumulation, and biological magnification characteristics.

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    Description

    This quiz covers the concepts of energy flow within ecosystems, including the roles of photosynthetic organisms, food chains, and food webs. It also examines biomass, productivity, and ecological pyramids, providing a comprehensive overview of how energy is transferred in various trophic levels. Test your understanding of these key ecological principles.

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