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Lesson 8 – Ecosystems
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1.       Which of the following organisms is incorrectly paired with its trophic level?
a.   cyanobacteria—primary producer.
b.   grasshopper—primary consumer.
c.   zooplankton—secondary consumer.
d.   eagle—tertiary consumer.
e.   fungi—detritivore.

2.       One of the lessons from a pyramid of production is that
a.   only one half of the energy in one trophic level is passed on to the next level.
b.   most of the energy from one trophic level is incorporated into the biomass of the next
c.   the energy lost as heat or lost in cellular respiration is 10% of the available energy of
      each trophic level.
d.   production efficiency is highest for primary consumers.
e.   eating grain-fed beef is an inefficient means of obtaining the energy trapped by

3.       The role of decomposers in the nitrogen cycle is to
a.   fix N2 into ammonia.
b.   release ammonia from organic compounds, thus returning it to the soil.
c.   denitrify ammonia, thus returning N2 to the atmosphere.
d.   convert ammonia to nitrate, which can then be absorbed by plants.
e.   incorporate nitrogen into amino acids and organic compounds.

4.       The recent increase in atmospheric CO2 concentration is mainly a result of an increase in
a.   primary production.
b.   the biosphere's biomass.
c.   the absorption of infrared radiation escaping from Earth.
d.   the burning of fossil fuels and wood.
e.   cellular respiration by the exploding human population.

5.       Which of the following is a result of biological magnification?
a.   Top-level predators may be most harmed by toxic environmental chemicals.
b.   DDT has spread throughout every ecosystem and is found in almost every organism.
c.   the greenhouse effect will be most significant at the poles.
d.   Energy is lost at each trophic level of a food chain.
e.   Many nutrients are being removed from agricultural lands and shunted into aquatic

6.       Which of these ecosystems has the lowest primary production per square meter?
a.   a salt marsh
b.   an open ocean
c.   a coral reef
d.   a grassland
e.   a tropical rain forest

7.       Quantities of mineral nutrients in soils of tropical rain forests are relatively low because
a.   the standing crop is small.
b.   microorganisms that recycle chemicals are not very abundant in tropical soils.
c.   the decomposition of organic refuse and reassimilation of chemicals by plants occur
d.   nutrient cycles occur at a relatively slow rate in tropical soils.
e.   the high temperatures destroy the nutrients.

8.       Coastal water polluted with phosphate and nitrogenous compounds from duck farms showed detectable levels of phosphates but not nitrogen. In experiments, algae were grown in water samples that were controls or enriched with phosphate or ammonium. The greatest algal growth was observed in the nitrogen enriched samples; phosphate-enriched and control samples both had similar growth. From these results, one could conclude that
a.   reducing the levels of phosphate in these waters will not help reduce phytoplankton production.
b.   adding nitrogen to these waters will help reduce eutrophication.
c.   the high levels of phosphates in the water is helping to control algal growth.
d.   nitrogen is the limiting nutrient in these waters.
e.   both a and d are reasonable conclusions.

9.       Which of the following contributes most to the rate of chemical cycling in an ecosystem?
a.   the rate of primary production
b.   the efficiency of secondary production
c.   the rate of decomposition
d.   the trophic efficiency of the ecosystem
e.   the location of available nutrients in inorganic or organic compartments.

10.    Which of the following statements best describes the movements of energy and nutrients in ecosystems?
a.   Energy and nutrients flow through
b.   Energy cycles and nutrients recycle
c.   Energy increases and nutrients cycle
d.   Energy flows through and nutrients cycle
e.   Energy and nutrients cycle

11.    What happens to 99% of the energy that reaches the earth's atmosphere?
a.   It is captured by plants and used in photosynthesis
b.   It is destroyed by the atmosphere
c.   It is used as heat by animals
d.   It is absorbed by rocks on the earth's crust
e.   It is reflected or absorbed by the atmosphere

12.    How much of the energy that reaches the earth's outer atmosphere from the sun is available for photosynthesis in plants at the surface?
a.   25%
b.   21%
c.   14%
d.   5%
e.   1%

13.    Only a small percentage of the energy that arrives at the outer atmosphere of earth reaches the surface and is then captured within ecosystems. What percentage is captured by the photosynthetic organisms?
a.   5%
b.   3%
c.   1%
d.   0.03%
e.   0.0001%

14.    How much of the light energy that reaches a plant is used in photosynthesis to make sugar?
a.   100%
b.   25%
c.   15%
d.   8%
e.   3% or less

15.    If a bird eats an insect that ate a plant, the bird would be considered a(n)
a.   Autotroph
b.   Primary producer
c.   Primary consumer
d.   Secondary consumer
e.   Tertiary consumer

16.    If a wolf eats a rodent that ate a smaller insect that ate a plant, the wolf would be a(n)
a.   Autotroph
b.   Primary producer
c.   Primary consumer
d.   Secondary consumer
e.   Tertiary consumer

17.    If the plants in a community produce 500 grams of organic matter per square meter per year that is available for animals in the community to eat, this amount (500 g per m2 per yr) is known as the
a.   Availability factor of the community
b.   Net primary productivity of the community
c.   Consumership of the community
d.   Secondary productivity of the community
e.   Trophic factor of the community

18.    The amount of life that can be supported by an ecosystem is determined by the
a.   Efficiency of the consumers
b.   Number of producers and their efficiency
c.   Number of heterotrophs
d.   Number of chemoautotrophs
e.   Efficiency of the heterotrophs

19.    Organisms that must rely on the complex high energy molecules produced by other organisms for survival are
a.   Heterotrophs
b.   Producers
c.   Autotrophs
d.   Denitrifying bacteria
e.   Cyanobacteria

20.    Which of the following would NOT be likely to limit the primary productivity of an ecosystem?
a.   The kind of consumers
b.   The amount of light
c.   The temperature
d.   The availability of nutrients
e.   The amount of water

21.    The first trophic level of an ecosystem are
a.   Primary consumers
b.   Detritus feeders
c.   Secondary consumers
d.   Producers
e.   Heterotrophs

22.    When researchers measure the amount of plant biomass in an ecosystem, they are measuring the
a.   Carnivores
b.   Phytoplankton
c.   Net primary productivity
d.   Autotrophic potential
e.   Trophic levels

23.    A carnivore is a
a.   Primary producer
b.   Secondary producer
c.   Primary consumer
d.   Secondary consumer
e.   Tertiary consumer

24.    Which best illustrates the movement of energy through an ecosystem?
a.   Food chain
b.   Food web
c.   Biological magnification
d.   Nutrient cycles
e.   Trophic chain

25.    An important and often overlooked group of organisms that releases nutrients to soil or water is
a.   Producers
b.   Heterotrophs
c.   Decomposers
d.   Tertiary consumers
e.   Autotrophs

26.    Without decomposers and detritus feeders in an ecosystem
a.   Plants would die
b.   Plants would develop nutrient deficiencies
c.   Dead material would accumulate
d.   The soil quality would get poorer
e.   All of these

27.    The transfer of energy from one trophic level to the next is
a.   Reciprocol (two way)
b.   Slow
c.   Inefficient
d.   Difficult
e.   Impossible, only nutrients are transferred

28.    The energy lost as it passes from one trophic level to another is approximately
a.   99%
b.   90%
c.   75%
d.   63%
e.   50%

29.    If a field contains approximately 1000 kilocalories of energy in grass, which is eaten by crickets, which are eaten by birds, approximately how many kilocalories of energy could be in the birds which live in this field?
a.   1000
b.   900
c.   100
d.   90
e.   10

30.    Which of these toxic materials is known to cause human health problems because of biological magnification?
a.   DDT
b.   Mercury
c.   Radioactive compounds
d.   Chlorinated hydrocarbons
e.   All of these

31.    A carnivorous plant, such as a sundew, can be considered a ______________ when it eats a predaceous spider.
a.   tertiary consumer and a producer
b.   secondary consumer and a producer
c.   primary consumer and a producer
d.   primary consumer and a secondary consumer
e.   primary consumer and a tertiary consumer

32.    The amount of energy captured by plants and made available to consumers in an ecosystem is termed:
a.   Net primary productivity
b.   Energy pyramid
c.   Biological magnification
d.   Nutrient cycling
e.   Secondary trophic level

33.    Certain bacteria and fungi that are important in nutrient recycling because they release nutrients from dead organisms back into the ecosystem are:
a.   Autotrophs
b.   Carnivores
c.   Detritus feeders
d.   Decomposers
e.   Recyclers

34.    What ecological effects are suspected or have been linked to biological magnification of chlorinated hydrocarbons such as DDT, dioxin, and PCB's?
a.   Declining insect populations
b.   Water pollution
c.   Interference with animal reproduction
d.   Disruption of the carbon cycle
e.   Interference with the hydrological cycle

35.    Three major reservoirs of carbon are:
a.   Rocks, atmosphere, guano
b.   Acid precipitation, carbon-fixing bacteria, oceans
c.   Soil, water, atmosphere
d.   Fossil fuels, legumes, micronutrients
e.   Oceans, atmosphere, fossil fuels

36.    Herbivores may be classified as:
a.   autotrophs
b.   producers
c.   heterotrophs
d.   metatrophs
e.   a and b

37.    Autotrophs gain energy from
a.   primary producers
b.   secondary consumers
c.   secondary producers
d.   omnivores
e.   sun and chemical energy

38.    Net primary production is
a.   energy that photosynthetic organisms make available to other organisms over a given time
b.   energy stored by secondary consumers from primary biomass
c.   energy made by autotrophs minus energy consumed by heterotrophs, and measured as biomass
d.   heterotrophic production per unit land per unit time
e.   heterotrophic production minus autotrophic production per unit land per unit time

39.    Carnivores are
a.   secondary consumers
b.   primary consumers
c.   omnivores
d.   detrital consumers
e.   consumer producers

40.    Detrital feeders consume
a.   herbivores
b.   plants and plant debris
c.   secondary consumers and primary debris
d.   dead organic matter
e.   fungi and bacteria

41.    Detrital feeders serve to
a.   reduce organic matter accumulation
b.   return nutrients to the soil
c.   regulate fungal populations
d.   a and b
e.   a, b, and c

42.    A snake that eats a small rabbit that feeds on grass would be classified as a(n)
a.   autotroph
b.   primary producer
c.   secondary consumer
d.   primary consumer
e.   tertiary consumer

43.    In a grassland of Kansas, 1000 grams of grass are produced per square meter per year by all the different grass species. A theoretical upper limit to the biomass of secondary consumers that can be supported in this ecosystem is
a.   1000 grams
b.   100 grams
c.   10 grams
d.   1 gram
e.   0.1 grams

44.    The pathways that macronutrients and micronutrients follow through ecosystems are
a.   Energy cycles
b.   Nutrient cycles
c.   Carbon cycle
d.   One way
e.   Reservoirs

45.    Which of the following is NOT involved with the carbon cycle?
a.   Limestone
b.   Fixation
c.   Calcium carbonate
d.   Decomposers
e.   Cellular respiration

46.    Which of the following is NOT involved with the nitrogen cycle?
a.   Fixation
b.   Legumes
c.   Decomposers
d.   Crystalline rock
e.   Ammonia

47.    Plants need nitrogen to synthesize all the following except:
a.   Amino acids
b.   Nucleic acids
c.   Complex polysaccharides
d.   Vitamins
e.   Proteins

48.    Which of the following are ways that nitrogen can be made available to organisms?
a.   Decomposers
b.   Nitrogen fixation by bacteria
c.   Electrical storms
d.   Burning forests and fossil fuels
e.   All the above

49.    The phosphorus cycle includes all but which of the following components?
a.   Atmosphere
b.   Some rocks and soil
c.   Producers
d.   Consumers
e.   Decomposers

50.    Phosphate fertilizers have increased the amount of phosphate in lakes and other bodies of water. What effect does this have on the producers in the water?
a.   It kills them.
b.   It stimulates their growth.
c.   It increases their likelihood of getting eaten.
d.   It causes them to form toxic compounds.
e.   It reduces their photosynthetic capacity.

51.    A crucial nutrient reservoir of phosphorous that is available to organisms is
a.   Atmosphere
b.   Sedimentary rocks
c.   Oceans
d.   Autotrophs
e.   Consumers

52.    Phosphorous, which is very commonly a limiting nutrient in ecosystems, is very important because it
a.   Is needed for molecules such as ATP, cell membranes and nucleic acids
b.   Evaporates quickly
c.   Is found only in sedimentary rocks
d.   Is necessary for the production of cellulose so that autotrophs can grow and provide food for
e.   Is part of the hydrologic cycle

53.    The hydrologic cycle is different from other nutrient cycles in that
a.   Water is chemically unchanged throughout the cycle
b.   The ocean is involved
c.   The atmosphere is involved
d.   The soil is not involved
e.   Water is not recycled, but flows one way through ecosystems

54.    Nitrogen fixation
a.   is due to a lack of decomposers, and causes nitrogen to accumulate in dead organic matter
b.   is the conversion of ammonium to nitrate
c.   is the conversion of nitrate to ammonium
d.   is undertaken by denitrifying bacteria
e.   is the synthesis of ammonium by certain bacteria and cyanobacteria

55.    Limestone is part of the biogeochemical cycle of
a.   N, because denitrifying bacteria gain energy from shell organisms
b.   C, because limestone represents a marine sink for carbon
c.   N, because marine producers may use shell organisms for cellular respiration
d.   C, because shell organisms represent the highest trophic level in marine waters
e.   both a and c

56.    A major ecological concern, the Greenhouse Effect, is caused by:
a.   The release of heat energy from burning fossil fuels
b.   The release of carbon dioxide from the burning of wood, coal, and oil
c.   The destruction of ozone in the upper atmosphere
d.   Overuse of fertilizers in farming
e.   Global warming

57.    Why is the concentration of carbon dioxide rapidly increasing in the earth's atmosphere?
a.   The earth is warming.
b.   More photosynthesis is occurring.
c.   The ozone layer has become much thinner.
d.   Human activities.
e.   The oceans are cooling.

58.    The assaults of acids dissolved in precipitation and dry particles of sulfuric acid are together known as
a.   Acid rain
b.   Acid precipitation
c.   Acid deposition
d.   Acid fog
e.   Decomposition acid

59.    Which of the following best describes a lake that has been severely polluted by acid rain?
a.   Cloudy water with few organisms
b.   Cloudy water with many algae crowding out other organisms
c.   Cloudy water with large numbers of insect larvae
d.   Crystal clear water with large numbers of algae, but no animals
e.   Crystal clear water with few organisms

60.    Which of these is NOT a result of acid rain?
a.   Dead lakes
b.   Damaged statues
c.   Global warming
d.   Injured plants
e.   Mercury biological magnification

61.    How do carbon dioxide and other greenhouse gases cause the temperature of the earth to increase?
a.   By allowing greater transmission of incoming solar radiation.
b.   By absorbing heat energy and holding it near the earth.
c.   By increasing plant respiration.
d.   By reducing photosynthetic rates.
e.   By increasing the amount of radiation from the earth's surface.

62.    Burning coal and oil to release energy also releases ________ which are overloading nutrient cycles of earth.
a.   Sulfur, carbon, nitrogen
b.   Sulfur, oxygen, acid
c.   Phosphorous, carbon, nitrogen
d.   Oxygen, methane, sulfur
e.   Nitrogen, phosphorus, potassium

63.    What are the sources of sulfur in the atmosphere?
a.   Equal amounts of sulfur are released from natural and human sources.
b.   Volcanoes, hot springs, but mostly (over 90%) from human activities such as burning coal.
c.   Mostly (over 90%) from volcanoes, and photosynthetic bacteria.
d.   Mostly from transportation sources such as autos, trucks, and planes.
e.   Decomposition and small amounts from pollution.

64.    Which of the following would NOT be an expected result of global warming?
a.   Ocean level rise
b.   Acidified lakes
c.   Change in forest composition
d.   Change in rainfall patterns
e.   Agricultural disruption

65.    Human-caused disturbances of which biogeochemical cycle may be contributing to global warming?
a.   Hydrologic
b.   Carbon
c.   Nitrogen
d.   Phosphorus
e.   Sulfur

66.    Acid precipitation is the result of interference with which biogeochemical cycles?
a.   sulfer and nitrogen
b.   sulfer and hydrologic
c.   hydrologic and nitrogen
d.   hydrologic and phosphorus
e.   sulfer and phosphorus

67.    Possible consequences of global warming include:
a.   Rise in sea-level
b.   Shifts in temperature and rainfall patterns
c.   Alteration of range and species composition of forests
d.   Changes in ocean currents
e.   All of the above

68.    By the end of the 21st century, global warming is expected to increase average global air temperatures by how much?
a.   less than 1
° C
b.   1.5 to 4.5
° C
c.   5 to 8.5
° C
d.   9 to 12
° C
e.   more than 12
° C

69.    Which of the following statements about the hydrologic cycle is incorrect?
a.   The hydrologic cycle is driven by solar energy that evaporates water
b.   The ocean is the major water reservoir for the entire planet
c.   Little water is used in the synthesis of other molecules in living organisms
d.   Freshwater ecosystems use a hydrologic cycle which is separate from the marine hydrologic
e.   Gravity acts to pull water from the atmosphere in the form of precipitation

70.    When you observe a lake that has been affected by acidic deposition, you might expect to find
a.   a clear lake with high levels of cations and metals
b.   a murky lake with excess algal growth from the deposition of anthropogenic N
c.   low levels of cations and nutrients essential for growth of biotic organisms
d.   excess carbon that will contribute to global warming
e.   high levels of dissolved sulfur dioxide

71.    The greenhouse effect is
a.   the ability of SO2 and NO2 to retain heat in the lower atmosphere
b.   the ability of SO2 and NO2 to retain heat in the upper atmosphere
c.   the ability of certain gases to absorb solar heat and reflect the heat as short-wave radiation to the
d.   the ability of certain gases to retain solar radiation as heat energy
e.   the ability of structures created by humans to retain solar energy as short-wave radiation



72.    Which ecosystems are more productive, tropical rain forests or northern coniferous forests and why?

73.    Draw a food chain for a vacant city lot which has weeds, seed-eating mice, cats, and grasshoppers. Explain what would happen if an animal came in that ate both mice and cats.

74.    Explain why a food web gives a better picture of a community than does a food chain.

75.    Explain why decomposers and detritus feeders are so important to ecosystems.

76.    Describe which trophic level, primary consumers or secondary consumers, has more biomass in any ecosystem and explain why.

77.    Plants produce biomass by taking in energy, CO2 and nutrients from the environment; consumers eat much of this biomass, but not all. However, ecosystems do not indefinitely accumulate large quantities of organic matter over time. Why not?

78.    Draw a typical energy pyramid for a grassland ecosystem. Give examples of trophic levels with potential organisms that occupy the different trophic levels. Explain why the energy pyramid is shaped the way that it is.

79.    Why is phosphorus so important to living organisms?

80.    The global phosphorus cycle is described as a "cycle" yet there is no atmospheric component. P weathers from rocks, and enters the soil. Once P is incorporated into plants or animals, is it ever returned to the rock phase? How?

81.    Nitrogen is fixed by soil bacteria and is then incorporated into plant biomass, and eventually into the food chain. What process(es) complete the global N cycle?

82.    Why is acid rain more of a problem in certain areas, such as New England than in others?

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