55
Communities and Ecosystems
TEST FILE QUESTIONS
Fill in the Blank
1. The total amount of energy assimilated by photosynthesis is called _______.
Answer: gross primary production
2. The amount of energy assimilated by photosynthesis after the energy used by plants for
maintenance and biosynthesis is subtracted is called _______.
Answer: net primary production
3. All organisms that get their energy from a common source (e.g., all herbivores)
constitute a _______.
Answer: trophic level
4. The organisms that live together in a particular area constitute an _______.
Answer: ecological community
5. A set of linkages through which a plant is eaten by an herbivore, which in turn is eaten
by a carnivore, and so on, is called a _______.
Answer: food chain
6. Organisms that reduce the remains of other organisms to mineral nutrients that can be
taken up by plants are called _______.
Answer: detritivores
7. A network of linkages connecting a set of plants with a set of herbivores and
carnivores is called a(n) _______.
Answer: food web
8. Two species of Paramecium are placed together in a test tube and one species drives
the other to extinction. This phenomenon is an example of _______.
Answer: competitive exclusion
9. Growth on an area that at first supported no organisms but ends up supporting a mature
forest is called _______.
Answer: succession
10. When the dead body of a freshly killed mouse decomposes, the change in the
community of decomposers in the body is called _______.
Answer: secondary succession
11. Animals such as cows, which eat only plant tissues, are called _______.
Answer: herbivores
12. When a species has a larger influence on the community than its abundance would
lead one to predict, it is called a _______ species.
Answer: keystone
13. Animals that eat other animals are called _______.
Answer: predators
Multiple Choice
1. Which of the following changes would not result in an increase in net primary
production?
a. Increased precipitation in an arid area
b. Increased soil fertility
c. Increased latitude (moving from the equator toward the poles)
d. Moving down a mountain to warmer temperatures
e. Increasing the light in aquatic ecosystems
Answer: c
2. Which of the following always has a “pyramidal” shape, that is, decreasing values at
higher trophic levels?
a. Pyramids of numbers
b. Pyramids of biomass
c. Pyramids of energy
d. Both b and c
e. a, b, and c
Answer: c
3. Which of the following statements about food chains and energy flow through
ecosystems is false?
a. A single organism can feed at several trophic levels.
b. The lower the trophic level at which an organism feeds, the more energy is available.
c. Detritivores feed at all trophic levels except the producer level.
d. Food webs include two or more food chains.
e. All organisms that are not producers are consumers.
Answer: c
4. Assume that the energy transfer efficiency between trophic levels is 10 percent. How
much grain would be required to produce 70 kg of human biomass if the grain is eaten by
cows and the cows are eaten by humans?
a. 210 kg
b. 700 kg
c. 2,100 kg
d. 7,000 kg
e. 70,000 kg
Answer: d
5. Which characteristic of moose is most significant in determining that moose are a
keystone species?
a. A few moose have a large effect on forest succession.
b. Moose are the largest animals in the ecosystem.
c. Moose browse on a large variety of tree species.
d. Moose use both terrestrial and aquatic habitats.
e. Moose care for their young longer than any other species in the ecosystem.
Answer: a
6. If the removal of a species from a community has a greater effect on the structure and
functioning of the community than one would have predicted from the species’
abundance, then that species is most likely a(n)
a. keystone species.
b. carnivore.
c. herbivore.
d. early successional species.
e. mimic of another species.
Answer: a
7. An inverted pyramid of _______ may occasionally be observed in _______
communities.
a. energy; grassland
b. energy; forest
c. biomass; marine
d. biomass; grassland
e. biomass; forest
Answer: c
8. In light, a plant fixes 0.12 ml of CO2 per hour. However, in the dark the same plant
releases 0.04 ml of CO2 per hour. What is the estimated net primary production of this
plant?
a. 0.04 ml/hour
b. 0.08 ml/hour
c. 0.12 ml/hour
d. 0.16 ml/hour
e. 0.0048 ml/hour
Answer: b
9. The sea star Pisaster ochraceous is an abundant predator on the rocky intertidal
communities on the Pacific coast of North America. The sea star feeds preferentially on
the mussel Mytilus californianus. In the absence of the sea star, the mussel is a dominant
competitor. Predation by the sea star, however, creates bare areas. For this reason,
a. the number of species will be changed by the presence of the sea star, but the direction
of change cannot be predicted.
b. the variety of species will be unaffected by the presence or absence of the sea star.
c. the variety of species will be greater when the sea star is present than when it is absent.
d. the variety of species will be smaller when the sea star is present than when it is absent.
e. Mytilus will go extinct when the sea star is present.
Answer: c
10. Which of the following could not be used as an example of succession?
a. A landslide exposes bare rock. Eventually a forest is reestablished on the site.
b. An alien weed is introduced into the Hawaiian Islands. Eventually it displaces a native
plant, driving the native plant to extinction.
c. A freshly killed mouse decomposes.
d. A tree falls in the forest. Eventually a new tree replaces it.
e. The leaf litter under a pine tree is in layers, with freshly fallen litter at the top and more
decomposed layers deeper down.
Answer: b
11. Keystone species may influence the
a. species richness of an ecosystem.
b. flow of energy and materials in an ecosystem.
c. environment of an ecosystem.
d. Both a and b
e. None of the above
Answer: d
12. A community ecologist would most likely be concerned with
a. energy flow through an ecosystem.
b. population growth of a single species.
c. interactions between individuals of the same species living together in a small area.
d. interactions between individuals of different species living together in a small area.
e. the cycling of matter through biotic and abiotic components of an area.
Answer: d
13. Which characteristic is not true of ecological succession?
a. The species composition of the community changes through time.
b. The physical conditions of the community change through time.
c. The rate of change is constant through time.
d. Some species disappear quickly; others are more long-lived.
e. The community becomes more complex through time.
Answer: c
14. Interactions within communities can control populations. Based on community
studies involving white-footed mice, gypsy moths, and oak trees, scientists have
determined that an increase in the mouse population leads to an increase in acorn
production by the oak trees. If the mice prey on the larvae of the moths and the moth
larvae eat the leaves of the oak, how can this be so?
a. Gypsy moths do not influence acorn production.
b. An increase in the mouse population leads to a decrease in the gypsy moth population.
c. An increase in the mouse population leads to an increase in the gypsy moth population.
d. Oak trees produce substances that deter the moth larvae from eating the leaves.
e. Acorn production is not related to the mouse population.
Answer: b
15. Solar energy is an important energy source in all of the following ecosystems except
a. the tropical rainforest.
b. temperate grassland.
c. deserts.
d. upper layers of the oceans.
e. deep-sea hydrothermal vent systems.
Answer: e
16. The greatest amount of energy loss in ecosystems occurs through
a. photosynthesis.
b. respiration.
c. herbivory.
d. excretion.
e. digestion.
Answer: b
17. Average net primary production in the open ocean is low, but it makes up the largest
percentage of net primary production on Earth. Why?
a. Oceans can support only a small number of species.
b. Sunlight is not a limiting factor in primary production in the open ocean.
c. Oceans cover most of Earth, so the total percentage is the highest.
d. Both a and b
e. a, b, and c
Answer: c
18. _______ exhibit _______ primary production due to a lack of moisture.
a. Tropical rainforests; low
b. Open oceans; high
c. Deserts; low
d. Tropical seasonal forests; high
e. Savannas; high
Answer: c
19. An example of species-specific coevolution is
a. yucca plants and the single species of moth that pollinates them.
b. egrets feeding near water buffalo.
c. ants “milking” aphids for honeydew.
d. tropical butterflies that look more similar to each other in each new generation.
e. Both b and d
Answer: a
20. Species richness is influenced by primary productivity. Which of the following
statements regarding this phenomenon is true?
a. As species richness increases, primary production decreases.
b. As species richness decreases, primary production increases.
c. Species richness is highest at an intermediate level of primary production.
d. As primary production increases, species richness continues to increase.
e. Species richness is not influenced by primary production.
Answer: c
21. Species richness has been observed to increase with primary productivity—to a point.
At high levels of productivity, species richness decreases. Which of the following
explains this phenomenon?
a. Competitive exclusion
b. Predation
c. Herbivory
d. Decomposition
e. None of the above
Answer: a
22. Photosynthetic plants are considered to be
a. heterotrophs.
b. consumers.
c. autotrophs.
d. detritivores.
e. predators.
Answer: c
23. Organisms that consume other organisms are called
a. heterotrophs.
b. detritivores.
c. autotrophs.
d. producers.
e. photosynthesizers.
Answer: c
24. Biomass pyramids in the open ocean are inverted in comparison to most terrestrial
ecosystems because
a. primary production is lower in the open ocean.
b. in the open ocean there are fewer consumers than there are producers.
c. most of the biomass is found among the producers.
d. the producers reproduce so rapidly that a smaller biomass of producers can support a
larger biomass of herbivores.
e. most of the biomass is found among the carnivores.
Answer: d
25. Organisms that obtain their food from both primary consumers and another trophic
level are called
a. herbivores.
b. omnivores.
c. detritivores.
d. producers.
e. autotrophs.
Answer: b
26. Organisms that eat herbivores are called
a. tertiary consumers.
b. primary producers.
c. detritivores.
d. secondary consumers.
e. herbivores.
Answer: d
27. Why does a biomass pyramid for a forest show less biomass at the herbivore level
than a grassland does?
a. Forests contain fewer herbivores.
b. Carnivores eat more herbivores in forests.
c. Primary production of forests is higher than that of grasslands.
d. Most of the biomass in a forest is tied up in material that is difficult to digest.
e. Both a and b
Answer: d
28. All of the following are detritivores except
a. insects.
b. fungi.
c. wolves.
d. insects.
e. bacteria.
Answer: c
29. Which of the following are examples of or causes of disturbances?
a. Keystone species
b. Hurricanes
c. Fires
d. Volcanic eruptions
e. All of the above
Answer: e
30. The intermediate disturbance hypothesis states that
a. communities with high levels of disturbance have greater species richness.
b. communities with low levels of disturbance have lower species richness.
c. there is no relationship between species richness and the level of disturbance in a
community.
d. communities with intermediate levels of disturbance have greater species richness.
e. communities with lower species richness have little or no competition.
Answer: d
31. A volcano has decimated a significant portion of the ecosystem around it. Following
this disturbance, what type of process is likely to proceed?
a. Secondary succession
b. Tertiary succession
c. Decomposition
d. Primary succession
e. All of the above
Answer: d
32. _______ succession may begin in an area where dead parts of organisms remain.
a. Secondary
b. Primary
c. Tertiary
d. Quaternary
e. Disturbance
Answer: a
33. During primary succession, what process is important for the reestablishment of the
soil and the colonization of a plant community?
a. Decomposition
b. Predation
c. Disturbance
d. Secondary succession
e. Nitrogen fixation
Answer: e
34. _______ succession begins in areas that lack living organisms.
a. Secondary
b. Primary
c. Tertiary
d. Quaternary
e. Disturbance
Answer: b
35. The formation of the Central American land bridge 4 million years ago led to
a. reduced dispersal of mammals between North and South America.
b. mass extinction of most mammals in North and South America.
c. increased dispersal of mammal species between North and South America.
d. the establishment of a large number of South American mammals in North America.
e. the establishment of a small number of North American mammals in South America.
Answer: c
STUDY GUIDE QUESTIONS
Knowledge and Synthesis Questions
1. Which of the following could not be considered an ecosystem?
a. A small pond
b. All the fish in a coral reef
c. Earth
d. A pile of dung in a pasture
2. Which environmental factor frequently limits primary production in both terrestrial and
aquatic ecosystems?
a. Temperature
b. Moisture
c. Light
d. Nutrient supply
3. A plant in the dark uses 0.02 ml of O2 per minute. The same plant in sunlight releases
0.14 ml of O2 per minute. A correct estimate of its rate of gross primary production is
__________ ml of O2 per minute.
a. 0.02
b. 0.12
c. 0.14
d. 0.16
4. Examine the following food web. Organism 9 is a(n)
a. herbivore.
b. primary carnivore.
c. secondary carnivore.
d. omnivore.
5. The food web shown in Question 4 has __________ trophic levels.
a. three
b. two
c. four
d. five
6. In which of the following ecosystems would you expect to observe the lowest biomass
of primary consumers relative to the biomass of the primary producers?
a. Tropical rainforest
b. Temperate grassland
c. Freshwater lake
d. Open ocean
7. Which of the following is most characteristic of a keystone species?
a. Very abundant
b. Removal having a great effect on community structure
c. Herbivore
d. Uniform distribution
8. Species richness is
a. positively correlated with stability of annual net primary production.
b. often greatest in communities with an intermediate level of primary production.
c. typically greatest in communities experiencing the least amount of disturbance.
d. Both a and b
9. If the following list of stages of ecological succession occurring on glacial moraines in
Alaska were put in correct chronological sequence, which would be third?
a. Arrival of willows and alders
b. Arrival of lichens
c. Arrival of conifers
d. Increase in soil nitrogen content
10. Which of the following would represent primary succession?
a. The development of an aquatic community in a newly excavated farm pond, eventually
followed by the filling in of the pond with sediment and its conversion to a forest
b. The gradual establishment of a forest following a fire that destroyed the previous
community
c. The invasion of weeds followed by shrubs and trees on an abandoned farm field
d. Both a and b
Answers
Knowledge and Synthesis Answers
1. b. An ecosystem includes the environment and the biological community living there.
A coral reef ecosystem would include much more than just the fish.
2. a. Temperature, nutrient supply, and light can limit production in aquatic ecosystems;
temperature and moisture most often limit production on land.
3. d. The amount of production used in maintenance and biosynthesis is added to net
primary production to determine gross primary production. Photosynthetic release of O2
in the light is an estimate of net production; O2 use in the dark is an estimate of
maintenance and biosynthesis costs. You would add 0.02 ml to 0.14 ml to get an estimate
of gross primary production of 0.16 ml per minute.
4. d. Because organism 9 eats from both the primary producer level (1) and the herbivore
level (2), it would be an omnivore.
5. c. Four trophic levels are depicted. The levels are primary producer (1), herbivore (2,
3, 4), primary carnivore (5, 6), and secondary carnivore (7, 8). The omnivore (9) occupies
either the herbivore or primary carnivore level, depending on whether it is feeding on a
primary producer or on an herbivore.
6. a. Compared to grasslands or aquatic ecosystems, forests typically have a lower ratio
of primary consumer biomass to primary producer biomass because trees (the dominant
primary producers) store energy for long periods of time in difficult-to-digest forms.
7. b. By definition, removal of a keystone species has a larger effect on the community
than would be expected based on its abundance.
8. d. Of the first three choices, only c is incorrect. The highest levels of species richness
are associated with intermediate levels of disturbance.
9. d. Of the stages listed, the arrival of lichens would be first, followed by the arrival of
willows and alders, an increase in soil nitrogen content (the correct answer), and finally
the arrival of conifers.
10. a. Succession that begins on a newly available site, like a freshly excavated pond, is
primary. Succession that occurs after disturbances such as fire or the conversion of a
natural community to farmland is considered secondary.
TEXTBOOK SELF QUIZ QUESTIONS
1. An ecological community is
a. all the species of organisms that live and interact with one another in an area.
b. all the species that live and interact in an area together with the abiotic environment.
c. all the species in an area that belong to a particular trophic level.
d. all the species that are members of a local food web.
e. all of the above
2. What is the difference between primary productivity and primary production?
a. Primary productivity is always greater than primary production.
b. Primary productivity is always less that primary production.
c. Primary productivity is a rate, whereas primary production is a product.
d. Primary productivity is a product, but primary production is a rate.
e. There is no real difference between primary productivity and primary production.
3. The total amount of energy that plants assimilate by photosynthesis is called
a. gross primary production.
b. net primary production.
c. biomass.
d. a pyramid of energy.
e. succession.
4. The amount of energy reaching a higher trophic level is determined by
a. net primary production.
b. net primary production and the efficiencies with which food energy is converted to
biomass.
c. gross primary production.
d. gross primary production and the efficiencies with which food energy is converted to
biomass.
e. gross primary production and net primary production.
5. The pyramids of energy and biomass of forests and grasslands differ because
a. forests are more productive than grasslands.
b. forests are less productive than grasslands.
c. large mammals avoid living in forests.
d. trees store much energy in difficult-to-digest wood, whereas grassland plants produce
few difficult-to-digest tissues.
e. grasses grow faster than trees.
6. Keystone species
a. influence the structure of the communities in which they live more than expected on
the basis of their abundance.
b. strongly influence the species composition of communities.
c. may speed up the rate of nutrient cycling.
d. may be herbivores or carnivores.
e. all of the above
7. What is the general relationship between species richness and disturbance?
a. Species richness peaks at low levels of disturbance.
b. Species richness peaks at high levels of disturbance.
c. Species richness peaks at intermediate levels of disturbance.
d. Species richness is less at intermediate levels of disturbance.
e. There is no general relationship between species richness and level of disturbance.
8. Ecological succession is
a. the changes in species over time.
b. the gradual process by which the species composition of a community changes.
c. the changes in a forest as the trees grow larger.
d. the process by which a species becomes abundant.
e. the buildup of soil nutrients.
9. Primary succession begins
a. soon after a disturbance ends.
b. at varying times after a disturbance ends.
c. at sites where some species survived the disturbance.
d. at sites were no species survived the disturbance.
e. at sites where only primary producers survived the disturbance.
10. The South American mammals that became established in North America after
crossing the Central American land bridge include
a. porcupines, armadillos, and caviomorph rodents.
b. porcupines, caviomorph rodents, and Virginia opossums.
c. Virginia opossums, porcupines, and anteaters.
d. Virginia opossums, porcupines, and armadillos.
e. armadillos, anteaters, and caviomorph rodents.
Answers
1. a
2. c
3. a
4. b
5. d
6. e
7. c
8. a
9. d
10. d
ONLINE QUIZ QUESTIONS
1.The species that live and interact in an area constitute a(n)
a.lek.
b.population.
c.ecological community.
d.ecosystem.
e.biome.
Answer: c
2.This type of energy drives almost all biological systems.
a.Solar
b.Chemical
c.Physical
d.Mechanical
e.Electrical
Answer: a
3.The rate at which energy is incorporated into the bodies of photosynthetic organisms is
called
a.gross primary productivity.
b.net primary productivity.
c.secondary productivity.
d.photosynthetic efficacy.
e.photosynthetic efficiency.
Answer: a
4.The energy available to organisms that eat plants is called
a.gross primary productivity.
b.net primary production.
c.secondary productivity.
d.photosynthetic efficacy.
e.photosynthetic efficiency.
Answer: b
5.The number of species living in a community is called
a.population density.
b.population number.
c.species number.
d.species density.
e.species richness.
Answer: e
6.Divisions of organisms in a community based on the way in which they obtain their
energy are called
a.a food chain.
b.trophic levels.
c.a food web.
d.pyramids.
e.consumers.
Answer: b
7.Species whose influences on ecosystems are greater than would be expected on the
basis of their abundance are called
a.primary producers.
b.secondary consumers.
c.flagged species.
d.keystone species.
e.disturbance specialists.
Answer: d
8.Although the consequences of various kinds of disturbances are highly variable, their
results conform to a general pattern. This general pattern generated the
a.intermediate disturbance hypothesis.
b.general disturbance hypothesis.
c.disaster equilibrium theory.
d.general equilibrium theory.
e.intermediate equilibrium theory.
Answer: a
9.A change in community composition following a disturbance is called
a.primary succession.
b.secondary succession.
c.ecological succession.
d.disaster succession.
e.equilibrium succession.
Answer: c
10.The major influence(s) on the composition of ecological communities is
a.primary and secondary succession.
b.ecological and evolutionary events taking place over long time periods and large spatial
scales.
c.secondary productivity.
d.photosynthetic efficacy.
e.community stability and species number.
Answer: b
11.Rain tends to be much more common in mountains than in the adjacent lowlands
because
a. as air travels up the mountains, it cools. Cool air holds less moisture than warm air, and
the excess moisture is dropped as rain.
b. as air travels up the mountains, it is compressed. The mountains squeeze the water out
of the air, which is dropped as rain.
c. because of their great height, mountains are often in the clouds. Precipitation is much
greater in these clouds.
d. as air moves down the mountains, it expands and is unable to form clouds, so no
rainfall occurs.
e. the rainfall is equal in both mountains and lowlands; however, because the rain has
farther to travel from the clouds to the lowlands, more of it evaporates before it reaches
the ground in the lowlands.
Answer: a
12.Rain shadows form on the __________ of mountains and result in _________ rainfall
there.
a. windward side, more
b. windward side, less
c. leeward side, more
d. leeward side, less
e. peaks, more
Answer: d
13.As air rises over a mountain it
a. expands and cools.
b. compresses and cools.
c. expands and heats up.
d. compresses and heats up.
e. compresses.
Answer: a
14.Why does the leeward side of the mountain remain dry?
a. It never rains on the leeward side.
b. There is no moisture near the leeward side.
c. The leeward side is so arid that rain cannot permeate.
d. As air descends the slope, it warms and picks up moisture from the environment.
e. None of the above
Answer: d
15.The windward side of the mountain is moist and lush.
a. true
b. false
Answer: a
16.Which of the following is not a component of integrated pest management?
a. Use of cultural strategies such as crop rotation and mixed plantings
b. Use of pest-resistant strains of crops
c. Use of predators and parasites of crop pests
d. Use of chemical attractants
e. Use of chemical pesticides whenever pests are discovered
Answer: e
17.Which of the following statements concerning the water cycle is false?
a. There is a net movement of water vapor from oceans to terrestrial environments.
b. Precipitation exceeds evaporation on land.
c. Most of the water that evaporates from oceans is returned by runoff from land.
d. Transpiration makes a significant contribution to evaporative water loss from terrestrial
ecosystems.
e. Evaporation exceeds precipitation over the seas.
Answer: c
18.The role of decomposers in the nitrogen cycle is to
a. fix N2 into ammonium.
b. release ammonium and other inorganic nitrogen compounds from organic compounds,
thus returning nitrogen to the soil.
c. denitrify ammonium, thus returning N2 to the atmosphere.
d. convert ammonium to nitrate, which can then be absorbed by plants.
e. incorporate nitrogen into amino acids and organic compounds.
Answer: b
19.The recent increase in atmospheric CO2 concentration is mainly a result of an increase
in
a. primary productivity.
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.
Answer: d