Chapter 31 The Dynamics of Communities and Ecosystems1
Chapter 31: The Dynamics of Communities and Ecosystems
Multiple-Choice Questions
1.Introduction; p. 31-2; easy; ans: b
A(n) ______includes, by definition, all the organisms in a particular place together with their environment.
a.community
b.ecosystem
c.population
d.species
e.biosphere
2.Introduction; p. 31-2; moderate; ans: e
The biosphere consists of all the Earth’s:
a.populations.
b.communities.
c.species.
d.autotrophs and heterotrophs.
e.ecosystems.
3.Introduction; p. 31-3; moderate; ans: d
A community consists of all the ______in a particular area.
a.individuals of a single species
b.plants
c.plants and animals
d.organisms
e.organisms and their environment
4.Ecosystem Energetics–Trophic Levels; p. 31-3; moderate; ans: b
Which of the following is not an autotroph?
a.a chemosynthesizer
b.a mushroom
c.an oak tree
d.a green alga
e.a moss
5.Ecosystem Energetics–Trophic Levels; pp. 31-3—31-4; moderate; ans: e
Which of the following is not a primary producer?
a.a cyanobacterium
b.a diatom
c.a lichen
d.a chemosynthesizer
e.a caterpillar
6.Ecosystem Energetics–Trophic Levels; p. 31-4; moderate; ans: d
______are primary consumers.
a.Ferns
b.Phytoplankton
c.Lions and tigers
d.Cows and sheep
e.Chemosynthesizers
7.Ecosystem Energetics–Trophic Levels; p. 31-4; moderate; ans: c
A secondary consumer occupies the ______trophic level.
a.first
b.second
c.third
d.fourth
e.fifth
8.Ecosystem Energetics–Trophic Levels; p. 31-4; easy; ans: a
In general, ______percent of the incident light is incorporated into plant biomass.
a.less than 1
b.5 to 8
c.10 to 20
d.25 to 30
e.35 to 40
9.Ecosystem Energetics–Trophic Levels; p. 31-4; easy; ans: b
In general, approximately _____ percent of the energy in one trophic level can be assimilated into the next.
a.1
b.10
c.20
d.50
e.80
10.Ecosystem Energetics–Trophic Levels; p. 31-5; difficult; ans: d
A fungus is both a(n) ______and a ______.
a.heterotroph; primary producer
b.autotroph; primary consumer
c.heterotroph; secondary consumer
d.heterotroph; decomposer
e.autotroph; decomposer
11.Ecosystem Energetics–Trophic Levels; p. 31-6; easy; ans: c
In an ecosystem, energy flows from:
a.consumers to autotrophs to decomposers.
b.decomposers to consumers to autotrophs.
c.autotrophs to consumers to decomposers.
d.consumers to decomposers to autotrophs.
e.autotrophs to decomposers to consumers.
12.Ecosystem Energetics–Trophic Levels; p. 31-6; moderate; ans: a
______would be found at the base of a pyramid of energy.
a.Oak trees
b.Elephants
c.Mushrooms
d.Birds
e.Fish
13.Ecosystem Energetics–Trophic Levels; p. 31-6 and Fig. 31-3; difficult; ans: c
Which of the following statements about an upright pyramid of energy is FALSE?
a.It represents the energy relationships among trophic levels.
b.The total energy of producers is represented at the base of the pyramid.
c.The total energy of consumers is greater than the total energy of producers.
d.The total energy of primary carnivores is greater than the total energy of secondary carnivores.
e.The total energy decreases at successively higher trophic levels.
14.Ecosystem Energetics–Trophic Levels; p. 31-6; easy; ans: c
The existence of more grass plants than herbivores in a grassland ecosystem is illustrated by a(n):
a.pyramid of energy.
b.pyramid of biomass.
c.pyramid of numbers.
d.pyramid of body size.
e.inverted pyramid of biomass.
15.Ecosystem Energetics–Trophic Levels; p. 31-7; easy; ans: c
______is a fuel formed from wetland biomass that accumulates under standing water.
a.Lignite
b.Natural gas
c.Peat
d.Coal
e.Oil
16.Ecosystem Energetics–Trophic Levels; p. 31-8; easy; ans: e
Which of the following statements about parasites is FALSE?
a.They live on or in another organism.
b.They are always one trophic level above their hosts.
c.An example is a virus.
d.An example is a pathogenic bacterium.
e.They can be autotrophs or heterotrophs.
17.Nutrient and Material Cycling; p. 31-9; difficult; ans: d
Which of the following statements about nutrient cycling is FALSE?
a.An ecosystem has the property of regulating the cycling of nutrients.
b.An ecosystem is self-sustaining in terms of its nutrient supply.
c.Nutrients are continuously cycled between organisms and the environment.
d.In an ideal nutrient cycle, small amounts of nutrients are lost.
e.In a nutrient cycle, the rate of flow differs among nutrients and habitats.
18.Nutrient and Material Cycling; p. 31-10; difficult; ans: d
In the undisturbed Hubbard Brook forest, scientists detected:
a.considerable loss of nutrients by leaching.
b.considerable addition of nutrients from dissolving bedrock.
c.considerable inefficiency in conserving minerals.
d.a slight annual gain of nitrogen and potassium.
e.a slight annual gain of calcium.
19.Nutrient and Material Cycling; p. 31-10; difficult; ans: c
After all plants in a selected portion of the Hubbard Brook forest were killed, scientists detected a(n):
a.decrease in net calcium loss.
b.decrease in net potassium loss.
c.increase in net nitrogen loss.
d.increase in the amount of nitrate in the soil.
e.increase in the amount of potassium in the soil.
20.Interactions between Organisms–Beyond Trophic Relationships; p. 31-10; easy; ans: c
Competition occurs, by definition, when two individuals living in the same area:
a.belong to the same species.
b.belong to the same population.
c.require the same limiting resource.
d.photosynthesize at the same rates.
e.allocate energy in the same way.
21. Interactions between Organisms–Beyond Trophic Relationships; pp. 31-10–31-11; easy; ans: e
An example of interference competition is:
a.bears competing for food.
b.earthworms competing for oxygen.
c.plants competing for water.
d.plants competing for minerals.
e.birds competing for territory.
22.Interactions between Organisms–Beyond Trophic Relationships; p. 31-11; moderate; ans: d
Which of the following statements about the role of growth rate in competition is FALSE?
a.Plants with a high growth rate often have an advantage over plants with a low growth rate.
b.Plants with a low growth rate may survive if they are able to photosynthesize at low light intensities.
c.Leaf arrangement, crown shape, and patterns of allocation of energy all affect growth rate.
d.A single combination of traits usually produces a competitor that is best in all environments.
e.Within a single community, different species may coexist because of adaptations to different microenvironments.
23.Interactions between Organisms–Beyond Trophic Relationships; p. 31-11; moderate; ans: e
According to the principle of competitive exclusion, two species with similar requirements:
a.generally grow to the same height.
b.generally photosynthesize at the same rate.
c.cannot take up water equally well.
d.cannot photosynthesize equally well.
e.cannot coexist indefinitely in the same habitat.
24.Interactions between Organisms–Beyond Trophic Relationships; p. 31-11; moderate; ans: a
When the two species are grown together, Lemna polyrhiza is replaced by Lemna gibba because L. gibba outcompetes L. polyrhiza for:
a.light.
b.space.
c.carbon dioxide.
d.oxygen.
e.minerals.
25.Interactions between Organisms–Beyond Trophic Relationships; p. 31-12; moderate; ans: a
In the northern Rocky Mountains, seedlings of Engelmann spruce outcompete seedlings of subalpine fir in sunny locations because the spruce:
a.has a lower sensitivity to drought.
b.has a lower growth rate.
c.has a greater longevity.
d.grows to a greater size.
e.has more flexible growth requirements.
26.Interactions between Organisms–Beyond Trophic Relationships; p. 31-12; moderate; ans: d
In the chalk grasslands of England, what happened to the plants when a viral disease reduced the rabbit population?
a.All the plants died.
b.The average height increased.
c.The average height decreased.
d.Diversity decreased.
e.Diversity increased.
27.Interactions between Organisms–Beyond Trophic Relationships; p. 31-13; easy; ans: c
In nature, the penicillin produced by Penicillium chrysogenum growing on seeds:
a.inhibits seed germination.
b.inhibits the growth of the fungus.
c.inhibits the growth of bacteria.
d.stimulates seed germination.
e.stimulates the growth of bacteria.
28.Interactions between Organisms–Beyond Trophic Relationships; p. 31-13; moderate; ans: e
In allelopathy:
a.the alleles of a bacterium or fungus produce pathogenic effects in a plant.
b.some alleles of a plant are pathogenic to that same plant.
c.chemicals produced by a bacterium inhibit growth of a plant.
d.chemicals produced by a fungus inhibit growth of a plant.
e.chemicals produced by one plant inhibit growth of another plant.
29.Interactions between Organisms–Beyond Trophic Relationships; p. 31-13; easy; ans: b
Mutualism is an interaction between two species in which:
a.one species benefits and the other is harmed.
b.both species benefit.
c.both species are harmed.
d.one species benefits and the other is neither harmed nor helped.
e.one species is harmed and the other is neither harmed nor helped.
30.Interactions between Organisms–Beyond Trophic Relationships; p. 31-13; easy; ans: b
Which of the following statements about mycorrhizal associations is FALSE?
a.Mycorrhizal fungi grow in or on roots.
b.Mycorrhizal fungi can be species that simply grow near roots.
c.They are found in most vascular plants.
d.They are mutualistic associations.
e.They can be highly specific.
31.Interactions between Organisms–Beyond Trophic Relationships; p. 31-14; moderate; ans: e
The ants of genus Pseudomyrmex that swarm over a bull’s-horn acacia tree:
a.harm the plant.
b.provide the plant with sugar.
c.provide the plant with protein.
d.store the plant’s seeds.
e.protect the plant against predators.
32.Interactions between Organisms–Beyond Trophic Relationships; p. 31-14; moderate; ans: a
When ants of the genus Pseudomyrmex were removed from bull’s-horn acacia trees, the trees:
a.usually died.
b.were unaffected.
c.grew taller.
d.lived longer.
e.produced thorns.
33.Interactions between Organisms–Beyond Trophic Relationships; p. 31-15; moderate; ans: d
______produced by plants are the most important factors preventing attack by herbivorous insects.
a.Thorns
b.Spines
c.Waxy cuticles
d.Secondary metabolites
e.Leathery leaves
34.Interactions between Organisms–Beyond Trophic Relationships; p. 31-15; difficult; ans: b
What are tannins?
a.Sex attractants in insects
b.Compounds that make plant proteins indigestible to insects
c.Compounds produced by a plant when it is attacked
d.Fungal substances that detoxify pisatin
e.Elicitors produced by bacteria and fungi
35.Interactions between Organisms–Beyond Trophic Relationships; p. 31-15; difficult; ans: e
Strains of the Fusarium fungus produce ______that counter the production of ______by pea plants.
a.chromenes; helenanin
b.pisatin; chromenes
c.tannins; thorns
d.pyrethrum; waxy leaves
e.monooxygenases; pisatin
36.Interactions between Organisms–Beyond Trophic Relationships; p. 31-15; moderate; ans: c
After the cactus moth was introduced in Australia, what was the effect on the prickly-pear cactus?
a.The cacti were able to flower.
b.The cacti produced toxic chemicals.
c.The cactus population was vastly reduced.
d.The cactus population was completely wiped out.
e.The cacti were more widely available to grazing animals.
37.Development and Change of Communities and Ecosystems; p. 31-17; moderate; ans: a
After a glacier recedes, _____ are often the first to become established on the bare rock.
a.lichens and mosses
b.lichens and ferns
c.mosses and ferns
d.mosses and grasses
e.grasses and lichens
38.Development and Change of Communities and Ecosystems; p. 31-18; moderate; ans: c
An example of secondary succession is:
a.lichens colonizing bare rock.
b.mosses colonizing lava after a volcanic eruption.
c.shrubs colonizing a weedy field.
d.trees colonizing a grassy meadow.
e.grasses colonizing a moss-covered rock.
39.Development and Change of Communities and Ecosystems; p. 31-21; easy; ans: d
The transition from sugar pine to white fir forests in California was caused mainly by:
a.volcanic eruptions.
b.frequent earthquakes.
c.logging.
d.reduced numbers of forest fires.
e.reduced numbers of settlers.
40.Development and Change of Communities and Ecosystems; p. 31-21; easy; ans: e
The seeds of a serotinous cone are released by:
a.wind.
b.birds.
c.insects.
d.water.
e.fire.
41.Development and Change of Communities and Ecosystems; p. 31-22; moderate; ans: b
Nonprairie species are prevented by ______from encroaching on prairie ecosystems.
a.wind
b.fire
c.rainfall
d.herbivores
e.low temperature
True-False Questions
1.Introduction; p. 31-3; difficult; ans: T
An example of a community is an oak tree and all the organisms that live in and on it.
2.Ecosystem Energetics–Trophic Levels; p. 31-3; moderate; ans: F
Energy is recycled in an ecosystem.
3.Ecosystem Energetics–Trophic Levels; p. 31-3; easy; ans: T
All chemosynthesizers are microbial.
4.Ecosystem Energetics–Trophic Levels; p. 31-3; moderate; ans: F
All autotrophs obtain their energy from the sun.
5.Ecosystem Energetics–Trophic Levels; p. 31-3; difficult; ans: F
All plants are autotrophs.
6.Ecosystem Energetics–Trophic Levels; p. 31-4; easy; ans: T
An herbivore is a primary consumer; a carnivore is a secondary consumer.
7.Ecosystem Energetics–Trophic Levels; p. 31-4; easy; ans: F
Ecosystems usually have eight or nine trophic levels.
8.Ecosystem Energetics–Trophic Levels; p. 31-5; easy; ans: T
Detritivores obtain their food from dead and discarded organic matter.
9.Ecosystem Energetics–Trophic Levels; p. 31-6; easy; ans: F
Herbivores usually occupy the base of a pyramid of energy.
10.Ecosystem Energetics–Trophic Levels; p. 31-6; difficult; ans: T
An aquatic ecosystem is more likely to have an inverted pyramid of biomass than a terrestrial ecosystem.
11.Ecosystem Energetics–Trophic Levels; p. 31-7; moderate; ans: F
An example of biological energy conversion is burning coal for fuel.
12.Ecosystem Energetics–Trophic Levels; p. 31-8; easy; ans: T
Many species are members of more than one trophic level.
13.Ecosystem Energetics–Trophic Levels; p. 31-8; moderate; ans: T
An example of a parasitoid is a wasp.
14.Interactions between Organisms–Beyond Trophic Relationships; p. 31-10; easy; ans: T
Competition results when individuals living in the same area require the same limiting resource.
15.Interactions between Organisms–Beyond Trophic Relationships; p. 31-13; easy; ans: T
An example of allelopathy is the inability of weeds to grow near sorghum plants.
16.Interactions between Organisms–Beyond Trophic Relationships; p. 31-13; easy; ans: T
An example of mutualism is nitrogen-fixing bacteria growing in the root nodules of legumes.
17.Interactions between Organisms–Beyond Trophic Relationships; p. 31-13; easy; ans: F
Only a small percentage of vascular plants have mycorrhizal associations.
18.Interactions between Organisms–Beyond Trophic Relationships; p. 31-14; moderate; ans: T
In the bull’s-horn acacia, Beltian bodies provide food for ants of the genus Pseudomyrmex.
19.Interactions between Organisms–Beyond Trophic Relationships; p. 31-15; easy; ans: T
Secondary metabolites are chemicals produced by plants that deter insect herbivores.
20.Interactions between Organisms–Beyond Trophic Relationships; p. 31-15; moderate; ans: T
In response to Gypsy moth attack, defoliated oak trees produce new leaves with higher tannin levels than normal.
21.Interactions between Organisms–Beyond Trophic Relationships; p. 31-16; easy; ans: T
According to the cooperative model for an ecosystem, herbivores do not do irreparable harm to plants.
22.Development and Change of Communities and Ecosystems; p. 31-17; easy; ans: F
Higher plants are usually the first to become established on bare rock.
23.Development and Change of Communities and Ecosystems; p. 31-17; easy; ans: T
The Gaia hypothesis suggests that the biosphere functions as an organismal system.
24.Development and Change of Communities and Ecosystems; p. 31-20; easy; ans: F
A windstorm can cause a “gap” but a prairie dog cannot.
25.Development and Change of Communities and Ecosystems; p. 31-21; easy; ans: F
Efforts to prevent forest fires in California resulted in enhanced growth of sugar pines.
26.Development and Change of Communities and Ecosystems; p. 31-22; easy; ans: T
“Restoration” ecology refers to efforts by humans to reestablish natural communities.
Essay Questions
1.Ecosystem Energetics–Trophic Levels; pp. 31-3—31-4; easy
Name the trophic levels present in most ecosystems and describe the types of organisms present at each level. How do primary producers relate to these trophic levels?
2.Ecosystem Energetics–Trophic Levels; p. 31-4; moderate
Explain why a) there are so few links in a food chain and b) the largest land animals are herbivores.
3.Ecosystem Energetics–Trophic Levels; p. 31-6; difficult
Explain what is meant by pyramids of energy, biomass, and numbers. Under what circumstances are these pyramids upright and under what circumstances are they inverted?
4.Ecosystem Energetics–Trophic Levels; p. 31-7; moderate
Discuss the efforts by humans to develop renewable sources of energy from plants.
5.Nutrient and Material Cycling; pp. 31-9—31-10; moderate
Explain how the experiments at Hubbard Brook forest provided information about the retention of nutrients in ecosystems.
6.Interactions between Organisms–Beyond Trophic Relationships; p. 31-11; moderate
Use the experimental data from studies of Lemna species to explain the principle of competitive exclusion.
7.Interactions between Organisms–Beyond Trophic Relationships; p. 31-14; moderate
Describe the interactions between ants and acacia trees. What evidence supports the hypothesis that this is an example of mutualism?
8.Interactions between Organisms–Beyond Trophic Relationships; pp. 31-16–31-17; moderate
Explain the difference between the cooperative and competitive models used to view ecosystems.
9.Development and Change of Communities and Ecosystems; pp. 31-17; moderate
In what sense is the term “climax community” a misnomer?
10.Development and Change of Communities and Ecosystems; pp. 31-17–31-19; moderate
How does secondary succession differ from primary succession? Give three examples of secondary succession from your own experience.
11.Development and Change of Communities and Ecosystems; pp. 31-18–31-19; moderate
Discuss the speed and stages of succession following a volcanic eruption, using Krakatau or Mount St. Helens as an example.
12.Development and Change of Communities and Ecosystems; pp. 31-20–31-21; moderate
Discuss the roles of gaps in succession and the maintenance of species diversity.
13.Development and Change of Communities and Ecosystems; pp. 31-21–31-22; moderate
Are forest fires always detrimental to ecosystems? Give reasons to support your answer.
14.Development and Change of Communities and Ecosystems; p. 31-22; moderate
Describe the attempts to restore prairie communities by restoration ecologists.