CHAPTER 5—BIODIVERSITY, SPECIES INTERACTIONS, AND POPULATION
CONTROL
MULTIPLE CHOICE
1. What was the primary reason the southern sea otter nearly went extinct by the early 1900s?
a. They scared the tourists.
b. They have thick, luxurious fur.
c. They were ruining the kelp beds.
d. They were eating all the shellfish.
e. They raided valuable bird nests.
ANS: B
PTS: 1
TOP: 5-0 Core Case Study: The Southern Sea Otter: A Species in Recovery
KEY: Bloom's: Remember
2. The primary reason why southern sea otter recovery is important is because they ____.
a. are educational
b. are a keystone species
c. encourage tourism
d. eliminate common pests
e. have luxurious, thick fur
ANS: B
PTS: 1
TOP: 5-0 Core Case Study: The Southern Sea Otter: A Species in Recovery
KEY: Bloom's: Remember
3. Species can, over a long period of time, develop adaptations that allow them to reduce or avoid
competition by sharing resources. This is called ____.
a. competitive exclusion principle
b. resource partitioning
c. population distribution
d. interspecific competition
e. mimicry
ANS: B
PTS: 1
KEY: Bloom's: Understand
TOP: 5-1 How Do Species Interact?
4. Some prey species discourage predators with chemicals that are poisonous, irritating, foul smelling, or
bad tasting. What is this called?
a. chemotoxicity
b. biological warfare
c. chemical warfare
d. behavioral warfare
e. behavioral strategies
ANS: C
PTS: 1
KEY: Bloom's: Understand
TOP: 5-1 How Do Species Interact?
NOT: New
5. When populations of two different species interact over long periods of time, changes in the gene pool of
one species can lead to changes in the gene pool of the other. What is this called?
a. competition
b.
c.
d.
e.
coevolution
coincidence
commensalism
predation
ANS: B
PTS: 1
KEY: Bloom's: Remember
TOP: 5-1 How Do Species Interact?
6. Bats prey on certain species of moths by using high frequency echolocation to locate their prey. Certain
moths have evolved ears that can hear these frequencies allowing them to escape. This is an example of
____.
a. mimicry
b. coevolution
c. a behavioral strategy
d. commensalism
e. mutualism
ANS: B
PTS: 1
KEY: Bloom's: Apply
TOP: 5-1 How Do Species Interact?
NOT: New
7. What is said to occur when one organism feeds on another organism by living on or in the other
organism?
a. interspecific competition
b. predation
c. parasitism
d. mutualism
e. commensalism
ANS: C
PTS: 1
KEY: Bloom's: Remember
OP: 5-1 How Do Species Interact?
8. Parasites ____.
a. rarely kill their hosts
b. are usually larger than their hosts
c. must be internal to their hosts
d. may strengthen their hosts over a long period of time
e. are usually microscopic
ANS: A
PTS: 1
KEY: Bloom's: Understand
TOP: 5-1 How Do Species Interact?
9. From the ____ point of view, parasites are harmful, but from the ____ perspective, parasites can promote
diversity.
a. population’s; host’s
b. host’s; population’s
c. predator’s; prey’s
d. prey’s; predator’s
e. community’s; individual’s
ANS: B
PTS: 1
KEY: Bloom's: Apply
TOP: 5-1 How Do Species Interact?
NOT: New
10. When two species behave in ways that benefit both by providing each with food, shelter, or some other
resource, it is called ____.
a.
b.
c.
d.
e.
mimicry
coevolution
parasitism
commensalism
mutualism
ANS: E
PTS: 1
KEY: Bloom's: Understand
TOP: 5-1 How Do Species Interact?
NOT: New
11. The relationship between clownfish and sea anemone is called ____.
a. interspecific competition
b. predation
c. parasitism
d. mutualism
e. commensalism
ANS: D
PTS: 1
KEY: Bloom's: Understand
TOP: 5-1 How Do Species Interact?
12. The relationship between bacteria that live in the digestive systems of animals, such as humans, is ____.
a. interspecific competition
b. predation
c. parasitism
d. mutualism
e. commensalism
ANS: D
PTS: 1
KEY: Bloom's: Understand
TOP: 5-1 How Do Species Interact?
NOT: New
13. What occurs when an interaction benefits one species but has little, if any, effect on the other?
a. interspecific competition
b. predation
c. parasitism
d. mutualism
e. commensalism
ANS: E
PTS: 1
KEY: Bloom's: Remember
TOP: 5-1 How Do Species Interact?
14. Plants such as bromeliads share a commensalism interaction with large trees in tropical and subtropical
forests by attaching to the trunks or branches of the trees. The bromeliads are an example of ____.
a. parasites
b. opportunistic parasites
c. epiphytes
d. prey
e. herbivores
ANS: C
PTS: 1
KEY: Bloom's: Apply
TOP: 5-1 How Do Species Interact?
NOT: Modified
15. Which of the following is not considered a form of nondestructive behavior?
a. reducing competition by foraging at different times
b. reducing competition by foraging in different places
c. orchids attached to branches of forest trees
d. using the energy or body of another organisms as a food source
e. bacteria breaking down food for a host and having a sheltered habitat
ANS: D
PTS: 1
KEY: Bloom's: Analyze
TOP: 5-1 How Do Species Interact?
16. What occurs when members of two or more species interact to gain access to the same limited resources?
a. interspecific competition
b. predation
c. parasitism
d. mutualism
e. commensalism
ANS: A
PTS: 1
KEY: Bloom's: Understand
TOP: 5-1 How Do Species Interact?
17. What is the most common interaction between species?
a. competition
b. predation
c. parasitism
d. mutualism
e. commensalism
ANS: A
PTS: 1
KEY: Bloom's: Remember
TOP: 5-1 How Do Species Interact?
18. If multiple species find themselves competing for the same resource, the competition can be reduced by
which of the following?
a. camouflage
b. cooperation
c. resource partitioning
d. resource expansion
e. mimicry
ANS: C
PTS: 1
KEY: Bloom's: Understand
TOP: 5-1 How Do Species Interact?
19. The non-poisonous ____ butterfly gains protection by looking like the bad -tasting ____ butterfly, which
is a protective device known as ____.
a. monarch; viceroy; camouflage
b. monarch; zebra swallowtail; camouflage
c. viceroy; zebra swallowtail; mimicry
d. viceroy; monarch; mimicry
e. viceroy; monarch; camouflage
ANS: D
PTS: 1
KEY: Bloom's:Evaluate
TOP: Figure 5-6 | 5-1 How Do Species Interact?
20. Kelp forests help reduce ____ by blunting the force of incoming waves and trapping some of the
outgoing sand.
a. runoff
b. shore erosion
c. coastal pollution
d. tidal waves
e. tidal pools
ANS: B
PTS: 1
KEY: Bloom's: Understand
TOP: Science Focus 5-1 Threats to Kelp Forests
NOT: New
21. Kelp forests are a very important ecosystem in marine waters by supporting important biodiversity.
These kelp forests are threatened by all of the following except _____.
a. water pollution containing herbicides
b. sea urchins
c. southern sea otters
d. global warming
e. water pollution containing fertilizers
ANS: C
PTS: 1
KEY: Bloom's: Analyze
TOP: Science Focus 5-1 Threats to Kelp Forests
22. What is a population’s distribution of individuals among various age groups called?
a. reproductive structure
b. genetic structure
c. age structure
d. reproductive composition
e. age composition
ANS: C
PTS: 1
KEY: Bloom's: Understand
TOP: 5-3 What Limits the Growth of Populations?
NOT: New
23. What describes an organism that is too old to reproduce?
a. prereproductive
b. reproductive
c. postreproductive
d. nonreproductive
e. elderly
ANS: C
PTS: 1
KEY: Bloom's: Understand
TOP: 5-3 What Limits the Growth of Populations?
NOT: New
24. Each population in an ecosystem has a ____ to variations in its physical and chemical environment.
a. low tolerance
b. high tolerance
c. range of tolerance
d. high resilience
e. low resilience
ANS: C
PTS: 1
KEY: Bloom's: Understand
TOP: 5-3 What Limits the Growth of Populations?
NOT: New
25. Too much or too little of any physical or chemical factor can prevent the growth of a population, even if
all other factors are at or near the optimum conditions. What is this ecological principle?
a. tolerance
b. limiting factor
c. resilience
d. persistence
e. optimal level
ANS: B
PTS: 1
TOP: 5-3 What Limits the Growth of Populations?
KEY: Bloom's: Understand
NOT: New
26. What is the number of individuals in a population found within a defined area or volume that can limit
the size of some populations?
a. population density
b. population control
c. the range of tolerance
d. the age structure
e. the optimum population level
ANS: A
PTS: 1
KEY: Bloom's: Understand
TOP: 5-3 What Limits the Growth of Populations?
NOT: New
27. Some species that tend to reproduce later in life and have a small number of offspring with long life
spans ____.
a. have high population growth rates
b. have high environmental resistance
c. have low environmental resistance
d. are unlikely to ever face extinction
e. are vulnerable to extinction
ANS: E
PTS: 1
KEY: Bloom's: Analyze
TOP: 5-3 What Limits the Growth of Populations?
NOT: New
28. There are ____ limits to population growth in nature.
a. never
b. sometimes
c. always
d. low
e. high
ANS: C
PTS: 1
KEY: Bloom's: Understand
TOP: 5-3 What Limits the Growth of Populations?
NOT: New
29. The maximum population of a given species that a particular habitat can sustain indefinitely is the
definition of ____.
a. logistic growth
b. environmental resistance
c. exponential growth
d. carrying capacity
e. biotic potential
ANS: D
PTS: 1
KEY: Bloom's: Remember
TOP: 5-3 What Limits the Growth of Populations?
NOT: Modified
30. When plotting the number of individuals in a population against time, the data yield a J-shaped curve.
What does this curve indicate?
a. logistic growth
b. environmental resistance
c. exponential growth
d. carrying capacity
e. biotic potential
ANS: C
PTS: 1
TOP: 5-3 What Limits the Growth of Populations?
KEY: Bloom's: Apply
31. Exponential growth followed by a steady decrease in population growth until the population size
stabilizes is typical of ____.
a. logistic growth
b. environmental resistance
c. exponential growth
d. carrying capacity
e. biotic potential
ANS: A
PTS: 1
KEY: Bloom's: Analyze
TOP: 5-3 What Limits the Growth of Populations?
NOT: Modified
32. By 1900, white-tailed deer populations in the U.S. were reduced to about ____, but now, since laws have
been passed to protect them and their natural predators have nearly been eliminated, their population is
over ____ in the U.S.
a. 500; 1 million
b. 5,000; 1 million
c. 50,000; 5 million
d. 50,000; 25 million
e. 100,000; 10 million
ANS: D
PTS: 1
KEY: Bloom's: Understand
TOP: 5-3 What Limits the Growth of Populations?
NOT: New
33. What would cause a population to overshoot its carrying capacity?
a. an increase in predators
b. a decrease in birth rates
c. an increase in emigration
d. a decrease in environmental pressures
e. a reproductive time lag between birth and death rates
ANS: E
PTS: 1
KEY: Bloom's: Understand
TOP: 5-3 What Limits the Growth of Populations?
34. A group of interbreeding individuals of the same species in the same geographic region is called a(n)
____.
a. community
b. population
c. ecosystem
d. biosphere
e. biome
ANS: B
PTS: 1
KEY: Bloom's: Remember
TOP: 5-3 What Limits the Growth of Populations?
35. What is the most common distribution of populations?
a. random
b. uniform
c. clumped
d. circles
e. none of these
ANS: C
PTS: 1
TOP: 5-3 What Limits the Growth of Populations?
KEY: Bloom's: Remember
36. A population increases through birth and ____.
a. assimilation
b. integration
c. socialization
d. emigration
e. immigration
ANS: E
PTS: 1
KEY: Bloom's: Understand
TOP: 5-3 What Limits the Growth of Populations?
NOT: New
37. Emigration is the ____.
a. arrival of individuals into an established population
b. arrival movement of individuals into an uninhabited area
c. departure movement of individuals from a population to another area
d. repeated movement into and out of an area
e. lack of immigration into an area
ANS: C
PTS: 1
KEY: Bloom's: Understand
TOP: 5-3 What Limits the Growth of Populations?
NOT: Modified
38. Kelp forests are composed of large concentrations of a(n) ____.
a. algae
b. phytoplankton
c. seaweed
d. trees
e. anemone
ANS: C
PTS: 1
KEY: Bloom's: Remember
TOP: Science Focus 5-1 Threats to Kelp Forests
NOT: New
39. Which of the following has caused the population of the southern sea otters to fluctuate?
a. decline in population of orcas
b. parasites from house cats
c. parasites from dolphins
d. high reproductive rates
e. extinction of algal species
ANS: B
PTS: 1
TOP: Science Focus 5-2 Why Do California's Sea Otters Face an Uncertain Future?
KEY: Bloom's: Analyze
NOT: Modified
40. What is succession that begins in an area where an ecosystem has been disturbed, removed, or destroyed,
and that contains soil or bottom sediment?
a. primary succession
b. secondary succession
c. ecological establishment
d. disturbance succession
e. facilitation
ANS: B
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Understand
NOT: New
41. Which of the following exhibits secondary ecological succession?
a. abandoned parking lot
b. newly cooled lava
c. newly constructed reservoir
d. a crumbled concrete building
e. recently flooded land
ANS: E
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Apply
42. The situation in which one set of species makes an area suitable for species with different niche
requirements and often, less suitable for itself, is called ____.
a. primary succession
b. secondary succession
c. facilitation
d. inhibition
e. tolerance
ANS: C
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Remember
NOT: New
43. Late successional plants are largely unaffected by plants at earlier stages of succession because they are
not in direct competition for resources, a factor called ____.
a. facilitation
b. imperturbability
c. inhibition
d. tolerance
e. intolerance
ANS: D
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Understand
NOT: Modified
44. Most ecologists now recognize that mature, late-successional ecosystems ____.
a. are in a state of continual disturbance and change
b. are in a stable state of equilibrium
c. are in natural balance with their environment
d. have followed an expected path to their stable state as a climax community
e. have inevitably progressed through succession and no longer face competition
ANS: A
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Understand
NOT: New
45. The capacity to withstand external stress and disturbance is called ____.
a. equilibrium
b. stability
c. balance of nature
d. facilitation
e. inhibition
ANS: B
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Understand
NOT: New
46. The ability of a living system to survive moderate disturbances is called ____.
a. stability
b. inertia
c. constancy
d. tipping point
e. resilience
ANS: B
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Remember
47. What refers to the ability of a living system to be restored after a period of moderate to severe
disturbance?
a. stability
b. inertia
c. constancy
d. tipping point
e. resilience
ANS: E
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Remember
48. If the resilience of a damaged ecosystem is low enough, the degraded area may not be restored by
secondary succession. When this happens, the damaged ecosystem has reached ____.
a. stability
b. inertia
c. constancy
d. a tipping point
e. resilience
ANS: D
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Understand
NOT: Modified
49. Grasslands have ____ and can burn easily.
a. low facilitation
b. high facilitation
c. low resilience
d. high inertia
e. low inertia
ANS: E
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Apply
NOT: New
50. Which of the following exhibits primary succession?
a. a rock exposed by a retreating glacier
b. an abandoned farm
c. a clear-cut forest
d. newly flooded land
e. a recently burned forest
ANS: A
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Apply
TRUE/FALSE
1. The southern sea otter is a tool-using mammal.
ANS: T
PTS: 1
TOP: Figure 5-1 | 5-0 Core Case Study: The Southern Sea Otter: A Species in Recovery
KEY: Bloom's: Understand
2. The most common interaction between species is commensalism.
ANS: F
PTS: 1
KEY: Bloom's: Understand
TOP: 5-1 How Do Species Interact?
3. Humans compete with many other species for space, food, and other resources.
ANS: T
PTS: 1
KEY: Bloom's: Remember
TOP: 5-1 How Do Species Interact?
4. Animal predators tend to kill the sick, weak, aged, and least fit members of a species because they are the
easiest to catch.
ANS: T
PTS: 1
KEY: Bloom's: Understand
TOP: 5-1 How Do Species Interact?
NOT: Modified
5. In predator-prey relationships, the predator is seeking food for itself and its offspring, while the prey is
seeking not to become food for the predator. As a result, predator and prey populations exert tremendous
natural selection pressures on each other.
ANS: T
PTS: 1
KEY: Bloom's: Apply
TOP: 5-1 How Do Species Interact?
6. At the population level, parasites are always harmful to the host species.
ANS: F
PTS: 1
KEY: Bloom's: Understand
TOP: 5-1 How Do Species Interact?
7. Organisms with clumped distributions are fairly rare.
ANS: F
PTS: 1
KEY: Bloom's: Understand
TOP: 5-3 What Limits the Growth of Populations?
8. Large mammals, such as elephants and rhinoceroses, are especially vulnerable to extinction because of
their reproductive patterns.
ANS: T
PTS: 1
TOP: 5-3 What Limits the Growth of Populations?
KEY: Bloom's: Understand
NOT: Modified
9. The growth rate of a population increases as its size nears the carrying capacity of its environment.
ANS: F
PTS: 1
KEY: Bloom's: Analyze
TOP: 5-3 What Limits the Growth of Populations?
NOT: Modified
10. The carrying capacity of any given area is not fixed.
ANS: T
PTS: 1
KEY: Bloom's: Understand
TOP: 5-3 What Limits the Growth of Populations?
11. Humans are exempt from population overshoot and dieback.
ANS: F
PTS: 1
KEY: Bloom's: Apply
TOP: 5-3 What Limits the Growth of Populations?
12. Primary and secondary ecological succession tend to increase biodiversity of communities and
ecosystems by increasing species richness and interactions among species.
ANS: T
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Understand
NOT: Modified
13. Scientists have changed their view about a stable type of climax community as the end product of
succession and are now suggesting we can not predict the course of succession.
ANS: T
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Analyze
14. Grasslands have a high resilience and therefore can recover quickly following a fire.
ANS: T
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Understand
NOT: Modified
15. In communities and ecosystems the types and numbers of species change in response to changing
environmental conditions.
ANS: T
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Understand
COMPLETION
1. The southern sea otter has been classified as a(n) ____________________ species because in their
absence, kelp forests would probably be destroyed.
ANS: keystone
PTS: 1
TOP: 5-0 Core Case Study: The Southern Sea Otter: A Species in Recovery
KEY: Bloom's: Understand
NOT: Modified
2. ____________________ is a competitive interaction between species for food, water, light and/or space.
ANS: Interspecific competition
PTS: 1
NOT: Modified
TOP: 5-1 How Do Species Interact?
KEY: Bloom's: Remember
3. When two or more species compete with one another their niches are said to ____________________.
ANS: overlap
PTS: 1
TOP: 5-1 How Do Species Interact?
KEY: Bloom's: Understand
4. ____________________ occurs when a member of one species feeds directly on all or part of a member
of another species.
ANS: Predation
PTS: 1
TOP: 5-1 How Do Species Interact?
KEY: Bloom's: Remember
5. Bad-tasting, bad-smelling, toxic, or stinging-prey species advertise their characteristics using
____________________.
ANS: warning coloration
PTS: 1
NOT: Modified
TOP: 5-1 How Do Species Interact?
KEY: Bloom's: Understand
6. Some prey species make themselves larger or mimic a predator, both of which are called
____________________.
ANS: behavioral strategies
PTS: 1
NOT: Modified
TOP: 5-1 How Do Species Interact?
KEY: Bloom's: Understand
7. When two different species interact over a long time, changes in the gene pool help both species to
become more competitive or avoid competition. This is called _______________,
ANS: coevolution
PTS: 1
TOP: 5-1 How Do Species Interact?
KEY: Bloom's: Remember
8. In _______________, two species behave in ways that benefit both by providing each with needed
resources.
ANS: mutualism
PTS: 1
TOP: 5-1 How Do Species Interact?
KEY: Bloom's: Remember
9. Vast armies of ____________________ inhabit the digestive tracts of animals, such as humans, and help
break down or digest their food.
ANS: bacteria
PTS: 1
TOP: 5-1 How Do Species Interact?
KEY: Bloom's: Remember
10. The gradual change in species composition in a given area is called ____________________.
ANS: ecological succession
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Remember
11. The most common form of population dispersion found in nature is ____________________.
ANS: clumps
PTS: 1
TOP: 5-3 What Limits the Growth of Populations?
KEY: Bloom's: Remember
12. ____________________ is the combination of all factors that act to limit the growth of a population.
ANS: Environmental resistance
PTS: 1
TOP: 5-3 What Limits the Growth of Populations?
KEY: Bloom's: Remember
13. A population exceeding its carrying capacity will suffer a(n) ____________________ or
____________________, unless the excess individuals can switch to new resources or move to a new
area.
ANS:
dieback; crash
crash; dieback
PTS: 1
TOP: 5-3 What Limits the Growth of Populations?
KEY: Bloom's: Apply
14. ____________________ involves the gradual establishment of biotic communities in lifeless areas
where there is no soil.
ANS: Primary succession
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Understand
15. One of the factors determining the rate of succession is _______________, in which one set of species
makes an area suitable for other species with different requirements.
ANS: facilitation
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Understand
SHORT ANSWER
1. Describe what happens when species partition resources.
ANS:
Resource partitioning occurs when species competing for similar scarce resources evolve specialized
traits that allow them to share resources by using parts of them, using them at different times, or using
them in different ways.
PTS: 1
NOT: New
TOP: 5-1 How Do Species Interact?
KEY: Bloom's: Understand
2. What method of hunting prey do Arctic foxes use?
ANS:
Arctic foxes use camouflage by blending into their snowy background to avoid detection, and then they
ambush their prey.
PTS: 1
TOP: Figure 5-5 | 5-1 How Do Species Interact?
KEY: Bloom's: Apply
NOT: New
Use the figure above to answer the following question(s).
3. Determine which portion of the accompanying graph represents the number of reindeer that can be
sustained indefinitely in a given area. What term illustrates this?
ANS:
Letter A represents the carrying capacity.
PTS: 1
TOP: 5-3 What Limits the Growth of Populations?
KEY: Bloom's: Analyze
NOT: New
4. What does it mean when a population uses up their resource supplies and temporarily overshoots?
Which letter on this graph represents when this has occurred to a certain reindeer population?
ANS:
The population exceeds the carrying capacity of their environment. It is represented by letter B.
PTS: 1
TOP: 5-3 What Limits the Growth of Populations?
KEY: Bloom's: Analyze
NOT: New
5. What happens to a population if a dieback occurs, and which portion of the graph represents this?
ANS:
A population suffers a sharp decline, also called a population crash. It is represented by letter C.
PTS: 1
TOP: 5-3 What Limits the Growth of Populations?
KEY: Bloom's: Analyze
NOT: New
ESSAY
1. Explain why it is important to care about the survival of the endangered southern sea otters of California.
ANS:
One reason is for ethical reasons, as many people believe it is wrong to allow human activities to cause
the extinction of a species. Another reason is that people love to watch this lovable and intelligent
animals as they play in water, which results in millions of dollars a year in tourism revenues. Finally,
biologists classify southern sea otters as keystone species, which means that in their absence sea urchins
and other kelp-eating species on which sea otters feed would probably destroy the Pacific coast kelp
forests and much of the biodiversity they support.
PTS: 1
TOP: 5-0 Core Case Study: The Southern Sea Otter: A Species in Recovery
KEY: Bloom's: Analyze
NOT: New
2. Using a small rodent, such as a field mouse, and a predator, such as a snake, explain how coevolution
works.
ANS:
The rodent responds to the environmental pressure applied by the snake through changes in behavior,
anatomy, or physiology to reduce the predation. The snake, facing reducing predatory success, changes
in response to the rodent. The rodent again responds to the specifics of the environmental pressure. This
step-by-step adaptation is known as coevolution.
PTS: 1
TOP: 5-1 How Do Species Interact?
KEY: Bloom's: Apply
3. At the present time the global human population surpasses seven billion people. If we exceed the
carrying capacity of the earth, the human population may suffer a substantial collapse.
Consider the following formula for population change:
population change = (births + immigration)  (deaths + emigration)
What will be required of humans in order to stabilize or reduce our population?
ANS:
Speaking on a global scale, there is no place for us to come from (immigration) or go to (emigration).
That means population change is limited to births minus deaths. To put it in the crudest of terms, we
must either reduce the number of births or increase the number of deaths in order to stabilize or reduce
our population. If we choose not to undertake that change, nature will do so as we exceed our carrying
capacity.
PTS: 1
TOP: 5-3 What Limits the Growth of Populations?
KEY: Bloom's: Analyze
NOT: Modified
4. Some people blame white-tailed deer for invading suburban yards and gardens. Discuss potential
solutions to this problem.
ANS:
There are no easy answers to the deer population problem in the suburbs. Changes in hunting
regulations that allow for the killing of more female deer have cut down the overall deer population.
However, since widespread hunting is not allowed in suburban areas, some areas have hired experienced
archers to help reduce deer numbers safely. Some communities spray the scent of deer predators or
rotting deer meat on the edges of suburban areas to scare off deer. Others have used equipment that
emits high frequency sounds, which are undetectable to humans. Some people surround their yards
with high fences over which the deer can not jump. In addition to these deterrents, deer can be trapped
and moved, but this is expensive and must be repeated whenever the deer return. People could try birth
control for deer to keep their numbers down or they could try trapping dominant males and sterilizing
them.
PTS: 1
TOP: 5-3 What Limits the Growth of Populations?
KEY: Bloom's: Analyze
NOT: New
5. Describe the three factors ecologists have identified that affect how and at what rate succession occurs.
ANS:
The first factor that affects how and at what rate succession occurs is facilitation. This is when one set
of species makes an area suitable for species with different niche requirements, and often less suitable
for itself. For example, lichens and mosses gradually build up soil on rocks in primary succession,
which allows grasses and other plants to move in and crowd out the lichens and mosses. The second
factor is inhibition, in which some species hinder the establishment and growth of other species. For
example, needles dropping off some pine trees make the soil beneath the trees too acidic for most other
plants to grow there. The third factor is tolerance, whereby plants in the late stages of succession
succeed because they are not in direct competition with other plants for key resources. For example,
shade-tolerant species can live in shady forests because they do not need as much sunlight as the trees
above them do.
PTS: 1
TOP: 5-2 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
KEY: Bloom's: Analyze
NOT: New