1.	When a biologist studies the way organisms interact with each other and with their
environment, she is studying their
	a.	Physiology
	b.	Anatomy
	c.	Morphology
	d.	Genetics
	e.	Ecology

2.	In a deciduous oak forest of the American northeast, one example of an abiotic
component of the ecosystem would be
	a.	nematodes in the soil that feed on plant roots
	b.	nematodes in the soil that feed on dead organic matter
	c.	sunlight that filters through the canopy
	d.	animals such as deer that migrate through the forest but do not eat in the
	e.	the understory plant community

3.	An aquatic biologist is studying a lake in western Massachusetts in order to
document the N cycle of the lake, and thus she is measuring inputs, turnover, and outputs
of N. A second ecologist is studying a larger region of western Massachusetts that is
forested, with several lakes, and is studying N transfers between the forest and the lakes.
The first ecologist claims that her lake is an ecosystem; the second ecologist also claims
that her forested region, with its many lakes, is an ecosystem. Which ecologist is correct,
or are they both wrong or right?

4.	Bacteria growing in a petri dish may grow rapidly and experience exponential
growth. However, bacteria in the soil, measured as the number of organisms per gram of
soil, usually do not increase in population size from one year to the next. Yet no new food
is added to the petri dish after the initial addition of the bacterial innoculum, but new
food sources are always added to the soil by way of plant detritus. How can this be true?

5.	Although models of population structure in an ecosystem usually assume that
populations reach a carrying capacity after time, in fact, population size may fluctuate
around a mean from year to year. Using a population of mice in a grassland, give (1) an
example of a density-independent factor that could cause population size to increase; (2)
an example of a density-independent factor that could cause population size to decrease;
(3) an example of a density-dependent factor that could cause population size to increase;
(4) an example of a density-dependent factor that could cause population size to decrease.

6.	A complex interrelated network of organisms and the surrounding abiotic environment
in a defined area is a(n):
	a.	Community
	b.	Ecosystem
	c.	Population
	d.	Biosphere
	e.	Biome

7.	All organisms that reside within an ecosystem and that can potentially interbreed
are members of a(n)
	a.	population
	b.	community
	c.	trophic level
	d.	aggregation
	e.	ecotope

8.	The organisms that represent the different species within an ecosystem that
interact in various ways comprise the
	a.	population
	b.	community
	c.	trophic level
	d.	aggregation
	e.	ecotope

9.	Environmental resistance may limit the size of populations by
	a.	increasing both birth and death rates
	b.	decreasing both birth and death rates
	c.	increasing death rates and/or decreasing birth rates
	d.	decreasing death rates and/or increasing birth rates
	e.	changing the biotic potential

10.	To determine the number of individuals that will be added to a population in a
specified time we multiply the growth rate (r) by the ________.
	a.	biotic potential
	b.	original population size
	c.	environmental resistance
	d.	final population size
	e.	number of immigrants
11.	If a population of 100 birds increases to 120 birds the following year, r =
	a.	0.16
	b.	0.20
	c.	1.2
	d.	2
	e.	20

12.	Which factor would not influence the size a population reaches over time?
	a.	Number of individuals migrating
	b.	Number of deaths
	c.	Age of females at reproduction
	d.	Distance travelled by migrants
	e.	Number of births

13.	Environmental resistance
	a.	is limits imposed on population growth by the biotic environment
(predators, competitors)
	b.	is limits imposed on population growth by the abiotic environment
	c.	is limits imposed on population growth by both the biotic and abiotic
	d.	is a factor that decreases both death rates and birth rates
	e.	is a factor that increases both death rates and birth rates

14.	The biotic potential of a population
	a.	directly affects environmental resistance
	b.	causes changes in birth rates without affecting death rates
	c.	causes changes in death rates without affecting birth rates
	d.	is the maximum rate at which a population may increase
	e.	both a and c

15.	There are 150 spotted owls in an old-growth forest patch in western Oregon. A
biologist tracking the birds saw that in one year, 25 new birds were hatched, and 5 died.
Thus r = 
	a.	170
	b.	145
	c.	2
	d.	6
	e.	20
16.	Exponential growth occurs when
	a.	there is a constant number of births each year and b > d
	b.	the population grows by a fixed percentage each year
	c.	immigration is greater than emigration
	d.	the biotic potential increases each year
	e.	environmental resistance declines each year

17.	Populations which have been relatively undisturbed by man normally grow unlimited
by their environment.

18.	According to the equation for population growth rate, of two populations with equal
death rates the population with r = 2 will increase more rapidly than a population with r =

19.	A measure of the ability of a population to grow under ideal circumstances is its
_______________ _________________.

20.	The sum of all factors that limit the ability of a population to grow are known as
________________ ________________.

21.	In the equation "population growth = rN," the letter r stands for

22.	Many species of field mice are able to reproduce several times a year, and produce
litters with multiple offspring. However, an ecologist noted that the population size of
mice, as measured in a California grassland, did not change from year to year. The factors
that keep natural populations from increasing are collectively called the __________.

23.	How is a population growth rate expressed?

24.	Write an equation which describes a situation in which a population remains stable.

25.	Explain what happens in exponential population growth.

26.	In the United States today there is a trend toward women having their first child
in their late 30's or early 40's. By contrast, a few years ago most women started having
children in their early 20's. What effect would you expect this change to have on
population growth in the USA?  Would it have any effect if the number of children per woman
is the same?  Explain.

27.	Why would a bacterial population living in an unrestricted environment grow much
faster than an eagle population?

28.	When a population has inhabited an area for a long time and the population size has
stabilized because of resource limitations:
	a.	Carrying capacity has been reached
	b.	Density dependence occurs
	c.	Predation decreases
	d.	Density independence occurs
	e.	Environmental resistance declines

29.	An insect population grows exponentially until an early winter freeze kills almost
all of the insects. The next spring the population grows exponentially again. This type of
population growth is known as
	a.	Boom and bust
	b.	Sigmoidal
	c.	Density-dependent
	d.	Density-independent
	e.	Sustained

30.	The human population is currently following a J-shaped curve. This means that the
population is growing
	a.	Arithmetically
	b.	Sigmoidally
	c.	At a decreasing rate
	d.	By a boom and bust cycle
	e.	Exponentially

31.	An important density-independent factor limiting population size is __________.
	a.	Predation
	b.	Weather
	c.	Environmental resistance
	d.	Competition
	e.	Food quantity

32.	Which of these is not a density-dependent control of population size?
	a.	Parasitism
	b.	Predation
	c.	Competition
	d.	Biotic potential
	e.	Shortage of food

33.	Density-dependent factors such as predation have _________________ effect on
population size.
	a.	a long-term
	b.	a short-term
	c.	a negative feedback
	d.	a positive feedback
	e.	no

34.	If a caterpillar eats a seedling in your garden, the caterpillar is acting as a
	a.	Predator
	b.	Parasite
	c.	Competitor
	d.	Density-independent factor
	e.	Saprophyte

35.	Predators and parasites are always harmful to their prey or host populations.
	a.	True.
	b.	False, because predators always harm the prey population, but parasites
often do little or no harm.
	c.	False, because parasites always harm their host populations but predators
may be helpful.
	d.	False, because parasites and predators kill their hosts and prey.
	e.	False, because predators and parasites often help the host or prey
population by attacking the weak.

36.	In a maple forest in the spring the ground will often be covered with young maple
seedlings which compete for light and nutrients. By fall, most of these have died, leaving
only a few survivors. This is an example of ____________ competition.
	a.	scramble
	b.	contest
	c.	dominance hierarchy
	d.	interspecific
	e.	social stress

37.	Most parasites have evolved to _________ their host.
	a.	kill
	b.	only weaken
	c.	have no effect on
	d.	control
	e.	all of these
38.	What type of competition has occurred when one organism uses social or chemical
interactions to limit the access of other individuals to resources?
	a.	Contest competition
	b.	Scramble competition
	c.	Interspecific
	d.	Intramural
	e.	Social

39.	A caribou dies because it was weakened by parasites (like tapeworms) passed from
one individual to the next under crowded conditions during an unusually long, cold winter.
What killed the caribou?
	a.	Density-independent factors
	b.	Density-dependent factors
	c.	Abiotic factors
	d.	Biotic factors
	e.	Both density-dependent and density-independent factors

40.	Some predators feed preferentially on the most abundant prey. This type of
predation is:
	a.	Density dependent
	b.	Density independent
	c.	Competitive
	d.	Exponential
	e.	Cyclical

41.	Why do many non-native species, such as a prickly pear cactus brought to Australia
from South America, rapidly become abundant when first introduced?
	a.	The climate in the new site is more favorable than it's native site
	b.	Non-native species increase their reproductive rate when introduced
	c.	There are fewer predators and parasites capable of attacking the non-native
species in the new site
	d.	The carrying capacity at the new site is higher than at the native site
	e.	Growth changes from an S-curve to a J-curve at the new site

42.	An ecosystem's carrying capacity for a population is determined by all of the
following factors except:
	a.	Space
	b.	Energy
	c.	Water
	d.	Food
	e.	Competition
43.	The carrying capacity of an ecosystem is determined by
	a.	the number of ecotones in the ecosystem
	b.	the availability of resources in the environment
	c.	demand for space
	d.	demand for space, water and light
	e.	the intersection between environmental resistance and biotic potential

44.	Parasites affect population sizes of their hosts
	a.	in a density dependent fashion, and usually directly kill the hosts
	b.	in a density dependent fashion, and do not usually directly kill the hosts
	c.	in a density independent fashion, and usually directly kill the hosts
	d.	in a density independent fashion, and do not usually directly kill the
	e.	in a density dependent fashion, and do not affect host death rates

45.	During the winter of 1999, minimum temperatures did not get much below freezing in
an Oregon pond, and the following summer large mosquito populations were observed. In the
winter of 2000, frost came early, and most ponds froze for 3 months. In the following
summer, very low mosquito populations were observed. This is an example of
	a.	density independent regulation
	b.	density dependent regulation
	c.	ecosystem carrying capacity
	d.	community carrying capacity
	e.	exotic regulation

46.	When mosquitoes are very abundant, purple martins flock to the area and specialize
on them. When mosquito populations are not large, purple martins are similarly scarce and
feed on other insects. This is an example of
	a.	density independent regulation
	b.	density dependent regulation
	c.	ecosystem carrying capacity
	d.	community carrying capacity
	e.	exotic regulation
47.	Juglans nigra, or the black walnut, releases an allelopathic (toxic to other
plants) compound when its leaves decompose; the result is that few plants can live under
the canopy of the tree. Thus the black walnut can be said to engage in
	a.	parasitism
	b.	scramble competition
	c.	sociopathic competition
	d.	allele-dependent competition
	e.	contest competition

48.	Prey, such as lemmings, may have a density-dependent effect on predator
populations, such as those of the snowy owl, by enabling the predator to increase the
number of predator offspring at high prey densities.

49.	When predators and prey both have population cycles, the predator cycle will tend
to _______________ the prey cycle.

50.	Predation is considered to be a density __________ factor that controls the
population size of prey.

51.	Competition among individual members of the same species is referred to as
__________ competition.

Match these with the types of effects they might have on a lemming population:
a. Density-dependent
b. Density-independent

52.	In a population of lemmings which followed a boom and bust cycle, a sudden freeze
which caused many of the lemmings to die would be a _____________ factor.

53.	When the lemmings ran out of food because there were so many of them, this would be
a ________________ factor.

54.	In this situation wolves which ate lemmings whenever they could find them would be
a ________________ factor.

55.	When a population stops growing because it has reached the maximum number that the
environment can support, we say that the population has reached what?
56.	Regular population cycles of rapid growth followed by massive die-off are known as

57.	Predation is considered to be a density dependent factor that controls the
population size of prey species. Give two examples of ways in which predators act in
density dependent ways in response to fluctuations in prey population sizes.

58.	Parasites may often kill their hosts, although they do not directly benefit from
host death. And yet, many ecologists believe that parasites may have beneficial effects on
their host populations. Why might this be so?

59.	In high elevation forested ecosystems of New Hampshire and Vermont, ecologists have
noticed a serious decline in certain tree species such as red spruce. When the affected
trees are studied, it often seems that parasitic beetles or microbes are involved. Other
scientists have stated that acid rain might be the cause of red spruce decline. Yet a third
group of scientists have argued that both factors are equally involved. How could this
third possibility be true, and which cause is likely to be density dependent, and which is
more likely to be density independent?

60.	How do interspecific and intraspecific competition differ from each other?

61.	Which tends to be more intense, intra or interspecific competition?  Explain why.

62.	The distribution pattern associated with organisms that are grouped together
because of availability of resources, for mating, or for protection from predators is
	a.	Random
	b.	Uniform
	c.	Aggregated
	d.	Social
	e.	Linear
63.	Cottonwood trees grow in groups only along streams and rivers in grasslands. This
is an example of what kind of distribution?
	a.	Random
	b.	Uniform
	c.	Aggregated
	d.	Community
	e.	Constant

64.	Some desert plants (such as the creosote bush) secrete chemicals which inhibit the
growth of nearby plants. This results in ________ distribution.
	a.	random
	b.	uniform
	c.	aggregate
	d.	density-independent
	e.	density-dependent

65.	When organisms (rainforest plants, for example) form no social groups and the
resources they need are evenly distributed, they will often show _________ distribution.
	a.	random
	b.	uniform
	c.	aggregate
	d.	individual
	e.	clumped

66.	Species which are territorial, such as nesting Redwing Blackbirds, often show a/an
_________ distribution pattern.
	a.	random
	b.	uniform
	c.	aggregate
	d.	temporal
	e.	sigmoidal

67.	If the distance between individuals in a population is relatively constant the
population is ____________ distributed.

68.	If adults of reproductive age are having just enough children to replace
themselves, then the population is said to have _______________ fertility.

69.	Animal species often show a clumped spatial pattern due to mating or cooperation;
uniform patterns might arise from a competition for resources such as nesting space. Desert
plants such as the perennial shrub Larrae tridentata often show uniform spatial patterns in
extremely dry desert conditions, and random spatial patterns in more mesic deserts. Why
might this be so?

70.	Just after the Industrial Revolution, many countries in Europe saw expanding
populations: infant mortality went down and family size increased. However, after World War
II, many countries in Eastern Europe are actually declining in population as families
choose to have either one or no children. Draw the 2 age-structure diagrams for a country
such as Hungary, with first the post-Industrial Revolution scenario, and then the current
scenario. Hint: number of individuals by age is represented on the x-axis, and age is
represented on the y-axis.

71.	The U.S. fertility rate in 1999 was 2.1 meaning that the average family had 2.1
offspring. Why is 2.1 considered to be replacement level fertility in developed countries,
and not 2? Finally, if the U.S. has replacement level fertility, why is the population
growing rapidly?

72.	If most of the individuals of a species die when they are young, that species will
exhibit a ________ survivorship curve.
	a.	convex
	b.	constant
	c.	concave
	d.	sigmoid (S-shaped)
	e.	declining

73.	If the individuals of a species are very likely to live until old age, that species
will exhibit a ________ survivorship curve.
	a.	convex
	b.	constant
	c.	concave
	d.	sigmoid (S-shaped)
	e.	declining

74.	If all the individuals of a species have an equal chance of dying at any age, that
species will exhibit a ________ survivorship curve.
	a.	convex
	b.	constant
	c.	concave
	d.	sigmoid (S-shaped)
	e.	declining
75.	Which survivorship curve is characteristic of many large animals including humans?
	a.	Early loss
	b.	Concave
	c.	Constant loss
	d.	Late loss
	e.	Uniform

76.	A graph which shows patterns of death or survivorship over time is known as what?

77.	What are the 3 shapes of survivorship curves, and what does each one tell about the

78.	Human populations have continued to grow because humans have increased the
____________ of the earth by agriculture, medicine, and technology.
	a.	biotic potential
	b.	evolutionary pressure
	c.	environmental resistance
	d.	fertility
	e.	carrying capacity

79.	In the 18th and 19th centuries people increased the capacity of the earth to
support more humans by the discoveries of the _____________ revolution.
	a.	cultural
	b.	agricultural
	c.	industrial-medical
	d.	social
	e.	demographic

80.	At current rates of growth there will be about ____ million more people on the
earth a year from now than there are today.
	a.	1
	b.	4
	c.	15
	d.	65
	e.	90
81.	Which best describes the reason for the very rapid growth of the human population
in the last 8,000 years?
	a.	Humans have a late-loss survivorship curve.
	b.	Environmental resistance does not apply to humans.
	c.	Climatic change has allowed the human species to expand its range.
	d.	Technology has allowed the species to overcome some environmental
	e.	The biotic potential for humans has increased.

82.	Population growth rates are high in less-developed countries because
	a.	Medicines have lowered death rates.
	b.	Wealth has not lowered birth rates.
	c.	Children are often an important economic advantage.
	d.	Social traditions support large families.
	e.	All of these are important reasons why population growth is high in
less-developed countries.

83.	In areas with a stable population, the number of children is
	a.	Increasing
	b.	Decreasing
	c.	Approximately equal to the number of adults
	d.	Higher than the number of adults
	e.	Lower than the number of adults

84.	In countries such as Nigeria which have large numbers of children under age 15, the
population is
	a.	Becoming larger
	b.	Becoming smaller
	c.	Staying the same
	d.	Hard to predict
	e.	Able to expand their carrying capacity

85.	If a population's age structure diagram looks like a pyramid, the:
	a.	Population is expanding
	b.	Population is remaining the same
	c.	Population will expand for at least a generation
	d.	Population is showing continuous exponential growth

86.	In countries such as France in which the number of children below 15 is
approximately equal to the number between 15 and 45, the population is
	a.	Expanding slowly
	b.	Stable
	c.	Shrinking slightly
	d.	Growing exponentially
	e.	Declining drastically

87.	Less-developed countries tend to have a(n) ________________ age diagram.
	a.	rectangular-shaped
	b.	inverted triangle
	c.	pyramid-shaped
	d.	square
	e.	round

88.	If people in less-developed countries reached replacement-level fertility
immediately, their populations would
	a.	Decline slowly.
	b.	Decline rapidly.
	c.	Become stable.
	d.	Continue to grow for many years.
	e.	Grow for a short time and then decline rapidly.

89.	The population of the USA continues to grow as a result of
	a.	Immigration
	b.	Babies born to baby boom generation parents
	c.	Increases in fertility
	d.	The birth rate was above replacement level fertility during the 1940's
through 1960's
	e.	All of the above are causes of population growth in the USA

90.	Americans use about ____ times as much energy as the world average.
	a.	2
	b.	3
	c.	4
	d.	5
	e.	6

91.	The United Nations estimates that by 2150 the world's population may stabilize at
about ______ billion.
	a.	7
	b.	8.5
	c.	11.5
	d.	15
	e.	20.5
92.	If all people in the world were to live at the level which Americans live in terms
of technology, wealth, education, etc., the population of the world would have to
___________________ in order to support them.
	a.	double
	b.	reduce by half
	c.	reduce to a fourth of current levels
	d.	reduce to less than a 10th of the current population
	e.	decline by 90%

93.	Which developed country has the fastest population growth rate today?
	a.	France
	b.	Denmark
	c.	China
	d.	USA
	e.	Russia

94.	At present, the earth's human population is:
	a.	Stable
	b.	Declining
	c.	Increasing exponentially
	d.	Increasing at a constant rate
	e.	Increasing at about 10% per year

95.	A population grows exponentially when:
	a.	the birth rate and the death rate are equal
	b.	the birth rate exceeds the death rate and there is no immigration or
	c.	emigration exceeds immigration and the birth rate equals the death rate
	d.	the birth rate equals the death rate and immigration is equal to emigration
	e.	the carrying capacity is exceeded

96.	Where do most of the people in the world live today, in developed or developing

97.	Why has it been so hard to come up with an accurate measure of the carrying
capacity of the earth?

98.	What factors determine the earth's carrying capacity for humans?

(c) 2002 Prentice-Hall, Inc. All rights reserved.
1.	e
2.	c
3.	They both are correct. An ecosystem is a network of interrelated living things and
their physical environment. The boundaries of an ecosystem may be drawn almost anywhere,
depending on the scope of the study.
4.	Bacteria in the petri dish grow exponentially when first added, but the population
stabilizes (and will eventually decline) as space and food become limiting. In the field,
bacterial populations have already reached equilibrium with food availability. New food is
"added" with plant inputs, but old food has been consumed so there is not a net
accumulation of food resources.
5.	Density-independent factors may include a mild winter, which reduces death rates
and thus causes a population to increase; the accidental spill of a pesticide might cause
the population to decrease in a manner that is density-independent. The increase in a
predator population would cause a density-dependent reduction in population; the reduction
of a competitor species might cause a density-dependent increase in population size.
6.	b
7.	a
8.	b
9.	c
10.	b
11.	b
12.	d
13.	c
14.	d
15.	e
16.	b
17.	False
18.	False
19.	biotic potential
20.	environmental resistance
21.	growth rate
22.	environmental resistance
23.	Changes per individual per unit of time.
24.	Birth + immigration = death + emigration
25.	The population grows by a fixed percentage of its size during each time period so
that the actual numbers of individuals being added to the population gets larger at an ever
increasing rate.
26.	Population growth will slow even if the number of offspring per woman remains the
27.	A bacterial population can increase more rapidly than an eagle population because
each bacterial cell can reproduce every 20 minutes, whereas eagles reproduce less often and
begin reproducing at an older age.
28.	a
29.	a
30.	e
31.	b
32.	d
33.	c
34.	a
35.	e
36.	a
37.	b
38.	a
39.	e
40.	a
41.	c
42.	e
43.	b
44.	b
45.	a
46.	b
47.	e
48.	True
49.	lag behind
50.	independent
51.	intraspecific
52.	b
53.	a
54.	a
55.	Its carrying capacity.
56.	Boom and bust cycles.
57.	Predators may not only adjust the number of prey that they eat in response to prey
abundance, but they might switch to alternate food sources when prey abundances are low or
specialize in feeding on the prey when population sizes are high. In addition, predators
may regulate the number of offspring that they produce in response to prey abundances.
58.	Parasites and predators tend to destroy weaker and less fit prey, leaving the
stronger or better-adapted prey to reproduce and pass genes to the next generation. Thus
the prey population is regulated but very fit individuals are not eliminated.
59.	Population size is a result of complex interactions between density dependent and
density independent regulation. Many parasites will respond to trees in a density dependent
way, but weaken the trees so that a density independent factor (acid rain) will kill them;
the reverse may also be true.
60.	Inter - between two species, intra - between members of the same species
61.	Intraspecific, because the individuals of the same species all need very similar
62.	c
63.	c
64.	b
65.	a
66.	b
67.	uniformly
68.	replacement level
69.	The uniform pattern probably arises from intense competition for water as a
resource; if 2 plants are too close together, either both will die or else the weaker one
will die. Under less intense competition, random factors of plant dispersal will overcome
the need for uniform spacing due to competition.
70.	The diagrams should look like the expanding and the shrinking diagrams of figure
71.	RLF is 2.1 because parents must replace both themselves and children who die before
reaching maturity. Immigration, and lag timing of the baby boom is causing the U.S.
population to expand.
72.	c
73.	a
74.	b
75.	d
76.	A survivorship curve
77.	Convex - Most individuals survive to old age
Constant - Equal chance of dying at any age
Concave - High infant mortality
78.	e
79.	c
80.	e
81.	d
82.	e
83.	c
84.	a
85.	b
86.	b
87.	c
88.	d
89.	e
90.	d
91.	c
92.	c
93.	d
94.	c
95.	b
96.	In less-developed countries
97.	Because humans have the ability to increase their own carrying capacity by a series
of revolutions in agriculture, industry, and medicine.
98.	The amount of water, light, nutrients, and space available to sustain the maximum
human population size indefinitely.