Unit 5 (Chapters 8, 9 & 10) – Community and Population Ecology
Reading:
Chapter 8 – Community Ecology
Chapter 9 – Population Ecology
Chapter 10 – Applying Population Ecology to the Human Population
Supplemental reading:
A Jellyfish Explosion in a Warming World
Kudzu
Zebra Mussel
Human Population Control
China’s One-Child Policy
Family Planning in India
Demographics of Japan
Moral Implications of Cultural Carrying Capacity
Activities:
Micro-Communities
World Population Growth
Questions for Review
Chapter 8
Instructions: You should be able to answer these questions once you have finished the chapter:
1. Define the boldfaced terms in this chapter.
2. Describe the ecological and economic importance of flying foxes in tropical forests.
3. List four characteristics of the structure of a community or ecosystem. Distinguish among species diversity, species richness, and
species evenness.
4. What are the three most species-rich environments? How does species diversity vary with (a) latitude in terrestrial communities and (b)
pollution in aquatic systems?
5. What two factors determine the species diversity found on in isolated ecosystem such as an island? What is the theory of island
biogeography? How do the size of an island and its distance from a mainland affect its species diversity?
6. Distinguish among native, nonnative, indicator, and keystone species, and give an example of each.
7. Why are birds good indicator species? Explain why amphibians are considered indicator species, and list reasons for declines in many
of their populations.
8. Describe the keystone ecological roles of (a) flying foxes, (b) alligators, and (c) some shark species. What can happen in an ecosystem
that loses a keystone species?
9. Define and give an example of a foundation species.
10. What is interspecific competition? What are four possible consequences when the niches of two species competing in the same area
overlap to a large degree?
11. Define and give two examples of resource partitioning. How does it allow species to avoid overlap of their fundamental niches?
12. What is predation? Describe the predator–prey relationship, and give two examples of this type of species interaction. Why are sharks
important species?
13. Give two examples of how predators increase their chances of finding prey by (a) pursuit and (b) ambush.
14. List six ways (adaptations) used by prey to avoid their predators, and give an example of each type.
15. Define and give two examples of parasitism, and explain how it differs from predation. What is the ecological importance of
parasitism?
16. Define and give two examples of (a) mutualism and (b) commensalism.
17. Distinguish between primary succession and secondary succession. Distinguish among pioneer (or early successional) species,
midsuccessional plant species, and late successional plant species. Distinguish among facilitation, inhibition, and tolerance as factors that
affect how and at what rate succession occurs.
18. Give three examples of environmental disturbances, and explain how they can affect succession. How can some disturbances be
beneficial to ecosystems? What is the intermediate disturbance hypothesis?
19. Explain why most ecologists contend that (a) the details of succession are not predictable and (b) no balance of nature exists.
20. Distinguish among inertia, constancy, and resilience, and explain how they help maintain stability in an ecosystem.
21. Does high species diversity always increase ecosystem stability? Explain.
22. What is the precautionary principle, and why do many scientists find it a useful strategy for dealing with some of the environmental
problems we face? What are some disadvantages of widespread use of the precautionary principle?
Chapter 9
Instructions: You should be able to answer these questions once you have finished the chapter:
1. Define the boldfaced terms in this chapter.
2. Explain how the populations of southern sea otters and kelp interact and why the southern sea otter is considered a keystone species.
3. What is population dynamics? Why are the populations of most species found in clumps or groups?
4. What four factors affect population change? Write an equation showing how population change is related to births, deaths, immigration,
and emigration.
5. What is the biotic potential of a population? What are four characteristics of a population with a high intrinsic rate of increase (r) ?
6. What are environmental resistance and carrying capacity? How do biotic potential and environmental resistance interact to determine
carrying capacity?
7. Distinguish between exponential and logistic growth of a population, and give an example of each type.
8. How can a population overshoot its carrying capacity, and what are the consequences of doing this?
9. Distinguish between density-dependent and density-independent factors that affect a population’s size, and give an example of each.
10. Distinguish among stable, irruptive, irregular, and cyclic forms of population change.
11. Distinguish between top-down control and bottom-up control of a population’s size. Use these concepts to describe the effects of the
predator–prey interactions between the snowshoe hare and the Canadian lynx on the population of each species.
12. Distinguish between asexual reproduction and sexual reproduction. What are the disadvantages and advantages of sexual
reproduction?
13. List the characteristics of (a) r-selected or opportunist species and (b) K-selected or competitor species, and give two examples of
each type. Under what environmental conditions are you most likely to find (a) r-selected species and (b) K-selected species?
14. What is a survivorship curve, and how is it used? List three general types of survivorship curves, and give an example of a species
with each type.
15. How can genetic diversity affect the survival of small, isolated populations? Distinguish between the founder effect, demographic
bottleneck, and genetic drift. What is a metapopulation?
16. List nine potentially harmful ways in which humans modify natural ecosystems.
17. List four principles of sustainability observed in natural systems and describe how they can be adapted for developing more
sustainable human societies.
18. List four guidelines we could use to help us live more sustainably.
Chapter 10
Instructions: You should be able to answer these questions once you have finished the chapter:
1. Define the boldfaced terms in this chapter.
2. How did Thailand reduce its birth rate?
3. What is demography and how does it affect you?
4. What four factors affect the size of the human population in a particular area? What are the crude birth rate and the crude death rate?
5. About how many people are added to the world’s population each year and each day? How is the annual rate of population change
calculated? What three countries have the world’s largest populations?
6. What are doubling time and the rule of 70? Use the rule of 70 to calculate how many years it would take for the population of a country
to double if its population was growing by 2% a year.
7. What is fertility? Distinguish between replacement-level fertility and total fertility rate. Explain why replacement-level fertility is higher
than 2. Explain why reaching replacement-level fertility does not mean an immediate halt in population growth.
8. How have fertility rates and birth rates changed in the United States since 1910? How rapidly is the U.S. population growing?
9. List ten factors that affect birth rates and fertility rates.
10. List five reasons why the world’s death rate has declined over the past 100 years.
11. Distinguish between life expectancy and infant mortality rate. Why is infant mortality the best measure of a society’s quality of life? List
three factors that keep the U.S. infant mortality higher than it could be.
12. Describe immigration in the United States in terms of numbers. List the major arguments for and against reducing immigration in the
United States.
13. What is the age structure of a population? Explain why the current age structure of the world’s population means the population will
keep growing for at least another 50 years even if the replacement-level rate of 2.1 is somehow reached globally tomorrow.
14. Draw the general shape of an age structure diagram for a country undergoing (a) rapid population growth, (b) slow population growth,
(c) zero population growth, and (d) population decline.
15. What percentage of population is under age 15 in (a) the world, (b) developed countries, and (c) developing countries? Explain how
age structure diagrams can be used to make population and economic projections.
16. What are the benefits and potentially harmful effects of rapid population decline? What are some effects of population decline from a
rise in death rates from AIDS?
17. List the major arguments for and against reducing birth rates globally.
18. What is the demographic transition, and what are its four phases? What factors might keep many developing countries from making
the demographic transition?
19. What is family planning, and what are the advantages of using this approach to reduce the birth rate? Describe the success of family
planning in slowing population growth in Iran.
20. Explain how empowering women can help reduce birth rates, poverty, and environmental degradation.
21. Describe and compare the success China and India have had in reducing their birth rates.
21. List the eight goals of the current UN plan to stabilize the world’s population at 7.8 billion by 2050, instead of the projected 8.9 billion.
Key Terms
Chapter 8
alien species
See nonnative species.
annual
Plant that grows, sets seed, and dies in one growing season. Compare perennial.
carnivore
Animal that feeds on other animals. Compare herbivore, omnivore.
climax community
See mature community.
commensalism
An interaction between organisms of different species in which one type of organism benefits and the other type
is neither helped nor harmed to any great degree. Compare mutualism.
competitive exclusion
principle
No two species can occupy exactly the same fundamental niche indefinitely in a habitat where there is not
enough of a particular resource to meet the needs of both species. See ecological niche, fundamental niche,
realized niche.
complexity
In ecological terms, refers to the number of species in a community at each trophic level and the number of
trophic levels in a community.
constancy
Ability of a living system, such as a population, to maintain a certain size. Compare inertia, resilience. See
homeostasis.
disturbance
A discrete event that disrupts an ecosystem or community. Examples of natural disturbances include fires,
hurricanes, tornadoes, droughts, and floods. Examples of human-caused disturbances include deforestation,
overgrazing, and plowing.
early successional
plant species
Plant species found in the early stages of succession that grow close to the ground, can establish large
populations quickly under harsh conditions, and have short lives. Compare late successional plant species,
midsuccessional plant species.
ecological succession Process in which communities of plant and animal species in a particular area are replaced over time by a series
of different and often more complex communities. See primary succession, secondary succession.
epiphyte
Plant that uses its roots to attach itself to branches high in trees, especially in tropical forests.
exotic species
See nonnative species.
exploitation
competition
Situation in which two competing species have equal access to a specific resource but differ in how quickly or
efficiently they exploit it. See interference competition, interspecific competition.
habitat fragmentation
Breakup of a habitat into smaller pieces, usually as a result of human activities.
herbivore
Plant-eating organism. Examples are deer, sheep, grasshoppers, and zooplankton. Compare carnivore,
omnivore.
homeostasis
Maintenance of favorable internal conditions in a system despite fluctuations in external conditions. See
constancy, inertia, resilience.
host
Plant or animal on which a parasite feeds.
immature community
Community at an early stage of ecological succession. It usually has a low number of species and ecological
niches and cannot capture and use energy and cycle critical nutrients as efficiently as more complex, mature
communities. Compare mature community.
immigrant species
See nonnative species.
indicator species
Species that serve as early warnings that a community or ecosystem is being degraded. Compare keystone
species, native species, nonnative species.
inertia
Ability of a living system to resist being disturbed or altered. Compare constancy, resilience.
interference
competition
Situation in which one species limits access of another species to a resource, regardless of whether the
resource is abundant or scarce. See exploitation competition, interspecific competition.
interspecific
competition
Attempts by members of two or more species to use the same limited resources in an ecosystem. See
competition, competitive exclusion principle, intraspecific competition.
intraspecific
competition
Attempts by two or more organisms of a single species to use the same limited resources in an ecosystem. See
competition, interspecific competition.
keystone species
Species that play roles affecting many other organisms in an ecosystem. Compare indicator species, native
species, nonnative species.
late successional
plant species
Mostly trees that can tolerate shade and form a fairly stable complex forest community. Compare early
successional plant species, midsuccessional plant species.
mature community
Fairly stable, self-sustaining community in an advanced stage of ecological succession; usually has a diverse
array of species and ecological niches; captures and uses energy and cycles critical chemicals more efficiently
than simpler, immature communities. Compare immature community.
midsuccessional
plant species
Grasses and low shrubs that are less hardy than early successional plant species. Compare early successional
plant species, late successional plant species.
mutualism
Type of species interaction in which both participating species generally benefit. Compare commensalism.
native species
Species that normally live and thrive in a particular ecosystem. Compare indicator species, keystone species,
nonnative species.
nonnative species
Species that migrate into an ecosystem or are deliberately or accidentally introduced into an ecosystem by
humans. Compare native species.
omnivore
Animal that can use both plants and other animals as food sources. Examples are pigs, rats, cockroaches, and
people. Compare carnivore, herbivore.
parasite
Consumer organism that lives on or in and feeds on a living plant or animal, known as the host, over an
extended period of time. The parasite draws nourishment from and gradually weakens its host; it may or may
not kill the host. See parasitism.
parasitism
Interaction between species in which one organism, called the parasite, preys on another organism, called the
host, by living on or in the host. See host, parasite.
perennial
Plant that can live for more than 2 years. Compare annual.
persistence
How long a pollutant stays in the air, water, soil, or body. See also inertia.
pioneer community
First integrated set of plants, animals, and decomposers found in an area undergoing primary ecological
succession. See immature community, mature community.
pioneer species
First hardy species, often microbes, mosses, and lichens, that begin colonizing a site as the first stage of
ecological succession. See ecological succession, pioneer community.
predation
Situation in which an organism of one species (the predator) captures and feeds on parts or all of an organism
of another species (the prey).
predator
Organism that captures and feeds on parts or all of an organism of another species (the prey).
predator&endash;prey Interaction between two organisms of different species in which one organism, called the predator, captures and
relationship
feeds on parts or all of another organism, called the prey.
prey
Organism that is captured and serves as a source of food for an organism of another species (the predator).
primary succession
Ecological succession in a bare area that has never been occupied by a community of organisms. See
ecological succession. Compare secondary succession.
resilience
Ability of a living system to restore itself to original condition after being exposed to an outside disturbance that
is not too drastic. See constancy, inertia.
resource partitioning
Process of dividing up resources in an ecosystem so that species with similar needs (overlapping ecological
niches) use the same scarce resources at different times, in different ways, or in different places. See ecological
niche, fundamental niche, realized niche.
secondary consumer
Organism that feeds only on primary consumers. Compare detritivore, omnivore, primary consumer.
secondary
succession
Ecological succession in an area in which natural vegetation has been removed or destroyed but the soil is not
destroyed. See ecological succession. Compare primary succession.
species equilibrium
model
See theory of island biogeography.
stability
Ability of a living system to withstand or recover from externally imposed changes or stresses. See constancy,
inertia, resilience.
succession
See ecological succession, primary succession, secondary succession.
symbiosis
Any intimate relationship or association between members of two or more species. See symbiotic relationship.
symbiotic relationship Species interaction in which two kinds of organisms live together in an intimate association. Members of the
participating species may be harmed by, benefit from, or be unaffected by the interaction. See commensalism,
interspecific competition, mutualism, parasitism, predation.
territoriality
Process in which organisms patrol or mark an area around their home, nesting, or major feeding site and defend
it against members of their own species.
theory of island
biogeography
The number of species found on an island is determined by a balance between two factors: the immigration rate
(of species new to the island) from other inhabited areas and the extinction rate (of species established on the
island). The model predicts that at some point the rates of immigration and extinction will reach an equilibrium
point that determines the island's average number of different species (species diversity).
Chapter 9
asexual
reproduction
Reproduction in which a mother cell divides to produce two identical daughter cells that are clones of the
mother cell. This type of reproduction is common in single-celled organisms. Compare sexual reproduction.
biotic potential
Maximum rate at which the population of a given species can increase when there are no limits on its rate of
growth. See environmental resistance.
carrying
capacity (K)
dieback
environmental
resistance
Maximum population of a particular species that a given habitat can support over a given period.
Sharp reduction in the population of a species when its numbers exceed the carrying capacity of its habitat.
See carrying capacity.
All the limiting factors that act together to limit the growth of a population. See biotic potential, limiting factor.
exponential
growth
Growth in which some quantity, such as population size or economic output, increases at a constant rate per
unit of time. An example is the growth sequence 2, 4, 8, 16, 32, 64 and so on; when the increase in quantity
over time is plotted, this type of growth yields a curve shaped like the letter J. Compare linear growth.
genetic drift
Change in the genetic composition of a population by chance. It is especially important for small populations.
intrinsic rate of
increase (r)
Rate at which a population could grow if it had unlimited resources. Compare environmental resistance.
J-shaped curve
Curve with a shape similar to that of the letter J; can represent prolonged exponential growth. See exponential
growth.
K-selected
species
Species that produce a few, often fairly large offspring but invest a great deal of time and energy to ensure
that most of those offspring reach reproductive age. Compare r-selected species.
K-strategists
See K-selected species.
limiting factor
Single factor that limits the growth, abundance, or distribution of the population of a species in an ecosystem.
See limiting factor principle.
limiting factor
principle
Too much or too little of any abiotic factor can limit or prevent growth of a population of a species in an
ecosystem, even if all other factors are at or near the optimum range of tolerance for the species.
linear growth
Growth in which a quantity increases by some fixed amount during each unit of time. An example is growth
that increases in the sequence 2, 4, 6, 8, 10, and so on. Compare exponential growth.
logistic growth
Pattern in which exponential population growth occurs when the population is small, and population growth
decreases steadily with time as the population approaches the carrying capacity. See S-shaped curve.
monoculture
Cultivation of a single crop, usually on a large area of land. Compare polyculture, polyvarietal cultivation.
pathogen
Organism that produces disease.
population
density
Number of organisms in a particular population found in a specified area or volume.
population
dispersion
General pattern in which the members of a population are arranged throughout its habitat.
population
distribution
Variation of population density over a particular geographic area. For example, a country has a high
population density in its urban areas and a much lower population density in rural areas.
population
dynamics
Major abiotic and biotic factors that tend to increase or decrease the population size and age and sex
composition of a species.
population size
Number of individuals making up a population's gene pool.
r-selected
species
Species that reproduce early in their life span and produce large numbers of usually small and short-lived
offspring in a short period. Compare K-selected species.
r-strategists
See r-selected species.
reproduction
Production of offspring by one or more parents.
reproductive
potential
See biotic potential.
S-shaped curve
Leveling off of an exponential, J-shaped curve when a rapidly growing population exceeds the carrying
capacity of its environment and ceases to grow.
sexual
reproduction
Reproduction in organisms that produce offspring by combining sex cells or gametes (such as ovum and
sperm) from both parents. This produces offspring that have combinations of traits from their parents.
Compare asexual reproduction.
survivorship
curve
Graph showing the number of survivors in different age groups for a particular species.
Chapter 10
age structure
Percentage of the population (or number of people of each sex) at each age level in a population.
birth rate
See crude birth rate.
crude birth rate
Annual number of live births per 1,000 people in the population of a geographic area at the midpoint of a given year.
Compare crude death rate.
crude death rate
Annual number of deaths per 1,000 people in the population of a geographic area at the midpoint of a given year.
Compare crude birth rate.
death rate
See crude death rate.
demographic
transition
Hypothesis that countries, as they become industrialized, have declines in death rates followed by declines in birth
rates.
demography
The study of the size, composition, and distribution of human populations and the causes and consequences of
changes in these characteristics.
doubling time
The time it takes (usually in years) for the quantity of something growing exponentially to double. It can be calculated
by dividing the annual percentage growth rate into 70.
family planning
Providing information, clinical services, and contraceptives to help people choose the number and spacing of children
they want to have.
fertility
The number of births that occur to an individual woman or in a population.
immigration
Migration of people into a country or area to take up permanent residence.
infant mortality
rate
Number of babies out of every 1,000 born each year that die before their first birthday.
life expectancy
Average number of years a newborn infant can be expected to live.
population
change
An increase or decrease in the size of a population. It is equal to (Births + Immigration) - (Deaths + Emigration).
replacement-level Number of children a couple must have to replace them. The average for a country or the world usually is slightly
fertility
higher than 2 children per couple (2.1 in the United States and 2.5 in some developing countries) because some
children die before reaching their reproductive years. See also total fertility rate.
rule of 70
Doubling time (in years) = 70/(percentage growth rate). See doubling time, exponential growth.
total fertility rate
Estimate of the average number of children who will be born alive to a woman during her lifetime if she passes
(TFR)
through all her childbearing years (ages 15-44) conforming to age-specific fertility rates of a given year. In simpler
terms, it is an estimate of the average number of children a woman will have during her childbearing years.
zero population
growth (ZPG)
State in which the birth rate (plus immigration) equals the death rate (plus emigration) so that the population of a
geographic area is no longer increasing.