Unit 5 (Chapters 8, 910) – 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 relationship / Interaction between two organisms of different species in which one organism, called the predator, captures and 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) / Maximum population of a particular species that a given habitat can support over a given period.
dieback / Sharp reduction in the population of a species when its numbers exceed the carrying capacity of its habitat. See carrying capacity.
environmental resistance / 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