Chapter 19 Glossary, Summary, and Practice Questions
KEY TERMS
age structure the distribution of the proportion of population members in each age class
birth rate the number of births within a population at a specific point in time
carrying capacity the maximum number of individuals of a population that can be supported by the limited resources of a habitat
climax community the final stage of succession, where a stable community is formed by a characteristic assortment of plant and animal species
competitive exclusion principle no two species within a habitat can coexist indefinitely when they compete for the same resources at the same time and place
death rate the number of deaths within a population at a specific point in time
demography the statistical study of changes in populations over time
density-dependent regulation
size
the regulation of population in which birth and death rates are dependent on population
density-independent regulation
size
the regulation of population in which the death rate is independent of the population
environmental disturbance a change in the environment caused by natural disasters or human activities exponential growth an accelerating growth pattern seen in populations where resources are not limiting foundation species a species which often forms the major structural portion of the habitat
host an organism a parasite lives on
intraspecific competition the competition among members of the same species
island biogeography the study of life on island chains and how their geography interacts with the diversity of species found there
J-shaped growth curve the shape of an exponential growth curve
K-selected species a species suited to stable environments that produce a few, relatively large offspring and provide parental care
keystone species a species whose presence is key to maintaining biodiversity in an ecosystem and to upholding an ecological community’s structure
life table a table showing the life expectancy of a population member based on its age
logistic growth the leveling off of exponential growth due to limiting resources
mark and recapture a method used to determine population size in mobile organisms
mimicry an adaptation in which an organism looks like another organism that is dangerous, toxic, or distasteful to its predators
mortality rate the proportion of population surviving to the beginning of an age interval that dies during that age interval
mutualism a symbiotic relationship between two species where both species benefit
one-child policy a policy in China to limit population growth by limiting urban couples to have only one child or face a penalty of a fine
parasite an organism that uses resources from another species: the host
pioneer species the first species to appear in primary and secondary succession population density the number of population members divided by the area being measured population size the number of individuals in a population
primary succession the succession on land that previously has had no life
quadrat a square within which a count of individuals is made that is combined with other such counts to determine population size and density in slow moving or stationary organisms
r-selected species a species suited to changing environments that produce many offspring and provide little or no parental care
relative species abundance the absolute population size of a particular species relative to the population size of other species within the community
S-shaped growth curve the shape of a logistic growth curve
secondary succession the succession in response to environmental disturbances that move a community away from its equilibrium
species distribution pattern the distribution of individuals within a habitat at a given point in time
species richness the number of different species in a community
survivorship curve a graph of the number of surviving population members versus the relative age of the member
zero population growth the steady population size where birth rates and death rates are equal
CHAPTER SUMMARY
Population Demographics and Dynamics
Populations are individuals of a species that live in a particular habitat. Ecologists measure characteristics of populations: size, density, and distribution pattern. Life tables are useful to calculate life expectancies of individual population members. Survivorship curves show the number of individuals surviving at each age interval plotted versus time.
Population Growth and Regulation
Populations with unlimited resources grow exponentially—with an accelerating growth rate. When resources become limiting, populations follow a logistic growth curve in which population size will level off at the carrying capacity.
Populations are regulated by a variety of density-dependent and density-independent factors. Life-history characteristics, such as age at first reproduction or numbers of offspring, are characteristics that evolve in populations just as anatomy or behavior can evolve over time. The model of r– and K-selection suggests that characters, and possibly suites of characters, may evolve adaptations to population stability near the carrying capacity (K-selection) or rapid population growth and collapse (r-selection). Species will exhibit adaptations somewhere on a continuum between these two extremes.
The Human Population
Earth’s human population is growing exponentially. Humans have increased their carrying capacity through technology, urbanization, and harnessing the energy of fossil fuels. The age structure of a population allows us to predict population growth. Unchecked human population growth could have dire long-term effects on human welfare and Earth’s ecosystems.
Community Ecology
Communities include all the different species living in a given area. The variety of these species is referred to as biodiversity. Many organisms have developed defenses against predation and herbivory, including mechanical defenses, warning coloration, and mimicry. Two species cannot exist indefinitely in the same habitat competing directly for the same resources. Species may form symbiotic relationships such as commensalism, mutualism, or parasitism. Community
structure is described by its foundation and keystone species. Communities respond to environmental disturbances by succession: the predictable appearance of different types of plant species, until a stable community structure is established.
ART CONNECTION QUESTIONS
- Figure 19.2 As this graph shows, population density typically decreases with increasing body size. Why do you think this is the case?
- Figure 19.6 If the major food source of seals declines due to pollution or overfishing, which of the following would likely occur?
- The carrying capacity of seals would decrease, as would the seal population.
- The carrying capacity of seals would decrease, but the seal population would remain the same.
REVIEW QUESTIONS
- Which of the following methods will provide information to an ecologist about both the size and density of a population?
- mark and recapture
- mark and release
- quadrat
- life table
- Which of the following is best at showing the life expectancy of an individual within a population?
- quadrat
- mark and recapture
- survivorship curve
- life table
- Human populations have which type of survivorship curve?
- Type I
- Type II
- Type III
- Type IV
- Species with limited resources usually exhibit a(n)
growth curve.
- logistic
- logical
- experimental
- exponential
- The maximum growth rate characteristic of a species is called its .
- limit
- carrying capacity
- biotic potential
- exponential growth pattern
- The population size of a species capable of being supported by the environment is called its .
- limit
- carrying capacity
The number of seal deaths would increase, but the number of births would also increase, so the population size would remain the same.- The carrying capacity of seals would remain the same, but the population of seals would decrease.
- Figure 19.11 Age structure diagrams for rapidly growing, slow growing, and stable populations are shown in stages 1 through 3. What type of population change do you think stage 4 represents?
- biotic potential
- logistic growth pattern
- Species that have many offspring at one time are usually:
- r-selected
- K-selected
- both r- and K-selected
- not selected
- A forest fire is an example of regulation.
- density-dependent
- density-independent
- r-selected
- K-selected
- A country with zero population growth is likely to be
.
- in Africa
- in Asia
- economically developed
- economically underdeveloped
- Which type of country has the greatest proportion of young individuals?
- economically developed
- economically underdeveloped
- countries with zero population growth
- countries in Europe
- Which of the following is not a way that humans have increased the carrying capacity of the environment?
- agriculture
- using large amounts of natural resources
- domestication of animals
- use of language
- The first species to live on new land, such as that formed from volcanic lava, are called.
- climax community
- keystone species
- foundation species
- pioneer species
- A symbiotic relationship where both of the co-existing species benefit from the interaction is called .
- commensalism
- parasitism
- mutualism
CRITICAL THINKING QUESTIONS
- Describe how a researcher would determine the size of a penguin population in Antarctica using the mark and release method.
- Describe the growth at various parts of the S-shaped curve of logistic growth.
- Give an example of how density-dependent and density-independent factors might interact.
communism- When an invasive species alters the community structure it is introduced to, what can the consequence be?
- extinction of economically important species
- reduced predation on some native species
- increased predation on some native species
- all of the above
- Describe the age structures in rapidly growing countries, slowly growing countries, and countries with zero population growth.
- Describe the competitive exclusion principle and its effects on competing species.
- Describe the potential effects when a keystone species is removed from a community.
