A group of individuals that belong to the same species and live in the same area
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population size
the total number of individuals within a defined area at a given time
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population density
the number of individuals per unit area at a given time
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population distribution
a description of how individuals are distributed with respect to one another
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Population sex ratio (PSR)
the ratio of males to females in a population
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population age structure
a description of how many individuals fit into particular age categories
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density dependent factors
limiting factor that depends on population size
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limiting resource
a resource that a population cannot live without and that occurs in quantities lower than the population would require to increase in size (water, food supply, nest sites...)
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carrying capacity (K)
the limit of how many individuals in a population the environment can sustain
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density-independent factor
limiting factor that affects all populations in similar ways, regardless of population size
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population growth models
mathematical equations that can be used to predict population size at any moment in time
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population growth rate
the number of offspring an individual can produce in a given time period, minus the deaths of the individual or its offspring during the same period
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intrinsic growth rate
the maximum potential for growth of a population under ideal conditions with unlimited resources
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exponential growth model (Nt=N0e^rt)
a growth model that estimates a population's future size (Nt) after a period of time (t), based on the intrinsic growth rate (r) and the number of reproducing individuals currently in the population (N0)
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J-shaped curve
the curve of the exponential growth model when graphed
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logistic growth model
a growth model that describes a population whose growth is initially exponential, but slows as the population approaches the carrying capacity of the environment
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S-shaped curve
the shape of the logistic growth model when graphed
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Overshoot
when a population becomes larger than the environment's carrying capacity
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die-off
a rapid decline in a population due to death
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K-selected species
a species with a low intrinsic growth rate that causes the population to increase slowly until it reaches carrying capacity
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r-selected species
a species that has a high intrinsic growth rate, which often leads to population overshoots and die-offs
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Traits of K-selected and R-selected species
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survivorship curve
a graph that represents the distinct patterns of species survival as a function of age
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corridor
strips of natural habitat that connect populations
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metapopulation
a group of spatially distinct populations that are connected by occasional movements of individuals between them
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competition
the struggle between organisms to survive in a habitat with limited resources
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competitive exclusion principle
no two species can occupy the same niche in the same habitat at the same time
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resource partitioning
when two species divide a resource based on differences in their behavior or morphology (temporal resource partitioning; spatial resource partitioning; morphological resource paritioning )
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Predation
An interaction in which one organism kills another for food.
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Parasitoids
organisms that lay eggs inside other organisms ( one specialized type of predator)
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parasitism
A relationship in which one organism lives on or in a host and harms it.
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Pathogen
a parasite that causes disease in its host
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Mutualism
A relationship between two species in which both species benefit (pseudomyrmex ant and acacia tree)
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Commensalism
A relationship between two organisms in which one organism benefits and the other is unaffected
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keystone species
A species that influences the survival of many other species in an ecosystem
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ecosystem engineers
a keystone species that creates or maintains habitat for other species
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ecological succession
the predictable replacement of one group of species by another group of species over time
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primary succession
An ecological succession that begins in an area where no biotic community previously existed
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secondary succession
Succession following a disturbance that destroys a community without destroying the soil
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pioneer species
a species that can colonize new areas rapidly and grow well in full sunshine
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climax stage
communities in late-stage succession with more complex species; succession "ends"
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succession occurs in a variety of aquatic ecosystems
over a time span of hundred to thousands of years, lakes are filled with sediments and slowly become terrestrial habitats
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species richness of a community is influenced by many factors
latitude, time, habitat size, distance from other communities
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Thomas Malthus
the human population could exceed Earth's carrying capacity
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factors that influence human populations
population size, birth and death rate, fertility, life expectancy, and migration
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Demography
The scientific study of population characteristics.
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Immigration
the movement of people into one country from another for the purpose of settlement
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Emigration
movement of individuals out of an area
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doubling time
the time required for a population to double in size
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the rule of 70
to find doubling time of pop, divide 70 by the percent of growth
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Total Fertility Rate (TFR)
The average number of children a woman will have throughout her childbearing years.
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Replacement level fertility
the total fertility rate required to offset the average number of deaths in a population in order to maintain the current population size
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developed country
a country with relatively high levels of industrialization and income
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developing country
a country with relatively low levels of industrialization and income
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life expectancy
The average number of years an individual can be expected to live, given current social, economic, and medical conditions.
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infant mortality
the number of deaths of children under 1 year of age per 1000 live birth
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child mortality
the number of deaths of children under age 5 per 1,000 live births
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Age-structure diagram
a visual representation of the number of individuals within specific age groups for a country, typically expressed for males and females
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Population Pyramid
an age structure diagram that is widest at the bottom and smallest at the top, typical of developing countries
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population momentum
continued population growth that does not slow in response to growth reduction measures
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theory of demographic transition
the theory that as a country moves from a subsistence economy to industrialization and increased affluence it undergoes a predictable shift in population growth
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family planning
the practice of regulating the number or spacing of offspring through the use of birth control
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Affluence
wealth
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IPAT equation
Impact = Population x Affluence x Technology
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urban area
an area that contains more than 385 people per square kilometer (1,000 people per square mile)
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The biotic potential of a population
is the maximum reproductive rate of a population
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clumping
the most common dispersion pattern for populations, individuals flock together
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cohort
a group of people from a given time period
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Community
All the different populations that live together in an area
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Dieback
A sudden population decline; also called a population crash.
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fecundity
fertility
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Generalist
Species that does not rely on a single source of prey
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inbreeding depression
when individuals with similar genotypes - typically relatives - breed with each other and produce offspring that have an impaired ability to survive and reproduce
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uniform dispersion pattern
a pattern in which the individuals of a population are evenly distributed over an area
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Crude Death Rate (CDR)
the number of deaths per 1,000 individuals per year
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Crude Birth Rate (CBR)
the number of births per 1,000 individuals per year
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post-industrialization
the shift from an industrial economy dominated by manufacturing jobs to an economy dominated by service-oriented information-intensive occupations.
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Pre-Industrialization
Traditional, agrarian, rural, poor health, famine and disease
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random dispersion pattern
a pattern in which the individuals of a population are spaced in an unpredictable way
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sex ratio
The number of males per 100 females in the population.
Studied by 7 people
