53.1-5 – Flashcards
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define population ecology
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the study of population in relation to their environment, including environmental influences on population density and distribution, age structure, and variation in population size
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dynamic biological processes influence ________________
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population density, dispersion, and demographics
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define population
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a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring
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define density
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the number of individuals per unit area or volume changes as individuals are added to or removed from a population
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define dispersion
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the pattern of spacing among individuals within the boundaries of a population
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what is the mark-recapture method?
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a sampling technique used to estimate the size of wild animal populations
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how do population ecologists estimate density?
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from number of nests, burrows, tracks, fecal droppings
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define immigration
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the influx of new individuals into a population form other areas
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define emigration
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the movement of individuals out of a population
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what are the patterns of dispersion within a population's geographic range?
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clumped uniform random
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clumped dispersion
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the most common pattern where individuals are aggregated in patches plants and fungi are often clumped where factors favor germination and growth
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uniform dispersion
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evenly spaced pattern of dispersion may result from direct interactions between individuals in the population, such as territoriality
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define territoriality
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a behavior in which an animal defends a bounded physical space against encroachment by other individuals, usually of its own species
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random dispersion
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unpredictable spacing the position of each individual in a population is independent of other individuals occurs in the absence of strong attractions or repulsions among individuals or where key physical or chemical factors are relatively constant across the area ex: plants by windblown seeds
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define demography
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the study of changes over time in the vital statistics of populations, especially birth and death rates uses life tables and survivorship curves
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define life table
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an age specific summary of the survival pattern of a population
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what is the best way to construct a life table?
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to follow the fate of a cohort
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define cohort
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a group of individuals of the same age in a population
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define survivorship curve
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a plot of the number of members of a cohort that are still alive at each age one way to represent age specific mortality three types: type I, II, III
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type I survivorship curve
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flat at the start, reflecting low death rates during early and middle life, and then drops steeply as death rates increase among older age groups many large animals including humans that produce few offspring but provide good care
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type III survivorship curve
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drops sharply at the start, reflecting very high death rates for the young, but flattens out as death rates decline for those few that survive the early period of die off usually organisms that produce large amounts of offspring but provide little to no care, such as long lived plants, fishes, and marine invertebrates
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type II survivorship curve
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intermediate, with constant death rate over the organisms life span (straight line) squirrels, rodents, annual plants
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define reproductive table
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an age specific summary of the reproductive rates in a population
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the exponential model describes ___
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population growth in an idealized, unlimited environmnet
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what are population ecologist most interested in?
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the difference between the per capita birth rate and per capita death rate, which is the per capita rate of increase
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define zero population growth(ZPG)
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a period of stability in population size, when additions through population through births and immigration are balanced by subtractions through deaths and emigration
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define exponential population growth
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growth of a population in an ideal, unlimited environment, represented by a j-shaped curve when population size is plotted over time assumes resources are unlimited with unlimited reproduction
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the j-shaped curve of exponential growth is characteristic of ___
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some populations that are introduced into a new environment or whose numbers have been drastically reduced by an event and are rebounding
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the logistic model describes___
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the logistic model describes how a population grows more slowly as it nears its carrying capacity
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define carrying capacity
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the maximum population size that can be supported by the available resources, symbolized as K
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what are some limiting factors of carrying capacity?
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energy shelter refuge from predators nutrient availability water suitable nesting sites
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define logistic population growth
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population growth that levels off as population size approaches carrying capacity the per capita rate of increase approaches zero as the carrying capacity is reached produces a sigmoid(S-shaped) growth curve when N(population size) is plotted over time
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life history traits are products of _________
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natural selection
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define life history
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the traits that affect an organisms's schedule of reproduction and survival
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what are the three main variables of life history?
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when reproduction begins how often the organism reproduces how many offspring are produced per reproductive episode
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define semelparity
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reproduction in which an organism produces all of its offspring in a single event; also known as big band reproduction example: salmon and agave plant
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define iteroparity
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reproduction in which adults produce offspring over many years; also known as repeated reproduction produce few but large offspring
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what are the two critical factors between selemparity and iteroparity?
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survival rate of the offspring and the likelihood that the adult will survive to reproduce again when survival rate of offspring is low, semelparity is favored because adults are also less likely to survive in such environments iteroparity is more favorable in dependable environments, where adults are more likely to survive to breed again and where competition for resources may be intense
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define K-selection
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selection for life history traits that are sensitive to population density; also called density dependent selection favored at high density
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define r-selection
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selection for life history traits that maximize reproductive success in uncrowded environments; also called density independent selection
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many factors that regulate population growth are ____________
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density dependent
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density independent
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referring to any characteristic that is not affected by population density ex: a birth or death rate that does not change with population density
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density dependent
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referring to any characteristic that varies with population density acts as a negative feedback between population density and rates of birth and death ex: death rate that rises as population density rises
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what are the mechanisms of density dependent regulation?
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competition for resources predation intrinsic factors toxic wastes territoriality disease
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how does competition for resources affect population growth?
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increasing population density intensifies competition for resources, reducing reproductive rates
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how does predation affect population growth?
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can be important if a predator captures more food as the population density of the prey increases predators may feed preferentially on that species if population builds up
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how do intrinsic factors affect population growth?
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intrinsic physiological factors sometimes regulate population size reproduction may drop at high population densities
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how do toxic wastes affect population growth?
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organisms produce wastes, and too much waste is toxic
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how does territoriality affect population growth?
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territoriality can limit population density when space becomes the resource for which individuals compete maintaining territory increases likelihood that animal will capture enough food to reproduce surplus means territoriality is restricting population growth
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how does disease affect populate growth?
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diseases have a higher transmission rate in higher crowded areas
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define population dynamics
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the study of how complex interactions between biotic and abiotic factors influence variations in population size
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define metapopulation
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a group of spatially separated populations of one species that interact through immigration and emigration
