BIO 307: POPULATION
27 Cards in this Set
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What is population ecology?
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studying the interactions involving populations -factors that determine their distribution and abundance
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What to study?
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-changes in population size
-courses and texts always focus on growth
-declining populations sizes more interesting and important?
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Origins of Populations for Ecology
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-developed as part of a number of applied fields, examples: fisheries, wildlife, pest control
-ecology emphasis on development and testing of mathematical models of populations processes
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Testing of Populations
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-determine sustainable harvest levels
-minimum viable population sizes for threatened and endangered populations
-control methods to most effectively slow growth of pest populations
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Population
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group of individuals of the same species in a particular area
-assume that group of individuals is interbreeding
-area they are living in has a natural boundary (lake, island)
-or can be defined arbitrarily (political entities: county, state)
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Geographic Range
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boundaries for a population can be geographic barriers (mountains, oceans) or environmental conditions beyond tolerance limit of species (temperature, amount of rain, dryness)
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Tolerance Limits
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minimum and maximum levels beyond which a particular species cannot survive or reproduce
-many species exhibit tolerance limits that are more critical for the young that for the adults
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Shelford's Law of Tolerance
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For an organism to succeed in a given environment, each of a complex set of conditions must remain within the tolerance range of that organism and if any condition exceeds the minimum or maximum tolerance of that organism, it will fail to thrive
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Subpopulation
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Within a geographical range of a species there are often smaller distinct populations
-subpopulations are described precisely by environmental tolerance limits
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Metapopulation
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collective of local subpopulations
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Abundance
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number of individuals in a populations
(Helps determine population density and area over which population is distributed)
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Density of Population
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number or organisms per unit area or per unit volume
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Population Abundance
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= Density x Area
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Spatial Distribution
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-randomly arranged (dispersed all over in random spots) (dandelions)
-regularly or uniformly arranged (dispersed in a neat pattern) (creosote brush)
-clumped (dispersed in groups in a random order) (elephants)
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Methods for Determining Density Population
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-count all individuals
-sample a subset of population and obtain a mean density (sessile and conspicuous organisms, quadrat or subunits, transects)
-mark and recapture
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Quadrat Estimates
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-total area of interest is divided into subunits or "quadrats"
-subunits are often random measured in a square plot along a transect (line)
-most conveniently applied to small, sedentary organisms that are easily counted and unlikely to avoid "capture' in the quadrat during counting
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N =
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predicted total number of individuals in the population
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Y =
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number of quadrats (sampling units) within which the entire population is contained
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n =
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number of individuals in each quadrat
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y =
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number of quadrats sampled
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Ñ = (lower case N)
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mean number of individuals per quadrat
=∑n/y
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Petersen-Lincoln estimator
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N=nM/r
N=number of individuals
M=total number marked individuals
n=number of individuals caught at censusing
r=number of marked individuals caught at censusing
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Population Density Factors
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-resource availability or predation
-temperature
-food
-water
-shelter
-single factors ins short supply relative to demand
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Population Demography
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the statistical study of populations (helps predict how population sizes will change in the future)
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Age Structure (Population Demography)
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Cohort (group of organisms, usually born in the same year)
(relative number of individuals in each cohort defines a populations age structure)
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Cohort Characteristics
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-Birth Rate = number of offspring in a standard time
-Death Rate = number of individuals that die in that period
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Sex Ration (Population Demography)
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the proportion of males to females in a population
-number of births is usually directly related to the number of females
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BIO 307: EXAM 2