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26 Cards in this Set
- Front
- Back
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POPULATION ECOLOGY
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study of how and why number of individuals change over time
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demography
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study of factors that determine size and structure of populations through time
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life tables
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summarizes the probability that an individual will survive and reproduce in any given year over its entire lifetime
-survivorship, and fecundidty |
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survivorship
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-proportion of offspring that survive to a particular age
-3 curves |
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survivorship
TYPE I CURVE |
- humans
- survivorship through life is high and most approach the maximum life span of species |
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survivorship
TYPE II CURVE |
- songbirds
- most individuals experience relatively constant survivorship throughout life |
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survivorship
TYPE III CURVE |
- plants
- high death rates early in life with high survivorship after maturity |
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fecundity
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number of female offspring produced by each female in population
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age-specific fecundity
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average number of female offspring produced by a female in a given age class
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Population growth
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Growth rate = N x r
N→population r→per-capita rate of increase (r = b - d) |
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intrinsic rate of increase, rmax
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when birth rates per individual are as high as possible and deat rates per individual is as low as possible
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exponential population growth
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when r does not change over time
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density independent
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when increase in size of a population does not affect r
- factors are usually abiotic |
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population density
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number of individuals per unit area
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density dependent
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population density gets very high and should decrease r
- factors are usually biotic - density dependent changes in survivorship and fecundity cause logistic population growth |
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Carrying capacity, K
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max number of individuals in a population that can be supported in a a particular habitat over sustained period of time
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logistic growth equation describes logistic population growth
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change in growth rate that occurs as a function of its population size
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population dynamics
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changes in populations through time
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metapopulations
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population of populations
- individuals from a species occupy many small patches of habitat so that they form many independent populations - overall number of individuals stays relatively stable |
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population cycles
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regular fluctuatiions in size
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replacement rate
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each woman producing exactly enough offspring to replace herself and her offspring's father: zero population growth
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population viability analysis
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model that estimates liklihood that a population will avoid extinction for a given time period
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Key Concept
Life tables summarize how likely it is that individuals of each age class in a population will survive and reproduce |
- Basic tool in demography
- resources available to an individual are always limited, so any increase in allocation of resources to survival and competitive ability necessitates decrease in the resources allocated to reproduction |
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Key Concept
THe growth rate of a population can be calculated from life-table data or from direct observation of changes in population size over time |
- exponential growth rate when r doesnt change, but eventually hit carrying capacity resulting in logistic growth
- as population density increases, survivorship and fecundity may decrease → increased death rates and lowered birth rates |
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Key Concept
Wide variety of patterns in population size over time: no growth, regular cycles, continued growth independent of population size |
- density dependent factors drive regular population cycles
- change in age structure can cause change in population size - large amount of juveniles is likely to increase rapidly in size |
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Key Concept
Data from population ecology studies help evaluate prospects for endangered species |
- history of metapopulation driven by birth and death of populations
- migration among habitat patches is essential for stability of a metapopulation - PVAestimates probability that a population will persist for a certain number of years under a prescribed set of demographic and habitat conditions |
