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Chapter 54

Chapter 54 Notes

6 Pages
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Department
Biological Sciences
Course Code
BIOA02H3
Professor
Kamini Persaud

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54: Population Ecology
54.1: How do ecologists study populations?
Population: all the individuals of a species in a given area. At any given moment, an
individual of a certain age and size is in one spot, while the members of the
population are distributed over space and they differ in age and size.
Population structure: age distribution of individuals and how they are spread over
the environment
Population density: individuals/unit area (land) or volume (water)have a strong
influence over how individuals interact
Demographic events: changes in population structure over time due to births, death,
immigration, and emigrationthese events create population dynamics
Demography: study of the events stated above (births, deaths, immigration,
emigration)
Tracking individuals: individuals are often tagged/marked in some way to facilitate
research
oTracking devices: may provide addition physiological and environmental data
oMolecular markers: i.e. hydrogen isotopes have been used to determine where
American redstarts molt during their migrations reflect the latitude at
which the feathers grew because there is a strong latitudinal gradient of
these isotopes in precipitation
Measuring population density: counting every individual in a population is often not
possible. Statistical methods to estimate population size from samples are implied
Population densities can be estimated from samples
Capture, mark, recapture: for sedentary organisms
oCapture a sample of individuals, mark al of them, release them into general
population, capture another small sample
oProportion of marked individuals in the new sample is used to estimated the
population size
om2/n2=n1/Nnumber of marked individuals in 2nd sample/# of individuals in
2nd sample=# of individuals in 1st sample/total population
www.notesolution.com
population densities can be used to estimate rates of demographic events
if these counts are made over many time intervals, we can determine how population
density changes over time
birth and death rates can also be estimated from population density dats
N1=N0+B-D+I-E
oN1= Number of individuals at time 1
oN0=Number of individuals at time 0
oB= Number of individuals born between time 0 and 1
oD= Number of individuals that died between time 0 and 1
oI= Number of individuals that immigrated between 0 and 1
oE= Number of individuals that emigrated between 0 and 1
A useful way to display information about birth and death rates in population is to
construct a life table
A life table is constructed by tracking a group of individuals born at the same time: a
cohort and determining the number that are still alive at later dates (survivorship)
oCan be used to predict future trends
oMortality rate fluctuated year to year because the birds are dependent on
seed production which fluctuates with rainfall
Survivorship curves: the data can be plotted to show survivorship in relation to age
oSurvivorship curves fall into 3 different general patterns
oHigh survivorship whole life until end
oGradual decline
oDrop at beginning, maintained through middle
Age distribution reveals information about recent births and deaths i.e. human
population of the U.S. baby boomers
54.2: How do ecological conditions affect life histories
www.notesolution.com

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Description
54: Population Ecology 54.1: How do ecologists study populations? Population: all the individuals of a species in a given area. At any given moment, an individual of a certain age and size is in one spot, while the members of the population are distributed over space and they differ in age and size. Population structure: age distribution of individuals and how they are spread over the environment Population density: individualsunit area (land) or volume (water)have a strong influence over how individuals interact Demographic events: changes in population structure over time due to births, death, immigration, and emigrationthese events create population dynamics Demography: study of the events stated above (births, deaths, immigration, emigration) Tracking individuals: individuals are often taggedmarked in some way to facilitate research o Tracking devices: may provide addition physiological and environmental data o Molecular markers: i.e. hydrogen isotopes have been used to determine where American redstarts molt during their migrations reflect the latitude at which the feathers grew because there is a strong latitudinal gradient of these isotopes in precipitation Measuring population density: counting every individual in a population is often not possible. Statistical methods to estimate population size from samples are implied Population densities can be estimated from samples Capture, mark, recapture: for sedentary organisms o Capture a sample of individuals, mark al of them, release them into general population, capture another small sample o Proportion of marked individuals in the new sample is used to estimated the population size o m 2n2=n 1Nnumber of marked individuals in 2 sample# of individuals in 2 sample=# of individuals in 1 sampletotal population www.notesolution.com
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