Population Ecology

R-Strategy

  • r-strategy: species that typically have a relatively short life span; reproduce once and have a large quantity of offspring; observed in unstable environments
  • traits associated with r-strategy:
    • small body size
    • short life spans and generations
    • fast reproduction
    • ability to widely disperse offspring

K-Strategy

  • k-strategy: organisms that can reproduce several times during their lifespan, but the offspring are much slower in reaching maturity; observed in stable environments
  • traits associated with K-strategy
    • larger body size
    • longer life span and generations

Population Sampling

  • population sampling methods
    • random sampling
    • quadrats
    • transect
    • capture-mark-release

Random Sampling:

  • random sampling: finding the distribution of species or comparing distributions in different locations
  • Finding the distribution of species or comparing distributions in different locations
  • Gives a good representation of the population
  • Assumes every organism has an equal chance of being sampled

Capture- Mark - Release:

  • <<capture mark release steps<<
    • <<A large sample of the specimen must be trapped/netted (without causing harm)<<
    • <<The number of captured organisms is counted and recorded<<
    • <<Captured animals are marked (eg. Non-toxic dye, clipping fur)<<
    • <<Animals are returned to the wild and allowed to reintegrate.<<
    • <<A second sample of the specimen is collected from the population after some time.<<
    • <<The numbers of marked and unmarked animals in the new sample are counted and recorded.<<
  • The population size is calculated using the Lincoln Index formula:

Quadrats:

  • quadrant: square made up of wood or metal, placed on the ground; the organisms found in the quadrats are counted
  • <<process of quadrats:<<
    • <<Divide the area that needs to be surveyed into 1m squares and give it quadrants<<
    • <<Use a random # generator to determine which grid squares to use<<
    • <<Count the number of organisms in the selected squares<<
    • <<Average the number found in 1m^2 and multiply by the total number of squares in that survey area!<<

Transects:

  • transect: shows the distribution of species in relation to abiotic factors or changes in communities of organisms across a habitat
  • Systematic rather than random
  • Stretch tape/rope from a fixed point across the changing habitat
  • At intervals (10m, or what is suitable) along the tape, put down a quadrat and count the organisms inside it.
  • Gives a series of samples
  • Measure the abiotic factor of interest at each quadrat location (ie: temperature, salinity, soil pH)
  • <<Process:<<
    • <<Stretch tape/rope from a fixed point across the changing habitat<<
    • <<At intervals (10m, or what is suitable) along the tape, put down a quadrat and count the organisms inside it.<<
    • <<Gives a series of samples<<
    • <<Measure the abiotic factor of interest at each quadrat location (ie: temperature, salinity, soil pH)<<

Biotic Index

  • Found by surveying and sampling organisms present
  • Each species is given a 'sensitive factor' which indicates its ability to tolerate pollution
  • high biotic index = sensitive species = good quality
  • low biotic index = tolerant species = low quality
  • species richness: the number of different species present
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