POPULATION STUDIES

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POPULATION STUDIES
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Growth of populations
FACTORS INCREASING POPULATION FACTORS DECREASING POPULATION
BIRTH IMMIGRATION DEATH EMIGRATION
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CALCULATING GROWTH RATE OF A POPULATION

• Growth rate
• (birth rate immigration rate) (death rate
  emigration rate)For example
• When the growth rate is gt0 the population is
  increasing
• When the growth rate is lt0 the population is
  decreasing

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Quantifying risk
Which population is at a more significant risk of
displaying a significant decline in population
numbers? Why?
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Distribution
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Measuring Distribution

• A line transect is the best method to use when
  measuring changes along a land surface. Gradual
  changes in environment are referred to as
  environmental gradients

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Measuring Abundance

• There are 3 methods of measuring abundance
• Direct observation
• Quadrat
• Capture mark - recapture

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Direct observation

• Time consuming
• Involves monitoring a particular area either by
  being present on capturing an entire area by
  photograph and counting the individuals present

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Quadrat

• Used to measure density of organisms that do not
  move very much (e.g. plants, some insects, etc) a
  quadrat is an effective method used to make
  predictions on population numbers.
• Quadrats involve the marking out of a square
  area for observation(usually 1m X 1m)
• The following is observed- The number of
  individuals of each species is counted or the
  relative number of each species is estimated
  using a scale from abundant (3) to absent (0)-
  The percentage of cover is estimated
• - The totals of the quadrat are averaged- The
  use of a simple mathematic calculation can give
  the total number or cover for each
  speciesAVERAGE DENSITY OF MEMBER SPECIES
• TOTAL NUMBER OF INDIVIDUALS COUNTED AREA OF
  EACH QUADRAT x NUMBER OF QUADRATS
• This will give you an average of the number of
  individuals found per square meter

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Capture mark - recapture

• Commonly used to measure abundance of mobile
  species.
• Step 1 Capture Animals are caught
  randomlyStep 2 Mark Each captured animal is
  marked then returned to its habitatStep 3
  Recapture Later a random sample is taken and
  the number of marked animals is compared to the
  number or unmarked animals captured. From this
  information a total population can be estimates

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MARK CAPTURE REMARK
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Carrying Capacity

• The Carrying capacity of an ecosystem refers to
  the levels of life sustaining resources an
  environment contains.
• It has been estimated that 100km2 of moist tall
  eucalypt forest is the minimum area possible to
  support 10 000 sugar gliders as a viable
  population.

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POPULATION REGULATION
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POPULATION REGULATION
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OVERVIEW OF POPULATION
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RESTORING / CONTROLLING POPULATIONS

• Student taskPg 331, 331 of Nelson Biology units
  12Write a summary of current methods used to
  control and restore population numbers