PPT 1

• Population Ecology

  The ecological study of how biotic and abiotic factors affect the density, dispersion and size of a population
• Population


  A group of individuals that belong in the same species and live in the same area
• Characteristics of a population

  • Genetic make-up
  • Reproductive modes
  • Overall behavior
  • Demographics (population size, density, distribution and age structure)
• Population density


  The number of individuals of a species per unit area or volume
• Mark-recapture


  A sampling technique to estimate wildlife population size: Marking animals, releasing them, then recapturing and counting marked and unmarked individuals
• Population distribution


  The pattern of dispersal of individuals across an area
• Limiting factors


  Environmental aspects that determine where an organism lives
• Dispersion patterns


  • Clumping
  • Uniform
  • Random
• Biotic potential


  The highest possible growth rate of a population when resources are unlimited
• Factors affecting biotic potential

  • Usual number of offspring per reproduction
  • Chances of survival
  • Frequency of reproduction
  • Age at which reproduction begins
• Cohort


  Population members that are the same age and have the same chances of surviving
• Survivorship


  The probability of cohort members surviving to particular ages
• Types of survivorship curves

  • Type I (Convex)
  • Type II (Diagonal)
  • Type III (Concave)
• Age structure diagram


  Divides a population into age groupings: pre-reproductive, reproductive, post-reproductive
• Population growth


  The rate at which the number of individuals in a population changes from one period to the next. It is the number of birth minus number of death
• Population growth


  Birth rate greater than death rate
• Population shrink


  Birth rate less than death rate
• Types of population growth

  • Exponential growth
  • Logistic growth
• Exponential growth


  Continuous population growth throughout the year
• Logistic growth model


  Population growth that is slowed down by limiting factors
• Population limiting factors are environmental factors that restrict population growth
• Clumping - results from an unequal distribution of resources in the

  environment.
• Clumping


  results from an unequal distribution of resources in the

  environment.
• Uniform Pattern


  pattern of dispersion often results from

  interactions among the individuals of a population.
• Random Dispersion


  where individuals in a population are spaced in a

  patternless, unpredictable way. It only occurs without

  strong attractions or repulsions among individuals in

  a population.
• A population's annual growth rate is dependent upon natality, thenumber of Individuals born each year,
• Mortality


  the number of individuals that die each yea
• annual immigration, the number of individuals of a species moving into an existing population,
• Emmigration the number of individuals of a species moving out of an existing population.
• TYPE I OR CORVEX CURVE

  • they survive well past the midpoint of the life span. And death does not come until near the end of the life span.
• TYPE II OR DIAGONAL CURVE

  • survivorship decreases at a constant

  rate throughout the life span.
• TYPE III OR CONCAVE CURVE

  • in which most individuals will probably die very young.
  • example: oysters
• Population Age Categories

  • Pre-reproductive
  • Reproductive
  • Post-reproductive
• Logistic growth occurs in populations that produce a single batch of offspring in a year.
• How do they count individuals?

  • Sampling Technique
  • Indirect Technique
  • Mark Recapture