MODULE 5

• Organism


  Individual form of life
• Species


  Genetically similar organisms that reproduce
• Population


  All members of the same species in a given area
• Biotic community


  An assemblage of populations that function as an integrative unit through coevolved metabolic transformations in a habitat
• Properties of Population


  • Size
  • Density
  • Dispersion
• Population Size


  Total number of individuals in a population
• Population Density


  Number of individuals per unit area or volume
• Dispersion


  Spacing of organisms relative to each other
• Patterns of Dispersion


  • Random
  • Regular
  • Random Clumped
  • Regular Clumped
• Random Dispersion


  • Occurs when environment is very uniform
  • No tendency to aggregate
  • Many factors acting on the population
• Regular Dispersion


  • Uniform dispersion
  • Occurs when competition between individuals is severe
  • Even spacing
  • Few major factors dominating
• Clumped Dispersion


  • Most common pattern
  • Strong tendency for organisms to aggregate
  • Individuals form groups of a certain size
• Random Clumped Dispersion


  • Clumped in a random pattern
• Regular Clumped Dispersion


  • Clumped in a regular pattern with large unoccupied spaces
• Lincoln Index


  Capturing and marking some fraction of the total population and using this fraction to estimate total population density
• Assumptions for Lincoln Index validity

  • Marking technique has no negative effect on mortality
  • Marked individuals released at original capture site and allowed to mix naturally
  • Marking does not affect probability of recapture
  • Marks not lost or overlooked
  • No significant immigration/emigration
  • No significant mortality/natality in interval
• Minimum Known Alive


  Mark-recapture method using total number of individuals observed over a period
• Other Methods for Estimating Population Density

  • Total counts
  • Quadrat or transect sampling
  • Removal sampling
  • Plotless method
  • Importance percentage value
• The ratio of marked to unmarked individuals allows scientists to calculate total population size
• The larger the population, the lower the percentage of tagged organisms that will be recaptured
• Natality


  Number of individuals added to the population through reproduction
• Mortality


  Rate at which individuals are lost by death
• Immigration


  Movement of individuals into a population
• Emigration


  Movement of individuals out of a population
• Types of Natality


  • Maximum natality
  • Ecological natality
• Ecological Mortality


  Loss of individuals under a given environmental condition
• Minimum Mortality


  Minimum loss under ideal or non-limiting conditions
• Sex Ratio


  Relative numbers of males and females
• Sex ratio


  The relative numbers of males and females
• Minimum mortality


  Minimum loss under ideal of non-limiting conditions
• In many social insects (bees, ants, and wasps), the number of females greatly exceeds the number of males at all times, though most of the females are sterile
• Rapidly expanding population


  Contains a large portion of young pulsing
• Stable population


  Contains an even distribution of age classes
• Declining population


  Contains a large proportion of old individuals
• In the zooplankton Moina macrocopa, the population consists of neonates, juveniles, adult parthenogenetic females, and gravid females
• Exponential growth


  Populations can only grow until they reach their biotic potential, the rate that populations could increase at ideal conditions, meeting conditions of no immigration/emigration, unlimited resources, no predation/parasitism/competition
• Logistic growth


  Populations can only grow until they reach their carrying capacity, the maximum population size that can be supported by the available resources
• 1. shaped growth curve


  A graph representing exponential population growth that then stops abruptly as environmental resistance or other factors become effective
• 1. shaped growth curve


  A graph representing exponential population growth followed by a gradual leveling off of the population size as environmental resistance becomes proportionately more important
• Density-dependent factors limit population growth through resource limitations triggered by increasing population density