population and communties

• Population


  Interacting groups of organisms of the same species living in an area
• Reproductive isolation


  Barrier preventing individuals from reproducing
• Members of a population normally reproduce
• Populations of Zebra and Wildebeest are found in Africa
• Phases of sigmoid population growth

  • Exponential phase
  • Plateau phase
  • Transitional phase
• Rabbits were introduced to Australia in the 1800’s
• Intraspecific relationships


  Interactions between individuals of the same species
• Interspecific relationships


  Interactions between individuals of different species
• Categories of interspecific relationship within communities

  • Herbivory
  • Predation
  • Interspecific competition
  • Mutualism
  • Parasitism
  • Pathogenicity
• Allelopathy


  Chemical inhibition of one species by another
• Top-down control


  Population control from higher trophic levels
• Bottom-up control


  Population control from lower trophic levels
• Exponential Phase


  • Begins with a lag phase
  • Exponential increase in numbers
  • Natality exceeds mortality
  • Low mortality due to abundant resources
• Plateau Phase


  • Carrying capacity is reached
  • Natality equals mortality
  • Population fluctuates around carrying capacity
• Transitional Phase


  • Resources become limited
  • Mortality increases
  • Natality decreases
• Organisms for population growth experiments

  • Yeast
  • Duckweed
• Intraspecific competition


  Competition for resources between members of the same species
• Intraspecific competition increases due to

  • Density dependent factors
• Members of a species compete for

  • Territory
  • Mates
  • Social dominance
• Intraspecific competition - Territory


  • American robins compete for territory
• Intraspecific competition - Mates

  • Male southern elephant seals fight for dominance
• Intraspecific competition - Social Dominance


  • Chimpanzees compete for social position
• Intraspecific cooperation


  Benefits all members of a population
• Examples of intraspecific cooperation


  • Group hunting
  • Group foraging
  • Defence against predators
  • Parenting
• Intraspecific cooperation - Group Hunting


  • Wolves hunt in packs
• Intraspecific cooperation - Foraging


  • Bees cooperate to forage
• Intraspecific cooperation - Defence

  • Meerkats use alarm calls
• Intraspecific cooperation - Parenting

  • Female orangutans teach their young
• A community is formed by populations of different species living and interacting with each other
• Types of interspecific interactions

  • Mutualism
  • Parasitism
  • Pathogenicity
  • Herbivory
  • Predation
  • Interspecific competition
• Herbivory


  The act of eating plants
• Herbivores


  • Red deer
• Predation


  Preying on other animals
• Predators


  • Lions
• Interspecific competition


  Competition between individuals from different species
• Interspecies competition leads to competitive exclusion
• Mutualism


  A close relationship where both individuals benefit
• Mutualism


  • Bees and dandelions
• Parasitism


  One species benefits while the other is harmed
• Parasites


  • Ticks