5.1 & 5.2 - Pop. Growth

• • Population: a group of organisms of the same species that live in the same area at the same time
• • There are four factors that determine if a pop. grows: natality, mortality, immigration, and emigration
• • Factors that increase pop.
  • Natality: new organisms are born
  • Immigration: organisms move into a pop.
• Factors that decrease a pop.

  • Mortality: organisms die
  • Emigration: organisms move out of a pop.
• • There are two types of population growth patterns: exponential growth and logistic growth
• Exponential Growth = J-shaped curve

  • If a population has abundant resources, then the pop. will increase at a constant rate
  • Occurs under ideal conditions with unlimited resources
  • No limiting factors
  • factors that slow growth
• Logistic Growth = S-shaped curve

  • Exponential Growth can't continue forever
  • In LG, as resources become less available, the population growth slows or stops
• Carrying capacity: the greatest number of individuals that can live in an area as determined by the available resources

  • Pop. growth slows/stops (LG) when the number of organisms reaches the carrying capacity
  • If pop. numbers exceed its carrying capacity, organisms use up their resources
  • This can lead to a drastic reduction in the pop. due to death or emigration
• Limiting Factors

  • Ex: food and water supply, competition, predators, pollution, and disease
  • The balance of these factors may cause organisms to move or die to keep the population from getting too big
  • There are two types of limiting factors: density dependent and density independent
• Density dependent limiting factors: factors that become more limiting when the populations get bigger and more dense

  • water, food, disease, predators
• Density independent limiting factors: factors that affect crowded and uncrowded populations in the same way

  • natural disaster, fire, weather, human activity (clear cutting forest)