AB

3.3 Population Growth and Resources Availability

No population can grow in definitely due to limiting factors such as…

  • light
  • water
  • space
  • competition
  • predation
  • disease

^^INTRINSIC RATE OF INCREASE (r):^^ Rate of population growth with unlimited resources

4 CHARACTERISTICS OF RAPIDLY GROWING POPULATIONS

  1. timing of reproduction
  2. amount of time between generations
  3. length of reproductive lives
  4. \ # of offspring (fecundity)
    • many offsprings= high fecundity

CARRYING CAPACITY (K)

  • Determined by ^^biotic potential^^ = maximum reproductive rate of a population in ideal conditions (capacity for growth) and ^^environmental resistance^^ (factors that limit growth)
  • As population reaches carrying capacity, growth rate decreases because resources become more scarce, among other factors

Types of Curves

S-Curve: Logistic (restricted) Growth J-Curve: Exponential (un-restricted) Growth

Exponential Growth Equation

Density Dependent Factors

  • will change their intensity depending on the density of the population
    • ex: competition, diseases, predation, parasitism

Density Independent Factors

  • will have the same intensity depending on the density of the population
    • Natural: Floods, hurricanes, fire
    • Anthropogenic: Pollution, habitat destruction

4 TYPES OF POPULATION FLUCTUATIONS

  1. Stable

    1. fluctuates slightly above and below carrying capacity

    2. Tropical Rainforest

      1. temps/rainfall stay steady

  2. Irrupt

    1. Usually stable, but sometimes explodes and then crashes

    2. Algae, insects

      1. due to seasonal changes, nutrient availability

  3. Cyclic

    1. Rise and fall in predictable pattern
    2. predator/prey

  4. Irregular

    1. no reoccurring pattern