Population Dynamics:

1
Population Dynamics

• How Populations Change

2
Biotic Potential and Environmental Resistance

• Biotic potential maximum reproductive rate of a
  population under ideal conditions
• Assumes all young live long enough to reproduce
• Populations must have all the resources they need
  to survive
• Factors influencing biotic potential include, but
  are not limited to, the age at which an
  individual is able to reproduce and the number of
  young born at any one time

3

• Examples of biotic potential
• If a pair of houseflies produce one generation
  every two weeks, they could have 391,000,000
  descendents at the end of one year.
• Some bacteria reproduce about every 20 minutes.
  At this rate, 72 generations could be produced in
  24 hours.
• The number of individuals produced would be
  enough to cover the entire surface of the earth
  to a depth of over 20 centimeters!

4
Biotic Potential and Environmental Resistance

• Environmental resistance name given to a
  collection of factors that reduce the growth rate
  of a population
• The advantage of a high biotic potential, such as
  the housefly, is to counteract the effects of
  environmental resistance.

5
Density Dependent Factors

• Definition Factors that influence a population
  differently if the population is crowded than if
  it is not crowded.
• A disease spreads more rapidly through a crowded
  population that through a sparse one.
• A loss of a food source affects a crowded
  population severely since there is less food to
  go around..

6
Density Independent Factors

• Definition Factors that influence all
  populations regardless of their density.
• Forest fires
• Drought
• Lack of sunshine

7
Carrying Capacity

• Definition The number of individuals a
  population in a particular are can support in
  terms of space, food, and shelter.
• Interactions between biotic potential (max.
  reprod. rate) and environmental resistance
  (reduces growth rate) tend to hold most
  populations at a fairly stable level that matches
  the carrying capacity of the area.
• How do humans affect the carrying capacity of an
  area?
• Remove habitats for housing
• Destroy the food in an area
• Change the flow of water in an area