Population growth is affected by
births, deaths, immigration, emigration
Immigration
indivisuals move into an area
Emmigration
indivisuals leave an area
Population grow when
births + immigration > deaths + emigration
Exponential Growth
happens when the population has unlimited resources, "ideal conditions"
Individuals reproduce at a constant rate (ex. once per 20 min for some bacteria).
This results in a "J" shaped growth curve.
This type of growth cannot continue indefinitely.
Resources run out, predators catch up, disasters happen, etc.
Logistic Growth
Begins as exponential growth
As resources run out, growth slows/stops
Produces an "S" shaped curve
Number at which growth levels off is the carrying capacity
Could be described as exponential growth after reality has set in
Logistic Growth Equation
Growth Rate (or dN/dt) = rN(K-N/K) t=time N=actual # of organisms r=intrinsic growth rate K=carrying capacity
In the logistic growth equation, the slope of the curve is the steepest when
N=K/2 the # of actual organisms is equal to the carrying capacity divided by two
Predator-Prey Curve
Curves of the predator and prey mirror each other as they have direct impacts of the other population
Limiting Factors
any condition the keeps a population size from increasing
Density-dependent Factors
Affects population more seriously as population density increases
Ex. Competition, predation, parasitism/disease
Density-Independent Factors
Effects not dependent on population density
Ex. Natural disasters, seasonal effects, human habitat destruction WOULD HAPPEN REGARDLESS OF THE POP. DENSITY