Biology Ch. 5 - Population Ecology

11/9/22 - 12/1/2 Mr. Sandro

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

1. happens when the population has unlimited resources, "ideal conditions"
2. Individuals reproduce at a constant rate (ex. once per 20 min for some bacteria).
3. This results in a "J" shaped growth curve.
4. This type of growth cannot continue indefinitely.
5. Resources run out, predators catch up, disasters happen, etc.

Logistic Growth

1. Begins as exponential growth
2. As resources run out, growth slows/stops
3. Produces an "S" shaped curve
4. Number at which growth levels off is the carrying capacity
5. 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

1. Affects population more seriously as population density increases
2. Ex. Competition, predation, parasitism/disease

Density-Independent Factors

1. Effects not dependent on population density
2. Ex. Natural disasters, seasonal effects, human habitat destruction
WOULD HAPPEN REGARDLESS OF THE POP. DENSITY