# Biology Ch. 5 - Population Ecology

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

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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