Ecology: Patterns of Population Growth Flashcards
Population size is affected by 4 factors
Natality, mortality, emigration, immigration
Density
of individuals per unit area/volume
Density is measured by
Total counts and sub-sampling methods
Patterns of dispersion
Clumped- discrete groupsUniform- minimum distance between indvRandom
Type 1 age structure and what does the curve look like?
HumanQuarter circle downward hitting 0
Type 2 age structure
BirdsLinear line downwards
Type 3
Plants and fishDownward invert of humans
All populations have the potential for exponential growth
False
Requirements for exponential growth
Unlimited resources
For a very short time some populations may grow at rates close to the intrinsic (max) growth rate
True
Population dynamics
How population sizes change over time
No natural populations can maintain exponential growth indefinitely
True
Population density typically fluctuates around a constant # of individuals
True
As population size increases, resources become limiting for growth and population
True
In the population equations, logistic growth adds what variable?
K (carrying capacity)
Carrying capacity is
The maximum population size an environment can support
Population growth slows as density approaches what?
Carrying capacity
When pop size is below (K) growth
Increases
When pop size is near (K) growth
Decreases
Logistic model fits well with what size organism?
Small
Do populations stabilize at (K)?
Most don’t
Logistic predictions are correct when
Environment is constantNo predatorsNo competition
3 assumptions that make logistic growth not fit well
Each individual added has a negative effect on population growth
The logistic curve is ____ shaped
S
In density dependent curves the #killed is a ______ curve and the % mortality is a ________ curve
ExponentialIncreasing linear
Density dependent examples
Predation, disease, competition
In density-independent graphs the #killed is a _________ and the %mortality is a ______
Inclining linear curveHorizontal line
Density-independent factors are
Abiotic
Natural populations are a mix of density-dependent and independent factors
True
Due to density-dependent control, over long time scales populations _______________ to (K)
Remain stable/close
Short time fluctuations are due to
Density-independent factors
Stable equilibrium means
Birth=deathIf disturbed it will go back to normalDensity-dependent control
Unstable population
May never return to normalInverse density dependence with log time lags
Metapopulation
A population thats divided into discrete sub-populations
What connects sub-populations in a metapopulation?
Emmigration and immigration
Dynamics of metapopulations
Growth in patches, migration and colonization
Migration increase dampens what in metapopulations? Decrease does what?
Local population fluctuationEnhances local population fluctuation
A medium rate of migration causes
A shifting “mosaic” of occupied and unoccupied patches (persistence)
If immigration rate is high an extinction rate low, then
The fraction of occupied sites will increase with time, and vice versa
