population dynamics Flashcards
population dynamics
the ways which populations change in abundance overtime
population size changes as a result of four processes
birth
death
immigration
emigration
patterns of population growth
exponential growth
logistic growth
fluctuations
regular cycles
delayed density dependence
delays in the effect that density has on population size
can cause population to fluctuate in size
small populations are at risk of extinction from chance events
genetic (genetic drift)
demographic (stochasticity)
environmental (stochasticity)
genetic drift
chance events influence which alleles are passed onto the next gen
allele freq can change at random from one gen to the next and genetic variation is reduced
demographic stochasticity
chance events affect the survival and reproduction of individuals
environmental stochasticity
change in average birth and death rates from year to year because of random changes in environmental conditions
metapopulations
a set of spatially isolated populations linked by dispersal of individuals or gametes
allele effects
the finding that for some populations there is a positive correlation between population size and growth rate
habitat fragmentation
large tracts of habitat are converted to isolated patches, resulting in metapopulation structures
causes of habitat fragmentation
low densities, individuals have difficult finding mates, so growth rates decrease as population density decreases
responses to fragmentation
isolation by distance can affect chance of extinction, a patch that is near an occupied path may receive immigrants repeatedly
rescue effect
high rates of immigration that protect a population from extinction
bottom up control
increase nutrient inputs caused eutrophication and increased phytoplankton biomass, decreased oxygen, fish die-offs
