negative density dependence
causes of negative density dependence
carrying capacity
positive density dependence
at low numbers, positive density dependence is called…
the Allee effect
Allee effect
arise via small-population breakdowns in mating behaviors or the ability to find mates
biological mechanisms of the Allee effect
many of the famous Allee effects arise via small-population breakdowns in mating behaviors or the ability to find mates, or in the ability to collectively make necessary habitat modification or engage in successful cooperative feeding
biological mechanisms of the Allee effect : mating and caring for young
biological mechanisms of the Allee effect : foraging advantages
biological mechanisms of the Allee effect : predator-method
genetic variation
the difference in the genetic makeup (DNA) of individuals or populations among the same species
why is genetic variation improtant?
important for survival and adaptation of a species as it helps in terms of natural selection and evolution
effective population size (Ne)
the number of individuals that effectively participates in producing the next generation
which is smaller, census size or effective size of a population?
effective size of a population
small Ne
bigger increase in genetic drift
when is Ne highest?
at equal breeding sex ratio
genetic drift
change in allele frequencies by chance
what does genetic drift cause?
a loss of genetic diversity
where is genetic drift most common?
in small populations
what does a population bottle neck lead to?
genetic drift
when does genetic drift occur?
occurs when an event drastically reduces population size
how to measure genetic drift?
gene flow
the movement of alleles between populations
when does gene flow occur?
occurs when individuals join new populations and reproduce