lecture 22 Flashcards
what term do we use when resources are unlimited
rmax
what is the formula for the exponential model
change in pop over change in time equals rmax times N
when the population changes what stays constant
rmax
more realistic population models limits growth by adding what
carrying capacity
carrying capacity
maximum population size that the environment can support , population stops growing at this point
what is the logistic growth model
exponential model plus carrying capacity term
what is the logistic growth model equation
dN/dt=rmax*N[(k-n)/k] its the exponential growth model but adding k-n over k
when N=0; then (k-N)/k is
1
when N=K; then (k-N)/k is
0, this is when r reaches capacity
in exponential growth the per capita growth rate
doesnt change even if pop gets super large
in logistic growth the per capita growth rate
gets smaller as population gets closer to its max size
what are the assumptions of the logistic model
- no immigration or emigration 2. all individuals contribute equally 3. the environment thus K is constant
what controls population size
biotic factors (parasites, disease, predation, etc) and abiotic factors that dont change based on the pop size and can change carrying capacity size
positive density dependence
rare; when population growth is facilitated by the increased population density
negative density dependence
common; when population growth is curtailed by crowding predators and competition
r strategists
create large numbers of off spring without parental investment (type 3)
why do r strategists occur
they occur in unstable changing environment and reproduce at rates approaching r max
k strategists
few offspring with a lot of parental investment (type 1)
why do k strategists occur
occurs in stable predictable environment and pop densities are often close to k carrying capacity
BD model assumes what
assumes closed populations
BIDE model
accounts for immigrants and emigrants in an open system
metapopulations
they are made up of smaller populations that are linked by occasional movements among them; subpopulations can experience extinction and colonization events
human population is approximated by what model
by the exponential model
what is human population growth thanks to
vaccines, sanitation, and ANTIBIOTICS
the human population is increasing but
the rate of change is decreasing
what is global carrying capacity
- some think maximum k is 9 to 10 billion 2. some think we have reached k because we are using non renewable resources 3. k may decline based on climate and ecosystem degradation
