exam 3 ppt 5 Flashcards
equation for population growth
delta N = (b-d) + (i-e)
delta N=
change in population size
b=
births
d=
deaths
i=
movement in (immigration)
e=
movement out (emigration)
equation for per capita growth rate
r = (delta N/delta t) / Nknot (Nknot = initial population size)
t=
time
what is logistic growth like?
may start as exponential, but levels out as growth hits carrying capacity (K)
deltaN / deltat =
(births - deaths)N; can also be rN (where r is the per capita rate or increase)
what is the assumption about r regarding exponential growth?
r is constant over time
what is the assumption about movement of populations regarding exponential growth?
no immigraton or emigration
what is the assumption about resources regarding exponential growth?
resources are unlimited (which resulgs in density independent growth)
is exponential growth density dependent or independent?
density independent
definition of density independent
of people in population doesn’t affect how many others are able to survive
is exponential growth realistic?
not really- there is always a limit to how big a population can be
when can exponential growth be realistic?
1) colonization of a new habitat (no populations there before, with ample resources), 2) recovering after a disaster (no more competition and enough resources, etc)
what happens when resources run out? (reality)
density dependent growth -> logistic growth
when should a population continue to grow regarding logistic growth?
if a population of size N is below the carrying capacity K, then the population should continue to grow
equation for logistic growth
deltaN/deltat = rN(K-N) / K ((K-N) tells how much more pop can grow before hitting c.c.)
if a population in logistic growth is very small, what will (K-N) be like?
if the population is very small, this will be 1 and the growth is pretty much exponential
if a population in logistic growth is very large, what will (K-N) be like?
if a population is large and reaching c.c., this will be about 0 and deltaN/deltat will also be 0
definition of environmental resistance
factors that limit population growth
factors that limit population growth (listed)
density dependent factors, density independent factors
definition of density dependent factors
biotic (living) factors that fluctuate with population size -> leads to logistic growth
definition of density independent factors
are unrelated to population size and are usually abiotic (non-living) factors
exps of density dependent factors
competition for resources, disease/parasitism, predation, social behavior, toxic wastes
what do cyclical populations mean?
their populations fluctuate in response to each other (one increases, the other decreases and vice versa)
exps of density independent factors
natural disasters such as floods, earthquakes, fires
when does exponential growth occur?
when the growth rate r is constant
definition of carrying capacity (K)
the maximum number of individuals that the environment can support; this can change if the environment changes
is logistic growth density dependent?
yes
as a population approaches its c.c., its deltaN / deltat….
decreases (gets closer to zero)
if the major food source of seals decline, what would occur?
the c.c. and seal population would both decrease
does the carrying capacity change based on what resources are available?
yes
is human population growth currently exponential or logistical?
exponential
what do trends show is happening to r in the human population?
trends show r is decreasing (we are currently at about 7.9 billion)
what does age structure tell you?
age structure of a population tells you how many individuals re in an age group
rapid growth age structure means…
broad at bottom- lot of young people, few old people
slow growth age structure means…
growth is more slow vs rapid
stable growth age structure means…
growth is levelling off
exps of countries with rapid growth
guatemala, nigeria, saudi arabia
what is age structure stage 1?
rapid growth
what is age structure stage 2?
slow growth
what is age structure stage 3?
stable
exps of countries with slow growth
united states, australia, canada
what does zero growth mean?
population is not growing in size over time
exps of countries with zero growth
spain, austria, greece
what is negative growth?
population is decreasing in size- having less kids, more old people vs young
exps of countries with negative growth
germany, bulgaria, sweden
in what countries is highest growth occurring?
highest growth is occurring in less economically developed countries
