Topic 11- Population Growth Flashcards
what is population growth?
the change in total number of individuals within a population. (B-D)/∆t
what is the per capita birth rate?
b=B/N number of births relative to the population
what is per captia death rate?
d=D/N number of deaths relative to the population
what is the per capita growth rate?
r=b-d the rate of growth of the population relative to per capita growth and death rates
what is the exponential model of population growth?
under ideal conditons:
-per capita growth rate will be at a maximum for the population (rmax= intrinsic rate of increase)
-rmax is always positive and constant
-rmax varies by species
how do you calculate exponential growth?
N(t) = N0 (1 + rmax)^t
the population at time (t) is equal to the population at time 0 multiplied by (1 + rmax) to the power of time (t)
what limits population growth?
predators, disease, limited food, limited shelter, precipitation, temperature.
what is the relationship between population size (N), carrying capacity (K) and per capita growth rate (r)?
when N<K>K r is negative
as N increases r decreases</K>
what is the logistic model of population growth?
populations per capita growth rate decreases as population reaches carrying capacity.
what is the formula for logistic population growth?
N(t+1)= N(t) (1 + r(t))
r(t)= rmax ((k-N(t))/K)
what are the density dependent factors that affect population growth?
Biotic factors:
food availability, shelter, mates, disease, predation
have an increased effect as population increases.
what do density dependent factors influence?
reproduction- as density increases, reproduction decreases
growth rate- as density increase growth rate slows and reaches less mean body mass
adult size- as density increases, performance and availability of resources decreases so adult size decreases
survival rate- as density increases, survival rate decreases
what are the density independent factors that affect population growth?
Abiotic factors:
temperature, precipitation, distrubances sich as floods, forest fires
have an affect at any population size
how do life history traits influence population growth?
r-selective species: dont grow far enough to reach carrying capacity, growth looks exponential, grow very fast, often have a small size
k-selective species: highly competitive, slow growth rates, live close to carrying capacity, can survive extremes
in the exponential growth model when does the population reach a maximum?
exponential growth curve never reaches a maximum
