3. Population Ecology (Unregulated & Regulated Populations Growth)

N₁ = N₀R₀

geometric growth

(pic)

finite growth rate

zero population growth occurs when

the birth rate equals the death rate

N is:

population size

t is:

time

r is:

per capita rate of increase

= birth - death

N_t = N₀e^rt

lnN_t = lnN₀ + rt

(lnN_t - lnN₀) / (t) = r

R₀=e^rT; r=ln(R₀)/T per generation growth rate

r < 0, population is decreasing

r = 0, population is stable

r > 0, population is increasing

exponential population growth

is population increase under idealized conditions

equation of exponential growth is:

(dN) / (dt) = r_maxNp

population growing exponentially exhibit characteristics:

• positive feedback of population size on population hrowth; larger populations grow faster than do smaller populations

• per capita population growth is constant

what is (K)

Carrying Capacity = the maximum population size the environment can support

populations growing logistically also exhibit the following characteristics:

• negative feedback of population size on population growth; unimodal response for population growth rate vs. population size

  • per capita population growth declines with increasing population size

density-independent populations

birth rate and death rate do not change with population density

density-dependent populations

birth rates fall and death rates rise with population density

• negative feedback

territoriality

defense of a defined geographical area,

• ex. cheetahs are highly territorial, using chemical communication, to warn other cheetahs of their boundaries

predation

as a prey population build up, predators may feed preferentially on that species

toxic waste

accumulation of toxic waste can contribute to density-dependent regulation of population size

intrinsic factors

for some populations, (physiological) appear to regulate population size