GROWTH MODELS pp. 383-387

birth rate: # of births occurring in a given amount of time death rate: # of deaths occurring in a given amount of time Population growth: # of births is greater than the # of deaths Zero population growth: # of births is equal to # of deaths

REGULATING POPULATION SIZE AND GROWTH Limiting factors: restrains population growth Density-independent factors: no regard for population density EX. Weather, seasons, natural disasters Density-dependent factors: increase or become more prominent when the population density increases EX. predation, pollution, food shortage

EXPONENTIAL MODEL

EXPONENTIAL MODEL: Increase on the y axis (population size) much faster than on the x axis (time) The larger the population, the faster it grows birth and death rates are constant (b > d) limited by density-independent factors

LOGISTIC MODEL

Starts off exponential (b> d) Levels off as it reaches carrying capacity (K = maximum number of individuals an environment can sustain) This is when b = d rates (zero population growth) Limited by density-dependent factors