MEASURING POPULATIONS 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

GROWTH RATE The amount a population size changes in a given time

GROWTH RATE net reproduction r = birth rate – death rate Growth rate= r = b - d

EXAMPLE of per capita rate In a rat cage containing 400 rats, 100 rats are born and 40 die. P.C. Growth rate= p.c.r = (b – d) / total population p. c. r= #of births - #of deaths total population p.c.r= 100 - 40 = 60 = 0.15 400 400

What the per capita means If the value is +, the population is growing If the value is -, the population is declining You can estimate the next year’s population size EX. .15 x 400 = 60 original population + change = new pop. 60 + 400 = 460 How big would the population be the next generation?

BACK TO MODELS POPULATION GROWTH: # of births is greater than the # of deaths ZERO POPULATION GROWTH: # of births is equal to # of deaths (G = 0)

EXPONENTIAL MODEL: exponential rate increase birth and death rates are constant (b > d) limited by density-independent factors

LOGISTIC MODEL: starts off as b> d levels off as it reaches carrying capacity K This is when b = d rates (zero population growth) limited by density-dependent factors

REGULATING POPULATION SIZE AND GROWTH Carrying Capacity: The population has reached its limit of density dependent factors and achieves zero population 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

Homework Read p 383 – 387 P 389 Problems # 1-5 This math will be on the Test! You may use a calculator but not your cell phone. So Bring a CALCULATOR