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BIOL 3240 Plant and Animal Ecology – Population Dynamics. Population Growth. What factors limit the growth of populations?. http://www.thewildlifenews.com/2007/10/21/next-years-cheatgrass-is-growing-rapidly-right-now/. BIOL 3240 Plant and Animal Ecology – Population Dynamics.
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BIOL 3240 Plant and Animal Ecology – Population Dynamics Population Growth What factors limit the growth of populations? http://www.thewildlifenews.com/2007/10/21/next-years-cheatgrass-is-growing-rapidly-right-now/
BIOL 3240 Plant and Animal Ecology – Population Dynamics Geometric Growth • When generations do not overlap, growth can be modeled geometrically. Nt= Noλt • Nt = • No = • λ (lambda) = • t = λ =2.4
BIOL 3240 Plant and Animal Ecology – Population Dynamics Population Growth What factors limit the growth of populations?
BIOL 3240 Plant and Animal Ecology – Population Dynamics Exponential Growth • Continuous population growth in an unlimited environment can be modeled exponentially. dN / dt = rmax N • dN = • dt = • rmax= • N = Rate of population growth
BIOL 3240 Plant and Animal Ecology – Population Dynamics Exponential Growth dN / dt = rmax N • Appropriate for populations with overlapping generations. • As population size (N) increases, rate of population increase (dN/dt) gets… • Which variable above would best represent the “Intrinsic rate of increase”?
BIOL 3240 Plant and Animal Ecology – Population Dynamics Exponential Growth • For an exponentially growing population, size at any time can be calculated as: Nt = Noer t • Nt= • N0 = • e = • rmax = • t = max
BIOL 3240 Plant and Animal Ecology – Population Dynamics Exponential Population Growth
BIOL 3240 Plant and Animal Ecology – Population Dynamics Logistic Population Growth
BIOL 3240 Plant and Animal Ecology – Population Dynamics Logistic Population Growth • As resources are depleted, population growth rate slows and eventually stops: _________________ ________. • Sigmoid (S-shaped) _______________________. • _____________________ is the number of individuals of a population the environment can support. • Finite amount of resources can only support a finite number of individuals.
BIOL 3240 Plant and Animal Ecology – Population Dynamics Logistic Population Growth
BIOL 3240 Plant and Animal Ecology – Population Dynamics Limits to Population Growth • Environment limits population growth by altering birth and death rates. • Density-dependent factors?!? • Density-independent factors?!?
BIOL 3240 Plant and Animal Ecology – Population Dynamics Logistic Population Growth dN/dt = rmaxN(1-N/K) • rmax = Maximum per capita rate of increase under ideal conditions. • When N nears K, the right side of the equation… • As population size increases, logistic growth rate becomes… • Highest when N=K/2. • N/K = Environmental resistance.
BIOL 3240 Plant and Animal Ecology – Population Dynamics Galapagos Finch Population Growth
Which graph on the left indicates growing, declining and stable populations?
BIOL 3240 Plant and Animal Ecology – Population Dynamics In the presence of _________ ___________, populations can grow at ___________ or ___________ rates. The environment limits population growth by changing _______ and _______ rates. As resources are depleted, population growth…; this is known as __________ __________ growth.
