11 population growth what factors limit the growth of populations?
TRANSCRIPT
11
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
22
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
33
Population Growth
What factors limit the growth of populations?
BIOL 3240 Plant and Animal Ecology – Population Dynamics
44
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
55
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
66
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
77
Exponential Population GrowthBIOL 3240 Plant and Animal Ecology – Population Dynamics
88
Logistic Population GrowthBIOL 3240 Plant and Animal Ecology – Population Dynamics
99
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
1010
Logistic Population GrowthBIOL 3240 Plant and Animal Ecology – Population Dynamics
1111
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
1212
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
1313
Galapagos Finch Population GrowthBIOL 3240 Plant and Animal Ecology – Population Dynamics
1414
Which graph on the left indicates growing, declining and stable populations?
1515
BIOL 3240 Plant and Animal Ecology – Population Dynamics
1616
BIOL 3240 Plant and Animal Ecology – Population Dynamics
1717
In the presence of _________ ___________, populations can grow at ___________ or ___________ rates.
As resources are depleted, population growth…
; this is known as __________ __________ growth.
The environment limits population growth by changing _______ and _______ rates.
BIOL 3240 Plant and Animal Ecology – Population Dynamics
1818
BIOL 3240 Plant and Animal Ecology – Population Dynamics