population growth

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1 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. - PowerPoint PPT Presentation

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Page 1: Population Growth

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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

Page 2: Population Growth

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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

Page 3: Population Growth

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Population Growth

What factors limit the growth of populations?

BIOL 3240 Plant and Animal Ecology – Population Dynamics

Page 4: Population Growth

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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

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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

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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

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Exponential Population GrowthBIOL 3240 Plant and Animal Ecology – Population Dynamics

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Logistic Population GrowthBIOL 3240 Plant and Animal Ecology – Population Dynamics

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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

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Logistic Population GrowthBIOL 3240 Plant and Animal Ecology – Population Dynamics

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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

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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

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Galapagos Finch Population GrowthBIOL 3240 Plant and Animal Ecology – Population Dynamics

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Which graph on the left indicates growing, declining and stable populations?

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BIOL 3240 Plant and Animal Ecology – Population Dynamics

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BIOL 3240 Plant and Animal Ecology – Population Dynamics

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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

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BIOL 3240 Plant and Animal Ecology – Population Dynamics