# population growth

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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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INTRODUCTION

Population GrowthWhat 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 GrowthWhen generations do not overlap, growth can be modeled geometrically.

Nt = Not

Nt = No = (lambda) = t = =2.4BIOL 3240 Plant and Animal Ecology Population Dynamics##Population GrowthWhat factors limit the growth of populations?

BIOL 3240 Plant and Animal Ecology Population Dynamics##Exponential GrowthContinuous population growth in an unlimited environment can be modeled exponentially.

dN / dt = rmax N

dN = dt = rmax = N = Rate of population growthBIOL 3240 Plant and Animal Ecology Population Dynamics##Exponential GrowthdN / dt = rmax N

Appropriate for populations with overlapping generations.As population size (N) increases, rate of population increase (dN/dt) getsWhich variable above would best represent the Intrinsic rate of increase?

BIOL 3240 Plant and Animal Ecology Population Dynamics##Exponential GrowthFor an exponentially growing population, size at any time can be calculated as:

Nt = Noer t

Nt = N0 = e = rmax = t = maxBIOL 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 GrowthAs 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 GrowthEnvironment 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 GrowthdN/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

BIOL 3240 Plant and Animal Ecology Population Dynamics##

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

BIOL 3240 Plant and Animal Ecology Population Dynamics##

BIOL 3240 Plant and Animal Ecology Population Dynamics##

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##

BIOL 3240 Plant and Animal Ecology Population Dynamics##Cactus Finches and Cactus ReproductionGrant and Grant documented several ways finches utilized cacti:Open flower buds in dry season to eat pollenConsume nectar and pollen from mature flowersEat seed coating (aril)Eat seedsEat insects from rotting cactus pads##Cactus Finches and Cactus ReproductionFinches tend to destroy stigmas, thus flowers cannot be fertilized.Wet season activity may reduce seeds available to finches during the dry season.Opuntia helleri main source for cactus finches.Negatively impacted by El Nino (1983).Stigma snapping delayed recovery.Interplay of biotic and abiotic factors.##Galapagos Finch Population GrowthBoag and Grant - Geospiza fortis was numerically dominant finch (1,200).After drought of 1977, population fell to (180).Food plants failed to produce seed crop.1983 - 10x normal rainfall caused population to grow (1,100) due to abundance of seeds and caterpillars.BIOL 3240 Plant and Animal Ecology Population Dynamics##