ch45 lecture(Pop Eco)Sans photos

8/14/2019 ch45 lecture(Pop Eco)Sans photos

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Population EcologyPopulation Ecology


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Population EcologyPopulation Ecology

Certain ecological principles govern theCertain ecological principles govern the

growth and sustainability of allgrowth and sustainability of all

populations--including humanpopulations--including human

populationspopulations


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Ecological Principles Apply to AllEcological Principles Apply to All

SpeciesSpecies

Humans, Palms, Crabs, Seagulls, algae, etc.


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Limits to GrowthLimits to Growth

A populations growth depends onA populations growth depends on

the resources of its environmentthe resources of its environment

Deer introduced to Angel IslandDeer introduced to Angel Island

Population outstripped resourcesPopulation outstripped resources


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Angel IslandAngel Island


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Angel Island 1Angel Island 1

A. Angel Island is a game reserve in SanA. Angel Island is a game reserve in SanFrancisco Bay near SausalitoFrancisco Bay near Sausalito

B. In the early 1900's well-meaning natureB. In the early 1900's well-meaning naturelovers introduced deer to the islandlovers introduced deer to the island

C. With no natural predators to controlC. With no natural predators to controlthem the population quickly rose to a levelthem the population quickly rose to a levelmuch higher than the island could supportmuch higher than the island could support

D. Well meaning people brought food toD. Well meaning people brought food to

the island to feed the deer, causing thethe island to feed the deer, causing thepopulation to further increasepopulation to further increase


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Angel Island 2Angel Island 2

E. Eventually the population grew toE. Eventually the population grew to

over 300, much too large for theover 300, much too large for the

island to supportisland to support

F. As the deer began to starve theyF. As the deer began to starve they

ate most of the native vegetation.ate most of the native vegetation.

Without vegetation the soil startedWithout vegetation the soil started

washing away and the islandwashing away and the islandenvironment rapidly deterioratedenvironment rapidly deteriorated


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Angel Island - 3Angel Island - 3

G. It was proposed that hunters kill someG. It was proposed that hunters kill some

of the deer and/or that coyotes, the deersof the deer and/or that coyotes, the deers

natural predators, be introduced to thenatural predators, be introduced to the

island. However many people objectedisland. However many people objectedbecause they viewed both alternatives asbecause they viewed both alternatives as

cruelcruel

H. Eventually two thirds of the populationH. Eventually two thirds of the population

was rounded up and moved to thewas rounded up and moved to themainland, at a cost of $3,000 per deermainland, at a cost of $3,000 per deer


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I. However, tracking studies revealed thatI. However, tracking studies revealed thatthe majority of the deer moved to thethe majority of the deer moved to themainland were killed by cars, dogs,mainland were killed by cars, dogs,coyotes and hunters within 60 dayscoyotes and hunters within 60 days

J. The story of Angel Island illustrates aJ. The story of Angel Island illustrates abasic ecological principle: a population'sbasic ecological principle: a population's

growth is dependent on the resources ofgrowth is dependent on the resources ofits environment. Human intervention couldits environment. Human intervention couldonly postpone, not prevent the inevitableonly postpone, not prevent the inevitable


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K. Many environmental problems are simply theK. Many environmental problems are simply theresult of a lack of understanding of basicresult of a lack of understanding of basicecological principles by politicians, lawyers,ecological principles by politicians, lawyers,economists, the general public and even welleconomists, the general public and even well

intentioned "environmentalists". Humanintentioned "environmentalists". Humanignorance of simple ecological principles oftenignorance of simple ecological principles oftenleads to disastrous resultsleads to disastrous results

From:From:http://arnica.csustan.edu/boty1050/Ecology/ecolhttp://arnica.csustan.edu/boty1050/Ecology/ecology.htmogy.htm


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Human Population ProblemsHuman Population Problems

Over 6 billion people aliveOver 6 billion people alive

About 2 billion live in povertyAbout 2 billion live in poverty

Most resources are consumed by theMost resources are consumed by the

relatively few people in developedrelatively few people in developed

countriescountries


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Population GrowthPopulation Growth

For most of human history, humansFor most of human history, humans

have not been very numeroushave not been very numerous

compared to other species.compared to other species.

It took all of human history to reach 1It took all of human history to reach 1

billion.billion.

150 years to reach 3 billion.150 years to reach 3 billion.

12 years to go from 5 to 6 billion.12 years to go from 5 to 6 billion.Human population tripled during theHuman population tripled during the

twentieth century.twentieth century.


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Human Population HistoryHuman Population History


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U.S. POPClock ProjectionU.S. POPClock Projection

According to the U.S. Bureau of the Census, theAccording to the U.S. Bureau of the Census, theresident population of the United States,resident population of the United States,projected to 03/21/05 at 17:04 GMT (EST+5) isprojected to 03/21/05 at 17:04 GMT (EST+5) is

295,707,750295,707,750

COMPONENT SETTINGSCOMPONENT SETTINGS One birth every.................................. 7One birth every.................................. 7

seconds One death every..................................seconds One death every..................................11 seconds One international migrant (net)11 seconds One international migrant (net)

every............ 24 seconds Net gain of one personevery............ 24 seconds Net gain of one personevery..................... 12 secondsevery..................... 12 seconds


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PopulationPopulation

A group of individuals of the same speciesA group of individuals of the same species

occupying a given area during a particularoccupying a given area during a particularperiod of timeperiod of time

Can be described by demographicsCan be described by demographics

Vital statistics such as size, density,Vital statistics such as size, density,

distribution, and age structuredistribution, and age structure


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Population Age StructurePopulation Age Structure

Divide population into ageDivide population into age

categoriescategories

Populations reproductive basePopulations reproductive base

includes members of theincludes members of the

reproductive and pre-reproductivereproductive and pre-reproductive

a e cate oriesa e cate ories


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Population Age Structure DiagramPopulation Age Structure Diagram


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Question 1Question 1

1. How did the community respond to1. How did the community respond to

the Angel Island deer problem?the Angel Island deer problem?


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Answer 1Answer 1

1.1. How did the community respond toHow did the community respond to

the Angel Island deer problem?the Angel Island deer problem?

The community demanded thatThe community demanded that

the deer be moved to thethe deer be moved to the

mainland, rather than be killedmainland, rather than be killed

by hunters.by hunters.


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2. Ultimately what happen to most of2. Ultimately what happen to most of

the deer?the deer?


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Answer 2Answer 2

2. Ultimately what happen to most of2. Ultimately what happen to most of

the deer?the deer?

They died from car impacts, dogs,They died from car impacts, dogs,

coyotes, and hunters.coyotes, and hunters.


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3. What is there to be learned from3. What is there to be learned from

the Angel Island experience?the Angel Island experience?


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Answer 3Answer 3

3. What is there to be learned from3. What is there to be learned from

the Angel Island experience?the Angel Island experience?

Answers will vary.. But many willAnswers will vary.. But many will

include an element ofinclude an element of

unexpected consequences.unexpected consequences.


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4. Define the term,4. Define the term,populationpopulation..


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Answer 4Answer 4

4. Define the term,4. Define the term,populationpopulation..

A group of individuals of the sameA group of individuals of the samespecies occupying a given area duringspecies occupying a given area during

a particular period of time.a particular period of time.


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5. What is a5. What is apopulation agepopulation age

structure diagramstructure diagram??


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Answer 5Answer 5

5. What is a5. What is apopulation agepopulation age

structure diagramstructure diagram??

A demographic analytic method that dividesA demographic analytic method that dividesa population into age categories (often bya population into age categories (often by

gender) and displays it as a graph.gender) and displays it as a graph.


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6. A populations ______ _____6. A populations ______ _____

includes members of theincludes members of the


age categories.age categories.


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Answer 6Answer 6

6. A populations6. A populations reproductivereproductivebasebaseincludes members of theincludes members of the


age categories.age categories.


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Density & DistributionDensity & Distribution

Number ofNumber of

individuals in someindividuals in some

specified area ofspecified area of

habitathabitat Crude densityCrude density

information is moreinformation is more

useful if combineduseful if combinedwith distributionwith distribution

datadata

clumped

nearly uniform

randomFigure 45.2

Page 808


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Clumped DistributionClumped Distribution


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Determining Population SizeDetermining Population Size

Direct counts are most accurate butDirect counts are most accurate but

seldom feasibleseldom feasible

Can sample an area, then extrapolateCan sample an area, then extrapolate

Capture-recapture method is used forCapture-recapture method is used for

mobile speciesmobile species


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Population EstimatePopulation Estimate

How could you determine theHow could you determine the

population size of the students inpopulation size of the students in

Robinson Hall?Robinson Hall?

The number of revelers on the beach?The number of revelers on the beach?


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Does Time and Place Make aDoes Time and Place Make a

Difference?Difference?

Daytona Beach

Hilton Head


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Capture-Recapture MethodCapture-Recapture Method

Capture, mark, and releaseCapture, mark, and release

individualsindividuals

Return later and capture secondReturn later and capture second

samplesample

Count the number of markedCount the number of marked

individuals and use this toindividuals and use this to

estimate total populationestimate total population


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Example:Example:

Capture - RecaptureCapture - Recapture In 1970, naturalists wanted to estimateIn 1970, naturalists wanted to estimate

the number of pickerel fish in Dryden Lakethe number of pickerel fish in Dryden Lake

in central New York State. Theyin central New York State. They capturedcaptured

232 pickerel232 pickerel, put a mark on their fins,, put a mark on their fins,and returned the fish to the lake. Severaland returned the fish to the lake. Several

weeks later, anotherweeks later, anothersample of 329sample of 329

pickerelpickerelfish were captured. Of thisfish were captured. Of this

second sample,second sample, 16 had marks on their16 had marks on theirfins.fins. (Chaterjee in Mosteller et al.(Chaterjee in Mosteller et al.

Statistics by Example: Finding ModelsStatistics by Example: Finding Models).).


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Chain PickerelChain Pickerel


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How Many Pickerel Were in theHow Many Pickerel Were in the

Lake?Lake? N = total number of pickerel in lakeN = total number of pickerel in lake

NM = total number of marked pickerelNM = total number of marked pickerel

(232)(232)

RC = Number of recaptured pickerel (16)RC = Number of recaptured pickerel (16) NS = number of fish in sample (329)NS = number of fish in sample (329)

NM/N = RC/NSNM/N = RC/NS N = (NM x NS)/RCN = (NM x NS)/RC


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SolutionSolution

N = (232 x 329)/16N = (232 x 329)/16

N = 4770N = 4770 pickerel in the lakepickerel in the lake(estimate)(estimate)

This is an example of how theThis is an example of how theCapture/Recapture method works.Capture/Recapture method works.


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AssumptionsAssumptions

The sampling is randomThe sampling is random The marked organisms will not be harmedThe marked organisms will not be harmed

by the capture and markingsby the capture and markings

The marked organisms will not avoidThe marked organisms will not avoidrecapturerecapture The samples are statistically large enoughThe samples are statistically large enough

to avoid problems with sampling errorto avoid problems with sampling error

No significant emigration/immigrationNo significant emigration/immigrationoccursoccurs

The sampling is done promptlyThe sampling is done promptly


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7. Define7. Define crude population densitycrude population density..


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Answer 7Answer 7

7. Define7. Define crude population densitycrude population density..

The number of individuals inThe number of individuals insome specified area of habitat.some specified area of habitat.

It does not take intoIt does not take into

consideration the distribution ofconsideration the distribution of

organisms.organisms.


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8. What are two distribution patterns8. What are two distribution patterns

(there are three)?(there are three)?


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Answer 8Answer 8

8. What are two distribution patterns8. What are two distribution patterns

(there are three)?(there are three)?

ClumpedClumped

RandomRandom

UniformUniform(Any two will do.)(Any two will do.)


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9. State two methods of determining9. State two methods of determining

population size (there are three).population size (there are three).


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Answer 9Answer 9

9. State9. State twotwo methods of determiningmethods of determining

population size (there are three).population size (there are three).

Direct countsDirect counts

Can sample an area, then extrapolateCan sample an area, then extrapolate

Capture-recapture methodCapture-recapture method


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Changes in Population SizeChanges in Population Size

Immigration adds individualsImmigration adds individuals

Emigration subtracts individualsEmigration subtracts individuals

Births add individualsBirths add individuals

Deaths subtract individualsDeaths subtract individuals


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Zero Population GrowthZero Population Growth

Interval in which number of birthsInterval in which number of births

is balanced by number of deathsis balanced by number of deaths

Assume no change as a result ofAssume no change as a result of

migrationmigration

Population size remains stablePopulation size remains stable


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Per Capita RatesPer Capita Rates

Rates per individualRates per individual

Total number of events in a timeTotal number of events in a time

interval divided by the number ofinterval divided by the number of

individualsindividuals

Per capita birth rate per month =Per capita birth rate per month =Number of births per monthNumber of births per month

Population sizePopulation size


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rr

Net reproduction per individual perNet reproduction per individual per

unit time (Intrinsic rate of naturalunit time (Intrinsic rate of natural

increase) a constant the units areincrease) a constant the units are

inverse timeinverse time

Variable combines per capita birthVariable combines per capita birthand death rates (assuming bothand death rates (assuming both

constant)constant)

Can be used to calculate rate ofCan be used to calculate rate of


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Exponential Growth EquationExponential Growth Equation

GG == rNrN

GG is population growth per unit timeis population growth per unit time rris net reproduction per individualis net reproduction per individual

per unit timeper unit time

NNis population sizeis population size


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Exponential GrowthExponential Growth

Population sizePopulation size

expands by everexpands by ever

increasingincreasing

increments duringincrements duringsuccessive intervalssuccessive intervals

The larger theThe larger the

population gets, thepopulation gets, themore individualsmore individuals

there are tothere are to

reproducereproduceFigure 45.4Page 810

( ) St t i( ) St t i


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(r) Strategies(r) Strategies

Short lifeShort life Rapid growthRapid growth Early maturityEarly maturity Many small offspring.Many small offspring. Little parental care.Little parental care.

Little investment in individual offspring.Little investment in individual offspring.

Adapted to unstable environment.Adapted to unstable environment. Pioneers, colonizersPioneers, colonizers Niche generalistsNiche generalists

PreyPrey Regulated mainly by extrinsic factors.Regulated mainly by extrinsic factors. Low trophic level.Low trophic level.


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Weedy Species r StrategistsWeedy Species r Strategists

Opportunistic Species - Quickly appear when opportunitiesOpportunistic Species - Quickly appear when opportunities

arise.arise.

Many weeds.Many weeds.

Pioneer Species - Can quickly colonize open, disturbed, orPioneer Species - Can quickly colonize open, disturbed, or

bare ground.bare ground.


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Effect of DeathsEffect of Deaths

Population grows exponentially as long as perPopulation grows exponentially as long as per

capita death rates are lower than per capitacapita death rates are lower than per capita

birth ratesbirth rates

25% mortality

between divisions

Figure 45.5Page 811


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10. What are two rates that10. What are two rates that increaseincreasepopulation size?population size?


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Answer 10Answer 10

10. What are two rates that10. What are two rates that increaseincreasepopulation size?population size?

Birth rateBirth rate

Immigration rateImmigration rate


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11. When is a zero population rate11. When is a zero population rate

attained?attained?


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Answer 11Answer 11

11. When is a zero population rate11. When is a zero population rate

attained?attained?

When: births + immigration = deaths + emigrationWhen: births + immigration = deaths + emigration


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12. State the12. State the Exponential GrowthExponential Growth

Equation.Equation.


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Answer 12Answer 12

12. State the12. State the Exponential GrowthExponential Growth

Equation.Equation.

GG== rNrN


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13. Given13. Given G = rNG = rN, what do the, what do the

symbols represent?symbols represent?


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Answer 13Answer 13

13. Given13. Given G = rNG = rN, what do the, what do thesymbols represent?symbols represent?

G is population growth per unitG is population growth per unittimetime

r is net reproduction perr is net reproduction perindividual per unit timeindividual per unit time

N is population sizeN is population size


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14. What type of organisms are r14. What type of organisms are r

strategists?strategists?


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Answer 14Answer 14

14. What type of organisms are r14. What type of organisms are r

strategists?strategists?

Weedy species and pioneerWeedy species and pioneer

speciesspecies


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15. State three characteristics of r15. State three characteristics of r

strategists.strategists.


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Answer 15Answer 15

15. State three characteristics of r strategists.15. State three characteristics of r strategists. Short lifeShort life Rapid growthRapid growth Early maturityEarly maturity Many small offspring.Many small offspring.

Little parental care.Little parental care. Little investment in individual offspring.Little investment in individual offspring.

Adapted to unstable environment.Adapted to unstable environment. Pioneers, colonizersPioneers, colonizers

Niche generalistsNiche generalists PreyPrey Regulated mainly by extrinsic factors.Regulated mainly by extrinsic factors. Low trophic level.Low trophic level.


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Biotic PotentialBiotic Potential

Maximum rate of increase perMaximum rate of increase per

individual under ideal conditionsindividual under ideal conditions

Varies between speciesVaries between species

In nature, biotic potential is rarelyIn nature, biotic potential is rarely

reachedreached


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Limiting FactorsLimiting Factors

Any essential resource that is inAny essential resource that is in

short supplyshort supply

All limiting factors acting on aAll limiting factors acting on a

population dictate sustainablepopulation dictate sustainable

population sizepopulation size


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Carrying Capacity (Carrying Capacity (KK))

Maximum number of individuals thatMaximum number of individuals that

can be sustained in a particularcan be sustained in a particular

habitathabitat

Logistic growth occurs whenLogistic growth occurs when

population size is limited by carryingpopulation size is limited by carrying

capacitycapacity


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Logistic Growth EquationLogistic Growth Equation

G = rG = rmaxmaxN ((K-N)/K)N ((K-N)/K)

G =G = population growth per unit timepopulation growth per unit time

rrmaxmax == maximum population growth ratemaximum population growth rate

per unit timeper unit time

N =N = number of individualsnumber of individuals

K =K = carrying capacitycarrying capacity


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Logistic GrowthLogistic Growth

As size of the population increases,As size of the population increases,

rate of reproduction decreasesrate of reproduction decreases

When the population reaches carryingWhen the population reaches carrying

capacity, population growth ceasescapacity, population growth ceases


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Figure 45.6Page 812

initial carrying

capacity

new carrying

capacity

Logistic Growth Graph


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K StrategistsK Strategists

Long lifeLong life

Slower growthSlower growth

Late maturityLate maturity

Fewer large offspring.Fewer large offspring.

High parental care and protection.High parental care and protection.

High investment in individualHigh investment in individualoffspring.offspring.


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More on K StrategistsMore on K Strategists

Adapted to stable environment.Adapted to stable environment.

Later stages of succession.Later stages of succession.

Niche specialistsNiche specialistsPredators (often, but not always)Predators (often, but not always)

Regulated mainly by intrinsicRegulated mainly by intrinsic

factors.factors.

High trophic level.High trophic level.


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Top PredatorsTop Predators


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16. Define16. Define biotic potentialbiotic potential..


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Answer 16Answer 16

16. Define16. Define biotic potentialbiotic potential..

Maximum rate of increase perMaximum rate of increase per

individual under ideal conditionsindividual under ideal conditions


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17. What is17. What is K?K?


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Answer 17Answer 17

17. What is17. What is K?K?

Maximum number of individualsMaximum number of individuals

that can be sustained in athat can be sustained in a

particular habitatparticular habitat(carrying(carrying

capacity)capacity)

Q i 18


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18. State the logistic equation.18. State the logistic equation.

A 18


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Answer 18Answer 18

18. State the logistic equation.18. State the logistic equation.

G = rG = rmaxmaxN ((K-N)/K)N ((K-N)/K)

QQ ti 19


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19. Given the logistic equation,19. Given the logistic equation,

G = rG = rmaxmaxN (K-N/K)N (K-N/K)

What do the symbols stand for?What do the symbols stand for?

A 19A 19


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Answer 19Answer 19

19. Given the logistic equation,19. Given the logistic equation,

G = rG = rmaxmaxN (K-N/K)N (K-N/K)

What do the symbols stand for?What do the symbols stand for?

G =G = population growth per unit timepopulation growth per unit time

rrmaxmax == maximum population growth rate per unit timemaximum population growth rate per unit time

N =N = number of individualsnumber of individuals

K =K = carrying capacitycarrying capacity

Q ti 20Q ti 20


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20.Refering to the former equation,20.Refering to the former equation,what happens towhat happens to GG as N approachesas N approaches

K?K?

A 20A 20


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Answer 20Answer 20

20.Refering to the former equation,20.Refering to the former equation,what happens to G as N approacheswhat happens to G as N approaches

K?K?

G (growth rate) approaches zero. TheG (growth rate) approaches zero. The

population stops growing.population stops growing.

O h ti C itO h ti C it


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Overshooting CapacityOvershooting Capacity

Population mayPopulation may

temporarilytemporarily

increase aboveincrease above

carrying capacitycarrying capacity Overshoot isOvershoot is

usually followed byusually followed by

a crash; dramatica crash; dramaticincrease in deathsincrease in deaths

Figure 45.6

Page 812

Reindeer on St. Matthews Island

D it D d t C t lD it D d t C t l


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Density-Dependent ControlsDensity-Dependent Controls

Logistic growth equation dealsLogistic growth equation deals

with density-dependent controlswith density-dependent controls

Limiting factors become moreLimiting factors become more

intense as population sizeintense as population size

increasesincreases

Disease, competition, parasites,Disease, competition, parasites,

toxic effects of waste productstoxic effects of waste products

D it I d d t C t lD it I d d t C t l


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Density-Independent ControlsDensity-Independent Controls

Factors unaffected by populationFactors unaffected by population

densitydensity

Natural disasters or climate changesNatural disasters or climate changes

affect large and small populationsaffect large and small populations

alikealike

A Hurricane is an Example of aA Hurricane is an Example of a


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A Hurricane is an Example of ap

Density Independent FactorDensity Independent Factor

E th Q k d T iE th Q k d T i


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Earth Quakes and TsunamisEarth Quakes and Tsunamis

Lif Hi t P ttLife Histor Patterns


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Life History PatternsLife History Patterns

Patterns of timing of reproductionPatterns of timing of reproduction

and survivorshipand survivorship

Vary among speciesVary among species

Summarized in survivorshipSummarized in survivorship

curves and life tablescurves and life tables

Lif T blLife Table


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Life TableLife Table

Tracks age-specific patternsTracks age-specific patterns

Population is divided into agePopulation is divided into age

categoriescategories

Birth rates and mortality risks areBirth rates and mortality risks are

calculated for each age categorycalculated for each age category


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Survivorship CurvesSurvivorship Curves

Graph of age-specific survivorshipGraph of age-specific survivorship

Figure 45.8

Page 815

Type IType I


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Type IType I

Large animals, few offspring, muchLarge animals, few offspring, muchparental care, live to an old ageparental care, live to an old age

Type IIType II


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Type IIType II

Birds are good examplesBirds are good examples

Intermediate number of offspring,Intermediate number of offspring,

some parental care, fairly constantsome parental care, fairly constant

survival rate over a lifesurvival rate over a life

time.time.

Type IIIType III


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Type IIIType III

These are typical r strategists,These are typical r strategists,weedy species, pesky..weedy species, pesky..

Short life, many offspring, littleShort life, many offspring, little

parental care, highparental care, high

mortality of themortality of the

youngyoung

Predation and Life HistoryPredation and Life History


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Predation and Life HistoryPredation and Life History

Guppy populations vary in life historyGuppy populations vary in life history

characteristics and morphologycharacteristics and morphology

Differences have genetic basisDifferences have genetic basis

Variation seems to be result of directionalVariation seems to be result of directional

selection by predatorsselection by predators

Human Population GrowthHuman Population Growth


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Human Population GrowthHuman Population Growth

Population now exceeds 6 billionPopulation now exceeds 6 billion

Rates of increase vary among countriesRates of increase vary among countries

Average annual increase is 1.26 percentAverage annual increase is 1.26 percent

Population continues to increasePopulation continues to increase

exponentiallyexponentially

Side Stepping ControlsSide Stepping Controls


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Side-Stepping ControlsSide-Stepping Controls

Expanded into new habitatsExpanded into new habitats

Agriculture increased carryingAgriculture increased carrying

capacity; use of fossil fuels aidedcapacity; use of fossil fuels aided

increaseincrease

Hygiene and medicine lessenedHygiene and medicine lessened

effects of density-dependent controlseffects of density-dependent controls

Future GrowthFuture Growth


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Future GrowthFuture Growth

Exponential growth cannot continueExponential growth cannot continue

foreverforever

Breakthroughs in technology mayBreakthroughs in technology may

further increase carrying capacityfurther increase carrying capacity

Eventually, density-dependentEventually, density-dependentfactors will slow growthfactors will slow growth

Fertility RatesFertility Rates


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Fertility RatesFertility Rates

Worldwide, average annual rate ofWorldwide, average annual rate of

increase is 1.26%increase is 1.26%

Total fertility rate (TFR) is averageTotal fertility rate (TFR) is average

number of children born to a womannumber of children born to a woman

Highest in developing countries, lowestHighest in developing countries, lowest

in developed countriesin developed countries

Age Structure DiagramsAge Structure Diagrams


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Age Structure DiagramsAge Structure Diagrams

Show age distribution of a populationShow age distribution of a population

Rapid

Growth

Slow

Growth

Zero

Growth

Negative

Growth

Figure 45.14

Page 821

Population MomentumPopulation Momentum


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Population MomentumPopulation Momentum

Lowering fertility ratesLowering fertility rates cannotcannot

immediately slow population growthimmediately slow population growth

raterate

Why? There are alreadyWhy? There are already many futuremany future

parents aliveparents alive

If every couple had just two children,If every couple had just two children,population would still keeppopulation would still keep growinggrowing

for another 60 yearsfor another 60 years

Projected Human PopulationsProjected Human Populations


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Projected Human PopulationsProjected Human Populations

Life Expectancy and IncomeLife Expectancy and Income


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Life Expectancy and IncomeLife Expectancy and Income

Slowing Growth in ChinaSlowing Growth in China


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Slowing Growth in ChinaSlowing Growth in China

Worlds most extensive familyWorlds most extensive family

planning programplanning program

Government rewards small familyGovernment rewards small familysize, penalizes larger families,size, penalizes larger families,

provides free birth control, abortion,provides free birth control, abortion,

sterilizationsterilization

Since 1972, TFR down to 1.8 fromSince 1972, TFR down to 1.8 from

5 75 7

Effects of EconomicEffects of Economic


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DevelopmentDevelopment

Total fertility rates (TFRs) are highest inTotal fertility rates (TFRs) are highest in

developing countries, lowest indeveloping countries, lowest in

developed countriesdeveloped countries

When individuals are economicallyWhen individuals are economically

secure, they are under less pressure tosecure, they are under less pressure to

have large familieshave large families

Sweat Shop IndiaSweat Shop India


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Sweat Shop, IndiaSweat Shop, India

http://www.mcps.k12.md.us/curriculum/socialstd/grade7/india/Sweatshop.html

Shop size = 2m x 5m. How many people can you count?

Population Sizes in 2001Population Sizes in 2001


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Population Sizes in 2001Population Sizes in 2001

Asia 3.7 billion

Europe 727 millionAfrica 816 million

Latin America 525 million

North America 316 million

Oceania 31 million

DemographicDemographic


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Transition ModelTransition Model

Based on historical data fromBased on historical data from

western Europewestern Europe

Postulates that as countries becomePostulates that as countries become

industrialized, first death rates drop,industrialized, first death rates drop,

then birth rates dropthen birth rates drop

DemographicDemographic


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Transition ModelTransition Model

Stage 1

Preindustrial

Stage 2

Transitional

Stage 3

Industrial

Stage 4

Postindustrial

births

deaths

relative

population

size

low increasing very high decreasing low zero negative

Resource ConsumptionResource Consumption


114/114

Resource ConsumptionResource Consumption

United States has 4.7 percent of theUnited States has 4.7 percent of the

worlds populationworlds population

Americans have a disproportionatelyAmericans have a disproportionately

large effect on the worlds resourceslarge effect on the worlds resources

Per capita, Americans consume morePer capita, Americans consume more

resources and create more pollutionresources and create more pollutionthan citizens of less developedthan citizens of less developed

nationsnations

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