ch45 lecture(Pop Eco)Sans photos
Transcript of 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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Angel Island - 4Angel Island - 4
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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Angel Island - 5Angel Island - 5
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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Question 2Question 2
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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Question 3Question 3
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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Question 4Question 4
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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Question 5Question 5
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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Question 6Question 6
6. A populations ______ _____6. A populations ______ _____
includes members of theincludes members of the
reproductive and pre-reproductivereproductive and pre-reproductive
age categories.age categories.
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Answer 6Answer 6
6. A populations6. A populations reproductivereproductivebasebaseincludes members of theincludes members of the
reproductive and pre-reproductivereproductive and pre-reproductive
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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Question 7Question 7
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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Question 8Question 8
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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Question 9Question 9
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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Question 10Question 10
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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Question 11Question 11
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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Question 12Question 12
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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Question 13Question 13
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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Question 14Question 14
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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Question 15Question 15
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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Question 16Question 16
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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Question 17Question 17
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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Question 18Question 18
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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Question 19Question 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?
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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Question 20Question 20
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
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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