Transcript
Population Ecology Population Ecology 20122012
Population EcologyPopulation Ecology
Certain ecological principles govern the Certain ecological principles govern the
growth and sustainability of all growth and sustainability of all
populations--including human populations--including human
populations populations
Ecological Principles Apply to All Ecological Principles Apply to All SpeciesSpecies
Humans, Palms, Crabs, Seagulls, algae, etc.
Limits to GrowthLimits to Growth
A population’s growth depends on A population’s growth depends on
the resources of its environmentthe resources of its environment
Deer introduced to Angel Island Deer introduced to Angel Island
– Population outstripped resourcesPopulation outstripped resources
Angel IslandAngel Island
Angel Island 1Angel Island 1 A. Angel Island is a game reserve in San A. Angel Island is a game reserve in San
Francisco Bay near Sausalito Francisco Bay near Sausalito B. In the early 1900's well-meaning nature B. In the early 1900's well-meaning nature
lovers introduced deer to the islandlovers introduced deer to the island C. With no natural predators to control C. With no natural predators to control
them the population quickly rose to a level them the population quickly rose to a level much higher than the island could supportmuch higher than the island could support
D. Well meaning people brought food to D. Well meaning people brought food to the island to feed the deer, causing the the island to feed the deer, causing the population to further increasepopulation to further increase
Angel Island 2Angel Island 2
E. Eventually the population grew to E. Eventually the population grew to over 300, much too large for the over 300, much too large for the island to supportisland to support
F. As the deer began to starve they F. As the deer began to starve they ate most of the native vegetation. ate most of the native vegetation. Without vegetation the soil started Without vegetation the soil started washing away and the island washing away and the island environment rapidly deterioratedenvironment rapidly deteriorated
Angel Island - 3Angel Island - 3
G. It was proposed that hunters kill some G. It was proposed that hunters kill some of the deer and/or that coyotes, the deer’s of the deer and/or that coyotes, the deer’s natural predators, be introduced to the natural predators, be introduced to the island. However many people objected island. However many people objected because they viewed both alternatives as because they viewed both alternatives as cruelcruel
H. Eventually two thirds of the population H. Eventually two thirds of the population was rounded up and moved to the was rounded up and moved to the mainland, at a cost of $3,000 per deermainland, at a cost of $3,000 per deer
Angel Island - 4Angel Island - 4 I. However, tracking studies revealed that I. However, tracking studies revealed that
the majority of the deer moved to the the majority of the deer moved to the mainland 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 a J. The story of Angel Island illustrates a basic ecological principle: a population's basic ecological principle: a population's growth is dependent on the resources of growth is dependent on the resources of its environment. Human intervention could its environment. Human intervention could only postpone, not prevent the inevitableonly postpone, not prevent the inevitable
Angel Island - 5Angel Island - 5 K. Many environmental problems are simply the K. Many environmental problems are simply the
result of a lack of understanding of basic result of a lack of understanding of basic ecological principles by politicians, lawyers, ecological principles by politicians, lawyers, economists, the general public and even well economists, the general public and even well intentioned "environmentalists". Human intentioned "environmentalists". Human ignorance of simple ecological principles often ignorance of simple ecological principles often leads to disastrous resultsleads to disastrous results
From: From: http://arnica.csustan.edu/boty1050/Ecology/ecolohttp://arnica.csustan.edu/boty1050/Ecology/ecology.htmgy.htm
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 Most resources are consumed by
the relatively few people in the relatively few people in
developed countries developed countries
Population GrowthPopulation Growth
For most of human history, humans For most of human history, humans have not been very numerous have not been very numerous compared to other species.compared to other species.– It took all of human history to reach 1 It 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 the Human population tripled during the twentieth century.twentieth century.
World Population Growth World Population Growth VisualizedVisualized
From youtubeFrom youtube
http://www.youtube.com/watch?v=4BbkQiQyaYc
Human Population HistoryHuman Population History
Seven Billion…..Seven Billion…..
From the National Geographic:From the National Geographic: http://www.youtube.com/watch?v=sc
4HxPxNrZ0
U.S. POPClock ProjectionU.S. POPClock Projection
According to the U.S. Bureau of the Census, the According to the U.S. Bureau of the Census, the resident population of the United States, resident population of the United States, projected to 03/21/05 at 17:04 GMT (EST+5) is projected to 03/21/05 at 17:04 GMT (EST+5) is
295,707,750295,707,750 COMPONENT SETTINGSCOMPONENT SETTINGS One birth every.................................. 7 seconds One birth every.................................. 7 seconds
One death every.................................. 11 seconds One death every.................................. 11 seconds One international migrant (net) every............ 24 One international migrant (net) every............ 24 seconds Net gain of one person seconds Net gain of one person every..................... 12 seconds every..................... 12 seconds
So what do you think the US population is today?So what do you think the US population is today?
US PopClock todayUS PopClock today
http://www.census.gov/population/www/popclockus.html
PopulationPopulation
A group of individuals of the same species A group of individuals of the same species
occupying a given area during a particular occupying a given area during a particular
period 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
Population Age StructurePopulation Age Structure
Divide population into age categoriesDivide population into age categories
Population’s reproductive base Population’s reproductive base
includes members of the reproductive includes members of the reproductive
and pre-reproductive age categoriesand pre-reproductive age categories
Population Age Structure DiagramPopulation Age Structure Diagram
Density & DistributionDensity & Distribution
Number of Number of individuals in some individuals in some specified area of specified area of habitathabitat
Crude density Crude density information is more information is more useful if combined useful if combined with distribution with distribution
datadata
clumped
nearly uniform
random Figure 45.2
Page 808
Clumped DistributionClumped Distribution
Determining Population SizeDetermining Population Size
Direct counts are most accurate but Direct counts are most accurate but seldom feasibleseldom feasible
Can sample an area, then extrapolateCan sample an area, then extrapolate
Capture-recapture method is used for Capture-recapture method is used for mobile speciesmobile species
Population EstimatePopulation Estimate
How could you determine the How could you determine the population size of the students in population size of the students in Robinson Hall? Robinson Hall?
The number of revelers on the beach?The number of revelers on the beach?
Does Time and Place Make a Does Time and Place Make a Difference?Difference?
Daytona Beach
Hilton Head
Capture-Recapture MethodCapture-Recapture Method
Capture, mark, and release Capture, mark, and release individualsindividuals
Return later and capture second Return later and capture second samplesample
Count the number of marked Count the number of marked individuals and use this to estimate individuals and use this to estimate total populationtotal population
Example:Example:Capture - RecaptureCapture - Recapture
In 1970, naturalists wanted to estimate In 1970, naturalists wanted to estimate the number of pickerel fish in Dryden Lake the number of pickerel fish in Dryden Lake in central New York State. They in central New York State. They captured captured 232 pickerel232 pickerel, put a mark on their fins, , put a mark on their fins, and returned the fish to the lake. Several and returned the fish to the lake. Several weeks later, another weeks later, another sample of 329 sample of 329 pickerelpickerel fish were captured. Of this fish were captured. Of this second sample, second sample, 16 had marks on their 16 had marks on their fins.fins. (Chaterjee in Mosteller et al. (Chaterjee in Mosteller et al. Statistics by Example: Finding ModelsStatistics by Example: Finding Models).).
Chain PickerelChain Pickerel
How Many Pickerel Were in the How 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 pickerel NM = 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
Solution Solution
N = (232 x 329)/16N = (232 x 329)/16
N = 4770N = 4770 pickerel in the lake pickerel in the lake (estimate)(estimate)
This is an example of how the This is an example of how the “Capture/Recapture” method works.“Capture/Recapture” method works.
AssumptionsAssumptions
The sampling is randomThe sampling is random The marked organisms will not be harmed The marked organisms will not be harmed
by the capture and markingsby the capture and markings The marked organisms will not avoid The marked organisms will not avoid
recapturerecapture The samples are statistically large enough The samples are statistically large enough
to avoid problems with sampling errorto avoid problems with sampling error No significant emigration/immigration No significant emigration/immigration
occursoccurs The sampling is done promptlyThe sampling is done promptly
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
Zero Population GrowthZero Population Growth
Interval in which number of births Interval in which number of births
is balanced by number of deathsis balanced by number of deaths
Assume no change as a result of Assume no change as a result of
migrationmigration
Population size remains stablePopulation size remains stable
Per Capita RatesPer Capita Rates Rates per individualRates per individual
Total number of events in a time Total number of events in a time
interval divided by the number of interval divided by the number of
individualsindividuals
Per capita birth rate per month =Per capita birth rate per month =
Number of births per month Number of births per month
Population sizePopulation size
rr
Net reproduction per individual per unit Net reproduction per individual per unit
time (Intrinsic rate of natural increase) time (Intrinsic rate of natural increase)
a constant the units are inverse timea constant the units are inverse time
Variable combines per capita birth and Variable combines per capita birth and
death rates (assuming both constant)death rates (assuming both constant)
Can be used to calculate rate of growth Can be used to calculate rate of growth
of a populationof a population
Exponential Growth EquationExponential Growth Equation
GG = = rNrN
GG is population growth per unit time is population growth per unit time rr is net reproduction per individual is net reproduction per individual
per unit timeper unit time NN is population size is population size
Exponential GrowthExponential Growth
Population size Population size expands by ever expands by ever increasing increasing increments during increments during successive intervalssuccessive intervals
The larger the The larger the population gets, the population gets, the more individuals more individuals there are to there are to reproducereproduce
Figure 45.4Page 810
(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.
Weedy Species – “r Strategists”Weedy Species – “r Strategists” Opportunistic Species - Quickly appear when opportunities Opportunistic Species - Quickly appear when opportunities
arise.arise.– Many weeds.Many weeds.
Pioneer Species - Can quickly colonize open, disturbed, or Pioneer Species - Can quickly colonize open, disturbed, or bare ground.bare ground.
Effect of DeathsEffect of Deaths
Population grows exponentially as long as per Population grows exponentially as long as per capita death rates are lower than per capita birth capita death rates are lower than per capita birth
ratesrates
25% mortality
between divisions
Figure 45.5Page 811
Biotic PotentialBiotic Potential
Maximum rate of increase per Maximum rate of increase per
individual under ideal conditionsindividual under ideal conditions
Varies between speciesVaries between species
In nature, biotic potential is rarely In nature, biotic potential is rarely
reachedreached
Limiting FactorsLimiting Factors
Any essential resource that is in Any essential resource that is in
short supplyshort supply
All limiting factors acting on a All limiting factors acting on a
population dictate sustainable population dictate sustainable
population sizepopulation size
Carrying Capacity (Carrying Capacity (KK))
Maximum number of individuals that Maximum number of individuals that
can be sustained in a particular habitatcan be sustained in a particular habitat
Logistic growth occurs when Logistic growth occurs when
population size is limited by carrying population size is limited by carrying
capacitycapacity
Logistic Growth EquationLogistic Growth Equation
G = rG = rmaxmax N ((K-N)/K)N ((K-N)/K)
G = G = population growth per unit timepopulation growth per unit time
rrmaxmax = = maximum population growth rate maximum population growth rate
per unit timeper unit time
N = N = number of individualsnumber of individuals
K = K = carrying capacitycarrying capacity
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 carrying When the population reaches carrying capacity, population growth ceasescapacity, population growth ceases
Figure 45.6Page 812
initial carrying capacity
new carrying capacity
Logistic Growth GraphLogistic Growth Graph
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 individual High investment in individual
offspring.offspring.
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 intrinsic Regulated mainly by intrinsic
factors.factors.High trophic level.High trophic level.
Top PredatorsTop Predators
Overshooting CapacityOvershooting Capacity
Population may Population may temporarilytemporarily increase above increase above carrying capacitycarrying capacity
Overshoot is Overshoot is usually followed by usually followed by a crash; dramatic a crash; dramatic increase in deathsincrease in deaths
Figure 45.6Page 812
Reindeer on St. Matthew’s Island
Density-Dependent ControlsDensity-Dependent Controls
Logistic growth equation deals with Logistic growth equation deals with
density-dependent controlsdensity-dependent controls
Limiting factors become more Limiting factors become more
intense as population size intense as population size
increasesincreases
Disease, competition, parasites, Disease, competition, parasites,
toxic effects of waste productstoxic effects of waste products
Density-Independent ControlsDensity-Independent Controls
Factors unaffected by population Factors unaffected by population
densitydensity
Natural disasters or climate changes Natural disasters or climate changes
affect large and small populations affect large and small populations
alikealike
A Hurricane is an Example of a A Hurricane is an Example of a Density Independent FactorDensity Independent Factor
Earth Quakes and TsunamisEarth Quakes and Tsunamis
Life History PatternsLife History Patterns
Patterns of timing of reproduction Patterns of timing of reproduction
and survivorshipand survivorship
Vary among speciesVary among species
Summarized in survivorship Summarized in survivorship
curves and life tablescurves and life tables
Life TableLife Table
Tracks age-specific patterns Tracks age-specific patterns
Population is divided into age Population is divided into age
categoriescategories
Birth rates and mortality risks are Birth rates and mortality risks are
calculated for each age categorycalculated for each age category
USAUSA
Survivorship CurvesSurvivorship Curves
Graph of age-specific survivorship Graph of age-specific survivorship
Figure 45.8Page 815
Type IType I
Large animals, few offspring, much Large animals, few offspring, much parental care, live to an old ageparental care, live to an old age
Type IIType II
Birds are good examples……Birds are good examples……
Intermediate number of offspring, Intermediate number of offspring, some parental care, fairly constant some parental care, fairly constant survival rate over a lifesurvival rate over a life
time.time.
Type IIIType III
These are typical “r strategists”, These are typical “r strategists”, weedy species, pesky…..weedy species, pesky…..
Short life, many offspring, little Short life, many offspring, little parental care, high parental care, high
mortality of themortality of the
young…young…
Predation and Life History Predation and Life History
Guppy populations vary in life history Guppy populations vary in life history
characteristics and morphologycharacteristics and morphology
Differences have genetic basisDifferences have genetic basis
Variation seems to be result of directional Variation seems to be result of directional
selection by predatorsselection by predators
Human Population Growth Human 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 increase Population continues to increase
exponentiallyexponentially
Side-Stepping ControlsSide-Stepping Controls
Expanded into new habitats Expanded into new habitats
Agriculture increased carrying capacity; Agriculture increased carrying capacity;
use of fossil fuels aided increaseuse of fossil fuels aided increase
Hygiene and medicine lessened effects Hygiene and medicine lessened effects
of density-dependent controlsof density-dependent controls
Future GrowthFuture Growth
Exponential growth cannot continue Exponential growth cannot continue
foreverforever
Breakthroughs in technology may Breakthroughs in technology may
further increase carrying capacity further increase carrying capacity
Eventually, density-dependent Eventually, density-dependent
factors will slow growthfactors will slow growth
Fertility Rates Fertility Rates
Worldwide, average annual rate of Worldwide, average annual rate of
increase is 1.26%increase is 1.26%
Total fertility rate (TFR) is average Total fertility rate (TFR) is average
number of children born to a womannumber of children born to a woman
Highest in developing countries, lowest Highest in developing countries, lowest
in developed countriesin developed countries
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 45.14Page 821
Population MomentumPopulation Momentum
Lowering fertility rates Lowering fertility rates cannotcannot immediately slow population growth immediately slow population growth raterate
Why? There are already Why? There are already many future many future parents aliveparents alive
If every couple had just two children, If every couple had just two children, population would still keep population would still keep growing growing for another 60 yearsfor another 60 years
Projected Human PopulationsProjected Human Populations
Life Expectancy and IncomeLife Expectancy and Income
Slowing Growth in ChinaSlowing Growth in China
World’s most extensive family World’s most extensive family
planning program planning program
Government rewards small family Government rewards small family
size, 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 from 5.7Since 1972, TFR down to 1.8 from 5.7
Effects of Economic Effects of Economic Development Development
Total fertility rates (TFRs) are highest in Total fertility rates (TFRs) are highest in
developing countries, lowest in developing countries, lowest in
developed countriesdeveloped countries
When individuals are economically When individuals are economically
secure, they are under less pressure to secure, they are under less pressure to
have large familieshave large families
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
Asia 3.7 billion
Europe 727 million
Africa 816 million
Latin America 525 million
North America 316 million
Oceania 31 million
Demographic Demographic Transition ModelTransition Model
Based on historical data from Based on historical data from
western Europewestern Europe
Postulates that as countries become Postulates that as countries become
industrialized, first death rates drop, industrialized, first death rates drop,
then birth rates dropthen birth rates drop
Demographic Demographic 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 negativeFigure 45.16
Page 822
Resource ConsumptionResource Consumption
United States has 4.7 percent of the United States has 4.7 percent of the world’s populationworld’s population
Americans have a disproportionately Americans have a disproportionately large effect on the world’s resourceslarge effect on the world’s resources
Per capita, Americans consume more Per capita, Americans consume more resources and create more pollution resources and create more pollution than citizens of less developed than citizens of less developed nationsnations
Population EcologyPopulation EcologyThe EndThe End
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