Chapter 8Chapter 8Population ChangePopulation Change

Overview of Chapter 8Overview of Chapter 8

o Principles of Population EcologyPrinciples of Population Ecologyo Reproductive StrategiesReproductive Strategieso The Human PopulationThe Human Populationo Demographics of CountriesDemographics of Countrieso Demographics of United StatesDemographics of United States

Principles of Population EcologyPrinciples of Population Ecology

Population EcologyPopulation Ecology• Study of populations and why their numbers Study of populations and why their numbers

change over time. For example, what is the change over time. For example, what is the pattern of reproduction, and what is the pattern pattern of reproduction, and what is the pattern of mortalityof mortality

• Important forImportant for• Endangered speciesEndangered species• Invasive speciesInvasive species

PopulationPopulation• Group of individuals of same species living in Group of individuals of same species living in

the same geographic area at the same timethe same geographic area at the same time

Population DensityPopulation Density

Population densityPopulation density• The number of individuals of a species per The number of individuals of a species per

unit area or volume at a given timeunit area or volume at a given time• Ex: minnows per Liter of pond waterEx: minnows per Liter of pond water

Ovals below have same population, and Ovals below have same population, and different densitiesdifferent densities

Change in Population SizeChange in Population Size

Change in Population SizeChange in Population Size

Calculating Population ChangeCalculating Population Change

Birth (b), Death (d), Immigration (i) and Birth (b), Death (d), Immigration (i) and Emigration (e) are calculated per 1000 peopleEmigration (e) are calculated per 1000 people

GrowthGrowth raterate

Birth Birth raterate

Death Death raterate

Immigration Immigration raterate

Emigration Emigration raterate

r = (b – d)r = (b – d) + (i – e) + (i – e)

Maximum Population GrowthMaximum Population Growth

Intrinsic Rate of Growth (Biotic Potential)Intrinsic Rate of Growth (Biotic Potential)• Growth rate under ideal conditionsGrowth rate under ideal conditions• J- Shaped Curve (exponential growth)J- Shaped Curve (exponential growth)

Environmental ResistanceEnvironmental Resistance

Environmental limits (resistance)Environmental limits (resistance)• Prevent indefinite reproductionPrevent indefinite reproduction• Unfavorable food, water, shelter, predation, Unfavorable food, water, shelter, predation,

etc.etc.

Carrying Capacity (K)Carrying Capacity (K)• Maximum # of individuals an environment Maximum # of individuals an environment

can supportcan support• Causes leveling off of exponential growthCauses leveling off of exponential growth• S- shaped curve (logistic population growth)S- shaped curve (logistic population growth)

Population CrashPopulation Crash

Overshooting carrying capacity can lead to Overshooting carrying capacity can lead to population crashpopulation crash• Abrupt decline in population densityAbrupt decline in population density

Factors That Affect Population SizeFactors That Affect Population Size

Density Dependent Factor:Density Dependent Factor:• Factor whose effect on population changes Factor whose effect on population changes

as population density changesas population density changes• Examples:Examples:

• PredationPredation• DiseaseDisease• CompetitionCompetition

• Sometimes cause Boom-or-Bust Population Sometimes cause Boom-or-Bust Population CyclesCycles

Boom-Or-Bust Population CyclesBoom-Or-Bust Population Cycles

Case Study- Predator Prey Dynamics Case Study- Predator Prey Dynamics on Isle Royaleon Isle Royale

As wolf population increases, moose As wolf population increases, moose population decreases (and vice versa)population decreases (and vice versa)

Factors That Affect Population SizeFactors That Affect Population Size

Density Independent FactorsDensity Independent Factors• Factors that affects population size, but is Factors that affects population size, but is

not influenced by changes in population not influenced by changes in population densitydensity

• Examples:Examples:• Killing frostKilling frost• Severe blizzardSevere blizzard• FireFire• HurricanesHurricanes• Geologic events, etc.Geologic events, etc.

Reproductive StrategiesReproductive StrategiesLife History StrategiesLife History Strategies

r-selected k-selectedvs.

high growth rate slow growth rate

small body size large body size

early maturity late maturity

short life span long life span

large broods small broods

little / no parental care high parental care

Reproductive StrategiesReproductive Strategies

r-selected speciesr-selected species k-selected speciesk-selected species

Mosquitoes Mosquitoes

DandelionsDandelions

-Redwood trees Redwood trees -Human beingsHuman beings

SurvivorshipSurvivorship

Some populations fit two curvesSome populations fit two curves

Herring GullsHerring Gulls

Type III & Type III & Type IIType II

Human PopulationHuman Population

DemographyDemography• Science of Science of

population population structure and structure and growthgrowth

Human Population Human Population since 1980 is J-since 1980 is J-shaped curveshaped curve

Human PopulationHuman Population1 Billion1 Billion 18001800

2 Billion2 Billion 19301930

3 Billion3 Billion 19601960

4 Billion4 Billion 19751975

5 Billion5 Billion 19871987

6 Billion6 Billion 19991999

6.6 Billion6.6 Billion 20062006

7.0 Billion 7.0 Billion 20112011

Population clock

Population Increase in MexicoPopulation Increase in Mexico

What can you tell me about this graph?

Projecting Future Projecting Future PopulationsPopulations

Population is increasingPopulation is increasing

Growth rate (r) has Growth rate (r) has started to declinestarted to decline

Projections for 2050Projections for 2050• Low = 7.7 billionLow = 7.7 billion• High = 10.6 billionHigh = 10.6 billion• Most likely = 9.1 billionMost likely = 9.1 billion

Demographics of CountriesDemographics of Countries

Demographics of CountriesDemographics of Countries

Country

2004 population

(in Millions)

2010 population

(in Millions)

Population Density

(2004 per mi2)

Population Density

(2010 per mi2)

China 1300 1341 352 360

India 1087 1192 856 940

United States 293.6 310 79 83

Indonesia 218.7 238 297 313

Brazil 179.1 191 54 60

Pakistan 159.2 171 518 552

Nigeria 137.3 158 385 433

Bangladesh 141.3 150 2542 2919

Russia 144.1 142 22 21

Japan 127.6 127.4 875 873

Demographics of CountriesDemographics of Countries

Developed vs. Developing Countries Demographics

Demographics of CountriesDemographics of Countries

Developed vs. Developing Countries Demographics

Demographic StagesDemographic Stages

Pre-industrial StagePre-industrial Stage• Birth and death rates highBirth and death rates high• Modest population growthModest population growth

Transitional StageTransitional Stage• Lowered death rateLowered death rate• Rapid population growthRapid population growth

Industrial StageIndustrial Stage• Birth rate declineBirth rate decline• Population growth slowPopulation growth slow

Post Industrial StagePost Industrial Stage• Low birth and death ratesLow birth and death rates• Population growth very slowPopulation growth very slow

Demographic StagesDemographic Stages

Age StructureAge Structure

o The number and proportion of people at The number and proportion of people at each age in a populationeach age in a population

Demographics of Specific CountriesDemographics of Specific Countries

Examples:Examples:

Demographics of Specific CountriesDemographics of Specific Countries

Examples:Examples:

Demographics of Specific CountriesDemographics of Specific Countries

Examples:Examples:

World-wide World-wide

29% of human 29% of human population is population is under age 15under age 15

Could cause large Could cause large increase in birth increase in birth ratesrates

Demographics of the USDemographics of the US

Education of Immigrants into USEducation of Immigrants into US