ecology of populations chapter 46. chapter outline scope of ecology scope of ecology population...
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Ecology of Ecology of PopulationsPopulations
Chapter 46Chapter 46
Chapter OutlineChapter Outline Scope of EcologyScope of Ecology Population Density and DistributionPopulation Density and Distribution Population Growth ModelsPopulation Growth Models Survivorship CurvesSurvivorship Curves Age DistributionsAge Distributions Regulation of Population SizeRegulation of Population Size Life History PatternsLife History Patterns Human Population GrowthHuman Population Growth
Environmental ImpactEnvironmental Impact
Scope of EcologyScope of Ecology
EcologyEcology – what is it? – what is it? Definitions:Definitions:
Habitat Habitat - Place where an organism lives.- Place where an organism lives. PopulationPopulation - All the organisms within an - All the organisms within an
area belonging to the same species.area belonging to the same species. CommunityCommunity - All various populations - All various populations
interacting at same locale.interacting at same locale. EcosystemEcosystem – A collection of communities – A collection of communities
Ecological LevelsEcological Levels
Density and Density and Distribution of Distribution of
PopulationsPopulations Population DensityPopulation Density - Number - Number
of individuals per unit area or of individuals per unit area or volume.volume.
Population DistributionPopulation Distribution - - Pattern of dispersal of Pattern of dispersal of individuals within the area of individuals within the area of interest.interest.
Uniform DistributionUniform Distribution
Random DistributionRandom Distribution
Clumped DistributionClumped Distribution
Characteristics of Characteristics of PopulationsPopulations
They tend to growThey tend to grow Intrinsic Rate of Natural Intrinsic Rate of Natural
Increase (Increase (rr))
Population Growth Population Growth ModelsModels
Exponential GrowthExponential GrowthBiotic PotentialBiotic Potential Environmental ResistanceEnvironmental Resistance
Exponential Growth CurveExponential Growth Curve
Logistic GrowthLogistic Growth
Logistic growth—indicated by an S-Logistic growth—indicated by an S-shaped curveshaped curve
Difference between logistic and Difference between logistic and exponential due to environmental exponential due to environmental resistanceresistance
Logistic GrowthLogistic Growth
Carrying CapacityCarrying Capacity
Carrying Capacity is the maximum Carrying Capacity is the maximum number of individuals of a given number of individuals of a given species the environment can support.species the environment can support. The closer the population to the carrying The closer the population to the carrying
capacity, the greater the environmental capacity, the greater the environmental resistance.resistance.
Biotic potential is having full effect and Biotic potential is having full effect and birthrate is a maximum during exponential birthrate is a maximum during exponential growth.growth.
St. Paul Island Reindeer Population
Mortality PatternsMortality Patterns CohortCohort --- all the members of a --- all the members of a
population born at the same time.population born at the same time. SurvivorshipSurvivorship---the probability of ---the probability of
newborn individuals of a cohort newborn individuals of a cohort surviving to particular ages.surviving to particular ages.
Illustrated by Survivorship CurvesIllustrated by Survivorship Curves
Survivorship CurvesSurvivorship Curves
Survivorship CurvesSurvivorship Curves
Age DistributionsAge Distributions
What proportion of What proportion of population is in each population is in each cohort? cohort?
Age Structure DiagramsAge Structure Diagrams
U.S. Age Distributions U.S. Age Distributions
Regulation of Population Regulation of Population SizeSize
Density - Dependent Density - Dependent FactorsFactors
Density - Independent Density - Independent FactorsFactors
Factors That Affect Population Size
Density Dependent Factors
1. Competition Intraspecific Interspecific
2. Predation
3. Parasitism
4. Disease
Factors That Affect Population Size
Density Independent Factors
1. Abiotic factors
2. Unpredictable, catastrophic
events
Life History PatternsLife History Patterns r r - Strategists - Strategists
(Opportunistic)(Opportunistic) Remember Remember
r=reproductionr=reproduction
Life History PatternsLife History Patterns k k - Strategists (Equilibrium)- Strategists (Equilibrium)
Remember k=Karrying Remember k=Karrying kapacitykapacity
Human Population GrowthHuman Population Growth
Human population has had an Human population has had an exponential growth pattern.exponential growth pattern. Doubling time currently estimated at 53 Doubling time currently estimated at 53
years.years. Population SizePopulation Size
1800 1800 1 Billion1 Billion 1930 1930 2 Billion2 Billion 196019603 Billion3 Billion 200020006 Billion6 Billion
World Population GrowthWorld Population Growth
Country Country DevelopmentDevelopment More-Developed Countries More-Developed Countries
(MDCs) GR=0.1%(MDCs) GR=0.1% Less-Developed Countries Less-Developed Countries
(LDCs) GR= 1.6%(LDCs) GR= 1.6% LDC population expected to LDC population expected to increase from 5-8b by 2050increase from 5-8b by 2050
Age DistributionsAge Distributions Age Structure DiagramsAge Structure Diagrams
divide populations into divide populations into three age groups.three age groups.Pre-ReproductivePre-ReproductiveReproductiveReproductivePost-ReproductivePost-Reproductive
The Demographic The Demographic TransitionTransition
Stage I: high birthrates and death Stage I: high birthrates and death ratesrates
Stage II: continued high birthrates, Stage II: continued high birthrates, declining death ratesdeclining death rates
Stage III: falling birthrates and death Stage III: falling birthrates and death rates, eventually stabilizingrates, eventually stabilizing
More-Developed CountriesMore-Developed Countries
Less-Developed CountriesLess-Developed Countries
Population Structures by Age and Sex, 2005 Millions
300 100 100 300300 200 100 0 100 200 300
Less Developed Regions
More Developed Regions
Male Female Male Female
80+ 75-79 70-74 65-69 60-64 55-59 50-54 45-49 40-44 35-39 30-34 25-29 20-24 17-19 10-16
5-90-4
Age
Source: United Nations, World Population Prospects: The 2002 Revision (medium scenario), 2003.
Age Distribution of the World’s Age Distribution of the World’s PopulationPopulation
Figure 7.2Figure 7.2 World World Population Distribution by Population Distribution by
Region, 1998 and 2050Region, 1998 and 2050
Environmental ImpactEnvironmental Impact
Measured in terms of:Measured in terms of:Population SizePopulation SizeResource Consumption Resource Consumption Per Capita Per Capita
Resultant PollutionResultant Pollution
Environmental ImpactEnvironmental Impact
ReviewReview Scope of EcologyScope of Ecology Population Density and DistributionPopulation Density and Distribution Population Growth ModelsPopulation Growth Models Survivorship CurvesSurvivorship Curves Age DistributionsAge Distributions Regulation of Population SizeRegulation of Population Size Life History PatternsLife History Patterns Human Population GrowthHuman Population Growth
Environmental ImpactEnvironmental Impact
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