Population Ecology

1、Population EcologyPopulation DynamicsPopulation:All the individuals of a species that live together in an areaDemography:The statistical study of populations, allows predictions to be made about how a population will changePopulation DynamicsThree Key Features of PopulationsSizeDensityDispersionThre

2、e Key Features of PopulationsSize: number of individuals in an areaThree Key Features of PopulationsGrowth Rate: Birth Rate (natality) - Death Rate (mortality)How many individuals are born vs. how many dieBirth rate (b) death rate (d) = rate of natural increase (r)Density: measurement of population

3、per unit area or unit volumePop. Density = # of individuals unit of space Three Key Features of PopulationsImmigration: movement of individuals into a population Emigration: movement of individuals out of a population Density-dependent factors: Biotic factors in the environment that have an increasi

4、ng effect as population size increases (disease, competition, parasites)Density-independent factors: Abiotic factors in the environment that affect populations regardless of their density (temperature, weather)How Do You Affect Density?ImmigrationEmigrationNatalityMortalityPopulation+-Factors That A

5、ffect Future Population GrowthPopulation DispersionDispersion: describes the spacing of organisms relative to each otherClumpedUniformRandomThree Key Features of PopulationsPopulation density = number of individuals in a given area or volumeCount all the individuals in a populationEstimate by sampli

6、ngMark-Recapture MethodHow Are Populations Measured? Idealized models describe two kinds of population growth:Exponential Growth2. Logistic GrowthHow Do Populations Grow?Carrying CapacityCarrying Capacity (k): The maximum population size that can be supported by the available resourcesThere can only

7、 be as many organisms as the environmental resources can supportFigure 35.3AExponential Growth CurveLogistic Growth CurveDeclining birth rate or increasing death rate are caused by several factors including:Limited food supplyThe buildup of toxic wastesIncreased diseasePredation Factors Limiting Gro

8、wth Rate “Booms” and “Busts”R StrategistsShort life span Small body sizeReproduce quickly Have many young Little parental care Ex: cockroaches, weeds, bacteria Reproductive StrategiesReproductive StrategiesK StrategistsLong life spanLarge body size Reproduce slowly Have few young Provides parental c

9、are Ex: humans, elephants Age DistributionDistribution of males and females in each age group of a populationUsed to predict future population growthHuman Population GrowthJ curve growthGrows at a rate of about 80 million yearly r =1.3%Why doesnt environmental resistance take effect?Altering their environmentTechnological advancesThe cultural revolutionThe agricultural revolutionThe industrial-medical revolutionDoubled three times in the last three centuriesAbout 6.1 billi