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  • Figure 53.3 Population dynamics.
  • Table 53.1 Life Table for Belding ’s Ground Squirrels ( Spermophilus beldingi ) at Tioga Pass, in the Sierra Nevada of California
  • Figure 53.5 Survivorship curves for male and female Belding ’s ground squirrels.
  • Figure 53.6 Idealized survivorship curves: Types I, II, and III.
  • Figure 53.12 An agave ( Agave americana ), an example of big-bang reproduction.
  • Figure 53.13 Inquiry: How does caring for offspring affect parental survival in kestrels?
  • Figure 53.7 Population growth predicted by the exponential model.
  • Figure 53.8 Exponential growth in the African elephant population of Kruger National Park, South Africa.
  • Figure 53.9 Population growth predicted by the logistic model.
  • Figure 53.10 How well do these populations fit the logistic growth model?
  • Figure 53.10 How well do these populations fit the logistic growth model?
  • Figure 53.17 Exploring: Mechanisms of Density-Dependent Regulation
  • Figure 53.17 Exploring: Mechanisms of Density-Dependent Regulation
  • Figure 53.17 Exploring: Mechanisms of Density-Dependent Regulation
  • Figure 53.17 Exploring: Mechanisms of Density-Dependent Regulation
  • Figure 53.18 Fluctuations in moose and wolf populations on Isle Royale, 1959–2008.
  • Figure 53.19 Population cycles in the snowshoe hare and lynx.
  • Figure 53.22 Human population growth (data as of 2009).
  • Figure 53.23 Annual percent increase in the global human population (data as of 2009).
  • Figure 53.24 Age-structure pyramids for the human population of three countries (data as of 2009).
  • Figure 53.25 Infant mortality and life expectancy at birth in industrialized and less industrialized countries (data as of 2008).
  • Figure 53.26 Annual per capita energy use around the world.
  • 52 lectures ppt

    1. 1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPowerPoint Lectures forBiology, Seventh EditionNeil Campbell and Jane ReeceLectures by Chris RomeroChapter 52Population Ecology
    2. 2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Population ecology is the study of populations inrelation to environment, including environmentalinfluences on density and distribution, agestructure, and population size© 2011 Pearson Education, Inc.
    3. 3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
    4. 4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsDynamic biological processes influence populationdensity, dispersion, and demography• A population is a group of individuals of a singlespecies living in the same general area
    5. 5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsDynamic biological processes influence populationdensity, dispersion, and demographics• A population is a group of individuals of a singlespecies living in the same general area• Populations are described by their boundaries andsize© 2011 Pearson Education, Inc.
    6. 6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsDensity and Dispersion• Density is the number of individuals per unit areaor volume• Dispersion is the pattern of spacing amongindividuals within the boundaries of the population© 2011 Pearson Education, Inc.
    7. 7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsDensity: A Dynamic Perspective• Determining the density of natural populations isdifficult• In most cases, it is impractical or impossible tocount all individuals in a population• Density is the result of an interplay betweenprocesses that add individuals to a population andthose that remove individuals– Immigration is the influx of new individuals from otherareas– Emigration is the movement of individuals out of apopulation
    8. 8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 53.3Births DeathsImmigration EmigrationBirths and immigrationadd individuals toa population.Deaths and emigrationremove individualsfrom a population.
    9. 9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPatterns of Dispersion• Environmental and social factors influencespacing of individuals in a population• In a clumped dispersion, individuals aggregate inpatches• A clumped dispersion may be influenced byresource availability and behavior© 2011 Pearson Education, Inc.
    10. 10. LE 52-3aClumped. For many animals, such as these wolves,living in groups increases the effectiveness of hunting,spreads the work of protecting and caring for young, andhelps exclude other individuals from their territory.
    11. 11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• A uniform dispersion is one in which individualsare evenly distributed• It may be influenced by social interactions such asterritoriality, the defense of a bounded spaceagainst other individuals© 2011 Pearson Education, Inc.
    12. 12. LE 52-3bUniform. Birds nesting on small islands, such as theseking penguins on South Georgia Island in the SouthAtlantic Ocean, often exhibit uniform spacing, maintainedby aggressive interactions between neighbors.
    13. 13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• In a random dispersion, the position of eachindividual is independent of other individuals• It occurs in the absence of strong attractions orrepulsions© 2011 Pearson Education, Inc.
    14. 14. LE 52-3cRandom. Dandelions grow from windblown seeds thatland at random and later germinate.
    15. 15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsDemographics• Demography is the study of the vital statistics of apopulation and how they change over time• Death rates and birth rates are of particularinterest to demographers© 2011 Pearson Education, Inc.
    16. 16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsLife Tables• A life table is an age-specific summary of thesurvival pattern of a population• It is best made by following the fate of a cohort, agroup of individuals of the same age• The life table of Belding’s ground squirrels revealsmany things about this population– For example, it provides data on the proportionsof males and females alive at each age© 2011 Pearson Education, Inc.
    17. 17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsTable 53.1
    18. 18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsSurvivorship Curves• A survivorship curve is a graphic way ofrepresenting the data in a life table• The survivorship curve for Belding’s groundsquirrels shows a relatively constant death rate© 2011 Pearson Education, Inc.
    19. 19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 53.5MalesFemales1,000100101Age (years)Numberofsurvivors(logscale)0 2 4 6 8 10
    20. 20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Survivorship curves can be classified into threegeneral types– Type I: low death rates during early and middlelife, then an increase in death rates among olderage groups– Type II: the death rate is constant over theorganism’s life span– Type III: high death rates for the young, then aslower death rate for survivors• Many species are intermediate to these curves© 2011 Pearson Education, Inc.
    21. 21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 53.61,000IIIIII100101100500Percentage of maximum life spanNumberofsurvivors(logscale)
    22. 22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsConcept 53.4: Life history traits are products ofnatural selection• An organism’s life history comprises the traitsthat affect its schedule of reproduction andsurvival– The age at which reproduction begins– How often the organism reproduces– How many offspring are produced during eachreproductive cycle• Life history traits are evolutionary outcomesreflected in the development, physiology, andbehavior of an organism© 2011 Pearson Education, Inc.
    23. 23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsEvolution and Life History Diversity• Species that exhibit semelparity, or big-bangreproduction, reproduce once and die• Species that exhibit iteroparity, or repeatedreproduction, produce offspring repeatedly• Highly variable or unpredictable environmentslikely favor big-bang reproduction, whiledependable environments may favor repeatedreproduction© 2011 Pearson Education, Inc.
    24. 24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 53.12
    25. 25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings“Trade-offs” and Life Histories• Organisms have finite resources, which may leadto trade-offs between survival and reproduction– For example, there is a trade-off between survivaland paternal care in European kestrels© 2011 Pearson Education, Inc.
    26. 26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 53.13MaleFemaleRESULTSReducedbrood sizeNormalbrood sizeEnlargedbrood sizeParentssurvivingthefollowingwinter(%)100806040200
    27. 27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Some plants produce a large number of smallseeds, ensuring that at least some of them willgrow and eventually reproduce© 2011 Pearson Education, Inc.
    28. 28. LE 52-8aMost weedy plants, such as this dandelion, grow quickly andproduce a large number of seeds, ensuring that at least somewill grow into plants and eventually produce seeds themselves.
    29. 29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Other types of plants produce a moderate numberof large seeds that provide a large store of energythat will help seedlings become established© 2011 Pearson Education, Inc.
    30. 30. LE 52-8bSome plants, such as this coconut palm, produce a moderatenumber of very large seeds. The large endosperm providesnutrients for the embryo, an adaptation that helps ensure thesuccess of a relatively large fraction of offspring.
    31. 31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPer Capita Rate of Increase• If immigration and emigration are ignored, apopulation’s growth rate (per capita increase)equals birth rate minus death rate• Zero population growth (ZPG) occurs when thebirth rate equals the death rate (r = 0)© 2011 Pearson Education, Inc.Change inpopulationsizeBirthsImmigrantsenteringpopulationDeathsEmigrantsleavingpopulation   
    32. 32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsExponential Growth• Exponential population growth is populationincrease under idealized conditions• Under these conditions, the rate of increase is atits maximum, denoted as rmax• The equation of exponential population growth is© 2011 Pearson Education, Inc.dNdt rmaxN• Exponential population growth results in aJ-shaped curve
    33. 33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsNumber of generationsPopulationsize(N)0 5 10 152,0001,5001,000500dNdtdNdt= 1.0N= 0.5NFigure 53.7
    34. 34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• The J-shaped curve of exponential growthcharacterizes some rebounding populations– For example, the elephant population in KrugerNational Park, South Africa, grew exponentiallyafter hunting was banned© 2011 Pearson Education, Inc.
    35. 35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 53.8YearElephantpopulation8,0006,0004,0002,00001900 1910 1920 1930 1940 1950 1960 1970
    36. 36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe logistic model describes how a populationgrows more slowly as it nears its carrying capacity• Exponential growth cannot be sustained for long inany population• A more realistic population model limits growth byincorporating carrying capacity• Carrying capacity (K) is the maximum populationsize the environment can support• Carrying capacity varies with the abundance oflimiting resources© 2011 Pearson Education, Inc.
    37. 37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Logistic Growth Model• In the logistic population growth model, the percapita rate of increase declines as carryingcapacity is reached• We construct the logistic model by starting with theexponential model and adding an expression thatreduces per capita rate of increase as N increases• The logistic model of population growth producesa sigmoid (S-shaped) curve
    38. 38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Logistic Growth Model• In the logistic population growth model, the percapita rate of increase declines as carryingcapacity is reached• The logistic model starts with the exponentialmodel and adds an expression that reduces percapita rate of increase as N approaches KdNdt(K  N)Krmax N© 2011 Pearson Education, Inc.• The logistic model of population growthproduces a sigmoid (S-shaped) curve
    39. 39. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsNumber of generationsPopulation growthbegins slowing here.ExponentialgrowthLogistic growthPopulationsize(N)0 5 15102,0001,5001,0005000K = 1,500dNdt= 1.0NdNdt= 1.0N1,500 – N1,500( )Figure 53.9
    40. 40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Logistic Model and Real Populations• The growth of laboratory populations of parameciafits an S-shaped curve• These organisms are grown in a constantenvironment lacking predators and competitors© 2011 Pearson Education, Inc.
    41. 41. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 53.10aTime (days)(a) A Paramecium population inthe labNumberofParamecium/mL1,00080060040020000 5 10 15
    42. 42. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• The logistic model fits few real populations but isuseful for estimating possible growth• Some populations overshoot K before settlingdown to a relatively stable density
    43. 43. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 53.10bTime (days)(b) A Daphnia population in the labNumberofDaphnia/50mL200 16040 60 80 100 120 1401801501209060300
    44. 44. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Some populations fluctuate greatly around K
    45. 45. LE 52-13cTime (years)Numberoffemales801975 19804019850199060A song sparrow population in its natural habitat201995 2000
    46. 46. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Logistic Model and Life Histories• Life history traits favored by natural selection mayvary with population density and environmentalconditions• K-selection, or density-dependent selection,selects for life history traits that are sensitive topopulation density• r-selection, or density-independent selection,selects for life history traits that maximizereproduction
    47. 47. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• The concepts of K-selection and r-selection areoversimplifications but have stimulated alternativehypotheses of life history evolution© 2011 Pearson Education, Inc.
    48. 48. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPopulations are regulated by a complexinteraction of biotic and abiotic influences• There are two general questions about regulationof population growth:– What environmental factors stop a populationfrom growing?– Why do some populations show radicalfluctuations in size over time, while othersremain stable?
    49. 49. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPopulation Change and Population Density• In density-independent populations, birth rateand death rate do not change with populationdensity• In density-dependent populations, birth rates falland death rates rise with population density© 2011 Pearson Education, Inc.
    50. 50. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsMechanisms of Density-Dependent PopulationRegulation• Density-dependent birth and death rates are anexample of negative feedback that regulatespopulation growth• Density-dependent birth and death rates areaffected by many factors, such as competition forresources, territoriality, disease, predation, toxicwastes, and intrinsic factors© 2011 Pearson Education, Inc.
    51. 51. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCompetition for Resources• In crowded populations, increasing populationdensity intensifies competition for resources andresults in a lower birth rate© 2011 Pearson Education, Inc.
    52. 52. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsToxic Wastes• Accumulation of toxic wastes can contribute todensity-dependent regulation of population size© 2011 Pearson Education, Inc.
    53. 53. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPredation• As a prey population builds up, predators mayfeed preferentially on that species© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.
    54. 54. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 53.17bTrout feed preferentiallyon these insects as theyemerge from their aquaticlarval stage
    55. 55. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsIntrinsic Factors• For some populations, intrinsic (physiological)factors appear to regulate population size© 2011 Pearson Education, Inc.
    56. 56. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 53.17dIncreased population size can lead to hormonal changes that delaysexual maturation and depress the immune system, which decreasesthe birth rate and increases the death rate
    57. 57. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsTerritoriality• In many vertebrates and some invertebrates,competition for territory may limit density© 2011 Pearson Education, Inc.
    58. 58. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 53.17ea
    59. 59. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsOceanic birds exhibit territoriality in nestingbehavior
    60. 60. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsDisease• Population density can influence the health andsurvival of organisms• In dense populations, pathogens can spread morerapidly© 2011 Pearson Education, Inc.
    61. 61. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 53.17f
    62. 62. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPopulation Dynamics• The study of population dynamics focuses onthe complex interactions between biotic andabiotic factors that cause variation in populationsize© 2011 Pearson Education, Inc.
    63. 63. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsStability and Fluctuation• Long-term population studies have challenged thehypothesis that populations of large mammals arerelatively stable over time• Both weather and predator population can affectpopulation size over time– For example, moose on Isle Royale collapsedduring a harsh winter, and when wolf numberspeaked© 2011 Pearson Education, Inc.
    64. 64. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsWolves MooseYearNumberofwolvesNumberofmoose1955 1965 1975 1985 1995 2005504030201002,5002,0001,5001,0005000Figure 53.18
    65. 65. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPopulation Cycles: Scientific Inquiry• Some populations undergo regular boom-and-bustcycles• Lynx populations follow the 10-year boom-and-bust cycle of hare populations• Three hypotheses have been proposed to explainthe hare’s 10-year interval© 2011 Pearson Education, Inc.
    66. 66. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsSnowshoe hareLynxYear1850 1875 1900 1925Numberofhares(thousands)Numberoflynx(thousands)160120804009630Figure 53.19
    67. 67. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe human population is no longer growingexponentially but is still increasing rapidly• No population can grow indefinitely, and humansare no exception• The human population increased relatively slowlyuntil about 1650 and then began to growexponentially© 2011 Pearson Education, Inc.
    68. 68. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 53.22The PlagueHumanpopulation(billions)8000BCE4000BCE2000CE1000BCE2000BCE3000BCE1000CE076543210
    69. 69. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• The global population is more than 6.8 billionpeople• Though the global population is still growing, therate of growth began to slow during the 1960s© 2011 Pearson Education, Inc.
    70. 70. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsProjecteddata2009Annualpercentincrease1950 1975 2000 2025 2050Year2.22.01.81.61.41.21.00.80.60.40.20Figure 53.23
    71. 71. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsRegional Patterns of Population Change• To maintain population stability, a regional humanpopulation can exist in one of two configurations– Zero population growth =High birth rate – High death rate– Zero population growth =Low birth rate – Low death rate• The demographic transition is the move from thefirst state to the second state© 2011 Pearson Education, Inc.
    72. 72. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• The demographic transition is associated with anincrease in the quality of health care and improvedaccess to education, especially for women• Most of the current global population growth isconcentrated in developing countries© 2011 Pearson Education, Inc.
    73. 73. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsAge Structure• One important demographic factor in present andfuture growth trends is a country’s age structure• Age structure is the relative number of individualsat each age© 2011 Pearson Education, Inc.
    74. 74. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 53.24Percent of population Percent of population Percent of populationRapid growthAfghanistanSlow growthUnited StatesNo growthItalyMale Male MaleFemale Female FemaleAge85+80–8475–7970–7465–6960–6455–5950–5445–4940–4435–3930–3425–2920–2415–1910–145–90–4Age85+80–8475–7970–7465–6960–6455–5950–5445–4940–4435–3930–3425–2920–2415–1910–145–90–410 0108 8 8 8 886 6 6 6 6 64 4 4 4 4 4222222 00
    75. 75. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Age structure diagrams can predict a population’sgrowth trends• They can illuminate social conditions and help usplan for the future© 2011 Pearson Education, Inc.
    76. 76. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsInfant Mortality and Life Expectancy• Infant mortality and life expectancy at birth varygreatly among developed and developingcountries but do not capture the wide range of thehuman condition© 2011 Pearson Education, Inc.
    77. 77. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsIndus-trializedcountriesIndus-trializedcountriesLess indus-trializedcountriesLess indus-trializedcountriesInfantmortality(deathsper1,000births)Lifeexpectancy(years)6050403020100806040200Figure 53.25
    78. 78. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsGlobal Carrying Capacity• How many humans can the biosphere support?• Population ecologists predict a global populationof 7.8−10.8 billion people in 2050• The carrying capacity of Earth for humans isuncertain• The average estimate is 10-15 billion© 2011 Pearson Education, Inc.
    79. 79. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsLimits on Human Population Size• The ecological footprint concept summarizes theaggregate land and water area needed to sustainthe people of a nation• It is one measure of how close we are to thecarrying capacity of Earth• Countries vary greatly in footprint size andavailable ecological capacity© 2011 Pearson Education, Inc.
    80. 80. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 53.26Gigajoules> 300150–30050–15010–50< 10

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