1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell & Jane Reece Lectures by Chris Romero Chapter 52 pop Ecology

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: Earth’s Fluctuating pop's To understand human pop growth, we must consider general principles of pop ecology

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings pop ecology- study of pop’s in relation to environ, including density & distribution, age structure, & pop size The fur seal pop of St. Paul Island, off the coast of Alaska, has experienced dramatic fluctuations in size

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5. Concept 52.1: Dynamic biological processes influence pop density, dispersion, & demography pop-grp of indiv's of 1 spp living in the same general area

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Density & Dispersion Density- # of indiv's per unit area or volume Dispersion- pattern of spacing among indiv's w/in the boundaries of the pop

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Density: A Dynamic Perspective Determining the density of natural pop's is difficult In most cases, it is impractical or impossible to count all indiv's in a pop Density is the result of an interplay b/w processes that add indiv's to a pop & those that remove indiv's

8. LE 52-2 pop size Emigration Deaths Immigration Births

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Patterns of Dispersion Environmental & social factors influence spacing of indiv's in a pop

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings clumped dispersion - indiv's aggregate in patches A clumped dispersion may be influenced by resource availability & behavior Video: Flapping Geese (clumped) Video: Flapping Geese (clumped)

11. LE 52-3a Clumped. For many animals, such as these wolves, living in groups ↑'s the effectiveness of hunting, spreads the work of protecting & caring for young, & helps exclude other indiv's from their territory.

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings uniform dispersion- indiv's are evenly distributed It may be influenced by social interactions such as territoriality Video: Albatross Courtship (uniform) Video: Albatross Courtship (uniform)

13. LE 52-3b Uniform. Birds nesting on small islands, such as these king penguins on South Georgia Island in the South Atlantic Ocean, often exhibit uniform spacing, maintained by aggressive interactions b/w neighbors.

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings random dispersion- position of each indiv is independent of other indiv's Video: Prokaryotic Flagella (Salmonella typhimurium) (random) Video: Prokaryotic Flagella (Salmonella typhimurium) (random)

15. LE 52-3c Random. Dandelions grow from windblown seeds that land at random & later germinate.

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Demography Demography- study of the vital statistics of a pop & how they change over time Death rates & birth rates are of particular interest to demographers

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Life Tables A life table is an age-specific summary of the survival pattern of a pop It is best made by following the fate of a cohort The life table of Belding’s ground squirrels reveals many things about this pop

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19. Survivorship Curves A survivorship curve is a graphic way of representing the data in a life table The survivorship curve for Belding’s ground squirrels shows a relatively constant death rate

20. LE 52-4 Males Females 10 Age (years) # of survivors (log scale) 4 6 8 0 2 1,000 100 10 1

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Survivorship curves can be classified into 3 general types: Type I, Type II, & Type III

22. LE 52-5 III II 100 Percentage of maximum life span # of survivors (log scale) 0 50 1,000 100 10 1 I

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reproductive Rates A reproductive table, or fertility schedule, is an age-specific summary of the reproductive rates in a pop It describes reproductive patterns of a pop

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25. Concept 52.2: Life history traits are products of natural selection Life history traits are evolutionary outcomes reflected in the development, physiology, & behavior of an organism

26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Life History Diversity Life histories are very diverse Semelparity- “big-bang” reproduction, reproduce once & die Iteroparity- repeated reproduction, produce offspring repeatedly

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28. “Trade-offs” & Life Histories Organisms have finite resources, which may lead to trade-offs b/w survival & reproduction

29. LE 52-7 Female Parents surviving the following winter (%) Normal brood size 100 80 60 0 Reduced brood size Enlarged brood size Male 40 20

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some plants produce a lg # of small seeds, ensuring that at least some of them will grow & eventually reproduce

31. LE 52-8a Most weedy plants, such as this dandelion, grow quickly & produce a large # of seeds, ensuring that at least some will grow into plants & eventually produce seeds themselves.

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Other types of plants produce a moderate # of lg seeds that provide a lg store of energy that will help seedlings become established

33. LE 52-8b Some plants, such as this coconut palm, produce a moderate # of very large seeds. The large endosperm provides nutrients for the embryo, an adaptation that helps ensure the success of a relatively large fraction of offspring.

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In animals, parental care of smaller broods may facilitate survival of offspring

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 52.3: The exponential model describes pop growth in an idealized, unlimited environ It is useful to study pop growth in an idealized situation Idealized situations help us understand the capacity of spp to ↑ & the cond’s that may facilitate this growth

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Per Capita Rate of ↑ If immigration & emigration are ignored, a population’s growth rate (per capita ↑ ) equals birth rate minus death rate

37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Zero pop growth occurs when the birth rate equals the death rate Most ecologists use differential calculus to express pop growth as growth rate at a particular instant in time: dN dt  rN

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Exponential Growth Exponential pop growth- pop ↑ under idealized cond’s; J-shaped curve Under these cond’s, the rate of reproduction is at its maximum, called the intrinsic rate of ↑

39. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Equation of exponential pop growth: dN dt  r max N

40. LE 52-9 # of generations pop size (N) 2,000 = 1.0N 1,000 1,500 500 0 15 10 5 0 dN dt = 0.5N dN dt

41. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The J-shaped curve of exponential growth characterizes some rebounding pop's

42. LE 52-10 Year Elephant pop 8,000 4,000 6,000 2,000 0 1980 1960 1940 1920 1900

43. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 52.4: The logistic growth model includes the concept of carrying capacity Exponential growth cannot be sustained for long in any pop A more realistic pop model limits growth by incorporating carrying capacity

44. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Carrying capacity (K)- max pop size the environ can support

45. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Logistic Growth Model logistic pop growth model- per capita rate of ↑ declines as carrying capacity is reached; sigmoid (S-shaped) curve We construct the logistic model by starting w/ the exponential model & adding an expression that reduces per capita rate of ↑ as N ↑'s

46. LE 52-11 pop size (N) Per capita rate of ↑ (r) Maximum Positive Negative N = K 0

47. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The logistic growth equation includes K, the carrying capacity dN dt  ( K  N ) K r max N

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49. LE 52-12 # of generations pop size (N) K = 1,500 1,500 2,000 1,000 500 15 10 5 0 0 Logistic growth Exponential growth = 1.0N dN dt = 1.0N dN dt 1,500 – N 1,500

50. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Logistic Model & Real pop's The growth of laboratory pop's of paramecia fits an S-shaped curve

51. LE 52-13a Time (days) # of Paramecium/mL 1,000 0 400 5 200 10 0 15 800 600 A Paramecium pop in the lab

52. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some pop's overshoot K before settling down to a relatively stable density

53. LE 52-13b Time (days) # of Daphnia/50 mL 180 0 90 20 60 40 0 60 150 120 A Daphnia pop in the lab 30 80 100 120140 160

54. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some pop's fluctuate greatly around K

55. LE 52-13c Time (years) # of females 80 1975 1980 40 1985 0 1990 60 A song sparrow pop in its natural habitat 20 1995 2000

56. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The logistic model fits few real pop's but is useful for estimating possible growth

57. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Logistic Model & Life Histories Life history traits favored by natural selection may vary w/ pop density & environmental cond’s K-selection/density-dependent selection- selects for life history traits that are sensitive to pop density r-selection/density-independent selection- selects for life history traits that max reproduction

58. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The concepts of K-selection & r-selection are somewhat controversial & have been criticized by ecologists as oversimplifications

59. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 52.5: pop's are regulated by a complex interaction of biotic & abiotic influences There are 2 general questions about regulation of pop growth: – What environmental factors stop a pop from growing? – Why do some pop's show radical fluctuations in size over time, while others remain stable?

60. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings pop Change & pop Density In density-independent pop's, birth rate & death rate do not change w/ pop density In density-dependent pop's, birth rates fall & death rates rise w/ pop density

61. LE 52-14 pop density Equilibrium density Density- independent birth rate Density-dependent death rate pop density Equilibrium density Density- independent death rate Density-dependent birth rate pop density Equilibrium density Density- dependent death rate Density-dependent birth rate per capita Birth or death rate

62. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Density-Dependent pop Regulation Density-dependent birth & death rates are an example of negative feedback that regulates pop growth Density dependent limiting factors- affected by competition for resources, territoriality, health, predation, toxic wastes, & intrinsic factors

63. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Competition for Resources In crowded pop's, increasing pop density intensifies intraspecific competition for resources

64. LE 52-15 10,000 Average # of seeds per reproducing individual (log scale) 1,000 100 10 1 Plants per m 2 (log scale) Plantain. The # of seeds produced by plantain (Plantago major) decreases as density ↑'s. Song sparrow. Clutch size in the song sparrow on Mandarte Island, British Columbia, decreases as density ↑'s & food is in short supply. Average clutch size 2.8 80 Females per unit area 3.0 3.8 4.0 3.4 3.6 3.2 60 70 50 30 40 20 0 10

65. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Territoriality In many vertebrates & some invertebrates, territoriality may limit density

66. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cheetahs are highly territorial, using chemical communication to warn other cheetahs of their boundaries

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68. Oceanic birds exhibit territoriality in nesting behavior

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70. Health pop density can influence the health & survival of organisms In dense pop's, pathogens can spread more rapidly

71. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Predation As a prey pop builds up, predators may feed preferentially on that spp

72. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Toxic Wastes Accumulation of toxic wastes can contribute to density-dependent regulation of pop size

73. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Intrinsic Factors For some pop's, intrinsic (physiological) factors appear to regulate pop size **for example, white-footed mice stop reproduction when the pop density gets high, this is apparently due to aggressive interactions that increase w/pop density (even when there is abundant food & shelter) * scientists are not sure what is the mechanism by which aggression affects reproductive rate

74. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Density independent limiting factors- Natural disasters, weather, damming rivers, etc….

75. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings pop Dynamics The study of pop dynamics focuses on the complex interactions b/w biotic & abiotic factors that cause variation in pop size

76. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Stability & Fluctuation Long-term pop studies have challenged the hypothesis that pop's of large mammals are relatively stable over time

77. LE 52-18 1960 Year Moose pop size 2,500 Steady decline probably caused largely by wolf predation 2,000 1,500 1,000 500 0 1970 1980 1990 2000 Dramatic collapse caused by severe winter weather & food shortage, leading to starvation of more than 75% of the pop

78. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Extreme fluctuations in pop size are typically more common in invertebrates than in large mammals

79. LE 52-19 1960 Year Commercial catch (kg) of male crabs (log scale) 730,000 100,000 10,000 1970 1980 1990 1950

80. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Metapopulations & Immigration Metapopulations are groups of pop's linked by immigration & emigration High levels of immigration combined w/ higher survival can result in greater stability in pop's

81. LE 52-20 1988 Year # of breeding females 60 1989 1990 1991 Small islands Mandarte Island 50 40 30 20 10 0

82. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Many pop's undergo boom-&-bust cycles Boom-&-bust cycles are influenced by complex interactions b/w biotic & abiotic factors

83. LE 52-21 Year Hare pop size (thousands) 1850 Snowshoe hare 0 1875 1900 1925 40 80 120 160 Lynx pop size (thousands) Lynx 0 3 6 9

84. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 52.6: Human pop growth has slowed after centuries of exponential ↑ No pop can grow indefinitely, & humans are no exception

85. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Global Human pop The human pop increased relatively slowly until about 1650 & then began to grow exponentially

86. LE 52-22 8000 B.C. Human pop (billions) 6 5 4 3 2 1 0 4000 B.C. 3000 B.C. 2000 B.C. 1000 B.C. The Plague 0 1000 A.D. 2000 A.D.

87. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Though the global pop is still growing, the rate of growth began to slow about 40 years ago

88. LE 52-23 Annual percent ↑ 2.2 2 1.8 1.6 1.4 1.2 1 2003 2050 Year 2025 2000 1975 1950 0.8 0.6 0.4 0.2 0

89. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Regional Patterns of pop Change To maintain pop stability, a regional human pop can exist in one of 2 configurations: – Zero pop growth = High birth rate – High death rate – Zero pop growth = Low birth rate – Low death rate The demographic transition is the move from the 1 st state toward the 2 nd state

90. LE 52-24 Birth or death rate per 1,000 people 50 40 30 20 10 Sweden 2050 Year 20001900 1950 1850 0 1800 1750 Birth rate Death rate Mexico Birth rate Death rate

91. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The demographic transition is associated w/ various factors in developed & developing countries

92. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Age Structure One important demographic factor in present & future growth trends is a country’s age structure Age structure- relative # of indiv's at each age It is commonly represented in pyramids

93. LE 52-25 Rapid growth Afghanistan Age Male Percent of pop Female 86 42 24 68 0 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 0–4 85+ 80–84 75–79 70–74 65–69 60–64 55–59 50–54 Slow growth United States Age Male Percent of pop Female 6 42 24 68 0 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 0–4 85+ 80–84 75–79 70–74 65–69 60–64 55–59 50–54 8 Decrease Italy Male Percent of pop Female 6 42 24 68 0 8

94. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Age structure diagrams can predict a population’s growth trends They can illuminate social conditions & help us plan for the future

95. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Infant Mortality & Life Expectancy Infant mortality & life expectancy at birth vary greatly among developed & developing countries but do not capture the wide range of the human condition

96. LE 52-26 Infant mortality (deaths per 1,000 births) 50 40 30 20 10 0 Developed countries 60 Developing countries Life expectancy (years) 80 40 20 0 Developed countries 60 Developing countries

97. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Global Carrying Capacity How many humans can the biosphere support?

98. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Estimates of Carrying Capacity The carrying capacity of Earth for humans is uncertain

99. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ecological Footprint The ecological footprint concept summarizes the aggregate land & water area needed to sustain the people of a nation It is one measure of how close we are to the carrying capacity of Earth Countries vary greatly in footprint size & available ecological capacity

100. LE 52-27 Ecological footprint (ha per person) 14 12 10 8 6 4 16 0 2 0 24 6 8 1012 14 16 Available ecological capacity (ha per person) New Zealand Australia Canada Sweden World China India Spain UK Japan Germany Norway USA Netherlands

101. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings At more than 6 billion people, the world is already in ecological deficit