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

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Population ecology is the study of populations in relation to environment, including environmental influences on density and distribution, age structure, and population size

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 52.1: Dynamic biological processes influence population density, dispersion, and demography A population is a group of individuals of a single species living in the same general area

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Density and Dispersion Density is the number of individuals per unit area or volume Dispersion is the pattern of spacing among individuals within the boundaries of the population

5. LE 52-2 Population size Emigration Deaths Immigration Births Population Dynamics

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In a clumped dispersion, individuals aggregate in patches A clumped dispersion may be influenced by resource availability and behavior Video: Flapping Geese (clumped) Video: Flapping Geese (clumped)

7. LE 52-3a Clumped. For many animals, such as these wolves, living in groups increases the effectiveness of hunting, spreads the work of protecting and caring for young, and helps exclude other individuals from their territory.

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A uniform dispersion is one in which individuals are evenly distributed It may be influenced by social interactions such as territoriality Video: Albatross Courtship (uniform) Video: Albatross Courtship (uniform)

9. 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 between neighbors.

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In a random dispersion, the position of each individual is independent of other individuals Video: Prokaryotic Flagella (Salmonella typhimurium) (random) Video: Prokaryotic Flagella (Salmonella typhimurium) (random)

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

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

13. 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 population

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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

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

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Survivorship curves can be classified into three general types: Type I, Type II, and Type III III II 100 Percentage of maximum life span Number of survivors (log scale) 0 50 1,000 100 10 1 I

17. 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 population It describes reproductive patterns of a population

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Per Capita Rate of Increase If immigration and emigration are ignored, a population’s growth rate (per capita increase) equals birth rate minus death rate Birth – Death = growth rate Zero population growth occurs when the birth rate equals the death rate

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Exponential Growth Exponential population growth is population increase under idealized conditions Under these conditions, the rate of reproduction is at its maximum, called the intrinsic rate of increase

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Exponential population growth results in a J- shaped curve Number of generations Population size (N) 2,000 = 1.0N 1,000 1,500 500 0 15 10 5 0 dN dt = 0.5N dN dt

21. LE 52-10 Year Elephant population 8,000 4,000 6,000 2,000 0 1980 1960 1940 1920 1900 The J-shaped curve of exponential growth characterizes some rebounding populations

22. 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 population A more realistic population model limits growth by incorporating carrying capacity Carrying capacity (K) is the maximum population size the environment can support

23. LE 52-11 Population size (N) Per capita rate of increase (r) Maximum Positive Negative N = K 0

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The logistic model of population growth produces a sigmoid (S-shaped) curve Number of generations Population 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

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

26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some populations overshoot K before settling down to a relatively stable density Time (days) Number of Daphnia/50 mL 180 0 90 20 60 40 0 60 150 120 A Daphnia population in the lab 30 80 100 120140 160

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

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Logistic Model and Life Histories Life history traits favored by natural selection may vary: K-selection, or density-dependent selection, selects for life history traits that are sensitive to population density r-selection, or density-independent selection, selects for life history traits that maximize reproduction

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

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Population Change and Population Density In density-independent populations, birth rate and death rate do not change with population density In density-dependent populations, birth rates fall and death rates rise with population density

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

32. LE 52-15 10,000 Average number of seeds per reproducing individual (log scale) 1,000 100 10 1 Plants per m 2 (log scale) Plantain. The number of seeds produced by plantain (Plantago major) decreases as density increases. Song sparrow. Clutch size in the song sparrow on Mandarte Island, British Columbia, decreases as density increases and 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

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

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Oceanic birds exhibit territoriality in nesting behavior

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Other Factors Health Predation Toxic Wastes

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Many populations undergo boom-and-bust cycles Boom-and-bust cycles are influenced by complex interactions between biotic and abiotic factors

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

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Global Human Population The human population increased relatively slowly until about 1650 and then began to grow exponentially 8000 B.C. Human population (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.

39. LE 52-23 Annual percent increase 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

40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Regional Patterns of Population Change To maintain population stability, a regional human population 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 the first state toward the second state

41. 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

42. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Age Structure One important demographic factor in present and future growth trends is a country’s age structure Age structure is the relative number of individuals at each age It is commonly represented in pyramids

43. LE 52-25 Rapid growth Afghanistan Age Male Percent of population 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 population 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 population Female 6 42 24 68 0 8

44. 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

45. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ecological Footprint The ecological footprint concept summarizes the aggregate land and 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 and available ecological capacity

46. 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