1. End Show Slide 1 of 22 Copyright Pearson Prentice Hall Biology

2. End Show Slide 2 of 22 Copyright Pearson Prentice Hall 5-1 How Populations Grow

3. End Show 5-1 How Populations Grow Slide 3 of 22 Characteristics of Populations What characteristics are used to describe a population? Copyright Pearson Prentice Hall

4. End Show 5-1 How Populations Grow Slide 4 of 22 Copyright Pearson Prentice Hall Characteristics of Populations Three important characteristics of a population are its: geographic distribution population density growth rate

5. End Show 5-1 How Populations Grow Slide 5 of 22 Population Growth What factors affect population size? Copyright Pearson Prentice Hall

6. End Show 5-1 How Populations Grow Slide 6 of 22 Copyright Pearson Prentice Hall Population Growth Three factors can affect population size: the number of births the number of deaths the number of individuals that enter or leave the population A population can grow when its birthrate is greater than its death rate.

7. End Show 5-1 How Populations Grow Slide 7 of 22 Population Growth Immigration, the movement of individuals into an area, is another factor that can cause a population to grow. Emigration, the movement of individuals out of an area, can cause a population to decrease in size. Copyright Pearson Prentice Hall

8. End Show 5-1 How Populations Grow Slide 8 of 22 Exponential Growth What are exponential growth and logistic growth? Copyright Pearson Prentice Hall

9. End Show 5-1 How Populations Grow Slide 9 of 22 Copyright Pearson Prentice Hall Exponential Growth Under ideal conditions with unlimited resources, a population will grow exponentially. Exponential growth occurs when the individuals in a population reproduce at a constant rate. The population becomes larger and larger until it approaches an infinitely large size.

10. End Show 5-1 How Populations Grow Slide 10 of 22 Exponential Growth Copyright Pearson Prentice Hall Exponential Growth

11. End Show 5-1 How Populations Grow Slide 11 of 22 Copyright Pearson Prentice Hall Logistic Growth As resources become less available, the growth of a population slows or stops. Logistic growth occurs when a population's growth slows or stops following a period of exponential growth.

12. End Show 5-1 How Populations Grow Slide 12 of 22 Logistic Growth Logistic growth is characterized by an S- shaped curve. Copyright Pearson Prentice Hall

13. End Show 5-1 How Populations Grow Slide 13 of 22 Limiting Factors What factors limit population growth? Copyright Pearson Prentice Hall

14. End Show 5-1 How Populations Grow Slide 14 of 22 Density-Dependent Factors Copyright Pearson Prentice Hall Wolf and Moose Populations on Isle Royale Moose Wolves Moose Wolves Density-Dependent Activity Density-Dependent Activity

15. End Show - or - Continue to: Click to Launch: Slide 15 of 22 Copyright Pearson Prentice Hall 5-1

16. End Show Slide 16 of 22 Copyright Pearson Prentice Hall 5-1 Population density is the number of individuals a.that are born each year. b.per unit area. c.that immigrate. d.that emigrate.

17. End Show Slide 17 of 22 Copyright Pearson Prentice Hall 5-1 When the birthrate of a population exceeds its death rate, the population a.decreases. b.increases. c.stays the same. d.increases then decreases.

18. End Show Slide 18 of 22 Copyright Pearson Prentice Hall 5-1 An S-shaped curve on a graph of population growth is characteristic of a.exponential growth. b.logistic growth. c.carrying capacity. d.delayed growth.

19. End Show Slide 19 of 22 Copyright Pearson Prentice Hall 5-1 Exponential growth in a population slows down or stops as a.resources become limited. b.rate of immigration increases. c.rate of emigration decreases. d.birth rate increases.

20. End Show Slide 20 of 22 Copyright Pearson Prentice Hall 5-1 Exponential growth rate means that each new generation of a population a.adds the same number of new individuals as the previous generation did. b.increases at the same rate as the previous generation. c.is the same size as the generation before. d.increases by a varying amount.

21. End Show Slide 21 of 22 Copyright Pearson Prentice Hall 5-2 Limits to Growth

22. End Show Slide 22 of 22 Copyright Pearson Prentice Hall Limiting Factors –What factors limit population growth?

23. End Show Slide 23 of 22 Copyright Pearson Prentice Hall Limiting Factors The primary productivity of an ecosystem can be reduced when there is an insufficient supply of a particular nutrient. Ecologists call such substances limiting nutrients.

24. End Show Slide 24 of 22 Copyright Pearson Prentice Hall Limiting Factors A limiting nutrient is an example of a more general ecological concept: a limiting factor. In the context of populations, a limiting factor is a factor that causes population growth to decrease.

25. End Show Slide 25 of 22 Copyright Pearson Prentice Hall Density-Dependent Factors A limiting factor that depends on population size is called a density- dependent limiting factor.

26. End Show Slide 26 of 22 Copyright Pearson Prentice Hall Density-Dependent Factors –Density-dependent limiting factors include: competition predation parasitism disease

27. End Show Slide 27 of 22 Copyright Pearson Prentice Hall Density-Dependent Factors –Density-dependent factors operate only when the population density reaches a certain level. These factors operate most strongly when a population is large and dense. –They do not affect small, scattered populations as greatly.

28. End Show Slide 28 of 22 Copyright Pearson Prentice Hall Density-Dependent Factors –Competition When populations become crowded, organisms compete for food, water space, sunlight and other essentials. Competition among members of the same species is a density-dependent limiting factor.

29. End Show Slide 29 of 22 Copyright Pearson Prentice Hall Density-Dependent Factors Competition can also occur between members of different species. This type of competition can lead to evolutionary change. Over time, the species may evolve to occupy different niches.

30. End Show Slide 30 of 22 Copyright Pearson Prentice Hall Density-Dependent Factors –Predation Populations in nature are often controlled by predation. The regulation of a population by predation takes place within a predator- prey relationship, one of the best-known mechanisms of population control.

31. End Show Slide 31 of 22 Copyright Pearson Prentice Hall Density-Dependent Factors Wolf and Moose Populations on Isle Royale Moose Wolves

32. End Show Slide 32 of 22 Copyright Pearson Prentice Hall Density-Dependent Factors –Parasitism and Disease Parasites can limit the growth of a population. A parasite lives in or on another organism (the host) and consequently harms it.

33. End Show Slide 33 of 22 Copyright Pearson Prentice Hall Density-Independent Factors Density-independent limiting factors affect all populations in similar ways, regardless of the population size.

34. End Show Slide 34 of 22 Copyright Pearson Prentice Hall Density-Independent Factors –Examples of density- independent limiting factors include: unusual weather natural disasters seasonal cycles certain human activities—such as damming rivers and clear-cutting forests

35. End Show Slide 35 of 22 Copyright Pearson Prentice Hall 5-2

36. End Show Slide 36 of 22 Copyright Pearson Prentice Hall 5-2 –A limiting factor that affects all populations in similar ways regardless of their size might be drought. disease. predation. crowding.

37. End Show Slide 37 of 22 Copyright Pearson Prentice Hall 5-2 –Which of the following would be a limiting factor affecting the panda population of China? programs that educate people about endangered species capture of some pandas for placement in zoos laws protecting habitat destruction a disease that kills bamboo plants

38. End Show Slide 38 of 22 Copyright Pearson Prentice Hall 5-2 –Density-dependent factors operate most strongly when a population is large and dense. large but sparse. small and sparse. small, but growing.

39. End Show Slide 39 of 22 Copyright Pearson Prentice Hall 5-2 –Within a limited area, if the population of a predator increases, the population of its prey is likely to increase. decrease. remain about the same. become extinct.

40. End Show Slide 40 of 22 Copyright Pearson Prentice Hall 5-2 –Which of the following is a density-independent factor affecting populations? predation disease a destructive hurricane parasites

41. End Show Slide 41 of 22 Copyright Pearson Prentice Hall 5-3 Human Population Growth

42. End Show Slide 42 of 22 Copyright Pearson Prentice Hall Historical Overview –How has the size of the human population changed over time?

43. End Show Slide 43 of 22 Copyright Pearson Prentice Hall Historical Overview –Like the populations of many other living organisms, the size of the human population tends to increase with time. –For most of human existence, the population grew slowly. –Limiting factors kept population sizes low.

44. End Show Slide 44 of 22 Copyright Pearson Prentice Hall Historical Overview About 500 years ago, the human population began growing more rapidly. Life was made easier and safer by advances in agriculture and industry. Death rates were dramatically reduced due to improved sanitation, medicine, and healthcare, while birthrates remained high.

45. End Show Slide 45 of 22 Copyright Pearson Prentice Hall Historical Overview With these advances, the human population experienced exponential growth. Human Population Growth

46. End Show Slide 46 of 22 Copyright Pearson Prentice Hall Patterns of Population Growth The scientific study of human populations is called demography. Demography examines the characteristics of human populations and attempts to explain how those populations will change over time.

47. End Show Slide 47 of 22 Copyright Pearson Prentice Hall Patterns of Population Growth –Why do population growth rates differ in countries throughout the world?

48. End Show Slide 48 of 22 Copyright Pearson Prentice Hall Patterns of Population Growth –Birthrates, death rates, and the age structure of a population help predict why some countries have high growth rates while other countries grow more slowly.

49. End Show Slide 49 of 22 Copyright Pearson Prentice Hall Patterns of Population Growth –The Demographic Transition Over the past century, population growth in the United States, Japan, and much of Europe has slowed dramatically. According to demographers, these countries have completed the demographic transition, a dramatic change in birth and death rates.

50. End Show Slide 50 of 22 Copyright Pearson Prentice Hall Patterns of Population Growth The demographic transition has three stages. In stage 1, there are high death rates and high birthrates. In stage 2, the death rate drops, while the birthrate remains high. The population increases rapidly. In stage 3, the birthrate decreases, causing population growth to slow.

51. End Show Slide 51 of 22 Copyright Pearson Prentice Hall Patterns of Population Growth The demogra phic transitio n is complete when the birthrate falls to meet the death rate, and populati on growth stops.

52. End Show Slide 52 of 22 Copyright Pearson Prentice Hall Patterns of Population Growth –Age Structure Population growth depends, in part, on how many people of different ages make up a given population. Demographers can predict future growth using models called age-structure diagrams. Age-structure diagrams show the population of a country broken down by gender and age group.

53. End Show Slide 53 of 22 Copyright Pearson Prentice Hall Patterns of Population Growth In the United States, there are nearly equal numbers of people in each age group. This age structure diagram predicts a slow but steady growth rate for the near future. Males Females 8 6 4 2 0 2 4 6 8 Percentage of Population 80+ 60–64 20–24 0–4 40–44 Age (years) U.S. Population

54. End Show Slide 54 of 22 Copyright Pearson Prentice Hall Patterns of Population Growth In Rwanda, there are many more young children than teenagers, and many more teenagers than adults. This age structure diagram predicts a population that will double in about 30 years. 80+ 60–64 20–24 0–4 Age (years) Males Females Rwandan Population 40–44 Percentage of Population

55. End Show Slide 55 of 22 Copyright Pearson Prentice Hall Future Population Growth To predict human population growth, demographers must consider the age structure of each country, as well as the prevalence of life-threatening diseases. If growing countries move toward the demographic transition, growth rate may level off or decrease.

56. End Show Slide 56 of 22 Copyright Pearson Prentice Hall Future Population Growth

57. End Show Slide 57 of 22 Copyright Pearson Prentice Hall Future Population Growth Ecologists suggest that if growth does not slow down, there could be serious damage to the environment and global economy. Economists assert that science, technology, and changes in society may control the negative impact of population growth.

58. End Show Slide 58 of 22 Copyright Pearson Prentice Hall 5-3

59. End Show Slide 59 of 22 Copyright Pearson Prentice Hall 5-3 –The size of the human population began to increase exponentially after the bubonic plague. development of plowing and irrigation. Industrial Revolution. development of the first cities.

60. End Show Slide 60 of 22 Copyright Pearson Prentice Hall 5-3 –Which of the following is NOT a potential limiting factor of human population growth? famine medicine war disease

61. End Show Slide 61 of 22 Copyright Pearson Prentice Hall 5-3 –After the demographic transition is complete, a population grows rapidly. grows slowly. begins a period of rapid decline. stays about the same size as time passes.

62. End Show Slide 62 of 22 Copyright Pearson Prentice Hall 5-3 –An age-structure diagram shows a breakdown of a population by location and age group. age group and gender. birthrate and death rate. age group and emigration rate.

63. End Show Slide 63 of 22 Copyright Pearson Prentice Hall 5-3 –Since the mid-1960s, the average annual growth rate of the human population has remained about the same. failed to show a consistent pattern. increased. decreased.