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0133_0137_bi_c07_te 3/10/06 7:01 PM Chapter 5 Study Guide Study Tip Have students work in pairs to review the Key Concepts and the Vocabulary for each section. Students might first quiz each other on the Key Concepts, with one student reading the text statement but omitting the key terms, and the other student supplying the terms. For the first Key Concept in Section 5–1, for example, the first student would say, “The main characteristics of a population are . . .,” and the second student would identify the characteristics. A similar approach can be used to review Vocabulary. Thinking Visually 1. Density-dependent factors 2. Density-independent factors 3. Competition 4. Unusual weather or seasonal cycles Page 134 Chapter 5 Study Guide 5–1 How Populations Grow Key Concepts 5–2 Limits to Growth Key Concepts • Three important characteristics of a population are its geographic distribution, density, and growth rate. • Three factors affect population size: the number of births, the number of deaths, and the number of individuals that enter or leave the population. • Under ideal conditions and unlimited resources, a population will continue to grow in a pattern called exponential growth. As resources are used up and population growth slows or stops, the population exhibits logistic growth. • Density-dependent limiting factors include competition, predation, parasitism, and disease. • Unusual weather, natural disasters, seasonal cycles, and certain human activities—such as damming rivers and clear-cutting forests—are all examples of density-independent limiting factors. Vocabulary population density, p. 119 immigration, p. 120 emigration, p. 120 exponential growth, p. 121 logistic growth, p. 122 carrying capacity, p. 122 5–3 Human Population Growth Key Concepts • Like the populations of many other living organisms, the size of the human population tends to increase with time. • The characteristics of populations, and the social and economic factors that affect them, explain why some countries have high population growth rates while populations of other countries grow slowly or not at all. Chapter 5 Assessment Vocabulary demography, p. 130 demographic transition, p. 130 age-structure diagram, p. 131 Reviewing Content 1. c 2. c 3. b 4. b 5. b 6. a 7. b 8. a 9. d 10. a Thinking Visually Using information from this chapter, complete the following concept map: Understanding Concepts 134 Chapter 5 Populations SECTION RESOURCES Technology: • Teaching Resources, Chapter Vocabulary Review, Graphic Organizer, Chapter 5 Tests: Save Levels A and B e • Computer Test Bank, Chapter 5 Test • iText, Chapter 5 Assessment Tim Print: r 11. The movement of individuals into an area occupied by an existing population is called immigration. Emigration occurs when individuals move out of a population. 12. The graphs should show the characteristic J-shape of exponential population growth as illustrated in Figure 5–3 on page 121. 13. Logistic growth occurs when a population’s growth rate slows or stops following a period of exponential growth. Population growth may slow down when the birthrate decreases or the death rate increases, or when both events occur at the same rate. Population growth may also slow down when the rate of immigration decreases, the rate of emigration increases, or both. 14. Carrying capacity represents the largest number of individuals that a given environment can support. Examples will vary. Vocabulary limiting factor, p. 124 density-dependent limiting factor, p. 125 predator-prey relationship, p. 126 density-independent limiting factor, p. 127 0133_0137_bi_c07_te 3/10/06 7:01 PM Page 135 Chapter 5 Assessment Interactive textbook with assessment at PHSchool.com Reviewing Content Choose the letter that best answers the question or completes the statement. 8. A limiting factor that depends on population size is called a a. density-dependent limiting factor. b. density-independent limiting factor. c. predator-prey relationship. d. parasitic relationship. 1. The number of individuals of a single species per unit area is known as a. carrying capacity. c. population density. b. logistic growth. d. population growth rate. 9. The scientific study of human populations is called a. immigration. b. emigration. c. demographic transition. d. demography. 2. The movement of individuals into an area is called a. demography. c. immigration. b. carrying capacity. d. emigration. 3. The range or area occupied by a population is its a. growth rate. b. geographic distribution. c. age structure. d. population density. 10. The demographic transition is complete when a. population growth stops. b. the birthrate is greater than the death rate. c. the death rate begins to fall. d. the death rate is greater than the birthrate. 4. The graph below represents Number of Individuals Understanding Concepts 11. Distinguish between immigration and emigration. 12. Sketch the exponential growth curve of a hypothetical population. 13. Describe the conditions under which logistic growth occurs. 14. What is carrying capacity? Give an example. 15. How might the introduction of a limiting nutrient in a pond affect the carrying capacity of that pond? Time a. b. c. d. 16. Describe the long-term effects of competition on populations of two different species competing for the same resources. carrying capacity. exponential growth. logistic growth. limiting factors. 17. Describe how a predator-prey relationship can be a mechanism of population control. 5. The maximum number of organisms of a particular species that can be supported by an environment is called a. logistic growth. b. carrying capacity. c. exponential growth. d. population density. 18. How do parasites serve as a density-dependent limiting factor? 19. Explain how density-independent limiting factors can affect populations. 20. How can you account for the fact that the human population has grown more rapidly during the past 500 years than throughout its previous history? 6. If a population grows larger than the carrying capacity of its environment, the a. death rate may rise. b. birthrate may rise. c. death rate may fall. d. immigration rate may increase. 21. What is the significance of the demographic transition in studies of the human population? 7. Density-independent limiting factors include a. predation. c. competition. b. hurricanes. d. parasitism. 23. Explain how a limited resource can affect the survival of a species. Give a specific example. HOMEWORK GUIDE Section 5–1 1–6, 11–14, 28 Section 5–2 7, 8, 15–19, 23–25, 29–31 Sav26, e 27, 32 9, 10, 20–22, e Section 5–3 Tim Questions: r Section: 22. How does the age structure of a population affect its growth rate? Your students can go online to access an interactive version of the Student Edition and a self-test. (Continued from page 134) 15. The addition of a limiting nutrient to a pond would most likely cause an increase in the carrying capacity of those species directly dependent on that nutrient. 16. When two species compete for the same resources, both species are under pressure to change in ways that decrease their competition. Over time, the species may evolve to occupy separate niches. 17. The rise in the population of the prey would normally be followed by a rise in the predator population. As the population of predators rises, the population of prey declines. Since there is less prey available, the population of predators also declines. This cycle repeats itself and functions as a means of population control. 18. Parasites take nourishment from their hosts, often weakening them and causing disease or death. 19. Density-independent factors have similar effects on all individuals in a population regardless of the population’s density. Examples include the effects of a prolonged drought, a killing frost, or a flood. 20. Human population began growing more rapidly 500 years ago due to favorable growth conditions. Agriculture and industry made life easier. The world’s food supply became more reliable. Improved sanitation, medicine, and healthcare dramatically reduced the death rate. Simultaneously, the birthrate remained high. 21. Demographic transition is a prediction of population changes based on an analysis of changes in birthrate and death rate. 22. Populations with nearly equal numbers of people in each age group will have a slow but steady growth rate for the near future. Populations with many more young children than teenagers, and many more teenagers than adults, will grow at a fast rate. 23. A limited resource can affect the survival of a species if that species depends on the resource as part of its habitat. Most students will describe destruction of panda habitat. Populations 135 0133_0137_bi_c07_te 3/10/06 7:01 PM Chapter 5 Assessment Page 136 Chapter 5 Assessment Critical Thinking Critical Thinking 24. Since the communicable virus is more likely to spread when people are crowded together, it is densitydependent. 25. In most cases, it will have a greater effect on the population of a small ecosystem. A small population will be more susceptible to serious damage from a density-independent limiting factor such as a flood or storm. 26. Because there are relatively small numbers of individuals in younger age groups, the population of Sweden is likely to stay about the same or even decline over the next 50 years. 27. The growth curve of a small town made up mostly of senior citizens would show a decline in population. A growth curve of a small town made up of newly married couples would show an increase in population. 28. The carrying capacity of a population is affected by limiting factors such as competition, predation, parasitism, disease, climate, drought, and human disturbances. Likewise, the carrying capacity of a city’s roads depends on such limiting factors as the number and width of roads, the number of intersections, and the number of vehicles traveling on the road. 29. If there is a sudden increase in food for the prey, the population of predators would probably increase as well. An increase in food for prey would allow for a greater number of prey. More predators would then be supported. 30. In parasitic and predator-prey relationships, one member of the relationship benefits, while the other is harmed or killed. 31. The population of fish would most likely decrease due to a decrease in the size of the ecosystem. The decreased size would provide a smaller amount of resources. 32. A demographer would ask questions such as: “Have changes in society, such as access to healthcare and medicines, lowered the death rate?” and “Does the birthrate remain high, or are there signs that the birthrate is falling?” 24. Applying Concepts Why might a contagious virus that causes a fatal disease be considered a density-dependent limiting factor? 30. Comparing and Contrasting How is the relationship between parasites and their hosts similar to a predator-prey relationship? 25. Inferring Would a density-independent limiting factor have more of an effect on population size in a large ecosystem or in a small ecosystem? Explain. 31. Applying Concepts If the water level of a river drops, how might that affect a fish population living in that river? 26. Predicting Study the age-structure diagram for Sweden below. Then, predict how Sweden’s rate of population growth is likely to change over the next 50 years. 32. Asking Questions What questions would a demographer need to answer in order to determine whether a country is approaching the demographic transition? 136 Chapter 5 Age (years) Age-Structure Diagram for Sweden 85+ 80–84 75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 0–4 Males Females 8 7 6 5 4 3 2 10 1 2 3 4 5 6 78 Percentage of Population 27. Comparing and Contrasting Describe the most likely population growth curve you would expect to see in a small town made up mainly of senior citizens. Compare this growth curve to that of a small town made up of newly married couples in their twenties. 28. Using Analogies How is the carrying capacity of a city’s roads similar to the carrying capacity of an ecosystem? 29. Predicting What will happen to a population of predators if there is a sudden increase in food for the prey? Explain. The fertilizer washing into the pond would increase the level of a limiting factor in the pond ecosystem—nitrogen. This would increase the carrying capacity of the pond and probably lead to rapid growth of the algae population. Science, Technology, and Society Nitrogen is a limiting factor in aquatic ecosystems. Suppose that runoff from a field washes nitrogen-rich fertilizer into a pond containing a population of algae. Predict how the fertilizer will affect the carrying capacity of the pond for algae. Refer to the information on limiting nutrients in Section 3–3. Write a paragraph on populations. Include the characteristics of a population, factors that affect its size, and the changes in the size of the human population from about 500 years ago to the present. Give a projection on how large the world population might be in the year 2050 and on how the growth rate in 2050 might compare to that in 2000. (Hint: Outline your ideas before you begin to write.) Performance-Based Assessment Multimedia Presentation Create a visual presentation that describes how limiting factors regulate population growth. Be sure to distinguish between density-dependent limiting factors and densityindependent limiting factors. For: An interactive self-test Visit: PHSchool.com Web Code: cba-2050 Students’ paragraphs will vary. All should include mention of population density; carrying capacity; types of growth; and limiting factors, both densitydependent and density-independent. Students should also describe changes in the human population, drawing upon the text and figures in Section 5–3 for support for their descriptions. Using data in Figure 5–14, students should note that the projected population in 2050 is 9,078,850,714 and that the growth rate in 2050 is projected to be 0.43 percent annually, compared with an average annual growth rate of 1.23 percent in 2000.