4Chapter

120 Chapter 4 • Study Guide

Lesson 1 Studying ecology• Ecologists study life at many levels, including individual

organisms, species, populations, communities, ecosystems, and the entire biosphere.

• Ecosystems include both biotic (living) and abiotic (non-living) factors.

• Organisms depend on resources provided by their habitat for survival.

ecology (100) species (101) population (101) community (101) ecosystem (101) biosphere (102) biotic factor (102) abiotic factor (103) habitat (103) resource (103)

Lesson 2 Describing populations• The overall health of a population can often be monitored

by tracking how its size changes.• A population’s density is a measure of how crowded the

population is.• Populations can be distributed randomly, uniformly, or in

clumps. In a random distribution, individual organisms are arranged within a space in no particular pattern. A uniform distribution is one in which individual organisms are evenly spaced. In a clumped distribution, individual organisms arrange themselves according to the availability of resources they need to survive.

• Age structure diagrams show the number of males and females in different age groups within a population.

population size (104) population density (106) population distribution (107) age structure (108) age structure diagram (108) sex ratio (109)

Lesson 3 population Growth• A population’s growth rate is determined by births, deaths,

immigration, and emigration.• Populations can grow exponentially or logistically.

Exponential growth rarely lasts long. The growth of most populations is held at a carrying capacity determined by limiting factors present in the environment.

• Limiting factors and biotic potential regulate a popula-tion’s growth. Limiting factors can be density-dependent, or density-independent.

survivorship curve (111) immigration (112) emigration (112) migration (112) exponential growth (114) limiting factor (115) carrying capacity (115) logistic growth (115) density-dependent factor (116) density-independent factor (116) biotic potential (117)

InquIry LABs And ActIvItIes• Using Mark-and-Recapture Pull “population” samples from a cup of beans and

calculate the total “population” in the cup.• Yeast Population Growth Compare the sizes of yeast populations by counting

cells. Then graph the growth and decline.• Migrating Populations Find out when and where a local migration happens

and how it affects the ecosystem.

Lesson 2 What are the important

characteristics of populations?

Lesson 1 How do ecologists organize

and study life?

Lesson 3 What factors determine whether, and

how, a population’s size changes?

How do changes in population size relate to

environmental conditions?

STUDY RESOURCES

Chapter 4 Self Test • Chapter 4 Worksheets • Chapter 4 Overview Presentation (for PowerPoint)

Population Ecology 121

Review Concepts and Terms 1. A group of individuals that interbreed and produce

fertile offspring is a common definition for a. ecology. b. species. c. population. d. community.

2. An illustration of the Monteverde Cloud Forest is shown below. Which of the following is a biotic factor visible in the image?

a. clouds c. water b. golden toads d. plants

3. Which of the following includes only biotic factors?

a. ecosystem c. biosphere b. habitat d. population

4. Which of the following describes a population that is distributed evenly across an area?

a. random c. clumped b. uniform d. crowded

5. Which of the following is not included in a typical age structure diagram?

a. the population’s sex ratio b. the relative numbers of people in different age

groups c. the population’s historical growth d. the proportion of reproductive-aged

individuals

6. Which of the following terms describes sea-sonal movement of individuals into and out of a population?

a. immigration b. emigration c. natality d. migration

7. Which of the following equations summarizes population growth?

a. immigration – emigration b. (immigration + births) + (emigration + deaths) c. births – deaths d. (immigration + births) – (emigration + deaths)

8. The largest population size a given environment can sustainably support is known as its

a. limiting capacity. c. carrying capacity. b. logistic limit. d. biotic potential.

9. A population that increases 5 percent every year is said to be experiencing

a. exponential growth. c. unlimited growth. b. logistic growth. d. maximum growth.

Modified True/False Write true if the statement is true. If it is false, change the underlined word or words to make the statement true.

10. The primary difference between a community and an ecosystem is that an ecosystem includes biotic factors.

11. A population’s distribution describes how crowded it is.

The Central Case in this chapter focused on the causes of the golden toad extinction. Most people view national parks as an excellent way to protect species and ecosystems. The golden toad, however, lived in a protected reserve and yet still became extinct. Using examples from the Central Case, explain why the golden toad became extinct despite living on a reserve. Finally, suggest other approaches that should be considered when trying to protect organisms.

ANSWERS

Chapter Assessment For answers to the Chapter Assessment, see page A-6 at the back of the book.

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pter

122 Chapter 4 • Assessment

Short Answer 17. Name the different levels of ecological organiza-

tion from largest to smallest. 18. Give an example of how an abiotic factor could

affect organisms within an ecosystem. 19. Why is clumped distribution common in nature? 20. How do scientists calculate population density? 21. What is biotic potential?

Critical Thinking 22. Pose Questions Write a question that a popula-

tion ecologist might ask about the photo below. Then, write a question that an ecosystem ecologist might ask. How are the questions different?

23. Compare and Contrast What is the difference between an organism’s ecosystem and its habitat?

24. Predict A population of mice has a very bottom-heavy age structure diagram. Predict the growth of the population over the next several genera-tions. Explain your prediction.

25. Infer If a population has random distribution, what can you infer about the availability of resources individuals need to survive?

26. Compare and Contrast What is the difference between a type I and type III survivorship curve?

27. Apply Concepts An ecologist is carrying out a population study on songbirds in your area. Over a three-year period, the songbird population increases. In that time, the population’s birthrate was lower than its death rate. How can that be possible if the population size grew?

12. A population of approximately equal numbers of males and females has a balanced sex ratio.

13. Exponential growth curves are generally S shaped.

14. Catastrophic events like floods are density- dependent factors that affect population growth.

Reading Comprehension Read the following selection and answer the questions that follow.In 1906, President Theodore Roosevelt established the Grand Canyon National Game Preserve on the Kaibab Plateau in northern Arizona. The preserve was created to protect deer from hunting and pre-dation, which had reduced the population of Kaibab deer to only about 4000. Hunters were prohibited from shooting deer, but they were allowed to shoot the deer’s predators, including cougars and coyotes. Between 1907 and 1923, over 600 cougars and 3000 coyotes were trapped or killed. As a result, the deer herd began to increase. By 1915, the deer were esti-mated at 25,000; by 1920, at 50,000; and by 1923, at approximately 100,000.

15. If you were to graph the population growth of the Kaibab deer from 1906 to 1923, what would you see?

a. a straight line, showing a steady increase over time

b. a J-shaped upward curve showing a very rapid increase

c. an up-and-down, wavelike pattern d. an S-shaped curve that shows a smooth, rapid

increase leveling off in 1923

16. Deer can live 10 to 25 years. Which of the follow-ing most likely describes an age structure diagram of the Kaibab deer population in 1923?

a. an upside-down triangle, very wide at the top and narrow at the bottom

b. a rectangle, almost the same size from bottom to top

c. a narrow upside-down triangle, a little wider at the top than the bottom

d. a triangle with a very wide base and narrow top

Ecological Footprints

Fruit Fly Population Growth

5

10

15

20

25

30

35

40

10

50

100

200

300

310

320

320

Days Number of Fruit Flies

You (or the average American)

Your class

Your state

United States

Population Pounds of Co�ee Per Day

Pounds of Co�ee Per Year

Data from O’Brien, T.G., and M.F Kinnaird. 2003. Caffeine and conservation. Science 300: 587; and International Coffee Organization.

Population Ecology 123

Read the information below. Copy the table into your notebook and record your calcula-tions. Then, answer the questions that follow.

Coffee is a very economically important crop. In fact, only petroleum is more valuable on the world market. Most coffee is grown in full sun on large tropical plantations where coffee plants are the only species present. Given that an average Ameri-can consumes about 9 pounds of coffee per year, fill in the footprint table. 1. If about 15 billion pounds of coffee are pro-

duced every year, what percent is consumed by the United States?

2. Approximately 2 percent of coffee is shade-grown, meaning that it is grown in groves with many other species. Using your calcu-lated data, approximately how many pounds of coffee consumed in the United States were shade-grown?

3. Shade-grown coffee helps protect tropical habitats because the land doesn’t have to be cleared to grow the coffee plants. Assume that a pound of shade-grown coffee costs $1.50 more than a pound of traditional coffee, and that the added money goes to conservation efforts. If everyone in your state switched to shade-grown coffee for a year, how much money could be generated for conservation?

30. Analyze Graphs What is the approximate car-rying capacity in the fruit fly’s current environ-ment? On approximately which day did the popu-lation reach its carrying capacity?

31. Design an Experiment The ecologist thinks that either space or available food is the main limiting factor controlling population size in the fruit fly experiment. Describe a controlled experiment in which one could determine if food was the limit-ing factor.

Write About It 32. Description Write a paragraph that describes

your habitat. Describe how you obtain the food, water, and shelter you need from your habitat. How does your habitat meet your needs in ways that other habitats do not?

33. Summary How do population ecologists describe populations? Briefly explain each of the charac-teristics of populations outlined in Lesson 2.

34. Apply the BIGQUESTION Differentiate between exponential and logistic growth curves. Give examples of the conditions under which each would occur. Finally, explain how changes to the limiting factors in a community can affect an organism’s population size.

Analyze DataAn ecologist studying fruit flies records the following population size data. Use the data to answer the ques-tions that follow.

28. Graph Make a graph of the data in the table. Be sure to label both axes.

29. Analyze Graphs What pattern of growth is dem-onstrated by this population of fruit flies?