1. Chapter 42 Opener

2. Concept 42.1 Ecological Systems Vary in Space and over Time
Discuss the validity of the following statement:
Ecological systems at the organism, population, community, and ecosystem scales differ from one another only with respect to geographic scale (size of land area or water volume involved). 2

3. Figure 42.1 The Hierarchy of Ecological Systems

4. Concept 42.1 Ecological Systems Vary in Space and over Time
Ecological systems at the organism, population, community, and ecosystem scales differ from one another only with respect to geographic scale (size of land area or water volume involved).
a. True
b. False
c. I don’t understand this question.
Answer: b
(These do generally differ in geographic scale, but the other essential difference lies in the interacting components included in the system: at the organism level, the system consists of a single individual and the immediate biotic and abiotic environment with which it interacts; at the population level, the system contains a population of one species plus the biotic and abiotic environment with which the population interacts; at the community level the system contains multiple interacting species plus their abiotic environment; and at the biosphere level, the system contains all of the communities on Earth and the abiotic environment with which they interact.)
INSTRUCTOR NOTE:
Note that the term “ecosystem” has two modern meanings: as a contraction of “ecological system” and as an ecological system at the community and larger scale.
[NOTE TO THE INSTRUCTOR: It can be useful to include an “I don’t know” or “I don’t understand this question” choice with clickers, because it can help you discover how many students really haven’t understood the concept at all. Use of this option may depend on whether you assign participation-only points or performance points (or some combination) to clicker questions in your course. If you only assign participation points, it may be useful to leave the “I don't know” choice in the question, as it gives students a penalty-free way of indicating that more time may be needed on this concept.] 4

5. Figure 42.2 The Microbial Community of the Human Gut Depends on the Host’s Diet

6. Figure 42.2 The Microbial Community of the Human Gut Depends on the Host’s Diet

7. Figure 42.2 The Microbial Community of the Human Gut Depends on the Host’s Diet (Part 1)

8. Figure 42.2 The Microbial Community of the Human Gut Depends on the Host’s Diet (Part 2)

9. c. I don’t understand this question.
Concept Climate and Topography Shape Earth’s Physical Environments
High latitudes are cooler than low latitudes because as a result of Earth’s spherical shape, high latitudes are farther away from the sun than low latitudes.
a. True
b. False
c. I don’t understand this question.
Answer: b
(Latitudinal gradients in temperature are caused by latitudinal gradients in total input of solar energy. Low latitudes near the Equator receive more solar energy because the sun’s rays strike Earth’s surface at a more perpendicular angle at the equator than at high latitudes and travel through less radiation-absorbing atmosphere.)
[NOTE TO THE INSTRUCTOR: It can be useful to include an “I don’t know” or “I don’t understand this question” choice with clickers, because it can help you discover how many students really haven’t understood the concept at all. Use of this option may depend on whether you assign participation-only points or performance points (or some combination) to clicker questions in your course. If you only assign participation points, it may be useful to leave the “I don't know” choice in the question, as it gives students a penalty-free way of indicating that more time may be needed on this concept.] 9

10. Discuss the validity of the following statement:
Concept Climate and Topography Shape Earth’s Physical Environments
Discuss the validity of the following statement:
High latitudes are cooler than low latitudes because as a result of Earth’s spherical shape, high latitudes are farther away from the sun than low latitudes. 10

11. Figure 42.3 Solar Energy Input Varies with Latitude

12. Figure 42.3 Solar Energy Input Varies with Latitude

13. c. I don’t understand the question.
Concept Climate and Topography Shape Earth’s Physical Environments
Winter and summer seasons occur because Earth is farther from the sun in winter and closer to it in summer.
a. True
b. False
c. I don’t understand the question.
Answer: b
INSTRUCTOR NOTES:
Students should refer to Figure 42.4 of the textbook.
From page 825: “Seasonality occurs because Earth’s axis of rotation is tilted at an angle of approximately 23.5 degrees relative to its orbit around the sun. This tilt causes different latitudes to receive their greatest solar energy input at different times during the yearly orbit, in a yearly cycle of solstice and equinox. In late June of every year, the North Pole tilts toward the sun, and the sun is directly over the Tropic of Cancer (latitude 23.5°N). At this time the Northern Hemisphere is basking in the long, warm days of summer, and the Southern Hemisphere is shivering in the long, cold nights of winter. In late December of every year, the North Pole points away from the sun, and the Tropic of Capricorn (latitude 23.5°S) receives the greatest solar input; then it is winter in the Northern Hemisphere and summer in the Southern Hemisphere. In late March and late September, the sun is directly above the equator, and both hemispheres experience equal lengths of day and night.”
[NOTE TO THE INSTRUCTOR: It can be useful to include an “I don’t know” or “I don’t understand this question” choice with clickers, because it can help you discover how many students really haven’t understood the concept at all. Use of this option may depend on whether you assign participation-only points or performance points (or some combination) to clicker questions in your course. If you only assign participation points, it may be useful to leave the “I don't know” choice in the question, as it gives students a penalty-free way of indicating that more time may be needed on this concept.] 13

14. Figure 42.4 The Tilt of Earth’s Axis of Rotation Causes the Seasons

15. Figure 42.4 The Tilt of Earth’s Axis of Rotation Causes the Seasons

16. Discuss the validity of the following statement:
Concept Climate and Topography Shape Earth’s Physical Environments
Discuss the validity of the following statement:
Winter and summer seasons occur because Earth is farther from the sun in winter and closer to it in summer. 16

17. c. I don’t understand this question.
Concept Climate and Topography Shape Earth’s Physical Environments
The direction of prevailing winds at Earth’s surface is determined solely by Hadley cell circulation in the atmosphere that results from latitudinal gradients in solar energy input.
a. True
b. False
c. I don’t understand this question.
Answer: b
INSTRUCTOR NOTES:
Refer students to Figure 42.6 of the textbook.
Follow-up discussion:
Ask students what other factors affect wind direction (e.g., the north-south direction of surface winds is caused by vertical Hadley cell circulation, but the east-west direction of surface winds is caused by the spherical shape of the Earth and its spin).
[NOTE TO THE INSTRUCTOR: It can be useful to include an “I don’t know” or “I don’t understand this question” choice with clickers, because it can help you discover how many students really haven’t understood the concept at all. Use of this option may depend on whether you assign participation-only points or performance points (or some combination) to clicker questions in your course. If you only assign participation points, it may be useful to leave the “I don't know” choice in the question, as it gives students a penalty-free way of indicating that more time may be needed on this concept.] 17

18. Discuss the validity of the following statement:
Concept Climate and Topography Shape Earth’s Physical Environments
Discuss the validity of the following statement:
The direction of prevailing winds at Earth’s surface is determined solely by Hadley cell circulation in the atmosphere. 18

19. Figure 42.5 Global Atmospheric Circulation

20. Figure 42.5 Global Atmospheric Circulation

21. Figure 42.6 Direction of Prevailing Surface Winds

22. Figure 42.6 Direction of Prevailing Surface Winds

23. Figure Ocean Currents

24. Figure 42.8 Walter Climate Diagrams Summarize Climate in an Ecologically Relevant Way

25. Apply the Concept, Ch. 42, p. 829

26. Why are tropical latitudes and mountaintops wet?
Concept Climate and Topography Shape Earth’s Physical Environments
Why are tropical latitudes and mountaintops wet?
a. As air rises, it cools.
b. Liquid water evaporates as it is warmed and water vapor condenses as it is cooled.
c. Both a and b are involved.
d. Neither a nor b is involved.
e. I don’t understand this question.
Answer: a
INSTRUCTOR NOTES:
Students should refer to Figure 42.5, which shows Hadley cells (explain tropical moisture), and Figure 42.9, which shows rain shadows.
The goal is to get students thinking about the physical principles that are involved both in latitudinal precipitation patterns and rain shadows. Latitudinal gradients in solar input cause water to evaporate in the tropics. The warm moist air is buoyant and rises, and as it rises it (expands and) cools. The water vapor in the air condenses and falls as precipitation. This occurs in both with wet tropics and wet mountaintop areas.
Specific phenomena involved:
Hadley cells: In the tropics, warm, moist air rises, expands and cools, dropping its moisture, as it flows pole-ward. The now cool, dry air that has moved north and south from the equator warms and retains its moisture as it descends. It reaches Earth’s surface at about 30°N and 30°S. Because the air warms as it descends and is compressed, the little water that remains stays in a gaseous state. Earth’s great deserts are located at these dry, subtropical latitudes.
Rain shadow: Prevailing winds pick up moisture over water bodies. As air masses rise and cool as they come into contact with elevated areas of land, and release moisture in the form of precipitation.
Learning tip: As a starting point, students can think of a hot air balloon: “Hot air rises.”
[NOTE TO THE INSTRUCTOR: It can be useful to include an “I don’t know” or “I don’t understand this question” choice with clickers, because it can help you discover how many students really haven’t understood the concept at all. Use of this option may depend on whether you assign participation-only points or performance points (or some combination) to clicker questions in your course. If you only assign participation points, it may be useful to leave the “I don't know” choice in the question, as it gives students a penalty-free way of indicating that more time may be needed on this concept.] 26

27. Figure A Rain Shadow

28. Figure A Rain Shadow

29. Concept 42.3 Physical Geography Provides the Template for Biogeography
Comparing these two Walter climate diagrams showing rainforest in two different locations, we can see that
a. the location depicted by diagram A is wetter in January than the location depicted in diagram B.
b. location A has more seasonal variation than location B.
c. location A is warmer than location B.
d. All of the above
e. None of the above
Answer: b
Answer choice a: Location A is drier in January than location B (about 39 mm of precipitation compared with 60 mm).
Answer choice c: Location B is warmer (year-round, except in mid summer at the temperate location A, where temperatures are similar in both locations) than location A.
Seasonality is indicated by the extent of variation in temperature and precipitation over the annual cycle. Location B has very little temperature variation, and only a small amount of variation in precipitation over the year. Location A is cooler and drier in winter, and generally warmer and wetter in summer, with a greater range of both temperature and precipitation values over the year.

30. Concept 42.3 Physical Geography Provides the Template for Biogeography
With a partner or discussion group, compare the two Walter climate diagrams below, which show rainforests in two different locations.
Discuss their similarities and differences: Which is (a) wetter in January, (b) more seasonal, and (c) warmer?
Discuss where on Earth you would expect to find these two different rainforest biomes. Do you think they would both be found in the Northern Hemisphere?
Answers:
The location depicted in diagram A is wetter in January than the location depicted in diagram B.
Location A has more seasonal variation than location B.
Location A is warmer than location B.
(Seasonality is indicated by the extent of variation in temperature and precipitation over the annual cycle. Location B has very little temperature variation, and only a small amount of variation in precipitation over the year. Location A is cooler and drier in winter, and generally warmer and wetter in summer, with a greater range of both temperature and precipitation values over the year.)
INSTRUCTOR NOTES:
Regarding the question: Do you think both occur in the Northern Hemisphere?
Direct students to look at which seasons are warmer versus colder. Since there is very little temperature variation over the entire year in B, this should be a clue that it is a tropical location (tropical rainforest).
Extension question: How would you predict the Walter climate diagram would look if the temperate rainforest (shown in A) were in the Southern Hemisphere?
Answer: Seasons would be reversed; warmer and wetter in November, December, January, and February. 30

31. Concept 42.3 Physical Geography Provides the Template for Biogeography
INSTRUCTOR NOTES:
Extension question: Ask students how they would plot these graphs as dots on Figure of the textbook.
Answer: They could calculate the annual average temperature and precipitation, and then plot these points, expecting they will fall within the tropical rain forest and temperate rain forest segments.
Temperate rainforest: Large amount of rainfall overall but more seasonal variation in both temperature and precipitation.
Tropical rainforest: Generally warm and wet year-round. 31

32. Figure 42.10 Temperature and Precipitation Gradients Determine Terrestrial Biomes

33. Figure 42.11 Global Terrestrial Biomes

34. Figure 42.12 Same Biome, Different Continents

35. Figure 42.12 Same Biome, Different Continents (Part 1)

36. Figure 42.12 Same Biome, Different Continents (Part 2)

37. Figure 42.12 Same Biome, Different Continents (Part 3)

38. Figure 42.12 Same Biome, Different Continents (Part 4)

39. Concept 42.4 Geological History Has Shaped the Distributions of Organisms
Referring to the figure below, discuss the likelihood of finding closely related organisms in the following pairs of regions:
Europe and Asia
North and South America
Africa and South America 39

40. Concept 42.4 Geological History Has Shaped the Distributions of Organisms
Referring to the figure above, the likelihood of finding closely related organisms is greatest in which of the following pair of regions?
a. Australia and New Zealand
b. North and South America
c. Africa and South America
d. The likelihood is the same for each pair.
e. I don’t understand this question.
Answer: b
(North and South America will likely be the most similar in terms of organisms.)
INSTRUCTOR NOTES:
Follow up question: What is the reason for this?
Answer: Discuss how it is related to how long the places have been isolated and undergone independent evolution. The time since separation for North and South America is the least for all of these pairs.
Time since separation is: Australia and New Zealand (80 MY), North and South America (6 MY), and Africa and South America (100 MY).
Similarities are likely linked to amount of time that has passed since the continents were joined. The longer the time period, the less similar taxa are likely to be, since there has been a longer period of time for evolution and extinction to occur.
North and South America have recently been reconnected via the narrow land bridge that is Central America.
[NOTE TO THE INSTRUCTOR: It can be useful to include an “I don’t know” or “I don’t understand this question” choice with clickers, because it can help you discover how many students really haven’t understood the concept at all. Use of this option may depend on whether you assign participation-only points or performance points (or some combination) to clicker questions in your course. If you only assign participation points, it may be useful to leave the “I don't know” choice in the question, as it gives students a penalty-free way of indicating that more time may be needed on this concept.] 40

41. Concept 42.3 Physical Geography Provides the Template for Biogeography
 Do the same set of factors determine characteristics of terrestrial and aquatic biomes?
a. Yes
b. No
Answer: b
Terrestrial biomes are mainly determined by temperature, precipitation, and soil type, and are characterized by distinct vegetation types.
Aquatic biomes are distinguished by water depth and movement, temperature, pressure, salinity, dissolved oxygen, depth of light penetration, and characteristics of the substrate (see page 833 of the textbook).
The littoral (intertidal) zone is occupied by plants and animals specifically able to deal with variability in water levels, exposure to air (desiccation), wave action, and changes in salinity (e.g., rainfall during low tide).
INSTRUCTOR NOTES:
Extension question: Would you expect to find the same organisms in the littoral zone of a lake versus the littoral zone of the ocean? 41

42. Table 42.1 Major Aquatic Biomes

43. Figure 42.13 Water-Depth Zones

44. Figure 42.13 Water-Depth Zones

45. Figure 42.13 Water-Depth Zones (Part 1)

46. Figure 42.13 Water-Depth Zones (Part 2)

47. Concept 42.4 Geological History Has Shaped the Distributions of Organisms
Alfred Russel Wallace proposed that a line (now known as Wallace’s line) separates two distinct faunal regions in Southeast Asia, between Bali and Lombok.
Discuss the reasons for the faunal differences between these two islands. 47

48. a. distance between the islands.
Concept Geological History Has Shaped the Distributions of Organisms
Alfred Russel Wallace proposed that a line (now known as Wallace’s line) separates two distinct faunal regions in Southeast Asia, between Bali and Lombok. We now know that distinctive “line” is a boundary because of
a. distance between the islands.
b. depth of the ocean trench between the islands.
c. climate differences.
d. soil differences.
e. All of the above
Answer: b
(Refer to page 834 of the textbook, under the subheading “Barriers to dispersal affect the distributions of species”.) 48

49. Figure Wallace’s Line

50. Figure Wallace’s Line

51. Figure 42.15 Movement of the Continents Shaped Earth’s Biogeographic Regions

52. Figure 42.15 Movement of the Continents Shaped Earth’s Biogeographic Regions

53. Figure 42.16 Distribution of Nothofagus

54. Figure 42.16 Distribution of Nothofagus

55. Figure 42.16 Distribution of Nothofagus (Part 1)

56. Figure 42.16 Distribution of Nothofagus (Part 2)

57. Apply the Concept, Ch. 42, p. 837

58. Figure 42.17 Human Agricultural Practices Produce a Uniform Landscape

59. Figure 42.18 Harmonious Grazers

60. a. The moving of organisms on purpose or by accident
Concept Human Activities Affect Ecological Systems on a Global Scale
Referring to Concept 42.5 of the textbook, which of the following human activities do you think are most strongly blurring biogeographic boundaries?
a. The moving of organisms on purpose or by accident
b. The clearing of land for agriculture
c. The fragmentation of habitats
d. I don’t understand this question.
Answer: a
INSTRUCTOR NOTES:
Human-assisted dispersal of organisms takes many forms. Some examples:
Stowaways such as the brown tree snake in Guam, which is believed to have been brought there there via air freight; mosquitoes and avian malaria (Hawaii) and zebra mussels (Great Lakes) in bilge water from ships.
Purposeful introductions: Cane toad in Australia, starlings and house sparrow in North America, grasses for lawns (around the world), animals introduced for food (e.g., pigs, goats, horses)
Aesthetic introductions: Exotic pets, ornamental garden species
Biological control, and recreation (e.g., sport fish, game birds introduced for hunting or fishing)
Extension: Excellent videos to present in class:
“Throughout the entire history of life on this planet, species have always changed their ranges, they’ve always spread into new regions, but what’s happening now is fundamentally different, in terms of both rate and spatial scale.”
Dr. Anthony Ricciardi, McGill University (from the video)
Nova News Minute:
[NOTE TO THE INSTRUCTOR: It can be useful to include an “I don’t know” or “I don’t understand this question” choice with clickers, because it can help you discover how many students really haven’t understood the concept at all. Use of this option may depend on whether you assign participation-only points or performance points (or some combination) to clicker questions in your course. If you only assign participation points, it may be useful to leave the “I don't know” choice in the question, as it gives students a penalty-free way of indicating that more time may be needed on this concept.] 60

61. a. Models are useful in addressing complex problems.
Concept Ecological Investigation Depends on Natural History Knowledge and Modeling
One way to investigate the impacts of atmospheric greenhouse gases on Earth’s climate would be to have several Earths where we burn fossil fuels to increase atmospheric carbon dioxide, and several more Earths as controls where the atmospheric CO2 composition is held constant. Why might modeling be a better way to assess the potential impacts of greenhouse gases on Earth’s climate?
a. Models are useful in addressing complex problems.
b. We only have one Earth, and no replicates or controls are available.
c. Modeling allows us to predict effects of CO2 on climate without having to wait for experimental results.
d. An experiment that affected the whole planet might be difficult to get approved, very expensive, and might have undesirable or irreversible impacts.
e. All of the above
Answer: e
INSTRUCTOR NOTES:
Make sure that students know that it is assumed that variability from natural sources of carbon dioxide, such as volcanic eruptions, would be consistent across all Earths.
Suggested editorial changes may make the long first sentence easier to parse. It is assumed that variability from natural sources of GHG is consistent across all Earths.
Be sure to tell students that climate models will be treated in Chapter 46, to avoid them wondering where they missed this material in Chapter 42.
Note: This is not an exhaustive list, and students might come up with other valid reasons as to why modeling is a better approach than this hypothetical (and obviously impossible!) experiment.
Climate change has indeed been referred to by some scientists as “an uncontrolled scientific experiment” on all of the inhabitants of our planet. Modeling of climate has become increasingly sophisticated over the past several decades, and many of the patterns currently seen: increased frequency of severe weather events, exaggerated warming at the poles, melting of polar ice caps, changes in rainfall and temperature, etc. are consistent with the predictions of climate models.
RESOURCES:
See
Chapter 46 of the textbook. 61

62. Model Predictions Real World Data
Concept Ecological Investigation Depends on Natural History Knowledge and Modeling
Model Predictions
Real World Data
INSTRUCTOR NOTES:
Optional slide for instructor reference.
Refer to Chapter 46 of the textbbok, which discusses climate models.
Models can be checked against real climate change data, and then adjusted (to improve the models), and then again checked against real data (as variables and dynamics of the model are better understood over time, the models can be modified and improved).
ART SOURCES:
Model Predictions: Courtesy of United States Environmental Protection Agency
Real World Data: Courtesy of the Intergovernmental Panel on Climate Change 62