Solution Manual for Ecology Concepts and Applications Release 2025 Anna A. Sher and Manuel C. Molles 1. Answers to End-of-Chapter Review Questions 2. Answers to Critiquing the Evidence 3. Answers to Concept Review Questions
Answers to End-of-Chapter Review Questions Chapter 1 1. The advantage of dividing the field of ecology into subdisciplines, each focusing on a single level of organization is that such concentration and simplification tends to make the hypotheses addressed more likely to be testable. 2. The pitfalls of subdividing nature is that important ecological relationships may go unrecognized. Figure 1.1 misrepresents nature by converting the complexity of nature into an abstract simplification and by picturing the natural world as a vertically nested hierarchy, when in fact natural relationships and influences are more like a tangled web. 3. In the case of MacArthur’s warblers, you might compare the use of foraging zones by warbler species in areas with the full complement of warbler species with the use of foraging zones where one or more species is missing from the community. One way to test the role of competition in excluding some American redstarts from productive feeding areas would be to capture and remove the, presumably, dominant individuals from those areas to see if other redstarts, especially females and young males would move in to replace the individuals removed. 4. New technology allows us to see things we were not able to observe before, and ask questions that we were not previously able to address. For example, drones can carry cameras and other sensors to locations that are not easily accessible. Stable isotope analyses allow us to trace water and nutrients through ecosystems. Genetic analyses allow us to identify gut contents. Sound equipment allows us to hear things out of the range of human hearing. Citizen science initiatives increase the number of eyes and ears collecting evidence. Improved computing allows us to analyze larger data sets and run complex models to more accurately predict future events. 5. The species composition of these forests has changed substantially and their composition is likely to change in the future in response to climatic change. 6. There are trade-offs when comparing simple and complex models. While complex models include more data/variables and potentially provide greater accuracy, they may also incorporate more assumptions and therefore have a greater potential for error if any of those assumptions are invalid. Chapter 2 Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
1. Use biome discussions as a guide. 2. Use figure 2.8 and the associated discussion as a guide. 3. Use figure 2.4 and associated discussion as a guide. High precipitation in the tropics is produced by high rates of evaporation and subsequent condensation of water vapor in ascending air masses. The clouds formed in this way produce the heavy precipitation associated with the tropics. High precipitation at temperate latitudes is produced when warm moisture bearing subtropical air meets cold polar air, which forces condensation of the water vapor in the subtropical air mass. Many tropical environments experience drought during periods of El Niño (see chapter 23). 4. The seasonal rainfall of these biomes is produced by shifts in the latitude at which the sun is directly overhead. Figure 2.4a, which shows the sun directly overhead at the equator, which generates storms through the processes of evaporation, condensation and precipitation of water, is really a snapshot of a dynamic system. The latitude at which the sun is directly overhead, which is sometimes called the "solar equator", and acting as a generator of tropical storms shifts between 23.5° N and 23.5° S. The wet season comes during the warmer time of the year when the sun is more nearly overhead. The dry season comes when the solar input is less direct (sun's angle is more oblique). 5. Anywhere that the presence of mountains which can force precipitation in rising air masses and form a "rain shadow" in the leeward (downwind) side. The height of mountains will generally make a difference in the rain shadow effect, since higher mountains will induce more precipitation in rising air masses. 6. One of the greatest differences is the presence of permanent snow and ice on mountains at high latitudes. 7. One of the main differences between midlatitude and tropical alpine zones is that on tropical mountains daily variation in temperature is nearly as great as seasonal variation. Tropical alpine ecosystems lack fht every strong seasonality in input of solar radiation and temperature that occurs in midlatitude alpine zones. 8. In tropical climates the dominant seasonal change is from wet season to dry season. At very high latitudes it is cold much of the year with a brief cool growing season. In some tropical countries, such as Costa Rica, people have divided the seasonal changes significantly than has been done customarily in temperate climates. In the middle of the wet season, for instance, there is a period of reduced rainfall which Costa Ricans call veranillo, which means "little summer". The point here is that the seasonal terms associated with midlatitudes do not fit the annual variations that occur in other parts of the earth. It would be interesting to catalog the traditional terms for seasonal changes used by native peoples living in different climatic zones. 9. There has been much greater connection and exchange across the tundra and boreal forests which form nearly continuous bands in the northern hemisphere. In contrast, the temperate woodland tropical rain forest biomes are highly fragmented with few opportunities for biotic exchange over long periods of evolutionary history. 10. The most heavily impacted biomes have been temperate forest, temperate grassland, desert, and temperate woodland. Areas of tropical dry forest have also been fairly heavily impacted. Tropical rain forest, boreal forest, and tundra have received less impact. Satellite imagery could be used to assess the density of human-induced change on landscapes. The very high rates of human population growth in tropical countries and increasing resource extraction in the northern biomes will likely increase human impact in these biomes.
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Chapter 3 1. Use Figure 3.2 as a guide for your review. The major sources of freshwater are groundwater, lakes, and rivers. A large amount of freshwater is also present as ice. Water shortages already affect large regions of the world and groundwater levels are dropping in many regions. Even where water remains plentiful, pollution is reducing water quality. 2. The proportion of the ecosystem receiving sufficient light to support photosynthesis is 200 m divided by 4000 m, about 0.05 or 5% of the total. 3. Major challenges faced by organisms moving from an aquatic to a terrestrial environment included lower support in the less dense aerial medium, greater temperature variation on land, and desiccating water loss to air. Some advantages were less resistance to movement through air, lower rate of heat loss to air, and higher oxygen concentrations. 4. Refer to figure 3.13 as you develop your answer. Darwin's developmental sequence was tested by drilling on atolls, which revealed deep accumulations of ancient coral reefs deposited on sunken volcanic mountains. 5. The main factor here is that, though urchins feed on young corals, they also suppress the growth of algae, which reduces algal competition with the young corals. Thus the net effect of urchins on coral establishment is positive. 6. The wide environmental fluctuations of the intertidal environment has probably selected for greater physiological tolerance among intertidal species. Because of differences in the intensity of selection, tolerance of variation in salinity should be higher in the upper intertidal zone compared to the lower intertidal and subtidal zones. 7. Because small grain size reduces rates of water flow, oxygen concentration is generally lower in the interstitial waters of fine sediments compared to coarse sediments. Oxygen concentrations should be lower in tide pools in sheltered locations because of wave-related circulation. 8. The most direct way to test these predictions would be to study the relative contributions of litterfall from streamside forests and photosynthesis within the stream to the total energy budget of the stream. 9. Two approaches have been used to study the influence of nutrient availability on lake primary production. The first has involved measuring nutrient availability and rates of primary production in a large number of lakes and looking for a correlation between these two variables. The second approach has been to increase the nutrient availability in lakes and measure primary production responses (see Chapter 18). 10. It is clear that that the introduction of exotic species has greatly altered the structure and functioning of the Great Lakes ecosystem. However, the Great Lakes of Africa have also been impacted by species’ introductions. See Chapter 17 online, which includes a discussion of the effects of introducing Nile perch on the rich fish fauna of Lake Victoria. Chapter 4 1. Darwin mainly conducted comparative studies of natural populations, while Mendel conducted numerous experimental studies in his garden. In addition, Mendel used mathematics extensively in his work, while Darwin did not. Darwin proposed potential mechanisms for evolutionary change in species. Mendel discovered mechanisms of inheritance. The studies of Darwin and Mendel prepared the way for the later studies
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