This Document Contains Chapters 3 to 4 Chapter 3 Biodiversity and Evolution Summary and Objectives 3-1 What is biodiversity and why is it important? Biodiversity involves several levels including genetic, species, ecological, and functional diversity. It is a vital renewable resource that keeps us alive as long as we live off of the biological natural income it provides. CONCEPT 3-1 The biodiversity found in genes, species, ecosystems, and ecosystem processes is vital to sustaining life on the earth. 1. What is biodiversity, and why is it vital to sustaining life on Earth? 2. Summarize the four main facets of biodiversity. 3-2 Where do species come from? The process of biological evolution by natural selection occurs when genetic changes result in differential reproduction, selecting those individuals with the adaptive trait. This results in populations that are better able to survive and reproduce under existing environmental conditions. CONCEPT 3-2 According to the scientific theory of evolution through natural selection, populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits. 3. Briefly describe the theory of evolution, being sure to include the roles played by variation within the gene pool and natural selection. What are the limitations to natural selection? Summarize and address three common misconceptions about evolution through natural selection. 4. What are fossils, and what information can they provide in terms of how life developed on Earth? 5. How can geologic processes, catastrophes, and climate change affect natural selection? 3-3 How do speciation, extinction, and human activities affect biodiversity? Natural selection can lead to development of an entirely new species; in speciation, two species arise from one usually as a result of geographic isolation and reproductive isolation. Extinction is normally a low-rate process that occurs when organisms cannot adapt to some change in their environment. CONCEPT 3-3 As environmental conditions change, the balance between formation of new species and extinction of existing species determines the earth’s biodiversity. 6. Define speciation. Explain how geographic isolation and reproductive isolation can result in speciation. 7. Distinguish between background extinction and mass extinction. 8. Explain why we should be concerned about extinction of species. 3-4 What are biomes and how have human activities affected them? Terrestrial parts of the earth are called biomes. Biomes are influenced by climate, latitude, and altitude. CONCEPT 3-4A Differences in average annual precipitation and temperature lead to the formation of tropical, temperate, and cold deserts, grasslands, and forests, and largely determine their locations. CONCEPT 3-4B In many areas, human activities are impairing ecosystem and economic services provided by the earth’s deserts, grasslands, forests, and mountains. 9. Describe how climate affects the distribution of plant life on Earth. Compare the climate in deserts, grasslands, forest, and mountains. Summarize the interactions of altitude, latitude, and biome type. 10. Explain how human activities are negatively impacting terrestrial biomes. 3-5 What are aquatic life zones and how have human activities affected them? Freshwater life zones and ocean/marine life zones are the two types of aquatic life zones on the earth. Different types of organisms, plant and animal, evolve in these aquatic zones, according to environmental conditions. CONCEPT 3-5A The key factors determining biodiversity in aquatic systems are temperature, dissolved oxygen content, availability of food, and availability of light and nutrients necessary for photosynthesis. CONCEPT 3-5B Human activities threaten aquatic biodiversity and disrupt ecosystem and economic services provided by saltwater and freshwater systems. 11. Evaluate the significance of the ecological contributions of the oceans. Distinguish between coastal zones and open sea. List and compare the three principal zones of an ocean. 12. Distinguish between coastal and inland wetlands. Describe the ecological functions performed by wetlands. Describe environmental problems associated with coastal and inland wetlands. 13. List and compare the four zones of a lake. Distinguish between oligotrophic and eutrophic lakes. Describe stratification and a turnover in a lake. 14. Name three different human activities that are currently threatening aquatic life zones. d Evolution Key Terms biological diversity or biodiversity biological evolution or evolution natural selection fossils mutations adaptation adaptive trait differential reproduction climate speciation geographic isolation reproductive isolation extinction endemic species artificial selection genetic engineering background extinction rate mass extinction biomes desert grasslands forest mountains aquatic life zones coastal zone estuary coastal wetland open sea lakes oligotrophic eutrophic hypereutrophic mesotrophic surface water runoff streams watershed drainage basin inland wetlands Outline 3-1 Biodiversity Is a Crucial Part of the Earth’s Natural Capital. A. The major components of biodiversity are genetic diversity, species diversity, ecological diversity, and functional diversity. B. Biodiversity is vital to sustaining life on the earth – preserving air and water quality, maintaining topsoil fertility, decomposing and recycling wastes, and controlling pest populations. Human activity is destroying the earth's biodiversity at an increasing rate. 3-2 Where Do Species Come From? A. Evolution is the change in a population’s genetic makeup over time; populations evolve by becoming genetically different. B. Natural selection occurs when members of a population have genetic traits that improve their ability to survive and reproduce offspring with those specific traits. C. Over time, a population’s gene pool changes when mutations (beneficial changes) in DNA molecules are passed on to offspring. 1. Mutations occur in two ways. a. Random changes that occur in coded genetic instructions. b. Exposure of DNA to external agents like X rays, chemicals, or radioactivity (collectively called mutagens) 2. Only mutations in reproductive cells are passed to offspring. D. For natural selection to occur in a population, three conditions are necessary: 1. The population must have genetic variability. 2. The trait must be heritable, capable of being passed from one generation to another. 3. The trait must enable individuals with the trait to produce more offspring than individuals without the trait; this is differential reproduction. E. Adaptation or adaptive traits are heritable traits that help organisms to survive and reproduce better under prevailing environmental conditions. 1. Structural adaptations include coloration, mimicry, and protective cover, e.g., gray wolves. 2. Genetic resistance adaptations allow an organism to tolerate a chemical designed to kill it. F. Limits to adaptation through natural selection 1. A beneficial heritable trait must already be present in a population’s gene pool. 2. The population’s ability to adapt depends on its reproductive capacity. G. Uncovering myths about evolution through natural selection 1. “Survival of the fittest” does not mean “survival of the strongest.” Evolution is concerned with leaving the most descendants, NOT the strongest ones. 2. Organisms do not always develop certain traits because they need or want them. 3. Evolution through natural selection does not mean that a species will become more perfectly adapted. There is no master plan to achieve genetic perfection. H. Environmental conditions can also affect biological evolution through natural selection (See Science Focus: Earth Is Just Right for Life to Thrive) 3-3 How Do Speciation, Extinction, and Human Activities Affect Biodiversity? A. Natural selection can lead to development of an entirely new species. 1. In speciation, two species arise from one when some members of a population cannot breed with other members to produce fertile offspring. (See Science Focus: Changing the Genetic Traits of Populations) a. Speciation takes place in geographic isolation. b. Speciation takes place in reproductive isolation. The gene pools are so changed that members become so different in genetic makeup that they cannot interbreed. B. When population members cannot adapt to changing environmental conditions, the species becomes extinct. Endemic species are found in only one area and are more vulnerable to extinction 1. When local environmental conditions change, some species will disappear at a low rate; this is called background extinction. 2 Mass extinction is a significant rise in extinction rates above the background extinction level. Usually, from 25–70% of species are lost. There appear to have been two mass extinctions on Earth. 3. After mass extinction new species evolve to fill niches in changed environments. It takes one to ten million years to rebuild biological diversity after a mass extinction/depletion. 3-4 What Are Biomes and How Have Human Activities Affected Them? A. Terrestrial parts of the earth are called biomes: regions that have a distinct climate and particular form of life, especially plant life. B. The planet’s climate produces these different types of biomes. 1. Average temperature and average precipitation determine a region’s climate. 2. Biomes themselves are a mosaic of different biological communities, all similar to a particular biome: forest, grassland, and desert. C. Precipitation generally determines the type of biome: desert with little water and low vegetation; grassland with enough precipitation for grasses; and forest with enough water to support trees and smaller types of vegetation. D. Climate and vegetation vary with amount of precipitation and with latitude and altitude. E. Deserts take a particularly long time to recover from disturbances to them. 1. Their plant growth is slow. 2. There is limited/low species diversity. 3. Their nutrient cycle to sustain plants is slow moving. F. Grasslands are located in the interiors of continents and are able to endure a variety of environmental conditions. G. Forests are dominated by trees and consist of three main forest classes: tropical, temperate, and cold. H. Mountains are high lands that help to regulate the earth’s climate and play an important role in the hydrologic cycle. I. About 62% of the world's major land ecosystems are being used unsustainably. 3-5 What Are Aquatic Life Zones and How Have Human Activities Affected Them? A. The two types of aquatic life zones are: freshwater life zones and ocean/marine (saltwater) life zones. 1. Key factors in determining types and numbers of organisms found in aquatic zones are: water temperature, dissolved oxygen content, availability of food, availability of light and nutrients required for photosynthesis. B. Marine zones that are rich in biodiversity are divided into three major life zones. 1. The coastal zone interacts with the land and, thus, is much affected by human activities. Ecosystems in coastal zones have a high net primary productivity per unit of area. a. Estuaries are partially enclosed areas of coastal water where seawater and fresh water mix, as do nutrients from water in rivers, streams, and runoff. b. Coastal wetlands, like mangrove forest swamps and salt marshes, are covered with water all or part of the year. c. Coral reefs in the shallow coastal zones of tropical and subtropical oceans support the world’s most diverse and productive ecosystems. 2. The second marine life zone is the open sea. The three vertical zones of the open sea are the euphotic, bathyal, and abyssal. These zones are described on the basis of sunlight penetration into them. 3. Human activities are disrupting and degrading the services provided by aquatic systems, especially coastal wetlands, shorelines, mangrove forests, and coral reefs. C. Major freshwater life zones are lakes, wetlands, and rivers. 1. The freshwater ecosystems cover less than 1% of the earth’s surface; the water in these systems can be standing or flowing. 2. Lakes are described in reference to their plant nutrients. a. An oligotrophic lake is one that has been newly formed and has a small supply of plant nutrients. They are often deep and crystal-clear blue or green water. b. A eutrophic lake has a large or excessive supply of nutrients. They need to be shallow, have a high net primary productivity, and water with poor visibility. c. A hypereutrophic lake has excessive nutrients due to human activities. d. Lakes between oligotrophic and eutrophic are called mesotrophic lakes. 3. Precipitation that does not sink into the ground or evaporate is called surface water. When it flows into streams, it is called runoff. A watershed/drainage basin is land area that delivers runoff, sediment, and substances to a stream. 4. When water flows downhill, it is identified by three zones: the source zone is water from mountain streams; the transition zone contains wider, lower-elevation streams; and the floodplain zone contains rivers that open into the ocean. a. River systems are a series of different ecosystems. b. Streams flow downhill and shape the land in many ways. 5. Man has compromised the watershed around rivers and streams and has, thereby, increased the flow of plant nutrients, sediment, and pollutants into the ecosystems. 6. Inland wetlands are away from coastal areas and cover land with fresh water all or part of the time. Seasonal wetlands cover the land for a short time each year; they are called prairie potholes, floodplain wetlands, and bottomland hardwood swamps. These wetlands provide ecological services: a. Filtering toxic wastes and pollutants. b. Absorbing and storing excess water from storms. c. Providing habitats. Teaching Tips 1. Misconceptions about science are very common and act as a barrier to learning new information. Evolution in particular has many misconceptions. Exposing, examining, and resolving misconceptions before beginning a lesson is helpful in preparing students to learn or relearn the new information within the proper framework. Revisiting these misconceptions later is also recommended because many misconceptions are deeply held and difficult for a learner to reconstruct. 2. Helping the student create connections between their existing knowledge and the new knowledge is a vital step in the learning process. Drawing on that which the student already knows promotes confidence in the student and prepares them for the information to come. Remember, making the new information relevant to the student is crucial. 3. In addition to being an excellent critical thinking activity, the following can help prepare students for learning about how biodiversity in ecosystems functions and why it is important. As the lesson proceeds, similarities can be made between the warm-up activity and the content being learned. Consider using the following as a warm-up activity for Chapter Three. In small groups, evaluate the diversity of your community using criteria such as ethnic, racial, religious, and socioeconomic groups; lifestyles; and industries, landscape features, and landscape forms. What elements of diversity have proved troublesome? What additional elements of diversity would improve your community? 4. Depending on the class size, you may want to have students share what they have learned with one another in small groups or as a class. Topics for Term Papers and Discussion Conceptual Topics 1. Evolution: the theory of evolution, supporting and detracting evidence, fossils; embryological homologies, structural homologies; biochemical evidence; DNA evidence. Contrast the views of slow, gradual change and relatively rapid (punctuated) change. What is known about how animals adapt to changing environmental conditions? 2. Plant and animal adaptations to different biomes. Desert plants and animals; plants and animals of the tundra; mountain microclimates and vertically zoned vegetation; organisms of the Amazon. 3. Human activities interfering with ecosystems. Inorganic fertilizers; phosphate detergents and cultural eutrophication; sulfur compounds and acid deposition; CFCs and ozone depletion; combustion of fossil fuels and greenhouse gases; degradation and deforestation of tropical forests; wetlands development; intensively developed coastal areas, bleaching of coral reefs. 4. Fragile ecosystems. Deserts; tropical forests; tundra. 5. Aquatic life zones: coastal zones, beaches, coastal wetlands, coral reefs, the abyssal zone. 6. Freshwater life zones: lakes, streams, and rivers. Attitudes & Values 1. Are you familiar with any specific fluctuations in populations of species (extinction or population growth)? What were your explanations for the fluctuations? Did you have any particular feelings about the fluctuations? Do you feel you have a right to manipulate the populations of other species? If so, under what circumstances? Do you think species have a right to struggle to survive without human interference? 2. Have you visited a variety of types of ecosystems? If so, where do you feel most at home? Do you feel you are part of an ecosystem? What niche do you fill? 3. Do you feel that the development of your community is related to the climate of the area? Are there any connections you have experienced? Are you aware of mountains or bodies of water in your area that affect local climate conditions and human developments? Is your water supply affected by spring and fall turnovers? 4. Do humans have a right to use the atmosphere in any way they wish? Do you see limits to freedom of choice? If so, what determines those limits? Do you feel that humans have the power to alter Earth's climate? Do you feel that humans can responsibly control their impact on the atmosphere? 5. Do humans have a right to use aquatic life zones in any way they wish? Do you see limits to freedom of choice? If so, what determines those limits? Do you feel that humans have the power to alter the quality of aquatic life zones? Do you feel that humans can responsibly control their impact on these zones? 6. Should our goal for human population be to reach Earth’s carrying capacity? 7. To what extent should humans take evolution into their own hands? Should there be limits on genetic engineering? How does the change that humans create through cultural evolution compare to the process of evolution by natural selection? 8. Should we retreat from the beach? Should houses built on barrier islands/beaches have access to insurance? 9. What is life like at hydrothermal vents in the deep ocean? Action-Oriented Topics 1. Scientific methods: genetic engineering; DNA analysis; carrying capacity analysis. 2. Global: the Montreal Protocol; Kyoto Protocol. 3. Regional. Restoration of degraded ecosystems, ecosystem management, restoration versus rehabilitation. 4. National energy policy. Evaluation of the current national energy policy proposals in light of the laws of energy and long-term economic, environmental, and national-security interests. Activities and Projects 1. As a class, consider the crops that provide the majority of our food. Brainstorm a list of “designer genes” that would improve those crops for human consumption. Reflect on how genetic engineering alters the relationship between humans and evolution. Consider the power and the limits of that relationship. See the Science Focus on page 56. 2. Are inland wetlands being drained and filled in your area? Is there a nearby stream or river being subjected to excessive levels of pollution? Is it feasible for you and your class to “adopt” one of these disturbed ecosystems and help restore it to health? 3. Arrange a debate on the problems and alternatives of coastal zone management. Debate the proposition that we should severely restrict engineering approaches to beach stabilization and adopt a “retreat from the beach” strategy, emphasizing the preservation of coastal ecosystems and the ecosystem services they provide. 4. Organize a class field trip to systematically investigate the ecological niches for plant and animal life existing in a landscape significantly modified by human activities. If possible, arrange to travel along a gradient that will take you from farmland to suburbs to city to central business district. (A simplified version of this exercise could be done by walking around campus.) 5. In small groups, evaluate the diversity of your community using criteria such as ethnic, racial, religious, and socioeconomic groups; lifestyles; and industries, landscape features, and landscape forms. What elements of diversity have proved troublesome? What additional elements of diversity would improve your community? 6. Invite an evolutionary biologist to your class. Ask about evidence for different parts of the theory of evolution, including the endosymbiont hypothesis. Ask about the Gaia hypothesis. 7. Invite a climatologist to visit your classroom to describe the climate of your region: past, present, and future. 8. Arrange a field trip providing opportunities to compare and contrast ecosystems of several different types, including some damaged or stressed by human activities. Invite an ecologist or biologist along to identify and discuss specific examples of species adaptation to environmental conditions. Do the boundaries between different kinds of ecosystems tend to be sharply delineated? Can you identify factors that limit the growth of certain species? 9. Arrange a field trip providing opportunities to compare and contrast aquatic life zones. What factors appear to be significant in determining the life found in each zone? 10. Ask students to bring to class and share examples of art, music, poetry, and other creative expressions of human thoughts and feelings about Earth's aquatic life zones. Lead a class discussion on the subject of the human tendency to settle near water. BBC News Videos The Brooks/Cole Environmental Science Video Library with Workbook, Featuring BBC Motion Gallery Video Clips, 2011. DVD ISBN: 978-0-538-73355-7 (Prepared by David Perault) Kalahari Desert Could Double in Size New Ideas for Dealing with Climate Change Darwin's Galapagos Under Threat Carbon Dioxide's Impact on Our Oceans Are We Facing an Extinction Crisis? Suggested Answers for Critical Thinking Questions 1. Biodiversity is important for our food supplies, building materials, energy, and medicines. If any of the four components of biodiversity is eliminated, the effects on the biosphere would include poorer quality air and water, less fertile soils, increased pest populations, and buildup of wastes. 2. (a) Natural selection aids in biodiversity as individuals pass on genetic traits to their offspring and populations evolve. Population control is aided as some populations are better able to adapt to the prevailing environmental conditions because of the inherited genetic traits. The organisms all depend on solar energy and nutrient cycling to survive. (b) Speciation occurs when two species arise from one, thereby increasing biodiversity. Population is controlled by the interaction of the diverse species. All species depend on solar energy and nutrient cycling to survive. (c) Extinction aids in the implementation of population control as well as biodiversity. An example of this lays in the fact that a mass extinction allows for the evolution of new species, which can fill unoccupied ecological roles or newly created ones. It also aids in nutrient cycling, as dead organisms are broken down and recycled back into the environment. 3. Answers may vary but may include: (a) Increasing use of antibiotics by people is cause for concern due to the evolution of antibiotic resistance in disease-causing bacteria. Eventually, the bacteria may be resistant to all antibiotics and humans will be unable to protect themselves against disease. (b) Increasing use of antibiotics in beef cattle and other livestock used for meat production is also a concern. With the evolution of antibiotic resistance, treatment of cattle and other livestock will not be effective and products sold from these animals may be harmful to consume. (c) Antibacterial soaps and detergents used by consumers may become less effective in killing bacteria with the evolution of antibiotic resistance in disease-causing bacteria. Instances of communicable diseases will most likely increase, despite regular hand washing. Healthcare workers and children will be especially at risk. 4. Student answers will vary but may include: Two simple examples of human activities that can separate and isolate populations of species and affect their evolution are: clearing large areas of land for monoculture and creating fragmented habitats by developing of roads, housing developments, and other infrastructure through wild areas. 5. Student answers will vary but may include clarifying the difference in the natural process of extinction (background extinction) and extinction as a result of our activities (development, climate change, pollution). The loss of a single species is a concern when you examine the entire ecosystem where that species lived. Each species has a specific role in an ecosystem, and the natural balance in the ecosystem can be disrupted when a species becomes extinct. Many of our activities that disrupt ecosystems are not out of necessity; they are for convenience at best or luxury at worst. The loss of biodiversity in any area impacts its ability to adapt to other environmental changes and the ecosystem services it provides. Those can ultimately impact the availability of fresh water, clean air, and nutrients that are critical for our survival, too. 6. Temperate grasslands are best for a) raising crops and b) grazing livestock. Using the three principles of sustainability, our methods for these processes could be improved (student answers will vary for this part). The variety of plants native to grasslands help produce thick, nutrient-rich soils. As we practice more and more monoculture, this natural chemical cycle of nutrients returning to the soil is lost, leading in turn to reliance on more fertilizers. Excessive grazing by livestock eventually kills off even the heartiest of plants, leading to loss of the plant biodiversity, allowing weeds to proliferate and increasing soil erosion. More sustainable approaches include: crop rotation, reducing monoculture, limiting fertilizer use, eliminating overgrazing, eliminating non-native plants and restoring grazing lands to a more native state. Using solar and renewable energy to power our farms would further minimize the ecological footprint of raising crops and grazing livestock. 7. Student answers will vary but should include a discussion of the negative impacts associated with the destruction of a freshwater wetland habitat such as a decrease of biodiversity, increased flooding and erosion by storm water, lack of recharge groundwater for aquifers, and the inability to replenish stream flows during dry periods. A more positive approach is examining the benefits of the wetland to the local ecosystem and the individual. Encourage an analysis of pros/cons from the individual's viewpoint, but also that of the wetland ecosystem. Chapter 4 Community Ecology, Population Ecology, and the Human Population Summary and Objectives 4-1 What roles do species play in an ecosystem? All different types of species in a community—native, non-native, indicator, exotic, and alien—play specific roles in its ecology. CONCEPT 4-1A Each species plays a specific ecological role called its niche. CONCEPT 4-1B Any given species may play one or more of four key roles—native, nonnative, indicator, or keystone roles—in a particular ecosystem. 1. Define ecological niche. Distinguish between a specialist and a generalist. Evaluate the conditions that favor these two approaches. 2. Explain the difference between a niche and a habitat. 3. Distinguish among the following roles played by species and give one example of each: native species, nonnative species, indicator species, and keystone species. Explain why these labels are important. 4-2 How do species interact? CONCEPT 4-2 Five types of species interactions—competition, predation, parasitism, mutualism, and commensalism — affect the resource use and population sizes of the species in an ecosystem. Over a long time scale, populations of some species develop adaptations to help them use shared resources at different times, in different ways, or in different places – a process called resource partitioning. 4. Why and how does resource partitioning occur? 5. Distinguish between a predator and a prey, and give an example of a predator-prey relationship. How does this relationship contribute to population management? 6. Distinguish among three forms of symbiotic relationships and give one example of each: parasitism, mutualism, and commensalism. 4-3 How do communities and ecosystems respond to changing environmental conditions? CONCEPT 4-3 The structure and species composition of communities and ecosystems change in response to changing environmental conditions through a process called ecological succession. Scientists currently believe that ecological succession is an ongoing struggle for resources, and that even late-successional communities are in a continual state of flux. 7. Define ecological succession. Distinguish between primary and secondary succession, giving an example of each. 4-4 What limits the growth of populations? Biotic potential together with environmental resistance determine the carrying capacity of a habitat – the maximum population of a given species that the habitat can sustain indefinitely. CONCEPT 4-4 No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources. Population crash (dieback) can occur if a population exceeds the carrying capacity of its environment. 8. Explain the concepts of biotic potential, intrinsic rate or increase, environmental resistance, and carrying capacity. Using these concepts, explain why there are always limits to population growth in nature. 9. Differentiate between exponential growth and logistic growth of populations. 10. Briefly explain why humans are not exempt from nature’s population controls. 11. Distinguish between opportunists and competitor species. How are their reproductive rates different? 4-5 What factors influence the size of the human population? Expansion of habitat, emergence of modern agriculture, and development of sanitation, antibiotics, and vaccines have all contributed to the expansion of the human population in the last 200 years. CONCEPT 4-5A Population size increases because of births and immigration, and decreases through deaths and emigration. CONCEPT 4-5B The average number of children born to women in a population (total fertility rate) is the key factor that determines population size. An array of social, economic, and health factors contributes to the TFR of a given country. CONCEPT 4-5C The numbers of males and females in young, middle, and older age groups determine how fast a populations grows or declines. 12. Define birth rate, death rate. Write an equation to mathematically describe the relationship between these rates and the rate of population change. 13. Distinguish between replacement-level fertility and total fertility rate. Describe how these fertility rates affect population growth. 14. What factors affect birth rates and fertility rates? 15. Why is infant mortality rate a key measure of a society's quality of life? 16. How does age structure impact a society? What is the impact of a rapid population decline, especially when that is focused in a single age group? 4-6 How can we slow human population growth? As the world's population grows, debates about interactions among population growth, economic growth, politics, and moral beliefs are some of the most important environmental questions being addressed today. As countries develop, they undergo demographic transition, resulting in slowed population growth. CONCEPT 4-6 We can slow human population growth by reducing poverty, elevating the status of women, and encouraging family planning. 17. List the four stages of the demographic transition. List social, biological, political, and economic issues that can be addressed to help developing countries undergo a demographic transition. 18. What is the connection between a woman's birth rate and her access to education and social/economic opportunities? 19. What is family planning? Describe the roles of family planning. 20. Compare and evaluate the population policies of China and India. 21. What are the key approaches (as identified by the United Nations Conference on Population and Development) to slowing population growth? Key Terms ecological niche (niche) habitat generalist species specialist species native species nonnative species indicator species keystone species interspecific competition resource partitioning predation predator prey predator–prey relationship parasitism mutualism commensalism ecological succession primary ecological succession secondary ecological succession biotic potential intrinsic rate of increase (r) limiting factors environmental resistance carrying capacity population crash population change crude birth rate crude death rate fertility rate replacement-level fertility rate total fertility rate (TFR) life expectancy infant mortality rate migration age structure demographic transition family planning Outline 4-1 What Roles Do Species Play in an Ecosystem? A. An ecological niche is a species’ way of life in an ecosystem, including everything that affects its survival and reproduction. 1. The niche includes the members’ adaptations, its range of tolerance for physical and chemical conditions, its interactions with other components of the ecosystem, and its role in energy flow and matter recycling. 2. This is NOT the same has an organism’s habitat. A habitat is the place where an organism lives. 3. Generalist species have broad niches: they can tolerate a wide range of environmental conditions. 4. Specialist species have narrow niches: they have narrow tolerances for food or environmental conditions. They are prone to extinction when environmental conditions change. 5. See Case Study on Giant Pandas for specific information on this specialist species. B. Native species are those that normally live in a particular ecosystem. 1. Nonnative species (also called invasive, alien, exotic species) are those that have been introduced to an ecosystem. They are not always threatening, but often nonnative species can out-compete native species, with unexpected consequences. C. Indicator species alert us to harmful changes to a community or ecosystem. 1. See Case Study: Why Are Amphibians Vanishing? D. Keystone species help ecological communities run smoothly 1. Keystone species influence the type and number of other species in the ecosystem. 2. Keystone species fill vital ecological roles: e.g., pollinating and regulating populations of other species. See Case Study: Why Should We Protect Sharks 3. Loss of a keystone species can lead to population crashes and extinctions of other species that depend on them for ecological services. 4-2 How Do Species Interact? Five basic species interactions are competition, predation, parasitism, mutualism, and commensalism. A. Competition between species for food, sunlight, water, soil, space, etc. is interspecific competition. 1. With intense competition for limited resources, one species may improve its efficiency at acquiring resources or food. Over a long time scale, resource partitioning can occur, allowing species to utilize shared resources at different times, in different ways, or in different places. 2. As humans take more and more space, other species are compromised. B. Consumers often feed on live organisms of other species. 1. Predator-prey relationships define one animal (the predator) feeding/preying on another. In populations, these relationships play an important role in evolution by natural selection. 2. Parasites live on or in another species. The host of this arrangement is often harmed, but the parasite can contribute to biodiversity by controlling the size of specific species populations. 3. Mutually beneficial interactions also exist in ecological environments. a. Mutualism is a relationship that benefits both species; these benefits can be dispersing pollen and seeds for reproduction, receiving food, or receiving protection. While not cooperation, each species benefits from the relationship. 4. Some species interaction helps one species but does nothing for the other; this is commensalism. 4-3 How Do Communities and Ecosystems Respond to Changing Environmental Conditions? A. With new environmental conditions, one group of species can be replaced by another. 1. Ecological succession is the gradual change in species composition of a given area. 2. Primary ecological succession is the gradual establishment of biotic communities on lifeless ground; in the soil there is no terrestrial community; in an aquatic community, there is no bottom sediment. This can take hundreds to thousands of years due to the need to build up the necessary nutrients in the soil. 3. Secondary ecological succession defines a series of communities with different species developing in places that already have soil or bottom sediment. This occurs where an ecosystem has been disturbed, removed, or destroyed. B. The classic view of ecological succession is that it is an orderly sequence, each stage leading to a next, more stable stage until a climax community is reached. Such a community would represent the balance of nature, one dominated by a few long-lived plant species that is in balance with its environment. C. However, the classic view described above does not seem to represent true, evolving ecological communities. Ecological communities are ever-changing mosaics of vegetation patches at different stages of succession. 4-4 What Limits the Growth of Populations? A. Four variables influence/govern population size: births, deaths, immigration, and emigration. 1. The biotic potential is the population’s capacity for growth under ideal conditions. 2. The intrinsic rate of increase (r) is the rate of population growth if it had unlimited resources. 3. Rapid growing populations have four characteristics: a. Individuals in the population reproduce early in life. b. Individuals have short periods between generations. c. Individuals can reproduce many times. d. Individuals have multiple offspring each time they reproduce. B. Environmental resistance consists of factors that limit population growth. 1. Carrying capacity is determined by biotic potential and environmental resistance. This is the number of a species’ individuals that can be sustained indefinitely in a specific space. 2. As a population reaches its carrying capacity, its growth rate will decrease. a. With few resource limitations, a population will have exponential growth. This will be slow growth with more and more rapid growth; there will be a J-shaped growth curve that represents its intrinsic rate of increase (r) or biotic potential. b. This exponential growth is converted to logistic growth when the populations gets larger and faces environmental pressure. In logistic growth, the growth rate decreases. 3. The sigmoid (s-shaped) population growth curve shows that the population size is stable, at or near its carrying capacity. C. When population size exceeds its carrying capacity, organisms die unless they move or switch to new resources. 1. Exponential growth leads to logistic growth and may lead to the population overshooting the environment’s carrying capacity. a. Overshooting an environment’s resources often is a result of a reproductive time lag. b. The reproductive time lag can produce a dieback/crash of organisms unless the organisms can find new resources or move to an area with more resources. 2. If the carrying capacity of an area is exceeded, changes in the area itself can reduce future carrying capacity. Reducing grass cover by over-grazing allowed sagebrush to move in and reduce the number of cattle that the land could support. 3. Technological, social, and cultural change has extended the earth’s carrying capacity for human beings, for the time being. D. Reproductive patterns of species influence carrying capacity. 1. Opportunists have many offspring and disperse rapidly; they have ‘boom-and-bust’ cycles. 2. Competitor species reproduce late in life and have fewer offspring who need long-term nurturing. Those of this species who have long generation times and few offspring are prone to extinction. 4-5 What Factors Influence the Size of the Human Population? A. Three major factors account for the recent, rapid expansion of the human population. 1. Humans developed the ability to expand into diverse new habitats and climate zones. 2. Modern agriculture allowed more people to be fed. 3. Sanitation, antibiotics, and vaccines helped control infectious disease, dropping death rates below birth rates. 4. 98% of the world's population growth is occurring in middle- and low-income, less-developed countries, places least equipped to handle the pressures of rapid population growth. B. Population increases through births and immigration and decreases through deaths and emigration. [Population Change = (Births +Immigration) – (Deaths – Emigration)] 1. The crude birth rate is the number of live births per 1,000 people in a population in a specific year. 2. The crude death rate is the number of deaths per 1,000 people in a population in a specific year. C. Fertility rate is the number of births that occur to an individual woman, and this rate affects the country’s population size and growth rate. 1. Replacement-level fertility is the number of children needed to replace their parents. 2. Total fertility rate (TFR) is the average number of children that women have during their reproductive years. 3. See Case Study: The U.S. Population – Third Largest and Growing D. Many factors influence birth and fertility rates. 1. The importance of children as part of the labor force – this is especially true in developing countries. 2. The economic cost of raising and educating children – in more developed countries, the cost of raising children is higher because they do not enter the workforce until their teens or twenties. This high cost tends to keep birth rates lower. 3. If private/public pension systems are available, adults have fewer children because they don’t need children to take care of them in old age. 4. If infant mortality rate is high people have more children to ensure survival of at least a few. 5. People in urban areas usually have better access to family planning services – thereby having fewer children. 6. Total fertility rates are lower when women have access to education and employment opportunities; these women also tend to marry later in life. 7. If abortions are available and legal, women have fewer children. Also, if reliable birth control methods are available, women are able to control the number and spacing of children they have. 8. Religious beliefs, traditions, and cultural norms also influence birth rates. E. The rapid population growth in the past 100 years is due primarily to a decline in death rates 1. Better food supplies, nutrition, and safer water supplies contribute to people living longer. 2. Advances in medicine and public health, and improved sanitation and personal hygiene also contribute to people living longer. 3. Infant mortality reflects a country's general level of nutrition and health care. 4. While infant mortality rates have declined in recent years, more than 4 million infants die of preventable causes each year, primarily in less-developed countries. F. Migration influences population change 1. Most people migrate to seek jobs and economic improvement. 2. Religious persecution, ethnic conflicts, wars, political oppression, and similar events cause people to migrate. G. Population age structure affects population growth or decline 1. The percentages of male and females in the total population are divided into the following age categories: a. PR reproductive ages span birth to 14 years of age. b. Reproductive ages include 15 through 44. c. Post reproductive ages include ages 45 and up. 2. The major determiner in future population growth is the number of people under 15 who are just entering their reproductive years. In 2012, this age group was about 26% of the world's population. 3. The fastest growing population are seniors, age 65 and up. 4. See Case Study: The American Baby Boom for analysis of the economic and societal impact of changes in age group distribution. H. Reduced fertility and population decline has long-term consequences, especially if the decline is rapid. 1. There can be a sharp rise in the proportion of older people, resulting in higher costs for health care and pension funds being funded by a decreasing number of younger, working taxpayers. I. Deaths from AIDS have disrupted social and economic structures by removing a significant number of young adults from the population. 4-6 How Can We Slow Human Population Growth? A. Can the world sustain a rising population without causing widespread environmental damage? This debate is one of the most important and controversial issues in environmental science. 1. No, the current population is already degrading the earth's natural capital, and we cannot provide basic necessities for 1.4 billion people (1 out of 5), so how will we be able to provide an adequate standard of living for 2.5 billion more? 2. Yes, as technological advances have allowed humans to overcome the environmental resistance to increase the carrying capacity for people. 3. Regulating population goes against some religious or moral beliefs. Others view it as an intrusion to privacy and personal freedoms. 4. If we do not slow population growth: a. Death rates may increase because of declining health and environmental conditions in some areas. b. Resource use and environmental harm will increase. B. The demographic transition hypothesis states that as countries become industrialized, first their death rates and then their birth rates decline in four stages. 1. The preindustrial stage produces high birth and death rates because living conditions are harsh. 2. The transitional state sees food production rise and improvement in health care. Death rates drop and birth rates rise. 3. The industrial stage causes the birth rate to begin to drop and the death rate drops because industrialization, medical advances, and modernization are widespread. 4. The postindustrial stage moves to the birth rate equaling the death rate and results in zero population growth. Population size will begin slowly decreasing. C. Some countries run the risk of getting caught in the transitional state, with economic conditions unable to sustain the population. 1. There can be a shortage of skilled workers to sustain the country’s economy. 2. There will not be capital and resources to support rapid developing economies. a. International debt takes much of a country’s resources. b. Developing countries are not helping underdeveloped countries economically. D. Empowering women helps to slow population growth. 1. Women do almost all the world's domestic work and child care, including 60-80% of the work associated with growing food, gathering and hauling fuel, and hauling water. 2. Sons are more valued in many societies, and girls are kept home to work instead of being sent to school. E. Family planning helps reduce the number of births and abortions throughout the world, yet challenges remain. 1. According to the UN Population Fund, 42% of all pregnancies in less-developed countries are unplanned. 2. An estimated 215 million couples in less-developed countries want to limit the number of children but lack access to family planning services. 3. See Case Studies: Slowing Population Growth in China: The One Child Policy and India’s Attempt to Slow Its Population Growth. Teaching Tips 1. Do not underestimate the power of repetition. Repetition of key concepts can reinforce the learning objectives of the course and assist learners in transferring that learned knowledge from their short-term to long-term memory. Without repetition learners can easily forget the information presented to them. Using the learning objectives outlined at the beginning of each chapter may help you decide which points to focus on. 2. Repetition means more than just repeating the same key information in the same way. Rather, consider using creative strategies to reinforce the previously learned information in new ways. For example, reading, writing, lecturing, presenting, researching, playing jeopardy, making flash cards, taking a quiz, and doing group work constitute repetition when they are focused on the same key ideas. These are just a few examples. 3. An especially important piece to repetition is having each student individually write or verbalize the key concepts. Once students are capable of doing this, the information has been internalized deeper than simple recognition. Be aware, if students are having a difficult time recalling the information it may indicate that they don’t fully understand the concept(s). If students don’t understand the key concepts, then they won’t be able to remember them. 4. Don’t view repetition of key concepts as something confined to a single class meeting. Instead, repetition of concepts should be something that is continually built upon as the course progresses. Begin by selecting a few main concepts and terms each class period that can then be frequently revisited later on in the course. Continue to incorporate these concepts and terms into subsequent class meetings. 5. The three scientific principles of sustainability (revisited at the end of each chapter) would also be excellent focal points to come back to during each class meeting. Helping students move from simple recognition of these principles to deeper, meaningful knowledge will enable them be environmental stewards long after this course has ended. Topics for Term Papers and Discussion Conceptual Topics 1. Niche: relationships among species in a particular ecosystem; pick-a-predator; resource partitioning versus direct competition strategies. 2. Unusual niches: write a case study of a particular alien species, indicator species, or keystone species. 3. Competition and predation: important features of natural selection, the competitive exclusion principle. 4. Making peace in natural ecosystems: resource partitioning, symbiotic relationships. 5. Ecological succession: the role of humans in succession, the role of fires (or other natural disasters) and chaos in determining succession. 6. Nature’s response to human activities. Succession on deserted farmlands; succession after fire; dilution of pollution by streams; species migration; a closer look at homeostatic systems; population crashes; pioneer species; problems with crop monocultures. 7. Fragile ecosystems: deserts, tropical forests, tundra. Attitudes & Values 1. Has your local ecosystem been invaded by a nonnative species? If so, how did you feel about the invasion? About methods to control its expansion? 2. How do you feel toward indicator species? Keystone species? Do predators fulfill a valuable ecological function or should their numbers be reduced? 3. Do you have any particular feelings toward relationships demonstrated in ecosystems? Competition? Predation? Commensalism? Parasitism? Mutualism? 4. How do you feel when you observe grass emerging from a sidewalk or paved parking lot? 5. How do you feel when you observe lichens growing on a bare rock? 6. How do you feel toward fire in natural ecosystems? Should we pursue fire-prevention approaches or leave wild lands in their natural states? Should we let wildfires burn or should we actively extinguish them? 7. How do you feel toward mature ecosystems? Immature ecosystems? 8. Do you feel any responsibility to protect natural ecosystems? Would you support the preservation of representative ecosystems? If so, on what basis? 9. Have you ever suffered from environmental stress? If so, were you able to respond to the stress? Please describe. 10. Is there evidence of environmental stress in your community? If so, is there evidence of ecosystem responses to stress in your community? How do you feel when you see an ecosystem under stress? 11. What lessons for human societies can be drawn from a study of species interaction in ecosystems? 12. To what extent should we disrupt and simplify natural ecosystems for our food, clothing, shelter, and energy needs and wants? Action-Oriented Topics 1. Research management strategies for predator control; consider places where predators have been re-introduced (wolves in Yellowstone, for example) 2. Research wildlife management strategies that rely on human control of successional stages of development. 3. Field methods of ecological research: relationships among species; computer modeling of ecological interrelationships. 4. Restoration of degraded ecosystems such as Lake Erie; coastal zone management. Activities and Projects 1. As a class, investigate an invasion of a nonnative species in your community. Research the species and contribute to a plan to prevent its impact on natural ecosystems. 2. As a class, investigate hunting, trapping, and predator control issues in your community. Evaluate current regulations and management strategies. Make proposals for change that seem necessary and appropriate to you. 3. As a class exercise, systematically study a modern freeway or interstate highway and trace its impact on the surrounding land in terms of succession. 4. Find works of literature, art, and music that depict species interactions in natural ecosystems. Draw as many parallels between species interaction and your own experiences as you can. 5. Arrange a field trip providing opportunities to compare and contrast ecosystems of several different types, including some damaged or stressed by human activities. Invite an ecologist or biologist along to identify and discuss specific examples of species adaptation to environmental conditions. Do the boundaries between different kinds of ecosystems tend to be sharply delineated? Can you identify factors that limit the growth of certain species? 6. Organize a class field trip to systematically investigate the ecological niches for plant and animal life existing in a landscape significantly modified by human activities. If possible, arrange to travel along a gradient that will take you from farmland to suburbs to city to central business district. (A simplified version of this exercise could be done by walking around campus.) 7. Find works of literature, art, and music that show human attachment to different ecosystems and destruction and stressing of natural ecosystems. Lead a class discussion on the subject of how human culture has been shaped to an important degree by the environmental conditions of each major biome. 8. Organize a class trip to an abandoned field, coastal dune, rock outcrop, or other disturbed area and observe the various aspects of ecological succession. If possible, visit and compare two areas that have experienced different types of disturbance. 9. Arrange a field trip providing opportunities to compare and contrast relatively pristine ecosystems with some damaged or stressed ecosystems. Invite an ecologist or biologist along to identify and discuss specific examples of species adaptation to environmental conditions. Can you identify factors that limit the growth of certain species? 10. Have your class secure a large jar or glass container and equip it with a ventilated (finely perforated or meshed) top. Place a male and a female fruit fly in it, together with a plentiful supply of food. Set the jar aside and monitor the fly population as the days pass. Why does the population increase slowly at first and then very rapidly? What causes the inevitable population collapse? Why do all of the flies, rather than just the “surplus” population, die? BBC News Videos The Brooks/Cole Environmental Science Video Library with Workbook, Featuring BBC Motion Gallery Video Clips, 2011. DVD ISBN: 978-0-538-73355-7 (Prepared by David Perault) Kalahari Desert Could Double in Size Half the World Denied Basic Sanitation Darwin's Galapagos Under Threat China's Deadly Pollution How Exotic Species Are Devastating Hawaii's Native Fauna Are We Facing an Extinction Crisis? Suggested Answers for Critical Thinking Questions 1. Biodiversity is what holds the diversity of life on the planet. This includes not only the obvious species and ecosystems, but also the genetic diversity within. Losing this diversity may have immediate short term effects or the losses may be unknown to us. Though extinction is a natural process, the rate of extinction has increased dramatically in human time. It is important to the future of the planet to maintain as much biodiversity as possible. 2. Student answers will vary. A strong argument for saving amphibians is that they represent a highly diverse group that occupy many different niches worldwide and their loss could have widespread effects. The Giant Panda is limited in niche and geographic range and its loss may not have as large of an effect on global ecosystems. 3. Species with a high biotic potential tend to be small sized, as opposed to the large-sized low biotic potential species, because they reproduce early in life, have shorter generation times, and can reproduce large number of offspring each time they reproduce. Their small size means they require less energy as well. Larger animals tend to eat at a higher trophic level, requiring much more total energy input to meet their needs. It also takes more energy for these animals to successfully give birth, so incubation times tend to be long, and few offspring are born each time. 4. You can identify a keystone species by the niche it holds. Keystone species may help create habitats and ecosystems for other organism; however, they also play an important role in maintaining the function of these ecosystems. If a species is a keystone species, you will see population crashes if the species is disturbed. 5. Student answers will vary. One example can be nutrient inputs into estuaries from our waterways, and the associated impacts on ecosystem structure and function, as the human population increases. 6. Student answers will vary. A few factors from the chapter to consider include: • The cost of raising and educating children • Accessibility of birth control • Access to health care • Education and employment opportunities for women • Religious beliefs, traditions, and cultural norms • Can technology continue to increase the earth’s carrying capacity? 7. Student answers will vary, but they should recognize the complexity of developed nations changing our habits to truly decrease our ecological footprint. There is significant difficulty in developed nations coming in to dictate how people in developing countries “should” live, especially given the completely disparate cultures in which these two societies operate. Instructor Manual for Sustaining the Earth G. Tyler Miller, Scott E. Spoolman 9781285769493
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