HUMANS AND SUSTAINABILITY: AN OVERVIEW



HUMANS AND SUSTAINABILITY: AN OVERVIEWChapter 1Environmental Problems, Their Causes, and SustainabilitySummary1.All life depends on energy from the sun, solar capital, and the resources and ecological services of the earth, natural capital, to survive. An environmentally sustainable society provides for the current needs of its people without undermining the ability of future generations to do the same.2.The world’s population is growing exponentially, adding about 80 million people per year. Economic growth increases a country’s capacity to provide goods and services to its people. Economic development uses economic growth to improve standards of living. Globalization is a process of increasingly interconnecting people through social, economic, and environmental global changes.3.The earth’s main resources are perpetual resources like solar energy, renewable resources like forests and fresh water, and nonrenewable resources like oil and gas. The resources can be depleted or degraded by overuse, by waste, by pollution, and by man’s increasing “ecological footprint.”4.The principle types of pollution are air, water, soil, and food pollutants. We can prevent pollution or clean up pollution. Prevention is far preferable because cleaning up pollution often causes additional pollutants in another part of the environment.5.The basic causes of today’s environmental problems are population growth, wasteful use of resources, the tragedy of the commons, poverty, poor environment accounting, and ecological ignorance. They are interconnected because of political and economic practices that are not equitable for various populations, in resource consumption and in technological applications. 6.The world’s current course is not sustainable. Environmental sustainable development encourages environmentally beneficial forms of economic growth and discourages environmentally harmful growth.Key Questions and Concepts1-1 What are three principles of sustainability?CORE CASE STUDY. Contemporary society faces many environmental problems. Sustainability is the capacity of natural systems and cultural systems to survive and flourish indefinitely. As we look to the future, our actions today are pivotal to our ultimate sustainability. The environment is everything around us. Environmental science is an interdisciplinary study of how humans interact with their environment. Three goals of environmental science are:to learn how nature works.to understand how we interact with the environment.to find ways to address environmental problems and embrace sustainability.Ecology studies relationships between living organisms and their environment.Environmentalism is a social movement dedicated to protecting life support systems for all species.A path toward sustainability includes three overarching themes:Reliance on solar energy.Biodiversity.Chemical or nutrient cycling.Natural capital is the natural resources (materials and energy in nature) and natural services (natural processes) that support ecosystems and economies.Resources are that which can be taken from the environment to meet our needs or wants.Perpetual resources are continuously available (sunlight)Renewable resources can be replenished in the foreseeable future (forests, fertile topsoil).Non-renewable resources are found in fixed quantities and are not renewable on a human time scale. Economic growth is an increase in a nation’s output of goods and services, measured by gross domestic product (GDP). Economic development uses economic growth to improve living standardsMore developed countries make up 20% of the world’s population and use 88% of all resources. 1-2 How Are Our Ecological Footprints Affecting the Earth?A.The process of depleting resources is known as environmental degradation or natural capital degradation.B.Pollution is any presence in the environment that is harmful to health or survival or humans or other organisms.1. Point sources are single identifiable sources; non-point sources are dispersed.2. Biodegradable pollutants break down over time and nonbiodegradable pollutants cannot break down.3. Pollutants can have three kinds of effects:Disrupt or degrade life-support systems for humans or other species.Damage wildlife, human health, or property.Create nuisances.There are two ways to deal with pollution:Pollution cleanup.Pollution prevention.C.The Tragedy of the Commons describes the overuse or degradation of freely available resources. The cumulative effect of many users exploiting a common resource can degrade it such that no one can benefit from it. D.Ecological footprint1.The amount of biologically productive land and water needed to supply renewable resources and absorb waste for people in a given area.2.Humanity’s ecological footprint exceeds by at least 30% the earth’s biological capacity to support life.E. IPAT summarizes environmental impact1. Impact (I) = Population (P) x Affluence (A) x Technology (T).CASE STUDY: The number of affluent consumers is rising rapidly, as people in underdeveloped countries attain a middleclass lifestyle. China is already a leading consumer of many resources, and its economy and population are continuing to grow at a rapid rate. Thus, its ecological footprint and overall level of resource consumption are expected to continue to grow.F. Ecological tipping point refers to an irreversible shift in the behavior of a natural system. We currently face three potential tipping points:1. Collapse of fish populations from overfishing.2. Species extinction from overharvesting and habitat destruction.3. Climate change from burning coal and oil. G. Culture describes a society’s knowledge, beliefs, technology and practices.1. Three major cultural changes have occurred in human historyAgricultural revolution: 10,000 – 12,000 years ago when people began growing and breeding plants.Industrial-medical revolution: 275 years ago machines and medical advances improved rmation-globalization revolution: 50 years ago new technologies allow for global communications and trade. A fourth, called the sustainability revolution, is advocated by many environmental scientists.1-3 Why do we have environmental problems?A.Four major causes of environmental problems are:1.Population growth.2.Wasteful resource use.3.Poverty.4.Poor environmental accounting.B. Exponential growth occurs when a population increases by a fixed percentage per unit of time.There are roughly 6.9 billion people on earth in 2010. There may be as many as 9.3 billion by 2050. No one knows how many people the Earth can support. Affluence results in high levels of consumption.1. Affluence can lead to an unsustainable addiction to acquiring material things.2. Affluence can lead to better education, improved health, and more resources to address environmental issues.D. Poverty occurs when people are unable to fulfill their basic needs.1. 1/5 of the world population lives in extreme poverty.2. Poverty conditions in heavily populated areas can have significant environmental impacts.3. Pollution and environmental degradation can have severe impacts on the poor. Three significant health issues are:a. malnutritionb. inadequate sanitation and access to safe drinking waterc. respiratory disease E. Prices of goods do not include their harmful environmental costs.F.Environmental worldviews and ethics determine the way people view the seriousness of environmental problems.1.Your environmental worldview is your assumptions and values about the world and your role.2. Environmental Ethics are beliefs about what is right and wrong in our treatment of the environment. a.The planetary management worldview holds that nature exists to meet our needs.b.The stewardship worldview holds that we manage the earth, but we have an ethical responsibility to be stewards of the earth.c.The environmental worldview holds that we are connected to nature and that nature exists for all species equally.1-4 What is an environmentally sustainable society? An environmentally sustainable society meets the current and future basic resource needs of its people in a just and equitable manner by protecting natural capital and living off its income.1. The shift to sustainability involves building social capital, which involves bringing together people with different views and values and finding common ground. CASE STUDY: Chattanooga, Tennessee, was once one of the most polluted cities in the United States. In the mid-1980s civic leaders gathered together community members to identify problems and brainstorm solutions. After years of encouraging zero-emission industries, implementing recycling programs, and renovating much of the city, Chattanooga is an example of what can be accomplished when cities build their social capital. Individuals matter1. It takes only 5-10% of a community to bring about major social change.2. Significant social change can occur very rapidly. Additional Video ResourcesIndigenous Peoples: Humane and Environmental Sustainability (Documentary, 2005). A 45-minute documentary highlighting the thoughts and proposals of indigenous people. Habitable Planet: A Systems Approach to Environmental Science, Looking Forward: Our Global Experiment (Documentary, 2007). Focuses on ingenuity and cooperation as a means of attaining sustainable solutions. Earth: The Future Living Together (Documentary, 2007). The final episode of the Planet Earth series explores the intricacies of conservation and sustainability. the World (Documentary, 2000). Explores some of the biggest challenges facing us today,including urban sustainability . The 11th Hour (Documentary, 2008). A feature length film highlighting major environmental issues as well as approaches to sustainability.Web ResourcesRedefining Progress – Ecological Footprint Quiz and Sustainability Resources Community for the Environment – Many Resources Answers to End of Chapter QuestionsReview QuestionsReview the Key Questions and Concepts for this chapter on p. 6. What is sustainability and why should we care about it? What are the three principles that nature has used to sustain itself for 3.5 billion years, and how can we use these principles to live more sustainably? Sustainability is the capacity of the earth’s natural systems and human cultural systems to survive, flourish, and adapt to changing environmental conditions indefinitely. It is important that we embrace sustainability to ensure that future generations have access to adequate resources.The three principles are reliance on solar energy, biodiversity, and chemical cycling. These principles entail sustainability insofar as they guarantee that we will value and preserve biodiversity, live with renewable energy, and continue to recycle and reuse the earth’s valuable resources. Define environment. Distinguish among environmental science, ecology, and environmentalism. Distinguish between an HYPERLINK "javascript:void(0);" \o "header={}

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Any form of life.} hideselects={on} " organism and a species. What is an ecosystem? Define natural capital, HYPERLINK "javascript:void(0);" \o "header={}

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Materials such as air, water, and soil and energy in nature that are essential or useful to humans. See natural capital.} hideselects={on} " natural resources?, and natural services. Define nutrient cycling and explain why it is important? Describe how we can degrade natural capital and how finding solutions to environmental problems involves making trade-offs. Explain why individuals matter in dealing with the environmental problems we face. The environment is everything around us.Environmental science is an interdisciplinary study of how humans interact with living and nonliving parts of their environment.Ecology is the biological science that studies how organisms, or living things, interact with one another and with their environment. Environmentalism is a social movement dedicated to protecting the earth’s life-support systems for all forms of life.Every organism is a member of a certain species: a group of organisms that have distinctive traits and, for sexually reproducing organisms, can mate and produce fertile offspring. An ecosystem is a set of organisms within a defined area or volume interacting with one another and with their environment of nonliving matter and energy.Natural capital—the natural resources and natural services that keep us and other forms of life alive and support our economies.Natural resources are materials and energy in nature that are essential or useful to humans. These resources are often classified as renewable (such as air, water, soil, plants, and wind) or nonrenewable (such as copper, oil, and coal). Natural services are processes in nature such as purification of air and water, which support life and human economies. Nutrient cycling is the circulation of chemicals necessary for life, from the environment (mostly from soil and water) through organisms and back to the environment. This is a vital natural service because without it nutrients would become unavailable to living organisms.We can degrade natural capital by overharvesting, or unsustainably managing resources. Solutions often involve conflicts necessitating trade-offs. Individuals matter in dealing with environmental problems because what we all do on a daily basis has an overall impact. What is a resource? Distinguish between a perpetual resource and a renewable resource and give an example of each. What is sustainable yield? Define and give two example of a nonrenewable resource. Distinguish between recycling and reuse and give an example of each. What is HYPERLINK "javascript:void(0);" \o "" economic growth? Distinguish between gross domestic product (GDP) and per capita GDP. Distinguish between more-developed countries and less-developed countries and give an example of a high-income, a middle income and a low-income country. Perpetual resources have continual supplies, and renewable resources will be replenished as long as we do not use them too rapidly. Solar energy is perpetual and wood resources are renewable. Sustainable yield is the highest rate at which a resource can be used without indefinitely reducing it’s available supply.Nonrenewable resources are resources that exist in a fixed quantity such as copper or oil. Reuse involves using a resource over and over as in washing a reusing a bottle. Recycling entails collecting materials and processing them into new materials, as in melting discarded aluminum cans to make new aluminum products. Economic growth is the increase in the capacity to provide people with goods and services; an increase in gross domestic product (GDP). Economic growth is usually measured by the percentage of change in a country’s gross domestic product (GDP): the annual market value of all goods and services produced by all firms and organizations, foreign and domestic, operating within a country. Changes in a country’s economic growth per person are measured by per capita GDP: the GDP divided by the country’s total population at midyear. GDP and per capita GDP indicators provide a standardized and useful method for measuring and comparing the economic outputs of nations. The GDP is deliberately designed to measure such outputs without distinguishing between goods and services that are environmentally or socially beneficial and those that are harmful. The United Nations classifies countries as economically developed or developing based primarily on their degree of industrialization and their per capita GDP PPP. Most developed countries are highly industrialized and have a high per capita GDP PPP. Some developing countries are middle- income and moderately developed while others are low-income and least developed. The United States is a high-income country, Brazil is a middle-income country, and Haiti is a low-income country. Define and give three examples of environmental degradation (natural capital degradation). Define pollution. Distinguish between point source and nonpoint sources of pollution. Distinguish between pollution cleanup (output pollution control) and pollution prevention (input pollution control) and give an example of each. Describe three drawbacks to solutions that rely mostly on pollution cleanup. What is the tragedy of the commons? Natural capital degradation involves using resources at an unsustainable rate. Examples include forests shrinking, topsoil eroding and deserts expanding. Pollution is a presence in the environment that is harmful to the health, survival or activities of humans or other organisms. Point sources have single identifiable sources, whereas nonpoint sources are dispersed. Output control involves cleaning up after the pollutants have been released. And may involve physically removing a pollutant from the environment, while input control involves reducing or eliminating the production of pollutants, which may involve trapping the pollutants before they are released and then properly disposing of them. The drawbacks of cleanup are that it may be a temporary “bandage,” cleanup may involve simply displacing the pollutant to another environment, and it may be too costly to reduce the chemicals to acceptable levels. The tragedy of the commons is environmentally degrading many openly shared renewable resources. What is an ecological footprint? What is a per capita ecological footprint? Compare the total and per capita ecological footprint s of the United States and China. Use the ecological footprint concept to explain how we are living unsustainably. What is the IPAT model for estimating our environmental impact? Explain how we can use this model to estimate the impacts of the human populations in less-developed countries and more developed countries. Describe the environmental impacts of China’s new affluent consumers. What is an ecological tipping point?Ecological footprint refers to the amount of biologically productive land and water needed to provide the people in a particular country or area with an indefinite supply of renewable resources and to absorb and recycle the wastes and pollution produced by such resource use. The per capita ecological footprint is the average ecological footprint of an individual in a given country or area.The total ecological footprint for the United States in millions of hectares is 2810 versus 2050 for China. The U.S. per capita ecological footprint was about 6 times larger than China’s per capita footprint.We are living unsustainably by over extracting resources, and not allowing adequate time for the processes of recycling and regeneration. Impact (I) = Population (P) × Affluence (A) × Technology (T)In less-developed countries, population tends to be a larger issue, while consumption is less of an impact. On the other hand, in more-developed countries, it is consumption that drives up the overall impact, with population being less of an issue. Technologies can either increase or reduce the overall impact in both cases. China’s newly affluent consumers are putting immense pressure on the earth’s potentially renewable natural capital and its nonrenewable resources.An ecological tipping point is a threshold level which causes an often irreversible shift in the behavior of a natural system.Define culture? Describe three major cultural changes that have occurred since humans were hunter-gatherers. What would a sustainability revolution involve? Culture is the whole of a society’s knowledge, beliefs, technology, and practices, and human cultural changes have had profound effects on the earth. Three major cultural changes have occurred during mankind's history. First was the agricultural revolution when humans learned how to grow and breed plants and animals for food, clothing, and other purposes. Second was the industrial– medical revolution when people invented machines for the large- scale production of goods in factories. This involved learning how to get energy from fossil fuels, such as coal and oil, and how to grow large quantities of food in an efficient manner. Finally, in the information– globalization revolution we developed new technologies for gaining rapid access to much more information and resources on a global scale.An environmental, or sustainability, revolution would involve learning how to reduce our ecological footprints and live more sustainability. Identify four basic causes of the environmental problems that we face today. What is exponential growth? Describe the past, current, and projected exponential growth of the world’s human population. What is affluence? How do Americans, Indians, and the average people in the poorest countries compare in terms of consumption? What are two types of environmental damage resulting from growing affluence? How can affluence help us to solve environmental problems? What is poverty and what are three of its harmful environmental and health effects? Describe the connection between poverty and population growth. Some basic causes of environmental problems are: Population growth.Unsustainable resource usePoverty.Exclusion of harmful environmental costs from the market prices of goods and services.Exponential growth occurs when a quantity such as the human population increases at a fixed percentage per unit of time.The exponential rate of global population growth has declined some since 1963. Nevertheless, unless death rates rise sharply, there will probably be 9.3 billion of us by 2050 (up from 6.9 in 2010). Affluence is wealth that enables the consumption of large amounts of resources far beyond basic needs.The average American consumes about 30 times as much as the average Indian and 100 times as much as the average person in the world’s poorest countries. Growing affluence results in high levels of consumption and unnecessary waste of resources.Affluence can allow for better education, which can lead people to become more concerned about environmental quality. It also provides money for developing technologies to reduce pollution, environmental degradation, and resource waste.Poverty occurs when people are unable to meet their basic needs for adequate food, water, shelter, health, and education. Poverty has a number of harmful environmental and health effects. People who are desperate for short- term survival people deplete and degrade forests, soil, grasslands, fisheries, and wildlife, at an ever- increasing rate. They do not have the luxury of worrying about long- term environmental quality or sustainability. Other problems include malnutrition and lack of access to clean drinking water. Poverty can drive population growth, as people in poor regions often have more children to ensure that they will have assistance with daily work as well as someone to care for them in old age. Explain how excluding from the prices of goods and services the harmful environmental costs of producing them affects the environmental problems we face. What is the connection between government subsidies, resource use, and environmental degradation? What is an environmental worldview? What are environmental ethics? Distinguish among the planetary management, stewardship, and environmental wisdom worldviewsExcluding the harmful environmental costs in the prices of goods and services can hurt the environment because the consumer does not realize the value being lost.Environmentally harmful subsidies encourage the depletion and degradation of natural capital.Environmental worldview is a set of assumptions and values reflecting how you think the world works and what you think your role in the world should be. Environmental ethics are beliefs about what is right and wrong with how we treat the environment. World view:The planetary management worldview holds that we are separate from and in charge of nature, that nature exists mainly to meet our needs and increasing wants, and that we can use our ingenuity and technology to manage the earth’s life-support systems, mostly for our benefit, indefinitely.The stewardship worldview holds that we can and should manage the earth for our benefit, but that we have an ethical responsibility to be caring and responsible managers, or stewards, of the earth. It says we should encourage environmentally beneficial forms of economic growth and development and discourage environmentally harmful forms. The environmental wisdom worldview holds that we are part of, and dependent on, nature and that nature exists for all species, not just for us. Describe an environmentally sustainable society. What is natural income? What is social capital? Describe the environmental transformation of Chattanooga, Tennessee.An environmentally sustainable society is one that meets the current and future basic resource needs of its people in a just and equitable manner without compromising the ability of future generations to meet their basic needs. Natural income is the renewable resources such as plants, animals, and soil provided by the earth’s natural capital.Building social capital involves getting people with different views and values to talk and listen to one another, to find common ground based on understanding and trust, and to work together to solve environmental and other problems facing our societies.Chattanooga’s story shows that a key to finding solutions to environmental problems is to recognize that most social change results from individual actions and individuals acting together (using social capital ) to bring about change through bottom- up grassroots action. How long do some scientists estimate that we have to make a shift to more environmentally sustainable economies and lifestyles? Based on the three principles of sustainability, what are the three best ways to make such a transition as summarized in this chapter’s three big ideas? Explain how we can use these three principles to get us closer to the vision of a sustainable earth described in the Core Case Study that opens this chapter.Many scientists argue that we must make changes now, as many would take as long as 50 years to take effect. Rely more on renewable energy, protect biodiversity, and help to sustain the earth’s natural chemical cycles by reducing the production of wastes and pollution.These strategies can help to reduce our ecological footprints, sustain the earth’s natural capital, and make a transition to more sustainable lifestyles and economies.Critical ThinkingThe following are examples of the material that should be contained in possible student answers to the end of chapter Critical Thinking questions. They represent only a summary overview and serve to highlight the core concepts that are addressed in the text. It should be anticipated that the students will provide more in-depth and detailed responses to the questions depending on an individual instructor’s stated expectations.Do you think that you are living unsustainably? Explain. If so, what are the three most environmentally unsustainable components of your lifestyle? List two ways in which you could apply each of the three principles of sustainability (Figure 1-3) to making your lifestyle more environmentally sustainable.Answers may vary. Some examples include reducing energy consumption and relying more heavily on solar energy, reducing resource use and recycling when possible, and advocating a reduction in population growth. Do you believe a vision such as the one described in the Core Case Study that opens this chapter is possible? Why or why not? What, if anything, do you believe will be different from that vision? Explain. If your vision of what it will be like in 2060 is sharply different from that in the Core Case Study, write a description of your vision. Compare your answers to this question with those of your classmates. Student answers will very based upon perspective.For each of the following actions, state one or more of the four scientific principles of sustainability (Figure 1-17) that are involved: (a) recycling soda cans; (b) using a rake instead of a leaf blower; (c) walking or bicycling to class instead of driving; (d) taking your own reusable bags to the grocery store to carry your purchases home; (e) volunteering to help restore a prairie; and (f) lobbying elected officials to require that 20% of your country’s electricity be produced by renewable wind power by 2020. (a) Nutrient Recycling/Reliance on Solar Energy: In nature there is no waste, so recycling the aluminum soda can mimics nutrient recycling. As less energy is used in the aluminum recycling process than starting from raw materials such as bauxite, we are less dependent on nonrenewable energy sources.(b) Reliance on Solar Energy: As no electrical or gasoline energy is expended by using the rake, we are less dependent on nonrenewable energy sources such as coal to generate the electricity to power the leaf blower.(c) Reliance on Solar Energy/Biodiversity: By not using gasoline to drive the car, you are relying more on renewable rather than nonrenewable energy and positively impacting biodiversity in areas where oil drilling is having harmful ecological effects.(d) Nutrient Recycling/Biodiversity/Reliance on Solar Energy: If you use a reusable grocery bag made from organically grown cotton, you will be relying on solar energy rather than nonrenewable energy sources that may have been used to make a plastic bag, which may or may not be recyclable; using paper bags can have an effect on the biodiversity of forest lands. (e) Biodiversity/Nutrient Recycling: By restoring habitat you will be enhancing biodiversity and also helping the future recycling of nutrients from the plantings.(f) Reliance on Solar Energy/Biodiversity: Promoting the use of renewable energy sources complies with the principle of relying on solar energy, and less reliance on nonrenewable sources such as coal and oil that adversely affect biodiversity in the extraction of these materials.Explain why you agree or disagree with the following propositions: a. Stabilizing population is not desirable because without more consumers, economic growth would stop. b. The world will never run out of resources because we can use technology to find substitutes and to help us reduce resource waste.Student answers will vary depending on their viewpoint but could include:a. Disagree: The earth has a finite amount of resources. With ever-increasing numbers of consumers the economy may eventually max out as these resources are diminished and the costs skyrocket. This would lead to greater disparity between rich and poor people and end up promoting increased poverty rather than increased wealth.b. Agree: Companies like 3M have reduced their waste by selling their generated waste products to other companies that need the materials for the manufacturing processes for goods that they produce. With an increase in such technology in the future, more materials have the potential to be reused and recycled indefinitely. What do you think when you read that: (a) the average American consumes about 30 times more resources than the average citizen of India, and (b) human activities are projected to make the earth’s climate warmer? Are you skeptical, indifferent, sad, helpless, guilty, concerned, or outraged? Which of these feelings help perpetuate such problems, and which can help to solve them?Again student answers will vary, but the benefit of such questions is that the instructor can facilitate a discussion that could help the students come to terms with the feelings they have on the issue and take the necessary steps to minimize their own ecological footprint. The instructor can help the students see how answers such as being indifferent to the issue, as in (b), lead to a perpetuation of the problem, and answers such as (f) may bring about a change in their own lifestyle. When you read that about 16,400 children age five and younger die each day (13 per minute) from preventable malnutrition and infectious disease, how does it make you feel? Can you think of something that you and others could do to address this problem? What might that be?Student answers will vary. The instructor could lead a discussion in which each student is asked to explain their answer. Through this discussion students be spurred into action.Explain why you agree or disagree with each of the following statements: (a) humans are superior to other forms of life, (b) humans are in charge of the earth, (c) the value of other forms of life depends only on whether they are useful to humans, (d) based on past extinctions and the history of life on the earth over the past 3.5 billion years, all forms of life eventually become extinct so we should not worry about whether our activities cause their premature extinction, (e) all forms of life have the inherent right to exist, (f) all economic growth is good, (g) nature has an almost unlimited storehouse of resources for human use, (h) technology can solve our environmental problems, (i) I do not believe I have any obligation to future generations, and (j) I do not believe I have any obligation to other forms of life. Student answers will vary and the instructor has the opportunity to lead a discussion where each student can elaborate on their own particular viewpoint. What are the basic beliefs of your environmental worldview? Record your answer. Then at the end of this course return to your answer to see if your environmental worldview has changed. Student answers will vary. This question provides the instructor with the basis for a discussion on individual worldviews and allows for each student to consider their own current beliefs. It is hoped that by the end of the course everyone in the class has gained a greater understanding of the environment and increased their environmental literacy. It also provides the instructor the chance to discuss specific actions individual members of the class can take to make sure that if they “talk the talk” they also “walk the walk” from an environmental perspective. This will help students to minimize their ecological footprint individually, as well as the class on the whole.Are the beliefs included in your environmental worldview (Question 8) consistent with your answers to question 7? Are your actions that affect the environment consistent with your environmental worldview? Explain.Student answers will vary. This question provides the instructor with further basis for a discussion on individual worldviews and allows for the exploration of the implications of the students’ individual actions.List two questions that you would like to have answered as a result of reading this chapter. Student answers will vary and will provide a good starting point for a class discussion.Ecological Footprint AnalysisIf the ecological footprint per person of a country or of the world (Figure 1-13) is larger than its biological capacity per person to replenish its renewable resources and absorb the resulting waste products and pollution, the country or the world is said to have an ecological deficit. If the reverse is true, the country or the world has an ecological credit or reserve. Use the data below to calculate the ecological deficit or credit for the countries listed and for the world. (For a map of ecological creditors and debtors see Figure 6, p. S000, in Supplement 8.)Place Per Capita Per CapitaEcological Ecological BiocapacityCredit (+)Footprint(Hectares per person)or Debit (-)(Hectares per person)(Hectares per person)World2.21.8-0.4United States9.84.7China1.60.8India0.80.4Russia4.40.9Japan4.40.7Brazil2.19.9Germany4.51.7United Kingdom[[Could be deleted to save space if needed]]5.61.6Mexico2.61.7Canada7.614.5Data from WWF Living Planet Report 2006 Which two countries have the largest ecological deficits? Why do you think they have such large deficits?Which two countries have an ecological credit? Why do you think each of these countries has an ecological credit?Rank the countries in order from the largest to the smallest per capita ecological footprint.AnswersPlace Per Capita Per CapitaEcological Ecological BiocapacityCredit (+)Footprint(Hectares per person)or Debit (-)(Hectares per person)(Hectares per person)World2.21.8-0.4United States9.84.7-5.4Canada7.614.5+6.9United Kingdom5.61.6-4.0Germany4.51.7-2.8Russia4.40.9-3.5Japan4.40.7-3.7Mexico2.61.7-0.9Brazil2.19.9+7.8China1.60.8-0.8India0.80.4-0.4Data from WWF Living Planet Report 2006 Which two countries have the largest ecological deficits? Why do you think they have such large deficits?The United States has an ecological deficit of -5.4 hectares per person, and the United Kingdom has an ecological deficit of -4.0 hectares per person. This is likely due to affluence and overconsumption.Which two countries have an ecological credit? Why do you think each of these countries has an ecological credit?Brazil has an ecological credit of +7.8 hectares per person and Canada has an ecological credit of +6.9 hectares per person. This may be due to low population sizes relative to available resources.Rank the countries in order from the largest to the smallest per capita ecological footprint.U.S.CanadaUnited KingdomGermanyRussiaJapanMéxicoBrazilChinaIndiaSCIENCE, ECOLOGICAL PRINCIPLES, AND SUSTAINABILITYChapter 2Science, Matter, Energy, and SystemsSummary1.Science is an attempt to discover the natural world’s order and use that in describing what is likely to happen in nature. Scientists ask a question or identify a problem to investigate. Then, they collect scientific data through observation and measurement. Experiments may be used to study specific phenomena.2.The major components of complex systems are environmental inputs, flows within the system, and outputs to the environment.3.The basic forms of matter are elements and compounds. Matter is useful to us as a resource because it makes up every material substance.4.The major forms of energy are kinetic energy and potential energy. Energy is useful to us as a resource because it moves matter.5.The Law of Conservation of Matter states that matter is neither created nor destroyed when a physical or chemical change occurs.6.Matter can undergo three types of nuclear changes: natural radioactive decay, nuclear fission, and nuclear fusion.7.The First Law of Thermodynamics states that in all physical and chemical changes, energy may be converted from one form to another but it is neither created nor destroyed. The Second Law of Thermodynamics states that when energy is changed from one form to another, there is always less usable energy left.8.These laws, then, show that energy goes from a more useful to a less useful form and that high-quality energy cannot be recycled. So, the quality as well as the quantity of our resources and our environment will be reduced.Key Questions and Concepts2-1 What do scientists do?CORE CASE STUDY. Controlled experiments involve an experimental group, in which a known variable is changed, and a control group, in which the variable is not changed. The example involves two drainages that were dammed. One was deforested and one left forested. The deforested landscape showed an increase in erosion and an increase in water flow carrying dissolved nutrients. Science assumes that events in the natural world follow orderly patterns and that, through observation and experimentation, these patterns can be understood.The scientific method used to learn about the world.Identify the problem.Find out what is known about the problem.Propose a question.Collect dataSuggest a hypothesis (possible explanation).Make testable projectionsTest with further experiments, models or observations.Models are approximate representations of a system.Support or reject hypothesis.A scientific theory is well-tested and widely accepted scientific hypothesis.Four important features of the scientific process are curiosity, skepticism, reproducibility, and peer review.Critical thinking entails three main steps.1. Be skeptical. 2. Evaluate available evidence.3. Identify and evaluate personal assumptions.a. Imagination and creativity are equally important in science.Science Focus: Easter Island Revisited—an example of how a once accepted hypothesis has been replaced as a result of new evidence.Scientific laws are widely accepted descriptions of phenomena we find happening repeatedly in nature.Science is repeatedly testedFrontier science is scientific results that have not been confirmed; reliable science is derived from scientific results that have been well tested and are widely accepted.Unreliable science has not undergone peer review, or has been discredited.Science has limitations.Scientists can disprove things, but not prove anything absolutely.Scientists are sometimes biased. Environmental phenomena often involve a multitude of interacting variables.Environmental scientists often rely on estimates based on statistical sampling and other mathematical methods.Science Focus: Statistics enable scientists to collect, organize and interpret numerical data. Probability, the chance that something will happen or be valid, is used to evaluate their results. Sample size can be very important to obtaining meaningful results.Science is limited to understanding the natural world and cannot be applied to morals or ethics.2-2 What is matter?A.Matter is anything that has mass and takes up space, living or not. It comes in chemical forms, as an element or a compound.1.An element is the distinctive building block that makes up every substance.2.Chemists classify elements by their chemical behavior by arranging them in a periodic table of elements.B.The building blocks of matter are atoms, ions, and molecules.1.An atom is the smallest unit of matter that exhibits the characteristics of an element.2.An ion is an electrically charged atom or combinations of atoms.3.A molecule is a combination of two or more atoms/ions of elements held together by chemical bonds.C.Each atom has a nucleus containing protons and neutrons. Electron(s) orbit the nucleus of an atom.1.A proton (p) is positively charged, a neutron (n) is uncharged, and the electron (e) is negatively charged.2.Each atom has an equal number of positively charged protons in the nucleus and negatively charged electrons outside the nucleus, so the atom has no net electrical charge.3.Each element has a specific atomic number that is equal to the number of protons in the nucleus.4.The mass number of an atom equals the total number of neutrons and protons in its nucleus.5.Isotopes are various forms of an element that have the same atomic number, but different mass number.D.Atoms of some elements can lose or gain one or more electrons to form ions with positive or negative electrical charges.1.Elements known as metals tend to lose one or more electrons; they are electron givers.2.Elements known as nonmetals tend to gain more electrons; they are known as electron receivers.3.Hydrogen ions (H+) in a solution are a measure of how acidic or basic the solution is. Neutral pH is 7, acid solutions are below 7, and basic solutions are above 7.E.Chemical formulas are a type of shorthand to show the type and number of atoms/ions in a compound.1.Ionic compounds are made up of oppositely charged ions, (Na+ and Cl-).pounds made of uncharged atoms are called covalent compounds (CH4).anic compounds contain carbon atoms combined with one another and with various other atoms. 1.Hydrocarbons: compounds of carbon and hydrogen atoms.2.Chlorinated hydrocarbons: compounds of carbon, hydrogen, and chlorine atoms.3.Simple carbohydrates: specific types of compounds of carbon, hydrogen, and oxygen atoms.G.Polymers are larger and more complex organic compounds that have molecular units.plex carbohydrates contain two or more monomers of simple sugars linked together.2.Proteins are formed by linking monomers of amino acids together.3.Nucleic acids are made of sequences of nucleotides linked together.4. Lipids are a fourth type of macromolecule. H. Cells are the fundamental structural and functional unit of life.Genes: specific sequences of nucleotides in a DNA molecule.Chromosomes: combinations of genes that make a single DNA molecule, plus some proteins.I.All compounds without the combination of carbon atoms and other elements’ atoms are inorganic compounds.J. According to the usefulness of matter as a resource, it is classified as having high or low quality.1.High-quality matter is concentrated with great potential for usefulness and is usually found near the earth’s surface.2.Low-quality matter is dilute and found deep underground and/or dispersed in air or water.2-3 What happens when matter undergoes change?A.When matter has a physical change, its chemical composition is not changed; the molecules are organized in different patterns.B.In a chemical change or reaction, the chemical composition of the elements/compounds change.1. Nuclear change occurs in three ways: radioactive decay, nuclear fission and nuclear fusion. C.The Law of Conservation of Matter states that no atoms are created/destroyed during a physical or chemical change. 2-4 What is energy and what happens when it undergoes change?A.Energy is the capacity to do work and transfer heat; it moves matter.1.Kinetic energy has mass and speed: wind, electricity are examples. Heat is also kinetic energy.2.Electromagnetic radiation is energy that travels as a wave, a result of changing electric and magnetic fields. Each form of electromagnetic radiation has a different wavelength and energy content. 3.Potential energy is stored energy.Potential energy can be changed into kinetic energy.99% of all energy on earth is solar; commercial energy in the marketplace makes up the remaining 1%, primarily derived from fossil fuels. C.Energy quality is measured by its usefulness; high energy is concentrated and has high usefulness. Low energy is dispersed and can do little work.D.The First Law of Thermodynamics states that energy can neither be created/destroyed, but can be converted from one form to another. E.The Second Law of Thermodynamics states that when energy is changed from one form to another, there is always less usable energy. Energy quality is depleted.1.In changing forms of energy, there is a loss in energy quality; heat is often produced and lost.2.Changing forms of energy produces a small percentage of useful energy; much is lost in the process.3.High-quality energy cannot be recycled/reused.What are systems and how do they respond to change?A system is a set of components that interact. Science Focus: The Usefulness of Models—models or simulations are used to learn how systems work, particularly when dealing with many variable, very long timeframes or situations where controlled experiments are not possible.1. Most systems have inputs from the environment, throughputs of matter and energy within the system, and outputs to the environment.Systems are affected by feedback and feedback loops (positive and negative).Systems often show time delays between input and response.Problems can build slowly in systems until reaching a tipping point.Synergy is when processes interact such that the combined effect is greater than the individual effects. Additional Video ResourcesAcid Rain The Invisible Threat (Video plus Lab)Hands-on lab activities plus video. The Habitable Planet: A Systems Approach to Environmental Science (Documentary series, 2007). The videos in this series all explore the use of science as a means of understanding the world. ResourcesThe Particle AdventureAn exploration of the fundamentals of matter from the Lawrence Berkeley Labs. Review QuestionsReview the Key Questions and Concepts for this chapter on p. 32. Describe the controlled scientific experiment carried out at the Hubbard Brook Experimental Forest. Scientists compared the loss of water and nutrients from an uncut forest ecosystem (the control site) with one that was stripped of its trees the experimental site) in the Hubbard Brook Experimental Forest in New Hampshire . First the investigators measured the amounts of water and dissolved plant nutrients that entered and left an undisturbed forested area (the control site). They found that an undisturbed mature forest is very efficient at storing water and retaining chemical nutrients in its soils. Then the scientists set up an experimental forested area; they cut down all trees and shrubs in one valley (the experimental site) and sprayed the area with herbicides to prevent regrowth. They compared the inflow and outflow of water and nutrients in this experimental site with those in the control site for 3 years. With no plants to help absorb and retain water, the amount of water flowing out of the deforested valley increased by 30– 40%. As this excess water ran rapidly over the ground, it eroded soil and carried dissolved nutrients out of the deforested site. Overall, the loss of key nutrients from the experimental forest was six to eight times that in the nearby control forest.What is science? Describe the steps involved in the scientific process. What is data? What is a model? Distinguish among a scientific hypothesis, scientific theory, and scientific law (law of nature). What is peer review and why is it important? Explain why scientific theories are not to be taken lightly and why people often use the term “theory” incorrectly. Describe how a hypothesis about the decline of a civilization on Easter Island has been challenged by new data.Science is an attempt to discover how nature works and to use that knowledge to make predictions about what is likely to happen in nature. There are a number of steps in the scientific method. A scientist will use the following procedure to study the natural world.Identify a problem. Find out what is known about the problem. A scientist will search the scientific literature to find out what was known about the area of interest. Ask a question to be investigated. Collect data to answer the question. To collect data— information needed to answer their questions— scientists make observations of the subject area they are studying. Scientific observations involve gathering information by using human senses of sight, smell, hearing, and touch and extending those senses by using tools such as rulers, microscopes, and satellites. Often scientists conduct experiments, or procedures carried out under controlled conditions to gather information and test ideas. Propose a hypothesis to explain the data. Scientists suggest a scientific hypothesis, a possible and test-able explanation of what they observe in nature or in the results of their experiments. Make testable predictions. Scientists use a hypothesis to make testable or logical predictions about what should happen if the hypothesis is valid. They often do this by making “ If . . . then” predictions. Test the predictions with further experiments, models, or observations. These predictions can be compared with the actual measured losses to test the validity of the models. Accept or reject the hypothesis. If their new data do not support their hypotheses, scientists come up with other testable explanations. This process continues until there is general agreement among scientists in the field being studied that a particular hypothesis is the best explanation of the data. Data is the information needed to answer scientific questions usually obtained by making observations and measurements. A model is an approximate representation or simulation of a system being studied.Scientific hypothesis is a possible and testable explanation of what is observed in nature or in the results of experiments. A well-tested and widely accepted scientific hypothesis or a group of related hypotheses is called a scientific theory. A scientific law, or law of nature is a well-tested and widely accepted description of what we find happening in nature. An important part of the scientific process is peer review, in which scientists openly publish details of the methods and models they used, the results of their experiments, and the reasoning behind their hypotheses for other scientists working in the same field (their peers) to evaluate. And any evidence gathered to verify a hypothesis must be reproducible. That is, scientists should repeat and analyze the work to see if the data can be reproduced and whether the proposed hypothesis is reasonable and useful. A scientific theory should be taken very seriously. It has been tested widely, supported by extensive evidence, and accepted by most scientists in a particular field or related fields of study. Nonscientists often use the word theory incorrectly when they actually mean scientific hypothesis, a tentative explanation that needs further evaluation. The statement, “Oh, that’s just a theory,” made in everyday conversation, implies that the theory was stated without proper investigation and careful testing—the opposite of the scientific meaning of the word. The gathering of new scientific data and the reevaluation of older data led to a revised hypothesis about the decline of civilization on Easter Island.Explain why scientific theories and laws are the most important and most certain results of science.Scientific theories and laws have a high probability of being valid, but they are not infallible. Occasionally, new discoveries and new ideas can overthrow a well- accepted scientific theory or law in what is called a paradigm shift. It occurs when the majority of scientists in a field or related fields accept a new paradigm, or framework for theories and laws in a particular field. Distinguish among tentative science (frontier science), reliable science, and unreliable science. What is statistics? What is probability and what is its role in scientific conclusions and proof? What are three limitations of science and environmental science?Tentative science or frontier science is the preliminary results that capture news headlines and may be controversial because they have not been widely tested and accepted by peer review yet. Reliable science consists of data, hypotheses, theories, and laws that are widely accepted by all or most of the scientists who are considered experts in the field under study, in what is referred to as a scientific consensus. The results of reliable science are based on the self-correcting process of testing, peer review, reproducibility, and debate. New evidence and better hypotheses may discredit or alter accepted views. Scientific hypotheses and results that are presented as reliable without having undergone the rigors of peer review, or that have been discarded as a result of peer review, are considered to be unreliable science. Statistics consists of mathematical tools used to collect, organize, and interpret numerical data.Probability is a mathematical statement about the likelihood that harm will be suffered from a hazard. Scientists often state probability in terms such as: “The lifetime probability of developing lung cancer from smoking one pack of cigarettes per day is 1 in 250.” Environmental science and science in general have three important limitations: Scientists cannot prove or disprove anything absolutely, because there is always some degree of uncertainty in scientific measurements, observations, and models.A limitation of science is that scientists are human and thus are not totally free of bias about their own results and hypotheses. A limitation—especially important to environmental science—is that many environmental phenomena involve a huge number of interacting variables and complex interactions. What is matter? Distinguish between an element and a compound and give an example of each. Distinguish among atoms, molecules, and ions and give an example of each. What is the atomic theory? Distinguish among protons, neutrons, and electrons. What is the nucleus of an atom? Distinguish between the atomic number and the mass number of an element. What is an isotope? What is acidity? What is pH?Matter is anything that has mass and takes up space. It can exist in three physical states—solid, liquid, and gas, and two chemical forms—elements and compounds. A chemical element is a fundamental substance that has a unique set of properties and cannot be broken down into simpler substances by chemical means. Compounds are a combination of two or more different elements held together in fixed proportions. The most basic building block of matter is an atom—the smallest unit of matter into which an element can be divided and still have its characteristic chemical properties, such as a single hydrogen atom. A second building block of some types of matter is an ion—an atom or group of atoms with one or more net positive (+) or negative (–) electrical charges, such as H+. A molecule is a combination of two or more atoms of the same elements held together by forces called chemical bonds, such as O2, oxygen.The atomic theory is the idea that all elements are made up of atoms.Three different types of subatomic particles: positively charged protons (p), neutrons (n) with no electrical charge, and negatively charged electrons (e). Each atom consists of an extremely small and dense center called its nucleus—which contains one or more protons and, in most cases, one or more neutrons— and one or more electrons moving rapidly somewhere around the nucleus.Each atom has equal numbers of positively charged protons and negatively charged electrons. Because these electrical charges cancel one another, atoms as a whole have no net electrical charge. Each element has a unique atomic number, equal to the number of protons in the nucleus of its atom. The mass of an atom is described by its mass number: the total number of neutrons and protons in its nucleus. Forms of an element having the same atomic number but different mass numbers are called isotopes of that element.Ions are also important for measuring a substance’s acidity in a water solution, a chemical characteristic that helps determine how a substance dissolved in water will interact with and affect its environment. Scientists use pH as a measure of acidity, based on the amount of hydrogen ions (H+) and hydroxide ions (OH–) contained in a particular volume of a solution.What is a chemical formula? Distinguish between organic compounds and inorganic compounds and give an example of each. Distinguish among complex carbohydrates, proteins, nucleic acids, and lipids. What is a cell? Distinguish among a gene, a trait, and a chromosome. What is matter quality? Distinguish between high- quality matter and low- quality matter and give an example of each.Chemists use a chemical formula to show the number of each type of atom or ion in a anic compounds contain at least two carbon atoms combined with atoms of one or more other element, such as table sugar and methane. All other compounds, except methane (CH4), are called inorganic compounds, such plex carbohydrates, such as cellulose and starch, consist of two or more monomers of simple sugars, such as glucose. Proteins are formed by monomers called amino acids. Nucleic acids (DNA and RNA) are formed by monomers called nucleotides. Lipids, which include fats and waxes, are not all made of monomers, but are a fourth type of macromolecule essential for life. Cells are the smallest and most fundamental structural and functional units of life.Within some DNA molecules are certain sequences of nucleotides called genes. Each of these distinct pieces of DNA contains instructions, called genetic information, for making specific proteins. Each of these coded units of genetic information concerns a specific trait, or characteristic, passed on from parents to offspring during reproduction in most animals or plants. Thousands of genes, in turn, make up a single chromosome, a special DNA molecule together with a number of proteins. Matter is anything that has mass and takes up space. It can exist in three physical states: solid, liquid, and gas and two chemical forms: elements and compounds.High-quality matter is highly concentrated, is typically found near the earth’s surface, and has great potential for use as a resource, coal for example. Low-quality matter is not highly concentrated, is often located deep underground or dispersed in the ocean or atmosphere, and usually has little potential for use as a resource, a salt solution for example.Distinguish between a physical change and a chemical change (chemical reaction) and give an example of each. What is a nuclear change? Explain the differences among natural radioactive decay, nuclear fission, and nuclear fusion. What is the law of conservation of matter and why is it important?When a sample of matter undergoes a physical change, there is no change in its chemical composition. A piece of aluminum foil cut into small pieces is still aluminum foil. When a chemical change, or chemical reaction, takes place there is a change in chemical composition of the substances involved. Chemists use a chemical equation to show what happens in a chemical reaction. For example, when coal burns completely, the solid carbon (C) in the coal combines with oxygen gas (O2) from the atmosphere to form the gaseous compound carbon dioxide (CO2). Nuclear change is the process in which nuclei of certain isotopes spontaneously change, or are forced to change, into one or more different isotopes. Nuclear fission occurs when the nuclei of certain isotopes with large mass numbers (such as uranium-235) are split apart into lighter nuclei when struck by a neutron and release energy plus two or three more neutrons.Nuclear fusion occurs when two isotopes of light elements, such as hydrogen, are forced together at extremely high temperatures until they fuse to form a heavier nucleus and release a tremendous amount of energy. The law of conservation of matter states whenever matter undergoes a physical or chemical change, no atoms are created or destroyed. This law helps us understand that we need to let our waste cycle back to its original nutrients/products in order for our resources to be sustainable.What is energy? Distinguish between kinetic energy and potential energy and give an example of each. What is heat? Define and give two examples of electromagnetic radiation. What are fossil fuels and what three fossil fuels do we use most to supplement energy from the sun? What is energy quality? Distinguish between high- quality energy and low- quality energy and give an example of each. What is the first law of thermodynamics (law of conservation of energy) and why is it important? What is the second law of thermodynamics and why is it important? Explain why the second law means that we can never recycle or reuse high- quality energy.Energy is the capacity to do work or transfer heat. There are two major types of energy: moving energy (called kinetic energy) and stored energy (called potential energy). Examples of kinetic energy include wind (a moving mass of air), flowing water, and electricity (flowing electrons). An example of potential energy is gasoline. Heat is a form of kinetic energy, the total kinetic energy of all moving atoms, ions, or molecules within a given substance. When two objects at different temperatures contact one another, heat flows from the warmer object to the cooler object. Electromagnetic radiation is energy that travels in the form of a wave as a result of changes in electrical and magnetic fields. Forms of electromagnetic radiation are short wavelengths such as gamma rays and X rays. fossil fuels are ancient deposits of organic matter formed over millions of years as layers of the decaying remains of ancient plants and animals were exposed to intense heat and pressure within the earth’s crust. The three most widely used fossil fuels are oil, coal, and natural gas.Energy quality is a measure of an energy source’s capacity to do useful work. High-quality energy is concentrated and has a high capacity to do useful work. Examples are very high-temperature heat, nuclear fission, concentrated sunlight, high-velocity wind, and energy released by burning natural gas, gasoline, or coal. Low-quality energy is dispersed and has little capacity to do useful work. An example is heat dispersed in the moving molecules of a large amount of matter (such as the atmosphere or an ocean) so that its temperature is low. The first law of thermodynamics, also known as the law of conservation of energy, states that whenever energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed. This scientific law tells us that no matter how hard we try or how clever we are, we cannot get more energy out of a physical or chemical change than we put in because energy input always equals energy output. The second law of thermodynamics states that when energy is changed from one form to another, it always goes from a more useful to a less useful form. We can never recycle or reuse high-quality energy because whenever energy is converted from one form to another, we always end up with a lower quality or less “usable” energy than we started with.Define and give an example of a system. Distinguish among the input, flow (throughput), and output of a system. Why are scientific models useful? What is feed-back? What is a feedback loop? Distinguish between a positive feedback loop and a negative (corrective) feedback loop in a system, and give an example of each. Distinguish between a time delay and a synergistic interaction (synergy) in a system and give an example of each. What is a tipping point?A system is a set of components that function and interact in some regular way. The human body, a river, an economy, and the earth are all systemsMost systems have the following key components: inputs from the environment, flows or throughputs of matter and energy within the system at certain rates, and outputs to the environment. Scientists use models, or simulations, to learn how systems work. Some of our most powerful and useful technologies are mathematical and computer models.Most systems are affected by feedback, any process that increases or decreases a change to a system. Such a process, called a feed-back loop, occurs when an output of matter, energy, or information is fed back into the system as an input and leads to changes in that system. A positive feedback loop causes a system to change further in the same direction. For example, in the Hubbard Brook experiments, researchers found that when vegetation was removed from a stream valley, flowing water from precipitation caused erosion and loss of nutrients, which caused more vegetation to die. With even less vegetation to hold soil in place, flowing water caused even more erosion and nutrient loss, which caused even more plants to die. Such accelerating positive feedback loops are of great concern in several areas of environmental science. One of the most alarming is the melting of polar ice, which has occurred as the temperature of the atmosphere has risen during the past few decades. As that ice melts, there is less of it to reflect sunlight, and more water is exposed to sunlight. Because water is darker, it absorbs more solar energy, making the area warmer and causing the ice to melt faster, thus exposing more water. The melting of polar ice thus accelerates.A negative, or corrective, feedback loop causes a system to change in the opposite direction from which is it moving. A simple example is a thermostat, a device that controls how often, and how long a heating or cooling system runs. When the furnace in a house is turned on and begins heating the house, the thermostat can be set to turn the furnace off when the temperature in the house reaches the set number. The house then stops getting warmer and starts to plex systems often show time delays between the input of a feedback stimulus and the response to it. For example, scientists could plant trees in a degraded area such as the Hubbard Brook experimental forest to slow erosion and nutrient losses, but it would take years for the trees and other vegetation to grow enough to accomplish this purpose.A synergistic interaction, or synergy, occurs when two or more processes interact so that the combined effect is greater than the sum of their separate effects.Scientific studies reveal such an interaction between smoking and inhaling asbestos particles. For example, lifetime smokers have ten times the risk that nonsmokers have of getting lung cancer. And individuals exposed to asbestos particles for long periods increase their risk of get-ting lung cancer fivefold. But people who smoke and are exposed to asbestos have 50 times the risk that non-smokers have of getting lung cancer.Time delays can also allow an environmental problem to build slowly until it reaches a threshold level, or tipping point, causing a fundamental shift in the behavior of a system.What are this chapter’s three big ideas? Relate the three principles of sustainability to the Hubbard Brook Experimental Forest controlled experiment.The three big ideas are that we cannot do away with matter, we cannot get more energy out than we put in, and whenever energy is converted from one form to another in a physical or chemical change, we always end up with lower-quality or less usable energy than we started with.The controlled experiment discussed in the Core Case Study that opened this chapter revealed that clearing a mature forest degrades some of its natural capital. The loss of trees and vegetation altered the ability of the forest to retain and recycle water and other critical plant nutrients— a crucial ecological function. The loss of vegetation also violated the other three scientific principles of sustainability. For example, the cleared forest had fewer plants that could use solar energy to produce food for animals. And the loss of plants and animals reduced the life-sustaining biodiversity of the cleared forest. This in turn reduced some of the interactions between different types of plants and animals that help control their populations. Critical ThinkingThe following are examples of the material that should be contained in possible student answers to the end of chapter Critical Thinking questions. They represent only a summary overview and serve to highlight the core concepts that are addressed in the text. It should be anticipated that the students will provide more in-depth and detailed responses to the questions depending on an individual instructor’s stated expectations.What ecological lesson can we learn from the controlled experiment on the clearing of forest described in the Core Case Study that opened this chapter?Vegetation controls water and nutrient loss from ecosystems. Loss of vegetation diminishes the systems’ ability to retain nutrients and water.You observe that all of the fish in a pond have disappeared. Describe how you might use the scientific process described in the Core Case Study and on p. 32 to determine the cause of this fish kill.The answer should begin with some observation that can lead to a hypothesis. An observation could be something like increased runoff, increased pollutants, decrease in vegetation or biodiversity, etc. Describe a way in which you have applied the scientific process described in the chapter (Figure 2-2) in your own life, and state the conclusion you drew from the process. Describe a new problem that you would like to solve using this process.One morning as you prepare to depart for your college, you find that your car will not start. You observe that there is no sound of the engine turning over. You hypothesize that you have a dead battery. You then devise an experiment to test this hypothesis. You reason that you can charge the battery or jumpstart the car to test whether or not the battery is truly the cause. Upon charging, your car will start, so you conclude that your battery must have died. Other problems the students could solve could range from issues that affect them directly to those affecting the community or the world. Respond to the following statements: a. Scientists have not absolutely proven that anyone has ever died from smoking cigarettes. b. The greenhouse theory—that certain gases (such as water vapor and carbon dioxide) warm the atmosphere—is not a reliable idea because it is just a scientific theory. (a) The medical and scientific evidence that links smoking to premature death caused by a number of pathological conditions is overwhelming. As we are exposed to many chemical hazards in our environment it is often difficult to specifically link the cause and effect. The chances of an individual dieing from smoking one cigarette is statistically negligible and highly unlikely, but many years of heavy smoking has a much higher probability that death could result from a disease brought on as a result of smoking.(b) Sometimes people with a limited knowledge of the scientific method often confuse a theory with a hypothesis. A theory has been widely tested and is endorsed by a wide group of scientists working in that particular field of study. Many scientists concur with the scientific evidence, obtained through conducting controlled experiments, that water and carbon dioxide are greenhouse gases.A tree grows and increases its mass. Explain why this phenomenon is not a violation of the law of conservation of matter.The growth of a tree is an example of a chemical change or chemical reaction. Small inorganic elements and compounds are combined to form more complex molecules that make up the material found in the tree. The components that were present in the soil and air have been rearranged to form other types of chemical components. The amount of material that was present before this rearrangement or chemical change took place is the same as the amount afterwards. A student may discuss photosynthesis to support and explain their answer.If there is no “away” where organisms can get rid of their wastes because of the law of conservation of matter, why is the world not filled with waste matter?Just like when small molecules are combined to form larger compounds, as in the case of the growth of a tree, when larger compounds are broken down they release smaller molecules back into the environment. An example is that of a rotting log. A tree limb may break off and fall to the forest floor. Over a period of time it is decomposed by a variety of organisms and the materials contained in the log return once again into the environment. In this way nature recycles all matter that exists in the environment. The student may discuss cell respiration to support or explain their answer.Someone wants you to invest money in an automobile engine that will produce more energy than the energy in the fuel (such as gasoline or electricity) used to run the motor. What is your response? Explain.That is not a good investment! The first law of thermodynamics states that energy can be changed from one form to another (such as chemical energy into mechanical energy), but energy cannot be created or destroyed. An engine that produces more energy than it consumes is simply not a feasible scientifically sound prospect.Use the second law of thermodynamics to explain why a barrel of oil can be used only once as a fuel, or in other words, why we cannot recycle this high quality energy.The second law of thermodynamics states that when energy changes from one form to another, some of the useful energy is always degraded to lower-quality, more dispersed, less useful energy. When a barrel of oil that contains high-quality chemical energy is used as a fuel in order to do useful work, it is transformed or changed into low-quality energy such as heat, which has little ability to do useful work. Therefore the barrel of oil can only be used once as a fuel.9.a. Imagine you have the power to revoke the law of conservation of matter for one day. What are the three most important things you would do with this power? Explain your choices b. Imagine you have the power to violate the first law of thermodynamics for one day. What are the three most important things you would do with this power? Explain your choices.(a) Student answers will vary but could include: make more oil to offset the world shortage; produce more water to supply areas that desperately need it; transform all chemical pollutants into useful materials that are not harmful.(b) Student answers will vary but could include: grow more crops to provide food; produce electricity that can be stored in batteries for later use; physically change more of the water in the Arctic Ocean into sea ice to offset the losses that have occurred in the past few decades.10.List two questions that you would like to have answered as a result of reading this chapter.Student answers will vary but could include:What other examples are there, apart from Easter Island, that show how civilizations have fallen as a result of degrading their resource base?How close are scientists to being able to mimic photosynthesis and use sunlight to split water into hydrogen and oxygen, similar to the process of electrolysis of water, and provide the world with hydrogen as a major energy source?Data AnalysisConsider the graph below that shows loss of calcium from the experimental cutover site of the Hubbard Brook Experimental Forest compared with that of the control site. Note that this is very similar to Figure 2-6, which compares loss of nitrates from the two sites. After studying this graph, answer the questions below.In what year did the calcium loss from the experimental site begin a sharp increase? In what year did it peak? In what year did it again level off?1965-19661967-19681971-1972In what year were the calcium losses from the two sites closest together? In the span of time between 1963 and 1972, did they ever get that close again?1964-1965No.Does this graph support the hypothesis that cutting the trees from a forested area causes the area to lose nutrients more quickly than leaving the trees in place? Explain.Yes, this data supports the hypothesis that the cutover area had an increase in nutrient loss from the site. The data shows that nutrient loss then began to decline over time as the vegetation began growing again. Chapter 3Ecosystems: What Are They and How Do They WorkSummary1.Ecology is the study of connections in nature.2.Life on earth is sustained by the one-way flow of high-quality energy from the sun, by the cycling of matter, and by gravity.3.Matter, energy, and life are the major components of an ecosystem.4.Energy in an ecosystem decreases in amount to each succeeding organism in a food chair or web.5.Soil is a complex mixture of eroded rock, mineral nutrients, water, air, decaying organic matter, and billions of living organisms. It covers most of the earth and provides nutrients for plant growth. Soils are formed by a breaking down of rock, decomposing surface litter and organic matter. Bacteria and other decomposer microorganisms break down some of soil’s organic compounds into simpler inorganic compounds.6.Matter is recycled through the earth’s ecosystem of air, land, water, and living organisms. This vast global recycling system is composed of nutrient cycles.7.Scientists study ecosystems through the use of aquarium tanks, greenhouses, and controlled indoor and outdoor chambers. Specific variables are carefully controlled, like temperature, light, carbon dioxide, and humidity.8.Two principles of sustainability found from learning how nature works are the law of conservation of matter and the two laws of thermodynamics.Outline3-1 What keeps us and other organisms alive?CORE CASE STUDY. Tropical rainforests make up only 2% of the earth’s land surface, but account for more than half of all biodiversity. Already more than half of this area has been destroyed, and degradation is increasing. This will cause a reduction in biodiversity, an increase in climate change, and changes in regional weather patterns. A. Earth’s life support system consists of four main systems: atmosphere (air), hydrosphere (water), geosphere (earth) and the biosphere (living things).1. Atmosphere contains many layers:The troposphere extends 17 km up and contains the air we breathe. About 1% is composed of greenhouse gases (water vapor, methane and carbon dioxide), which absorb energy to warm the lower atmosphere. The stratosphere lies 17–50 km above the troposphere and filters the sun’s harmful radiation.The hydrosphere consists of earth’s water, found in liquid water, ice, and water vapor.The geosphere consists of the earth’s core, mantle, and crust.The biosphere is where life is found. B. Life on earth depends on three interconnected factors1. The one-way flow of high-quality solar energy. 2.The cycling of nutrients.3.Gravity. C. Solar energy reaches earth as electromagnetic waves in the form of visible light, UV radiation and heat. D.As solar radiation interacts with the earth, infrared radiation is produced. Greenhouse gases trap the heat and warm the troposphere. This natural greenhouse effect makes the planet warm enough to support life. 1. Human activities add greenhouse gasses to the atmosphere, intensifying the greenhouse effect. 3-2 What are the major components of an ecosystem?A.Ecology is the study of connections in the natural world. 1.There are five levels of study: organisms, populations, communities, ecosystems and the biosphere. 2. Ecosystems are comprised of living (biotic) and non-living (abiotic) components.3. Every organism occupies a trophic (feeding) level.Producers, or autotrophs, make their own food from compounds in the environment. Photosynthesis is the process by which plants take solar energy, carbon dioxide and water to form energy rich sugars. Chemosynthesis is the process by which some organisms can use geothermal energy to produce complex nutrient compounds. 4. Consumers, or heterotrophs, feed on other organisms.Herbivores (primary consumers) feed on plants.Carnivores feed on animals.Secondary consumer feed on herbivoresTertiary consumers feed on other carnivores. Omnivores feed on both plants and animals.Decomposers break down organic detritus (bacteria/fungi) into simpler inorganic compounds.Detritivores feed on dead organic matter and break it down into smaller molecules. 5. Glucose and other organic compounds are broken down and energy is released by the process of aerobic respiration, the use of oxygen to convert organic matter back to carbon dioxide and water. 6. Some decomposers are able to break down organic compounds without using oxygen. This process is called anaerobic respiration, or fermentation.Science Focus: Microbes are pivotally important in terms of cycling matter, providing oxygen and regulating the earth’s temperature by removing carbon dioxide.3-3 What happens to energy in an ecosystem?A.Food chains and food webs help us understand how eaters, the eaten, and the decomposed are interconnected in an ecosystem.B.Energy flow in a food web/chain decreases at each succeeding organism in a chain or web.C.The dry weight of all organic matter within the organisms of a food chain/web is called biomass. D.The greater number of trophic levels in a food chain, the greater loss of usable energy.F.The pyramid of energy flow visualizes the loss of usable energy through a food chain. The lower levels of the trophic pyramid support more organisms. G.Production of biomass takes place at different rates among different ecosystems.1.The rate of an ecosystem’s biomass production is the gross primary productivity (GPP).2.Some of the biomass must be used for the producers’ own respiration. Net primary productivity (NPP) measures how fast producers can provide biomass needed by consumers in an ecosystem.3.Ecosystems and life zones differ in their NPP. H.The planet’s NPP limits the numbers of consumers who can survive on earth.3-4 What happens to matter in an ecosystem?A.Nutrient cycles/biogeochemical cycles are global recycling systems that interconnect all organisms.1.These cycles include the carbon, oxygen, nitrogen, phosphorus, and water cycles. B.The water/hydrologic cycle collects, purifies, and distributes the earth’s water in a vast global cycle.1.Solar energy evaporates water, and the water returns as rain/snow.2.Some water becomes surface runoff, returning to streams/rivers.3.Water is the major form of transporting nutrients within and between ecosystems.4. Many natural process purify waterC.The water cycle is altered by man’s activities.1.We withdraw large quantities of fresh water.2.We clear vegetation and increase runoff, reduce filtering and increase flooding.3.We increase flooding as we drain and alter wetlands. D.The carbon cycle circulates through the biosphere. 1.CO2 gas is an important temperature regulator on earth.2.Photosynthesis and aerobic respiration circulates carbon in the biosphere.3.Fossil fuels contain carbon. 4. Excess carbon dioxide in the atmosphere has contributed to global warming. E.Nitrogen is recycled through the earth’s systems by different types of bacteria.1.The nitrogen cycle converts nitrogen (N2) into compounds that are useful nutrients for plants and animals.2.The nitrogen cycle includes these steps:a.Specialized bacteria convert gaseous nitrogen to ammonia in nitrogen fixation.b.Special bacteria convert ammonia in the soil to nitrite ions and nitrate ions; the latter is used by plants as a nutrient. This process is nitrification.c.Decomposer bacteria convert detritus into ammonia and water-soluble salts in ammonification.d.In denitrification, nitrogen leaves the soil. Anaerobic bacteria in soggy soil and bottom sediments of water areas convert NH3 and NH4+ back into nitrite and nitrate ions, and then nitrogen gas and nitrous oxide gas are released into the atmosphere.3.Human activities affect the nitrogen cycle.a.In burning fuel, we add nitric oxide into the atmosphere; it can be converted to NO2 gas and nitric acid, and it can return to the earth’s surface as acid rain.b.Nitrous oxide that comes from livestock, wastes, and inorganic fertilizers we use on the soil can warm the atmosphere and deplete the ozone layer.c.We destroy forest, grasslands, and wetland and, thus, release large amounts of nitrogen into the atmosphere.d.We pollute aquatic ecosystems with agricultural runoff and human sewage.e.We remove nitrogen from topsoil with our harvesting, irrigating, and land-clearing practices.F.The phosphorus cycle does not include the atmosphere. The major reservoir is terrestrial rock formations. 1. Most soils contain little phosphate, and it is often the limiting factor for plant growth.2.Phosphorus is used as a fertilizer to encourage plant growth.3.Phosphorus also limits growth of producers in freshwater streams and lakes due to low solubility in water.G.Humans interfere with the phosphorous cycle in harmful ways.1.We mine phosphate rock to produce fertilizers and detergents.2.We cut down tropical forests and, thereby, reduce the phosphorus in tropical soils.3.Eroding topsoil moves large quantities of topsoil to aquatic systems, where it stimulates growth in algae. H.Sulfur cycles through the biosphere and much of it is stored underground in rocks and minerals.1.Natural sources of sulfur are hydrogen sulfide, released from volcanoes, swamps, bogs, and tidal flats where anaerobic decomposition occurs.2. Particles of sulfate, such as ammonium sulfate, enter the atmosphere from sea spray, dust storms and forest fires. 2.Some marine algae produce dimethyl sulfide (DMS). DMS acts as nuclei for condensation of water found in clouds. This can affect the cloud cover and climate.3.Sulfur compounds can be converted to sulfuric acid, which falls as acid deposition.4.Burning coal and oil, refining oil, and the production of some metals from ores all add sulfur to the environment.3-5 How do scientists study ecosystems?A.Ecologists do field research, observing and measuring the ecosystem structure and function.B.New technologies such as remote sensing and geographic information systems (GISs) gather data that is fed into computers for analysis and manipulation of data.C.Ecologists use tanks, greenhouses, and controlled indoor and outdoor chambers to study ecosystems (laboratory research). This allows control of light, temperature, CO2, humidity, and other variables.D.Field and laboratory studies must be coupled together for a more complete picture of an ecosystem.E.Systems analysis develops mathematical and other models that simulate ecosystems that are large and very complex and can’t be adequately studied with field and laboratory research. This allows the analysis of the effectiveness of various alternate solutions to environmental problems and can help anticipate environmental surprises.Science Focus: The use of satellites as remote sensing devises and tools such as Google Earth provide for a powerful new approach to understanding the environment and conducting research. Additional Video ResourcesBlue Planet (Video series from Discovery Channel, 2001)Mammoth series, five years in the making, taking a look at the rich tapestry of life in the world's oceans. Habitable Planet: A Systems Approach to Environmental Science, videos 2, 3, 4, 9, and 12 (Documentary series, 2007). The videos in this series focus on atmosphere, oceans, ecosystems, biodiversity decline and earth’s changing climate. to Planet Earth (Video series from PBS, 2003) Living Planet — A Portrait of the Earth (hosted by David Attenborough – four discs) This series discusses the biomass and life in a variety of ecosystems spanning many of the environments found on Earth.Planet Earth (BBC Series, 5 discs)An exploration of global ecosystems. Web ResourcesThe Hydrologic CycleInteractive exploration of various phases of the water cycle. QuestionsReview the Key Questions and Concepts for this chapter on p. 55. What are three harmful effects resulting from the clearing and degradation of tropical rain forests? It will reduce the earth’s vital biodiversity by destroying or degrading the habitats of many of the unique plant and animal species found in these forests, thereby causing their premature extinction.It will help to accelerate global warming, and thus climate change, by eliminating large areas of trees faster than they can grow back, thereby degrading the forests’ abilities to remove the greenhouse gas carbon dioxide (CO2) from the atmosphere. It will change regional weather patterns in ways that can prevent the return of diverse tropical rain forests in cleared or degraded areas. Once this irreversible ecological tipping point is reached, tropical rain forests in such areas will become less diverse tropical grasslands. Distinguish among the atmosphere, troposphere, stratosphere, stratosphere, hydrosphere, geosphere, and biosphere. What are greenhouse gases and why are they important? What three interconnected factors sustain life on earth?The atmosphere is a thin spherical envelope of gases surrounding the earth’s surface. Its inner layer, the troposphere, extends only about 17 kilometers (11 miles) above sea level at the tropics and about 7 kilometers (4 miles) above the earth’s north and south poles. It contains the majority of the air that we breathe, consisting mostly of nitrogen (78% of the total volume) and oxygen (21%). The remaining 1% of the air includes water vapor, carbon dioxide, and methane, all of which are called greenhouse gases, which absorb and release energy that warms the lower atmosphere. Without these gases the earth would be too cold for the existence of life as we know it. Almost all of the earth’s weather occurs within this layer. The next layer, stretching 17–50 kilometers (11–31 miles) above the earth’s surface, is called the stratosphere. Its lower portion holds enough ozone (O3) gas to filter out most of the sun’s harmful ultraviolet (UV) radiation. This global sunscreen allows life to exist on land and in the surface layers of bodies of water. The hydrosphere consists of all of the water on or near the earth’s surface. It is found as liquid water (on the surface and underground), ice (polar ice, icebergs, and ice in frozen soil layers called permafrost), and water vapor in the atmosphere. The oceans, which cover about 71% of the globe, contain about 97% of the earth’s water. The geosphere consists of the earth’s intensely hot core, a thick mantle composed mostly of rock, and a thin outer crust. The biosphere consists of all of the parts of the atmosphere, hydrosphere, and geosphere where life is found.Greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. They are responsible for warming the earth and making it inhabitable. Three factors sustain the earth’s life. The one-way flow of high-quality energy from the sun, through living things in their feeding interactions, into the environment as low-quality energy (mostly heat dispersed into air or water at a low temperature), and eventually back into space as heat. The cycling of nutrients (the atoms, ions, or molecules needed for survival by living organisms) through parts of the biosphere. Gravity allows the planet to hold onto its atmosphere and helps to enable the movement and cycling of chemicals through the air, water, soil, and organisms. Describe the flow of energy to and from the earth. What is the natural greenhouse effect and why is it important for life on earth? Define ecology. Define organism, population, and community. Define and distinguish between an ecosystem and the biosphere.About one-third of the incoming solar radiation is reflected back into space by clouds, particles in the atmosphere, and the earth’s surface. Another fifth of the incoming radiation is absorbed by ozone in the lower stratosphere (mostly UV radiation) and clouds and water vapor in the troposphere. Most of the remaining half of incoming solar radiation is absorbed by land and water on the earth’s surface. Carbon dioxide and other gases in the troposphere lead to a warming of the troposphere known as the natural greenhouse effect.Ecology is the biological science that studies how organisms, or living things, interact with one another and with their environment. An organism is an individual living being. A population is a group of individuals of the same species that live in the same place at the same time. A community, or biological community, consists of all the populations of different species that live in a particular place.An ecosystem is a community of different species interacting with one another and with their nonliving environment of matter and energy and the biosphere is the part of the earth's air, water, and soil where life is found.Distinguish between the living and nonliving components in ecosystems and give two examples of each.Biotic: consists of living biological components—plants, animals, and microbes.Abiotic: consists of nonliving components such as water, air, nutrients, rocks, heat, and solar energy. What is a trophic level? Distinguish among producers (autotrophs), consumers (heterotrophs), and decomposers and detritus feeders and give an example of each in an ecosystem. Distinguish among primary consumers (herbivores), secondary consumers (carnivores), tertiary (third-level) consumers, and omnivores, and give an example of each.The trophic level, a feeding level, is the level assigned every type of organism in an ecosystem, depending on its source of food or nutrients. Producers, sometimes called autotrophs (self-feeders), make the nutrients they need from compounds and energy obtained from their environment through a process called photosynthesis, a tree for example.All organisms that are not producers are consumers, or heterotrophs (“other-feeders”), who cannot produce their own nutrients, a fox for example. Decomposers are consumers that release nutrients from the dead bodies of plants and animals and return them to the soil, water, and air for reuse by producers, mushrooms for example. Detritus feeders feed on the wastes or dead bodies of other organisms. Examples are earthworms, some insects, and vultures.Primary consumers, or herbivores (plant eaters), are animals that eat producers, feeding mostly on green plants. Examples are caterpillars, deer, and zooplankton. Carnivores (meat eaters) are animals that feed on the flesh of other animals. Some carnivores such as spiders, robins, and tuna are secondary consumers that feed on the flesh of herbivores. Other carnivores such as tigers, hawks, and killer whales (orcas) are tertiary (or higher) consumers that feed on the flesh of other carnivores. Omnivores such as pigs, foxes, and humans can eat plants and other animals. Distinguish between photosynthesis and chemosynthesis. Distinguish between aerobic respiration and anaerobic respiration (fermentation). What two processes sustain ecosystems and the biosphere and how are they linked? Explain the importance of microbes.Producers use photosynthesis to convert CO2 into complex carbohydrates such as glucose (C6H12O6). Producers, consumers, and decomposers use the chemical energy stored in glucose and other organic compounds to fuel their life processes. In most cells, this energy is released by aerobic respiration, which uses oxygen to convert glucose (or other organic nutrient molecules) back into carbon dioxide and water. The net effect of the hundreds of steps in this complex process is represented by the following reaction: glucose +oxygen → carbon dioxide+water + energy. This linkage between photosynthesis in producers and aerobic respiration in producers, consumers, and decomposers circulates carbon in the biosphere. Oxygen and hydrogen—the other elements in carbohydrates—cycle almost in step with carbon. A few producers, mostly specialized bacteria, can convert simple inorganic compounds from their environment into more complex nutrient compounds with-out using sunlight, through a process called chemosynthesis.Some decomposers get the energy they need by breaking down glucose (or other organic compounds) in the absence of oxygen. This is called anaerobic respiration, or fermentation. The end products of this process are compounds such as methane gas ( CH4, the main component of natural gas), ethyl alcohol (C2H6O), acetic acid ( C2H4O2, the key component of vinegar), and hydrogen sulfide ( H2S, when sulfur compounds are broken down).Ecosystems and the biosphere are sustained through a combination of one- way energy flow from the sun through these systems and nutrient cycling of key materials within them— two important natural services that are components of the earth’s natural capital. Microbes that decompose dead and decaying plant and animal materials are vital to all ecosystems. Their importance is often ignored, but without them life would not exist. They consist of many different types of bacteria and fungi that secrete enzymes that break down materials from other organisms into smaller components; this enables nutrients to be recycled through the ecosystem as they are taken up from the soil and water by the producers.Distinguish between a food chain and a food web. Explain what happens to energy as it flows through the food chains and food webs. What is biomass? What is the pyramid of energy flow? Why are there more insects than tigers in the world?A sequence of organisms, each of which serves as a source of food or energy for the next, is called a food chain. Organisms in most ecosystems form a complex network of interconnected food chains called a food web. Each trophic level in a food chain or web contains a certain amount of biomass. In a food chain or web, chemical energy stored in biomass is transferred from one trophic level to another. With each transfer, some energy is lost as low-quality heat. As energy flows through ecosystems in food chains and webs, there is a decrease in the amount of chemical energy available to organisms at each succeeding feeding level.Biomass is the dry weight of all organic matter contained in its organisms.The pyramid of energy flow assumes a 90% energy loss with each transfer in a food chain. There is such a sharp reduction of energy as we move up trophic levels that there is simply not enough energy at the top to support large populations of top predators such as tigers. At the bottom level, however, there is plenty of energy to support large populations of insects. Distinguish between gross primary productivity (GPP) and net primary productivity (NPP), and explain their importance.Gross primary productivity (GPP) is the rate at which an ecosystem’s producers (usually plants) convert solar energy into chemical energy in the form of biomass found in their tissues. Net primary productivity (NPP) is the rate at which producers use photosynthesis to produce and store chemical energy minus the rate at which they use some of this stored chemical energy through aerobic respiration. The amount, or mass, of living organic material (biomass) that a particular ecosystem can support is determined by how much solar energy its producers can capture and store as chemical energy and by how rapidly they can do so.What happens to matter in an ecosystem? What is a biogeochemical cycle (nutrient cycle)? Describe the hydrologic, or water cycle. Summarize the unique properties of water. Explain how clearing a rainforest can affect local weather (Core Case study). Explain how human activities are affecting the water cycle. Describe the carbon, nitrogen, phosphorus, and sulfur cycles and explain how human activities are affecting each cycle. Explain how nutrient cycles connect past, present, and future life. Matter, in the form of nutrients, cycles within and among ecosystems and the biosphere, and human activities are altering these chemical cycles.The elements and compounds that make up nutrients move continually through air, water, soil, rock, and living organisms within ecosystems in cycles called biogeochemical cycles (literally, life-Earth-chemical cycles), or nutrient cycles. The hydrological cycle, or water cycle, collects, purifies, and distributes this supply of water.Water is necessary for life on the earth, and there is a fixed supply of it on our planet. Hydrogen bonds.Exists as a liquid over a wide temperate range.Stores a large amount of heat.Dissolves a variety of compounds.Filter’s some UV rays from the sun. Capillary action.Expands when freezes.Exists in all three phases at the Earth’s surfaceThe vegetation in forests is the primary source of local rainfall. Over land, about 90% of the water that reaches the atmosphere evaporates from the surfaces of plants, through a process called transpiration, and from the soil. We alter the hydrologic cycle by extracting water from streams, clearing vegetation and altering wetlands. Carbon is the basic building block of the carbohydrates, fats, proteins, DNA, and other organic compounds necessary for life. In the carbon cycle, carbon circulates through the biosphere, the atmosphere, and parts of the hydrosphere. We alter this cycle by adding large amounts of carbon to the atmosphere. Nitrogen is a crucial component of proteins, many vitamins, and nucleic acids such as DNA. We alter this cycle by burning fossil fuels, clearing forests, and fertilizing our crops. Phosphorus circulates through water, the earth’s crust, and living organisms in the phosphorus cycle. We alter this cycle by removing phosphate from the environment to make fertilizers.Sulfur circulates through the biosphere in the sulfur cycle. We alter this cycle primarily by burning fossil fuels The law of conservation of matter tells us that these nutrients cannot be destroyed, and so must be recycled. They are constantly cycled through living systems. Describe three ways in which scientists study ecosystems. Describe how satellite and Google Earth technology can be used to help us understand and monitor the natural world and how we are affecting it. Explain why we need much more basic data about the structure and condition of the world’s ecosystems. What are this chapter’s three big ideas? How are the three principles of sustainability showcased in tropical rain forests?Three approaches ecologists use to learn about ecosystems: field research, laboratory research, and ecosystem models. Google Earth and satellites offer a snapshot of our most remote ecosystems. Those snapshots, taken over time can be used to monitor change, and thus our affect on ecosystems. We need baseline data on the condition of the world’s ecosystems to see how they are changing and to develop effective strategies for preventing or slowing their degradation.The three big ideas are that:Life is sustained by the flow of energy from the sun through the biosphere, the cycling of nutrients within the biosphere, and gravity,Some organisms produce the nutrients they need, others survive by consuming other organisms, and some recycle nutrients back to producer organisms. Human activities are altering the flow of energy through food chains and webs and the cycling of nutrients within ecosystems and the biosphere.Producers within rain forests rely on solar energy to produce a vast amount of biomass through photosynthesis. Species living in the forests take part in, and depend on cycling of nutrients in the biosphere and the flow of energy through the biosphere. Tropical forests contain a huge and vital part of the earth’s biodiversity, and interactions among species living in these forests help to control the populations of the species living there.Critical ThinkingThe following are examples of the material that should be contained in possible student answers to the end of chapter Critical Thinking questions. They represent only a summary overview and serve to highlight the core concepts that are addressed in the text. It should be anticipated that the students will provide more in-depth and detailed responses to the questions depending on an individual instructor’s stated expectations.How would you explain the importance of tropical rainforests (Core Case Study) to people who think that such forests have no connections with their lives?Students might focus on the role these forests play as carbon sinks, tying up carbon that might otherwise contribute to climate change. Additionally, the biodiversity in rainforests affects the lives of people around the world because of the medicines that have been discovered there. And finally, weather patterns may be disrupted when the natural holding capacity of the forest is diminished and water simply runs off. Explain why: (a) the flow of energy through the biosphere depends on the cycling of nutrients, and (b) the cycling of nutrients depends on gravity (Concept 3-1B). The earth is closed to significant inputs of matter and has a fixed supply of nutrients that must be recycled to support life. Energy flows through living things in their feeding interactions, the basic components of which are recycled when plants photosynthesize, making molecules of sugars to be consumed.Gravity holds the atmosphere close to the earth, and enables the cycling of chemicals through air, water, soil, and organisms.Explain why microbes are so important. List two beneficial and two harmful effects of microbes on your health and lifestyle. Write a brief description of what you think would happen to you if microbes were eliminated from the earth.Microbes that decompose dead and decaying plant and animal materials are vital to all ecosystems. Their importance is often ignored but without them life would not exist. They consist of many different types of bacteria and fungi that secret enzymes that break down materials from other organisms into smaller components, and this enables nutrients to be recycled through the ecosystem as they are taken up from the soil and water by the producers. Two beneficial effects of microbes are their role in the recycling of matter and ensuring that there is no build-up of waste in the natural world. They are also used in the production of foods like cheese and yogurt. Two harmful effects of microbes are that they can cause diseases that can be detrimental to an individual’s health, and they can cause food to decay and be rendered unfit for human consumption.Make a list of the food you ate for lunch or dinner today. Trace each type of food back to a particular producer species. Describe the sequence of feeding levels that led to your feeding.Student answers will vary but could include some of the following: if a student had a burger and fries for lunch the bread can be traced back to wheat, the meat to cows and the grain that was fed to them, the lettuce and tomatoes to the original plants, and the fries to potatoes.Use the second law of thermodynamics (see Chapter 2, p. 47) to explain why many poor people in less-developed countries live on a mostly vegetarian diet.The second law of thermodynamics states that in any energy transformation, the energy quality will always decrease and we will end up with less usable energy than we began with. Much of the degraded energy is lost in the form of heat. Energy is lost at each trophic level in a food chain by as much as 90%. The earth can support more people if they ate at a lower level on the food chain by consuming grains, vegetables, and fruits directly. If these crops are fed to animals and pass through another trophic level, more energy is lost in the process. From an economic perspective it is also more costly to buy meat from cattle than it is to buy the grain that was used to feed them. People who live in rich developed countries can afford to live on a diet that is high in meat. However, people in poorer, less developed countries cannot afford to buy meat and live primarily on a vegetarian diet. In doing so they are behaving in a more energy efficient manner and in many cases a healthier one too.Why do farmers not need to apply carbon to grow their crops but often need to add fertilizer containing nitrogen and phosphorus?The crops that farmers grow obtain the carbon that they need directly from the atmosphere in the form of carbon dioxide. As the atmosphere is all around us, the farmer does not have to apply carbon to the fields to grow crops. This is part of the gas phase of the naturally occurring biogeochemical carbon cycle. Although the nitrogen cycle has a gas phase, plants cannot obtain the nitrogen they need directly from the air and must get it in the form of inorganic nitrogen compounds produced in the soil by the nitrogen cycle. Often the farmer grows and harvests crops at such a rate that the nitrogen demand cannot be kept up with by the nitrogen cycle, and so additional nitrogen in the form of fertilizer has to be added to the field. Similarly, phosphate, which does not have a gas phase in its very slow biogeochemical cycle, has to be absorbed into plant crops from the soil in the form of phosphate ions. Again the farmer often grows and harvests crops at such a rate that the naturally occurring levels of phosphate in the soil are diminished. A fertilizer high in phosphates then has to be applied to the field to compensate.What changes might take place in the hydrologic cycle if the earth’s climate becomes: (a) hotter, or (b) cooler? In each case explain how these changes might affect your lifestyle. (a) If the climate became hotter the hydrologic cycle could be adversely affected. The cycle could speed up and change global precipitation patterns, which in turn could affect the severity and frequency of storms, floods, and droughts. It could also enhance global warming by moving more water vapor into the atmosphere. An individual’s lifestyle could be affected by lack of water during droughts, too much water during floods causing landslides and mudslides, or increased exposure to disease causing organisms such as mosquitoes that reproduce in moist, humid climates that could result from increased rainfall in an area.(b) If the climate became cooler the hydrologic cycle could slow down and water would take more time to pass through this natural purification process. More freshwater could be trapped in the form of snow and ice in glaciers for a longer period of time, removing it from use for drinking, etc. by humans. Precipitation patterns could also change. A region may experience longer snow and ice coverage during winter, which could adversely affect the growing season in the area reducing the agricultural output. Another region may experience diminished rainfall, and water shortages could occur as aquifers are replenished at slower rates. Reduced water supplies has profound effects on the lifestyle of inhabitants of a region from not having enough drinking water to water rationing and bans on washing cars and watering lawns. What would happen to an ecosystem if: (a) all its decomposers and detritus feeders were eliminated, (b) all its producers were eliminated, or (c) all of its insects were eliminated? Could a balanced ecosystem exist with only producers and decomposers and no consumers such as humans and other animals? Explain. (a) The ecosystem would not be able to recycle matter, and wastes would build up. Eventually other species would die as no nutrients would be released for plant growth, etc. The ecosystem would be doomed to collapse.(b) The producers form the base of the food chain, and if they were removed then herbivores and subsequently carnivores would eventually die out as they both depend on the producers for the energy that sustains them. The ecosystem would also collapse in this scenario.(c) Ecosystem collapse is inevitable if all insects were removed. Pollination would cease and plant growth would be severely affected. Insects are intrinsically linked to two principles of sustainability (renewable solar energy and recycling of nutrients). Insects play a vital role in implementing these two scientific principles. If these parts of an ecosystem’s function were removed, sustainability cannot be achieved and the ecosystem would become unbalanced and unstable.A fully functioning ecosystem is made up of producers, consumers, and decomposers all interacting with each other and the abiotic components of the environment. The greater the biodiversity of the ecosystem, the greater the balance, stability, and sustainability there is in the ecosystem. Could an ecosystem function with only producers and decomposers? Theoretically a plant could be grown and not eaten by any consumer, then die and be decomposed by bacteria and fungi. However, neither the producers nor the decomposers would function fully. Their role in the ecosystem would not be realized and the ecosystem would be out of balance. Consumers are vital to the sustainable functioning of the ecosystem, whether they are the animals that eat the producers, such as herbivores, or the animals that help decompose the producers, such as the detritus feeders. In order for a balanced ecosystem to exist, it needs all of the interacting components—producers, consumers, and decomposers.List three ways you could apply Concept 3-3 and Concept 3-4 to making your lifestyle more environmentally sustainable.Answers may vary, but may include adopting a vegetarian diet, eating from lower trophic levels (especially in the case of many fish species that are top carnivores), and composting to recycle waste back into productive systems. List two questions that you would like to have answered as a result of reading this chapter.Student answers will vary and provide a good starting point for class discussion.Ecological Footprint Question Based on the following carbon dioxide emissions data and 2007 population data, answer the questions below.CountryTotal Carbon Footprint-Carbon Dioxide Emissions in Gigatonnes (109metric tons) (Gigatons (109 tons)) per yearPopulation in billions (2007)Per Capita Carbon Footprint (Per Capita Carbon Dioxide Emissions per year)China5.0 (5.5)1.3India1.3 (1.4)1.1Japan1.3 (1.4)0.13Russia1.5 (1.6)0.14United States6.0 (6.6)0.30WORLD29 (32)6.6 1. Calculate the per capita carbon footprint for each country and the world and complete the table. 2. It has been suggested that a sustainable average worldwide carbon footprint per person should be no more than 2.0 metric tons per person per year (2.2 tons per person per year). How many times larger is the U.S. carbon footprint per person than (a) the sustainable level, and (b) the world average?3. By what percentage will China, Japan, Russia, the United States, and the world each have to reduce their carbon footprints per person to achieve the estimated maximum sustainable carbon footprint per person of 2.0 metric tons (2.2 tons) per person per year? ANSWERS: 1. CountryTotal Carbon Footprint-Carbon Dioxide Emissions in Gigatonnes (109metric tons) [Gigatons (109short tons)] per yearPopulation in billions (2007)Per Capita Carbon Footprint (Per Capita Carbon Dioxide Emissions per year)China5.0 (5.5)1.33.8 metric tons (4.2 tons])India1.3 (1.4)1.11.2 metric tons (1.3 tons)Japan1.3 (1.4)0.1310 metric tons (11 tons)Russia1.5 (1.6)0.1411 metric tons (12 tons)United States6.0 (6.6)0.3020 metric tons (22 tons)WORLD29 (32)6.64.4 metric tons (4.8 tons) China:5.0 X 109 metric tons/1.3 X 109 people = 3.8 metric tons per person5.5 X 109 tons/1,3 X 109 people = 4.2 tons per personIndia: 1.3 X 109 metric tons/1.1 X 109 people = 1.2 metric tons per person1.4 X 109 tons/1.1 X 10 people = 1.3 tons per personJapan: 1.30 X 109 metric tons/0.133 X 109 people = 10 metric tons per person 1.4 X 109 tons/0.13X 109 people = 11 tons per personRussia: 1.5 X 109 metric tons/0.14 X 109 people = 11 metric tons per person 1.6 X 109 tons/ 0.14 X 109 people = 12 tons per personUnited States: 6.0 X 109 metric tons/0.30 X 109 people = 20 metric tons per person6.6 X 109 ton / 0.30 X 109 people = 22 tons per personWorld : 29 X 109 metric tons/6.6 X 109 people = 4.4 metric tons per person32 X 109 tons/6.6 X 109 people = 4.8 tons per person2. (a) How many times larger is the U.S. carbon footprint than the sustainable level?20 metric tons CO2 /person/year = 10 times greater2.00 metric tons CO2 /person/year 22 tons CO2 /person/year = 10 times greater2.20 tons CO2 /person/year2. (b) How many times larger is the U.S. carbon footprint than the world average?2020 metric tons CO2/person/year = 4.5 times greater4.4 metric tons CO2/person/year 22 tons CO2/person/year = 4.6 (4.58 times greater4.8 tons CO2 /person/year3. By what percentage will China, Japan, Russia, the United States, and the world each have to reduce their carbon footprints per person to achieve the estimated maximum sustainable carbon footprint per person of 2.0 metric tons (2.2 tons) per person per year?China: 3.8 metric tons per person – 2.0 metric tons per person = 1.8 metric tons per person1.8 metric tons per person/3.8 metric tons per person x 100 = 47%Japan: 10 metric tons per person – 2.0 metric tons per person = 8.0 metric tons per person8.0 metric tons per person/10 metric tons per person x 100 = 80%Russia: 11 metric tons per person – 2.0 metric tons per person = 9.0 metric tons per person9.0 metric tons per person/11 metric tons per person x 100 = 82%United States: 20 metric tons per person – 2.0 metric tons per person = 18 metric tons per person18 metric tons per person/20 metric tons per person x 100 = 90%World: 4.4 metric tons per person – 2.0 metric tons per person = 2.4 metric tons per person2.4 metric tons per person/4.4 metric tons per person x 100 = 55%Chapter 4Biodiversity and EvolutionSummary1.Evolution is the change in a population’s genetic makeup over time. Evolution forces adaptations to changes in environmental conditions in a population. The diversity of life on earth reflects the wide variety of adaptations necessary and suggests that environmental conditions have varied widely over the life of the earth.2.An ecological niche is a species’ way of life or its functional role in a community. Everything that affects its survival and reproduction (temperature tolerance, water needs, space needs, interactions with other organisms, etc.) is a part of that niche. The ecological niche helps a population survive by the adaptive traits that its organisms have acquired.3.Extinction of species and formation of new species constantly change the biodiversity of the earth.4.In the future, evolution will continue to influence our environment. Man’s use of artificial selection and genetic engineering to evolve species may have unintended consequences because evolution is a long, slow process and is unpredictable.Key Questions and ConceptsWhat is biodiversity and why is it important?CORE CASE STUDY. Some sharks play the role of keystone species in their environments. Nevertheless, about 32% of shark species are threatened with extinction. In addition to the roles sharks play in their environments, science stands to learn many things from these species. Many people argue that they should be saved simply because they have the right to exist. Biodiversity is the variety of species, genes, ecosystems, and ecosystem processes.1. Species are individuals that can make and produce viable offspring. 2. Species diversity, genetic diversity, ecosystem diversity, and functional diversity.Biomes are large regions with distinct climates and certain species that are adapted to them. Individuals Matter: E.O Wilson has been a large influence on conservation efforts. His early work included discovering how ants communicate and developing the theory of island biogeography.SCIENCE FOCUS: Insects often have a bad reputation and are considered pests. However the ecological roles they play in pollinating flowering plants and controlling other insect populations make them invaluable to humans.How does the earth’s life change over time?A. Most of what we know of the history of life comes from the fossil record. B.Evolution is the change in a population’s genetic makeup over time.C.All species descend from earlier, ancestral species—theory of evolution.1.In 1858 Charles Darwin and Alfred Russel Wallace independently proposed natural selection as the mechanism of evolution. 2. Natural selection occurs when members of a population have genetic traits that improve their ability to survive and produce offspring with those specific traits.3. For natural selection to work on a population, three steps occur:a.The development of genetic variability.i. Mutations are random changes in the structure/number of DNA molecules in a cell.ii. Mutations occur in two ways. 1. Gene DNA is exposed to external agents like X-rays, chemicals (mutagens), or radioactivity. 2. Random mistakes that occur in coded genetic instructions.b.Natural selection: environmental conditions favor some individuals over others by virtue of adaptive traits. c.populations evolve such that they are better adapted to survive and reproduce under existing conditions. CASE STUDY. Humans have thrived so well as a species because of their strong opposable thumbs, ability to walk upright and complex brain. These adaptations may not prove as beneficial as the environment continues to change, though our powerful brain may allow us to live more sustainably in the future. 4. Natural selection can only act on existing genes and is limited by reproductive capacity.5. Three common misconceptions about evolution. a. Fitness is a measure of strength.b. Organisms develop certain traits because they need them.c. Evolution works according to some grand plan. 4-3 How do geological processes and climate change affect evolution?A.Processes such as the shifting of tectonic plates, volcanic eruptions, and earthquakes influence earth’s climate and in turn affect evolution by removing and/or isolating habitats and species.B.Long-term climate changes relocate ecosystems, thus determining where certain species can live.C.Asteroids and meteorites have caused environmental stress and mass extinctions.SCIENCE FOCUS: Earth is uniquely suited to support life because of its average temperature, distance from the sun, size and atmospheric composition.4-4 How do speciation, extinction, and human activities affect biodiversity?A.Natural selection can lead to development of an entirely new species.In speciation, two species arise from one when some members of a population cannot breed with other members to produce fertile offspring. Speciation occurs in two phases:1.Geographic isolation, physical separation for long time periods.2.Reproductive isolation. B.When population members cannot adapt to changing environmental conditions, the species becomes extinct.1. Endemic species (those found in only one place) are especially vulnerable.C.When local environmental conditions change, some species will disappear at a low rate; this is called background extinction.D.Mass extinction is a significant rise in extinction rates above the background extinction level. Usually, 25–95% of species are lost. There appear to have been at least three and perhaps five mass extinctions on earth.SCIENCE FOCUS: Artificial selection involves crossbreeding between genetic varieties of the same species to give rise to populations with desirable traits. Now, scientists can use genetic engineering to produce desirable traits or eliminate undesirable ones. 4-5 What is species diversity and why is it important?A. Species diversity is the number of species (richness) combined with their relative abundance (evenness).B. Species rich communities tend to be more stable and more productive.SCIENCE FOCUS: The size of a habitat and its isolation affect the species richness of that habitat island.4-6 What roles do species play in ecosystems?A.Ecological niche is a species’ way of life in an ecosystem, everything that affects its survival and reproduction.B.Some species have broad ecological roles and are termed generalist species.C.Some species have narrow ecological roles and are termed specialist species.CASE STUDY: Cockroaches are the ultimate generalists. The can survive extreme conditions and have a wide variety of adaptations that allow them to avoid predation. D. Niches can be occupied by native or non-native species.E. Indicator species provide early warning of ecosystem damage because they have a narrow range of tolerance.CASE STUDY: Amphibians are indicator species that are declining globally. Factors affecting their survival include habitat loss, drought, pollution, an increase in UV radiation, parasites, fungal diseases, climate change, overhunting, and introduction of non-native species. Their role as indicator species is cause for alarm on a global scale. H. Keystone species have a large affect on maintaining balance within an ecosystem. 1. Can be, but are not necessarily, pollinators and top predators. CASE STUDY: Alligators act as a keystone species, yet their numbers were seriously compromised by over-hunting. Their activities provide important habitat for fish and avian species. They also control populations by their feeding behaviors. In 1967 the alligator was placed on the endangered species list and has made a dramatic recovery. 2. Foundation species create and enhance habitats that benefit other species.Additional Video ResourcesBeavers: IMAX (1998)An engaging look at the charismatic ecosystem engineers. The Habitable Planet: A Systems Approach to Environmental Science, Many planets, One Earth (Documentary series, 2007). This segment looks at clues to help explain the rise of complex animal life on earth. —Evolution: Extinction!Main Website: Planet Earth (BBC Series, 5 discs)An exploration of global ecosystems. Web ResourcesIUCN Red ListThe IUCN Species Survival Commission’s list of threatened and endangered species around the globe. of LifeAn attempt to document all species of life on earth. Answers to End of Chapter QuestionsReview QuestionsReview the Key Questions and Concepts for this chapter on p. 81. Describe the threats to many of the world’s shark species (Core Case Study) and explain why we should protect sharks from extinction as a result of our activities. Sharks are victim to our misconceptions about them. Many people fear sharks and for that reason they have been hunted and killed in many cases to the point of being threatened with extinction. Many sharks, however, act as keystone species in their ecosystems, so they are vitally important. What are the four major components of biodiversity (biological diversity)? What is the importance of biodiversity? What are species? Describe the importance of insects. Define and give three examples of biomes. Biological diversity, or biodiversity, is the variety of the earth’s species, the genes they contain, the ecosystems in which they live, and the ecosystem processes such as energy flow and nutrient cycling that sustain all. Biodiversity is a vital renewable resource.A species is a set of individuals that can mate and produce fertile offspring. Insects are pollinators and help sustain life on earth. Biomes are large regions with distinct climates and a set of species that are adapted to that climate. Examples include forests, deserts, and grasslands. What is a fossil and why are fossils important in understanding the history of life? What is biological evolution? Summarize the theory of evolution. What is natural selection? What is a mutation and what role do mutations play in evolution by natural selection? What is an adaptation (adaptive trait)? What is differential reproduction and why is it important? How did we become such a powerful species? What are two limits to evolution by natural selection? What are three myths about evolution through natural selection?Fossils are mineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, and seeds, or impressions of such items found in rocks that help to tell us the history of the earth. Biological evolution is the process whereby Earth’s life changes over time through changes in the genetic characteristics of populations.The theory of evolution holds that all species descended from earlier, ancestral species. In other words, life comes from life.Natural selection is the process in which individuals with certain traits are more likely to survive and reproduce under a particular set of environmental conditions than those without the traits. Mutations are random changes in the DNA molecules of a gene in any cell. Mutations can result from random changes that occur spontaneously within a cell or from exposure to external agents, such as radioactivity. Mutations can occur in any cell, but only those taking place in genes of reproductive cells are passed on to offspring. Sometimes such a mutation can result in a new genetic trait, called a heritable trait, which can be passed from one generation to the next. In this way, populations develop differences among individuals, including genetic variability. Adaptation, or adaptive trait, is any heritable trait that improves the ability of an individual organism to survive and to reproduce at a higher rate than other individuals in a population can under prevailing environmental conditions. For natural selection to occur, individuals with adaptive traits must have differential reproduction, which enables individuals with the trait to leave more offspring than other members of the population leave.Human success is attributed to three adaptations: strong opposable thumbs that allow us to grip and use tools better than the few other animals that have thumbs; an ability to walk upright, which gives us agility and frees up our hands for many uses; and a complex brain, which has allowed us to develop many skills, including the ability to use speech to transmit complex ideas. Two limits to evolution by natural selection include: a change in environmental conditions, which can lead to such an adaptation only for genetic traits already present in a population’s gene pool, or for traits resulting from mutations; and even if a beneficial heritable trait is present in a population, the population’s ability to adapt may be limited by its reproductive capacity.Three misconceptions: “Survival of the fittest” means “survival of the strongest.”Organisms develop certain traits because they need them.Evolution by natural selection involves some grand plan of nature in which species become more perfectly adapted.Describe how geologic processes can affect natural selection. How can climate change and catastrophes such as asteroid impacts affect natural selection? Describe conditions on the earth that favor the development of life as we know it. Tectonic plate movements, volcanic eruptions and earthquakes have shifted wildlife habitats, wiped out large numbers of species, and created opportunities for the evolution of new species.Climate change and asteroids have shifted the locations of ecosystems and created opportunities for evolution.Life on the earth, as we know it, can thrive only within a certain temperature range, which depends on the liquid water that dominates the earth’s surface.What is speciation? Distinguish between geographic isolation and reproductive isolation and explain how they can lead to the formation of a new species. Distinguish between artificial selection and genetic engineering and give an example of each. Speciation is when one species splits into two or more different species. For sexually reproducing organisms, a new species is formed when one population of a species has evolved to the point where its members no longer can breed and produce fertile offspring with members of another population that did not change or that evolved in a different way. Geographic isolation occurs when different groups of the same population of a species become physically isolated from one another for a long period of time. For example, part of a population may migrate in search of food and then begin living as a separate population in another area with different environmental conditions. Populations can also be separated by a physical barrier (such as a mountain range, stream, or road), a volcanic eruption, tectonic plate movements, or winds or flowing water that carry a few individuals to a distant area. In reproductive isolation, mutation and change by natural selection operate independently in the gene pools of geographically isolated populations.Artificial selection enables a change in the genetic characteristics of populations by selecting one or more desirable genetic traits in the population of a plant or animal such as a type of wheat, fruit, or dog. Then selective breeding is used to generate populations of the species containing large numbers of individuals with the desired traits. Genetic engineering is the alteration of an organism’s genetic material through adding, deleting, or changing segments of its DNA to produce desirable traits or eliminate undesirable ones. It enables scientists to transfer genes between different species that would not interbreed in nature. For example, genes from a fish species can be put into a tomato plant to give it certain properties. Scientists have used genetic engineering to develop modified crop plants, new drugs, pest-resistant plants, and animals that grow rapidly.What is extinction? What is an endemic species and why can such a species be vulnerable to extinction? Distinguish between background extinction and mass extinction. Extinction is a process in which an entire species ceases to exist (biological extinction) or a population of a species becomes extinct over a large region, but not globally (local extinction). Species that are found in only one area are called endemic species and are especially vulnerable to extinction because they are unlikely to be able to migrate or adapt in the face of rapidly changing environmental conditions. Throughout most of the earth’s long history, species have disappeared at a low rate, called background extinction. Mass extinction is a significant rise in extinction rates above the background level. In such a catastrophic, widespread, and often global event, large groups of species (25–95% of all species) are wiped out worldwide in a few million years or less.What is species diversity? Distinguish between species richness and species evenness and give an example of each. Describe the theory of island biogeography (species equilibrium model). According to this theory, what two factors affect the immigration and extinction rates of species on an island? What are habitat islands? Explain why species-rich ecosystems tend to be productive and sustainable. An important characteristic of a community and the ecosystem to which it belongs is its species diversity: the number of different species it contains (species richness) combined with the relative abundance of individuals within each of those species (species evenness). A biologically diverse community such as a tropical rain forest or a coral reef with a large number of different species (high species richness) generally has only a few members of each species ( low species evenness). A single tree in a tropical forest in Panama may house an estimated 1,700 different beetle species but only a few individuals of each species. In contrast, an aspen forest community in Canada may have only a few plant species (low species richness) but large numbers of each species (high species evenness). The theory of island biogeography, or species equilibrium model, is a widely accepted scientific theory that states that the number of different species (species richness) found on an island is determined by the interactions of two factors: the rate at which new species immigrate to the island and the rate at which species become extinct, or cease to exist, on the island. The model projects that, at some point, the rates of species immigration and species extinction should balance so that neither rate is increasing or decreasing sharply. This balance point is the equilibrium point that determines the island’s average number of different species (species richness) over time. The two factors affecting immigration and extinction are island size and isolation. Habitat islands are areas of habitat surrounded by a fragmented landscape. Species diversity is a major component of biodiversity and tends to increase the sustainability of some ecosystems. Research suggests that species richness affect an ecosystem because plant productivity is higher in species- rich ecosystems and species richness enhances the stability, or sustainability of an ecosystem.What is an ecological niche? Distinguish between specialist species and generalist species and give an example of each. Why do some scientists consider the cockroach to be one of evolution’s greatest success stories?An important principle of ecology is that each species has a specific role to play in the ecosystems where it is found. Scientists describe the role that a species plays in its ecosystem as its ecological niche, or simply niche. It is a species’ way of life in a community and includes everything that affects its survival and reproduction, such as how much water and sunlight it needs, how much space it requires, and the temperatures it can tolerate. Generalist species have broad niches. They can live in many different places, eat a variety of foods, and often tolerate a wide range of environmental conditions. Flies, cockroaches, mice, rats, white-tailed deer, raccoons, and humans are generalist species. Specialist species occupy narrow niches. They may be able to live in only one type of habitat, use one or a few types of food, or tolerate a narrow range of climatic and other environmental conditions. For example, tiger salamanders breed only in fishless ponds where their larvae will not be eaten. Cockroaches are excellent generalists that can survive in and colonize nearly any environment on earth. Distinguish among native, nonnative and indicator species and give an example of each type. What major ecological roles do amphibian species play? List nine factors that help to threaten the health of frogs and other amphibians with extinction. What are three reasons for protecting amphibians? Distinguish between keystone and foundation species. Describe the role of some sharks as keystone species. Describe the role of the American alligator as a keystone species and how it was brought back from near extinction. Describe the role of beavers as a foundation species. Native species are those species that normally live and thrive in a particular ecosystem. Other species that migrate into, or are deliberately or accidentally introduced into, an ecosystem are called nonnative species, also referred to as invasive, alien, and exotic species. The African bee would be native to Africa but a nonnative to Brazil.Species that provide early warnings of damage to a community or an ecosystem are called indicator species. The presence or absence of trout species in water at temperatures within their range of tolerance is an indicator of water quality because trout need clean water with high levels of dissolved oxygen.Amphibians help to control insect populations.Nine factors:Habitat lossDroughtIncreases in UV radiationParasitesViral and fungal diseasesPollutionClimate changeOverhuntingNon-native speciesThree reasons:They are indicator species.They control insect populations.They are a storehouse of pharmaceutical chemicals.Keystone species are species whose roles have a large effect on the types and abundances of other species in an ecosystem (e.g., the American Alligator). Foundation species play a major role in shaping communities by creating and enhancing their habitats in ways that benefit other species. For example, elephants push over, break, or uproot trees, creating forest openings in the woodlands of Africa. Birds are excellent indicator species because they are found almost everywhere and are affected quickly by environmental changes, such as loss or fragmentation of their habitats and introduction of chemical pesticides.Some sharks are keystone species, helping to remove injured and sick animals from the oceans. As most American alligators were eliminated from their natural areas in the 1950s, scientists began pointing out the ecological benefits these animals had been providing to their ecosystems (such as building water holes, nesting mounds, and feeding sites for other species). Since that time, they were placed on the endangered species list, and their numbers have increased dramatically. Beavers are another good example of a foundation species. Acting as “ecological engineers,” they build dams in streams to create ponds and other wetlands used by other species. Some bat and bird foundation species help to regenerate deforested areas and spread fruit plants by depositing plant seeds in their droppings.What are this chapter’s three big ideas? How are ecosystems and the variety of species they contain related to the three principles of sustainability?Three big ideas: Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits (natural selection).Human activities are decreasing the earth’s vital biodiversity by causing the extinction of species and by disrupting habitats needed for the development of new species.Each species plays a specific ecological role (ecological niche) in the ecosystem where it is found.Ecosystems are storehouses of biodiversity that are solar powered and that recycle matter. Ecosystems are a model for sustainability. Critical ThinkingThe following are examples of the material that should be contained in possible student answers to the end of chapter Critical Thinking questions. They represent only a summary overview and serve to highlight the core concepts that are addressed in the text. It should be anticipated that the students will provide more in-depth and detailed responses to the questions depending on an individual instructor’s stated expectations.How might we and other species be affected if all of the world’s sharks were to go extinct?The ecosystem would be very much altered because sharks act as keystone species. Some species of shark play crucial roles in keeping their ecosystems functioning by feeding at the top of the food web and ridding the ecosystem of injured and sick animals. Without this service, the food web would be greatly altered. What role does each of the following processes play in helping implement the four scientific principles of sustainability: (a) natural selection, (b) speciation, and (c) extinction? (a) Natural selection implements all four principles of sustainability. Solar energy produces the plants that provide the energy and food for a great biodiversity of creatures living on the planet. Predator-prey relationships help to maintain the “survival of the fittest” implications in natural selection and control population. The nutrients in the remains of the prey then get recycled back through the system.(b) Speciation impacts the biodiversity principle of sustainability. The more new species arise as a result of speciation, the greater the biodiversity of the ecosystem. If the new species is a predator it could also impact the population control principle of sustainability.(c) Extinction results directly in a loss of biodiversity as the species is lost from the gene pool. The nutrients in the species will be recycled through the ecosystem as the numbers decline until no more of the species are left. If the species that has become extinct was a predator species, then it could also impact the population control principle of sustainability. How would you respond to someone who tells you: (a) that he or she does not believe in biological evolution by natural selection because it is “just a theory,” and (b) that we should not worry about air pollution because natural selection will enable humans to develop lungs that can detoxify pollutants?(a) A theory is part of the process that scientists follow when investigating scientific evidence in order to explain their observations. For a theory to be validated it has to be accepted by the scientific community and reviewed by the world’s leading scientists. It has to stand up to scientific scrutiny. There is much fossil evidence to indicate that evolution through natural selection has taken place. There are also some examples that evolution is in action today as evidenced by the color changes in moths that has taken place since the industrial revolution. Indeed, evolution may just be a theory, but to date the theory has stood the test of time within the scientific world. Until a better scientific explanation is put forward it will remain the explanation of choice. Physicists and mathematicians give credence to the theory of relativity, because as yet no one has proven it wrong. Even Einstein said that a thousand experiments can prove him right, but it would take only one experiment to prove him wrong. As yet, that experiment has not been conducted so the theory of relativity, like the theory of evolution, remains the best scientific explanation of our observations.(b) Unfortunately, with the human species and other large species that do not reproduce large numbers of offspring rapidly, natural selection will not take place quickly enough for our lungs to become resilient to air pollution. Maybe this adaptation could take place over thousands or even millions of years, but in someone’s own lifespan this is not feasible. It is more feasible to tackle the problem of air pollution and bring about its reduction, than it is to assume that humans will be able to adapt to these undesirable environmental conditions in the short term.Describe the major differences between the ecological niches of humans and cockroaches. Are these two species in competition? If so, how do they manage to coexist?Both cockroaches and humans are generalist species having very broad niches. This means that they can live in many different places, eat a variety of foods, and tolerate a wide range of environmental conditions. Cockroaches have been around for 350 million years and have thrived throughout the evolutionary process. Humans are a recent addition to the planet. Cockroaches eat almost anything and can live anywhere except in the polar regions. They can go for a month without food, survive for a month on one drop of water, and can withstand high doses of radiation. Some cockroaches can even survive being frozen. These traits are in contrast to humans. Additionally humans do not reproduce as fast as cockroaches, which have a very high reproductive rate. Unlike humans, cockroaches also eat their own dead, and if food is scarce will even eat each other! Although cockroaches do live in homes that are occupied by humans, they are not directly in competition with each other for resources. However, cockroaches can evade been stepped on, as they have rapid response times, and the ability to see virtually in all directions at once. Cockroaches carry bacteria and viruses that cause diseases in humans, and can cause allergic responses in susceptible individuals.How would you experimentally determine whether an organism is (a) a keystone species and (b) a foundation species?(a) A controlled experiment could be performed similar to the one conducted by Robert Paine on the rocky shoreline of the Pacific coast of Washington State. He demonstrated the keystone role of the top-predator sea star Piaster orchaceus in an intertidal zone community. Paine removed these mussel-eating sea stars from one rocky shoreline community but not from an adjacent community, which served as the control group. Mussels took over and crowded out many other species in the community without the Piaster sea stars. This type of experiment could be performed in other areas, with different species, to assess the role that certain species have in an ecosystem and whether a species could be classified as a keystone species.(b) Similarly, a removal experiment could be designed in a region to assess if the absence of a species leads to significant changes in the overall environment. Foundation species effectively engineer their environment to provide new and different habitats. In their absence, these alterations would not occur and the relative abundance or species dependent upon the altered landscape would change. Is the human species a keystone species? Explain. If humans were to become extinct, what are three species that might also become extinct and three species whose population would probably grow?Humans are likely a keystone species by virtue of their technology and the extreme manner in which they influence their habitat. Were we to become extinct, their domesticates would most likely not survive. These would include pets, livestock, and crop plants. Species whose populations would likely grow would be the ones human activities have had a detrimental effect on, such as whales, mountain gorillas, and the many weeds we struggle to keep in check. How would you respond to someone who says that because extinction is a natural process, we should not worry about the loss of biodiversity when species become extinct as a result of our activities?It is true that as environmental conditions change some species may begin to disappear at a low rate. This is the background extinction rate, and annually is around one to five species for every million species on the planet. However, scientists such as E. O. Wilson suggest that human activities have increased the extinction rate to somewhere between 100 and 1000 times the natural background rate. As more and more habitat is disturbed by human use and the resulting declines in biodiversity take place, we could lose many species from the earth over a relatively small time scale. Tropical rain forests, coral reefs, and wetlands are some of the most biodiverse areas on the earth, yet these are the regions that are under the most threat. Loss of biodiversity in these regions will have a major effect on the ecosystems and bring about extinction rates that are well above the naturally occurring background rates.List three ways you could apply concept 4-4B in order to live a more environmentally sustainable lifestyle. Answers may vary. Students may suggest that they would attempt to limit the effects of habitat fragmentation by planting native vegetation in their yards in order to create or contribute to a habitat corridor. They could limit the extent to which their economic activities support deforestation and habitat loss in foreign countries. They might also pursue political activity to oppose massive habitat loss through the conversion of land into agriculture or suburban land uses. Congratulations! You are in charge of the future evolution of life on the earth. What are the three things that you would consider to be the most important to do?Student answers will vary but could include: increased conservation, preservation, and protection of habitat that allows for greater biodiversity and ecosystem stability through continuing evolutionary processes; learn how to work and live within the four principles of sustainability and apply these to the human ecosystem; and address some of the main anthropogenic causes of environmental degradation and take measures to remedy these issues expediently to offset the negative effects that they may have on the evolution of species-global warming, ozone thinning, etc.List two questions that you would like to have answered as a result of reading this chapter.Student answers will vary and provide a good starting point for discussion.Data Analysis This graph shows data collected by scientists investigating island biogeography. It shows measurements taken for two variables: the area within which measurements were taken and the population density of a certain species of lizard found in each area. Note that the areas studied varied from 100 square meters (m2) (1,076 square feet) to 300 m2 (3,228 square feet) (x-axis). Densities measured varied from 0.1 to 0.4 individuals per m2 (y-axis). Study the data and answer the following questions.How many measurements below 0.2 individuals per m2 were made? How many of these measurements were made in areas smaller than 200 m2? How many were made in areas larger than 200 m2?431How many measurements above 0.2 individuals per m2 were made? How many of these measurements were made in areas smaller than 200 m2? How many were made in areas larger than 200 m2?835Do your answers support the hypothesis that larger islands tend to have higher species densities? Explain.Yes, this data indicates a trend that larger islands tend to have higher species densities, and thus lends support (fails to refute) the hypothesis. ................
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