CH-5-6 Biodiversity, Species Interactions, and Population Control – Living in the Environment: Principles, Connections, and Solutions : Book Guide

This Document Contains Chapters 5 to 6 Chapter 5 Biodiversity, Species Interactions, and Population Control Summary 1. Two major factors affect the number of species in a community: the latitude in terrestrial communities and salinity/nutrients in aquatic systems. 2. Species play different roles in a community. Native species sustain the ecosystem in which they are a part. Some nonnative species will crowd out native species. Indicator species alert us to harmful changes in the community. Keystone species play ecological roles in the specific community: they may assist in pollination help regulate populations. Foundation species affect the community’s habitat to benefit other species. 3. Species interact with each other in these different ways: interspecific competition, predation, parasitism, mutualism, and commensalism. 4. As environmental conditions change, one species may be replaced by other groups of species. This gradual change in the composition of species in a given area is called ecological succession. 5. A community has three aspects of sustaining itself: its persistence, the ability to resist being altered, its constant population, and its resilience in repairing damage. High biodiversity may give a community some edge in surviving, but we do not know this for certain. Key Questions and Concepts 5-1 How do species interact? CORE CASE STUDY. Sea otters are a keystone species found on the west coast of the United States that are endangered. For many years they have been in recovery. Why should we be concerned about their status? Sea otters are charismatic, they generate tourist revenue, and they are very valuable in terms of controlling biological populations. A. Five basic species interactions are competition, predation, parasitism, mutualism, and commensalism. B. Competition between species for food, sunlight, water, soil, space, nest sites, etc. is interspecific competition. 1. With intense competition for limited resources, one species must migrate, shift its feeding habits/behavior, or face extinction. 2. As humans take more and more space, other species are compromised. C. In competitive situations, some species evolve adaptations that reduce/avoid competition for resources. 1. Over a long time, species evolve more specialized traits that allow them to use shared resources at different times, in different ways, or in different places; this is termed resource partitioning. 2. Predator-prey relationships define one species (the predator) feeding/preying on another. 3. Predators have a variety of ways to capture prey. Herbivores feed on immobile plant species; carnivores use pursuit of prey or ambush to capture prey. Some predators use camouflage, and others use chemical warfare (venom) to capture prey or deter predators. 4. Prey species escape predators in a number of different ways such as swift movement, protective shells, camouflage, or use of chemicals to repel or poison. SCIENCE FOCUS: Giant kelp forests are very productive and biologically diverse ecosystems. Sea urchins are a major threat to kelp, but sea otters keep their populations in check. Polluted water and the warming of the world’s oceans also threaten kelp forests. If kelp forests decline significantly, many other species could be affected. 5. Coevolution is when predator and prey can exert intense natural selection pressures on one another. D. Parasitism, mutualism, and commensalism. 1. Parasites live on or in another species. The host of this arrangement is obviously harmed by it, but the parasite can contribute to biodiversity by controlling the size of specific species populations. 2. Mutualism is a relationship that benefits both species; these benefits can be in dispersing pollen and seeds for reproduction, in receiving food, or in receiving protection. a. Mutualism is not cooperation; each species exploits the other. E. Some species interactions help one species but does nothing for the other; this is commensalism. Examples of this are the bromeliads and orchids (epiphytes). 5-2 What limits the growth of populations? A. Populations change in size, density, and age distribution; most members of populations live together in clumps or groups. 1. Three general patterns of population distribution occur in a habitat: clumping, uniform distribution, and random dispersion. Most species live in clumps or groups. a. Availability of resources varies from place to place. b. Living in groups offers better protection from predators. c. Some predator species live in packs to have a better chance of getting a meal. d. Temporary groups may form for mating and caring for young. 2. Uniform pattern distribution may occur where a resource such as water is scarce. B. Four variables influence/govern population size: birth, death, immigration, and emigration. 1. Increase in population occurs by birth and immigration. 2. Decrease in population occurs by death and emigration. 3. Age structure of a population is usually described as a pre-reproductive stage, the reproductive stage, and the post-reproductive stage. A population with a large reproductive stage is likely to increase while a population with a large post-reproductive stage is likely to decrease. 4. Each population has a range of tolerance to variations in the environment. 5. The limiting factor principle states that too much or too little of a physical or chemical factor can limit population growth even if all other factors are optimal. SCIENCE FOCUS: Many human activities have had detrimental effects of sea otter populations. Their low reproductive rate has limited their ability to increase in numbers. C. Rapidly growing populations typically reproduce early in life, have many offspring, and reproduce many times with short intervals between reproductive events. D. There are always limits to population growth in nature. E. Environmental resistance is all factors that limit the growth of a population, and largely determine an area’s carrying capacity. F. Exponential growth starts slow then accelerates, yielding a J-curve. CASE STUDY. White tailed deer populations were in decline 100 years ago, due to habitat loss and hunting. Subsequent protection and decline in their natural predators led to a drastic increase in their numbers to the extent that they have become a nuisance and even a danger on the urban edge. Efforts to control their populations are very complicated, and in many cases expensive. G. Exponential growth leads to logistic growth and may lead to the population overshooting the environment’s carrying capacity. 1. Overshooting an environment’s resources often is a result of a reproductive time lag. 2. The reproductive time lag can produce a dieback/crash of organisms unless the organisms can find new resources or move to an area with more resources. H. Carrying capacities can fluctuate seasonally or from year to year. I. Species use different reproductive patterns. 1. Some have many offspring and give them little protection. 2. Some have few offspring that are cared for by their parents. J. Population density is the number of individuals per unit area. 1. Density-independent population controls affect a population’s size regardless of its density. 2. Density-dependent population controls have a greater effect on the population as its density increases. Infectious disease is an example of density-dependent population control. K. Four general types of population fluctuations in nature are: stable, irruptive, cyclic, and irregular. 1. A stable population fluctuates slightly above and below carrying capacity and is characteristic of many species living under fairly constant environmental conditions. 2. Some species have a fairly stable population size that may occasionally irrupt to a high peak and then crash to below carrying capacity. This is characteristic of short-lived, rapidly reproducing species. 3. Cyclic fluctuations occur over a regular time period, generally a multiple-year cycle. A. Humans are not exempt from population crashes. Examples include the Irish potato famine, the bubonic plague, and the current AIDS epidemic. 5-3 How do communities and ecosystems respond to changing environmental conditions? A. With new environmental conditions, community structures can change; one group of species is replaced by another. 1. Ecological succession is the gradual change in species composition of a given area. 2. Primary ecological succession is the gradual establishment of biotic communities on lifeless ground; in the soil there is no terrestrial community; in an aquatic community, there is no bottom sediment. This process generally takes a very long time. 3. Secondary ecological succession defines a series of communities with different species developing in places with soil or bottom sediment. The soil or sediment remains after the natural community of organisms has been disturbed, removed, or destroyed. a. Forest fires or deforestation, for example, can convert a particular stage of succession to an earlier stage. B. The classic view of ecological succession is that it is an orderly sequence, each stage leading to the next, more stable stage until a climax community is reached. Such a community would represent the balance of nature, one dominated by a few long-lived plant species that is in balance with its environment. C. Changes in environmental conditions that disrupt a community can set back succession. 1. Scientists can’t predict the course of a given succession in a community toward a stable climax community in balance with its environment. SCIENCE FOCUS: Three factors that affect ecological succession. Facilitation is when a species makes an area more suitable for other species. Inhibition occurs when early successional species hinder the establishment of other species. Tolerance is when later plants are unaffected by plants that came in during earlier stages. D. Living systems are sustained through change. 1. Stability, the capacity of an ecosystem to withstand external stress and disturbance, is maintained by constant change in response to changing environmental conditions. a. Inertia or persistence is the ability of a system to survive moderate disturbances. b. Resilience is the ability to be restored through secondary succession. Teaching Tips Large Lecture Courses: Compare and contrast r-selected and K-selected species on the board. Take an example of an r-selected species most of the group will be familiar with. Review some points about its natural history. Next, engage the class in determining how, if they were the researchers, they might determine the carrying capacity of that species. How can K be determined in a humane way? How do we know what K is for humans? What are the inevitable consequences of finding out? Smaller Lecture Courses: Most species compete with one another for certain resources. This is a generalization in the biological world. Does it apply to humans? If so, in what way? You might work with the group as a whole, or break them into groups, each focusing on some aspect of human survival, such as agriculture or epidemiology. Are we really free from competition, or are we constantly competing? Key Terms age structure carrying capacity coevolution commensalism ecological succession environmental resistance inertia interspecific competition limiting factor limiting factor principle mutualism parasitism persistence population population crash population density predation predator-prey relationship primary ecological succession range of tolerance resilience resource partitioning secondary ecological succession Term Paper Research Topics 1. Niche: relationships among species in a particular ecosystem, pick-a-predator, resource partitioning versus direct competition strategies. 2. Unusual niches: write a case study of a particular alien species, indicator species, or keystone species. 3. Competition and predation: important features of natural selection, the competitive exclusion principle. 4. Making peace in natural ecosystems: resource partitioning, symbiotic relationships. 5. Ecological succession: the role of humans in succession, the role of fires and chaos in determining succession. 6. Do diversity and stability go together? 7. The theory and application of island biogeography. 8. Field and laboratory methods used in ecological research: measuring net primary productivity and respiration rates; analyzing for particular chemicals in the air, water, and soil; studying relationships among species; population studies; computer modeling of ecological interrelationships. 9. Research management strategies for predator control. 10. Research wildlife management strategies that rely on human control of successional stages of development. 11. Field methods of ecological research: relationships among species; computer modeling of ecological interrelationships. 12. Restoration of degraded ecosystems such as Lake Erie; coastal zone management. Discussion Topics 1. Do predators fulfill a valuable ecological function or should their numbers be reduced? Answer: Predators play a crucial role in maintaining ecological balance by controlling prey populations, which helps prevent overgrazing and supports biodiversity. Reducing predator numbers can lead to imbalances, affecting the entire ecosystem. Therefore, predators fulfill a valuable ecological function that supports overall ecosystem health. 2. What lessons for human societies can be drawn from a study of species interactions in ecosystems? Answer: Studying species interactions reveals the importance of balance and interconnectedness in systems. Human societies can learn about the benefits of preserving biodiversity, the risks of disrupting natural processes, and the value of considering ecological impacts in resource management and development decisions. 3. How should we manage predator populations? Answer: Managing predator populations requires a balanced approach, including habitat preservation, monitoring prey populations, and applying targeted management strategies when necessary. The goal should be to maintain ecological balance and prevent negative impacts on both predator and prey species, using science-based and adaptive management practices. 4. What can be done to decrease the incidence and impacts of invasions of nonnative species? Answer: To reduce the incidence and impacts of nonnative species invasions, strategies include improving biosecurity measures, monitoring and early detection, rapid response and eradication efforts, and public education. Preventing introductions through stringent regulations and promoting habitat restoration can also be effective. 5. What is the wisest strategy to handle fires in natural ecosystems? Answer: The wisest strategy for handling fires involves adopting a fire management plan that includes prevention, controlled burns, and preparedness. Understanding the role of fire in the ecosystem, allowing natural fires to occur when safe, and managing fuel loads can help maintain ecological health while reducing the risk of uncontrolled fires. 6. What are the most appropriate applications of the theory of island biogeography? Answer: The theory of island biogeography is applicable in conservation biology for designing reserves and understanding species diversity in isolated habitats. It helps in planning protected areas, managing fragmented landscapes, and studying species-area relationships to inform conservation strategies and biodiversity preservation. 7. To what extent should we disrupt and simplify natural ecosystems for our food, clothing, shelter, and energy needs and wants? Answer: Disrupting and simplifying natural ecosystems should be minimized to reduce adverse environmental impacts. Sustainable practices and technologies should be prioritized to meet human needs while preserving ecosystem functions and biodiversity. Balancing resource use with ecological preservation is key to long-term environmental health. Activities and Projects 1. Organize a class trip to a natural area such as a forest, grassland, or estuary to observe a variety of species interactions. Arrange for an ecologist or a naturalist to provide interpretive services. 2. Organize a class trip to an abandoned field, coastal dune, rock outcrop, or other disturbed area and observe the various aspects of ecological succession. If possible, visit and compare two areas that have experienced different types of disturbance. 3. Find works of literature, art, and music that depict species interactions in natural ecosystems. Draw as many parallels between species interaction and your own experiences as you can. 4. Arrange a field trip providing opportunities to compare and contrast ecosystems of several different types, including some damaged or stressed by human activities. Invite an ecologist or biologist along to identify and discuss specific examples of species adaptation to environmental conditions. Do the boundaries between different kinds of ecosystems tend to be sharply delineated? Can you identify factors that limit the growth of certain species? 5. Organize a class field trip to systematically investigate the ecological niches for plant and animal life existing in a landscape significantly modified by human activities. If possible, arrange to travel along a gradient that will take you from farmland to suburbs to city to central business district. (A simplified version of this exercise could be done by walking around campus.) 6. Organize a local field trip for the class to examine recently disturbed areas for evidence of resilience. 7. As a class, investigate an invasion of a nonnative species in your community. Research the species and contribute to a plan to prevent its impact on natural ecosystems. 8. As a class, investigate hunting, trapping, and predator control issues in your community. Evaluate current regulations and management strategies. Make proposals for change that seem necessary and appropriate to you. 9. As a class exercise, systematically study a modern freeway or interstate highway and trace its impact on the surrounding land in terms of succession, diversity, and stability. Attitudes and Values 1. Has your local ecosystem been invaded by a nonnative species? If so, how did you feel about the invasion? Answer: Invasive nonnative species can significantly impact local ecosystems by outcompeting native species and disrupting ecological balance. Observing such invasions can be concerning as they often lead to reduced biodiversity and altered ecosystem functions. Efforts to manage and mitigate these impacts are essential to restore and protect the local environment. 2. How do you feel toward indicator species? Keystone species? Answer: Indicator species provide valuable insights into the health of an ecosystem, helping us understand environmental changes and potential issues. Keystone species are crucial for maintaining ecological balance, as their presence or absence can significantly affect the entire ecosystem. Both types of species are important for monitoring and conserving ecosystems. 3. Do you have any particular feelings toward relationships demonstrated in ecosystems? Competition? Predation? Commensalism? Parasitism? Mutualism? Answer: Ecosystem relationships such as competition, predation, commensalism, parasitism, and mutualism reflect the complexity and interdependence of life. Each relationship plays a role in maintaining ecological balance, and understanding these dynamics helps appreciate the intricate web of interactions that sustain ecosystems. 4. How do you feel when you observe grass emerging from a sidewalk or paved parking lot? Answer: Seeing grass emerging from a sidewalk or paved area can be a symbol of nature's resilience and the power of life to adapt and thrive even in challenging conditions. It often evokes a sense of wonder at nature's persistence and ability to reclaim and transform human-made environments. 5. How do you feel when you observe lichens growing on a bare rock? Answer: Lichens growing on bare rock demonstrate the ability of life to colonize and thrive in seemingly inhospitable environments. This can inspire a sense of admiration for nature's adaptability and the symbiotic relationships that allow such survival, highlighting the resilience and persistence of life forms. 6. How do you feel toward fire in natural ecosystems? Answer: Fire in natural ecosystems can be a natural and essential process that promotes ecological health, such as by encouraging new growth and maintaining species diversity. While it can be destructive, understanding its role in ecosystem dynamics can foster a balanced perspective on its benefits and management needs. 7. How do you feel toward mature ecosystems? Immature ecosystems? Answer: Mature ecosystems often reflect stability, biodiversity, and complex interactions that have developed over time, inspiring appreciation for their richness and resilience. Immature ecosystems, on the other hand, represent potential and the process of development, highlighting the dynamic nature of ecological succession and the importance of nurturing new growth. 8. How do you feel toward island ecosystems? Answer: Island ecosystems are fascinating due to their unique biodiversity and isolation, which can lead to distinct evolutionary processes. They can be both delicate and resilient, often requiring careful conservation efforts to maintain their unique species and ecological functions. Observing island ecosystems offers insight into the effects of isolation on biodiversity and the importance of protecting these special environments. News Videos Bald Eagle Soars Again: Taken Off Endangered Species List; Environmental Science in the Headlines, 2008, DVD ISBN: 0495561908 Monarch Watch: Researchers Track Migration of Butterflies; Environmental Science in the Headlines, 2008, DVD ISBN: 0495561908 Circle of Life; Environmental Science in the Headlines, 2008, DVD ISBN: 0495561908 How Exotic Species are Devastating Hawaii’s Native Fauna; The Brooks/Cole Environmental Science Video Library, 2009; DVD ISBN: 0538733551 Additional Video Resources Last Journey for the Leatherback A 30-minute film about sea turtle population decline and efforts toward its recovery. http://www.greentreks.org/naturalheroes/season2/lastjourney.asp Ocean Oasis (Documentary, San Diego Natural History Museum, 2001) Biodiversity in the Sea of Cortez, and the deserts of Baja, Mexico. http://www.oceanoasis.org/toc.html Web Resources Hare and Lynx Populations A complete lesson plan exploring the classic population control model. http://www.mysciencebox.org/book/export/html/81 Suggested Answers to End of Chapter Questions Review Questions 1. Review the Key Questions and Concepts for this chapter on p. 105 Explain how southern sea otters act as a key-stone species in their environment. Explain why we should care about protecting this species from premature extinction that could result mostly from human activities. Answer: • One reason is that people love to look at these charismatic, cute, and cuddly animals as they play in the water. As a result, they help to generate millions of dollars a year in tourism income in coastal areas where they are found. Another reason is ethical: Some people believe it is wrong to cause the premature extinction of any species. • A third reason to care about otters—and a key reason in our study of environmental science—is that biologists classify them as a keystone species. Without southern sea otters, scientists hypothesize that sea urchins and other kelp-eating species would probably destroy the kelp forests and much of the rich biodiversity associated with them. • In giant kelp forest ecosystems, sea urchins prey on kelp, a form of seaweed. However, as keystone species, southern sea otters prey on the sea urchins and thus keep them from destroying the kelp. • Biodiversity is an important part of the earth’s natural capital and is the focus of one of the three principles of sustainability. 2. Define interspecific competition, predation, parasitism, mutalism, and commensalism and give an example of each. Explain how each of these species interactions can affect the population sizes of species in ecosystems. Describe and give an example of resource partitioning and explain how it can increase species diversity. Answer: • Interspecific competition occurs when members of two or more species interact to gain access to the same limited resources such as food, water, light, and space. An example is moss and lichen. • Predation occurs when a member of one species (the predator) feeds directly on all or part of a member of another species (the prey). An example is lion to deer. • Parasitism occurs when one organism (the parasite) feeds on another organism (the host), usually by living on or in the host. An example is tick to human. • Mutualism is an interaction that benefits both species by providing each with food, shelter, or some other resource. An example is bee to flower. • Commensalism is an interaction that benefits one species but has little, if any, effect on the other. An example is epiphyte to tree. • These relationships help maintain a balanced ecosystem with shared resources. • Resource partitioning occurs when species competing for similar scarce resources evolve specialized traits that allow them to use shared resources at different times, in different ways, or in different places. Some insect-eating bird species reduce competition by feeding in different portions of certain spruce trees and by feeding on different insect species. Resource partitioning allows species to avoid niche overlap. 3. Distinguish between a predator and a prey species and give an example of each. What is a predator– prey relationship? Explain why we should help to preserve kelp forests. Describe three ways in which prey species can avoid their predators and three ways in which predators can increase their chances of feeding on their prey. Answer: • In predation, a member of one species (the predator) feeds directly on all or part of a living organism of another plant or animal species (the prey) as part of a food web. Together, the two different species—such as lions (the predator, or hunter) and zebras (the prey, or hunted)—form a predator-prey relationship. • We should conserve kelp forests because biodiversity is an important part of the earth’s natural capital and is the focus of one of the three principles of sustainability. • Some ways in which prey species can avoid their predators include camouflage, protective shells, chemical warfare and a highly developed sense of sight or smell that alerts them to the presence of predators. • Some ways that predators can increase their chances of feeding on their prey include camouflage, chemical warfare, ability to fly faster than the prey, and better vision. 4. Define and give an example of coevolution. Answer: • Coevolution occurs when populations of two different species interact in such a way over a long period of time; changes in the gene pool of one species can lead to changes in the gene pool of the other. Such changes can help both sides become more competitive, or avoid or reduce competition. An example is bees and flowers. 5. Describe four variables that govern changes in population size and write an equation showing how they interact. What is a population’s age structure and what are three major age groups called? Answer: • Four variables—births, deaths, immigration, and emigration—govern changes in population size. A population increases by birth and immigration (arrival of individuals from outside the population) and decreases by death and emigration (departure of individuals from the population): Population change = (births + immigration) – (deaths + emigration). • Age structure refers to the number or percentage of males and females in young, middle, and older age groups. A diagram of the age structure of the human population might show the percentages of males and females in the total population in age categories: pre-reproductive (ages 0–14); reproductive (ages 15–44); and post-reproductive (age 45 and older). 6. Distinguish between the environmental resistance and the carrying capacity of an environment, and use these concepts to explain why there are always limits to population growth in nature. Why are southern sea otters making a slow comeback and what factors can threaten this recovery? Answer: • Environmental resistance is the combination of all factors that act to limit the growth of a population. It largely determines a population’s carrying capacity: the maximum population of a given species that a particular habitat can sustain indefinitely. The growth rate of a population decreases as its size nears the carrying capacity of its environment because resources such as food, water, and space begin to dwindle. • The southern sea otter cannot rapidly increase its numbers for several reasons. Female southern sea otters reach sexual maturity between 2 and 5 years of age, can reproduce until age 15, and typically each produce only one pup a year. The population size of southern sea otters has fluctuated in response to changes in environmental conditions. One such change has been a rise in populations of orcas (killer whales), which feed on them. Scientists hypothesize that orcas began feeding more on southern sea otters when populations of their normal prey, sea lions and seals, began declining. 7. Define and give an example of a population crash. Explain why humans are not exempt from nature’s population controls. Describe the exploding white-tailed deer population problem in the United States and discuss options for dealing with it. Describe two different reproductive strategies that can enhance the long-term survival of a species. Define population density and explain how it can affect the size of some but not all populations. Answer: • A population may suffer a dieback, or population crash, if it uses up its resource supplies and temporarily overshoots, or exceeds, the carrying capacity of the environment. The reindeer population crashed when they were introduced onto a small island in the Bering Sea. • Humans are not exempt from population crashes when they have used up their resources, as seen with the Irish potato famine. • There are 25– 30 million white- tailed deer in the United States. Laws to protect deer have restricted hunting and natural predators such as wolves and mountain lions have been nearly eliminated. During the last 50 years, large numbers of Americans have moved into the wooded habitat of deer and provided them with flowers, garden crops, and other plants they like to eat. In some forests, they are consuming native ground cover vegetation and allowing nonnative weed species to take over. Deer also spread Lyme disease to humans. Each year there are 1.5 million deer– vehicle collisions which injure at least 14,000 people and kill at least 200. • Options for dealing with the deer overpopulation include ○ Changing hunting regulations to allow killing of more female deer. Since it is too dangerous to allow widespread hunting with guns in populated communities, hire licensed archers who use bows and arrows to help reduce deer numbers. However, animal activists argue that this is cruel and inhumane treatment. ○ Scare off deer by spraying the scent of deer predators or rotting deer meat or using electronic equipment that emits high-frequency sounds, which humans cannot hear. ○ Surround their gardens with high fencing. Such deterrents may protect one area, but cause the deer to seek food in someone else’s yard or garden. ○ Deer can be trapped and moved from one area to another. This is expensive and must be repeated whenever deer move back into an area. ○ Put deer on birth control by shooting females with darts loaded with a contraceptive. • Some species have many, usually small, offspring and give them little or no parental care or protection. At the other extreme are species that tend to reproduce later in life and have a small number of offspring with fairly long life spans. • Population density is the number of individuals in a population found in a particular area or volume. Density-dependent factors tend to regulate a population, keeping it at a fairly constant size, often near the carrying capacity of its environment. 8. What is ecological succession? Distinguish between primary ecological succession and secondary ecological succession and give an example of each. Explain why succession does not follow a predictable path. Answer: • The gradual change in species composition in a given area is called ecological succession. • Primary succession involves the gradual establishment of biotic communities in lifeless areas where there is no soil in a terrestrial ecosystem or no bottom sediment in an aquatic ecosystem. • Examples include bare rock exposed by a retreating glacier (Figure 5-10), newly cooled lava, an abandoned highway or parking lot, and a newly created shallow pond or reservoir. • Secondary succession occurs as a series of communities or ecosystems with different species develop in places containing soil or bottom sediment. This type of succession begins in an area where an ecosystem has been disturbed, removed, or destroyed, but some soil or bottom sediment remains. Candidates for secondary succession include abandoned farmland (Figure 5-11), burned or cut forests, heavily polluted streams, and land that has been flooded. • Succession does not follow a predictable path because there are many unique variables, such as weather and available nutrients. 9. Explain how living systems achieve some degree of sustainability by undergoing constant change in response to changing environmental conditions. In terms of stability, distinguish between inertia (persistence) and resilience and give an example of each. Answer: • Living systems contain complex networks of positive and negative feedback loops that interact to provide some degree of stability, or sustainability. This stability, or capacity to withstand external stress and disturbance, is maintained only by constant change in response to changing environmental conditions. • There are two aspects of stability in living systems. One is inertia, or persistence: the ability of a living system, such as a grassland or a forest, to survive moderate disturbances, such as mild drought. A second factor is resilience: the ability of a living system to be restored through secondary succession after a moderate disturbance, such as a wildfire. 10. What are this chapter’s three big ideas? Explain how changes in the nature and size of populations are related to the three principles of sustainability. Answer: • The three big ideas are: ○ Certain interactions among species affect their use of resources and their population sizes. ○ There are always limits to population growth in nature. ○ Changes in environmental conditions cause communities and ecosystems to gradually alter their species composition and population sizes (ecological succession). • Population dynamics relate to the three principles of sustainability insofar as populations are a component of the biodiversity within an ecosystem, their role in an ecosystem involves the use of energy ultimately derived from the sun, and they are constantly involved in the cycling of nutrients. Critical Thinking The 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. 1. What difference would it make if the southern sea otter (Core Case Study) became prematurely extinct mostly because of human activities? What are three things we could do to help prevent the premature extinction of this species? Answer: The extinction of the sea otter would cause drastic changes to our ocean ecosystems, as the sea otter acts as a keystone species, controlling sea urchin populations that would otherwise decimate the highly productive kelp forests. Activities that might help prevent the demise of this species would be to join an organization that works on their behalf, as pollution is an issue for organisms in the near-shore environment. Of course, there should be opposition to any hunting or poaching of the species, and they could visit the regions where these organisms are found in order to broaden their appreciation. 2. Use the second law of thermodynamics (see chapter 2) to explain why predators are generally less abundant than their prey. Answer: Predators are generally found at higher trophic levels than their prey as they eat higher up the food chain. For example, a lion eats a zebra that feeds on grass. The lion, a carnivore and secondary consumer, is at the third trophic level; the zebra, an herbivore and primary consumer, is at the second trophic level; and the grass, a producer, is at the first trophic level. There is less energy and biomass when going from lower to higher trophic levels. This follows the second law of thermodynamics as some energy is degraded and lost as heat at each energy conversion from one trophic level to the next. Generally, there is a 90% loss of usable chemical energy that is transferred as biomass from one trophic level to another; this is referred to as ecological efficiency. As a result, large numbers of predators (or large amounts of biomass) cannot occur at the end of a food chain, so the number of predators will be less than the numbers of their prey. 3. Explain why most species with a high capacity for population growth (such as bacteria, flies, and cockroaches) tend to have small individuals, while those with a low capacity for population growth (such as humans, elephants, and whales) tend to have large individuals). Answer: Species with a high biotic potential tend to be born small and have minimal time and energy to invest into growth and development before reproduction begins. Species with fewer offspring tend to give birth to few large slowly-maturing individuals. These then grow large in order to better compete for resources. 4. Which reproductive strategy do most insect pest species and harmful bacteria use? Why does this make it difficult for us to control their populations? Answer: Insects and bacteria tend to reproduce very rapidly, with their populations following the J-curve. It is difficult to control their populations, because when problems arise, it is generally because we have provided them with abundant resources. In the case of insect pests, populations rise rapidly to take advantage of the food source that our crops provide. 5. List three factors that have limited human population growth in the past that we have overcome. Describe how we overcame each of these factors. List two factors that may limit human population growth in the future. Do you think that we are close to reaching those limits? Explain. Answer: In the past, human populations have been limited by disease, limitations in food productivity, and limitations in terms of the landscape they could occupy. Factors that may continue to limit human populations in the future would be water limitation and diseases. 6. If the human species suffered a population crash, name three species that might move in to occupy our part of the niche. Answer: Any number of inventive answers might suffice, depending on how students interpret the role that humans play in their environment. Humans occupy a very broad niche, and when niches are vacated, often invasive species tend to take over. Student responses should highlight generalist and invasive species that may occupy the vacated human niche. If humans experienced a population crash, three species that might move in to occupy our ecological niche could be: 1. Rats - Highly adaptable and opportunistic. 2. Crows - Intelligent and versatile in urban environments. 3. Coyotes - Adaptable predators with a wide range. 7. How would you reply to someone who argues that we should not worry about our effects on natural systems because succession will heal the wounds of human activities and restore the balance of nature? Answer: Succession may be able to restore the balance of nature and heal some of the wounds that humans have inflicted, however succession takes place over hundreds or thousands of years and will not be able to take place at a fast enough rate to restore the imbalances that humans are causing in the short term. We do need to worry about human effects on natural systems. 8. How would you reply to someone who contends that efforts to preserve natural systems are not worthwhile because nature is largely unpredictable? Answer: Preservation efforts must look beyond the snapshot view of nature and embrace the notion that nature is in a constant state of flux. These efforts should be directed at allowing natural processes to continue with little disturbance from humans. 9. In your own words, restate this chapter’s closing quotation by Sir Francis Bacon. Do you agree with this notion? Why or why not? Answer: Sir Francis Bacon’s quote that “we cannot command nature except by obeying her,” ultimately points to the balance we find in ecosystems. Our efforts to alter these systems generally have unforeseen and far-reaching effects. Whether or not these effects should be of concern to us should be determined, with supporting arguments, by the students. 10. List two questions that you would like to have answered as a result of reading this chapter. Answer: 1. How would a sudden decline in human population affect the distribution and behavior of other urban-adapted species? 2. What long-term ecological impacts could arise from the emergence of new dominant species in human-dominated niches? Data Analysis The graph below shows the changes in size of an Emperor Penguin population in terms of breeding pairs on Terre Adelie in the Antarctic. Use the graph to answer the questions below. 1. What was the approximate carrying capacity of the penguin population on the island from 1960 to 1975? What was the approximate carrying capacity of the penguin population on the island from 1980 to 2000? 2. What is the percentage decline in the penguin population from 1975 to 2000? Answer: 1. The carrying capacity from 1960 to 1975 is approximately 5,500 emperor penguins. The carrying capacity from 1980 to 2000 is approximately 3,000 emperor penguins. 2. The population of emperor penguins on Terre Adelie has declined by about 45%. 5,500 – 3,000 = 2,500 drop in the number of penguins. 2,500/5,500 x 100 = 45% Chapter 6 The Human Population and Its Impact Summary 1. Birth, death, fertility, and migration rates are the factors that determine population size. As birth rates have declined in developed countries, population has increased due to people’s migrating into these countries. Women’s fertility rates have dropped but are still above the replacement-level fertility around the world. 2. Population size is profoundly affected by age structure. If women are past their primary child-bearing ages, population increase will be limited. If, however, the population has a large percentage of young women entering their childbearing years, the potential for large population increases is present. In general, the closer a country’s young women are to 15–40 years of age, the more potential for a rapidly increasing population. 3. We can influence population size by encouraging smaller families, by encouraging adoption of children already born and discouraging new births. Population size is, also, affected by health care or its lack; by epidemics (such as AIDS); by losses through war, etc. Lack of prenatal care for expectant mothers, failure to protect children from communicable diseases (like measles) or wide-spread diseases (like malaria), can contribute to a smaller population. In the past economic development, family planning, and economic opportunities for women have reduced birth rates. 4. India and China have both made efforts to control their population growth. China has been more successful because, as a dictatorship, it has imposed restrictions on family size with rewards and punishments for those who support or defy the government’s direction. India, without a policy of coercion, has reduced its birth rate; but the wish for male children and several children for the care of old parents has helped to maintain a growing population. 5. Effective methods for slowing the growth of world population include investing in family planning, reducing poverty, and elevating the status of women. Key Questions and Concepts 6-1 How many people can the earth support? CORE CASE STUDY: Beginning in the 1960’s China has taken an aggressive approach to slowing its population growth, by embracing a one child per family policy. The result has been a dramatically slowed population growth, yet China is still the world’s most populous country, with 1.3 billion people. Rapid industrialization since 1980 has led to an emerging middle class, which will increase per capita resource consumption and increase China’s ecological footprint. A. The human population has grown rapidly due to technology, improved medical techniques, emphasis on hygiene, and expansion of agriculture and industry. B. Population growth has slowed but is still growing exponentially. 1. The vast majority of all growth occurs in less-developed countries. C. In 2050 there will be 7.8-10.8 billion people on earth 1. Cultural carrying capacity is the maximum number of people that can live in reasonable freedom and comfort indefinitely without compromising the ability of earth to sustain future generations. SCIENCE FOCUS: Estimates of future population growth vary widely. Demographers must rely on available data in making these predictions. However, current population estimates may not be accurate and assumptions must be made about future fertility. In addition, population predictions are made by a variety of different organizations. SCIENCE FOCUS: Human activities have directly affected about 83% of the Earth’s land surface, excluding Antarctica. Humans have altered nature in eight major ways. They have reduced biodiversity, increased primary productivity, increased genetic resistance in pests, eliminated natural predators, introduced harmful species, used renewable resources unsustainably, interfered with chemical cycling and energy flow, and relied on fossil fuels. 6-2 What factors influence the size of the human population? A. Population increases through births and immigration and decreases through deaths and emigration. [Population change = (Births + Immigration) – (Deaths + Emigration)] 1. The crude birth rate is the number of live births per 1,000 people in a population in a specific year. 2. The crude death rate is the number of deaths per 1,000 people in a population in a specific year. 3. Population change is calculated by subtracting the number of people leaving a population (death and emigration) from the number entering it (birth and immigration). B. Fertility is the number of births that occur to an individual woman or in a population. 1. The changing nature of fertility rates affect population growth. a. Replacement-level fertility is the number of children needed to replace their parents. b. Total fertility rate (TFR) is the average number of children that a woman has during her fertile years. CASE STUDY: The population of the United States is currently 310 million people. Although a drop in TFR has slowed the country’s growth, it is still growing faster than any other developed country. Because of high per capita resource use and waste, growth in the population of the United States has an enormous environmental impact. C. Many factors influence birth and fertility rates. 1. More children work in developing countries; they are important to the labor force. 2. The economic cost of raising and educating children determines their numbers. 3. If there are available private/public pension systems, adults have fewer children because they don’t need children to take care of them in old age. 4. People in urban areas usually have better access to family planning, so have fewer children. 5. If women have educational and economic choices, they tend to have fewer children. 6. The older the age at which women marry, the fewer children they bear. 7. If abortions are available and legal, women have fewer children. 8. The availability of reliable birth control allows women to space children and determines the number of children they bear. D. Factors that have caused a decline in death rates are the following: 1. Better food supplies and nutrition, and safer water supplies contribute to people living longer. 2. Advances in medicine and public health, and improved sanitation and personal hygiene also contribute to people living longer. E. Measures of overall health are: 1. Life expectancy is the average number of years a newborn can expect to live. 2. Infant mortality rate is the number of babies out of every 1,000 born who die before their first birthday. a. This rate reflects a country’s level of nutrition and health care. b. It is the single best measure of a society’s quality of life. 3. U.S. infant mortality rate is higher than 40 other countries because: a. Inadequate health care for poor women and for their babies. b. Drug addiction among pregnant women. c. High birth rate among teenagers. F. Migration is also a factor in population change. CASE STUDY: Historically, the United States has admitted more immigrants than all other countries combined. Some 60% of the U.S. population supports limiting legal immigration. A recent study suggests that to maintain a viable workforce as baby boomers retire, the U.S. would have to absorb many more immigrants per year than it currently does. 6-3 How does a population’s age structure affect its growth or decline? Age structure diagrams are visual aids that show the distribution of males and females in each age group. A. The percentages of males and females in the total population are divided into the following age categories: 1. Pre-reproductive ages span birth to 14 years of age. 2. Reproductive ages include age 15 through 44. 3. Post-reproductive ages include ages 45 and up. B. The major determining factor in a country’s future population growth is the number of people under the age of 15. 1. In 2010, 27% of the planet’s population was under 15. CASE STUDY: Changes in the distribution of a country’s age groups have long-lasting economic and social impacts. An example of this is the ‘baby boom’ generation in the U.S. Such a group can dominate the population’s demands for goods and services as well as influence elections and legislation and economic demand. The graying of America may create economic problems for future generations. C. Population decline can have long-term consequences, especially if the decline is rapid. 1. A gradual population decline, its harmful effects can usually be managed. 2. There can be a sharp rise in the proportion of older people. a. Produces a sharp rise in public service costs, for health, etc. b. May have many fewer working taxpayers and labor shortages. c. It may be necessary to raise retirement age, raise taxes, cut retirement benefits, and increase legal immigration, which are generally unpopular moves. 3. If population declines because of deaths, consequences are serious. a. Deaths from disease such as AIDS disrupt a country’s social and economic structure. b. Large numbers of people in a particular age are removed from the country’s future. 1) Life expectancy drops. 2) In the case of AIDS, the deaths are mostly young adults, those who usually help run the country and everyday life for millions. 3) Two major goals are to reduce the spread of HIV through education and health care and to provide financial help for education, health care, and volunteer teachers and social workers to compensate for the lost young adults. 6-4 How can we slow human population growth? A. A precautionary approach is adopted to slow or stop population growth. The three most important steps are to: a. Reduce poverty b. Elevate the status of women c. Encourage family planning B. The demographic transition hypothesis states that as countries become industrialized, first their death rates rise and then their birth rates decline. a. Four stages: preindustrial, transitional, industrial, and postindustrial. b. Some failing states may be stuck in step 2. C. Women have fewer children when they are educated, in control of their fertility, earn an income, and live in societies that do not suppress their rights. D. Family planning helps reduce the number of births and abortions throughout the world. 1. Information is given on birth spacing, birth control, and health care. 2. Family planning has been responsible for at least 55% of the drop in TFRs in developing countries. 3. Family planning has also reduced both legal and illegal abortions per year. 4. Services come through educational and clinical services. a. 42% of pregnancies in developing countries are unplanned and 26% end in abortion. b. Women want to limit their pregnancies but have no access to contraceptives. CASE STUDY: India has tried to control its population growth for years. Poverty, malnutrition, and environmental problems abound in India. Efforts to limit population have not been especially successful because poor couples believe they need several children for work and care ,and there is a strong preference for male children so many do not use birth control. India is currently undergoing tremendous economic growth that will likely continue. This may increase the ecological footprint of the nation, but may also serve to hasten the demographic transition. Teaching Tips Large Lecture Courses: Begin with a discussion of the concept of the ecological footprint. Have your students take an online footprint quiz before coming to lecture. Ask them to share their scores by show of hands and tabulate them on the board. Then go through the questions that gave rise to those numbers, asking for classroom participation as a means of brainstorming why certain factors, like meat consumption or number of people per household, contribute greatly to the high ecological footprint common to the developed world. Ask for suggestions that might help diminish the magnitude of the footprint, and then brainstorm reasons why there is opposition to these changes. Smaller Lecture Courses: Have the students take the ecological footprint quiz before coming to class. Ask the students to get into groups of three to four and share their scores. Than ask them to brainstorm ways developed nations might diminish their footprint. Ask them to address the question: What is the greater culprit, population size, or lifestyle? Ask them to then address the implications of the majority of the world’s population living in regions that are said to be developing. What are the ultimate consequences of their future economic development? Key Terms age structure birth rate crude birth rate crude death rate cultural carrying capacity death rate demographic transition family planning fertility rate infant mortality rate life expectancy migration population change replacement-level fertility total fertility rate (TFR) Term Paper Research Topics 1. Population growth: a case study of Mexico, China, India, Kenya, Japan; the geography of global population distribution; infant mortality trends and issues; illegal immigration into the United States; marriage age trends; fertility trends and the women's rights movement; factors influencing family size preferences; Earth's carrying capacity; family planning. 2. Population growth in the United States: economics of fertility control technology in the United States, economic costs of childrearing in the United States, new birth control methods, teenage pregnancy in the United States. 3. Influencing population size: case studies of India, China, Japan, Thailand. 4. Demographic transition: past, present, and future. 5. Environmental impacts of population: air pollution in urban areas; land degradation from urban sprawl; deforestation and desertification in developing countries. 6. Individual: decisions individuals make about family size and urban conditions and ways individuals can influence government agencies and non-government institutions concerned with population. 7. National: Zero Population Growth during the 1980s, ZPG analysis of the U.S. way of taxing. 8. Global: the UN International Conference on Population; UN Family Planning Association; International Planned Parenthood Federation. Discussion Topics 1. Do you think the United States needs a population policy? Should the federal government stop subsidizing large families? Answer: A population policy could address challenges related to resource management, environmental sustainability, and economic growth. However, the approach should be nuanced, considering the ethical implications of limiting family size or altering subsidies. Rather than stopping subsidies outright, a balanced policy could support diverse family structures while promoting sustainable practices and resource use. 2. Evaluate U.S. immigration policy. Answer: U.S. immigration policy is complex, with ongoing debates about border security, visa processes, and pathways to citizenship. While it aims to balance economic needs, security concerns, and humanitarian responsibilities, there are criticisms regarding its effectiveness and fairness. Reforming the policy to address these concerns while promoting integration and human rights could improve the system's overall efficacy. 3. Do you think the United States should play a global leadership role in promoting stabilization of the world's human population? Answer: Yes, the U.S. could leverage its influence to support global efforts in stabilizing human populations through sustainable development, education, and family planning programs. Leading by example and investing in international partnerships can help address demographic challenges and promote global stability, but it should be done with sensitivity to local contexts and needs. 4. Would you rather be a baby boomer or a baby buster? Answer: Choosing between being a baby boomer or a baby buster depends on one's perspective on historical and societal contexts. Baby boomers experienced post-war economic growth and social change, while baby busters faced economic challenges and shifts in societal norms. Each generation has its unique experiences and challenges, and personal preference might depend on the values and opportunities one prioritizes. Activities and Projects 1. Invite a public health official or nutritionist to your class to explain the factors involved in the decline in the global death rate over the past century and the decline in the infant mortality rate in the United States. Why is the latter rate higher in the United States than in many other developed nations? 2. U.S. immigration policy had become a volatile political issue by the 1980s. Arrange a debate on this subject. Debate the proposition that the United States should enact and strictly enforce legislation that holds legal immigration to levels consistent with the achievement of ZPG within a few generations. 3. Ask your students to share with the class poems, short stories, songs, paintings, collages, photographic displays, slide talks, or other works expressing their feelings about population issues and problems. 4. Are there family-planning clinics in your community that provide contraceptives and birth control counseling? Invite a family-planning worker to visit your class and discuss different aspects of family planning. 5. Ask students to work with dynamic computer simulations (such as the Forrester-Meadows model). Analyze the sensitivity of the model to initial assumptions (optimistic versus pessimistic). 6. Survey the marriage and childbearing intentions of your female students. Find out at what age students' mothers married and the number of children each had. Tally the results and compare them with recent trends in marriage age and total fertility. 7. Survey your students to obtain age- or life-span information about their grandparents. Compare the results with the average life expectancy in the United States in the year 1900 (46 for men and 48 for women). Invite your students to discuss major implications of these findings. 8. As a class project, study print and broadcast advertising to determine whether small families are directly or indirectly encouraged as the ideal model for U.S. society. Compare and contrast the results with those obtained through a similar analysis of magazine advertising in the 1940s and 1950s. 9. Have your students analyze the political platforms of the major political parties in the United States. What positions do they take on the birth of American children and birth control? What positions do they take on the influence of the United States in global population growth patterns? To what extent does debate on population policy revolve around right to life, desired pregnancies, and quality of life for the children who are born? Attitudes and Values 1. Do you feel the size of the human population is an important environmental issue? Answer: Yes, the size of the human population is a significant environmental issue because it impacts resource consumption, habitat destruction, and pollution levels. A growing population can strain ecosystems and lead to greater environmental challenges, making it crucial to address sustainable practices and resource management. 2. Do you feel consumption by the human population is an important environmental issue? Answer: Yes, consumption is a critical environmental issue, as it drives the demand for resources, energy, and produces waste and emissions. High levels of consumption can lead to overexploitation of natural resources and increased environmental degradation, underscoring the need for sustainable consumption practices. 3. Do you feel that humans have the right to have as many children as they want? Are there any limits on this right? If so, what are they? Answer: While individuals have the right to family planning, there are practical and ethical limits to consider, such as environmental sustainability and resource availability. Balancing personal rights with broader societal impacts is important, and promoting access to education and family planning can help manage population growth responsibly. 4. Do you feel that there should be a national population policy? What steps would you support? Answer: A national population policy could help address challenges related to resource management and environmental sustainability. Steps might include promoting education on family planning, supporting sustainable practices, and implementing policies that encourage responsible resource use while respecting individual rights. 5. Do you feel that teen pregnancy is a problem? Answer: Teen pregnancy can be a significant issue, often associated with challenges such as limited educational and economic opportunities for young parents and potential health risks. Addressing this issue through education, access to contraception, and support services can help reduce rates and improve outcomes for both parents and children. 6. Do you feel that women's roles are important in addressing population size? Answer: Yes, women's roles are crucial in addressing population size. Empowering women through education, access to reproductive health services, and economic opportunities can lead to informed family planning decisions and contribute to more sustainable population growth. 7. What are your feelings toward birth control? Population control? Answer: Birth control is an important tool for empowering individuals to make informed choices about family planning and reproductive health. Population control measures should focus on voluntary, respectful approaches that support sustainable development and personal choice rather than coercion. 8. Do you feel that the earth will be able to sustain the projected increases in human population growth? Answer: The Earth's ability to sustain projected population growth depends on advancements in technology, resource management, and changes in consumption patterns. Sustainable practices, innovations in agriculture and energy, and effective resource management are crucial to meeting future needs and maintaining ecological balance. Additional Video Resources The End of Suburbia: Oil Depletion and the Collapse of the America Dream (2004) This documentary explores the relation between ecological footprint and lifestyle in the developed world, with strong reference to diminishing oil reserves. The Habitable Planet: A Systems Approach to Environmental Science: Human Population Dynamics (Documentary series, 2007). The fifth video in this series explores human population growth. http://www.learner.org/resources/series209.html National Geographic: Human Footprint (DVD, 2008). This documentary offers a glimpse at the impact the human population has. Web Resources Population Action International This website contains a variety for resources, including a list of relevant documentaries. http://www.populationaction.org/Publications/Documentaries/Index.shtml Population Connection This website includes a wealth of information, including the succinct “fact sheets” that are useful for assignments and discussions. http://www.populationconnection.org/ Suggested Answers for End of Chapter Questions Review Questions 1. Review the Key Questions and Concepts in this chapter on p. 126. Summarize the story of population growth in China and the Chinese government’s efforts to regulate it (Core Case Study). Answer: • In the 1960’s, China’s population was growing so rapidly that there was a threat of mass starvation. China then began to promote on-child families as a means of reducing population growth. The results have been dramatic. China has reduced its birth rate as well as the average number of children per family. 2. List three factors that account for the rapid growth of the world’s human population over the past 200 years. About how many people are added to the world’s population each year? Explain how this growth is unevenly distributed. What five countries had the largest numbers of people in 2010? How many of us are likely to be on the planet in 2050? What are demographers? Give three reasons why it is difficult for them to project population changes. Answer: • Increase in population: ○ Humans developed the ability to expand into almost all of the planet’s climate zones and habitats; the emergence of early and modern agriculture allowed us to grow more food on the same land. ○ Death rates dropped sharply because of improved sanitation and health care; antibiotics and vaccines were developed to help control infectious diseases. • About 83 million people are added to the world’s population each year. • The majority of this growth occurs in less-developed countries. • The countries with the most people are China, India, The United States, Indonesia, and Brazil. • The median projection is 9.5 billion people on earth in 2050. • Demographers are experts that analyze and make predictions about populations. • Demographers must deal with inaccurate population estimates, predict future fertility trends, and they all work for different organizations with differing access to reliable information. 3. What is the cultural carrying capacity? Describe the debate over whether and how long the human population can keep growing. Describe eight ways in which we have used technology to alter nature to meet our growing needs and wants. Answer: • Some analysts believe that we should ask what the optimum sustainable population of the earth might be, based on the planet’s cultural carrying capacity. This would be an optimum level that would allow most people to live in reasonable comfort and freedom without impairing the ability of the planet to sustain future generations. • The debate focuses on the expanding ecological footprint that the over-extraction of resources on the one hand; and on the other, the reliance on technology to solve out most insidious problems. • We have used technology to: ○ reduce biodiversity ○ increase the net use of primary productivity ○ increasing genetic resistance to pests ○ eliminating natural predators ○ introducing species that are harmful to a local community ○ using renewable resources faster than they can be replenished ○ disrupting chemical cycling and energy flow ○ relying on fossil fuels 4. Distinguish between crude birth rate and crude death rate. List four variables that affect the population change of an area and write an equation showing how they are related. Answer: • The crude birth rate is the number of live births per 1,000 people in a population in a given year. The crude death rate is the number of deaths per 1,000 people in a population in a given year. • Population change = (births + immigration) - (deaths + emigration) 5. What is fertility rate? Distinguish between replacement-level fertility rate and total fertility rate (TFR). Explain why reaching the replacement-level fertility rate will not stop global population growth until about 50 years have passed (assuming that death rates do not rise). Describe what has happened since 1950 to total fertility rates in the world, in China, and in the United States. Answer: • Fertility rate is the number of children born to a woman during her lifetime. • Replacement-level fertility rate is the average number of children that couples in a population must bear to replace themselves. • TFR is the average number of children born to women in a population during their reproductive years. • Reaching replacement-level fertility does not bring an immediate halt to population growth because so many future parents are alive. If all of today’s girl children have 2.1 children, the world’s population will continue to grow for 50 years or more (assuming death rates do not rise). • Between 1955 and 2010, the average TFR dropped from 2.8 to 1.6 children per woman in more-developed countries and from 6.2 to 2.8 in less-developed countries. Because of China’s strict one-child population policy, the country’s total fertility rate dropped from 5.7 to 1.6 between 1972 and 2009. At the peak of the United States’ baby boom in 1957, the average TFR was 3.7 children per woman. In 2010, and in most years since 1972, it has been at or below 2.1 children per woman. 6. Describe population growth in the United States and explain why it is high compared to those of most other more-developed countries and China. Is the United States over-populated? Explain. Answer: • The population of the United States grew from 76 million in 1900 to 306 million in 2009, despite oscillations in the country’s TFR and birth rates. The U.S. has high and irregular immigration rates and less direct government population control. • According to U. S. Census Bureau, the U. S. population is likely to increase from 304 million in 2008 to 438 million by 2050 and then to 571 million by 2100. In contrast, population growth has slowed in other major developed countries since 1950, most of which are expected to have declining populations after 2010. Because of a high per capita rate of resource use and the resulting waste and pollution, each addition to the U. S. population has an enormous environmental impact. 7. List ten factors that can affect the birth rate and fertility rate of a country. Explain why there is a bride shortage in China. Define life expectancy and infant mortality rate and explain how they affect the population size of a country. Why does the United States have a lower life expectancy and higher infant mortality rate than a number of other countries? What is migration? Describe immigration into the United States and the issues it raises. Answer: • Birth rates are affected by: ○ Importance of children as a part of the labor force ○ Cost of raising and educating children ○ Availability or lack of private and public pension systems ○ Urbanization ○ Educational and employment opportunities available for women ○ Infant mortality rate ○ Average age at marriage ○ Availability of legal abortions ○ Availability of reliable birth control methods ○ Religious beliefs, traditions, and cultural norms • In China, there is a strong preference for male children. • Life expectancy is the average number of years a newborn infant can expect to live, and the infant mortality rate is the number of babies out of every 1,000 born who die before their first birthday. A longer life expectancy and a lower infant mortality will increase population. • The U.S. lower life expectancy may be due to more than 45 million Americans lacking health care insurance, while Canada and many European countries have universal health care; also, adults in the United States have one of the world’s highest obesity rates. Three factors helped to keep the U.S. infant mortality rate higher than it could be: inadequate health care for poor women during pregnancy and for their babies after birth, drug addiction among pregnant women, and a high birth rate among teenagers. • Migration is the movement of people into (immigration) and out of (emigration) specific geographic areas. • Since 1820, the United States has admitted almost twice as many immigrants and refugees as all other countries combined. Currently, legal and illegal immigration account for about 40% of the country’s annual population growth. This raises a number of issues: ○ Many in the U.S. believe that legal immigration to the United States should be reduced because providing legal immigrants with public services makes the U.S. a magnet for the world’s poor. ○ Some argue that reducing legal immigration would diminish the historical role of the United States as a place of opportunity for the world’s poor and oppressed and as a source of cultural diversity that is a hallmark of American culture. ○ Studies show that immigrants and their descendants are beneficial to society; they pay taxes, take low- paying jobs that most other Americans shun, start new businesses, create jobs, add cultural vitality, and help the United States succeed in the global economy. Statistics show that after 2020, higher immigration levels will be needed to supply enough workers as baby boomers retire. ○ There is also intense political controversy over what to do about illegal immigration. 8. What is the age structure of a population? Explain how it affects population growth and economic growth. Describe the American Baby Boom and some of the effects it has had on American culture. What are some problems related to rapid population decline due to an aging population? How has the AIDS epidemic affected that age structure of some countries in Africa? Answer: • Age structure refers to the number or percentage of males and females in young, middle, and older age groups. Diagram of percentages of males and females in the total population in age categories: pre-reproductive (ages 0–14); reproductive (ages 15–44); and post reproductive (age 45 and older). • The American baby boom added 79 million people to the U.S. population. For decades, members of the baby-boom generation have strongly influenced the U.S. economy because they make up about 36% of all adult Americans. In 1960, one in 11 Americans were older than 65. After 2011, when the first baby boomers began turning 65, the number of Americans older than age 65 will grow sharply through 2030 when they will be one of every five people in the country. • Population has the potential to increase if a large percentage falls in the pre-reproductive and reproductive categories and decrease if a large percentage falls in the post-reproductive age. Economic growth may be predicted based on how many individuals are in a group that would be working and spending money. • Rapid population declines from an aging population may cause a lack of support services such as health care. • A large number of deaths from AIDS can disrupt a country’s social and economic structure by removing significant numbers of young adults from its population. Another effect of the AIDS pandemic is the loss of productive young adult workers and trained personnel such as scientists, farmers, engineers, and teachers, as well as government, business, and health-care workers. 9. What is the demographic transition and what are its four stages? What factors could hinder some developing countries from making this transition? What is family planning? Describe the roles of reducing poverty, elevating the status of women, and family planning in slowing population growth. Describe India’s efforts to control their population growth. Answer: • The demographic transition is a hypothesis explaining population change that occurs as countries become industrialized and their populations tend to grow more slowly. As countries become industrialized, first their death rates and then their birth rates decline. The four stages of this transition are: ○ Preindustrial ○ Transitional ○ Industrial ○ Postindustrial • Factors that can hinder countries from making the demographic transition include: ○ Rapid population growth ○ Extreme poverty ○ Increasing environmental gradation • Family planning includes educational and clinical services that help couples choose how many children to have and when to have them. • Many women in the developing world are trapped in poverty by illiteracy, poor health, and unwanted high fertility. Reducing poverty can alleviate these problems. • In general, as women are empowered the population decreases. Studies show that women tend to have fewer children if they are educated, hold a paying job outside the home, and live in societies where their human rights are not suppressed. • For more than 5 decades, India has tried to control its population growth with only modest success. The world’s first national family planning program began in India in 1952, when its population was nearly 400 mil-lion. By 2010, after 58 years of population control efforts, India had 1.2 billion people. 10. What are this chapter’s three big ideas? Describe the relationship between human population growth, as exemplified in China, and the three principles of sustainability. Answer: • Three big ideas: ○ The human population is increasing rapidly and may soon bump up against environmental limits. ○ Even if population growth were not a serious problem, the increasing use of resources per person is expanding the overall human ecological footprint and putting a strain on the earth’s resources. ○ We can slow human population growth by reducing poverty through economic development, elevating the status of women, and encouraging family planning. • Human population growth relates to the three principles of sustainability because as the human population has grown, it has had detrimental effects on biodiversity, has generated pollution by ignoring natural chemical cycling, and has been fueled by fossil energy, rather than solar power. Critical Thinking The 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. 1. Do you think that the problems resulting from China’s one-child policy (Core Case Study) outweigh the problems of overpopulation that likely would have resulted without some sort of population growth regulation? Can you think of other ways in which China could try to regulate its population growth? Explain. Answer: If China had not taken the approach that they did, the burden of the population that would have developed on the earth’s natural capital would have been dramatic, with global ramifications. Similarly, starvation and other inhumane conditions would likely have resulted. Other ways that China may have regulated its population could have focused on social justice, education, and economic development. 2. If you could greet a new person every second without taking a break, how many people could you greet in one day? How many in a year? How many in a lifetime of 80 years? How long would you have to live to greet (a) all 6.9 billion people on earth at a rate of one every second working around the clock and (b) the 83 million people added to the world’s population this year? Answer: 1 person x 60 seconds x 60 minutes x 24 hours = 86,400 people 86,400 people x 365 days = 31,536,000 people 31,536,000 people x 80 years = 2,522,880,000 people a. 6,900,000,000people/31,536,000 people per year = 218.8 years b. 83,000,000 people/31,536,000 people per year = 2.6 years 3. Which of the three major environmental worldviews summarized on pp. 24-25 do you believe underlie the two major positions on whether the world is overpopulated (Science Focus, p. 128)? Answer: The planetary management worldview, which sees no problem with the current population of the earth, and the environmental wisdom worldview, which is supported by the group that suggests introducing measures of population control. 4. Identify a major local, national, or global environmental problem, and describe the role population growth plays in this problem. Answer: Overfishing is a major environmental problem in our area. As the population increased, the demand for seafood as a means of providing a form of healthy protein to our diets also increased led to a non-sustainable situation. Many types of fish and shellfish are being harvested beyond the maximum sustainable yield. This has resulted in dwindling fish stocks and closure of some local fishing areas. This is also a problem in developing countries where coastal communities are often dependent on fish as a food source and revenue for the local economy. 5. Is it rational for a poor couple in a developing country such as India to have four or five children? Explain. Answer: It is rational for people living in places like India to have four or five children. This is because they are seen as part of the labor force and will provide old-age security for their parents as the parent’s age. Many live in rural areas and may not have easy access to doctors or family planning advisors. In some parts of India there is a high infant mortality rate, which leads to the desire to have more children. Also, religion, cultural norms, traditions, beliefs, and other factors may lead to avoiding birth control and to having children until one or more male child is born. There are a number of things that could help change this pattern including: education of women, free access to birth control, introducing government pension funds, improving health care to decrease infant mortality, and offering free vasectomies and tubal ligations. 6. Do you believe that the population is too high in: (a) China (Core Case Study), (b) the world (c) your own country, and (d) the area where you live? Explain. Answer: (a) The population of China is too high simply because economic development is providing the opportunity for a large portion of this population to expand its ecological footprint. (b) The population of the world is too high. We do not know the carrying capacity for humans on the planet. With all of the environmental degradation that is taking place and the overconsumption of many of the world’s resources, the population of the world is already too high. (c) The population of my own country, America, is around 300 million. This is not a high population density when the size of the country is taken into account, but the majority of people tend to be located in highly populated areas, which leads to overcrowding and congestion. Also, our relative percentage of the earth’s population (<5%) is not proportional to our share of the world’s resource consumption. Our ecological footprint is excessive. So although we may not appear to be overcrowded overall, many would suggest that we appear to be rather greedy in our needs. (d) I live in the countryside where the population is spread out and the population density is fairly low. This means we have a less stressful lifestyle than some people who live in cities, like Los Angeles, and have to drive for many hours to and from work. I do not want any more people to move to my area, as I like it as it is and do not want it to get built up. 7. Should everyone have the right to have as many children as they want? Explain. Is your belief on this issue consistent with your environmental worldview? Answer: In a free democratic society people have certain inalienable rights to be able to make choices that affect many aspects of their lives. Many people would suggest that everyone has the right to have as many children as they want. However, in a free society people also have the right to have as few children as they want. Everyone should be able to have control over the choices they make and at the same time be provided with an education in a factual and unbiased way to make the best choices for themselves and the planet. The ultimate ideal would be to aspire to zero population growth with a fertility rate at replacement level, or in some cases below that. 8. Some people believe the most important environmental goal is to sharply reduce the rate of population growth in less-developed countries, where at least 92 % of the world’s population growth is expected to occur. Others argue that the most serious environmental problems stem from high levels of resource consumption per person in more-developed countries, which use 88% of the world’s resources and have much larger ecological footprints per person than the less-developed countries do. What is your view on this issue? Explain. Answer:It would need both things to occur simultaneously in order for the effects to be successful in the long term. People in developing countries need to sharply reduce their rate of population growth (maybe through education/access to family planning, etc.). Increasing numbers in developing countries will result in increased consumption of ever-dwindling resources. At the same time people in the developed world need to take stock of their over-consumptive lifestyles and make changes to help combat “affluenza” and reduce their ecological footprint. People in developed countries cannot expect the developing countries to take action if they are not prepared to act themselves. 9. Congratulations! You are in charge of the world. Write a summary of your population policy. In the summary, consider the following: will you enact a program to regulate population growth? In not, explain your reasoning. If so, describe the program and how you will enact and fund it. Answer: Three important features of a population policy would be: education and empowerment of women; availability to free birth control methods, family planning, and neo-natal/post-natal care; and expanded job opportunities that would help alleviate and offset poverty. Funding could come from a carbon tax that assesses the ecological footprint of each family, and charges larger families with greater footprints accordingly. 10. List two questions that you would like to have answered as a result of reading this chapter. Answer: 1. How can brands adapt their messaging in new geographical markets? 2. What are the challenges in managing brand equity across different segments? Ecological Footprint Analysis The chart below shows selected population data for two different countries A and B. Country A Country B Population (millions) 144 82 Crude birth rate (cbr) 43 8 Crude death rate (cdr) 18 10 Infant mortality rate 100 3.8 Total fertility rate 5.9 1.3 % of population under 15 years old 45 14 % of population older than 65 years 3.0 19 Average life expectancy at birth 47 79 % urban 44 75 (Data from Population Reference Bureau 2007. World Population Data Sheet) Questions 1. Calculate the rates of natural increase (due to births and deaths, not counting immigration) for the populations of Country A and Country B. Based on these calculations and the data in the table, suggest whether A and B are developed or developing countries, and explain the reasons for your answers. 2. Describe where each of the two countries may be in terms of their stage in the demographic transition (Figure 6-17). Discuss factors that could hinder Country A from progressing to later stages in the demographic transition. 3. Explain how the percentage of people under 15 years of age in country A and country B could affect the per capita and total ecological footprints of each country. Question 1 Answer: Country A is most likely to be a developing country as it has the following characteristics indicative of a developing country: higher birth and death rates; higher infant mortality; higher total fertility rate; higher percentage of population under 15 years old; smaller percentage of population over 65 years old; lower life expectancy; smaller urban population; higher percentage of the population living with HIV/AIDS; higher rate of natural increase. (Country A is actually Nigeria) Country B is most likely a developed country as it has the following characteristics indicative of a developed country: lower birth and death rates; lower infant mortality; lower total fertility rate; lower percentage of population under 15 years old; higher percentage of population over 65 years old; higher life expectancy; larger urban population; lower percentage of the population living with HIV/AIDS; lower rate of natural increase (in fact it is undergoing a natural decrease). (Country B is actually Germany) Question 2 Answer: Country A is probably in stage 2 or the transitional phase of the demographic transition. Birth rates are still high and the death rates are lower. Country B is probably in stage 4 or the postindustrial phase of the demographic transition. Birth rates and death rates are both low; in fact, the birth rate is lower than the death rate in Country B. Country A is probably about halfway along the path to economic development, and still has a fairly high population growth rate. There is concern and disagreement among the experts as to whether such a country may be able to progress smoothly through the industrial and postindustrial phases. One group feels that advances in technology and expanded birth control initiatives will allow such a transition to occur. Others feel that the continuing rapid rate of population growth and the population momentum that will occur may counteract any economic benefits and lead to overconsumption and further collapse of local ecosystems that are needed to provide food, water, and other necessities for life. Country A may end up trapped in stage 2 or even fall back into stage 1 depending on the impact of the HIV/AIDS epidemic. Due to the population structure there may also be a shortage of a skilled workforce, little opportunity for economic growth, and an increasing national debt which will all hinder the progression of Country A into the third and later stages of the demographic transition. Question 3 Answer: In Country A the large number under 15 can have many negative effects on the country as a whole. Not all of these individuals will be able to find jobs when they try to enter the workforce and many may not be able to provide for themselves. Poverty rates are likely to increase. Hunger and malnutrition would become a problem for many people in this large population as land is degraded by overgrazing or overuse for raising food. Water use issues will get worse. Much of the country’s environment can become degraded and exhausted as the country tries to meet the needs of this large percentage of its population. Social unrest could increase making this sector of society prime recruits for radical groups. Turmoil or even war could ensue leading to further overuse of limited resources, environmental degradation, and a larger the ecological footprint. Whenever the economic growth of a country is threatened through increased poverty, the overall footprint of the country is at risk as potentially renewable resources such as soil and water become degraded. Country B has a lower percentage of young people. However, this group can still have a profound effect on the ecological footprint of the country because they live in an affluent country with a high resource use per person. Thus, as these young people move into adulthood they could have a much larger ecological footprint per person than the average footprint per person for the much larger group of young people in country A. This could lead to a larger overall ecological footprint for country B than for country A. Solution Manual for Living in the Environment: Principles, Connections, and Solutions G. Tyler Miller, Scott Spoolman 9780538735346