Chapter 19 Population Ecology.

Chapter 19 Population Ecology

Biology and Society: Multiplying Like Rabbits
In 1859, 12 pairs of European rabbits were released on a ranch in southern Australia. By 1865, 20,000 rabbits were killed on just that one ranch. By 1900, several hundred million rabbits were distributed over most of the continent. The European rabbits Destroyed farming and grazing land Promoted soil erosion Made grazing treacherous for cattle and sheep Competed directly with native marsupials © 2010 Pearson Education, Inc.

Figure Rabbit plague Figure 19.00

The European red fox Was introduced to control the rabbits Spread across Australia Ate several species of native birds and small mammals to extinction Had little impact on the rabbit population Today, rabbits, foxes, and a long list of other non-native animal and plant species are Still entrenched in Australia Damaging the environment Costing hundreds of millions of dollars in economic losses

AN OVERVIEW OF POPULATION ECOLOGY
A population is a group of individuals of a single species that occupy the same general area. Population ecology is the study of factors that affect population: Density Structure Size Growth rate Population ecology is used to study How to develop sustainable fisheries How to control pests and pathogens Human population growth Student Misconceptions and Concerns 1. Students might imagine that the opportunistic life history is risky and might not be successful over time. Plants such as the agave (century plant) risk all of their reproductive effort on a single life-ending event. However, this reproductive strategy has evolved over time because it has been successful (but like investments, past success does not guarantee future success). 2. Many nonmajors have trouble thinking about the evolution of systems. One analogy that can be developed, especially for economically minded students, makes parallels to the “evolution” of businesses. Consider the introduction and expansion of McDonald’s restaurants in the United States over the last 50 years. When McDonald’s restaurants were just starting out, they experienced little competition with access to many customers. The population of McDonald’s grew exponentially (or so it seemed!) with few density-dependent factors. Today in the United States, McDonald’s restaurants experience competition with each other and many other fast-food restaurants such as Burger King and Taco Bell. The population of McDonald’s restaurants in the United States has somewhat leveled off because of this competition for customers, a density-dependent factor. A graph of the growth of McDonald’s restaurants in the United States would likely resemble the lazy S shape. Teaching Tips 1. Consider comparing opportunistic and equilibrial life histories in a table with the following top headings: Type of Survivorship Curve, Age of Maturity, Number of Offspring, Use of Parental Care, Stability of the Population, Is the Population Density Dependent?, and Examples. 2. Your class might get some practice analyzing life histories by describing additional examples. Challenge your students to classify the type of survivorship curve that would be expected. Frogs and fish typically produce hundreds of eggs, leading to type III survivorship curves. Elephants and whales typically produce few offspring in life histories that more likely represent type I survivorship curves. Mice and other small mammals are capable of producing litters of 10 or more offspring a year, over a several year period. These mammals have life histories that may be intermediate, leading to type II survivorship curves. 3. The following Center for Disease Control web site provides information and life tables for people living in the United States. ( 4. Compromise is a key lesson in biology. No adaptation can be perfect, no reproductive strategy can maximize all types of efforts. As the text notes, an organism cannot have many offspring and great amounts of parental care. Resources, including time, are limited. Have students imagine how their life as parents would change with the birth of quadruplet children.

Figure 19.1 An ecologist styding a population of black-browed albatross in the Falkland Islands, east of the tip of South America Figure 19.1

Population Density Population density is the number of individuals of a species per unit of area or volume. Examples include The number of largemouth bass per cubic kilometer (km3) of a lake The number of oak trees per square kilometer (km2) in a forest The number of nematodes per cubic meter (m3) in a forest’s soil How do we measure population density? In most cases, it is impractical or impossible to count all individuals in a population. In some cases, population densities are estimated by indirect indicators, such as Number of bird nests Rodent burrows Student Misconceptions and Concerns 1. Students might imagine that the opportunistic life history is risky and might not be successful over time. Plants such as the agave (century plant) risk all of their reproductive effort on a single life-ending event. However, this reproductive strategy has evolved over time because it has been successful (but like investments, past success does not guarantee future success). 2. Many nonmajors have trouble thinking about the evolution of systems. One analogy that can be developed, especially for economically minded students, makes parallels to the “evolution” of businesses. Consider the introduction and expansion of McDonald’s restaurants in the United States over the last 50 years. When McDonald’s restaurants were just starting out, they experienced little competition with access to many customers. The population of McDonald’s grew exponentially (or so it seemed!) with few density-dependent factors. Today in the United States, McDonald’s restaurants experience competition with each other and many other fast-food restaurants such as Burger King and Taco Bell. The population of McDonald’s restaurants in the United States has somewhat leveled off because of this competition for customers, a density-dependent factor. A graph of the growth of McDonald’s restaurants in the United States would likely resemble the lazy S shape. Teaching Tips 1. Consider comparing opportunistic and equilibrial life histories in a table with the following top headings: Type of Survivorship Curve, Age of Maturity, Number of Offspring, Use of Parental Care, Stability of the Population, Is the Population Density Dependent?, and Examples. 2. Your class might get some practice analyzing life histories by describing additional examples. Challenge your students to classify the type of survivorship curve that would be expected. Frogs and fish typically produce hundreds of eggs, leading to type III survivorship curves. Elephants and whales typically produce few offspring in life histories that more likely represent type I survivorship curves. Mice and other small mammals are capable of producing litters of 10 or more offspring a year, over a several year period. These mammals have life histories that may be intermediate, leading to type II survivorship curves. 3. The following Center for Disease Control web site provides information and life tables for people living in the United States. ( 4. Compromise is a key lesson in biology. No adaptation can be perfect, no reproductive strategy can maximize all types of efforts. As the text notes, an organism cannot have many offspring and great amounts of parental care. Resources, including time, are limited. Have students imagine how their life as parents would change with the birth of quadruplet children.

Figure 19.2 An indirect census of a prairie dog population

Population Age Structure
The age structure of a population is the distribution of individuals among age groups. The age structure of a population provides insight into The history of a population’s survival Reproductive success How the population relates to environmental factors Student Misconceptions and Concerns 1. Students might imagine that the opportunistic life history is risky and might not be successful over time. Plants such as the agave (century plant) risk all of their reproductive effort on a single life-ending event. However, this reproductive strategy has evolved over time because it has been successful (but like investments, past success does not guarantee future success). 2. Many nonmajors have trouble thinking about the evolution of systems. One analogy that can be developed, especially for economically minded students, makes parallels to the “evolution” of businesses. Consider the introduction and expansion of McDonald’s restaurants in the United States over the last 50 years. When McDonald’s restaurants were just starting out, they experienced little competition with access to many customers. The population of McDonald’s grew exponentially (or so it seemed!) with few density-dependent factors. Today in the United States, McDonald’s restaurants experience competition with each other and many other fast-food restaurants such as Burger King and Taco Bell. The population of McDonald’s restaurants in the United States has somewhat leveled off because of this competition for customers, a density-dependent factor. A graph of the growth of McDonald’s restaurants in the United States would likely resemble the lazy S shape. Teaching Tips 1. Consider comparing opportunistic and equilibrial life histories in a table with the following top headings: Type of Survivorship Curve, Age of Maturity, Number of Offspring, Use of Parental Care, Stability of the Population, Is the Population Density Dependent?, and Examples. 2. Your class might get some practice analyzing life histories by describing additional examples. Challenge your students to classify the type of survivorship curve that would be expected. Frogs and fish typically produce hundreds of eggs, leading to type III survivorship curves. Elephants and whales typically produce few offspring in life histories that more likely represent type I survivorship curves. Mice and other small mammals are capable of producing litters of 10 or more offspring a year, over a several year period. These mammals have life histories that may be intermediate, leading to type II survivorship curves. 3. The following Center for Disease Control web site provides information and life tables for people living in the United States. ( 4. Compromise is a key lesson in biology. No adaptation can be perfect, no reproductive strategy can maximize all types of efforts. As the text notes, an organism cannot have many offspring and great amounts of parental care. Resources, including time, are limited. Have students imagine how their life as parents would change with the birth of quadruplet children.

11 10 9 8 7 Age (years) 6 5 Figure 19.3 Age structure for the males in a population of large cactus finches (inset) on one of the Galápagos Islands in 1987. 4 3 2 2 1 10 20 30 40 50 Percent of population Figure 19.3

Life Tables and Survivorship Curves
Track survivorship Help to determine the most vulnerable stages of the life cycle Survivorship curves Graphically represent some of the data in a life table Are classified based upon the rate of mortality over the life span of an organism Student Misconceptions and Concerns 1. Students might imagine that the opportunistic life history is risky and might not be successful over time. Plants such as the agave (century plant) risk all of their reproductive effort on a single life-ending event. However, this reproductive strategy has evolved over time because it has been successful (but like investments, past success does not guarantee future success). 2. Many nonmajors have trouble thinking about the evolution of systems. One analogy that can be developed, especially for economically minded students, makes parallels to the “evolution” of businesses. Consider the introduction and expansion of McDonald’s restaurants in the United States over the last 50 years. When McDonald’s restaurants were just starting out, they experienced little competition with access to many customers. The population of McDonald’s grew exponentially (or so it seemed!) with few density-dependent factors. Today in the United States, McDonald’s restaurants experience competition with each other and many other fast-food restaurants such as Burger King and Taco Bell. The population of McDonald’s restaurants in the United States has somewhat leveled off because of this competition for customers, a density-dependent factor. A graph of the growth of McDonald’s restaurants in the United States would likely resemble the lazy S shape. Teaching Tips 1. Consider comparing opportunistic and equilibrial life histories in a table with the following top headings: Type of Survivorship Curve, Age of Maturity, Number of Offspring, Use of Parental Care, Stability of the Population, Is the Population Density Dependent?, and Examples. 2. Your class might get some practice analyzing life histories by describing additional examples. Challenge your students to classify the type of survivorship curve that would be expected. Frogs and fish typically produce hundreds of eggs, leading to type III survivorship curves. Elephants and whales typically produce few offspring in life histories that more likely represent type I survivorship curves. Mice and other small mammals are capable of producing litters of 10 or more offspring a year, over a several year period. These mammals have life histories that may be intermediate, leading to type II survivorship curves. 3. The following Center for Disease Control web site provides information and life tables for people living in the United States. ( 4. Compromise is a key lesson in biology. No adaptation can be perfect, no reproductive strategy can maximize all types of efforts. As the text notes, an organism cannot have many offspring and great amounts of parental care. Resources, including time, are limited. Have students imagine how their life as parents would change with the birth of quadruplet children.

Table 19.1 Life Table for the U.S. Population in 2004

Percentage of survivors (log scale)
100 I 10 Percentage of survivors (log scale) II 1 Figure 19.4 Three idealized types of survivorship curves III 0.1 50 100 Percentage of maximum life span Figure 19.4

Life History Traits as Evolutionary Adaptations
An organism’s life history is the set of traits that affect the organism’s schedule of reproduction and survival Key life history traits are the Age at first reproduction Frequency of reproduction Number of offspring Amount of parental care provided Organisms with an opportunistic life history Take immediate advantage of favorable conditions Typically exhibit a Type III survivorship curve Student Misconceptions and Concerns 1. Students might imagine that the opportunistic life history is risky and might not be successful over time. Plants such as the agave (century plant) risk all of their reproductive effort on a single life-ending event. However, this reproductive strategy has evolved over time because it has been successful (but like investments, past success does not guarantee future success). 2. Many nonmajors have trouble thinking about the evolution of systems. One analogy that can be developed, especially for economically minded students, makes parallels to the “evolution” of businesses. Consider the introduction and expansion of McDonald’s restaurants in the United States over the last 50 years. When McDonald’s restaurants were just starting out, they experienced little competition with access to many customers. The population of McDonald’s grew exponentially (or so it seemed!) with few density-dependent factors. Today in the United States, McDonald’s restaurants experience competition with each other and many other fast-food restaurants such as Burger King and Taco Bell. The population of McDonald’s restaurants in the United States has somewhat leveled off because of this competition for customers, a density-dependent factor. A graph of the growth of McDonald’s restaurants in the United States would likely resemble the lazy S shape. Teaching Tips 1. Consider comparing opportunistic and equilibrial life histories in a table with the following top headings: Type of Survivorship Curve, Age of Maturity, Number of Offspring, Use of Parental Care, Stability of the Population, Is the Population Density Dependent?, and Examples. 2. Your class might get some practice analyzing life histories by describing additional examples. Challenge your students to classify the type of survivorship curve that would be expected. Frogs and fish typically produce hundreds of eggs, leading to type III survivorship curves. Elephants and whales typically produce few offspring in life histories that more likely represent type I survivorship curves. Mice and other small mammals are capable of producing litters of 10 or more offspring a year, over a several year period. These mammals have life histories that may be intermediate, leading to type II survivorship curves. 3. The following Center for Disease Control web site provides information and life tables for people living in the United States. ( 4. Compromise is a key lesson in biology. No adaptation can be perfect, no reproductive strategy can maximize all types of efforts. As the text notes, an organism cannot have many offspring and great amounts of parental care. Resources, including time, are limited. Have students imagine how their life as parents would change with the birth of quadruplet children.

Organisms with an equilibrial life history
Reach sexual maturity slowly Produce few, well cared for offspring Are typically large-bodied and longer lived Typically exhibit a Type I survivorship curve Student Misconceptions and Concerns 1. Students might imagine that the opportunistic life history is risky and might not be successful over time. Plants such as the agave (century plant) risk all of their reproductive effort on a single life-ending event. However, this reproductive strategy has evolved over time because it has been successful (but like investments, past success does not guarantee future success). 2. Many nonmajors have trouble thinking about the evolution of systems. One analogy that can be developed, especially for economically minded students, makes parallels to the “evolution” of businesses. Consider the introduction and expansion of McDonald’s restaurants in the United States over the last 50 years. When McDonald’s restaurants were just starting out, they experienced little competition with access to many customers. The population of McDonald’s grew exponentially (or so it seemed!) with few density-dependent factors. Today in the United States, McDonald’s restaurants experience competition with each other and many other fast-food restaurants such as Burger King and Taco Bell. The population of McDonald’s restaurants in the United States has somewhat leveled off because of this competition for customers, a density-dependent factor. A graph of the growth of McDonald’s restaurants in the United States would likely resemble the lazy S shape. Teaching Tips 1. Consider comparing opportunistic and equilibrial life histories in a table with the following top headings: Type of Survivorship Curve, Age of Maturity, Number of Offspring, Use of Parental Care, Stability of the Population, Is the Population Density Dependent?, and Examples. 2. Your class might get some practice analyzing life histories by describing additional examples. Challenge your students to classify the type of survivorship curve that would be expected. Frogs and fish typically produce hundreds of eggs, leading to type III survivorship curves. Elephants and whales typically produce few offspring in life histories that more likely represent type I survivorship curves. Mice and other small mammals are capable of producing litters of 10 or more offspring a year, over a several year period. These mammals have life histories that may be intermediate, leading to type II survivorship curves. 3. The following Center for Disease Control web site provides information and life tables for people living in the United States. ( 4. Compromise is a key lesson in biology. No adaptation can be perfect, no reproductive strategy can maximize all types of efforts. As the text notes, an organism cannot have many offspring and great amounts of parental care. Resources, including time, are limited. Have students imagine how their life as parents would change with the birth of quadruplet children.

Table 19.2 Some Life History Characteristics of Opportunistic and Equilibrial Populations

Dandelions have an opportunistic life history
Table 19.2a Some Life History Characteristics of Opportunistic and Equilibrial Populations Dandelions have an opportunistic life history Table 19.2a

Elephants have an equilibrial life history
Table 19.2b Some Life History Characteristics of Opportunistic and Equilibrial Populations Elephants have an equilibrial life history Table 19.2b

POPULATION GROWTH MODELS
Population size fluctuates as individuals Are born Immigrate into an area Emigrate away Die Exponential population growth describes the expansion of a population in an ideal and unlimited environment. Exponential growth explains how A few dozen rabbits can multiple into millions In certain circumstances following disasters, organisms that have opportunistic life history patterns can rapidly recolonize a habitat Student Misconceptions and Concerns 1. Students with limited biology backgrounds may unrealistically expect simplistic explanations. When we consider the factors that limit population size, we learn to appreciate the complex nature of biology. As noted in the text, population growth models are approximations and density dependent and density independent factors are usually both involved to some extent. Teaching Tips 1. Exponential growth of a population is like compounded interest on a bank account. The growth of the account is initially small, but as the interest earns interest, the growth expands. For example, $1000 invested at 7% interest is worth more than $30,000 in 50 years. Consider a short assignment to have students calculate the value of a simple interest-bearing investment over a set period of years, similar to the example just noted. 2. It is typically easier to understand a concept when the examples are familiar. Consider the biology of your region and identify a species that is likely to be well known by your students. Perhaps this will be a squirrel population on your campus. Challenge your class to imagine the changes in this squirrel population if a) a strong storm toppled half the trees on campus or b) a large group of dogs moved onto campus for a few weeks. 3. Consider challenging your class to explain why the lynx and hare cycle does not result in the elimination of one or both of the species. Why don’t we see hare’s hunted to extinction? Students may not have considered the difficulty in finding prey when prey populations are low. This challenge permits a recovery of the hare population, which in turn supports the recovery of the lynx population.

Population size (N) Time (months) 500 450 400 350 300 250 200 150 100
Figure 19.5 Exponential growth of a rabbit population 100 50 1 2 3 4 5 6 7 8 9 10 11 12 Time (months) Figure 19.5

Figure 19.5a Exponential growth of a rabbit population

The Logistic Growth Model: The Reality of a Limited Environment
Limiting factors Are environmental factors that hold population growth in check Restrict the number of individuals that can occupy a habitat The carrying capacity is the maximum population size that a particular environment can sustain. Logistic population growth occurs when the growth rate decreases as the population size approaches carrying capacity. The carrying capacity for a population varies, depending on The species The resources available in the habitat Student Misconceptions and Concerns 1. Students with limited biology backgrounds may unrealistically expect simplistic explanations. When we consider the factors that limit population size, we learn to appreciate the complex nature of biology. As noted in the text, population growth models are approximations and density dependent and density independent factors are usually both involved to some extent. Teaching Tips 1. Exponential growth of a population is like compounded interest on a bank account. The growth of the account is initially small, but as the interest earns interest, the growth expands. For example, $1000 invested at 7% interest is worth more than $30,000 in 50 years. Consider a short assignment to have students calculate the value of a simple interest-bearing investment over a set period of years, similar to the example just noted. 2. It is typically easier to understand a concept when the examples are familiar. Consider the biology of your region and identify a species that is likely to be well known by your students. Perhaps this will be a squirrel population on your campus. Challenge your class to imagine the changes in this squirrel population if a) a strong storm toppled half the trees on campus or b) a large group of dogs moved onto campus for a few weeks. 3. Consider challenging your class to explain why the lynx and hare cycle does not result in the elimination of one or both of the species. Why don’t we see hare’s hunted to extinction? Students may not have considered the difficulty in finding prey when prey populations are low. This challenge permits a recovery of the hare population, which in turn supports the recovery of the lynx population. © 2010 Pearson Education, Inc.

Breeding male fur seals
10 8 Breeding male fur seals (thousands) 6 4 2 Figure 19.6 Logistic growth of a seal population 1915 1925 1935 1945 Year Figure 19.6

Figure 19.6a Logistic growth of a seal population

No natural population fits either one perfectly.
Organisms exhibiting equilibrial life history patterns occur in environments where the population size is at or near carrying capacity. The logistic model and the exponential model are theoretical ideals of population growth. No natural population fits either one perfectly. Student Misconceptions and Concerns 1. Students with limited biology backgrounds may unrealistically expect simplistic explanations. When we consider the factors that limit population size, we learn to appreciate the complex nature of biology. As noted in the text, population growth models are approximations and density dependent and density independent factors are usually both involved to some extent. Teaching Tips 1. Exponential growth of a population is like compounded interest on a bank account. The growth of the account is initially small, but as the interest earns interest, the growth expands. For example, $1000 invested at 7% interest is worth more than $30,000 in 50 years. Consider a short assignment to have students calculate the value of a simple interest-bearing investment over a set period of years, similar to the example just noted. 2. It is typically easier to understand a concept when the examples are familiar. Consider the biology of your region and identify a species that is likely to be well known by your students. Perhaps this will be a squirrel population on your campus. Challenge your class to imagine the changes in this squirrel population if a) a strong storm toppled half the trees on campus or b) a large group of dogs moved onto campus for a few weeks. 3. Consider challenging your class to explain why the lynx and hare cycle does not result in the elimination of one or both of the species. Why don’t we see hare’s hunted to extinction? Students may not have considered the difficulty in finding prey when prey populations are low. This challenge permits a recovery of the hare population, which in turn supports the recovery of the lynx population.

Exponential growth Number of individuals Carrying capacity
Logistic growth Figure 19.7 Comparison of exponential and logistic growth Time Figure 19.7

Regulation of Population Growth Density-Dependent Factors
The logistic model is a description of intraspecific competition, competition between individuals of the same species for the same limited resources. As population size increases Competition becomes more intense The growth rate declines in proportion to the intensity of competition A density-dependent factor is a population-limiting factor whose effects intensify as the population increases in density. Student Misconceptions and Concerns 1. Students with limited biology backgrounds may unrealistically expect simplistic explanations. When we consider the factors that limit population size, we learn to appreciate the complex nature of biology. As noted in the text, population growth models are approximations and density dependent and density independent factors are usually both involved to some extent. Teaching Tips 1. Exponential growth of a population is like compounded interest on a bank account. The growth of the account is initially small, but as the interest earns interest, the growth expands. For example, $1000 invested at 7% interest is worth more than $30,000 in 50 years. Consider a short assignment to have students calculate the value of a simple interest-bearing investment over a set period of years, similar to the example just noted. 2. It is typically easier to understand a concept when the examples are familiar. Consider the biology of your region and identify a species that is likely to be well known by your students. Perhaps this will be a squirrel population on your campus. Challenge your class to imagine the changes in this squirrel population if a) a strong storm toppled half the trees on campus or b) a large group of dogs moved onto campus for a few weeks. 3. Consider challenging your class to explain why the lynx and hare cycle does not result in the elimination of one or both of the species. Why don’t we see hare’s hunted to extinction? Students may not have considered the difficulty in finding prey when prey populations are low. This challenge permits a recovery of the hare population, which in turn supports the recovery of the lynx population. © 2010 Pearson Education, Inc.

Number of breeding pairs
12 11 10 Average clutch size 9 8 Figure 19.8a Density-dependent regulation of population growth 10 20 30 40 50 60 70 80 90 Number of breeding pairs (a) Decreasing birth rate with increasing density in a population of great tits Figure 19.8a

Density (beetles/0.5 g flour)
100 80 60 Survivors (%) 40 20 Figure 19.8b Density-dependent regulation of population growth 20 40 60 80 100 120 Density (beetles/0.5 g flour) (b) Decreasing survival rates with increasing density in a population of flour beetles Figure 19.8b

Density-dependent factors may include
Accumulation of toxic wastes Limited food supply Limited territory Student Misconceptions and Concerns 1. Students with limited biology backgrounds may unrealistically expect simplistic explanations. When we consider the factors that limit population size, we learn to appreciate the complex nature of biology. As noted in the text, population growth models are approximations and density dependent and density independent factors are usually both involved to some extent. Teaching Tips 1. Exponential growth of a population is like compounded interest on a bank account. The growth of the account is initially small, but as the interest earns interest, the growth expands. For example, $1000 invested at 7% interest is worth more than $30,000 in 50 years. Consider a short assignment to have students calculate the value of a simple interest-bearing investment over a set period of years, similar to the example just noted. 2. It is typically easier to understand a concept when the examples are familiar. Consider the biology of your region and identify a species that is likely to be well known by your students. Perhaps this will be a squirrel population on your campus. Challenge your class to imagine the changes in this squirrel population if a) a strong storm toppled half the trees on campus or b) a large group of dogs moved onto campus for a few weeks. 3. Consider challenging your class to explain why the lynx and hare cycle does not result in the elimination of one or both of the species. Why don’t we see hare’s hunted to extinction? Students may not have considered the difficulty in finding prey when prey populations are low. This challenge permits a recovery of the hare population, which in turn supports the recovery of the lynx population.

Figure 19.9 Space as a limiting resource in a population of gannets

Density-Independent Factors
Are population-limiting factors whose intensity is unrelated to population density Include abiotic factors such as: fires, floods, storms, etc… In many natural populations, density-independent factors limit population size before density-dependent factors become important. Over the long term, most populations are probably regulated by a mixture of both Student Misconceptions and Concerns 1. Students with limited biology backgrounds may unrealistically expect simplistic explanations. When we consider the factors that limit population size, we learn to appreciate the complex nature of biology. As noted in the text, population growth models are approximations and density dependent and density independent factors are usually both involved to some extent. Teaching Tips 1. Exponential growth of a population is like compounded interest on a bank account. The growth of the account is initially small, but as the interest earns interest, the growth expands. For example, $1000 invested at 7% interest is worth more than $30,000 in 50 years. Consider a short assignment to have students calculate the value of a simple interest-bearing investment over a set period of years, similar to the example just noted. 2. It is typically easier to understand a concept when the examples are familiar. Consider the biology of your region and identify a species that is likely to be well known by your students. Perhaps this will be a squirrel population on your campus. Challenge your class to imagine the changes in this squirrel population if a) a strong storm toppled half the trees on campus or b) a large group of dogs moved onto campus for a few weeks. 3. Consider challenging your class to explain why the lynx and hare cycle does not result in the elimination of one or both of the species. Why don’t we see hare’s hunted to extinction? Students may not have considered the difficulty in finding prey when prey populations are low. This challenge permits a recovery of the hare population, which in turn supports the recovery of the lynx population.

Number of aphids Exponential growth Sudden decline Apr May Jun Jul Aug
Figure Weather change as a density-independent factor limiting growth of an aphid population Apr May Jun Jul Aug Sep Oct Nov Dec Figure 19.10

Population Cycles Some populations have regular boom-and-bust cycles characterized by periods of rapid growth followed by steep population declines. A well studied example of boom and bust cycles are the cycles of snowshoe hares and lynxs The cause of these hare and lynx cycles may be Winter food shortages for the hares Overexploitation of hares by lynx Or a combination of both Student Misconceptions and Concerns 1. Students with limited biology backgrounds may unrealistically expect simplistic explanations. When we consider the factors that limit population size, we learn to appreciate the complex nature of biology. As noted in the text, population growth models are approximations and density dependent and density independent factors are usually both involved to some extent. Teaching Tips 1. Exponential growth of a population is like compounded interest on a bank account. The growth of the account is initially small, but as the interest earns interest, the growth expands. For example, $1000 invested at 7% interest is worth more than $30,000 in 50 years. Consider a short assignment to have students calculate the value of a simple interest-bearing investment over a set period of years, similar to the example just noted. 2. It is typically easier to understand a concept when the examples are familiar. Consider the biology of your region and identify a species that is likely to be well known by your students. Perhaps this will be a squirrel population on your campus. Challenge your class to imagine the changes in this squirrel population if a) a strong storm toppled half the trees on campus or b) a large group of dogs moved onto campus for a few weeks. 3. Consider challenging your class to explain why the lynx and hare cycle does not result in the elimination of one or both of the species. Why don’t we see hare’s hunted to extinction? Students may not have considered the difficulty in finding prey when prey populations are low. This challenge permits a recovery of the hare population, which in turn supports the recovery of the lynx population.

Figure 19.11 Snowshoe hare Lynx Hare population (thousands)
160 Hare population (thousands) Lynx population (thousands) 120 9 80 6 40 3 1850 1900 Year Figure Population cycles of the snowshoe hare and the lynx Figure 19.11

APPLICATIONS OF POPULATION ECOLOGY
Population ecology is used to Increase populations of organisms we wish to harvest Decrease populations of pests Save populations of organisms threatened with extinction The U.S. Endangered Species Act defines An endangered species as one that is in danger of extinction throughout all or a significant portion of its range A threatened species as one that is likely to become endangered in the foreseeable future A major factor in population decline is habitat destruction or modification. Student Misconceptions and Concerns 1. Most students do not understand the dangers of relocating wildlife or letting their pet loose in a park or non-native environment. As noted in the text, the consequences of accidental or deliberate introductions costs the United States more than $130 billion a year. What might seem like a kind gesture to your students is a very dangerous activity, little understood by the public. 2. The history of the widespread abuse of pesticides in North America occurred before most of your students were born. Yet, the lessons of this recent history remind us of the potential consequences. Rachel Carson’s book Silent Spring, or passages from it, might be a good assignment for your class. Teaching Tips 1. Students are likely to expect that spraying insecticides or using various killing devices (such as bug zappers) will make a significant impact in a pest population. However, many pesticides kill pests and their predators. Further, most pest populations are capable of recovering quickly, perhaps faster than their predators. The complexity of life histories and population dynamics help to illustrate the complexities inherent to biological systems and the unexpected consequences. 2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species, instead of wasting pollen by taking it to different species. 3. The United States Department of Agriculture sponsors the National Invasive Species Information Center, which has a web site at ( 4. Consider a class assignment to explore the collapse of the northern cod fishery and to identify other fish species in danger of over harvesting. Shark populations may be experiencing such a decline. As emphasized in the text, harvesting a population down to intermediate levels maximizes the sustained yield.

The red-cockaded woodpecker
Requires longleaf pine forests with clear flight paths between trees Suffered from fire suppression, increasing the height of the vegetation on the forest floor Recovered from near-extinction to sustainable populations due to controlled burning and other management methods Student Misconceptions and Concerns 1. Most students do not understand the dangers of relocating wildlife or letting their pet loose in a park or non-native environment. As noted in the text, the consequences of accidental or deliberate introductions costs the United States more than $130 billion a year. What might seem like a kind gesture to your students is a very dangerous activity, little understood by the public. 2. The history of the widespread abuse of pesticides in North America occurred before most of your students were born. Yet, the lessons of this recent history remind us of the potential consequences. Rachel Carson’s book Silent Spring, or passages from it, might be a good assignment for your class. Teaching Tips 1. Students are likely to expect that spraying insecticides or using various killing devices (such as bug zappers) will make a significant impact in a pest population. However, many pesticides kill pests and their predators. Further, most pest populations are capable of recovering quickly, perhaps faster than their predators. The complexity of life histories and population dynamics help to illustrate the complexities inherent to biological systems and the unexpected consequences. 2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species, instead of wasting pollen by taking it to different species. 3. The United States Department of Agriculture sponsors the National Invasive Species Information Center, which has a web site at ( 4. Consider a class assignment to explore the collapse of the northern cod fishery and to identify other fish species in danger of over harvesting. Shark populations may be experiencing such a decline. As emphasized in the text, harvesting a population down to intermediate levels maximizes the sustained yield.

Figure 19.12 A red-cockaded woodpecker perches at the entrance to its
nest in a long-leaf pine tree. High, dense undergrowth impedes the woodpeckers’ access to feeding grounds. Low undergrowth offers birds a clear flight path between nest sites and feeding grounds. Figure Habitat of the red-cockaded woodpecker Figure 19.12

Sustainable Resource Management
According to the logistic growth model, the fastest growth rate occurs when a population size is at roughly half the carrying capacity. Theoretically, populations should be harvested down to this level, assuming that growth rate and carrying capacity are stable over time. Student Misconceptions and Concerns 1. Most students do not understand the dangers of relocating wildlife or letting their pet loose in a park or non-native environment. As noted in the text, the consequences of accidental or deliberate introductions costs the United States more than $130 billion a year. What might seem like a kind gesture to your students is a very dangerous activity, little understood by the public. 2. The history of the widespread abuse of pesticides in North America occurred before most of your students were born. Yet, the lessons of this recent history remind us of the potential consequences. Rachel Carson’s book Silent Spring, or passages from it, might be a good assignment for your class. Teaching Tips 1. Students are likely to expect that spraying insecticides or using various killing devices (such as bug zappers) will make a significant impact in a pest population. However, many pesticides kill pests and their predators. Further, most pest populations are capable of recovering quickly, perhaps faster than their predators. The complexity of life histories and population dynamics help to illustrate the complexities inherent to biological systems and the unexpected consequences. 2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species, instead of wasting pollen by taking it to different species. 3. The United States Department of Agriculture sponsors the National Invasive Species Information Center, which has a web site at ( 4. Consider a class assignment to explore the collapse of the northern cod fishery and to identify other fish species in danger of over harvesting. Shark populations may be experiencing such a decline. As emphasized in the text, harvesting a population down to intermediate levels maximizes the sustained yield.

In the northern Atlantic cod fishery
Estimates of cod stocks were too high The practice of discarding young cod (not of legal size) at sea caused a higher mortality rate than was predicted The fishery collapsed in 1992 and has not recovered Student Misconceptions and Concerns 1. Most students do not understand the dangers of relocating wildlife or letting their pet loose in a park or non-native environment. As noted in the text, the consequences of accidental or deliberate introductions costs the United States more than $130 billion a year. What might seem like a kind gesture to your students is a very dangerous activity, little understood by the public. 2. The history of the widespread abuse of pesticides in North America occurred before most of your students were born. Yet, the lessons of this recent history remind us of the potential consequences. Rachel Carson’s book Silent Spring, or passages from it, might be a good assignment for your class. Teaching Tips 1. Students are likely to expect that spraying insecticides or using various killing devices (such as bug zappers) will make a significant impact in a pest population. However, many pesticides kill pests and their predators. Further, most pest populations are capable of recovering quickly, perhaps faster than their predators. The complexity of life histories and population dynamics help to illustrate the complexities inherent to biological systems and the unexpected consequences. 2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species, instead of wasting pollen by taking it to different species. 3. The United States Department of Agriculture sponsors the National Invasive Species Information Center, which has a web site at ( 4. Consider a class assignment to explore the collapse of the northern cod fishery and to identify other fish species in danger of over harvesting. Shark populations may be experiencing such a decline. As emphasized in the text, harvesting a population down to intermediate levels maximizes the sustained yield.

Yield (thousands of metric tons)
900 800 700 600 Yield (thousands of metric tons) 500 400 300 200 Figure Collapse of northern cod fishery off Newfoundland 100 1960 1970 1980 1990 2000 Figure 19.13

Invasive Species An invasive species
Is a non-native species that has spread far beyond the original point of introduction Causes environmental or economic damage by colonizing and dominating suitable habitats In the United States, invasive species cost about $137 billion a year. Invasive species typically exhibit an opportunistic life history pattern. Student Misconceptions and Concerns 1. Most students do not understand the dangers of relocating wildlife or letting their pet loose in a park or non-native environment. As noted in the text, the consequences of accidental or deliberate introductions costs the United States more than $130 billion a year. What might seem like a kind gesture to your students is a very dangerous activity, little understood by the public. 2. The history of the widespread abuse of pesticides in North America occurred before most of your students were born. Yet, the lessons of this recent history remind us of the potential consequences. Rachel Carson’s book Silent Spring, or passages from it, might be a good assignment for your class. Teaching Tips 1. Students are likely to expect that spraying insecticides or using various killing devices (such as bug zappers) will make a significant impact in a pest population. However, many pesticides kill pests and their predators. Further, most pest populations are capable of recovering quickly, perhaps faster than their predators. The complexity of life histories and population dynamics help to illustrate the complexities inherent to biological systems and the unexpected consequences. 2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species, instead of wasting pollen by taking it to different species. 3. The United States Department of Agriculture sponsors the National Invasive Species Information Center, which has a web site at ( 4. Consider a class assignment to explore the collapse of the northern cod fishery and to identify other fish species in danger of over harvesting. Shark populations may be experiencing such a decline. As emphasized in the text, harvesting a population down to intermediate levels maximizes the sustained yield.

Cheatgrass Is an invasive species in the western United States
Currently covers more than 60 million acres of rangeland formerly dominated by native grasses and sagebrush Produces seeds earlier and in greater abundance than native species Forms highly flammable brush creating fires that native plants cannot tolerate Student Misconceptions and Concerns 1. Most students do not understand the dangers of relocating wildlife or letting their pet loose in a park or non-native environment. As noted in the text, the consequences of accidental or deliberate introductions costs the United States more than $130 billion a year. What might seem like a kind gesture to your students is a very dangerous activity, little understood by the public. 2. The history of the widespread abuse of pesticides in North America occurred before most of your students were born. Yet, the lessons of this recent history remind us of the potential consequences. Rachel Carson’s book Silent Spring, or passages from it, might be a good assignment for your class. Teaching Tips 1. Students are likely to expect that spraying insecticides or using various killing devices (such as bug zappers) will make a significant impact in a pest population. However, many pesticides kill pests and their predators. Further, most pest populations are capable of recovering quickly, perhaps faster than their predators. The complexity of life histories and population dynamics help to illustrate the complexities inherent to biological systems and the unexpected consequences. 2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species, instead of wasting pollen by taking it to different species. 3. The United States Department of Agriculture sponsors the National Invasive Species Information Center, which has a web site at ( 4. Consider a class assignment to explore the collapse of the northern cod fishery and to identify other fish species in danger of over harvesting. Shark populations may be experiencing such a decline. As emphasized in the text, harvesting a population down to intermediate levels maximizes the sustained yield.

Figure 19.14 A reddish sea of cheatgrass threatens to overwhelm native sagebrush (green)

European starlings Are another invasive species
Were first released into New York in 1890 Now number more than 200 million in the United States Student Misconceptions and Concerns 1. Most students do not understand the dangers of relocating wildlife or letting their pet loose in a park or non-native environment. As noted in the text, the consequences of accidental or deliberate introductions costs the United States more than $130 billion a year. What might seem like a kind gesture to your students is a very dangerous activity, little understood by the public. 2. The history of the widespread abuse of pesticides in North America occurred before most of your students were born. Yet, the lessons of this recent history remind us of the potential consequences. Rachel Carson’s book Silent Spring, or passages from it, might be a good assignment for your class. Teaching Tips 1. Students are likely to expect that spraying insecticides or using various killing devices (such as bug zappers) will make a significant impact in a pest population. However, many pesticides kill pests and their predators. Further, most pest populations are capable of recovering quickly, perhaps faster than their predators. The complexity of life histories and population dynamics help to illustrate the complexities inherent to biological systems and the unexpected consequences. 2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species, instead of wasting pollen by taking it to different species. 3. The United States Department of Agriculture sponsors the National Invasive Species Information Center, which has a web site at ( 4. Consider a class assignment to explore the collapse of the northern cod fishery and to identify other fish species in danger of over harvesting. Shark populations may be experiencing such a decline. As emphasized in the text, harvesting a population down to intermediate levels maximizes the sustained yield.

Figure 19.15 A large flock of starlings (inset) settling into a tree to roost for the night

Biological Control of Pests
Invasive species may benefit from the absence of Pathogens Predators Herbivores Biological control Is the intentional release of a natural enemy to attack a pest population Is used to manage an invasive species Student Misconceptions and Concerns 1. Most students do not understand the dangers of relocating wildlife or letting their pet loose in a park or non-native environment. As noted in the text, the consequences of accidental or deliberate introductions costs the United States more than $130 billion a year. What might seem like a kind gesture to your students is a very dangerous activity, little understood by the public. 2. The history of the widespread abuse of pesticides in North America occurred before most of your students were born. Yet, the lessons of this recent history remind us of the potential consequences. Rachel Carson’s book Silent Spring, or passages from it, might be a good assignment for your class. Teaching Tips 1. Students are likely to expect that spraying insecticides or using various killing devices (such as bug zappers) will make a significant impact in a pest population. However, many pesticides kill pests and their predators. Further, most pest populations are capable of recovering quickly, perhaps faster than their predators. The complexity of life histories and population dynamics help to illustrate the complexities inherent to biological systems and the unexpected consequences. 2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species, instead of wasting pollen by taking it to different species. 3. The United States Department of Agriculture sponsors the National Invasive Species Information Center, which has a web site at ( 4. Consider a class assignment to explore the collapse of the northern cod fishery and to identify other fish species in danger of over harvesting. Shark populations may be experiencing such a decline. As emphasized in the text, harvesting a population down to intermediate levels maximizes the sustained yield.

Although initially successful, natural selection favored
In 1950, the Australian government introduced a virus lethal to European rabbits into the rabbits’ Australian environment. Although initially successful, natural selection favored Resistant rabbits Variations of the virus that Were not fatal or Killed their hosts more slowly Evolutionary changes such as these, in which an adaptation of one species leads to a counteradaptation in a second species, are known as coevolution. Student Misconceptions and Concerns 1. Most students do not understand the dangers of relocating wildlife or letting their pet loose in a park or non-native environment. As noted in the text, the consequences of accidental or deliberate introductions costs the United States more than $130 billion a year. What might seem like a kind gesture to your students is a very dangerous activity, little understood by the public. 2. The history of the widespread abuse of pesticides in North America occurred before most of your students were born. Yet, the lessons of this recent history remind us of the potential consequences. Rachel Carson’s book Silent Spring, or passages from it, might be a good assignment for your class. Teaching Tips 1. Students are likely to expect that spraying insecticides or using various killing devices (such as bug zappers) will make a significant impact in a pest population. However, many pesticides kill pests and their predators. Further, most pest populations are capable of recovering quickly, perhaps faster than their predators. The complexity of life histories and population dynamics help to illustrate the complexities inherent to biological systems and the unexpected consequences. 2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species, instead of wasting pollen by taking it to different species. 3. The United States Department of Agriculture sponsors the National Invasive Species Information Center, which has a web site at ( 4. Consider a class assignment to explore the collapse of the northern cod fishery and to identify other fish species in danger of over harvesting. Shark populations may be experiencing such a decline. As emphasized in the text, harvesting a population down to intermediate levels maximizes the sustained yield.

Figure 19.16 Kudzu (Pueraria lobata)

The Process of Science: Can Biological Control Defeat Kudzu?
Is an invasive Asian vine Covers about 12,000 square miles of the southeastern United States Has a range limited by cold winters Many strategies to control kudzu have been considered with little success. A fungal pathogen called Myrothecium verrucaria appears to be a promising candidate for biological control. Student Misconceptions and Concerns 1. Most students do not understand the dangers of relocating wildlife or letting their pet loose in a park or non-native environment. As noted in the text, the consequences of accidental or deliberate introductions costs the United States more than $130 billion a year. What might seem like a kind gesture to your students is a very dangerous activity, little understood by the public. 2. The history of the widespread abuse of pesticides in North America occurred before most of your students were born. Yet, the lessons of this recent history remind us of the potential consequences. Rachel Carson’s book Silent Spring, or passages from it, might be a good assignment for your class. Teaching Tips 1. Students are likely to expect that spraying insecticides or using various killing devices (such as bug zappers) will make a significant impact in a pest population. However, many pesticides kill pests and their predators. Further, most pest populations are capable of recovering quickly, perhaps faster than their predators. The complexity of life histories and population dynamics help to illustrate the complexities inherent to biological systems and the unexpected consequences. 2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species, instead of wasting pollen by taking it to different species. 3. The United States Department of Agriculture sponsors the National Invasive Species Information Center, which has a web site at ( 4. Consider a class assignment to explore the collapse of the northern cod fishery and to identify other fish species in danger of over harvesting. Shark populations may be experiencing such a decline. As emphasized in the text, harvesting a population down to intermediate levels maximizes the sustained yield. © 2010 Pearson Education, Inc.

Observation: The fungus Myrothecium verrucaria causes severe disease in other weeds belonging to the same family as kudzu. Question: Will the application of fungal spores of M. verrucaria control an established stand of kudzu in a natural setting? Hypothesis: M. verrucaria treatment that was effective in small outdoor plantings would also be most effective in a natural setting. Prediction: The greatest kudzu mortality would result from the treatment that sprayed the highest concentration of spores in combination with a wetting agent. Results: The hypothesis was supported by the data, as indicated in the following table. Student Misconceptions and Concerns 1. Most students do not understand the dangers of relocating wildlife or letting their pet loose in a park or non-native environment. As noted in the text, the consequences of accidental or deliberate introductions costs the United States more than $130 billion a year. What might seem like a kind gesture to your students is a very dangerous activity, little understood by the public. 2. The history of the widespread abuse of pesticides in North America occurred before most of your students were born. Yet, the lessons of this recent history remind us of the potential consequences. Rachel Carson’s book Silent Spring, or passages from it, might be a good assignment for your class. Teaching Tips 1. Students are likely to expect that spraying insecticides or using various killing devices (such as bug zappers) will make a significant impact in a pest population. However, many pesticides kill pests and their predators. Further, most pest populations are capable of recovering quickly, perhaps faster than their predators. The complexity of life histories and population dynamics help to illustrate the complexities inherent to biological systems and the unexpected consequences. 2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species, instead of wasting pollen by taking it to different species. 3. The United States Department of Agriculture sponsors the National Invasive Species Information Center, which has a web site at ( 4. Consider a class assignment to explore the collapse of the northern cod fishery and to identify other fish species in danger of over harvesting. Shark populations may be experiencing such a decline. As emphasized in the text, harvesting a population down to intermediate levels maximizes the sustained yield.

Treatment Mortality (%) Figure 19.17 Spores (2  106/ml)  water
Spores (2  106/ml)  wetting agent Spores (2  107/ml)  wetting agent Wetting agent only Untreated 20 40 60 80 100 Figure Biological control of a natural infestation of kudzu with the fungus Myrothecium verrucarua Mortality (%) Figure 19.17

Figure 19.17a Biological control of a natural infestation of kudzu with the fungus Myrothecium verrucarua Figure 19.17a

Integrated Pest Management
Agricultural operations create their own highly managed ecosystems that Have genetically similar individuals (a monoculture) Are planted in close proximity to each other Function as a “banquet” for Plant-eating animals Pathogenic bacteria Viruses Like invasive species, most crop pests Have an opportunistic life history pattern Can cause extensive crop damage Student Misconceptions and Concerns 1. Most students do not understand the dangers of relocating wildlife or letting their pet loose in a park or non-native environment. As noted in the text, the consequences of accidental or deliberate introductions costs the United States more than $130 billion a year. What might seem like a kind gesture to your students is a very dangerous activity, little understood by the public. 2. The history of the widespread abuse of pesticides in North America occurred before most of your students were born. Yet, the lessons of this recent history remind us of the potential consequences. Rachel Carson’s book Silent Spring, or passages from it, might be a good assignment for your class. Teaching Tips 1. Students are likely to expect that spraying insecticides or using various killing devices (such as bug zappers) will make a significant impact in a pest population. However, many pesticides kill pests and their predators. Further, most pest populations are capable of recovering quickly, perhaps faster than their predators. The complexity of life histories and population dynamics help to illustrate the complexities inherent to biological systems and the unexpected consequences. 2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species, instead of wasting pollen by taking it to different species. 3. The United States Department of Agriculture sponsors the National Invasive Species Information Center, which has a web site at ( 4. Consider a class assignment to explore the collapse of the northern cod fishery and to identify other fish species in danger of over harvesting. Shark populations may be experiencing such a decline. As emphasized in the text, harvesting a population down to intermediate levels maximizes the sustained yield.

Figure 19.18 Plants infested with Japanese beetles (left) and grasshoppers (right)

Integrated pest management (IPM)
Pesticides may Result in pesticide-resistant pests Kill the pest and their natural predators Kill pollinators Integrated pest management (IPM) Tolerates a low level of pests instead of total eradication Produces a sustainable control of agricultural pests Uses a combination of Biological methods Chemical methods Cultural methods Student Misconceptions and Concerns 1. Most students do not understand the dangers of relocating wildlife or letting their pet loose in a park or non-native environment. As noted in the text, the consequences of accidental or deliberate introductions costs the United States more than $130 billion a year. What might seem like a kind gesture to your students is a very dangerous activity, little understood by the public. 2. The history of the widespread abuse of pesticides in North America occurred before most of your students were born. Yet, the lessons of this recent history remind us of the potential consequences. Rachel Carson’s book Silent Spring, or passages from it, might be a good assignment for your class. Teaching Tips 1. Students are likely to expect that spraying insecticides or using various killing devices (such as bug zappers) will make a significant impact in a pest population. However, many pesticides kill pests and their predators. Further, most pest populations are capable of recovering quickly, perhaps faster than their predators. The complexity of life histories and population dynamics help to illustrate the complexities inherent to biological systems and the unexpected consequences. 2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species, instead of wasting pollen by taking it to different species. 3. The United States Department of Agriculture sponsors the National Invasive Species Information Center, which has a web site at ( 4. Consider a class assignment to explore the collapse of the northern cod fishery and to identify other fish species in danger of over harvesting. Shark populations may be experiencing such a decline. As emphasized in the text, harvesting a population down to intermediate levels maximizes the sustained yield.

IPM methods include Using pest-resistant varieties of crops
Using mixed-species plantings Rotating crops to deprive the pest of a dependable food source Student Misconceptions and Concerns 1. Most students do not understand the dangers of relocating wildlife or letting their pet loose in a park or non-native environment. As noted in the text, the consequences of accidental or deliberate introductions costs the United States more than $130 billion a year. What might seem like a kind gesture to your students is a very dangerous activity, little understood by the public. 2. The history of the widespread abuse of pesticides in North America occurred before most of your students were born. Yet, the lessons of this recent history remind us of the potential consequences. Rachel Carson’s book Silent Spring, or passages from it, might be a good assignment for your class. Teaching Tips 1. Students are likely to expect that spraying insecticides or using various killing devices (such as bug zappers) will make a significant impact in a pest population. However, many pesticides kill pests and their predators. Further, most pest populations are capable of recovering quickly, perhaps faster than their predators. The complexity of life histories and population dynamics help to illustrate the complexities inherent to biological systems and the unexpected consequences. 2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species, instead of wasting pollen by taking it to different species. 3. The United States Department of Agriculture sponsors the National Invasive Species Information Center, which has a web site at ( 4. Consider a class assignment to explore the collapse of the northern cod fishery and to identify other fish species in danger of over harvesting. Shark populations may be experiencing such a decline. As emphasized in the text, harvesting a population down to intermediate levels maximizes the sustained yield.

HUMAN POPULATION GROWTH The History of Human Population Growth
From 2000 to 500 years ago (in 1500) Mortality was high Births and deaths were about equal The world population held steady at about 300 million The world’s population began to grow exponentially in the 1900s due to advances in Nutrition Sanitation Health care Student Misconceptions and Concerns 1. Students may not appreciate the energy and effort that goes into the generation of their food and products they use daily. A simple analysis of packaging materials will reveal some of the daily investment in convenience. Consider some small task for your students to do to best estimate their ecological footprint. See Teaching Tip #5 below for a list of web sites where your students can calculate their ecological footprint. 2. We often grow tired and frustrated by the long list of problems caused by humans. Many feel helpless. You might consider referencing these web sites for basic ideas on what individuals can do to start to make a difference. 1) 2) 3) Teaching Tips 1. You might surprise your class by noting that more people are alive today than have ever lived before and died. An examination of Figure reveals why this is true. 2. The US government’s Census Bureau sponsors a US and World population clock at ( ) for the most recent estimates of US and world human populations. 3. Medicare and Social Security will be increasingly impacted as the US population ages. By contrast, you might want to discuss the occupational outlook for professions that will address the growing needs of the elderly and the opportunity to invest in companies that will capitalize on these changes. 4. The United States has an ecological footprint greater than the land of the United States. Consider asking your class to explain how this is possible, and what this means to other countries. If you spend some time doing various conversions, you will find that the average ecological footprint of a person in the United States is about equal to the area of 18 football fields with end zones. This was calculated using the following figures. a) 1 football field with end zones is square feet (360 x 160 feet) b) 1 acre = sq. feet c) acres = 1 hectare = 107,593 square feet d) 1.87 football fields in 1 hectare = 107,593 (1 hectare) sq. feet / sq. feet (football field with end zones) e) 17.6 football fields = 9.4 hectare x 1.87 football fields = average ecological footprint of each US citizen. 5. Many web resources are available for students to calculate their ecological footprint. A few of them are noted below. © 2010 Pearson Education, Inc.

Annual increase (millions) Total population (billions)
100 10 Population increase 80 8 60 6 Annual increase (millions) Total population (billions) 40 4 Total population size 20 2 Figure Five centuries of human population growth, projected to 2050 1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000 2050 Year Figure 19.19

Worldwide population growth rates reflect a mosaic of the changes occurring in different countries.
In the most developed nations, the overall growth rates are near zero. In the developing world Death rates have dropped High birth rates persist Student Misconceptions and Concerns 1. Students may not appreciate the energy and effort that goes into the generation of their food and products they use daily. A simple analysis of packaging materials will reveal some of the daily investment in convenience. Consider some small task for your students to do to best estimate their ecological footprint. See Teaching Tip #5 below for a list of web sites where your students can calculate their ecological footprint. 2. We often grow tired and frustrated by the long list of problems caused by humans. Many feel helpless. You might consider referencing these web sites for basic ideas on what individuals can do to start to make a difference. 1) 2) 3) Teaching Tips 1. You might surprise your class by noting that more people are alive today than have ever lived before and died. An examination of Figure reveals why this is true. 2. The US government’s Census Bureau sponsors a US and World population clock at ( ) for the most recent estimates of US and world human populations. 3. Medicare and Social Security will be increasingly impacted as the US population ages. By contrast, you might want to discuss the occupational outlook for professions that will address the growing needs of the elderly and the opportunity to invest in companies that will capitalize on these changes. 4. The United States has an ecological footprint greater than the land of the United States. Consider asking your class to explain how this is possible, and what this means to other countries. If you spend some time doing various conversions, you will find that the average ecological footprint of a person in the United States is about equal to the area of 18 football fields with end zones. This was calculated using the following figures. a) 1 football field with end zones is square feet (360 x 160 feet) b) 1 acre = sq. feet c) acres = 1 hectare = 107,593 square feet d) 1.87 football fields in 1 hectare = 107,593 (1 hectare) sq. feet / sq. feet (football field with end zones) e) 17.6 football fields = 9.4 hectare x 1.87 football fields = average ecological footprint of each US citizen. 5. Many web resources are available for students to calculate their ecological footprint. A few of them are noted below.

Table 19.3 Population Trends in 2008

Age Structures Age structures help predict a population’s future growth. The following figure shows the estimated and projected age structures of Mexico’s population in 1985 2010 2035 Population momentum is the continuation of population growth as girls in the prereproductive age group reach their reproductive years. Student Misconceptions and Concerns 1. Students may not appreciate the energy and effort that goes into the generation of their food and products they use daily. A simple analysis of packaging materials will reveal some of the daily investment in convenience. Consider some small task for your students to do to best estimate their ecological footprint. See Teaching Tip #5 below for a list of web sites where your students can calculate their ecological footprint. 2. We often grow tired and frustrated by the long list of problems caused by humans. Many feel helpless. You might consider referencing these web sites for basic ideas on what individuals can do to start to make a difference. 1) 2) 3) Teaching Tips 1. You might surprise your class by noting that more people are alive today than have ever lived before and died. An examination of Figure reveals why this is true. 2. The US government’s Census Bureau sponsors a US and World population clock at ( ) for the most recent estimates of US and world human populations. 3. Medicare and Social Security will be increasingly impacted as the US population ages. By contrast, you might want to discuss the occupational outlook for professions that will address the growing needs of the elderly and the opportunity to invest in companies that will capitalize on these changes. 4. The United States has an ecological footprint greater than the land of the United States. Consider asking your class to explain how this is possible, and what this means to other countries. If you spend some time doing various conversions, you will find that the average ecological footprint of a person in the United States is about equal to the area of 18 football fields with end zones. This was calculated using the following figures. a) 1 football field with end zones is square feet (360 x 160 feet) b) 1 acre = sq. feet c) acres = 1 hectare = 107,593 square feet d) 1.87 football fields in 1 hectare = 107,593 (1 hectare) sq. feet / sq. feet (football field with end zones) e) 17.6 football fields = 9.4 hectare x 1.87 football fields = average ecological footprint of each US citizen. 5. Many web resources are available for students to calculate their ecological footprint. A few of them are noted below.

Figure 19.20 Figure 19.20 Population momentum in Mexico 80 75–79
1985 2010 2035 80 75–79 70–74 65–69 Male Female Male Female Male Female 60–64 55–59 50–54 45–49 Age 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 0–4 Figure Population momentum in Mexico 5 4 3 2 1 1 2 3 4 5 5 4 3 2 1 1 2 3 4 5 5 4 3 2 1 1 2 3 4 5 Population in millions Total population size  76,767,225 Population in millions Total population size  112,468,855 Population in millions Total population size  139,457,070 Figure 19.20

Age structure diagrams may also indicate social conditions
Age structure diagrams may also indicate social conditions. An expanding population needs Schools Employment Infrastructure Trends in the age structure of the United States from 1983 to 2033 reveal important patterns. Student Misconceptions and Concerns 1. Students may not appreciate the energy and effort that goes into the generation of their food and products they use daily. A simple analysis of packaging materials will reveal some of the daily investment in convenience. Consider some small task for your students to do to best estimate their ecological footprint. See Teaching Tip #5 below for a list of web sites where your students can calculate their ecological footprint. 2. We often grow tired and frustrated by the long list of problems caused by humans. Many feel helpless. You might consider referencing these web sites for basic ideas on what individuals can do to start to make a difference. 1) 2) 3) Teaching Tips 1. You might surprise your class by noting that more people are alive today than have ever lived before and died. An examination of Figure reveals why this is true. 2. The US government’s Census Bureau sponsors a US and World population clock at ( ) for the most recent estimates of US and world human populations. 3. Medicare and Social Security will be increasingly impacted as the US population ages. By contrast, you might want to discuss the occupational outlook for professions that will address the growing needs of the elderly and the opportunity to invest in companies that will capitalize on these changes. 4. The United States has an ecological footprint greater than the land of the United States. Consider asking your class to explain how this is possible, and what this means to other countries. If you spend some time doing various conversions, you will find that the average ecological footprint of a person in the United States is about equal to the area of 18 football fields with end zones. This was calculated using the following figures. a) 1 football field with end zones is square feet (360 x 160 feet) b) 1 acre = sq. feet c) acres = 1 hectare = 107,593 square feet d) 1.87 football fields in 1 hectare = 107,593 (1 hectare) sq. feet / sq. feet (football field with end zones) e) 17.6 football fields = 9.4 hectare x 1.87 football fields = average ecological footprint of each US citizen. 5. Many web resources are available for students to calculate their ecological footprint. A few of them are noted below.

1983 2008 2033 Birth years Male Female Birth years Male Female Birth years Male Female 80 before 1904 before 1929 before 1954 75–79 1904–08 1929–33 1954–58 70–74 1909–13 1934–38 1959–63 65–69 1914–18 1939–43 1964–68 60–64 1919–23 1944–48 1969–73 55–59 1924–28 1949–53 1974–78 50–54 1929–33 1954–58 1979–83 45–49 1934–38 1959–63 1984–88 Age 40–44 1939–43 1964–68 1989–93 35–39 1944–48 1969–73 1994–98 30–34 1949–53 1974–78 1999–2003 25–29 1954–58 1979–83 2004–08 20–24 1959–63 1984–88 2009–13 15–19 1964–68 1989–93 2014–18 10–14 1969–73 1994–98 2019–23 5–9 1974–78 1999–2003 2024–28 Figure Age structures for the United States in 1983, 2008, and 2033 (projected) 0–4 1979–83 2004–08 2029–33 12 10 8 6 4 2 2 4 6 8 10 12 12 10 8 6 4 2 2 4 6 8 10 12 12 10 8 6 4 2 2 4 6 8 10 12 Population in millions Total population size  234,307,207 Population in millions Total population size  305,548,183 Population in millions Total population size  383,116,539 Figure 19.21

Our Ecological Footprint
An ecological footprint is an estimate of the amount of land required to provide the raw materials an individual or a population consumes, including: Food Fuel Water Housing Waste disposal Student Misconceptions and Concerns 1. Students may not appreciate the energy and effort that goes into the generation of their food and products they use daily. A simple analysis of packaging materials will reveal some of the daily investment in convenience. Consider some small task for your students to do to best estimate their ecological footprint. See Teaching Tip #5 below for a list of web sites where your students can calculate their ecological footprint. 2. We often grow tired and frustrated by the long list of problems caused by humans. Many feel helpless. You might consider referencing these web sites for basic ideas on what individuals can do to start to make a difference. 1) 2) 3) Teaching Tips 1. You might surprise your class by noting that more people are alive today than have ever lived before and died. An examination of Figure reveals why this is true. 2. The US government’s Census Bureau sponsors a US and World population clock at ( ) for the most recent estimates of US and world human populations. 3. Medicare and Social Security will be increasingly impacted as the US population ages. By contrast, you might want to discuss the occupational outlook for professions that will address the growing needs of the elderly and the opportunity to invest in companies that will capitalize on these changes. 4. The United States has an ecological footprint greater than the land of the United States. Consider asking your class to explain how this is possible, and what this means to other countries. If you spend some time doing various conversions, you will find that the average ecological footprint of a person in the United States is about equal to the area of 18 football fields with end zones. This was calculated using the following figures. a) 1 football field with end zones is square feet (360 x 160 feet) b) 1 acre = sq. feet c) acres = 1 hectare = 107,593 square feet d) 1.87 football fields in 1 hectare = 107,593 (1 hectare) sq. feet / sq. feet (football field with end zones) e) 17.6 football fields = 9.4 hectare x 1.87 football fields = average ecological footprint of each US citizen. 5. Many web resources are available for students to calculate their ecological footprint. A few of them are noted below.

The ecological footprint of the United States
Is 9.4 hectares per person Represents almost twice what the U.S. land and resources can support. The ecological impact of affluent nations is a problem of overconsumption, not overpopulation. Compared to a family in rural India, Americans have an abundance of possessions. Student Misconceptions and Concerns 1. Students may not appreciate the energy and effort that goes into the generation of their food and products they use daily. A simple analysis of packaging materials will reveal some of the daily investment in convenience. Consider some small task for your students to do to best estimate their ecological footprint. See Teaching Tip #5 below for a list of web sites where your students can calculate their ecological footprint. 2. We often grow tired and frustrated by the long list of problems caused by humans. Many feel helpless. You might consider referencing these web sites for basic ideas on what individuals can do to start to make a difference. 1) 2) 3) Teaching Tips 1. You might surprise your class by noting that more people are alive today than have ever lived before and died. An examination of Figure reveals why this is true. 2. The US government’s Census Bureau sponsors a US and World population clock at ( ) for the most recent estimates of US and world human populations. 3. Medicare and Social Security will be increasingly impacted as the US population ages. By contrast, you might want to discuss the occupational outlook for professions that will address the growing needs of the elderly and the opportunity to invest in companies that will capitalize on these changes. 4. The United States has an ecological footprint greater than the land of the United States. Consider asking your class to explain how this is possible, and what this means to other countries. If you spend some time doing various conversions, you will find that the average ecological footprint of a person in the United States is about equal to the area of 18 football fields with end zones. This was calculated using the following figures. a) 1 football field with end zones is square feet (360 x 160 feet) b) 1 acre = sq. feet c) acres = 1 hectare = 107,593 square feet d) 1.87 football fields in 1 hectare = 107,593 (1 hectare) sq. feet / sq. feet (football field with end zones) e) 17.6 football fields = 9.4 hectare x 1.87 football fields = average ecological footprint of each US citizen. 5. Many web resources are available for students to calculate their ecological footprint. A few of them are noted below.

Figure 19.22 Families in India (left) and the United States (right) display their possessions.

There is tremendous disparity in consumption throughout the world.
The world’s richest countries Have 20% of the global population Use 86% of the world’s resources The rest of the world Has 80% of the population Uses just 14% of global resources Student Misconceptions and Concerns 1. Students may not appreciate the energy and effort that goes into the generation of their food and products they use daily. A simple analysis of packaging materials will reveal some of the daily investment in convenience. Consider some small task for your students to do to best estimate their ecological footprint. See Teaching Tip #5 below for a list of web sites where your students can calculate their ecological footprint. 2. We often grow tired and frustrated by the long list of problems caused by humans. Many feel helpless. You might consider referencing these web sites for basic ideas on what individuals can do to start to make a difference. 1) 2) 3) Teaching Tips 1. You might surprise your class by noting that more people are alive today than have ever lived before and died. An examination of Figure reveals why this is true. 2. The US government’s Census Bureau sponsors a US and World population clock at ( ) for the most recent estimates of US and world human populations. 3. Medicare and Social Security will be increasingly impacted as the US population ages. By contrast, you might want to discuss the occupational outlook for professions that will address the growing needs of the elderly and the opportunity to invest in companies that will capitalize on these changes. 4. The United States has an ecological footprint greater than the land of the United States. Consider asking your class to explain how this is possible, and what this means to other countries. If you spend some time doing various conversions, you will find that the average ecological footprint of a person in the United States is about equal to the area of 18 football fields with end zones. This was calculated using the following figures. a) 1 football field with end zones is square feet (360 x 160 feet) b) 1 acre = sq. feet c) acres = 1 hectare = 107,593 square feet d) 1.87 football fields in 1 hectare = 107,593 (1 hectare) sq. feet / sq. feet (football field with end zones) e) 17.6 football fields = 9.4 hectare x 1.87 football fields = average ecological footprint of each US citizen. 5. Many web resources are available for students to calculate their ecological footprint. A few of them are noted below.

Figure 19.23 North America Europe Asia Africa South America Australia
Key > 5.4 global hectares per person 3.6–5.4 global hectares per person 1.8–3.6 global hectares per person 0.9–1.8 global hectares per person < 0.9 global hectares per person Insufficient data Figure World map with area corresponding to ecological footprint Figure 19.23

Evolution Connection: Humans as an Invasive Species
Pronghorn antelope Roamed the open plains and shrub deserts of North America millions of years ago Have a top speed of 97 km/h (60 mph) Are the fastest mammal on the continent Pronghorn speed is likely an adaptation to outrun American cheetahs, which went extinct about 10,000 years ago. Student Misconceptions and Concerns 1. Students may not appreciate the energy and effort that goes into the generation of their food and products they use daily. A simple analysis of packaging materials will reveal some of the daily investment in convenience. Consider some small task for your students to do to best estimate their ecological footprint. See Teaching Tip #5 below for a list of web sites where your students can calculate their ecological footprint. 2. We often grow tired and frustrated by the long list of problems caused by humans. Many feel helpless. You might consider referencing these web sites for basic ideas on what individuals can do to start to make a difference. 1) 2) 3) Teaching Tips 1. You might surprise your class by noting that more people are alive today than have ever lived before and died. An examination of Figure reveals why this is true. 2. The US government’s Census Bureau sponsors a US and World population clock at ( ) for the most recent estimates of US and world human populations. 3. Medicare and Social Security will be increasingly impacted as the US population ages. By contrast, you might want to discuss the occupational outlook for professions that will address the growing needs of the elderly and the opportunity to invest in companies that will capitalize on these changes. 4. The United States has an ecological footprint greater than the land of the United States. Consider asking your class to explain how this is possible, and what this means to other countries. If you spend some time doing various conversions, you will find that the average ecological footprint of a person in the United States is about equal to the area of 18 football fields with end zones. This was calculated using the following figures. a) 1 football field with end zones is square feet (360 x 160 feet) b) 1 acre = sq. feet c) acres = 1 hectare = 107,593 square feet d) 1.87 football fields in 1 hectare = 107,593 (1 hectare) sq. feet / sq. feet (football field with end zones) e) 17.6 football fields = 9.4 hectare x 1.87 football fields = average ecological footprint of each US citizen. 5. Many web resources are available for students to calculate their ecological footprint. A few of them are noted below. © 2010 Pearson Education, Inc.

Figure 19.24 A pronghorn antelope racing across the North American plains

About 10,000 years ago Changes in the biotic and abiotic environments happened too rapidly for an evolutionary response Many large North American mammals, in addition to American cheetahs, went extinct, including Lions Saber-toothed cats Towering short-faced bears Student Misconceptions and Concerns 1. Students may not appreciate the energy and effort that goes into the generation of their food and products they use daily. A simple analysis of packaging materials will reveal some of the daily investment in convenience. Consider some small task for your students to do to best estimate their ecological footprint. See Teaching Tip #5 below for a list of web sites where your students can calculate their ecological footprint. 2. We often grow tired and frustrated by the long list of problems caused by humans. Many feel helpless. You might consider referencing these web sites for basic ideas on what individuals can do to start to make a difference. 1) 2) 3) Teaching Tips 1. You might surprise your class by noting that more people are alive today than have ever lived before and died. An examination of Figure reveals why this is true. 2. The US government’s Census Bureau sponsors a US and World population clock at ( ) for the most recent estimates of US and world human populations. 3. Medicare and Social Security will be increasingly impacted as the US population ages. By contrast, you might want to discuss the occupational outlook for professions that will address the growing needs of the elderly and the opportunity to invest in companies that will capitalize on these changes. 4. The United States has an ecological footprint greater than the land of the United States. Consider asking your class to explain how this is possible, and what this means to other countries. If you spend some time doing various conversions, you will find that the average ecological footprint of a person in the United States is about equal to the area of 18 football fields with end zones. This was calculated using the following figures. a) 1 football field with end zones is square feet (360 x 160 feet) b) 1 acre = sq. feet c) acres = 1 hectare = 107,593 square feet d) 1.87 football fields in 1 hectare = 107,593 (1 hectare) sq. feet / sq. feet (football field with end zones) e) 17.6 football fields = 9.4 hectare x 1.87 football fields = average ecological footprint of each US citizen. 5. Many web resources are available for students to calculate their ecological footprint. A few of them are noted below.

Although still hotly disputed, many scientists think that the extinction at the end of the ice age about 10,000 years ago was in part the result of the human invasion of North America, with humans serving as the damaging invasive species. Like other invasive species, humans may change the environment at an accelerating pace and too rapidly for other species to evolve and survive. Student Misconceptions and Concerns 1. Students may not appreciate the energy and effort that goes into the generation of their food and products they use daily. A simple analysis of packaging materials will reveal some of the daily investment in convenience. Consider some small task for your students to do to best estimate their ecological footprint. See Teaching Tip #5 below for a list of web sites where your students can calculate their ecological footprint. 2. We often grow tired and frustrated by the long list of problems caused by humans. Many feel helpless. You might consider referencing these web sites for basic ideas on what individuals can do to start to make a difference. 1) 2) 3) Teaching Tips 1. You might surprise your class by noting that more people are alive today than have ever lived before and died. An examination of Figure reveals why this is true. 2. The US government’s Census Bureau sponsors a US and World population clock at ( ) for the most recent estimates of US and world human populations. 3. Medicare and Social Security will be increasingly impacted as the US population ages. By contrast, you might want to discuss the occupational outlook for professions that will address the growing needs of the elderly and the opportunity to invest in companies that will capitalize on these changes. 4. The United States has an ecological footprint greater than the land of the United States. Consider asking your class to explain how this is possible, and what this means to other countries. If you spend some time doing various conversions, you will find that the average ecological footprint of a person in the United States is about equal to the area of 18 football fields with end zones. This was calculated using the following figures. a) 1 football field with end zones is square feet (360 x 160 feet) b) 1 acre = sq. feet c) acres = 1 hectare = 107,593 square feet d) 1.87 football fields in 1 hectare = 107,593 (1 hectare) sq. feet / sq. feet (football field with end zones) e) 17.6 football fields = 9.4 hectare x 1.87 football fields = average ecological footprint of each US citizen. 5. Many web resources are available for students to calculate their ecological footprint. A few of them are noted below.

Chapter 19 Population Ecology.

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Chapter 19 Population Ecology.

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