© 2010 Pearson Education, Inc. Lectures by Chris C. Romero, updated by Edward J. Zalisko PowerPoint ® Lectures for Campbell Essential Biology, Fourth Edition.

© 2010 Pearson Education, Inc. Lectures by Chris C. Romero, updated by Edward J. Zalisko PowerPoint ® Lectures for Campbell Essential Biology, Fourth Edition – Eric Simon, Jane Reece, and Jean Dickey Campbell Essential Biology with Physiology, Third Edition – Eric Simon, Jane Reece, and Jean Dickey 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. © 2010 Pearson Education, Inc.

Figure 19.00

© 2010 Pearson Education, Inc. 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

© 2010 Pearson Education, Inc. 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

© 2010 Pearson Education, Inc. AN OVERVIEW OF POPULATION ECOLOGY Population ecology is the study of factors that affect population: –Density –Growth A population is a group of individuals of a single species that occupy the same general area.

Figure 19.1

© 2010 Pearson Education, Inc. 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 (km 3 ) of a lake –The number of oak trees per square kilometer (km 2 ) in a forest –The number of nematodes per cubic meter (m 3 ) in a forest’s soil Population Density

© 2010 Pearson Education, Inc. 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

Figure 19.2

© 2010 Pearson Education, Inc. 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 Population Age Structure

11 Percent of population 01020304050 1 22 3 4 5 6 7 8 9 10 Age (years) Figure 19.3

Percent of population 0 Age (years) 1020304050 1 2 3 4 5 6 7 8 9 10 11 Figure 19.3a

Figure 19.3b

Table 19.1

Percentage of maximum life span 050100 0.1 1 10 100 Percentage of survivors (log scale) III II I Figure 19.4

© 2010 Pearson Education, Inc. 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

Table 19.2

Dandelions have an opportunistic life history Table 19.2a

Elephants have an equilibrial life history Table 19.2b

The Exponential Growth Model: The Ideal of an Unlimited Environment Exponential population growth describes the expansion of a population in an ideal and unlimited environment. © 2010 Pearson Education, Inc.

Time (months) Population size (N) 0123456789101112 0 50 100 150 200 250 300 350 400 450 500 Figure 19.5

Figure 19.5a

© 2010 Pearson Education, Inc. 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

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 © 2010 Pearson Education, Inc.

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.

Year 1915192519351945 0 2 4 6 8 10 Breeding male fur seals (thousands) Figure 19.6

Figure 19.6a

Exponential growth Logistic growth Time Carrying capacity 0 Number of individuals 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. © 2010 Pearson Education, Inc.

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. Video: Wolves Agonistic Behavior Video: Snake Ritual Wrestling Video: Chimp Agonistic Behavior

Number of breeding pairs Average clutch size (a) Decreasing birth rate with increasing density in a population of great tits 0102030405060708090 8 9 10 11 12 Figure 19.8a

Figure 19.8aa

Density (beetles/0.5 g flour) 020406080100120 20 40 60 80 100 Survivors (%) (b) Decreasing survival rates with increasing density in a population of flour beetles Figure 19.8b

Figure 19.8ba

Figure 19.9

© 2010 Pearson Education, Inc. Density-Independent Factors Density-independent factors –Are population-limiting factors whose intensity is unrelated to population density –Include abiotic factors such as –Fires –Floods –Storms Video: Giraffe Courtship Ritual Video: Blue-footed Boobies Courtship Ritual Video: Albatross Courtship Ritual

Exponential growth Sudden decline AprMayJunJulAugSepOctNovDec Number of aphids Figure 19.10

Figure 19.10a

© 2010 Pearson Education, Inc. 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 –Density-independent factors –Density-dependent factors

Snowshoe hare Lynx Year 18501900 0 3 6 9 0 40 80 120 160 Hare population (thousands) Lynx population (thousands) Figure 19.11

Lynx Year 18501900 0 3 6 9 0 40 80 120 160 Hare population (thousands) Lynx population (thousands) Snowshoe hare Figure 19.11a

Figure 19.11b

© 2010 Pearson Education, Inc. 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

© 2010 Pearson Education, Inc. Conservation of Endangered Species 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

© 2010 Pearson Education, Inc. 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

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 19.12

A red-cockaded woodpecker perches at the entrance to its nest in a long-leaf pine tree. Figure 19.12a

High, dense undergrowth impedes the woodpeckers’ access to feeding grounds. Figure 19.12b

Low undergrowth offers birds a clear flight path between nest sites and feeding grounds. Figure 19.12c

© 2010 Pearson Education, Inc. 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

19601970198019902000 0 100 200 300 400 500 600 700 800 900 Yield (thousands of metric tons) Figure 19.13

© 2010 Pearson Education, Inc. 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.

© 2010 Pearson Education, Inc. 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

Figure 19.14

Figure 19.15

Figure 19.15a

Figure 19.15b

© 2010 Pearson Education, Inc. 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

The Process of Science: Can Biological Control Defeat Kudzu? Kudzu –Is an invasive Asian vine –Covers about 12,000 square miles of the southeastern United States –Has a range limited by cold winters © 2010 Pearson Education, Inc.

Figure 19.16

© 2010 Pearson Education, Inc. 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.

© 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.

© 2010 Pearson Education, Inc. 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.

Untreated Treatment Wetting agent only Spores (2  10 7 /ml)  wetting agent Spores (2  10 6 /ml)  wetting agent Spores (2  10 7 /ml)  water Spores (2  10 6 /ml)  water Mortality (%) 0 020406080100 Figure 19.17

Figure 19.17a

© 2010 Pearson Education, Inc. 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

Figure 19.18

Figure 19.18a

Figure 19.18b

© 2010 Pearson Education, Inc. 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

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 © 2010 Pearson Education, Inc.

The world’s population began to grow exponentially in the 1900s due to advances in –Nutrition –Sanitation –Health care Blast Animation: Population Dynamics

Annual increase (millions) Population increase Total population size Year Total population (billions) 150015501600170018001650175018501950190020002050 20 40 60 80 100 0 2 4 6 8 10 Figure 19.19

© 2010 Pearson Education, Inc. 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

Table 19.3

© 2010 Pearson Education, Inc. 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 Age Structures

198520102035 FemaleMale FemaleMale FemaleMale 80  75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 20–24 25–29 15–19 10–14 5–9 0–4 543210123455432101234554321012345 Population in millions Total population size  139,457,070 Population in millions Total population size  112,468,855 Population in millions Total population size  76,767,225 Age Figure 19.20

1985 Male Female Age Population in millions Total population size  76,767,225 80  75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 55432104321 0–4 Figure 19.20a

2010 Male Female Age Population in millions Total population size  112,468,855 80  75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 55432104321 0–4 Figure 19.20b

2035 Male Female Age Population in millions Total population size  139,457,070 80  75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 55432104321 0–4 Figure 19.20c

© 2010 Pearson Education, Inc. 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.

1983 20082033 Birth yearsMaleFemale before 1954 1954–58 1959–63 1964–68 1969–73 1974–78 1979–83 1984–88 1989–93 1994–98 1999–2003 2004–08 2009–13 2014–18 2024–28 2019–23 2029–33 1210864202468 12 10864202468 12 10864202468 12 Population in millions Total population size  383,116,539 Population in millions Total population size  305,548,183 Population in millions Total population size  234,307,207 Birth years MaleFemale Male Age 2004–08 1999–2003 1994–98 1989–93 1984–88 1979–83 1974–78 1969–73 1964–68 1959–63 1954–58 1949–53 1944–48 1939–43 1934–38 1929–33 before 1929 before 1904 1904–08 1909–13 1914–18 1919–23 1924–28 1929–33 1934–38 1939–43 1944–48 1949–53 1954–58 1959–63 1964–68 1969–73 1974–78 1979–83 0–4 5–9 10–14 15–19 20–24 25–29 30–34 35–39 40–44 45–49 50–54 55–59 60–64 65–69 70–74 75–79 80  Figure 19.21

1983 FemaleMaleBirth years Population in millions Total population size  234,307,207 1210864202468 12 1979–83 1974–78 1969–73 1964–68 1959–63 1954–58 1944–48 1939–43 1934–38 1929–33 1924–28 1919–23 1914–18 1949–53 1909–13 1904–08 before 1904 0–4 5–9 10–14 15–19 20–24 25–29 30–34 35–39 40–44 45–49 50–54 55–59 60–64 65–69 70–74 75–79 80  Age Figure 19.21a

2008 FemaleMale Birth years Population in millions Total population size  305,548,183 1210864202468 12 2004–08 before 1929 0–4 5–9 10–14 15–19 20–24 25–29 30–34 35–39 40–44 45–49 50–54 55–59 60–64 65–69 70–74 75–79 80  Age 1999–2003 1994–98 1989–93 1984–88 1979–83 1974–78 1969–73 1964–68 1959–63 1954–58 1949–53 1944–48 1939–43 1934–38 1929–33 Figure 19.21b

2033 FemaleMaleBirth years Population in millions Total population size  383,116,539 1210864202468 12 2029–33 before 1954 0–4 5–9 10–14 15–19 20–24 25–29 30–34 35–39 40–44 45–49 50–54 55–59 60–64 65–69 70–74 75–79 80  Age 2024–28 2019–23 2014–18 2009–13 2004–08 1999–2003 1994–98 1989–93 1984–88 1979–83 1974–78 1969–73 1964–68 1959–63 1954–58 Figure 19.21c

© 2010 Pearson Education, Inc. 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

© 2010 Pearson Education, Inc. 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.

Figure 19.22

Figure 19.22a

Figure 19.22b

© 2010 Pearson Education, Inc. 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

North America South America Africa Europe Asia 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 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. © 2010 Pearson Education, Inc.

Figure 19.24

© 2010 Pearson Education, Inc. 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

© 2010 Pearson Education, Inc. 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.

Percentage of maximum life span Percentage of survivors (log scale) 050100 Type I: most individuals survive to older age intervals Type II: survivorship constant over life span Type III: low survivorship at early age intervals 0.1 1 10 100 III II I Figure 19.UN01

1985 2033 FemaleMale FemaleBirth years Mexico, 1985 age structure United States, 2033 predicted age structure 1210864202468 12 54321012345 0–4 5–9 10–14 15–19 20–24 25–29 30–34 35–39 40–44 45–49 50–54 55–59 60–64 65–69 70–74 75–79 80  Age before 1954 1954–58 1959–63 1964–68 1969–73 1974–78 1979–83 1984–88 1989–93 1994–98 1999–2003 2004–08 2009–13 2014–18 2019–23 2024–28 2029–33 Figure 19.UN02

0 Figure 19.UN03

© 2010 Pearson Education, Inc. Lectures by Chris C. Romero, updated by Edward J. Zalisko PowerPoint ® Lectures for Campbell Essential Biology, Fourth Edition.

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© 2010 Pearson Education, Inc. Lectures by Chris C. Romero, updated by Edward J. Zalisko PowerPoint ® Lectures for Campbell Essential Biology, Fourth Edition.

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