Chapter 36 Population Ecology Power Point Lectures for

Chapter 36 Population Ecology Power. Point Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey © 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko

Figure 36. 0_2 Emperor penguins

Introduction § Individual emperor penguins face the rigors of the Antarctic climate and have special adaptations, including a – downy underlayer of feathers for insulation and – thick layer of fat for energy storage and insulation. § The entire population of emperor penguins reflects group characteristics, including the – survivorship of chicks and – growth rate of the population. © 2012 Pearson Education, Inc.

Introduction § Population ecologists study natural population – structure and – dynamics. © 2012 Pearson Education, Inc.

Figure 36. 0_1 Chapter 36: Big Ideas 1985 Male Population Structure and Dynamics Female The Human Population

POPULATION STRUCTURE AND DYNAMICS © 2012 Pearson Education, Inc.

36. 1 Population ecology is the study of how and why populations change § A population is a group of individuals of a single species that occupy the same general area. § Individuals in a population – rely on the same resources, – are influenced by the same environmental factors, and – are likely to interact and breed with one another. © 2012 Pearson Education, Inc.

36. 1 Population ecology is the study of how and why populations change § A population can be described by the – number and – distribution of individuals. § Population dynamics, the interactions between biotic and abiotic factors, cause variations in population sizes. © 2012 Pearson Education, Inc.

36. 1 Population ecology is the study of how and why populations change § Population ecology is concerned with – the changes in population size and – factors that regulate populations over time. § Populations – increase through birth and immigration to an area and – decrease through death and emigration out of an area. © 2012 Pearson Education, Inc.

36. 2 Density and dispersion patterns are important population variables § Population density is the number of individuals of a species per unit area or volume. § Examples of population density include the – number of oak trees per square kilometer in a forest or – number of earthworms per cubic meter in forest soil. § Ecologists use a variety of sampling techniques to estimate population densities. © 2012 Pearson Education, Inc.

36. 2 Density and dispersion patterns are important population variables § Within a population’s geographic range, local densities may vary greatly. § The dispersion pattern of a population refers to the way individuals are spaced within their area. © 2012 Pearson Education, Inc.

36. 2 Density and dispersion patterns are important population variables § Dispersion patterns can be – clumped, – uniform, or – random. § In a clumped pattern – resources are often unequally distributed and – individuals are grouped in patches. © 2012 Pearson Education, Inc.

Figure 36. 2 A Clumped dispersion of ochre sea stars at low tide

Clumped dispersion of schooling fish

36. 2 Density and dispersion patterns are important population variables § In a uniform pattern, individuals are – most likely interacting and – equally spaced in the environment. © 2012 Pearson Education, Inc.

Uniform dispersion of nesting king penguins

36. 2 Density and dispersion patterns are important population variables § In a random pattern of dispersion, the individuals in a population are spaced in an unpredictable way. © 2012 Pearson Education, Inc.

36. 3 Life tables track survivorship in populations § Life tables track survivorship, the chance of an individual in a given population surviving to various ages. © 2012 Pearson Education, Inc.

Table 36. 3

36. 3 Life tables track survivorship in populations § Survivorship curves plot survivorship as the proportion of individuals from an initial population that are alive at each age. § There are three main types of survivorship curves. – Type III © 2012 Pearson Education, Inc.

Percentage of survivors (log scale) Figure 36. 3 100 I 10 II 1 III 0. 1 0 50 Percentage of maximum life span 100

36. 4 Idealized models predict patterns of population growth There are two models of population growth § The exponential growth model § The logistic growth model © 2012 Pearson Education, Inc.

36. 4 Idealized models predict patterns of population growth The exponential growth model § Explains the rate of population increase under ideal conditions. § It can be calculated using the following equation § G = r. N, in which – G is the growth rate of the population, – N is the population size, and – r is the per capita rate of increase (the average contribution of each individual to population growth). § Eventually, one or more limiting factors will restrict population growth. © 2012 Pearson Education, Inc.

Figure 36. 4 A Population size (N) Exponential growth of rabbits 500 450 400 350 300 250 200 150 100 50 0 0 1 2 3 4 5 6 7 8 9 10 11 12 Time (months)

Table 36. 4 A

36. 4 Idealized models predict patterns of population growth The logistic growth model § Is a description of idealized population growth that is slowed by limiting factors as the population size increases. § To model logistic growth, the formula for exponential growth, r. N, is multiplied by an expression that describes the effect of limiting factors on an increasing population size. § K stands for carrying capacity, the maximum population size a particular environment can sustain. © 2012 Pearson Education, Inc.

Breeding male fur seals (thousands) Figure 36. 4 B 10 Growth of a population of fur seals 8 6 4 2 0 1915 1925 1935 Year 1945

Figure 36. 4 C Number of individuals (N) Logistic growth and exponential growth compared G r. N K 0 G Time (K N) r. N K

Table 36. 4 B

36. 5 Multiple factors may limit population growth § The logistic growth model predicts that population growth will slow and eventually stop as population density increases. § At increasing population densities, densitydependent rates result in – declining births and – increases in deaths. § Multiple factors may limit population growth © 2012 Pearson Education, Inc.

Figure 36. 5 A Decreasing birth rate with increasing density in a population of great tits Average clutch size 12 11 10 9 8 0 10 20 30 40 50 60 70 80 Number of breeding pairs 90

36. 5 Multiple factors may limit population growth § Limiting factors may include food, nutrients, retreats for safety, or nesting sites. § Intraspecific competition is – competition between individuals of the same species for limited resources and – is a density-dependent factor that limits growth in natural populations. © 2012 Pearson Education, Inc.

Decreasing survival rates with increasing density in a population of flour beetles 100 80 Survivors (%) Figure 36. 5 B 60 40 20 40 60 80 100 120 Density (beetles/0. 5 g flour)

36. 5 Multiple factors may limit population growth § In many natural populations, abiotic factors such as weather may affect population size well before density-dependent factors become important. § Density-independent factors are unrelated to population density. These may include – fires, – storms, – habitat destruction by human activity, or – seasonal changes in weather (for example, in aphids). © 2012 Pearson Education, Inc.

Figure 36. 5 C Number of aphids Weather change as a density-independent factor limiting aphid population growth Exponential growth Apr May Jun Sudden decline Jul Aug Sep Oct Nov Dec Month

36. 6 Some populations have “boom-and-bust” cycles § Some populations fluctuate in density with regularity. § Boom-and-bust cycles may be due to – food shortages or – predator-prey interactions. © 2012 Pearson Education, Inc.

Figure 36. 6 160 Snowshoe hare 120 9 Lynx 80 6 40 3 0 0 1850 1875 Year 1900 1925 Lynx population size (thousands) Hare population size (thousands) Population cycles of the snowshoe hare and the lynx

36. 7 EVOLUTION CONNECTION: Evolution shapes life histories § The traits that affect an organism’s schedule of reproduction and death make up its life history. § Key life history traits include – age of first reproduction, – frequency of reproduction, – number of offspring, and – amount of parental care. © 2012 Pearson Education, Inc.

36. 7 EVOLUTION CONNECTION: Evolution shapes life histories § Populations with so-called r-selected life history traits – produce more offspring and – grow rapidly in unpredictable environments. § Populations with K-selected traits – raise fewer offspring and – maintain relatively stable populations. § Most species fall between these two extremes. © 2012 Pearson Education, Inc.

36. 8 CONNECTION: Principles of population ecology have practical applications § Sustainable resource management involves – harvesting crops and – eliminating damage to the resource. § The cod fishery off Newfoundland – was overfished, – collapsed in 1992, and – still has not recovered. § Resource managers use population ecology to determine sustainable yields. © 2012 Pearson Education, Inc.

Figure 36. 8 Yield (thousands of metric tons) Collapse of northern cod fishery off Newfoundland 900 800 700 600 500 400 300 200 100 0 1960 1970 1980 1990 2000

THE HUMAN POPULATION © 2012 Pearson Education, Inc.

36. 9 The human population continues to increase, but the growth rate is slowing § The human population – grew rapidly during the 20 th century and – currently stands at about 7 billion. © 2012 Pearson Education, Inc.

100 80 10 Population increase 8 60 6 40 4 Total population size 20 1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000 2050 Year 2 0 Total population (in billions) Annual increase (in millions) Figure 36. 9 A

36. 9 The human population continues to increase, but the growth rate is slowing § The demographic transition – Is the shift in population – from high birth and death rates – to low birth and death rates, and – has lowered the rate of growth in developed countries. © 2012 Pearson Education, Inc.

Figure 36. 9 B Demographic transition in Mexico Birth or death rate per 1, 000 population 50 40 30 Rate of increase 20 10 Birth rate Death rate 0 1900 1925 1950 1975 2000 2025 2050 Year

36. 9 The human population continues to increase, but the growth rate is slowing § In the developing nations – death rates have dropped, – birth rates are still high, and – these populations are growing rapidly. © 2012 Pearson Education, Inc.

Table 36. 9

36. 9 The human population continues to increase, but the growth rate is slowing § The age structure of a population – is the proportion of individuals in different age groups and – affects the future growth of the population. © 2012 Pearson Education, Inc.

36. 9 The human population continues to increase, but the growth rate is slowing § Population momentum is the continued growth that occurs – despite reduced fertility and – as a result of girls in the 0– 14 age group of a previously expanding population reaching their childbearing years. © 2012 Pearson Education, Inc.

36. 10 CONNECTION: Age structures reveal social and economic trends § Age-structure diagrams reveal – a population’s growth trends and – social conditions. © 2012 Pearson Education, Inc.

Figure 36. 10 Age structures for the United States in 1985, 2010 (estimated), and 2035 (projected) Age Birth years 85 80– 84 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 0– 4 1985 Male Female before 1901– 1905 1906– 10 1911– 15 1916– 20 1921– 25 1926– 30 1931– 35 1936– 40 1941– 45 1946– 50 1951– 55 1956– 60 1961– 65 1966– 70 1971– 75 1976– 80 1981– 85 Birth years 2010 Male Female before 1926– 30 1931– 35 1936– 40 1941– 45 1946– 50 1951– 55 1956– 60 1961– 65 1966– 70 1971– 75 1976– 80 1981– 85 1986– 90 1991– 95 1996– 2000 2001– 2005 2006– 2010 12 10 8 6 4 2 0 2 4 6 8 10 12 Population in millions Total population size 238, 466, 283 Birth years 2035 Male Female before 1951– 55 1956– 60 1961– 65 1966– 70 1971– 75 1976– 80 1981– 85 1986– 90 1991– 95 1996– 2000 2001– 05 2006– 10 2011– 15 2016– 20 2021– 25 2026– 30 2031– 35 12 10 8 6 4 2 0 2 4 6 8 10 12 Estimated population in millions Total population size 310, 232, 863 12 10 8 6 4 2 0 2 4 6 8 10 12 Projected population in millions Total population size 389, 531, 156

Figure 36. 10_1 Age Birth years 1985 Male Female before 1901 85 80– 84 1901– 1905 75– 79 1906– 10 1911– 15 70– 74 1916– 20 65– 69 1921– 25 60– 64 1926– 30 55– 59 1931– 35 50– 54 1936– 40 45– 49 1941– 45 40– 44 1946– 50 35– 39 30– 34 1951– 55 25– 29 1956– 60 20– 24 1961– 65 15– 19 1966– 70 10– 14 1971– 75 1976– 80 5– 9 1981– 85 0– 4 12 10 8 6 4 2 0 2 4 6 8 10 12 Population in millions Total population size 238, 466, 283

Figure 36. 10_2 Age Birth years 85 80– 84 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 0– 4 2010 Male Female before 1926– 30 1931– 35 1936– 40 1941– 45 1946– 50 1951– 55 1956– 60 1961– 65 1966– 70 1971– 75 1976– 80 1981– 85 1986– 90 1991– 95 1996– 2000 2001– 2005 2006– 2010 12 10 8 6 4 2 0 2 4 6 8 10 12 Estimated population in millions Total population size 310, 232, 863

Figure 36. 10_3 Age Birth years 2035 Male Female before 1951 85 80– 84 1951– 55 75– 79 1956– 60 70– 74 1961– 65 1966– 70 65– 69 1971– 75 60– 64 1976– 80 55– 59 1981– 85 50– 54 1986– 90 45– 49 40– 44 1991– 95 35– 39 1996– 2000 30– 34 2001– 05 25– 29 2006– 10 20– 24 2011– 15 15– 19 2016– 20 10– 14 2021– 25 5– 9 2026– 30 0– 4 2031– 35 12 10 8 6 4 2 0 2 4 6 8 10 12 Projected population in millions Total population size 389, 531, 156

36. 11 CONNECTION: An ecological footprint is a measure of resource consumption § The U. S. Census Bureau projects a global population of – 8 billion people within the next 20 years and – 9. 5 billion by mid-21 st century. § Do we have sufficient resources to sustain 8 or 9 billion people? § To accommodate all the people expected to live on our planet by 2025, the world will have to double food production. © 2012 Pearson Education, Inc.

36. 11 CONNECTION: An ecological footprint is a measure of resource consumption § An ecological footprint is an estimate of the amount of land required to provide the raw materials an individual or a nation consumes, including – food, fuel, water, housing, and waste disposal. § Includes how much cropland, Grazing Lands, Forests, Fishing grounds, etc. are required © 2012 Pearson Education, Inc.

Ecological Footprints Source: Global Footprint Network

36. 11 CONNECTION: An ecological footprint is a measure of resource consumption § Unites States has a huge ecological foot print – The United States - 9. 4 gha person. – India – less than 0. 9 ha person § US can support only 5 gha person. – Thus US has a large ecological deficit Copyright © 2009 Pearson Education, Inc.

36. 11 CONNECTION: An ecological footprint is a measure of resource consumption § The United States – has a very large ecological footprint, much greater than its own land, and – is running on a large ecological deficit. § Some researchers estimate that – if everyone on Earth had the same standard of living as people living in the United States, – we would need the resources of 4. 5 planet Earths. © 2012 Pearson Education, Inc.

Figure 36. 11 A

Figure 36. 11 A_1

Figure 36. 11 A_2

Figure 36. 11 B Ecological Footprints (gha per capita) 0– 1. 5– 3. 0– 4. 5– 6. 0– 7. 5– 9. 0– 10. 5 Insufficient data

Environmental Bankruptcy “Environmental bankruptcy, as with corporate bankruptcy, can happen very slowly, then all of a sudden. This is what we face unless we slow down, then reverse the damage. We’re running short on fresh water, topsoil, fisheries, wetlands – all our planet’s natural systems and resources that support business, and life, including our own. We’re now using the resources of one-and-a-half planets on our one and only planet” -Advertisement on Patagonia Jacket http: //www. marcgunther. com/2011/11/27/maybe-the-best-retailad-ever/

Ecological Footprint assignment § If everyone in the world lived your lifestyle, how many earths would we need? ? ? § Your Ecological Footprint assignment will give you the answer