Copyright © 2009 Pearson Education, Inc. PowerPoint Lectures for Biology: Concepts & Connections, Sixth Edition Campbell, Reece, Taylor, Simon, and Dickey Chapter 36 Population Ecology Lecture by Brian R. Shmaefsky

Copyright © 2009 Pearson Education, Inc. Introduction: A Tale of Two Fishes  Population ecology is concerned with –Changes in population size –Factors that regulate populations over time  It helps explain the biodiversity of an environment

Copyright © 2009 Pearson Education, Inc.  Ecologists learn the structure and dynamics of natural populations  With this information they are better equipped to –Develop sustainable food sources –Assess the impact of human activities –Balance human needs with the conservation of biodiversity and resources Introduction: A Tale of Two Fishes

Copyright © 2009 Pearson Education, Inc. POPULATION STRUCTURE AND DYNAMICS

Copyright © 2009 Pearson Education, Inc Population ecology is the study of how and why populations change  Population –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 –Are likely to interact and breed with one another

Copyright © 2009 Pearson Education, Inc.  A population can be described by the number and distribution of individuals  Population dynamics is the interactions between –Biotic and abiotic factors  It is the cause of variation in population sizes –A population increases through birth and immigration –Death and emigration out of an area decrease the population 36.1 Population ecology is the study of how and why populations change

Copyright © 2009 Pearson Education, Inc 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 –The number of oak trees per square kilometer in a forest –The number of earthworms per cubic meter in forest soil  Ecologists use a variety of sampling techniques to estimate population densities

Copyright © 2009 Pearson Education, Inc.  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 36.2 Density and dispersion patterns are important population variables Video: Flapping Geese (clumped) Video: Albatross Courtship (uniform) Video: Prokaryotic Flagella (Salmonella typhimurium) (random)

Copyright © 2009 Pearson Education, Inc.  The dispersion pattern of a population refers to the way individuals are spaced within their area  Dispersion patterns can be –Clumped –Uniform –Random 36.2 Density and dispersion patterns are important population variables

Copyright © 2009 Pearson Education, Inc.  In a clumped pattern individuals are grouped in patches 36.2 Density and dispersion patterns are important population variables

Copyright © 2009 Pearson Education, Inc.  In a uniform pattern individuals are equally spaced in the environment 36.2 Density and dispersion patterns are important population variables

Copyright © 2009 Pearson Education, Inc.  In a random pattern of dispersion, the individuals in a population are spaced in an unpredictable way 36.2 Density and dispersion patterns are important population variables

Copyright © 2009 Pearson Education, Inc Life tables track survivorship in populations  Life tables track survivorship over the life span of individuals in a population  Survivorship curves plot the proportion of individuals alive at each age –Type I –Type II –Type III

Percentage of maximum life span Percentage of survivors (log scale) III II I

Copyright © 2009 Pearson Education, Inc Idealized models predict patterns of population growth  Exponential growth model –The rate of population increases under ideal conditions –Calculated using the equation G = rN –G is the growth rate of the population –N is the population size –r is the per capita rate of increase

Time (months) Population size (N)

Copyright © 2009 Pearson Education, Inc.  Logistic growth model –This growth model takes into account limiting factors –Limiting factors are environmental factors that restrict population growth –Formula 36.4 Idealized models predict patterns of population growth

Year Breeding male fur seals (thousands)

Year Breeding male fur seals (thousands)

Copyright © 2009 Pearson Education, Inc.  Idealized models describe two kinds of population growth –Exponential growth –Logistic growth 36.4 Idealized models predict patterns of population growth

Time Number of individuals (N) 0 K G = rN (K – N) K

Copyright © 2009 Pearson Education, Inc Multiple factors may limit population growth  The logistic growth model –Population growth slows and ceases as population density increases –Increasing population density results in a decrease in birth rate, an increase in death rate, or both

Density of females Clutch size

Copyright © 2009 Pearson Education, Inc.  Abiotic factors may reduce population size before other limiting factors become important 36.5 Multiple factors may limit population growth

Apr MayJun Jul AugSepOct Nov Dec Number of aphids Exponential growth Sudden decline

Copyright © 2009 Pearson Education, Inc.  Most populations fluctuate in numbers 36.5 Multiple factors may limit population growth

Time (years) Number of females

Copyright © 2009 Pearson Education, Inc Some populations have “boom-and-bust” cycles  Some populations fluctuate in density with regularity  Boom-and-bust cycles –Food shortages –Predator-prey interactions

Lynx Snowshoe hare Lynx population size (thousands) Hare population size (thousands) Year

Copyright © 2009 Pearson Education, Inc EVOLUTION CONNECTION: Evolution shapes life histories  Life history –Series of events from birth to death  r/K selection –r-selective traits –K-selective traits

MalesFemales Experimental transplant of guppies Predator: Killifish; preys mainly on small guppies Guppies: Larger at sexual maturity than those in pike-cichlid pools Pools with killifish, but no guppies prior to transplant Predator: Pike-cichlid preys mainly on large guppies Guppies: Smaller at sexual maturity than those in killifish pools 11 years later Mass of guppies at maturity (mg) Age of guppies at maturity (days) MalesFemales Control: Guppies from pools with pike-cichlids as predators Experimental: Guppies transplanted to pools with killifish as predators

Predator: Killifish; preys mainly on small guppies Experimental transplant of guppies Guppies: Larger at sexual maturity than those in pike-cichlid pools Pools with killifish, but no guppies prior to transplant Predator: Pike-cichlid preys mainly on large guppies Guppies: Smaller at sexual maturity than those in killifish pools

MalesFemales Mass of guppies at maturity (mg) MalesFemales Age of guppies at maturity (days) Control: Guppies from pools with pike-cichlids as predators Experimental: Guppies transplanted to pools with killifish as predators 11 years later

Copyright © 2009 Pearson Education, Inc CONNECTION: Principles of population ecology have practical applications  Sustainable resource management –Maximum sustained yield

1960 Yield (thousands of metric tons)

Copyright © 2009 Pearson Education, Inc. THE HUMAN POPULATION

Copyright © 2009 Pearson Education, Inc The human population continues to increase, but the growth rate is slowing  Human population is expected to continue increasing for several decades  95% of the increase is in developing nations

1500 Year Population increase Total population size Total population (in billions) Annual increase (in millions)

Year Birth rate Death rate Rate of increase (r) Birth or death rate per 1,000 population

Copyright © 2009 Pearson Education, Inc.  Population momentum of Mexico 36.9 The human population continues to increase, but the growth rate is slowing

Age Male Female Population in millions Total population size = 68,347,479 Population in millions Total population size = 106,202,903 FemaleMale Female Male Population in millions Total population size = 135,172,

Age Population in millions Total population size = 68,347, Male Female

Age Population in millions Total population size = 106,202,903 Female Male 2005

Age Female Male Population in millions Total population size = 135,172,155

Copyright © 2009 Pearson Education, Inc CONNECTION: Age structures reveal social and economic trends  Age structure diagram –Reveals a population’s growth trends

Age 1980 Birth years Male Female Birth years Male Female Birth years Male Female 80+ before 1900 before 1926 before Population in millions Total population size = 363,811,435 Population in millions Total population size = 295,734, Population in millions Total population size = 227,726,463

1980 Age Birth years Male Female before Population in millions Total population size = 227,726,463

Age Birth years Male Female Population in millions Total population size = 295,734,134 before

Age Birth years Male Female Population in millions Total population size = 363,811, before

Copyright © 2009 Pearson Education, Inc CONNECTION: An ecological footprint is a measure of resource consumption  U.S. Census Bureau projection –8 billion people within the next 20 years –9.5 billion by mid-21st century

Copyright © 2009 Pearson Education, Inc.  Ecological footprint helps understand resource availability and usage  The United States has a –Big ecological footprint –Large ecological deficit CONNECTION: An ecological footprint is a measure of resource consumption

North America Europe Asia Africa > 5.4 global ha per person 3.6–5.4 global ha per person 1.8–3.6 global ha per person 0.9–1.8 global ha per person < 0.9 global ha per person Insufficient data South America Australia

Few large offspring, low mortality until old age Many small offspring, high mortality Percentage of maximum life span Percentage of survivors III II I

G = rN (K  N)(K  N) K

Time Birth or death rate IIIIVI II

Copyright © 2009 Pearson Education, Inc. You should now be able to 1.Explain the factors that determine the characteristics of a population 2.Describe exponential growth and the factors that produce logistic growth of a population 3.Explain the limiting factors that influence population growth 4.Distinguish between r- and K-strategies 5.Describe and give examples of the different types of life histories

Copyright © 2009 Pearson Education, Inc. 6.Explain the factors the determine human population growth 7.Describe the concept of ecological footprint You should now be able to