Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 52 What is Population Ecology? What influences population density and distribution, age structure, and variations in population size?

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What processes impact populations? Figure 52.2 Births and immigration add individuals to a population. BirthsImmigration PopuIation size Emigration Deaths Deaths and emigration remove individuals from a population.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Populations have patterns of Dispersion (spacing of individuals) Compare the two patterns below and 1. Clumped 2. Uniform Figure 52.3a (a) Clumped. For many animals, such as these wolves, living in groups increases the effectiveness of hunting, spreads the work of protecting and caring for young, and helps exclude other individuals from their territory. Figure 52.3b (b) Uniform. Birds nesting on small islands, such as these king penguins on South Georgia Island in the South Atlantic Ocean, often exhibit uniform spacing, maintained by aggressive interactions between neighbors.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

How can you determine a population’s growth rate? Start with what’s coming in and out or birth rate (b) and death rate (m) How can you determine the rate of increase (r)? r = b-m (excluding….) So, the population growth equation is dN dt  rN Figure Birth rate Death rate Birth rate Death rate Year SwedenMexico Birth or death rate per 1,000 people

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What do Life Tables tell you? Table 52.1

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What does the survivorship curve show you? – What pattern do you see with the ground squirrel’s death rate? Figure Number of survivors (log scale) Age (years) Males Females

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Survivorship curves can be classified into three general types – Type I, Type II, and Type III Figure 52.5 I II III ,000 Percentage of maximum life span Number of survivors (log scale)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reproductive Rates Add reproductive patterns of a population Table 52.2

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reproduction is differential amongst species Some reproduce semelparity (once before death) others exhibit iteroparity (repeatedly) Figure 52.6 Figure 52.8a (a) Most weedy plants, such as this dandelion, grow quickly and produce a large number of seeds, ensuring that at least some will grow into plants and eventually produce seeds themselves.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings “Trade-offs” and Life Histories Organisms have finite resources Figure 52.7 Researchers in the Netherlands studied the effects of parental caregiving in European kestrels over 5 years. The researchers transferred chicks among nests to produce reduced broods (three or four chicks), normal broods (five or six), and enlarged broods (seven or eight). They then measured the percentage of male and female parent birds that survived the following winter. (Both males and females provide care for chicks.) EXPERIMENT The lower survival rates of kestrels with larger broods indicate that caring for more offspring negatively affects survival of the parents. CONCLUSION Reduced brood size Normal brood size Enlarged brood size Parents surviving the following winter (%) Male Female Does brood size lead to trade-offs between survival and reproduction for parents? For offspring? RESULTS

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Why do some plants produce a large number of small seeds? Figure 52.8a (a) Most weedy plants, such as this dandelion, grow quickly and produce a large number of seeds, ensuring that at least some will grow into plants and eventually produce seeds themselves.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings While others produce a moderate number of large seeds with larger stores of energy? Figure 52.8b (b) Some plants, such as this coconut palm, produce a moderate number of very large seeds. The large endosperm provides nutrients for the embryo, an adaptation that helps ensure the success of a relatively large fraction of offspring.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Exponential population growth – Results in a J-shaped curveEquation: – Ideal conditions like… Figure ,000 1,500 2,000 Number of generations Population size (N) dN dt  1.0N dN dt  0.5N dN dt  r max N

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Can exponential growth be maintained? The J-shaped curve of exponential growth – Is characteristic of some populations that are rebounding Figure Year 0 2,000 4,000 6,000 8,000 Elephant population

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The logistic growth Model equation – Includes K, the carrying capacity (the maximum population size the environment can support) dN dt  ( K  N ) K r max N

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A hypothetical example of logistic growth Table 52.3

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The logistic model of population growth – Produces a sigmoid (S-shaped) curve Figure dN dt  1.0N Exponential growth Logistic growth dN dt  1.0N 1,500  N 1,500 K  1, ,000 1,500 2,000 Number of generations Population size (N)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 52.13a Time (days) (a) A Paramecium population in the lab. The growth of Paramecium aurelia in small cultures (black dots) closely approximates logistic growth (red curve) if the experimenter maintains a constant environment. 1,000 Number of Paramecium/ml The Logistic Model and Real Populations The growth of laboratory populations of paramecia – Fits an S-shaped curve

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What happens when populations overshoot K? Figure 52.13b Time (days) Number of Daphnia/50 ml (b) A Daphnia population in the lab. The growth of a population of Daphnia in a small laboratory culture (black dots) does not correspond well to the logistic model (red curve). This population overshoots the carrying capacity of its artificial environment and then settles down to an approximately stable population size.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Why do some populations fluctuate greatly around K? Figure 52.13c Time (years) Number of females (c) A song sparrow population in its natural habitat. The population of female song sparrows nesting on Mandarte Island, British Columbia, is periodically reduced by severe winter weather, and population growth is not well described by the logistic model.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings K vs. R selection K-selection, or density-dependent selection – Selects for life history traits that are sensitive to population density – What population control factors are density- dependent? r-selection, or density-independent selection – Selects for life history traits that maximize reproduction

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings How do Density-dependent and density- independent factors impact populations? Figure 52.14a–c Density-dependent birth rate Density- dependent death rate Equilibrium density Density-dependent birth rate Density- independent death rate Equilibrium density Density- independent birth rate Density-dependent death rate Equilibrium density Population density Birth or death rate per capita (a) Both birth rate and death rate change with population density. (b) Birth rate changes with population density while death rate is constant. (c) Death rate changes with population density while birht rate is constant.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Competition for Resources is density ___________? – Competition can be intraspecific or interspecific – in a population it is _________________________ Figure 52.15a,b ,000 10,000 Average number of seeds per reproducing individual (log scale) Average clutch size Seeds planted per m 2 Density of females (a) Plantain. The number of seeds produced by plantain (Plantago major) decreases as density increases. (b) Song sparrow. Clutch size in the song sparrow on Mandarte Island, British Columbia, decreases as density increases and food is in short supply.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Territoritality is density ________________ Cheetahs use chemical signals to keep others out of territory – how does this limit their density? Figure 52.16

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Disease and Physiological stress are density- _______________ In dense populations – Pathogens can spread more rapidly – Animals will exhibit more stress – You expect __________ toxic waste Figure 52.17

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Predation is density _________________ As a prey population builds up you expect predator populations to________ Figure Year Lynx population size (thousands) Hare population size (thousands) Lynx Snowshoe hare

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Invertebrates have Extreme fluctuations in population size Figure Year , , ,000 Commercial catch (kg) of male crabs (log scale)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Stability and Fluctuation Are populations of large mammals stable over time? Metapopulations = groups of populations linked by immigration and emigration Figure Researchers regularly surveyed the population of moose on Isle Royale, Michigan, from 1960 to During that time, the lake never froze over, and so the moose population was isolated from the effects of immigration and emigration. FIELD STUDY CONCLUSION Year Moose population size ,000 1,500 2,000 2,500 Steady decline probably caused largely by wolf predation Dramatic collapse caused by severe winter weather and food shortage, leading to starvation of more than 75% of the population

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings High levels of immigration combined with higher survival – Can result in greater ________ in populations Figure Mandarte island Small islands Number of breeding females Year

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Global Human Population What do you notice about our trend? Figure B.C B.C B.C B.C B.C A.D. 0 The Plague Human population (billions) 2000 A.D

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Though the global population is still growing – The rate of growth began to slow approximately 40 years ago Figure Year 2003 Percent increase

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Regional Patterns of Population Change To maintain population stability – A human population must exhibit either: Zero population growth = High birth rates – High death rates Zero population growth = Low birth rates – Low death rates

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings How do we predict population trends? Age structure Diagrams (which has close to Zero Population Growth?) Figure Rapid growth Afghanistan Slow growth United States Decrease Italy Male Female Male FemaleMale Female Age Percent of population 80–84 85  75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 20–24 25–29 10–14 5–9 0–4 15–19 80–84 85  75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 20–24 25–29 10–14 5–9 0–4 15–19

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Infant Mortality and Life Expectancy Figure Developed countries Developing countries Developed countries Developing countries Infant mortality (deaths per 1,000 births) Life expectancy (years)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What is the Earth’s Human Carrying Capacity? The ecological footprint concept tells the land and water area needed to sustain the people of a nation Compare the footprint of 4 countries Figure New Zealand Australia Canada Sweden World China India Available ecological capacity (ha per person) Spain UK Japan Germany Netherlands Norway USA Ecological footprint (ha per person)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings At more than 6 billion people – The world is already in ecological deficit