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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece.

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Presentation on theme: "Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece."— Presentation transcript:

1 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 Population Ecology

2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: Earths Fluctuating Populations To understand human population growth – We must consider the general principles of population ecology

3 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Population ecology is the study of populations in relation to environment – Including environmental influences on population density and distribution, age structure, and variations in population size

4 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 52.1: Dynamic biological processes influence population density, dispersion, and demography A population – Is a group of individuals of a single species living in the same general area

5 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Density and Dispersion Density – Is the number of individuals per unit area or volume Dispersion – Is the pattern of spacing among individuals within the boundaries of the population

6 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Density: A Dynamic Perspective Determining the density of natural populations – Is possible, but difficult to accomplish In most cases – It is impractical or impossible to count all individuals in a population

7 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Density is the result of a dynamic interplay – Between processes that add individuals to a population and those that remove individuals from it Figure 52.2 Births and immigration add individuals to a population. BirthsImmigration PopuIation size Emigration Deaths Deaths and emigration remove individuals from a population.

8 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Patterns of Dispersion Environmental and social factors – Influence the spacing of individuals in a population

9 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A clumped dispersion – Is one in which individuals aggregate in patches – May be influenced by resource availability and behavior 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.

10 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A uniform dispersion – Is one in which individuals are evenly distributed – May be influenced by social interactions such as territoriality 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.

11 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A random dispersion – Is one in which the position of each individual is independent of other individuals Figure 52.3c (c) Random. Dandelions grow from windblown seeds that land at random and later germinate.

12 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Demography Demography is the study of the vital statistics of a population – And how they change over time Death rates and birth rates – Are of particular interest to demographers

13 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Survivorship Curves A survivorship curve – Is a graphic way of representing the data in a life table

14 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The survivorship curve for Beldings ground squirrels – Shows that the death rate is relatively constant Figure Number of survivors (log scale) Age (years) Males Females

15 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)

16 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reproductive Rates A reproductive table, or fertility schedule – Is an age-specific summary of the reproductive rates in a population

17 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 52.2: Life history traits are products of natural selection Life history traits are evolutionary outcomes – Reflected in the development, physiology, and behavior of an organism

18 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Species that exhibit semelparity, or big-bang reproduction – Reproduce a single time and die Figure 52.6

19 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Species that exhibit repeated reproduction – Produce offspring repeatedly over time

20 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Parental care of smaller broods – May also facilitate survival of offspring

21 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 – Which may lead to trade- offs between survival and reproduction RESULTS

22 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some plants produce a large number of small seeds – Ensuring that at least some of them will grow and eventually reproduce 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.

23 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Other types of plants produce a moderate number of large seeds – That provide a large store of energy that will help seedlings become established 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.

24 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 52.3: The exponential model describes population growth in an idealized, unlimited environment It is useful to study population growth in an idealized situation – In order to understand the capacity of species for increase and the conditions that may facilitate this type of growth

25 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Per Capita Rate of Increase If immigration and emigration are ignored – A populations growth rate (per capita increase) equals birth rate minus death rate

26 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Zero population growth – Occurs when the birth rate equals the death rate The population growth equation can be expressed as dN dt rN

27 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Exponential Growth Exponential population growth – Is population increase under idealized conditions Under these conditions – The rate of reproduction is at its maximum, called the intrinsic rate of increase

28 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Exponential population growth – Results in a J-shaped curve Figure ,000 1,500 2,000 Number of generations Population size (N) dN dt 1.0N dN dt 0.5N

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

30 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 52.4: The logistic growth model includes the concept of carrying capacity Exponential growth – Cannot be sustained for long in any population A more realistic population model – Limits growth by incorporating carrying capacity

31 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Carrying capacity (K) – Is the maximum population size the environment can support

32 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 52.5: Populations are regulated by a complex interaction of biotic and abiotic influences There are two general questions we can ask – About regulation of population growth

33 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What environmental factors stop a population from growing? Why do some populations show radical fluctuations in size over time, while others remain stable?

34 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Population Change and Population Density In density-independent populations – Birth rate and death rate do not change with population density In density-dependent populations – Birth rates fall and death rates rise with population density

35 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Density-Dependent Population Regulation Density-dependent birth and death rates – Are an example of negative feedback that regulates population growth – Are affected by many different mechanisms

36 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Territoriality In many vertebrates and some invertebrates – Territoriality may limit density

37 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cheetahs are highly territorial – Using chemical communication to warn other cheetahs of their boundaries Figure 52.16

38 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Oceanic birds – Exhibit territoriality in nesting behavior Figure 52.17

39 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Health Population density – Can influence the health and survival of organisms In dense populations – Pathogens can spread more rapidly

40 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Predation As a prey population builds up – Predators may feed preferentially on that species

41 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Toxic Wastes The accumulation of toxic wastes – Can contribute to density-dependent regulation of population size

42 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Intrinsic Factors For some populations – Intrinsic (physiological) factors appear to regulate population size

43 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Population Cycles Many populations – Undergo regular boom-and-bust cycles Figure Year Lynx population size (thousands) Hare population size (thousands) Lynx Snowshoe hare

44 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Boom-and-bust cycles – Are influenced by complex interactions between biotic and abiotic factors

45 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 52.6: Human population growth has slowed after centuries of exponential increase No population can grow indefinitely – And humans are no exception

46 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Global Human Population The human population – Increased relatively slowly until about 1650 and then began to grow exponentially Figure B.C B.C B.C B.C B.C A.D. 0 The Plague Human population (billions) 2000 A.D

47 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

48 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Regional Patterns of Population Change To maintain population stability – A regional human population can exist in one of two configurations

49 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Zero population growth = High birth rates – High death rates Zero population growth = Low birth rates – Low death rates

50 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The demographic transition – Is the move from the first toward the second state Figure Birth rate Death rate Birth rate Death rate Year SwedenMexico Birth or death rate per 1,000 people

51 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The demographic transition – Is associated with various factors in developed and developing countries

52 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Age Structure One important demographic factor in present and future growth trends – Is a countrys age structure, the relative number of individuals at each age

53 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Age structure – Is commonly represented in pyramids Figure Rapid growth Afghanistan Slow growth United States Decrease Italy Male Female Male FemaleMale Female Age Percent of population 80– –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– –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

54 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Age structure diagrams – Can predict a populations growth trends – Can illuminate social conditions and help us plan for the future

55 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Infant Mortality and Life Expectancy Infant mortality and life expectancy at birth – Vary widely among developed and developing countries but do not capture the wide range of the human condition Figure Developed countries Developing countries Developed countries Developing countries Infant mortality (deaths per 1,000 births) Life expectancy (years)

56 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Global Carrying Capacity Just how many humans can the biosphere support?

57 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Estimates of Carrying Capacity The carrying capacity of Earth for humans is uncertain

58 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ecological Footprint The ecological footprint concept – Summarizes the aggregate land and water area needed to sustain the people of a nation – Is one measure of how close we are to the carrying capacity of Earth

59 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ecological footprints for 13 countries – Show that the countries vary greatly in their footprint size and their available ecological capacity 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)

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


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