Ecology of Populations
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Outline. Scope of Ecology Demographics of Populations Population Density and Distribution Population Growth Models Survivorship Curves Age Distributions Regulation of Population Size Life History Patterns Human Population Growth Environmental Impact. Scope of Ecology. Ecology

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Outline

  • Scope of Ecology

  • Demographics of Populations

    • Population Density and Distribution

  • Population Growth Models

    • Survivorship Curves

    • Age Distributions

  • Regulation of Population Size

  • Life History Patterns

  • Human Population Growth

    • Environmental Impact


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Scope of Ecology

  • Ecology

    • The study of the interactions of organisms with

      • other organisms, and

      • The physical environment

    • Habitat - Place where an organism lives

    • Population - All the individuals of a species within a particular space

    • Community – Specified populations interacting with each other

    • Ecosystem - Community interacting with environment



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Density and Distribution of Populations

  • Population Density - Number of individuals per unit area or volume

  • Population Distribution - Pattern of dispersal of individuals within a space of interest

    • Ecologists analyze what causes the spatial and temporal “patchiness” of organisms

  • Limiting factors are factors that predominantly determine whether a species lives in a habitat



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Population Growth

  • Exponential Growth

    • Rate of increase increases as the total number of females increases

  • Biotic Potential

    • Maximum population growth that can possibly occur under ideal circumstances

  • Environmental Resistance

    • All environmental conditions that prevent populations from achieving biotic potential

  • Biotic potential is having full effect and birthrate is a maximum during exponential growth



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Mortality Patterns

  • A cohort

    • Composed of all the members of a population born at the same time

  • Survivorship

    • The probability that newborn individuals of a cohort will survive to a particular age

    • Survivorship Curves



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Age Distributions

  • What proportion of the population falls into various age categories

  • At least three structures possible

    • Increasing

    • Stable

    • Decreasing





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Logistic Growth

  • Logistic growth

    • Occurs when environmental resistance retards exponential growth

    • Growing populations must eventually come under the control of environmental resistance



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Regulation of Population Size

  • Density-dependent Factors

    • Number of organisms present influences the effect of the factor

      • Competition

      • Predation

  • Density-independent Factors

    • Number of organisms present does not influence the effect of the factor

      • Natural disasters




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Carrying Capacity

  • Carrying Capacity

    • The maximum number of individuals of a species the environment can continuously support

    • The closer the population to the carrying capacity, the greater the environmental resistance




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Life History Patterns

  • r - Strategists (Opportunistic)

    • Produce large numbers of offspring

    • Small body size

    • Early maturity

    • No parental care

    • Controlled by density-independent factors

    • Good dispersers and colonizers


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Life History Patterns

  • k - Strategists (Equilibrium)

    • Produce small numbers of offspring

    • Large body size

    • Late maturity

    • Significant parental care

    • Controlled by density-dependent factors

    • Specialists




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Human Population Growth

  • Human population has an exponential growth pattern

  • Doubling time currently estimated at 53 years

  • Population Size

    • 1800 1 Billion

    • 1930 2 Billion

    • 1960 3 Billion

    • 2000 6 Billion


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Country Development

  • More-Developed Countries (MDCs)

    • Slow population growth

    • High standard of living

    • Completed Demographic Transition

      • North America and Europe

  • Less-Developed Countries (LDCs)

    • Rapid population growth

    • Low standard of living

      • Latin America

      • Africa and Asia



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Age Distributions

  • Age Structure Diagrams

    • Show proportions of population at various age groups

    • Divide populations into three age groups

      • Pre-Reproductive

      • Reproductive

      • Post-Reproductive



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Environmental Impact

  • Environmental impact of a population is measured in terms of:

    • Population size

    • Resource consumption per capita

    • Resultant pollution



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Review

  • Scope of Ecology

  • Demographics of Populations

    • Population Density and Distribution

  • Population Growth Models

    • Survivorship Curves

    • Age Distributions

  • Regulation of Population Size

  • Life History Patterns

  • Human Population Growth

    • Environmental Impact



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