Population Dynamics

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Population Dynamics

• And
• Human Population Growth

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Major Characteristics of Populations

• Size number of individuals
• Density individuals per unit of space
• Dispersion spatial pattern
• Age Distribution proportion of individuals per
  age group

3
Limits on Population Growth

• Births
• Deaths
• Immigration
• Emigration
• population change
• (births immigration)-
• (deaths emigration)

4
Biotic Potential

• A populations potential for growth
• Factors influencing biotic potential
• High reproductive rate
• Adequate food supply
• Suitable habitat
• Resist disease
• Ability to adapt to environmental change

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Environmental Resistance

• A populations limits on growth
• Factors influencing environmental resistance
• Low reproductive rate
• Inadequate food supply
• Loss of habitat
• Inability to resist disease
• Inability to adapt to environmental change

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Carrying Capacity (K)

• Number of individuals of a species that can be
  sustained indefinitely in a given area
• Determined by biotic potential and environmental
  resistance

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• In the real world, a rapidly growing population
  reaches some size limit imposed by one or more
  limiting factors
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Exponential Growth

• Starts slowly
• Speeds up as population increases
• Individuals plotted against time produces a
  J-curve

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Logistic Growth

• Exponential growth occurs when the population is
  small
• Steady decrease in population growth with time as
  environmental resistance is encountered
• Individuals plotted against time produces an
  S-shaped curve

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Conversation Biologyand Population Dynamics

• Monitors status of natural populations to see
  which species are endangered
• Monitors quality and size of habitat needed to
  ensure viable populations of wild species

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Human Global Population Dynamics

• Same influences
• population change
• (births immigration)-
• (deaths emigration)
• Instead of using total numbers, birth rates and
  deaths are used.

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• Birth rate number of deaths per 1,000 people in
  a population in a given year
• Death rate number of deaths per 1,000 people in
  a population in a given year
• The worlds annual population change is
  expressed as a percentage

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Fertility Rates

• Fertility rates affect a countrys population
  size and growth rate
• There are two types
• Replacement level fertility
• Total fertility rate

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Replacement Level Fertility

• Number of children a couple must have to replace
  themselves
• 2.1 in developed countries
• 2.5 in developing countries
• Greater than 2 because some children die before
  reaching reproductive years

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Total Fertility Rate

• Estimate of the average number of children a
  woman will have during her childbearing years
  under current age-specific birth rates
• TFR for developed countries was 2.5 in 1950 and
  1.5 in 1999
• TFR for developing countries was 6.5 in 1950 and
  3.2 in 1999

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Total Fertility Rate
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United Nations Population Model

• Assumes that fertility rates will eventually
  stabilize at the replacement level of two
  children per mother
• Most countries with declining populations have
  dipped well below that level
• As a society modernizes, the fertility rate goes
  down to between 1.5 and 2 children per woman

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Age Structure Diagrams

• Plots percentages or numbers of males and females
  in the total population in 3 age categories
• Prereproductive
• Reproductive
• Postreproductive

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Age Structure of a Population
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Age Structure
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Age Structure and Population Growth

• Countries with many people below age 15 has a
  powerful built in momentum to increase its
  population size.

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Thomas Malthus, 1798

• Exponential human population growth causes
  social and environmental problems

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Malthus The Ultimate Pessimist

• "...the power of population is indefinitely
  greater than the power in the earth to produce
  subsistence for man. Population, when
  unchecked, increases in a geometrical ratio.
  Subsistence increases only in an arithmetical
  ratio. A slight acquaintance with numbers will
  show the immensity of the first power in
  comparison with the second.
• --Malthus.

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• Malthus was the first to propose that human
  population growth should be controlled.
• Malthus advocated this for the lower class of
  which he was not apart.

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Environmental Concerns and Human Population Growth

• Habitat disturbance
• Loss of species
• Pollution
• Soil loss
• Resource depletion
• Destruction of ecosystems

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Ethical Concerns and Human Population Control

• Forced sterilization
• Abortion
• Euthanasia
• Contraception
• Over consumption
• Viewing people as problems vs. assets

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• The
• End