Population

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Population

• Chapters 8

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Is there a problem?

• EVERY FOUR DAYS WE ARE ADDING ALMOST ONE MILLION
  ADDITIONAL PEOPLE TO THE PLANET EARTH

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Outline of lecture

• I. Population ecology - the basics
• A. Four factors that influence population size
• B. Biotic potential and carrying capacity
• C. Life history strategies and survivorship
  curves
• D. Density-dependent and density-independent
  factors that influence population size
• II. Human population growth
• A. Historical perspective and current trends
• B. Differing population characteristics, highly
  developed and developing countries

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Outline (Cont.)

• III. The human population explosion
• A. Factors related to human population growth
• B. People overpopulation vs. consumption
  overpopulation
• IV. Urbanization
• A. Trends in distribution rural and urban
  areas
• B. Urban population
• V. Fertility, national policies, and control of
  global human population growth
• A. Fertility rates and related factors
• B. National policies on fertility
• C. Control of global population growth

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Principles of Population

• Humans have a significant role in many
  environmental problems.
• As the number of humans increase so does the
  impact to the environment

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Lets look at population of animal species

• Population ecology number of individuals of a
  particular species found in a place how why
  those numbers increase or decrease.
• How does a population respond to environment?
• How do individuals compete?
• How does predation, disease, other
  environmental factors affect populations.

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Population Density

• Definition
• Can it vary?

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Population Change

• On global scale, change due to 2 factors
• 1.
• 2.
• Both birth and death rate are expressed in number
  per 1,000 people per year.
• Growth Rate

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What happens on a local scale?

• Population is effected by
• Growth rate r or
• Growth rate r

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What limits population Growth?

• No population can grow indefinitely because
  resources such as light, water, an nutrients are
  limited because of competitors or predators.
• Biotic potential
• Intrinsic rate
• Environmental resistance

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Carrying capacity

• Carrying capacity (K) number of individuals that
  can be supported in an area within natural
  resources limits without degrading the natural
  social, cultural, economic environment for
  present and future generations. .

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Carrying Capacity (cont.)

• As the environment is degraded, the carrying
  capacity shrinks. No population can live beyond
  the environments carrying capacity for very
  long.
• Carrying capacity for a given areas is not fixed.
  It can be altered by improved technology, but
  mostly it changes or the worse by pressures with
  accompany a population increase.

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Reproductive Strategies

• The perfect organism would
• 1.
• 2.
• 3.
• 4.
• No such organism exists!
• Would require all energy to go into reproduction
  and none would be left over to survive.

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Reproductive Characteristics

• r selection populations that have traits that
  contribute to high population growth.
• r growth rate
• High r strategists or r-selected species
• Small body size, early maturity, large broods, no
  parental care.
• Mosquitoes, weeds
• K selection traits maximize chance of surviving
  in environment near carrying capacity
• K strategists or K-selected species
• Long life spans, slow development, late
  reproduction, large body size, low productive
  rate
• Redwood trees, owls, elephants

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Survivorship

• Probability that a given individual in a
  population will survive to a particular age.

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Factors that Affect Population Size

• Density-Independent Factors affect a population
  size regardless of its size
• Examples -
• Density-Dependent Factors factors that limit
  population growth have a greater effect as
  populations density increases.
• Examples.

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Human Population
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Statistics

• Earth human population reached 6 billion in 1999
• Annual birth rate has declined from 2.2/yr in
  1960s to 1.4/yr in 2000 but death rate has also
  declined
• Estimate that zero population growth will be
  reached by end of 21st century
• By 2050, world population will be between 7.7
  billion 11.1 billion with 9.4 billion most
  likely

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Trends in Population

• Zero Population Growth when the birth rate
  equals the death rate.
• J curve
• S curve

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• Human population growth

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Demographic Transition
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Age Structure Diagrams
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Age Structure Diagrams

• When evaluating age diagrams, look at population
  size between 15 -44 years (reproductive years)
  0-14 years (pre-reproductive years).
• Worldwide 31 of population lt 15 years.
• Age diagrams

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Developed Countries

• Low population growth rate
• Highly industrialized
• Low birth rate
• Low infant mortality rate
• Infant mortality of infant deaths/1000 live
  births
• Examples

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Moderately Developed Countries

• Higher birth infant mortality rates, but
  declining
• Medium level of industrialization
• Lower GNP than developed countries
• Examples

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Less Developed Countries

• High birth infant mortality rates
• Short life expectancies
• Lowest GNPs
• Example

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Doubling Time

• The doubling time is the amount of time for a
  population to double in size
• Use the rule of 70
• 70/percentage growth rate doubling time in yrs
• Derived from mathematics for exponential growth
• Example World population grew by 1.2 in 2004.
  If that rate continues, the earths population
  will double in 56 years (70/1.256)

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Total Fertility Rate

• Total Fertility Rate (TFR) Average number of
  children a woman typically has during her
  reproductive years.
• In 2004, globally TFR was 2.8 children per woman.
• __ in developed countries
• __ in developing countries
• __ in Africa in 2004

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Replacement-level Fertility

• The number of children a couple must have in
  order to replace themselves.
• __ in highly developed countries
• __ in developing countries because some female
  children die before reaching their reproductive
  years.

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U.S. Population

• No formal population policy
• Highest rate of population increase of all highly
  developed countries
• 0.6 in 1992 compared to Europe 0.1 and Japan
  0.2
• Immigration has big effect
• Birth rate has decreased for last few years but
  still have baby boom bubble.

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