Human Population Size

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Human Population Size
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Questions for Today

• What are the Major Factors that affect Human
  Population Size?
• How are fertility rates analyzed?
• What are the factors that affect Birth and
  Fertility Rates?
• What are factors that affect Death Rates?
• What factors affect Migration?

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Factors that affect Population Size

• There are three factors that affect population
  size
• Births (fertility)
• Death (mortality)
• Migration
• Remember the formula to calculation Population
  Change
• Pop. Change (B I) (D E)

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Population Change

• For most of human history, the human population
  roughly grew at a slow pace.
• Within the past 200 years, that rate has
  increased significantly.
• Our current rate is roughly, 1.22
• 82 million people were added to the world in
  2008.
• An Average of 225,000 people are added daily
• 2.4 people are added every time your heart beats.
  
• http//www.worldometers.info/

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Population Change

• Three major factors account for this major
  increase
• Our ability to invade new ecosystems and adapt
  fast.
• The Agricultural Revolution
• Led to food surpluses and civilization
• The Industrial Revolution and modern medicine
• The development of sanitation, antibiotics, and
  vaccines.
• Longer life spans and decreased infant mortality

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Make sure that you know at least the top 5!
Fig. 6-3, p. 126
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Factors that affect Population Size

• Demographers use the crude birth and crude death
  rate to calculate population change
• Crude rates are determined by looking at the
  number of births and deaths per 1,000 people in a
  population per year.
• An estimated and extrapolated number.

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Fertility Rates

• Demographers also take in consideration Fertility
  Rates when calculating Population Statistics.
• Fertility rates are the number of children born
  to a woman during her lifetime.
• Two types of fertility rates
• Replacement-level fertility rate
• Total Fertility rates

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Replacement Level Fertility

• The average number of children per woman
  necessary to sustain a population size.
• Ideally would be 2 children per woman, one to
  replace the mother and one to replace the father.
• Ranges from 2.1 in developed countries (low
  infant mortality rates and good medical care) to
  2.5 in developing countries (high infant
  mortality rates and medical care not as good).

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Total Fertility Rate

• The average number of children born to women in a
  population during their reproductive years.
• The average world wide is 2.6 children per women.
• 1.6 in developed
• 2.8 in developing

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Factors that Affect Birth and Fertility Rates

• There are 10 factors that affect Fertility rates
• Child Labor (higher for developing)
• Cost of raising and Education (causes decrease in
  rates for developed countries)
• Availability of private and public pension
  systems (reduces the need to have many children
  for support)
• Urbanization (Urban areas typically provide more
  access to family planning services)
• Educational and employment opportunities for
  women (Increased opportunities tend to lower
  rates).

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Factors that Affect Birth and Fertility Rates

• 6. Infant Mortality Rate
• 7. Average age of marriage (Typically fewer
  children when avg. age of marriage is higher)
• 8. Availability of legal abortions
• Reliable Birth Control
• Religious Beliefs and Cultural Norms (For
  example, these factors may favor large families
  and strongly oppose abortion and some forms of
  birth control).

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Factors that affect Death Rate

• The boom in Human population growth is not
  primarily caused by the birth rate.
• Our Death (Mortality) Rate has significantly
  dropped.
• Death Rates have dropped due to
• Increased Food Supply
• Better nutrition
• Medical Advances
• Improved Sanitation
• Availability of Clean Water

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Factors that affect the Death Rate

• Two statistics used by Demographers as indicators
  of the overall health of people in a country or
  region
• Life Expectancy (the avg. number of years a
  newborn infant can expect to live)
• 1955 48 ? 2008 68 ? 2050 74
• Worldwide
• In the US, the Life Expectancy is 78
• Infant Mortality Rate (number of babies out of
  every 1,000 born who die before first birthday)

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Life Expectancy

• Two major factors that affect Life Expectancy in
  the US
• Healthcare across the Nation
• Obesity

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Infant Mortality

• Infant Mortality is one of the best measures of a
  societys quality of life
• Reflects general nutrition and pediatric health
  care
• Three factors affect Infant Mortality Rates in
  the US
• Health Care
• Drug addictions among pregnant women
• High Teen Birth Rates

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Migration

• Migration is affected by the economic and social
  problems of other countries.
• Most people leave countries to pursue better
  opportunities in another.
• Jobs
• Healthcare
• Political Opposition
• Religious Intolerance

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Population Doubling Time

• Refers to the number of years that it takes for a
  population to double
• Can be estimated with the rule of 70
• Doubling time 70/the percentage growth rate
• For example, at a growth rate of 2 annually
• Doubling time 70/2 (keep whole number)
• The number of years required for this population
  to double is 35.