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A changing human population
A changing human population
A changing human population
A changing human population
A changing human population
A changing human population
A changing human population
A changing human population
A changing human population
A changing human population
A changing human population
A changing human population
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A changing human population


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  • 1. A Changing Human Population Environmental Science
  • 2. Studying Human Populations
    • Demography – the study of the characteristics of populations (usually human populations)
    • Countries are divided into 2 categories by demographers:
      • Developed – higher average incomes, slower population growth, diverse industrial economies
      • Developing – lower average incomes, rapid population growth, agriculture-based economy
  • 3. Forecasting Population Size
    • Demographers try to predict what will happen to a population in order to plan for future infrastructure and services
    • Demographers look at several different factors to make their predictions
  • 4. Age Structure
    • Age structure describes the distribution of ages of a population
    • Countries with high growth rates have more young people than old people
    • Countries with slow growth or no growth have an even distribution of ages in the population
  • 5. Survivorship
    • The percentage of members of a group that are likely to survive to a given age
    • To predict survivorship, demographers study a group of people born at the same time and notes when each member of the group dies.
  • 6. Fertility Rates
    • The number a babies born each year per 1000 women of childbearing age (15-44)
    • Replacement level – the average number of children parents must have to “replace” themselves
  • 7. Declining Death Rates
    • Increased access to food, clean water, and safe sewage disposal have lead to a decrease in the world death rate
    • This decrease has more to do with the huge increase in the human population than the birth rate.
  • 8. Migration
    • Migration in general, is any movement of individuals or populations from one location to another.
    • The populations of many developed countries might be decreasing if not for immigration.
  • 9. Declining Death Rates
    • The dramatic increase in Earth ’ s human population in the last 200 years has happened because death rates have declined more rapidly than birth rates.
    • Death rates have declined mainly because more people now have access to adequate food, clean water, and safe sewage disposal.
    • The discovery of vaccines in the 20th century also contributed to the declining death rates.
  • 10. Life Expectancy
    • The average number of years that a member of a population is likely to live
    • Infant mortality rates have the largest influence on life expectancy numbers
    • Better medical care has lead to higher life expectancy in developed and developing nations.
  • 11. Demographic Transition
    • The demographic transition is the general pattern of demographic change from high birth and death rates to low birth and death rates.
    • Industrial development causes economic and social progress that then affects population growth rates.
  • 12. Women and Fertility
    • A decline in birth rates can most clearly be related to increasing education and economic independence for women.
    • Educated women learn family planning techniques and find that they do not need to bear as many children to ensure that some will survive.
    • Women are able to increase the prosperity for their families while spending less energy bearing and caring for children.