A changing human population


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A changing human population

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