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The Human Population Chapter 9.

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Presentation on theme: "The Human Population Chapter 9."— Presentation transcript:

1 The Human Population Chapter 9

2 I. Studying Human Populations
The human population of Earth has grown faster in the 20th century than in any other time – & led to environmental problems Demography – the study of populations – particularly the human population study historical size and makeup of the populations of countries to make comparisons and predictions Demographers study properties that affect population growth Countries with similar population trends are often grouped together

3 2 Types Of Countries Developed countries – higher average incomes, slower population growth, diverse industrial economies, and stronger social support systems Developing countries – lower average incomes, simple and agriculture-based economies, and rapid population growth

4 A. The Human Population Over Time
After growing slowly for thousands of years, the human population grew rapidly in the 1800s and underwent exponential growth Increases were due to increases in food production and improvements in hygiene that came with the industrial and scientific revolution. Ability to expand into new habitats – improved navigation and sailing It is unlikely the Earth can sustain this growth for much longer

5 A. The Human Population Over Time
After growing slowly for thousands of years, the human population grew rapidly in the 1800s and underwent exponential growth Increases were due to increases in food production and improvements in hygiene that came with the industrial and scientific revolution. Ability to expand into new habitats – improved navigation and sailing. It is unlikely the Earth can sustain this growth for much longer  

6 World Population Over Time

7 B. Forecasting Population Size
Age structure – the distribution of ages in a specific population at a certain time -if a population has more young people than old, the population will likely increase -graphed in a population pyramid – a type of double-sided bar graph that shows the age structure of a population

8 Age Structure Diagrams

9 Age Structure Diagrams
high rates of growth – pyramid has a fat bottom – or lots of young people slow growth or no growth – pyramid is evenly distributed -shrinking population – pyramid is inverse

10 Survivorship Survivorship – the percentage of members of a group that are likely to survive to any given age -to predict survivorship a demographer studies a group of people born at the same time and notes when each member of the group dies The results plotted is called a survivorship curve – One of 3 types Type I – wealthy, developed countries because most of the group lives a long time Type II – populations have similar death rates at all ages Type III – very poor countries in which many children die

11 Fertility rate Fertility rate – the number of babies born each year per 1000 women Total Fertility Rate (TFR) – or the average number of children a woman gives birth to in her lifetime

12 Replacement Level Fertility
– the average number of children each couple must have in order to “replace” themselves in the population -slightly higher than 2 (2.1) because not all children will survive to reproduce total fertility rates in the US remained below replacement level for most of the 1990s, but the population has continued to grow -children of the baby boom grew up and had children at a lower rate – you all are called echo babies

13 Hello Echo Boomers y’all are important to the economy!

14 Migration Another reason the population continued to grow was that immigration increases Migration – the movement of individuals between areas -immigration – movement into an area -emigration – movement out of an area Migration between and within countries is a significant part of population change The populations of many developed countries might be decreasing if not for immigration

15 C. 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 because more people now have access to adequate food, clean water, safe sewage disposal, proper medical care (vaccines)

16 Life Expectancy – the average number of years a person is likely to live -most affected by infant mortality – the death rates of infants less than a year old -in 1900 the average life expectancy was about 40, now the average is 67 years, but in developed countries the life expectancy is almost 80 years -infant health is most affected by parents’ access to education, food, fuel, and clean water -life expectancy influenced by contagious disease like tuberculosis and AIDS

17 D. The Demographic Transition
Demographic transition – a model that describes how these changes can occur -based on observations of the history of many developed countries -industrial development causes economic and social progress that then affects population growth rates

18 Stages of the transition
Preindustrial stage – birth and death rate are both high and population size is stable -most of the world was at this stage until about 1700 when the scientific and industrial revolution began Transitional stage –population explosion occurs-death rate declines due to improvements in hygiene, nutrition, and education happen-birth rates remain high and so the population explodes

19 Stages of the transition
Industrial Stage – population growth slows because the birth rate decreases-as the birth rate becomes close to the death rate, the population size stabilizes the population is much larger than before the demographic transition Postindustrial Stage – the birth rate drops below replacement level so the size of the population begins to decrease

20 Total Fertility Rate & Population Growth in the U.S.

21 Demography World Wide

22 Women and Fertility -the factors most clearly related to a decline in birth rates are increasing education and economic independence for women -educated women find they do not need to bear as many children to ensure some will survive -learn family planning techniques -contribute to their family’s increasing prosperity while spending less energy bearing and caring for children

23 countries that want to reduce birth rates have placed a priority on the education of females
-large families are valuable in communities where children work or take care of older family members -as countries modernize, parents are more likely to work away from home, parents must pay for child care, and so they are more likely to become a financial burden rather than an asset

24 elderly will not need the support of their children if pensions are available -all of these reasons contribute to lower birth rates -today the total fertility rate in developed countries is about 1.6 children per woman, while in developing countries the rate is about 3.1 children per woman


26 II. Changing Population Trends
A rapidly growing population uses resources at an increased rate and can overwhelm the infrastructure of a community. infrastructure – the basic facilities and services that support a community public water supplies, sewer lines, power plants, roads, subways, schools, hospitals -symptoms of overwhelming population include suburban sprawl, overcrowded schools, polluted rivers, barren land, and inadequate housing

27 A. Problems of Rapid Growth
A rapidly growing population can use resources faster than the environment can renew them -wood removed from local forests faster than it can grow back -wastes overwhelm local water sources -vegetation, water, and land are the resources most critically affected by rapid growth

28 A. Problems of Rapid Growth
Shortage of fuelwood -in many of the poorest countries, wood is the main fuel source -when populations are stable people use fallen tree limbs for fuel which does not harm trees, but when populations grow rapidly deadwood does not accumulate fast enough to provide fuel -people cut down living trees which reduces the amount available in each new year -a supply of fuel ensures a person can boil water and cook food

29 Problems of Rapid Growth
important to boil water as public supplies of water are not safe to drink and can carry waterborne diseases -food also is unsafe and harder to digest if uncooked -without enough fuelwood many people suffer from disease and malnutrition

30 Unsafe water In places that lack infrastructure, the local water supply may be used not only for drinking and washing but also for sewage disposal -the water supply becomes a breeding ground for organisms that cause disease such as dysentery, typhoid, and cholera -places with rapidly growing populations, the water systems cannot be expanded fast enough

31 Unsafe water

32 Impacts on land Arable land – land that can be used to grow crops
-growing populations also make trade-offs between competing uses for land such as agriculture, housing, or natural habitats Urbanization – more people living in urban areas than in rural areas -suburban sprawl – when people find work in the cities but live in the suburban areas -leads to traffic jams, inadequate infrastructure, reduction of land for farms, ranches, and wildlife habitat -housing within cities becomes more costly, more dense, and in shorter supply

33 B. A Demographically Diverse World
Not every country is progressing through each stage of the demographic transition according to the model In recent years the international community has begun to focus on the least developed countries -show few signs of development, increasing death rates, birth rates remain high -given priority for foreign aid and development programs

34 C. Managing Development and Population Growth
Countries such as China, India, and Thailand have created campaigns to reduce the fertility rate of their Citizens -family planning programs, economic incentives, or legal punishments 1994 the UN held the International Conference on Population and Development (ICPD) -debates about the relationships between population, development and the environment -favor stabilizing population through improvements in women’s status and other investments in development

35 5 main goals by 2015 -universal access to family planning and reproductive health services -reduce infant mortality rates -close the gap in maternal mortality -increase overall life expectancy -universal access to and completion of primary education and access to secondary and higher levels of education for girls and women

36 D. Growth is Slowing The human population is 6.5 billion and still growing -the worldwide population growth peaked at about 87 million per year between 1985 and 1990 -it grew by 85 million between 90 and 95 -fertility rates have declined but rates are still much higher in developing regions

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