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Chapter 9: The Human Population

Environmental Science
by

Desi Gorby

on 20 January 2013

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Transcript of Chapter 9: The Human Population

By: Desireé Gorbea, Simara Quiñones, Maya McCollum
Environmental Science: Period 4
January 15, 2013 Chapter 9: The Human Population Objectives:
Describe how the size and growth rate of the human population has changed in the last 200 years.
Define four properties that scientists use to predict population sizes.
Make predictions about population trends based on age structures.
Describes the four stages of the demographic transition.
Explain why different countries may be at different stages of the demographic transition. Section 1: Studying Human Population Key Terms:
Demography
Age Structure
Survivorship
Fertility Rate
Migration
Life Expectancy
Demographic Transition Section 1:
Studying Human Population The human population of Earth grew faster in the 20th century than it ever has before.
The rapid growth has led to environmental issues around the world.
Demography- is the study of populations; but most often refers to the study of human populations. The Human Population Over Time. Developed Countries- have higher average incomes, slower population growth, diverse industrial economics and stronger social support systems.
Developing countries- have lower average incomes, simple and agriculture-based economies, and rapid population growth. The Human Population Over Time. After growing slowly for thousands of years, the human population grew rapidly in the 1800s.
The human population underwent:
Exponential growth- which means that population growth rates increased during each decade. The Human Population Over Time. The increases were mostly due to increases in food production and improvements in hygiene that came with the industrial and scientific revolution.
Very unlikely the Earth can sustain this growth for much longer. The Human Population Over Time. The increases were mostly due to increases in food production and improvements in hygiene that came with the industrial and scientific revolution.
Very unlikely the Earth can sustain this growth for much longer. The Human Population Over Time. Population predictions are often inaccurate, however, because human behavior can change suddenly.
Demographers can make many predictions based on:
Age Structure- the distribution of ages in a specific population at a certain time.
Example: if a population has more young people than older people, the population has more young as the young people grow up and have children. Forecasting Population Size:
Age Structure. Age structure can be graphed in a:
Population Pyramid- is a type of double-sided bar graph.
Countries that have high rates of growth usually have more young people than old people.
In contrast, countries that have slow growth or no growth usually have an even distribution of ages in the population.
When parents have fewer children, the population will have fewer young people. Forecasting Population Size:
Age Structure. Age structure can be graphed in a:
Population Pyramid- is a type of double-sided bar graph.
Countries that have high rates of growth usually have more young people than old people.
In contrast, countries that have slow growth or no growth usually have an even distribution of ages in the population.
When parents have fewer children, the population will have fewer young people. Forecasting Population Size:
Age Structure. Another way to predict population trends is to study survivorship.
Survivorship- is 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. Forecasting Population Size:
Survivorship. Survivorship curves: show(s) how much of the population survives to a given age.
Wealthy developed countries such as:
Japan and Germany currently have a Type 1 survivorship curve because most people live to be very old.
Type 2 population have a similar death rate at all ages.
Type 3 survivorship is the patter in very poor human populations in which many children die.
Both Type 1 and Type 3 survivorship may result in populations that remain the same size or grow slowly. Forecasting Population Size:
Survivorship. Fertility Rate- the number of babies born each year per 1,00 women in a population.
Demographers also calculate the total fertility rate, or the average number of children a woman gives birth to in her lifetime.
In 1972, the total fertility rate dropped below replacement level for the first time in U.S. history. Forecasting Population Size: Fertility Rates. Fertility Rate- the number of babies born each year per 1,00 women in a population.
Demographers also calculate the total fertility rate, or the average number of children a woman gives birth to in her lifetime.
In 1972, the total fertility rate dropped below replacement level for the first time in U.S. history. Forecasting Population Size: Fertility Rates. Another reason the population continued to grow was that the immigration increased.
Migration- the movement of individuals between areas. Forecasting Population Size:
Migration. Movement into an area is immigration and movement out of an area is emigration.
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. Forecasting Population Size:
Migration. 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. Declining Death Rates:
Life Expectancy. The discovery of vaccines in the 20th century also contributed to declining death rates, especially among infants and children.
Life Expectancy- the average number of years a person is likely to live.
Life expectancy is most affected by:
Infant mortality: the death rate of infants less than a year old.
In 1900, worldwide life expectancy was about 40 years and the infant mortality rate was very high. Declining Death Rates:
Life Expectancy. By 2000, the rate of infant mortality was less than one-third of the rate in 1900.
Average life expectancy has increased to more than 67 years world wide.
For people in many developed countries, life expectancy is almost 80 years.
Expensive medical care is not needed to prevent infant deaths.
The infant mortality rate differs greatly among countries that have the same average income.
Instead, infant health is more affected by the parents’ access to education, food, fuel, and clean water. Declining Death Rates:
Life Expectancy. Even in poor areas, many people now know that babies simple need to be fed well and kept clean and warm.
If these basic needs are met, most children will have a good chance of surviving.
Meanwhile, new threats to life expectancy arise as population becomes denser.
Contagious diseases such as AIDS and tuberculosis are a growing concern in a world where such disease can spread quickly.
Life expectancy in sub-Saharan Africa has bee reduced in recent decades due to epidemics of AIDS. Declining Death Rates:
Life Expectancy. In more developed countries, populations have stopped growing.
Demographic transition- is a model that describes how these changes can occur.
The model is based on observations of the history of many developed countries.
The theory behind the demographic transition is the industrial development causes economic and social progress that then affect population growth rates. The Demographic Transition:
Stages of the Transition. In the first stage, of demographic transition, a society is in a preindustrial condition.
The birth rate and the death rate are both at high levels and population size is stable.
Most of the world was in this condition until about 1700, when the scientific and industrial revolution began. The Demographic Transition:
Stages of the Transition. In the second stage, a population explosion occurs.
Death rates decline as hygiene, nutrition, and education improve.
Birth rates remain high, so the population grows very fast.
During this stage, the population could double in less than 30 years. The Demographic Transition:
Stages of the Transition. In the third stage, of the demographic transition, population growth slows because the birth rates decreases.
As the birth rate comes close to the death rate, the population size stabilizes.
The population is much larger than before the demographic transition.
In most countries, that have passed through the transition, the population quadrupled during the 20th century. The Demographic Transition:
Stages of the Transition. In the fourth stage, the birth rate drops below replacement level, so the size of the population begins to decrease.
It has taken from one to three generations for the demographic transition to occur in the most developed countries. The Demographic Transition:
Stages of the Transition. Factors most clearly related to a decline in birth rates are:
Increasing education.
Economic independence for women. Women and Fertility Today, the fertility rate in develped countries is about 1.6 children per women.
Developing countries, the rate is about 3.1 children per children per women. Women and Fertility Education of girls and women is being suggested more and more. Objectives:
Describe three problems caused by rapid human population.
Compare population growth problems in more-developed countries and less developed countries.
Anakyze strategies countires may use to reduce their population growth.
Describe worldwide population projections into the next century. Section 2:
Changing Population Trends Key Terms:
Infrastructure
Arable Land
Urbanization
Least Developed Countries Section 2:
Changing Population Trends A rapidly growing population uses resources at an increased rate and can overwhelm the infrastructure of a community.
Infrastucture- is the basic facilities and services that support a community, such as public water supplies, sewer lines, power plants, roads, subways, schools and hospitals Problems of Rapid Growth. Symptoms of overwhelming population growth :
Suburban sprawl,
Overcroweded schools
Polluted rivers,
Barren land,
Inadequate housing. Problems of Rapid Growth. Rapid population growth can put pressure on: sources of water, land, and materials used for fuel or shelter. Humans cannot live without:
Sources of clean water.
Burnable fuel.
Agricultural land.
A rapidly growing population can use resources faster than the environment can renew them. Problems of Rapid Growth Standards of living decline when:
Wood is removed from local forests faster then it can grow back
Wastes overwhelm local water sources
Resources most critically affected by rapid growth are:
Vegetation,
Water and
Land Problems of Rapid Growth. Wood is the main fuel in poor countries
Supply of fuel ensures that a person can boil and cook food A Shortage of Fuelwood. Every person needs space to live in.
People prefer to live where they have easy access to resources and a comfortable lifestyle.
Growing populations may have a shortage of arable land. Impacts on Land. Arable land- is land that can be used to grow crops.
Growing populations also make trade-offs between competing uses for land.
Agriculture,
Housing,
Natural competing. Impacts on Land Much of the worlds population is undergoing urbanization.
Urbanization- more people living in cities than in rural areas. Impacts on Land Some impacts on land are:
Traffic jams,
Inadequate infrastructure,
Reduction on land for farms and Ranches & Wildlife habitat.
This becomes more costly, more dense, and causes shorter supply. Impacts on Land. As you have seen, demographers may categorize countries as either developed or developing.
Least Developed Countries- are countries that show few signs of development and in some cases have increasing death rates, while birth rates remain high.
In contrast, populations are still growing rapidly in less developed regions. Most of the worlds population is now within Asia. A Demographically Diverse World. http://www9.ocn.ne.jp/~aslan/pfe/pop.htm Humans throughout history have witnessed the negative effects of population growth.
In 1944, the United Nations held the International Conference on Population and Development.
Many countries favor stabilizing population growth through investments in development, especially through improvements in women's status. Managing Development and Population Growth. http://www.eoearth.org/article/Human_population_explosion?topic=54245 Fertility rates have declined since about 1970 in both more developed and less developed regions.
Demographers predict that this trend will continue and that worldwide population growth will be slower in this century than in the last century.
Most demographers predict the medium growth rate and a world population of 9 billion in 2050. Growth is Slowing. http://www9.ocn.ne.jp/~aslan/pfe/pop.htm Arms, K. (2004). Holt Environmental Science. Chapter 9: The Human Population (pg. 218-231). Austin: Holt Rinehart Winston.
http://www.google.com/imghp?hl=en&tab=wi
Google images. Bibliography:
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