Transcript Environmental Science Unit 1: Chapter 9

Chapter 9
The Human Population
9.1: Studying Human Populations
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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 structure
Describe the four stages of the demographic
transition
Explain why different countries may be at
different stages of the demographic transition
2 Categories for Countries:
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Countries are often grouped by
demographers into 2 general categories:
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Developed countries—higher average
incomes, slower population growth, and
diverse industrial economies.
Developing countries—lower average
incomes, simple and agriculture-based
economies, and rapid population growth.
Human Population Growth
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1800’s: exponential growth due to…
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Increases in food production
Improvements in hygiene (eg. clean water
and safe sewage disposal)
Industrial and scientific revolutions
Discovery of vaccines in the 20th century
Cannot continue…limited resources,
competition, carrying capacity
Predicting Population Sizes (4)
Age structure
1.
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The distribution of ages in a specific population at a certain
time.
Graphed in a population pyramid (lab!)
High growth rate more young than old
Slow or no growth  even distribution of ages
Survivorship
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The percentage of members of a group that are likely to
survive to any given age.
Survivorship curves: type I (most live to be very old), II
(similar death rates at all ages), III (very poor, many children
die)
Predicting Population Sizes (4)
Fertility rates: the number of babies born each
year per 1,000 women in a population.
3.
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Also can calculate total fertility rate
Considers “replacement level”: the avg. number of
children each parent must have in order to “replace”
themselves.
Migration: mvmt. of individuals btwn. areas.
4.
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Immigration (in) vs. Emigration (out)
Reasons for Increases in Human
Population Growth (or decline)…
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Death rates decreased more rapidly than birth
rates…causes???
Life expectancy (most affected by infant
mortality); survivorship curve
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1900 = age 40 w/ a high infant mortality rate
2000 = >age 67 (developed = 80+) w/ infant
mortality at < 1/3 of the rate in 1900
Infant health is affected by…
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-parents’ access to education, food, fuel, and clean water
Other threats?: density  increases in contagious
diseases (e.g. AIDS, tuberculosis, Ebola)
HW!!
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Read through chapter 9 
Pg. 239: The Demographic Transition
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Take notes over the “stages of transition” and
“women and fertility”
Checked in and discussed/questions tomorrow
9.2 Changing Population Trends
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Describe three problems caused by rapid
human population growth
Compare population growth problems in
more-developed countries and less
developed countries
Analyze strategies countries may use to
reduce their population growth
Describe worldwide population projections
into the next century
3 Problems…cause: rapid human
population growth
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Primary Problem: environmental; over
consumption of resources; infrastructure.
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1. vegetation…ex.: fuelwood
2. water…used for drinking, washing, &
sewage disposal: waterborne diseases such
as dysentery, typhoid, and cholera; ex. Lima,
Peru.
3. land…shortage of arable (A.V.) land
(land that is used to grow crops);
urbanization (A.V.); “suburban sprawl”.
Managing Development and Growth
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Strategies used include: family planning
programs, economic incentives, legal
punishments, public advertising, improvements
in women’s status.
Result: worldwide fertility rates are dropping!
Demographers predict that by 2050, most
countries will have replacement level fertility
rates  world population growth will _____(?)
World population = >7 billion and is still
increasing.