High School Biology: Population

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Global Trends
World Population Growth
World population is expected to nearly double by 2050, from 5.7 billion in 1994 to about 10
billion people. Nearly all the growth will occur in the developing world.
UN Population Projections
Long-range global population projections vary dramatically depending on assumptions about
several factors, one of which is fertility. If fertility stabilized at 2.5 children per couple (the
"High" projection), global population could reach 28 billion in 2150. If it stabilized at 1.7
children (the "Low" projection), population would peak at 7.8 billion in 2050 but then fall to 4.3
billion 100 years later. The current average fertility rate is 3.3 (the "Medium" projection), down
from 4.5 in the early 1970s.
Age and Sex Distribution Industrialized Countries
There are some striking differences in the population makeup of the developing and industrialized
nations. In the industrialized nations, the population is more evenly distributed between young,
middle-aged, and elderly people. Because there is not a larger number of young people entering
their reproductive years, the size of this population can remain stable over time.
Total Fertility Rate Map
Another way of looking at growth trends is to consider fertility rates, or the average number of
births per woman. As the map shows, fertility rates are very high in developing regions such as
Africa and the Middle East and low in most industrialized regions, especially Europe, where
some countries have fertility rates below the replacement level.
Population Growth Rate Map
Contraceptive Use
Since 1960, there has been a dramatic increase in the percentage of married couples using
contraception in many developing countries, especially in Latin America, East Asia, and South
Asia. Contraceptive use is still relatively limited in Africa.
Child Mortality Rate Map
Many countries have made significant progress in reducing mortality of children under age 5. In
Brazil, the number of deaths per 1,000 live births dropped from 181 in 1960 to 69 in 1991; in
Zimbabwe during the same period, the rate declined from 181 to 90. But under-5 mortality
remains high in many countries, especially in Sub-Saharan Africa. For example, in Nigeria,
deaths per 1,000 live births dropped from 204 in 1960 to 191 in 1991.
POPClock Projection

One birth every.................................. 9 seconds
One death every.................................. 13 seconds
One international migrant (net) every............ 49 seconds
One Federal U.S. citizen (net) returning every...4496 seconds
Net gain of one person every..................... 17 seconds
World POPClock
World POPClock
Population and Human Development
Population and Human Development
Microevolution: Allele Frequencies
1.describe biological evolution in terms of change in allele frequency in a population.
2.list and explain Darwin's main ideas concerning natural selection and evolution.
3.explain why survival is necessary, but insufficient as a criterion for judging the adaptiveness of a trait.
4.describe evolution as changes in allele frequency resulting from directional, stabelizing, and disruptive selection.
5.provide examples of evolution resulting from natural selection.
6.describe an example in which natural selection has affected the virulence and/or spread of a human disease.