4.2
Human Population Grow
demography:- is the study of human population, density, distribution, movement, and birth and death rate
technology and growth
Humans have learned to change their environment in
ways that increase the carrying capacity
EX:-
domestication of animals have increased the human food
supply
Technological advances, such as in medicine and
shelter construction, have reduced the death rate
Human Population Growth and trends
Events such as disease and war can change population
trends.
countries with similar economies tend
to have similar population growth trends
EX:-
one trend is a change in the population growth rate in industrially developed countries, such as the united state
demographic transition
a change from high birth and death rates to low birth and death rate in a population
How is population growth rate calculated?
calculation for PGR is
[birthrate death rate migration rate] PGR (%)
EX:-
we will calculate and compare the 2008
population growth rates for the United States and Honduras, a
small country in Central America we'll have to divide the final answer by 10
to get a percentage because the rates are calculated per 1000.
The United States has birthrate 14.1 (per 1000), death rate
8.3 (per 1000), and migration rate 2.9 (per 1000). This gives a
PGR of 0.87 percent for the United States.
zero population
occurs when the birthrate
equals the death rate
. At zero population
growth, the number of people in different age groups should
be nearly equal
age structure is the number of males
and females in each of three age groups. The groups are
pre-reproductive (up to age 20), , reproductive (ages 20
through 44), and post-reproductive (after age 44).
human population growth concerns
carrying capacities
Scientists are concerned that the human
population might exceed Earth’s ability to support it