Earth and Human Populaiton (Population Structure ( (), Populations tend…
Earth and Human Populaiton
Population explosion describes a sudden increase in a population.
For most of history, the human population increased at a fairly
steady rate. But in the 1800s, the population began to rise sharply
Populations tend to increase in size.
Many factors influence population growth. The rate of
population growth can be determined by subtracting the
number of individuals leaving a population from the number
entering the population. Individuals leave a population either by
death or by leaving an area to settle somewhere else. They enter
the population by birth or by moving to an area to live there.
Another factor that affects population growth is age structure.
A population’s age structure is the number of
males and females in each of three age groups: pre-reproductive
state, reproductive state, and post-reproductive state. A
nongrowing population looks like a rectangle. A slow-growing
population looks like a rectangle with a bulge in the middle. A
rapidly growing population looks like a triangle with its base at
Earth has limited resources. Earth cannot
support a population of any species in a particular environment
beyond Earth’s carrying capacity. Carrying capacity is the
largest number of individuals of a given species that Earth’s
resources can support and maintain for a long period of time
Approaching Carrying Capacity
Each person uses resources.
When the population of a species is low, resources are abundant.
The population then increases. If resources become scarce, the
population can decrease. If the human population continues to
grow beyond Earth’s carrying capacity, eventually Earth will not
have enough resources to support humans.
Growing Populations and Resource Use
The amount of
resources used by each person is an important factor to consider
when analyzing human population growth. The graph below
shows the estimated amount of land need to support a person
through his or her lifetime. Notice that individuals in
industrially developed countries use far more resources than
individuals in developing countries.