Populations and the
Chapter 5, 6.2 and 6.3
5.1 How Populations Grow
Population density is a
measurement of the
number of individuals
living in a defined
refers to how a population
is spread in an area.
The size of a population is
Four factors affect the size
of a population.
Population growth is based on
Exponential growth is a rapid
population increase due to an
abundance of resources.
Most populations are regulated by predators,
disease, and the availability of resources.
Because of this population will not exceed the
environmental carrying capacity
As a population grows, limited resources become
depleted and the growth of the population slows.
Logistic growth occurs when a population is
facing limited resources.
Carrying capacity is the maximum number of
individuals of a particular species that a
particular environment can support.
5.2 Limits to Growth
Limiting factors – control the growth of a
The rate at which they become depleted depends upon the
population density of the population that uses them.
Density-independent limiting factors limit a
population’s growth regardless of the size and
1.During which time period is birth rate higher than death rate?
2.During which time period are birth rate and death rate equal?
3.During which time period is death rate higher than birth rate?
5.3 Human Population Growth
For most of human existence, the
population grew slowly because life was
Food was hard to find. Predators and diseases
were common and life-threatening.
These limiting factors kept human death rates very
Improved nutrition, sanitation, medicine, and
healthcare, dramatically reduced death rates.
birthrates in most parts of the world remained high.
The combination of lower death rates and high birthrates led
to exponential growth.
6.2 Using Resources Wisely
How do we obtain what we need from local and
global environments without destroying those
Environmental Resources we affect:
Healthy soil supports both agriculture and
Topsoil – rich in organic matter and nutrients
Loss of fertile soil can have dire consequences.
Erosion – removal of soil by water or wind
Soil Use and Sustainablility
Leaving stems and roots of the previous
drinking water, industry, transportation, energy,
and waste disposal.
Some farmland relies heavily on irrigation
Many serious environmental problems
occur in our own backyard.
Agriculture introduces large amounts of
chemicals into the global ecosystem.
Including: pesticides, herbicides, and
Many chemicals, such as DDT, have been banned in the
US, but the effects of their use still circulate.
Causes biological magnification
Water Quality and Sustainability
Protecting the water cycle
Clean up pollution
Air quality has a direct impact on health.
Coal-burning power plants send smoke,
containing sulfur, into the atmosphere through
Scientists now know that the sulfur can combine with water
vapor to produce sulfuric acid, which will fall back to earth as
Acid rain causes forest damage, and dead lakes
Robl, Ernest H. Acid Rain Damage. Photograph
1990. Web. 21 Oct 2010.
Decrease in the amount of ozone (O3) in the
atmosphere allows more UV radiation to reach
the earth’s surface.
This can cause an increase in diseases related to UV
exposure such as cancer and cataracts.
The major cause is chlorofluorocarbons (CFCs) commonly
used in refrigerators, air conditioners, and in aerosols.
As a result CFCs have been banned in the US.
Hole in the ozone layer
Rubin, Ken. “Ask an Earth Scientist.”
Hawaii.Oct 2008. Web. 8 No
The earths average global temperature has been
steadily increasing for more than a century
Caused by the greenhouse effect, in which greenhouse gasses
trap the suns energy within the atmosphere.
Earth’s resources must be used responsibly.
Careless use of resources makes them unavailable to
An ecological footprint is the amount of land
needed to support a person.
The land must produce and maintain
food and water
Room for waste
Introduced species can disrupt stable relationships
in an ecosystem.
Burmese python in the Florida Everglades
Conservation methods can help protect and
Sustainable development meets needs without
hurting future generations.
resources meet current needs
resources will still be available for future use
The Endangered Species Act
Environmental Protection Agency (EPA)
National Park Service