1. Science Background
· In building shelters and raising food, people often alter
habitats by removing trees, draining wetlands, changing
the courses of rivers and streams, and digging up soil.
Each disruption of a habitat affects the organisms that live
there.
· Growing crops is one farming activity that changes the
environment. Raising livestock also changes habitats.
Animals that eat grasses, such as sheep, goats, and cattle,
can overgraze and turn a healty grassland area into a
barren wasteland.
History of Science
As the human population grows, more houses and
roads are built and more animal and plant habitat is
lost. Since World War II, at least 70 million to 100
million acres of open space in the United States
have been lost.

2. Quick Quiz #1 (pages A94-A95)
Some ways farmers
change the land to
1. What are some ways
produce food including
farmers change the
cutting down trees,
land to produce food?
draining wetlands, and
digging the soil.
Some ways people
change the land are
2. Other than farming,
building homes to live
what are some reasons
in and roads, railroads
people change the
and airports for
land?
transporting things
they need.
H.O.T. Name some organisms that
might be affected when trees are cut
down.

3. Science Background
· Pollution is anything harmful added to air, water or
land. Pollution destroys habitats and harms living
things, including people.
· The increased use of cars, trucks , and other vehicles
that burn fossil fuels has resulted in air pollution
problems. (Cities such as Denver and Los Angeles
are plagued by smog a yellow-brown haze that
results from complex chemical reactions involving
sunlight, oxygen, and vehicle emissions. Smog
hinders visibility and can irritate the eyes and lungs.)
· Substances such as chemical fertilizers, peticides,
road salt, and automotive fluides cause some water
pollution. During rainstorms, these substances wash
from gardens, golf courses, farms and roads into
streams, rivers, and lakes.
· Litter and trash can pollute both water and land
habitats and can be harmful to living things.

4. Quick Quiz #2 (pages A96-A97)
1. How do fuels cause
pollution?
2. How might pollution
in a river habitat affect
fish?
H.O.T. Where would be more air
pollution, in a farming area or in city?
Explain.