U 5 lesson 3 integrado e.s. environmental changes

Unit 5 Lesson 3 How Do Environmental Changes
Affect Organisms?
Copyright © Houghton Mifflin Harcourt Publishing Company

Change Comes Naturally
• All environments change over time. Some changes
happen slowly and some occur quickly.
• Climate changes, or changes to weather patterns,
affect organisms.
• An ice age happens when Earth’s temperatures
are colder than normal for a very long time. Large
areas of land are covered in ice for thousands of
years.
Unit 5 Lesson 3 How Do Environmental Changes Affect Organisms?

• What kinds of changes to the environment may
have happened during the last ice age?

• Earth is now in a warming cycle, due in part to
human activities. As areas become warmer,
organisms will move, adapt, or disappear.
• Natural events, such as floods, mudslides, or
volcanic eruptions can change the environment
quickly.

Next, Please!
• The gradual change of organisms in an ecosystem
is called succession.
• Primary succession begins on bare rock. The first
organisms to colonize are called pioneer species.
• Lichens, common pioneers, break down rock as
they grow, producing soil. When they die, their
litter decays, adding nutrients to the soil.

Next, Please!
• Plants grow as soil develops. Mosses flourish,
producing more soil. Bigger plants take hold and,
eventually, trees grow.
• This establishes a mature, stable community. This
process can take hundreds of years.

Next, Please!
• Secondary succession occurs where an ecosystem
has been disturbed, but soil is still present.
• Secondary succession occurs more quickly and
uses existing soil that contains seeds and roots
that sprout and grow.
• Shrubs and grasses grow first, followed by larger
plants. Eventually, a stable ecological community
is re-established.

For Better or Worse
• Organisms living in an environment can cause
both harmful and helpful changes.
• For example, beavers cut down trees that provide
food and shelter for other living things in order to
make a dam.
• The dam also slows the flow of water to animals.
However, dams also produce wetlands, providing
homes for other organisms.

Invasive Species
• Invasive species grow quickly after being
introduced into a new environment.
• Invasive species take food and space away from
native species, the organisms already living in an
ecosystem.
• Invasive and native species compete for food.

• Human activities such as open-pit mining, cutting
down forests, and building highways can harm an
ecosystem.
• Humans produce waste, which ends up in landfills.
These landfills can pollute soil and water.
• Pollution is the contamination of air, water, or soil
by substances harmful to organisms.
Humans Change the Environment

Humans Change the Environment
• Not all changes caused by humans are harmful.
• Conservation is the act of protecting ecosystems
and the organisms living in them.
• Humans practice conservation by replanting trees,
cleaning up pollution, removing invasive plants
and animals, and caring for injured animals.

Gone!
• Some organisms do not survive changes in the
environment.
• Extinction happens when all the members of a
certain species dies.
• For example, giant reptiles like the Tyrannosaurus
rex lived in a time when the Earth was warm. As
the environment cooled, they became extinct.

Gone!
• Could the extinction of the dodo bird have been
prevented? Why or why not?

U 5 lesson 3 integrado e.s. environmental changes

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