The document discusses how environmental changes affect organisms. It explains that all environments change over time, either gradually or suddenly, and these changes influence organisms. During an ice age, large areas of land were covered in ice for thousands of years. Now the Earth is warming due to human activities, so organisms will need to move, adapt, or become extinct. The document also describes primary and secondary succession in ecosystems and how human activities like pollution, invasive species, and deforestation impact the environment.

1. Unit 5 Lesson 3 How Do Environmental Changes
Affect Organisms?
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2. Change Comes Naturally
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• 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?

3. Change Comes Naturally
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• What kinds of changes to the environment may
have happened during the last ice age?
Unit 5 Lesson 3 How Do Environmental Changes Affect Organisms?

4. Change Comes Naturally
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• 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.
Unit 5 Lesson 3 How Do Environmental Changes Affect Organisms?

5. Next, Please!
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• 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.
Unit 5 Lesson 3 How Do Environmental Changes Affect Organisms?

6. Next, Please!
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• 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.
Unit 5 Lesson 3 How Do Environmental Changes Affect Organisms?

7. Next, Please!
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• 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.
Unit 5 Lesson 3 How Do Environmental Changes Affect Organisms?

8. For Better or Worse
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• 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.
Unit 5 Lesson 3 How Do Environmental Changes Affect Organisms?

9. Invasive Species
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• 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.
Unit 5 Lesson 3 How Do Environmental Changes Affect Organisms?

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• 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.
Unit 5 Lesson 3 How Do Environmental Changes Affect Organisms?
Humans Change the Environment

11. Humans Change the Environment
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• 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.
Unit 5 Lesson 3 How Do Environmental Changes Affect Organisms?

12. Gone!
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• 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.
Unit 5 Lesson 3 How Do Environmental Changes Affect Organisms?

13. Gone!
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• Could the extinction of the dodo bird have been
prevented? Why or why not?
Unit 5 Lesson 3 How Do Environmental Changes Affect Organisms?