unit 5 lesson 3 how do environmental changes affect organisms? · 2020-02-05 · copyright ©...

Unit 5 Lesson 3 How Do Environmental ChangesAffect Organisms?

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Unit 5 Lesson 3 How Do Environmental Changes Affect Organisms?

Change Comes Naturally


• All environments changeover time. Some changeshappen slowly and someoccur quickly.

• Climate changes, orchanges to weatherpatterns, affect organisms.

• An ice age happens whenEarth’s temperatures arecolder than normal for avery long time. Largeareas of land are coveredin ice for thousands ofyears.




• Earth is now in awarming cycle, duein part to humanactivities. As areasbecome warmer,organisms will move,adapt, or disappear.

• Natural events, suchas floods, mudslides,or volcanic eruptionscan change theenvironment quickly.




• A forest fire canseem harmful toecosystems, thoughsome ecosystemsdepend on fires tostay healthy.• Some seeds just

don’t grow until theyare burned.


Next, Please!


• The gradual change of organisms in an ecosystem is calledsuccession.• 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, addingnutrients to the soil.


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• Plants grow as soil develops. Mosses flourish, producing moresoil. Bigger plants take hold and, eventually, trees grow.

• This establishes a mature, stable community. This process cantake hundreds of years.


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• Secondary succession occurs where an ecosystem has beendisturbed, but soil is still present.

• Secondary succession occurs more quickly and uses existing soilthat 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.


Next, Please!



For Better or Worse


• Organisms living in anenvironment can cause bothharmful and helpfulchanges.

• For example, beavers cutdown trees that providefood and shelter for otherliving things in order tomake a dam.

• The dam also slows the flowof water to animals.However, dams alsoproduce wetlands, providinghomes for other organisms.


For Better or Worse



Invasive Species


• Invasive species grow quickly after beingintroduced into a new environment.

• Invasive species take food and space away fromnative species, the organisms already living in anecosystem.

• Invasive and native species compete for food.


Invasive Species



Invasive Species



• The Japanese honeysuckle covers the ground with thicktangles of vines and leaves.

• A full grown honeysuckle uses large amount of water andblocks sunlight, preventing native plants from growing.

Invasive Species




• Human activities such as1. Open-pit mining.2. Cutting down forests.3. Building highways.Can harm an ecosystem.

4. Humans produce waste, whichends up in landfills. Theselandfills can pollute soil andwater.

• Pollution is the contamination ofair, water, or soil by substancesharmful to organisms.


Humans Change the Environment



• Not all changes caused byhumans are harmful.

• Conservation is the act ofprotecting ecosystems andthe organisms living in them.

• Humans practice conservationby

1. Replanting trees.2. Cleaning up pollution.3. Removing invasive plants

and animals.4. Caring for injured animals.


Gone!


• Some organisms do notsurvive changes in theenvironment.

• Extinction happens whenall the members of acertain species dies.

• For example, giant reptileslike the Tyrannosaurus rexlived in a time when theEarth was warm. As theenvironment cooled, theybecame extinct.


Gone!



unit 5 lesson 3 how do environmental changes affect organisms? · 2020-02-05 · copyright ©...

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