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How do genetic traits change? Changes caused by man or nature may influence the genetics of organisms. Here is an example of a change that happened because nature changed the area.

 

Squirrels of the Grand Canyon: 

Originally there was only one species of squirrel living in the Grand Canyon. As the Grand Canyon deepened and widened, the group of squirrels on the north side of the canyon got separated from the group on the south side. The squirrels separated on the north side now have black fur, while the squirrels on the south side have red fur. The separation of the two groups caused them to evolve different traits. The two groups are becoming more and more genetically different and in time will likely become two different species.

 

Galapagos Finches:

As Charles Darwin conducted research on the Galapagos Islands, he noticed differences in finches from island to island.  One of the biggest differences was the sizes and shapes of the birds’ beaks. The shape of the beak is an example of an adaptation, or change over time that helped the birds survive. Remember the activity "I Will Survive!" You should have learned that differences in beak shapes make obtaining food either easier or harder for the bird.

 

Now read about differences that have happened in species as a result of man's influence on the species.

 

Corn and Cows:

People have been selectively breeding plants and animals for a long time.  Native Americans produced corn by selectively breeding a species of weed.  The corn they produced had ears that were only three inches long.  cowModern science has increased the length of the ears to a foot long. Farmers cross cows that produce the most milk to create new generations of cows that produce increasing amounts of milk.

   

Extensions:

Google and Read any of the following topics:

  1. Industrial melanism.
  2. Mimicry
  3. Genetic engineering
  4. Plant hybridization

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Teachers should view the Teacher Site Map to relate Sci-ber text and the USOE 7th grade science core.


Updated October 24, 2008 by: Glen Westbroek

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