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

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.  Modern science has increased the length of the ears to one foot long.  Farmers cross cows that produce the most milk to produce new generations of cows that produce increasing amounts of milk.

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 bird beaks.  Each bird had the type of beak it needed to survive.  Finches that ate insects had sharp needlelike beaks.  Those that ate seeds had strong, wide 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.