Among many other things, Charles Darwin was a pigeon breeder and used breeding as a demonstration of how selection for certain traits could bring changes. Using selective breeding (A.K.A. artificial selection) you can get an organism that didn't exist before!
People have been selectively breeding animals and growing plants to achieve desired outcomes for thousands of years. The American Foxhound, for instance, didn't exist 400 years ago! It’s the result of breeding an English foxhound with a French hound. American Foxhounds were bred by European settlers wishing to adapt their dogs to the land and game in America.
Today, KTS kids were tasked with creating a new breed of dog. The assignment? Breed a dog to help protect a group of entomologists working during the summer season in an area inhabited by wild bears. The dog breed would need to alert the scientists to approaching bears and to scare them away. Students were given a selection of dogs with various traits such as bark volume, fur length, and ear shape. They then selected two of the existing breeds they felt would most likely produce a successful new breed and determine the resulting offspring's characteristics.
Over several generations of selectively "breeding" their dogs, KTS kids were successful in creating a dog with short hair for those hot summer days, loud barks and pointy ears!
So what is the fourth clue they learned today? Selected traits can pass on to the next generation. Today, the kids were the breeders, the ones to decide what traits would pass from parents to offspring. But who selects in nature?