Visiting a Humane Society shelter can be a sad affair, and one that can make animal-lovers angry. See that tiny dog in the photo? Its owner gave it up for "lack of space." LACK OF SPACE?! That little guy could have lived in a shoebox!
Having said that, animal shelters (and adoption days that pet stores sometimes sponsor) are great places to see the incredible amount of variety that exists within one species of organism. Charles Darwin, writing in "On the Origin of Species," used dogs as an example of this sort of variation:
But let us look to the familiar case of the breeds of dogs: it cannot be doubted that young pointers (I have myself seen striking instances) will sometimes point and even back other dogs the very first time that they are taken out; retrieving is certainly in some degree inherited by retrievers; and a tendency to run round, instead of at, a flock of sheep, by shepherd-dogs. I cannot see that these actions, performed without experience by the young, and in nearly the same manner by each individual, performed with eager delight by each breed, and without the end being known--for the young pointer can no more know that he points to aid his master, than the white butterfly knows why she lays her eggs on the leaf of the cabbage--I cannot see that these actions differ essentially from true instincts. If we were to behold one kind of wolf, when young and without any training, as soon as it scented its prey, stand motionless like a statue, and then slowly crawl forward with a peculiar gait; and another kind of wolf rushing round, instead of at, a herd of deer, and driving them to a distant point, we should assuredly call these actions instinctive. Domestic instincts, as they may be called, are certainly far less fixed than natural instincts; but they have been acted on by far less rigorous selection, and have been transmitted for an incomparably shorter period, under less fixed conditions of life.
How strongly these domestic instincts, habits, and dispositions are inherited, and how curiously they become mingled, is well shown when different breeds of dogs are crossed. Thus it is known that a cross with a bull-dog has affected for many generations the courage and obstinacy of greyhounds; and a cross with a greyhound has given to a whole family of shepherd-dogs a tendency to hunt hares. These domestic instincts, when thus tested by crossing, resemble natural instincts, which in a like manner become curiously blended together, and for a long period exhibit traces of the instincts of either parent: for example, Le Roy describes a dog, whose great-grandfather was a wolf, and this dog showed a trace of its wild parentage only in one way, by not coming in a straight line to his master, when called.
So consider visiting a pound, shelter, or adoption day and observing, drawing, describing or photographing the differences among breeds (and crosses!), to help fulfill this standard:
1. Structure and Function in Living Systems
1. Living things are diverse with many different observable characteristics.
The following short video clip from HHMI helps tell the story very well:
http://www.hhmi.org/biointeractive/dog-breeding
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