I believe Darwin made the conscious decision to start with domesticated organisms first, because his argument is something any educated person could agree with. We have all seen litters of kittens or puppies, raised fish, or grown flowers, or at least known people who have done these things. Even today, which has much greater urbanization than existed in Darwin's time, we are aware that dog breeds are exquisitely different from each other, yet all German Shepherds are not alike. If you want to argue about variation within a population, you do not start with white oak trees, brown bear, and large-mouthed bass. Only a specialist would be aware of the intrinsic variation within distinct members of these organisms. But take a dog or feral cat or farm animal/plant as an example and most people would be inherently familiar with the idea of variation, even if they had never considered it. Darwin makes us consider it. Once we have recognized the diversity within organisms for which we have a great deal of experience, we can then appreciate the diversity that exists in organisms for which we have much less experience.
The first part of this chapter is somewhat derivative with the previous chapter. Variation exists. What I found compelling was Darwin begins to address the species concept in this chapter and notes the difficulties inherent with it. We also discuss varieties aka breeds or sub-species and the subjectiveness of classification.
An example of the first:
Darwin then gets into a discussion of the amount of variation within common species and within larger genera. The idea here is that members of a species that is wide-spread and colonizes/survives in a variety of different environments has more variation than members of a species that is only found in precise or limited environments. He then takes these arguments to make the following predictions:
and the test of these predictions
Finally, Darwin leaves us with a synopsis of species differences within large genera that, in my mind, serves as an initial argument for incipient speciation. This is the '
What are your thoughts?