Orgin of Species is an amazing work that one should read because it answers many questions.
The selected works of Charles Darwin bring forth a number of questions that will be answered in the following paragraphs with the help of outside sources and paraphrasing of the text itself.
Why must Darwin establish the principle of variation under nature? What is the role of this basic principle in his theory of evolution?
The reason why Darwin must establish the principle of variation under nature is so that he can explain why some varieties become permanent and others cease to exist. The principle of variation under nature explains how varieties are affected by their surrounding. Because of the nature that surrounds an animal there is a necessary struggle with other animals. The dominant species are able to reproduce and their offspring's are to some degree modified. All species, whether domesticated or wild, will produce offspring which are slightly different from the parents. The offspring have therefore inherited advantages that will allow them to become the dominant species. Darwin states that because of this the most flourishing and dominant species are part of a larger genera.
The principle of variation under nature is an important point in the theory of evolution.The large genres that are created because of variation under nature vary the most and they tend to convert into new and distinct species. In other words the species of a large genera evolve over a large period of time and become very new and distinct species. Darwin also point out that large genera tend to break up into smaller genera and because of this we have groups subordinate to groups.
What is the "Struggle for Existence?" How does it interact with natural selection?
Every species during its lifetime goes through a hard time. During this period there might be shortage of food or the season might be a difficult one. Darwin gives examples ranging from plants struggling against drought to plants competing for birds to eat their fruit and disseminate their seeds. If this was the not case species would multiply at a very high rate and the world could not hold them. In the book The Struggle for Existance author Walter Thomas Mills writes Part of the evidence for this struggle is the immense potential that animal and plant populations have to increase in size. As more species multiply then can survive there is a struggle for existence. This struggle can be with another species or with hard life conditions. Darwin emphasizes that he used the phrase "struggle for existence" in a large and metaphorical sense, including dependence of one being on another.
Darwin writes Under nature, the slightest difference of structure or constitution may well turn the nicely-balanced scale in the struggle for life and so be preserved. Natural selection plays a big role in the struggle for existence. The species that have been modified over time and have many varieties have an upper hand in the struggle for life because of natural selection.
How do we know that the principle of natural selection applies in nature? Describe one of the examples Darwin offers to substantiate this claim.
We know that the principle of natural selection applies in nature because the species we have today were not created that way. Darwin writes We cannot suppose that all the breeds were suddenly produces as perfect and as useful as we now see them. Through natural selection the species we see in nature today are present.
Darwin uses domestic pigeons to substantiate this claim. He lists some of the points of variation in pigeons: the shape of bones, the number of vertebrae and ribs, the proportion of facial features, the size of inner structures like the esophagus, the number and shape of wing and tail feathers, even the appearance of the eggs and the differences between males and females. Having established the tremendous variety in pigeons, he then explains what makes these variations important: all of the breeds are all thought to descend from the rock pigeon Columba livia. In his book Pigeons: The Fascinating Saga of the World's Most Revered and Reviled Bird author Andrew Blechman explains why Darwin chose fancy pigeons to substantiate his claim. Blechman writes This is the crux of why Darwin singled out fancy pigeons, aside from the personal affection he eventually acquired for them. Their incredible diversity arose from a well-documented history that was believed to travel all the way back to a single origin. They showed very clearly the radiating quality of evolution over time.
How do processes of selection in nature differ from the deliberate selection and development of domesticated breeds? How are they similar? Why is this distinction important to Darwin's overall theory?
Unlike in natural selection, deliberate selection does no permanently alter the domesticated breeds. For example, a man will breed two of the best dogs in order to get as good of a dog as he can. This man does not however have any intention of permanently altering this entire breed of dogs.
There are some similarities in the two forms of selection. In both cases the conditions of life, and the reproduction are highly important in causing variability. Darwin explains that the intercrossing of species has played an important part in the origin of our domestic productions.