Origin of Species - Darwin's Classic Work
Origin of Species is the abbreviated, more commonly-known title for Charles Darwin's classic, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. British naturalist Charles Darwin (1809-1882) began drafting Origin of Species in 1842, just six years after returning from his fateful five-year voyage aboard the HMS Beagle (1831-36). Heavily influenced by Sir Charles Lyell's Principles of Geology (1830-1833, a three volume work) and Thomas Malthus' An Essay on the Principle of Population (1798), Origin of Species was ultimately published in 1859.
Origin of Species - Natural Selection
In Origin of Species, Charles Darwin introduced the concept of natural selection. Natural selection is a natural process which acts to preserve and accumulate minor advantageous variations within living systems. Suppose a member of a species were to develop a functional advantage (a reptile grew wings and learned to fly: an obvious advantage his earth-bound relatives couldn't enjoy); its offspring would inherit that advantage and pass it on to future offspring. Natural selection would act to preserve the advantageous trait. Essentially, natural selection is the naturalistic equivalent to domestic breeding. Over the centuries, human breeders have produced dramatic changes within domestic animal populations simply by selecting individuals to breed. They have been able to accentuate desirable traits (given the trait is already present in the creature's genetic code) and even suppress undesirable traits gradually over time. The difference between domestic breeding and natural selection is this: rather than human breeders making the selections, nature itself is the selector.
Darwin made a keen observation but he drew a poor conclusion. He thought that since natural selection can and does produce slight variations within animal populations it should therefore be able to explain all of the variety we observe in biology. He concluded that since natural selection explains variety, all life must somehow be related, everything ultimately having evolved from some sort of common ancestor. "It is a truly wonderful fact-the wonder of which we are apt to overlook from familiarity-that all animals and all plants throughout all time and space should be related to each other…"  Darwinists have even gone so far as to suggest that this common ancestor somehow evolved from non-living matter (which they presume to be some kind of dirty-water soup-like composition). Well, this whole idea of the birds and bananas, the fish and the flowers, all being related, and life evolving from non-life… may have seemed remotely plausible back in the 1800s. Modern biology was still in its infancy and the living cell was still thought to be nothing more than a simple blob of protoplasm. Gregor Mendell (1822-1884) had only just begun exploring the principles of heredity and it wasn't until the late 1850's that Luis Pasteur (1822-1895) sought to disprove the abiogenesis fallacy. But thanks to the foundations laid by these great men of science (both of whom opposed Darwinian evolution) and in light of the tremendous advances we've made in molecular biology, biochemistry and genetics, especially over these past fifty years, the flaws in Darwin's theory standout quite clearly. For example, we've established that genetic barriers exist. Pigs will never fly! Yes, there are degrees of variation. Different skin tones, facial features, eyes colors, hair types, etc. You could have a big dog or a small dog, a dog with long or short hair. But no kind of dog will ever produce a non-dog! Birds and bananas aren't distant cousins! As far as life arising from non-life (abiogenesis), the mechanisms are fairly well known and the bottom line is this: certain chemical constraints make abiogenesis an impossible event.
Origin of Species - Henslow's Advice
If ever you find yourself sitting down to read Darwin's Origin of Species, keep in mind John Stevens Henslow's (1796-1861) advice to the young Charles Darwin. Henslow was one of Darwin's professors at Cambridge. In fact, it was Henslow who recommended Darwin to Captain Robert FitzRoy (1805-1865) of the HMS Beagle. Before Darwin set sail, Henslow recommended that he take Sir Charles Lyell's Principles of Geology. Lyell's book had a profound impact upon the young Charles and its influence is seen throughout Darwin's work. Henslow advised Darwin, "By all means read it for the facts, but on no account believe the wild theories."  We seek to pass this advice on to you. By all means read it for the facts, but on no account believe the wild theories.