The first principle of Darwin’s theory is that individuals vary in many heritable traits, and that no two individuals are exactly alike. He first noticed this during his observations of the different plant and animal species he collected from the Galapagos Islands. He learned that most of these species lived nowhere else in the world, although they resembled species from the mainland of South America. After the voyage he began to see how the environment and evolution are closely related. Since the time of Darwin we have discovered the role genes play in passing on different traits to future generations.
His second principle is that the reproductive potential of a population would increase exponentially if all individuals reproduced successfully, far exceeding the capacity of the environmental resources to support it. This inequality creates a struggle for survival among individuals within that environment. This struggle leads to the death of the individuals who are not able to survive within the environments limitations, and the only individual remaining reproduce. Depending on the resources that are available, as in food, water, weather, etc., part of the population will not be able to survive and reproduce.
Third, individuals who are best fit for the current environment leave a disproportionaly large number of offspring compared to individuals who are not fit. When that happens over many generations a species’ gene pool changes to only include the traits that are a best fit for ensuring survival of that species, and a new species may evolve. In the case of the Galapagos finches Darwin studied, biologists have since found that one of the differences was their beak size, which were adapted to the specific seeds available to the finches as food on the different islands. This would support this principle as only the birds able to eat the local seeds would be able to survive to reproduce, thus over many generations, new finches with a variety of different beak sizes would “evolve”.
The fourth principle is the effects of unequal reproductive success over many generations will lead to a gradual change in the population. Thus a species’ population can evolve over time; the individual itself does not evolve. The individual’s traits may or may not be favored by the environment, helping it to survive and reproduce or eliminating the traits from the gene pool.
Charles Darwin revolutionized biology, among all the sciences, in ways most people could not even fathom. During his lifetime it was unheard of to question that the earth and its inhabitants were not made by God, yet he saw things and studied them and came up with a theory that unified most of the sciences we study today. That theory is that evolution occurs by the process of natural selection. Darwin’s four main principles do support his theory.
Works Cited:
Campbell-Reece, 2002
Phillip Pepe, 2005
