Darwin's Theory Of Evolution By Natural Selection

Biology Evolution Essay

The theory of evolution is one of the great explanations of human history, drastically changing our view of the world. Evolution is the process of biological change by which descendants come to differ from their ancestors. Charles Darwin proposed his theory of evolution and supported it with a great body of evidence and examples. In Darwin's time, most scientists fully believed that each organism and each adaptation was the work of the creator. Yet Darwin proposed his theory of evolution by natural selection .

While on his voyage , Darwin encountered exotic plants and animals that challenged his thinking and led him to consider scientific evidence in new ways.In the Galapagos Darwin collected samples of mockingbirds, and later observed that the birds were somewhat different on each island. This made him wonder that the birds had a common ancestor,he would later figure out this was

caused by variation. Some differences seemed well suited to the animals environments and diets. For example finches with strong thin beaks lived in areas with a lot of large, hard-shelled nuts while those species of finch with more delicate beaks were found where insects or fruits were widely available. This led Darwin to realize that species may somehow be able to adapt to their surroundings. All of this helped him formulate the ideas of an old earth and slow gradual change to the evolution of organisms.
After his voyage, Darwin spent more than 20 years conducting research while thinking about how evolution occurs.

Darwin noticed a lot of variation in domestic plants and animals. Breeders would select certain traits to produce a great amount of diversity. This was know as artificial selection , the process by which humans change a species by breeding it for certain traits. Darwin used this line of thinking for his theory of natural selection, the complete opposite. Natural selection the process whereby organisms better adapted to their environment tend to survive and produce more offspring. Therefore , in nature characteristics are selected only if it gives the animal an advantage in their environment. Natural selection explains how evolution can occur. There are four main principles to the theory of natural selection. Variation is associated with heritable differences and overproduction results in competition . Adaptation allows individuals a better chance of survival. Descent with modification is when the environment plays a role so that traits are passed

on.
Darwin found evidence from a wide range of sources to support his argument for evolution. The three most important and convincing supports came from fossils , geography, embryology, and anatomy. Fossils contain a "snapshot" of what animals of that age looked like . Older fossils are found lower down in soil. Though digging you could compare the different fossils and identify if they are they same animals at different time periods of evolution. Geography showed Darwin that different habitats affected the organisms traits and characteristics . Embryology shows that different organisms look similar and develop similarly in their early stages of development, it is guessed that they came from a common ancestor. Some of Darwin's best evidence came from anatomy, comparing the body parts of different species. He discovered there were two structures : Analogous and homologous. With all of this evidence, it left no doubt in scientists minds that all organisms have a past history .