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Theory of Evolution - Coggle Diagram
Theory of Evolution
Evolution Before Darwin
At the time Darwin began his famous journey on The Beagle, most people believed that all organisms had been created separately. A few biologists, such as Jean-Baptiste Lamark, had proposed that one species could evolve into another, but his ideas were not well-accepted.
The study of fossils was also different. Biologists recognized the fossils represented species that had gone extinct and had completely died out. They believed, however, that extinction only occurred during dramatic events, like enormous volcanic eruptions, floods, and other catastrophes. They did not recognize extinction as a relatively common event in the history of Earth.
Charles Darwin
When Darwin set sail in 1831, it was not his goal to study evolution. The captain of The Beagle had invited him as a guest on the voyage to keep him company during the long months at sea. The mission of the ship was to survey the coastline of different countries to make maps for the British navy. While the crew worked, Darwin rowed ashore to study the plants, animals, and fossils he found.
What he saw began to intrigue him more and more. Most biologists of the time were content to study a few species in-depth and describe all of the details of their anatomy and physiology. Darwin did the same thing, but also began considering larger patterns of what species occurred together in one place. He also looked at how existing species compared to fossils found in the same area.
Darwin’s Fossils
Darwin also studied fossils. In South America, he found the fossilized bones of extinct mammals among fossils from mollusks that were still alive. Seeing a mix of fossils that showed extinct animals and animals that were still alive led Darwin to question the idea that extinction was a rare event that only occurred because of a catastrophe. He began to wonder whether extinction was a regular event that occurred naturally, and often.
The similarity between his fossils and living animals made Darwin wonder if they were somehow related.
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Alfred Wallace
Another man, however, developed almost the exact same idea at almost the same time. Alfred Wallace was a biologist who worked in Brazil and Indonesia.
Wallace allowed Darwin to take most of the credit, and Wallace is unfortunately forgotten by many who study biology. Wallace’s contributions, however, are considered to be as important and unique as Darwin’s.
Other Scientists
One thing Darwin and Wallace knew nothing of was genetics. They proposed that organisms could evolve over time, but they had no idea how genetic information was passed on to future generations. If a member of a species had some special trait, like being especially fast, why did their offspring also have this trait? Neither Darwin nor Wallace knew.
The completion of the theory of evolution would require the research of Gregor Mendel to show how genetic information was contained in genes. It would also require the work of the many other scientists discussed who showed how genetic information was contained in chromosomes and DNA. With the discovery of the structure of the DNA molecule by Watson and Crick in 1953 , biologists were finally able to put all of the pieces of evolution together.
Galapagos Islands
One of Darwin’s most famous research sites were the Galapagos Islands off of the coast of Ecuador. The Galapagos are volcanic islands like Hawaii. Since the islands had never been connected to a continent, all of the plants and animals that lived there have floated, swam, or flown to the island.