Biology Extra Credit 2014

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by amandaking18
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Evolutionary Biology

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Biology Extra Credit 2014

Who is Charles Darwin?Charles Darwin was a naturalist and geologist who contributed many ideas to the theory of evolution. During his trip on the HMS Beagle, he recorded many observations of the plants and animals he saw on different islands; the most important island being the Galapagos Islands. His trip to the Galapagos Islands led him to understand what casues plants and animals to evolve. After reviewing all of his observations, he was curious as to the geographical distribution of various wildlife and fossils. He wondered why finches varied from one island to the other. Today, we call this adaptive radiation. His travels led him to develop his three most famous theories: natural selection, speciation, and common descent.

In his book On the Origin of Species, Charles Darwin proposed the theory that all living things are desceded from a common ancestor. There is several forms of evidence that help to prove that every living organism comes from a common ancestor such as genetic code,amino acid sequences, phylogenetic trees, etc.

Speciation is the process of multiplication. This occurs when one population splits into two reproductively isolated populations. One of the main things that caused Darwin to develop the idea of speciation were the finches of the Galapagos Islands. He correctly believed the finches had each descended from one Central American species and multiplied on the islands. New species were created as populations became adapted to filling different roles on the island. His observation led Darwin to discover that new species form by gradual evolution from an ancestral population, eventually leading to two distinct species.

Darwin realized that every population has individuals that all slightly vary from one another. The individuals that have a variation that gives them an advantage in staying alive long enough to reproduce, are the ones that pass on their traits to the next generation. This means their traits become more common and the population evolves. Darwin called this "descent with modification."Finches are an example of this process. The birds that lived in arid environments and who had beaks better suited for eating cactus, were able to obtain more food. As a result, they were able to mate more successfully; as is the case for all species of finches etc. Basically, nature selected the best adapted varieties to survive and to reproduce (survival of the fittest). This process is known as natural selection.




Charles Darwin


1) Physical traits and characteristics allow species to survive (fitness). 2) Fitness results from adaptation.3) Adaptations result from natural selection and result in EVOLUTION.

Natural Selection

Common Descent


Amanda King P.6


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