閱讀筆記 S6048 Darwin’s Finches

Science 6048
Darwin’s Finches
Why were the beaks of birds living on the Galápagos Islands worth studying?
ln the middle of the Pacific Ocean, near the equator and west of Ecuador, lie the Galápagos Islands. These volcanic islands are the site of studies done by the scientist Charles Darwin. His research there led to the creation of his most well-known theories.
Finches, small, sparrow-like birds, live on the islands. With the help of a colleague, Darwin learned that there were 13 different species of finches on the islands. The birds were all about the same size, and they had similar coloring. The main difference that Darwin noticed was in the birds’ beaks.
Darwin came to the conclusion that all these different species of finches had an ancestor in common. He believed that over time, they developed different types of beaks to suit different needs. Some had beaks that were suited for crushing, which would be useful for eating seeds. Others had grasping beaks that could hold twigs or thorns and use them as a tool to pull insects from tree branches.
Even though the Galápagos finches have beaks that allow them to eat special foods, their general eating habits don’t vary that much from species to species. Instead, they are able to survive difficult times—such as times of drought or intense competition—because of their specialized beaks.
Darwin’s study of the finches led to his theory of natural selection. He believed that certain traits in a species make it better able to survive. Over time and many generations, the traits that benefit the animal become more common. For example, a certain type of coloring in a moth might protect it from predators. According to Darwin, future generations of the moth would have this coloring because it helps the species survive.
ln recent years, scientists have watched an example of this theory unfold. Traits usually evolve over a long period of time. In just about 20 years, though, one of Darwin’s finches developed a smaller beak so that it could eat smaller seeds. In the past, it fed on seeds of different sizes. Then, another species of finch came to the island and began eating all the larger seeds. A drought also caused greater competition for the existing food. The finches that had smaller beaks were better able to survive these changes. It was a perfect illustration of Darwin’s theory of natural selection—in the very same place he had originally formed his theory.

為甚麼居住於加拉巴哥群島鳥類的喙嘴值得被研究呢?
Charles Darwin將加拉巴哥群島中一些島嶼的鳥類做了研究
發現儘管屬於同是種類的鳥類，它們的鳥嘴形狀、大小並不盡相同
研究的結論為
會造成這些不同的原因是當他們在生存的過程中，碰上了不同挑戰與考驗
為了因應這些變因繼續生存下去， 體上的構造便會隨著一代一代緩慢改變
而現今發現擁有這些特徵的生物辨識經過大自然的淘汰及篩選所存活、傳承下來的基因型態