Introduction to ecosystems
Introduction to ecosystems

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Introduction to ecosystems

6.3.1 Darwin’s arrival on the Galápagos Islands

Although it is possible to follow in Darwin’s footsteps, as Dr David Robinson demonstrates in this video, the habitat has changed substantially as a consequence of the introduction of alien animals in the past. There are very few of the larger islands where you can see ecosystems unaffected by alien introductions and thus see them as Darwin saw them.

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Darwin’s arrival on the Galápagos Islands

DR. DAVID ROBINSON
On the 8th of October, 1835, the survey ship, HMS Beagle, anchored in this bay. On board was Charles Darwin. And he and four companions were put ashore on this island for a week - an island that he described as both picturesque and curious. In Darwin's day it was called James Island. Today it's known as Santiago. At almost 600 square kilometres, it's one of the larger islands in the Galapagos. Its highest point is 900 metres above sea level. On Santiago, Darwin met two Spaniards who were hard at work butchering tortoises for their meat. Together, they had an uncomfortable walk across this lava field. Eventually they arrived at this volcanic lake where the Spaniards collected salt to use as a preservative. Darwin was fascinated by local flora and fauna. He described the Galápagos as a world within itself - full of creatures that were both curious and remarkable. The islands were teeming with wildlife. There were so many land iguanas, for instance, that Darwin found it difficult to pitch his tent without covering their burrows. Today, there are none left on Santiago. In total, Darwin spent five weeks on the Galápagos - experimenting, observing, and collecting specimens. As for tortoise meat, he noted that it tasted particularly good when roasted in its shell.
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The finches that Darwin brought back from the Galápagos hold a special place in the history of the development of the theory of evolution by means of natural selection. There are 13 species and they occupy different niches in the habitats on the islands.

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Finches on Galápagos

DR. DAVID ROBINSON
Although he didn't realise it at the time, the most important specimens that Charles Darwin brought back from the Galápagos were finches. Initially, he wasn't sure how they were related. But when back in England, they were examined by the ornithologist John Gould, he reported that, in fact, Darwin had brought back 13 different species of finch all of which were unique to the Galápagos. This realisation played a significant role in Darwin's formulation of his theory of evolution. The most important differences between the finches came in their beaks. Some were large, some were small. Each one was suited to the availability of particular foodstuffs. Eventually, Darwin theorised that different species of finch had evolved on different islands, their distinctive beaks being an adaptation to distinct natural habitats or environmental niches. In the years since Darwin's visit, many other scientists and ornithologists have come to the Galápagos to study its finches. In this experiment, researchers are observing the woodpecker finch using this wooden box to stand in for a tree. The woodpecker finch is one of the only birds to use tools to help it find food. A stick or small twig enables it to dig deeper into tree bark for insect larvae. This skill enables it to survive in conditions which other birds would find difficult. In the dry season, it can gather up to 50% of its food in this way. Woodpecker finches are hungry birds, which in the wild need to eat every three hours, so they never turn down the chance of a free meal.
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