In 1831, at the age of just 22, Charles Darwin was hired as the naturalist on board HMS Beagle as it set off on a five-year voyage to create maps of new territories for the British Admiralty. One of these unchartered regions was the Galapagos, an isolated group of volcanic islands in the Pacific. It was here that Darwin made observations and collected specimens that he later acknowledged as an inspiration for his ideas on evolution by natural selection and the origin of new species.
Darwin and his insights from the Galapagos are so important they have even made it onto the GCSE biology syllabus! But contrary to what the textbooks would have our students believe, Darwin wrote almost nothing about the Galapagos finches, describing them as “an inexplicable confusion”. But it was the work of evolutionary biologists that followed, notably Peter and Rosemary Grant, that established the radiation of Galapagos finches – also referred to collectively as “Darwin’s finches” – as a perfect illustration of how one species can give rise to many.
In a lunchtime talk to the Year 10 Athenaeum, biology teacher Dr Henry Nicholls described how changes in the environment – like a drought – can lead to the death of certain individuals in a population, with the survivors passing on the particular traits that helped them get through the tough times to their offspring – like larger bills. Through this process of natural selection species change in appearance over time. This is how a single colonising population of one species of finch, estimated to have reached Galapagos around 3 million years ago, has since diverged into 14 different species, some feeding on seeds, some on cactuses, some on insects, and some – the sharp-beaked or vampire finch – on the blood from open wounds of other birds.
The same pattern of a rare colonisation event, followed by divergence and speciation, is now a familiar story across the Galapagos archipelago, explaining why there are 14 species of giant tortoise, 15 species of Scalesia, several different Opuntia cacti, more than 10 species of flightless weevil and over 70 species of land snails, each adapted to occupy its own unique microhabitat.
The students worked in pairs to collect answers to key questions from the talk. Those with the highest scores walked away with a penguin biscuit, a nod to the Galapagos penguin, the world’s smallest penguin species and the only one to stray into waters north of the equator.