Darwin was an English naturalist, he studied variation in plants, animals and fossils whilst on his 5-year voyage around the world during the 19th century.
During Darwin's 5 year voyage he visited the Galapágos Islands, where he observed many organisms finches, tortoises and mocking birds.
Darwin's theory of evolution challenged the commonly held Christian views of his era, that God made all the animals and plants that live on Earth. Darwin did not publish his scientific work and ideas until 28 years after he completed his voyage.
As a result of Darwin's expeditions and observations, he proposed the theory of evolution by natural selection (For more on natural selection visit the natural selection page)
Darwin proposed in the theory of natural selection that:
Individuals with characteristics most suited to the environment are more likely to survive to breed successfully.
The characteristics that have enabled these individuals to survive are passed on to the next generation
individual organisms within a particular species show a wide range of variation for a characteristic