Where there was a large supply of seeds on the ground, for instance, short-beaked finches became more common, because these beaks were better at cracking open the seeds. Each type of beak had evolved for a specific task. Darwin concluded that the traits of the different populations of finches had changed over time, and that these variations were related to different environments in the islands.

Some finches, for instance, had long, narrow beaks, while others had short, thick beaks. In fact, they were different species of finches with a variety of traits. How does this relate to finches? On the Galápagos Islands, some finches appeared so different from others that Darwin did not realize at first that they were all finches. If the environment changes, natural selection will then push organisms to evolve in a different direction to adapt to their new circumstances. Organisms therefore gradually become better-suited for their environment. Offspring with traits that make them more likely to survive, mature, and reproduce in the environment they inhabit pass on their traits to the next generation.Īs this happens generation after generation, natural selection acts as a kind of sieve, or a remover of undesirable traits. Sometimes summed up by the phrase “survival of the fittest,” natural selection is based on the following principles: In nature, organisms produce more offspring than are able to survive and reproduce. During a voyage in the 1830s, Darwin had observed these birds on the Galápagos Islands, a group of islands in the Pacific Ocean west of South America.

In laying out the evidence for his theory of evolution by natural selection in his 1859 book, On the Origin of Species, the British naturalist and biologist Charles Darwin highlighted the physical traits and behaviors of several species of bird called finches.

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