KEY CONCEPT Darwin’s voyage provided insight on evolution.

Darwin observed differences among island species. Variation is a difference in a physical trait. Galápagos tortoises: Saddle-backed tortoises have long necks and legs and live in areas with a lot of tall plants. Domed tortoises have shorter necks and legs and live in wet areas with short plants.

Darwin observed differences among island species. Galápagos finches: Finches with strong, thick beaks live in areas with a lot of large, hard-shelled nuts, while finches with more delicate beaks are found where insects or fruits are widely available.

An adaptation is a feature that allows an organism to better survive in its environment. Species are able to adapt to their environment. Adaptations can lead to genetic change in a population.

Darwin observed fossil and geologic evidence supporting an ancient Earth. Darwin found fossils of extinct animals that resemble modern animals. Ex.- Glyptodon, a giant extinct armadillo that resembled living armadillos. He also found fossil shells of marine organisms high up in the mountains, showing great changes that occurred in the past.

Geologic evidence included: Land that had been underwater was moved above sea level due to an earthquake, demonstrating that daily geologic processes can add up to a great change over a long period of time.