Charles Darwin (1809 -1882) “In the struggle for survival, the fittest win out at the expense of their rivals because they succeed in adapting themselves best to their environment."

Darwin Facts Joined the crew of the H.M.S. Beagle as its naturalist in 1831. Beagle's 5-year voyage explored South Pacific, coast of South America, and the Galápagos Islands. Studying Galápagos wildlife, especially the finches, contributed to Darwin’s theory of natural selection.

Origin of the Species In 1859, Darwin published "On the Origin of Species," which described his theory of natural selection. According to Darwin: fight for survival among members of the same species led to the survival of those with the most favorable characteristics. The "fittest" members had more offspring.

How Did Darwin Explain Diversity of the Finches? He proposed that all the finches came from a single common ancestor and became more specialized to suit their environment.

Finch Facts Darwin found 13 different species unique to Galapagos islands. All sparrow-sized and similar in appearance: brown, green, black feathers. Each species evolved according to its particular food source. Different beak shapes. Large ground finch developed a broad, wide beak, for cracking hard seeds. Cactus ground finch has long, down curved beak for digging food out of cactus flowers. Some feed on insects or peck at seabirds and feed on their blood.

Darwin’s Finches Finches 1–7 are ground finches. They look for food on the ground or in low shrubs. Finches 8–13 are tree finches and feed on insects. 2, #3, #6 have stout beaks for eating seeds. #7 has a beak like a woodpecker used to drill holes in wood. Uses a cactus spine held in its beak to dig out the insect.

Organisms Struggle to Survive Basic purposes of life are to survive and reproduce. All forms of life must gather resources to live. Threats include abundance of/competition for food, water, sunlight, shelter. Threats to habitat from climate change and humans. Predation.

Key Term: Natural Selection Process by which species adapt to their environment. An organism’s ability to survive and reproduce. Commonly known as “survival of the fittest.” Leads to evolutionary change when organisms with certain characteristics have a greater survival or reproductive rate than other organisms and pass inheritable characteristics to their offspring.

Darwin’s Postulates Variation exists among individuals within a species. Vitiations in behavior are heritable. Differential Reproduction is due to behavioral differences. Some survive better than others. Survival and Reproduction is not random.

Why Did the Finches Survive? No predators - no mammals and few reptiles on the islands. No competitors - only a handful of other types of songbirds. No humans.

Various Finch Beaks