Aim: What is the theory behind life’s great diversity ? Key Idea 3 Individual organisms and species change over time. Objective: Explain how the three processes of Evolution worked together to yield our present organisms

Evolution is the change of species over time. The diversity of life (millions of different species) on Earth today is the result of natural selection occurring over a vast amount of geologic time The origins of evolutionary thought was laid during the 1700s and 1800s. Charles Darwin Evolution: Who Was Charles Darwin? He was born in Shrewsbury England on Feb 12, 1809 into a well-off family of doctors and industrialists. But his upbringing wasn’t entirely conventional. After five yeas as naturalist aboard the BEAGLE he married his cousin Emma Wedgwood.

On a five-year voyage on the Beagle, Charles Darwin visited several continents and many remote islands. Darwin’s observations led to a revolutionary theory about the way life changes over time. Section 15-1 Darwin saw a great deal of diversity during his travels. During a single day in a Brazilian forest he collected 68 different beetle species.

Giant Tortoises of the Galápagos Islands Section 15-1 Pinta Tower Pinta Island Intermediate shell Marchena James Fernandina Santa Cruz Isabela Santa Fe On Darwin’s visit to the Galapagos Islands off the coast of South America, he made observations on the characteristics of the giant tortoises from the different islands. Make a list of the different characteristics of the tortoises. Among the tortoises, the shape of the shell corresponds to different habitats. The Hood Island tortoise has a long neck and a shell that is curved and open around the neck and legs, allowing the tortoise to reach the sparse vegetation on Hood Island. The tortoise from Isabela Island has a done-shaped shell and a shorter neck. Vegetation on this island is more abundant and closer to the ground. The tortoise from Pinta Island has a shell that is intermediate between these two forms. Hood Island Saddle-backed shell Floreana Hood Isabela Island Dome-shaped shell

Hood Island Tortoise On relatively dry islands, tortoises with long necks had a slight edge over the tortoises with slightly shorter necks -- long necks, and the notch in their shell that allows them to fully stretch it, allow an individual to reach the foliage on the plants that grow on the island

Isabella Island Tortoise This Tortoise has traits that helped the animal survive on an Island with lush, low vegetation

Darwin’s Book On the Origin of Species Based on Darwin’s travels and observations, he proposed a mechanism for evolution that he called Natural Selection. .