Speciation Chapter 16 –Section 3 Speciation-The Formation of a New Species 1. Common ancestors arrive in an environment. There is diversity in the gene pool causing a variety of phenotypes. 2. Geographic isolation Due to competition members of a population are driven to different locations. i.e. The other side of the river, another island, out of the forest and into the desert… 3. Changes in the Gene Pool. Due to differing environments, the phenotypes that are naturally selected for are different for each environment. Each population drifts towards it’s own fittest phenotypes 4. Reproductive isolation After many generations of Natural Selection leading the two populations of organisms towards different phenotypes, the two populations are no longer able to reproduce with each other. 5. Ecological Competition Even if the two populations begin to mix in the same environment again, their phenotypes are so different that competition drives them towards different behaviors and food sources. 6. Continued Evolution As the generations pass, the phenotypes continue to drift apart, as the behaviors and food sources are not similar. • Write a paragraph explaining how the speciation of the two tortoises on the Galapagos Islands may have evolved from the same ancestor.