SpeciationChapter 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 isolationDue 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 isolationAfter 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 CompetitionEven 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 EvolutionAs 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.