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Adaptation and Evolution of Populations

Natural selection favors certain traits in a population so that the organism adapts to its environment; changes in the genes over time is evolution.

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Salamander Speciation

Salamander Speciation

Credit: Chris Brown
Source: http://en.wikipedia.org/wiki/File:Ensatina_eschscholtzii_klauberi.jpg
License: CC BY-NC 3.0

This salamander is of the genus and species Ensatinaeschscholtzii, and is found along the western United States, from British Columbia down to Baja California. There are seven subspecies, all established within California.

Amazing But True!

Credit: Oregon Caves
Source: http://www.flickr.com/photos/100953877@N07/10332346525
License: CC BY-NC 3.0

There are many subspecies of the Ensatina around the world [Figure2]

  • Ensatina is a ring species, with different subspecies living at different locations.
  • One set of Ensatina live in the Sierra Nevada Mountains. The other set live in the Coast Range. Their ranges make a horseshoe around the Central Valley.
  • The subspecies at the ends of the horseshoe are very different from one another.

Show What You Know

With the link below, learn more about speciation. Then answer the following questions.

  1. What happens over time to populations of the same species that are separated geographically?
  2. What was the ancestor of the different subspecies and where does it live?
  3. What strategy for protection from predators did the salamanders use that lived in the Sierra Nevada Mountains, the eastern part of the salamander’s range?
  4. Moving south along the Sierra Nevada, what changes happen in the subspecies?
  5. What strategy for protection from predators did the salamanders in the western part of the range use?
  6. Are the two subspecies that are furthest south different species?
  7. Why would Charles Darwin have liked this example?

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Image Attributions

  1. [1]^ Credit: Chris Brown; Source: http://en.wikipedia.org/wiki/File:Ensatina_eschscholtzii_klauberi.jpg; License: CC BY-NC 3.0
  2. [2]^ Credit: Oregon Caves; Source: http://www.flickr.com/photos/100953877@N07/10332346525; License: CC BY-NC 3.0

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