CH15Evolution

 Chapter 15: Evolution

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 * Speciation** [|(Download Copy)]


 * Definition:** Process by which new species evolve from ancestral species

A permanent barrier to breeding between members of the same species (Isolation)
 * Requirements:**


 * Types of barriers:**

Physical barrier separates a population into groups Ex. River, mountain range, ocean, volcano, etc.
 * Geographic isolation**

Occurs when members of the same species are prevented from producing fertile offspring Ex. Different mating seasons, differing flowering times, polyploidy (type of mutation—plants get extra sets of chromosomes, sometimes many extra sets, they can’t reproduce with a normal member of its species.
 * Reproductive Isolation**


 * Rate of Evolution**

Evolution or speciation occurs slowly and steadily over millions of years (slow and steady change over time)
 * Gradualism:**

Species stay the same unless there is some type of pressure to change. When environmental changes exert pressure, change occurs rapidly.
 * Punctuated Equilibrium:**

Fossil evidence supports both types.


 * Patterns of Evolution**

Related species become less alike
 * Divergent Evolution**

Members of the same species adapt to a variety of environmental conditions and radiate out into separate species through divergent evolution and isolation
 * Adaptive Radiation**
 * **Darwin’s Finches**

Unrelated species become more similar--occurs when unrelated species adapt to similar environments ex. sharks and dolphins; bats and butterflies; american cacti and african euphorbs
 * Convergent Evolution**