Types of Natural Selection

Selection that favors the extremes of a population trait is DISRUPTIVE SELECTION.

An example of this would be the size of clams.  Predators find it harder to locate smaller clams and are unable to pry open larger clams.  Predators favor clams of a medium size.

disruptive selection  
smaller                                                                                   larger
Size of Clams
Graph linked from Spark Notes on "Types of Natural Selection"
clams      
introduction
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introduction
 objective
 theory
 selection types
 you try
 describing
 assess others