text: One book titled for these concepts, written by a barnacle expert, discusses the problem of why this concept exists.
full_question: One book titled for these concepts, written by a barnacle expert, discusses the problem of why this concept exists. Ernst Mayr developed the modern version of this concept, based on actual or potential reproductive isolation. Gause's law says that if two of these are in competition for the same resource, one will eventually drive out the other. The formation of these groups can be caused by barrier introduction, and new ones can emerge from adaptive radiation. For 10 points, this taxonomic classification below "genus," on whose origin Darwin wrote.
first_sentence: One book titled for these concepts, written by a barnacle expert, discusses the problem of why this concept exists.