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The Nature of Species • Speciation: the process by _________ ________________________________ – transformation of ________________ ______________________________ – or by the ______________________ ______________________________ species The Biological Species Concept • Ernst Mayr’s _____________________ ________________________________ defines species as… “…groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups.” – In short: population whose __________ ______________________________ 2 How and why do new species originate? • Species are created by a series of evolutionary processes – populations become ___________________ • ___________________________ isolated • ____________________________isolated – isolated populations ____________________________________ • Isolation – _______________________ • geographic _________________________ – ___________________________________ • still live in __________ area The Nature of Species • Sympatric speciation: the differentiation of populations within a ______________________________ into species • Species that occur together: – _________________________________ – _________________________________ – _________________________________ – __________________________________ 4 The Biological Species Concept • Reproductively isolated: populations whose members do not mate with each other or who cannot produce fertile offspring have _____________________ ___________________________ __________________________. 5 The Biological Species Concept • Prezygotic isolating mechanisms ________ ___________________________________ – Ecological isolation • Utilization _______________________ _______________________________ • _______________________________ each other • Example: Lions and tigers are ecologically isolated. 7 Biological Species Concept • Behavioral isolation: species differ in their ____________________ • Avoid mating with members of the wrong species by using: – ________________ – ________________ – ________________ _________________ – _________________ _________________ Biological Species Concept • Temporal isolation: species reproduce in ____________________ or at __________ __________________________________M echanical isolation: _______________ __________________________________ between species prevent mating • Prevention of gamete fusion: _________ of one species _______________________ with the gametes of another species or within the reproductive tract of another species 9 Biological Species Concept • Postzygotic isolation ________________ ___________________________________ into reproducing adults • Hybridization: mating between two different species with a ________________________ ____________________________________ Hybrids often: – Do not develop into adults – Do not develop into fertile adults 10 Geography of Speciation • Is geographic isolation required for speciation to occur? • Sympatric speciation occurs ________________ __________________________________________ Instantaneous speciation through – Polyploidy: individuals that have __________ ___________________________________ Plants ______________________________ (________________________) can survive, but not be fertilized by diploid individuals • Individual is reproductively isolated from all 11 other members of its species Geography of Speciation • Allopolyploidy: _____________________ – Resulting offspring have _____________ _________________________________ – Is infertile: ________________________ with either species – Can reproduce ____________________ – Can become fertile if ________________ _________________________________