Speciation Ch 14

What is a species Numerous definitions Biological Species Concept Morphological Species Concept Ecological Species Concept Phylogenic Species Concept

Evolutionary Theories

Creating a Species Reproductive Isolation Reproductive Barriers – Prezygotic Barriers – Postzygotic Barriers

Prezygotic Barriers Temporal Isolation Habitat Isolation Behavioral Isolation Mechanical Isolation Gametic Isolation

Postzygotic Barriers Reduced Hybrid Viability Reduced Hybrid Fertality Hybrid Breakdown

Speciation Emergence of a new species Allopatric vs Sympatric – Creation of reproductive barriers

Parent species 2n = 6 Tetraploid cells 4n = 12 1 Diploid gametes 2n = 6 2 Viable, fertile tetraploid species 4n = 12 Self- fertilization 3 Sympatric Speciation Niche separation, sexual selection, habitat differentiation Polyploid

Sympatric Speciation Hybrid Polypoid Species A 2n = 4 Gamete n = Species B 2n = 6 Gamete n = 3 Sterile hybrid n = 5 Chromosomes not homologous (cannot pair) Viable, fertile hybrid species 2n = 10 3

Hybrid Zones Regions where different species meet and mate Outcomes – Reinforcement – Fusion – Stability

Adaptive Radiation Evolution of diverse species from common ancestor Colonization Extinctions

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