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Biological Species Concepts To maintain species Prezygotic Barriers - Habitat isolation - Behavioral isolation - Temporal isolation - Mechanical isolation - Gamete isolation Postzygotic Barriers - Reduced hybrid viability - Reduced hybrid fertility - Hybrid breakdown Where the Biological concept DOES NOT work – • Inadequates for grouping extinct forms of life. • Meaningless for organisms that reproduce asexually. • Some species interbreed and produce viable hybrids but maintain separate species. Ex. Wolves, domestic dogs and coyotes. Also deer mouse that maintain fore subspecies. • Discovering more cases of “ what is a subspecies and what is a full species?” • Catching populations at different stages of evolution. For these reasons, other species concepts are being evaluated. 1. Morphological – taxonomy 2. Recognition – mating adaptations (rituals). 3. Cohesion – each species is defined by its set of genes. Can use this to include organisms that reproduce asexually and hybrids. 4. Ecological – Where organisms live and what they do (roles) rather than phenotype. 5. Evolutionary – Defines a species as a sequence of ancestral populations with a specific set of forces of natural selection and unique role in the environment. • Biological concept needs isolation of the gene pool. • The other concepts recognize genetic exchange between species. • Which concept(s) depends on the question you are asking about a species. Talking about populations that are genetically discrete, that have originated from genetic isolation.