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  • 1. Biological Species Concept How We Define Species
  • 2. Objectives• Define Biological Species Concept• Name the eight barriers that define a species• Categorize the barriers as either geographic or reproductive• Categorize the barriers as either prezygotic or postzygotic• Remember and understand the basis for each of the categories• Provide examples for each of those barriers
  • 3. Biological Species Concept• The biological species concept emphasizes reproductive isolation through prezygotic and postzygotic barriers that can result in separating the gene pools of different populations.
  • 4. Vocabulary• Geographic Isolation – • Reproductive Isolation Refers to being separated – Refers to being by space. separated by not being able to reproduce.
  • 5. Vocabulary Cont.• Prezygotic (Before • Postzygotic (After fertilization) – Refers fertilization) – Refers to a time before the to a time after the sperm and egg fuse. sperm and egg have fused.← Before this point After this point →
  • 6. Table 1 – Barriers between SpeciesBarriersPrezygotic 1. Habitat Isolation 2. Temporal Isolation 3. Behavioral Isolation 4. Mechanical Isolation 5. Gametic IsolationPostzygotic 6. Reduced Hybrid Viability 7. Reduced Hybrid Fertility 8. Hybrid Breakdown
  • 7. 1. Habitat Isolation• Same as Geographic Isolation
  • 8. 2. Temporal Isolation• Mate at different times
  • 9. 3. Behavioral Isolation• Different courtship rituals (mating signals)
  • 10. 4. Mechanical Isolation• Physically can’t mate
  • 11. Mechanical Isolation Cont.• More mechanical isolation
  • 12. 5. Gametic Isolation• When sperm can’t fertilize the egg
  • 13. 6. Reduced Hybrid Viability• When hybrids can’t develop This salamander is frail and underdeveloped.
  • 14. 7. Reduced Hybrid Fertility• When the hybrids develop but can’t reproduce Horse + Donkey = Mule (The mule is sterile; it can’t reproduce)
  • 15. 8. Hybrid Breakdown• When hybrids reproduce but their offspring can’t Hybrid A + B = C C can’t reproduceHybrid: A C B
  • 16. Table 2 – Classification of Barriers in Relation to Zygote FormationClassification Prezygotic Postzygotic Pre-mating Pre- Post-fertiliztion fertilization Barriers Habitat Mechanical Reduced Hybrid Viability Isolation Isolation Temporal Gametic Reduced Hybrid Fertility Isolation Isolation Behavioral Hybrid Breakdown Isolation
  • 17. Check Your Understanding• What is one example of a POST-mating but PRE-zygotic barrier?
  • 18. AnswerClassification Prezygotic Postzygotic Pre-mating Pre- Post-fertiliztion fertilization Barriers Habitat Mechanical Reduced Hybrid Viability Isolation Isolation Temporal Gametic Reduced Hybrid Fertility Isolation Isolation Behavioral Hybrid Breakdown Isolation
  • 19. Table 3 – Classification of Barriers in Relation to Isolation TypeClassification Isolation Geographic Reproductive Barriers Habitat Isolation Temporal Isolation Behavioral Isolation Mechanical Isolation Gametic Isolation Reduced Hybrid Viability Reduced Hybrid Fertility Hybrid Breakdown
  • 20. Check Your Understanding• Out of 8 barriers, how many are geographic?
  • 21. AnswerClassification Isolation Geographic Reproductive Barriers Habitat Isolation Temporal Isolation Behavioral Isolation Mechanical Isolation Gametic Isolation Reduced Hybrid Viability Reduced Hybrid Fertility Hybrid Breakdown
  • 22. Table 4.1 – Making Sense of the BarriersClassification Don’t meet Do meet Do meet Do meet Don’t have sex Do have sex Do have sex Don’t Do fertilize fertilize Offspring have issues Barriers Habitat Temporal Gametic Reduced Isolation Isolation Isolation Hybrid Viability Behavioral Reduced Isolation Hybrid Fertility Mechanical Hybrid Isolation Breakdown
  • 23. Check Your Understanding• What were the four bolded classifications?
  • 24. AnswerClassification Don’t meet Do meet Do meet Do meet Don’t have sex Do have sex Do have sex Don’t Do fertilize fertilize Offspring have issues Barriers Habitat Temporal Gametic Reduced Isolation Isolation Isolation Hybrid Viability Behavioral Reduced Isolation Hybrid Fertility Mechanical Hybrid Isolation Breakdown
  • 25. Table 4.2 – Making Sense of the Barriers (Translated)Classification Don’t meet Do meet Do meet Do meet Don’t have sex Do have sex Do have sex Don’t Do fertilize fertilize Offspring have issuesBarriers Location Timing Sperm and Don’t grow egg can’t fertilize Behavior Can’t reproduce Physical Children can’t reproduce
  • 26. Check Your Understanding• What was the pattern for Barriers in each column?
  • 27. Answer 1 3 1 3Classification Don’t meet Do meet Do meet Do meet Don’t have sex Do have sex Do have sex Don’t Do fertilize fertilize Offspring have issuesBarriers Location Timing Sperm and Don’t grow egg can’t fertilize Behavior Can’t reproduce Physical Children can’t reproduce
  • 28. Summary• You have just been introduced to the Biological Species Concept.• You also learned about the 8 barriers between species.• Now that you have the basics, read Ch. 24, Overview and Concept 24.1