SpeciationWhat are species?How do we identify them?How do they form?Types of reproductive isolation• Prezygotic mechanisms - prior to embryo formation– Habitat– Temporal– Behavioral– Mechanical– Gametic• Postzygotic mechanisms -after embryo formation– Hybrid inviability– Hybrid sterilityPrezygotic mechanisms• Habitat: parasite infects new host species• Temporal: Flies active at different time of day breeding at different temperaturesPrezygotic mechanisms• Behavioral: Courtship sequence differs• Mechanical: Bits don’t fit together• Gametic: Incompatible gametes; sperm cannot penetrate egg; dies early in female repro tractI.D.-ing reproductive isolation• Prezygotic mechanisms - prior to embryo formation• Postzygotic mechanisms -after embryo formation• All require observation of mating behavior, reproductive success and offspring viability• OK for some contemporary species, but what about:– Fossil species?– Hard to watch or catch species?– Rare or endangered species?Species Concepts– Biological: Are two groups actually or potentially interbreeding?– Morhological: Are two groups (fossils) sufficiently different from each other?– Phylogenetic: Are two groups bound by common ancestry? Do they form monophyletic groups?ICE SHEETS DIVIDE RANGESSympatric Speciation? Yes! When Natural Selection Occurs1. Write the two standard Hardy-Weinberg equations and define each of the terms.2. Explain what requirements must be met for a population to be in Hardy-Weinberg equilibrium.3. While visiting the tropics, you observe birds that are sexually dimorphic. You decide to investigate the effects of the exaggerated traits of the males (coloration and plumage) on fitness. What experiment would you design?4. In a population of fish living in a tropical reef, females are completely yellow and males are yellow with bright red stripes down their sides. A mutation causes a young male to be completely red, and this new coloration attracts more females than the original coloration. He therefore has a higher reproductive output, and his male offspring also have the new coloration. Determine whether evolution has occurred. Be sure to explain your rationale.5. Compare and contrast directional, disruptive, and stabilizing selection. Be sure to provide an example of each in your discussion.6. Describe how three of the evolutionary forces can cause evolution.7. Explain the use of Hardy-Weinberg equilibrium as a null
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