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Chapter 24 - Origin of Species Macroevolution Macroevolution refers to any evolutionary change at or above the species level. What is speciation? What prevents cross-species mating in the flycatcher? What would happen if two birds from different species did mate? A. What is a Species? - a group of actually or potentially interbreeding populations - a hybrid is an offspring of two distinct species, example: Liger, Mule Several similar species can live in the same area, but interbreeding is not advantageous. Hybrids are often infertile. There are mechanisms that prevent this type of mating. B. Reproductive Isolating Mechanisms Prezygotic ("before formation of a zygote") a. Habitat isolation b. Temporal isolation c. Behavioral isolation d. Mechanical isolation e. Gamete isolation (incompatibility) Postzygotic ("after formation of a zygote") a. Zygote mortality b. Hybrid sterility c. F2 fitness C. Modes of Speciation 1. Allopatric speciation: 2. Sympatric speciation: 3. Divergent Speciation occurs when species form, existing at the same time, likely in different locations 4. Phyletic Speciation occurs when a new species completely replaces an older species. D. Adaptive Radiation 1. Adaptive radiation is a rapid development from a single ancestral species of many new species. Example: WORD ATTACK!.........Compare and Contrast the terms in each set. Prepare an illustration to share with the class for the set you are assigned to. 1. Phyletic Speciation / Divergent Speciation 2. Zygote mortality / Hybrid Sterility 3. Behavioral / Temporal / Habitat / Geographic Isolation 4. Adaptive Radiation / Polymorphism / Dimorphism 5. Species / Subspecies / Hybrid 6. Premating Isolation / Post-mating Isolation 7. Allopatric / Sympatric Speciation 8. Disruptive / Directional / Stabilizing Selection 9. Sexual Selection / Nonrandom Mating / Assortative Mating 10. Gene Pool / Gene Flow / Genetic Drift 11. Microevolution / Macroevolution 12. Founder Effect / Bottleneck Effect