1. Chapter 24 ~Macroevolution Origin of Species

2. What is a species? A population whose members have the potential to interbreed and produce viable, fertile offspring + Horse Zebra Zorse = not-fertile

3. Patterns of Evolution Divergent Evolution 2 or more species originate from a common ancestor

4. Patterns of Evolution Convergent Evolution 2 unrelated species share similar traits due to adaptation to similar environments Unrelated species will never evolve into a single species

5. Patterns of Evolution Parallel Evolution 2 or more related species make similar evolutionary changes

6. Patterns of Evolution Co-Evolution Two interacting species evolve together

7. Macroevolution Large-scale evolution: –The descent of different species from a common ancestor over many generations. For macroevolution to occur, two populations must be reproductively isolated (or separated) from one another Over time, the two populations of beetles are eventually considered different species, since they can no longer produce viable, fertile offspring.

8. Pre-zygotic Isolating Mechanisms Isolating mechanisms that prevent fertilization Ova/egg

9. Pre-zygotic Isolating Mechanisms 1) Habitat Isolation 2 populations live in different habitats and rarely meet Ex. Terrestrial vs. Aquatic Garter Snakes

10. Pre-zygotic Isolating Mechanisms 2) Behavioral Isolation 2 populations can not recognize differences in courtship rituals 2 subspecies of tropical finches have been separated enough to have variations in song that they do not recognize

11. Pre-zygotic Isolating Mechanisms 3) Temporal Isolation 2 populations that breed during different times of day or seasons Day vs. Night Blooming Lily

12. Pre-zygotic Isolating Mechanisms 4) Mechanical Isolation incompatible sex- organs/genitalia 5) Gametic Isolation Sperm can not survive in the reproductive tract of females or gametes fail to recognize each other

13. Post-zygotic Isolating Mechanisms Fertilization is successful, but zygote is prevented from developing into a viable adult Ova/Egg

14. Post-zygotic Isolating Mechanisms 1) Hybrid Inviability – genetic incompatibility causes early miscarriage 2) Hybrid Sterility - Hybrid is viable, but sterile 3) Hybrid Breakdown – Hybrid is viable and fertile, but its offspring is sterile

15. Modes of Speciation (How new species are formed) 1)Allopatric SpeciationAllopatric Speciation 2)Adaptive RadiationAdaptive Radiation 3)Sympatric SpeciationSympatric Speciation

16. Allopatric Speciation ~ “other” ~ “homeland” Allopatric When a speciation occurs due to geographic isolation between two populations Back to Modes of Speciation

17. Adaptive Radiation Type of allopatric speciation Rapid evolution of many species from a single ancestor due to colonization of an area w/diverse conditions (ex. Darwin’s finches) Back to Modes of Speciation

18. Sympatric Speciation When new species are formed w/o a geographic barrier (more common in plants) This can an occur due to the following reasons: –Polyploidy –Allopolyploidy –Balanced Polymorphism

19. Sympatric Speciation (due to polyploidy) Mutant condition occurs when a non-disjunction error in meiosis causes gametes that are diploid. Mutant zygotes are triploid (3N) or tetraploid (4N) as a result and can propagate a new species

20. Sympatric Speciation (due to allopolyploidy) Type of hybridization When two different species interbreed and combine their chromosomes Usually sterile, but can breed new species asexually

21. Sympatric Speciation (due to balanced polymorphism) When there are different phenotypes in a population, members can self-isolate and “selectively breed” with those of their own. Over time, two populations of differing phenotypes (ex. colors) can evolve into two different species

22. Does macroevolution occur gradually or suddenly? Two models of evolutionary thought: 1) Gradualism 2) Punctuated Equilibrium Gradualism Evolution occurs due to -gradual accumulation of small changes over time ** not supported by fossil evidence, since existence of “intermediate” fossils are few or inadequate to support the theory [;’p ; Punctuated Equilibrium Evolution occurs due to -abrupt changes in the environment (ex. Catastrophes) that drives rapid speciation -New species appear quickly, then changes very little over time ** supported by fossil evidence