1114 Chapter 12

  1. Morphological Species Concept
    • Organisms of the same species share more similar characteristics with each other than those of different species because of a longer shared evolutionary history.
    • Forest elephants are half the weight of savanna elephants, straighter tusks, rounder ears, deeper bellow sounds
  2. Genetic Species Concept
    • Organisms of the same species share more similar DNA than those of different species because of a longer shared evolutionary history
    • Forest and Savanna elephants DNA as different from each other as Asian elephants and woolly mammoths
  3. Biological Species Concept
    • Species are groups of organisms that can interbreed and produce fertile offspring and are reproductively isolated from other species
    • Savanna and forest elephants elephants only produce fertile females, but sterile males
  4. Whit links the biological, morphological, and genetic species concepts?
    Members of the same species linked by shared evolutionary history via ability to exchange genetic information
  5. Limitations for Biological Species Concept
    • Hybrids (offspring produced by 2 species mating)
    • Extinct organisms
    • Asexually reproducing species
  6. Limitations for Morphological Species Concept
    Variation within species is tremendous
  7. Limitations for Genetic Species Concepts
    How different is enough difference in relation to the DNA
  8. Speciation
    The process by which populations attain reproductive isolation
  9. Reproductive Isolation
    Biological barriers that impede members of different species from interbreeding and producing viable, fertile offspring
  10. 2 Categories of Reproductive Isolation
    • Prezygotic Barriers: prevent mating or fertilization if matting does occur
    • Postzygotic Barriers: prevents hybrid offspring of 2 species from developing into viable, fertile adults
  11. Pre-zygotic Barrier: Mechanical Isolation
    Duck genitalia: variation in morphology decreases the liklihood that males and females of different species will have compatible genitalia
  12. Pre-zygotic Barrier: Temporal Isolation
    • Species breed during different time of day, season, or year and thus can't mix gametes
    • Example: bitternut and shagbark hickory both wind pollinated but butternut flowers in June/July, where shagbark flower in April/May,
  13. Pre-zygotic Barriers: Behavioral Isolation and Mate Recognition
    • Mating behavioral differences prevent mating:
    • Incorrect courtship displays
    • Can't recognize mating signals
  14. Postzygotic Barriers: Reduced Hybrid Viability and Infertility
    • Reduced Viability: hybrids either fail to develop or are very frail and unlikely to survive
    • Hybrids may be sterile or have lower fertility: e.g. mules (male donkey + female horse = sterile mule offspring)
  15. 3 other biological barriers to reproduction OTHER than geographic isolation
    • Size
    • Cellular make up of sperm & egg
    • Pheromones
  16. Allopatric Speciation
    • Gene flow prevented by geographic isolation of a previously continuous population
    • Allo= other, patra= homeland
    • Can occur via vicariance and dispersal
  17. Vicariance
    • Population split by the formation of a geographic barrier
    • --Allopatric speciation occurs if populations accumulate enough genetic differences that they couldn't mate even if the barrier was removed
  18. Allopatric Speciaton via Dispersal
    Distance as a result of movement to new areas results in reproductive isolation as populations are no longer continuous
  19. Drosophila dispersal in Hawaii
    • Drosophila dispersed to new islands as they formed and only reproduced with individuals on the home island
    • Causing reproductive isolation
  20. Image Upload 1
    Which phylogeny matches the allopatric speciation?



    A)
  21. Why might Drosophila from the Hilo and Kona locations experience reproductive isolation?
    Vicariance: geographic barrier (Mauna Loa and Mauna Kea
  22. Parapatric Speciation
    • Geographically continuous population over extremely vast distances 
    • Para= through, patra= homeland
    • Individuals at either end of distribution functionally isolated from each other -> often experience distinct selective pressures
  23. Speciation hypothesis based on morphological observations
    Image Upload 6
    • Ancestral population with features similar to picta originated in the north
    • As groups moved southward on either side of the valley, they couldn't interbreed and gradually became reproductively isolated
    • Different species where E and W populations rejoined
  24. Image Upload 7 Image Upload 8
    Yes, because the top portion is eastern species and the bottom clade represent the western species
  25. Image Upload 9
    Why is orgeonensis represented on many branches of the tree?
    DNA analysis revealed differences within subspecies that aren't apparent via morphology
  26. Ring Species
    • Continuous populations over large geographic ares form a ring that can interbreed except where the populations rejoin
    • Remains a serious classification challenge!
  27. Sympatric Speciation
    • Speciation occurs in populations that live in the same geographic area
    • Example: Lake Victoria Fish that have blue light dominant in shallow water vs. red light dominant in deep water
    • --After many generations, reproductive isolation has blue species in shallow water exclusively and red in deep water.
  28. 2 Models for Rates of Speciation
    • Punctuated Equilibrium: rapid bursts of speciation followed by relatively little change
    • Image Upload 10
    • Gradual Model: species diverge steadily over time
    • Image Upload 11
  29. Adaptive Radiation
    • Periods of evolutionary change in which organisms form many new species with adaptations specialized to different niches
    • Often occurs after mass extinctions or when new areas are colonized
  30. Niche
    The specific biotic and abiotic resources used by a species
  31. Why don't adaptive radiations result in multiple species utilizing the same niche?
    • Differential Survival
    • Competitive Exclusion
    • Resource Partitioning
  32. Differential Survival
    If multiple species are competing for the same resource, then one will win
  33. Competitive Exclusion
    • 2 species will never be perfectly equally successful at utilizing a resource so more successful competitor will exclude the other from its niche
    • Inferior competitor either goes locally extinct or utilizes different resources
  34. Resource Partitioning
    Similar species can coexist in an area if they use different sets of similar resources or the same resource at different times
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1114 Chapter 12
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