Species formation

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Species formation
2012-02-06 23:34:32

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  1. Species
    • defined by Linneaus-morphological species concept
    • Simply if they look alike they are related
    • Morphospecies
  2. Lineage species concept
    • Each species has a history
    • --Speciation event (split on tree)
    • --Extinction
    • --Two daughter species
  3. Sexual dimorphism
    -male and female of same species look different
  4. Sibling species
    -different species are superficially identical but are different
  5. Biological species concept- Mayr
    Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups

    Keep sexual lineages seperate
  6. Dobzhansky-Muller
    • Lineage splits
    • New allele becomes fixed at different loci in each They can hybridize
    • Lethal
    • Functionallyinferior
  7. Hybrid sterility
    • Species similar enough to each other but not of same species, mate to produce offspring
    • Offspring are sterile
  8. How new species arise
    • interbreeding
    • speciation
    • Dobzhansky-Muller
  9. Interbreeding
    • -daughter species
    • Over time the species will have different population and become 2 different species
  10. Speciation
    • allopatric
    • sympatric
  11. Allopatric
    - population of species become geographically isolated and accumulates enough difference through time reproductive isolation and formation of new offspring
  12. Believed to be reason for speciation
    • 1.Vicarience
    • 2.Founder events-founding pop that splits from parent pop Throughtime founding pop will become its own species
  13. Adaptive radiation
    -explosion of many new ecologically diverse species developing in an area in a short period of time from single ancestor
  14. Sympatric
    • -speciation occurs in same geographic location
    • 1.exploitation of niches- IE chikled fishes
    • 2.polyploidy-quickly change in as little as 2 generations Common in plants, rare in animals
  15. Polyploidy
    • -duplication of set of chromosomes within individuals
    • Single species-autopolyploidy
    • Two different species- allopolyploidy
  16. autopolyploid
    • Tetraploids NO w/diploids
    • But tetraploids w/ tetraploid complete isolation in 2 generations
  17. Allopolyploid
    Interbreeding of closely related Offspring often fertile bc chromosome pair w/almost identical
  18. What happens when newly found species come together
    • Hybrid zones may form if reproductive isolation is incomplete
    • If hybrids are fit, mating occurs with parentals from both pop
    • If hybrids less fit, complete isolation evolves Hybridzone- where two distinct pop reproduce regardless Yellowbellied toad- hybrids are abnormal yet wildtype will mate
  19. Why rate of speciation vary
    • Dietary shifts--predatory v herbivorous
    • In plants--animalpollinated faster than wind pollinated
    • Columbines--longer spurs>shorter => restict # pollinator species
  20. Prezygotic barriers
    • -before mating or fertilization or formation of zygote
    • Spatial isolation
    • Temporal isolation
    • Mechanical isolation
    • Gametic isolation
    • Behavioral isolation
  21. Postzygotic barriers
    • -after mating or fertilization
    • Prevents hybrid gametes producing viable offspring
    • In play when prezygotic barriers fail

    • hybrid zygote abnormality
    • hybrid sterility
    • low hybrid viability
  22. hybrid zygote abnormality
    -zygote will be unfit for reproduction/survival
  23. hybrid sterility
    -parents of different species produce offspring offspring is normal but cant repoduce
  24. low hybrid viability
    -much less fit than parents or purebred offspring
  25. Evolutionary radiation
    • - speciation exceed extinction rate
    • --Occurs following mass-extinction
    • --Large number of daughter species from single ancestor