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BIOL 103 Lecture Notes - Ploidy, Gamete, Adaptive Radiation

Course Code
BIOL 103
Peter T Boag

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Species and Speciation
- Finch speciation via dispersal and adaptation
o Allopatric model of finch speciation says species diverge on different
islands (allopatry) and eventually coexist on same island (sympatry)
o Step 1: immigrants from mainland colonize Galapagos
o Step 2: can occur repeatedly as birds disperse to other islands and
adapt to local foods genetic drift also likely
o Step 3: birds recolonize island where their ancestors lived; if
sufficiently distinct, have two species, otherwise merge back into
single species
- How are species formed?
o Gradually in situ or by more rapid division of ancestral population
o Usually allopatric, sometimes in sympatry
- How do species persist?
o Gene flow reduced by ‘RIMa’
- Variation within and between groups of organisms is common
- Morphospecies were the traditional way of describing species, going back to
the Latin naming system created by Swedish biologist Carl Linnaeus in the
mid 1700s
o Works where clear groups are defined by reliable characters
o ‘Monkeyflow’ species of the genus Mimulus share distinct floral
morphology and other traits associated with their preferred
pollinators and habitats
- Morphospecies concept not so useful for species with lots of intraspecific
variation; but if variants can freely interbreed in nature and produce fertile
offspring they can be described by the ‘biological species concept
championed by Ernst Mayr in the 1960’s
o All dog varieties belong to the species Canis lupus familiaris a
subspecies of the gray wolf
o Related species such as African jackals like Canis adustus don’t
naturally interbreed with dogs due to geographic or genetic isolation
- Increased availability of objective markers of shared common ancestry from
molecular sequences have increased the popularity of the ‘phylogenetic
species concept
o There are isolated populations of elephants on 2 continents, but the
phylogenetic species concept confirms no more and no less than three
species populations within each species are too similar to form
distinct branches
- Different species concepts each have strengths and weaknesses more than
one may be useful depending on context and question
Species concept
Widely applicable
Based on
Not applicable to
asexual species
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