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Lecture

BIOL 103 Lecture Notes - Ploidy, Gamete, Adaptive Radiation


Department
Biology
Course Code
BIOL 103
Professor
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
Criterion
Advantages
Disadvantages
Morphological
Anatomical
difference
Widely applicable
Subjective
Biological
Reproductive
isolation
Based on
evolutionary
Not applicable to
asexual species
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