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how to evolution advance according to ernst mayr?
by speciation, which is the production of new gene complexes capable of ecological shifts
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what is the keystone of evolution according to Mayr
species
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taxonomists
science of defining groups of biological organisms on shared characteristics and giving names to those groups
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are species real?
yes individuals cluster in morphospace corresponding to geno and phenotypic space.
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what can help us find ancestor
morphology and molecular clock (rate of decay)
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what example in class showed organisms that were only distinguishable on the basis of karyotype
agrodiaetus butterflies
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what is the natural category in the taxonomic hierarchy?
species
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hierarchy from species
genus, family, order
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what did darwin think of species
extension of the spectrum of variation seen within species (rhetorical necessity)
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what was the problem with Darwin's definition of species?
there is usually a disconnect between variation within a species and variation among species
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species paradox
darwin taught us to think of species as dynamic, changing entities, yet seeking to create an all embracing species concept, we place boxes around changing things
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what is dobzhansky's definition of species
group of organisms barred from interbreeding with other similar groups by its physiological properties (sterility of hybrids or incompat of parents)
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mayr's definition of species
species are reproductively isolated from other groups
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problems with BSC
- not work with fossils
- or asexual species
- ring species
- varying degrees of reproductive isolation
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what is an example of ring species
phylloscopus warblers
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alternative species concepts
- cluster of organisms that is distinct from other lineages and within which there is a common ancestor (phylogenetic)
- ecological (occupies the same zone)
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what is different about alternative species concept and BSC?
alternative emphasize outcomes of history. BSC emphasizes process
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in practice what do we rely on for distinguishing species
morphology
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prezygotic barriers
- ecological
- temporal
- sexual/behavioral
- mechanical
- gametic incompatibility
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example of ecological reproductive isolation
ladybugs (yasutomii and niponica)
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behavioral isolation ex
green lacewings
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mechanical barrier ex
- genital arch in males of drosophila
- baculum of walrus requires mechanically fitting species
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postzygotic barriers?
hybrid inviability and sterility
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biometrical characteristics
techniques that rely on measurable physical characteristics
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the new synthesis
not all traits are expressed, expressed in discrete units, though wide varieties
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allopatric
physical barrier
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peripatric
specie moves to island
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parapatric
pineapple and apple hence specie isolated based on food preference
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sympatric
blue dino wants to mate with red dino
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pup fish in death valley
example of allopatric
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what is an ecological niche
all elements that allow organism to survive
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what is the principle of competitive exclusion by G.F. Gause
two species occupying the same habitat can coexist only if they are not competing for the same resource
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vicariance
physical barrier
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dispersal
go to nearby island (birds and wind dispersed plants are better at it)
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deteriministic
according to dispersal abilities
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disharmony
ecosystems incomplete (not many species), susceptive to freak events
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example of sympatric
palm trees flower at different times as a result of volcano. even though they could interbred
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