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Speciation (biological species concept (use reproductive…
Speciation
biological species concept
use
reproductive isolation=evolution independently
in-viable offspring (could not develop to adulthood)
produce sterile offspring
breed but fail to produce offspring
do not breed
in nature
(pre)
pre-zygotic isolation
--> prevent successful mating
less waste effort
post- zygotic isolation
--> prevents offspring from producing offspring of their own
selects for pre-zygotic isolation
disadvantage
do not apply for asexual species
not practical for extinct species
may be hard to evaluate
difficult to identify whether the geographic distance or reproductive isolation
Phylogeny species concept
monophyletic
A monophyletic group is a group defined by a single common ancestor
Phylogenetic species
smallest monophyletic group
Advantage
well defined
broadly applicable
Disadvantage
hard to estimate phylogeny
requires a lot of information
species split
genetic isolation
necessary
limit gene flow
genetic divergence
allopatry (different place )
dispersal
isolate small part of same population to a new area and colonize it
variance
Population is split by a geographical or ecological barrier
sympatry (same area)
Polyploid speciation
(common in plants)
autopolyploid (same species)
same species: chromosome doubling within on mate
allopolyploid (other-species )
hybridization+chromosome doubling
Reuniting
when population come back into secondary contact
Fusion
when two isolated populations come back into contact, they may go back together
difference may be small
difference may be overwhelmed by gene flow
Reinforcement
reinforce the distinctions between two species
have lower fitness
Morphological species concept
species are groups of organisms that look (sufficiently) different
Advantage
useful for working with fossil
takes a lots of experience and expertise
Disadvantage
subjective
Cryptic species--> two species look very similar
No clear
Ecological species concept
According to species' ecological niche
Advantage
applicant for asexual
Disadvantage
different species may have similar niches
Splitting of one evolving group of organisms into two separately evolving groups