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Ch24 - Origin of Species, - Coggle Diagram
Ch24 - Origin of Species
Identification of species
molecular features
similarities to look for:
DNA sequences inside genes
gene order
chromosome structure
chromosome number
may be difficult to draw a line when separating species
ecological factors
factors related to a species habitat can be used to differentiate between one species and the other
can be unreliable because some bacterial strains (for example) exhibit similar optimum conditions when it comes to habitat
evolutionary relationships
reproductive isolation mechanism
pre-zygotic barriers
habitat isolation
geographic barrier prevents interbreeding
temporal isolation
reproduction at different times of the year
behavioral isolation
mate choice depends on behavior (e.g., song choice)
gametic isolation
gametes unable to unite successfully
mechanical isolation
size or compatibility of genitalia
post-zygotic barriers
hybrid inviability
zygote formed, cannot survive and progress
hybrid sterility
interspecies hybrid is viable but sterile and cannot reproduce
hybrid breakdown
viable & fertile but inherited genetic abnormalities
interspecies hybrid
when two different species produce offspring
morphological traits
physical characteristics
drawbacks
how many traits to consider?
some traits are continuously varied
what degree of dissimilarity to use?
members of the same species can look very different, whereas members of different species can look very similar
ability to interbreed
reproductive isolation prevents interbreeding of species
drawbacks
difficult to determine in nature
some organisms can interbreed but do not
does not apply to asexual or extinct species
speciation
what is it?
two types
mechanisms