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Natural Selection (In nature there are a variety of selection pressures…
Natural Selection
In nature there are a variety of selection pressures
Maybe different in different places
Which may change over time
These influence the gene pool by favouring the fit phenotype
and not favouring the unfit
Darwin named this Survival of the fittest
So allele frequencies and genotypes gradually change
Evolution/speciation
Speciation can occur/sometimes it doesn't
Selection pressures don't change
There must be a way that 2 or more species populations become reproductively isolated
RIM's - Mechanism that stop/prevent interbreeding
Geographic isolation
Behaviours/songs, displays, ritual, calls
Temporal breeding time is different, nocturnal/diurnal
Hybrid inviability
Hybrid death
Hybrid is born but dies very young
These are pre-zygotic RIM's
Structure (sexual apparatus)
This is a post-zygotic RIM
Selective
Stabilising
Disruptive
Directional (most common)