L11 Speciation Flashcards
What is speciation?
The origin of species - slitting into two.
What does the process of speciation lead to?
- Species
- Genera
- Families
- Orders
- Classes
- Phyla
What are the features of speciation?
- Biological species and reproductive isolation
- Gene flow and disruptive selection.
What are the two modes of speciation?
- Allopatrtic speciation
- Sympatric speciation
Define biological species.
a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring—but do not produce viable, fertile offspring with members of other such groups.
Define reproductive isolation.
the formation of a new species hinges on reproductive isolation—the existence of biological factors (barriers) that impede members of two species from inter- breeding and producing viable, fertile offspring.
What are the three types of selection?
- Stabilizing selection
- Directional selection
- Disruptive selection.
Define stabilizing selection.
the mean phenotype is favoured (extreme phenotypes are disfavoured
Define directional selection.
evolutionary change with a shift in the mean population phenotype.
Define disruptive selection.
two or more phenotypes are favoured, the mean phenotypes is selected against.
What is gene flow?
exchange of genes between populations as a result of movement and interbreeding of individuals
What are the two changes during speciation?
- Divergence – species adapt to different environments or selection pressures
- Reproductive isolation – populations cannot interbreed.
What are the two major hypotheses for the occurence of speciation?
- Focus on the interplay of gene flow & disruptive selection as drivers of reproductive isolation and phenotypic divergence.
- Major difference is in the order of isolation and divergence
What is allopatric speciation?
Geographic isolation & reproductive isolation first, then divergence.
What is sympatric speciation?
Divergence first, then reproductive isolation.
