BIOLOGY 3 Lecture Notes - Lecture 5: Genetic Divergence, Ensatina, Assortative Mating
Document Summary
Modes of speciation as classified by genetic and causal basis. Cytoplasmic incompatibility- results in sperm and eggs being unable to form viable offspring. The effect arises from changes in the gamete cells caused by intracellular parasites like wolbachia, which infect a wide range of insect species. Polyploidy (abrupt speciation)- result from whole genome duplication. Diploid becomes a tetraploid making gamete fusion impossible. Chromosomal rearrangement (abrupt speciation)- chromosome fusion or chromosome fission event. Recombinational speciation- hybridization between 2 species gives rise to a new lineage that is both fertile and true breeding, but is reproductively isolated from both parental species. Allopatric speciation- simplest and most common mechanism of speciation, evolution of reproductive barriers in populations that are prevented by a geographic barrier from exchanging genes. Ex: formation of the isthmus of panama separated once sympatric marine populations into caribbean and pacific populations which then proceeded on separate evolutionary trajectories, formation of mountain ranges, canyons, or rivers, continental drift.
