BIO152H5 Lecture Notes - Lecture 19: Species Problem, Gene Flow, Mass Production

118 views8 pages
29 Dec 2015

Document Summary

Speciation: formation of new species (process by which one species splits into 2 or more species) Many shared characteristics due to shared ancestry. E. g) dna of flightless and flying cormorants reveals close relatedness. Microevolution: changes in allele frequencies in a population over time: mechanisms: mutation, gene flow, genetic drift, natural selection, origin of new groups of organisms, mechanisms by which new species originate from existing ones. Speciation explains unity and diversity of life. Gene flow: reproductive isolation: barriers that prevent 2 species from interbreeding. Prezygotic: prevent zygote formation, block fertilization form occurring. Occur before zygote forms: habitat, temporal (time of breeding) Postzygotic: preventing proper development and functioning of zygote once formed: reduced survival, reduced hybrid fertility sterile organisms (horse and donkey; production of mule); a lot of examples with domestic animals. Hybrid breeding usually occurs in captivity: decreased chance of survival to reproduction, limitations to biological species concept: Not useful concept for asexually reproducing organisms.