BIO152H5 Lecture Notes - Lecture 20: Species Problem, Allopatric Speciation, Continental Drift
Document Summary
Darwin was fascinated by speciation: the process by which species form, many shared characteristics due to ancestry. Example: dna of flightless and flying cormorants reveals close similarity. Microevolution: mechanisms: mutation, migration, genetic drift, and natural selection. Macroevolution: the origin of living organisms: mechanisms by which new species originate from existing ones. Speciation explains the similarities (unity) and differences (diversity) of life among species. Evolutionary independent group or population - differences in appearance. Reproductive isolation: barriers that prevent 2 species from interbreeding: gene flow is key point in defining the difference between the biological species concept. How are species defined and identified: biologists commonly use four approaches to identify species: Prezygotic; prevent zygote formation: prevent fertilization from occurring. Postzygotic; preventing the proper development and functioning of zygote, once formed: reduced development, reduced hybrid, reduced chance of survival to reproduction. Limitation of biological species concept: cannot evaluate gene flow of fossils, not useful concept for asexually reproducing organisms.
