Natural Selection and Species Origin

This lecture explores the concept of natural selection and the origin of species, discussing the biological definition of species based on reproductive compatibility, barriers to gene flow, and alternative species definitions such as morphological, ecological, and phylogenetic. It delves into the classification of species using DNA markers, traditional methods, and conceptual entities like taxa. The lecture also covers the process of speciation, comparing allopatric and sympatric speciation, and providing examples such as chromosomal evolution in island mice and experimental evidence of speciation in fruit flies. Additionally, it examines polyploidy as a mechanism for sympatric speciation and presents the case of wheat as an allohexaploid resulting from hybridization. The lecture concludes with a discussion on ongoing sympatric speciation in apple maggot flies.