BIOL 1001 Lecture Notes - Lecture 5: Genetic Drift, Homeobox, Allometry
15 Aug 2018
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Two di erent ways (models) in which new species could be created: anagenesis. An existing species (the parent species) becomes a new species (the daughter species) Parent species no longer exists (pseudoextinction): cladogenesis. Parent species gives rise to a daughter species as a separate branching population. Parent and daughter species continue to coexist afterwards. Recall, all life is descended from one ancestor (universal genetic code). Only cladogenesis can increase the total number of species. Anagenesis may occur sometimes but only cladogenesis can account for the present day diversity of life on earth. A species is a group of individuals with the potential to interbreed in their natural environment. Interbreeding between populations of a species (=gene ow, the exchange of alleles) maintains their similarities. Gene ow does not occur between populations of di erent spices because of isolation mechanisms that act as interbreeding barriers. Act before fertilization (prevent zygote from being born).
