01:119:115 Lecture Notes - Lecture 21: Dendrobium, Species, Reproductive Isolation
Document Summary
November 11, 2014: introduction, speciation, the process by which one species (sp) splits into two or more species (spp, tremendous diversity of life ancestor. Mechanisms which prevent fertilization from taking place: habitat isolation if you don"t live in the same area, you won"t mate, temporal isolation species undergo breeding at different times. Live in same rainforest, but they do not cross pollinate. Different pollinators goes to different flowers: gametic isolation, molecular or chemical differences between the species (spp) Egg and sperm are incompatible prevents fertilization. Sperm unable to survive in female reproductive tract (can"t fertilize: post- zygotic barriers, reduced hybrid viability genetic incompatibility, reduced hybrid fertility hybrid is produced. Hybrid is either sterile or have decreased fertility ex: mule [offspring of female horse (2n=64) and male donkey (2n=62)] 1st generation of hybrid are viable and fertile. Hybrids are able to mate with other hybrids or with the parent species: hybrid breakdown. = resulting offspring are not viable and not fertile.