Memorial Union S110
The Evolution and Social Science Colloquium Series presents Prof. R. Michael Roberts, MU Department of Biochemistry, "The Evolution of the Human Placenta: Not Quite Up There with the Sheep or the Horse," Monday, Dec. 3, Memorial Union S110.
A still apt definition of a placenta is that it is an organ resulting from the apposition or fusion of the fetal membranes to the uterine mucosa, thereby allowing viviparity and exchange of solutes, gases and other molecules, e.g. hormones, between the maternal system and the developing offspring. By this definition, placentas have evolved within every vertebrate class other than birds. They have also emerged on multiple occasions, often within quite narrow taxonomic groups and over short periods of evolutionary time. As the placenta and the maternal system have evolved to associate more intimately, as in mammals, such that the conceptus comes to rely extensively on maternal support, the relationship leads to increased genetic conflict that drives adaptive changes on both sides. The story of vertebrate placentation, therefore, is one of convergent evolution at both the macro- and molecular levels. In this talk, I shall first describe the emergence of placental-like structures in non-mammalian vertebrates. I shall then attempt to explain the diversification of placentation encountered in mammals where, among extant species, a bewildering range of structures is encountered. I’ll emphasize the success of non-invasive placental types as encountered in horses, pigs, and domestic ruminant species in providing young born in a relatively mature and independent state. I close the review by discussing mechanisms that might have favored diversity and hence evolution of the morphology and physiology of the placentas of eutherian mammals.
For more information on the ESS series, visit this website: http://ess.missouri.edu/