Question

Life history theory examines trade-offs between the components of fitness. Birth weight is one life history trait that can be influenced by these trade-offs. Describe in detail one trade-off that has implications for variation in human birth weight.

Answer 1

Birth weight is one life history trait that is influenced by the trade off. Nutrional investment during fetal life is one of the trade off that has implication for variation in human birth weight. Nutrition is the key mechanism through which mothers would invest energy in babies. The fetal life is a critical period for the structural and functional development of different organs and for epigenetic development. Most of the cell divion occurs during this time.So this nutrional investment is very essential for the baby. The one reason for birth weight of the baby varies is that if the mother give more nutrition, the baby will gain more weight. Maternal basal metabolism is considered as the key element of the magnitude of the growth attanible by the fetus. Carbohydrate accounts for about 80% of fetal fuel consumption and by the consumption, the weight gained is more and the remainder coming from substrates such as amino acids and free fatty acids. As the pregnancy progress the energy needed is more. The maternal metabolism reaches an inherent limit where the glucose needed by the fetal brain is more and the mother is unable to supply it. So it is the point where the delivery occures. Therefore it is proposed that human birth occur at the time where fetal energy requiremets exceeds the capacity of maternal metabolism to meet that requirements through placental nutrition.