Ans. Mensuration is the periodic physiologic discharge through the ****** of blood, cervical mucus, vaginal secretions, and endometrial tissue during the reproductive period, and in the absence of pregnancy, as controlled by hormones.Genetic drift is a mechanism of evolution in which allele frequencies of a population change over generations due to chance (sampling error).Natural Selection is the process whereby organisms better adapted to their environment tend to survive and produce more offspring. The theory of its action was first fully expounded by Charles Darwin, and it is now regarded as be the main process that brings about evolution.Speciation is the evolutionary process by which biological populations evolve to become distinct species.