Answer:
By the process of cellular differentiation which consists of physical and functional changes of the cell used by processes at the genetic level. The expression of these in each type of cell is different. That is to say that the type of cell follows at a time of development there is differential activation of some genes and repression of others
An age-related change in the nervous system that can adversely affect nutritional status is decreased taste perception, hearing loss and vision loss. Aging refers to a multidimensional process in humans, the process of physical, and psychological, and social changes. As a population, older adults are more prone to age-related diseases, functional impairment, and physical inability that nay interfere with the maintenance of a good nutritional status.
A virus is a microscopic parasite that infects cells in biological organisms, they reproduce only by invading and controlling other cells as they lack the cellular machinery for self reproduction. Additionally, viruses contain at least one unique protein synthesized by specific genes in the nucleic acid, the proteins forms a shell called capsid around the nuclei acid.