Final answer:
Water comprises approximately 75 percent of a newborn's body weight, which is higher compared to about 50-60 percent in adults. The percentage decreases with age as the body composition changes.
Step-by-step explanation:
Water constitutes a significant portion of a newborn animal's body weight. In humans, infants typically have a higher percentage than adults. For newborns, water makes up about 75 percent of their body mass. This high percentage is primarily because newborns have a larger proportion of their body composed of organs like the brain and kidneys, which comprise 80-85 percent water.
As they grow, the proportion of body water decreases and stabilizes to around 50-60 percent in adults. The distribution of water is crucial for various body functions, being a major component of both intracellular and extracellular fluids.