Water & Nutrients. Like humans and animals, plants need both water and nutrients (food) to survive. Most all plants use water to carry moisture and nutrients back and forth between the roots and leaves. Water, as well as nutrients, is normally taken up through the roots from the soil.
Changing from puppy food to adult food depends on the size of your dog as an adult. If he is a small breed and will not exceed 30 pounds, he is mature at 10 to 12 months old. Some small breeds are mature before 10 months of age. Medium breeds are dogs that do not exceed 80 pounds at full growth.
1 Some formulas estimate that a puppy's adult weight will roughly be double of their weight at 14 weeks of age.  Teething - Puppies 12 weeks old will have most of their 28 baby teeth and may have their first 2 to 4 adult front teeth, called the incisors. Over the next three months, your puppy will be getting in all of his adult teeth. Because they are entering an active teething stage, they will want to chew.