We take it (1) FOR granted that when we put something in our mouths, we taste it. But why should our bodies be able to detect chemicals in this way? In order (2) TO answer that question, we need to consider two things: the dietary requirements (3) WHICH our bodies and the risks associate (4) WITH eating.
Our bodies need certain substances (5) ON a regular basis, including vitamins, carbohydrates and salt. The flavour of food, (6) SUCH as fruit, gives us important information
(8) ABOUT the nutrients it contains. Sweet tastes mean sugar, which (7) IN turn means high energy levels. Salty tastes indicate the presence of other chemicals we need besides sugar. Because we find these tastes pleasurable, we tend to eat food that (9) IS high in these substances.
Bitter and sour tastes, on the other hand, usually act (10) AS nature's warming devices. When something is poisonous, it usually has a bitter flavous, a taste (11) WHICH we naturally dislike. Also, as food (12) GOES off it tends to develop a sour taste. This means that we are able to avoid food that could cause health problems.