Egg yolks are the yellow, round part of an egg that is surrounded by the egg white. They are rich in nutrients and contain various substances that are essential for the development and growth of an embryo.

Stored Food:
One of the main components of an egg yolk is stored food. The yolk serves as a source of nutrients for the developing embryo. It contains proteins, fats, and vitamins that are necessary for the growth and development of the chick. This stored food provides energy and essential building blocks for the embryo to develop into a fully formed chick.

Proteins:
Egg yolks also contain proteins, which are important for the growth and repair of cells. These proteins are composed of amino acids, which are the building blocks of proteins. The presence of proteins in the egg yolk ensures that the developing embryo has the necessary materials for the formation of new tissues and organs.

Fats:
Egg yolks are high in fat content, particularly in the form of cholesterol. While cholesterol has often been associated with negative health effects in humans, it is actually a crucial component for the development of the embryo. Cholesterol is required for the formation of cell membranes and the production of various hormones.

Vitamins and Minerals:
Egg yolks also contain a variety of vitamins and minerals that are essential for the growth and development of the embryo. These include vitamins A, D, E, and K, as well as minerals like iron and phosphorus. These nutrients play vital roles in the development of bones, muscles, and other tissues.

Water:
While egg yolks do contain some water, it is not the main component. The water content in egg yolks is relatively low compared to the egg white. The egg white, or albumen, is primarily composed of water and proteins, while the yolk is richer in fats, proteins, and other nutrients.

In conclusion, egg yolks contain stored food, proteins, fats, vitamins, and minerals that are essential for the development and growth of an embryo. These nutrients provide the necessary energy and building blocks for the formation of new tissues and organs.

The egg yolk contains nutrients for the unhatched chick, or the embryo. Without nutrition, the egg will not hatch and may not even begin to develop. An egg yolk does not need water, soil or sunlight for developement. Hence, the answer is stored food.