Because that is what the babies inside the egg eat as they are forming
Usually there is only one egg yolk in an egg. But there have been nine found in one egg.
Well frog eggs are clear with black yolks. They come in hundreds though!
The yolk is basically the food supply for a developing chick, and the white is the protective membrane and cushion to protect the chick. As the chick grows in the egg, the yolk gets used up, and the...
Yolk is the yellow nucleus in the middle of the egg.