Why do flowers have sepals?

Sepals - the sepals of a flower protect it while it is in bud. The flower is really a kind of shoot, in which the leaves have been altered so that they can take on the task of producing seeds. In a simple flower these leaves are arranged in circles, called whorls. The outermost are five green, leaf shaped sepals. Inside these are five petals, usually heart shaped, each with a small flap and its base where nectar is produced to attract bees and other insects. Both the sepals and the petals are attached at their bases to the "receptacle", the swollen end of the flower-stalk, which looks like a cone in the middle of the flower. Above the sepals and petals are the parts of the flower used in reproduction. These are the stamens, which contain the yellow pollen, and the carpels, which contain the ovules. Most flowers are built on this plan but there are wide variations in size, shape and colour, and in the numbers of the different parts of the flowers.