In animals, a fertilized egg cell becomes a diploid zygote. This will then undergo cleavage resulting in an embryo with three germ layers. These layers are endoderm, mesoderm and ectoderm. From these layers, differentiation of these cells become recognizable body parts of the new embryo. In plants, a double fertilization occurs inside the ovule. One fertilization results in a diploid zygote, the other fertilization results in the union of two polar cells and a sperm forming a triploid tissue called endosperm. Both the zygote and endosperm become the seed. Plants, like animals have cleavage stages and at the eight cell stage, the embryo shows a clear pattern of tissues forming along a linear plane. Differentiation and growth occurs as the embryo develops.