Fertilization - Development Biology

Previously you knew the process which leads to the differentiation of the male and female germ cells, the sperm and ova, respectively. In this section we shall describe the process by which the sperm and the egg unite to form a zygote. This process is known as fertilization. Fertilization results in

1. The restoration of the diploid chromosomal number in the nucleus, and
2. The activation of the development.

Activation would essentially mean that a sequence of metabolic and morphological changes are triggered that in turn cause the division of a unicellular zygote into a multicellular organism. Mostly we will describe the fertilization in mammals with occasional references to sea urchins. It is true that depending upon the habitat as well as the life styles there may be variations in the fertilization process in diverse organisms. But generally the events of fertilization are more or less similar in many different organisms. Prior to the actual fusion of the sperm and the egg nuclei, the germ cells prepare themselves for the fertilization process.