Nile is a major north-flowing river in north-east Africa. It is generally regarded as the longest river in the world, but some people give title to Amazon river, in South America. The Nile, which is 6,853 km long, is an "international" river as its water resources are shared by 11 countries, namely, Tanzania, Uganda, Rwanda, Burundi, Congo-Kinshasa, Kenya, Ethiopia, Eritrea, South Sudan, Sudan and Egypt. It is the primary water source of Egypt and Sudan. The Nile has two major tributaries, the White Nile and the Blue Nile. The White Nile is the primary source of the river, whereas the Blue Nile is the secondary source and also the source of most of the water and silt.
Because of the process of fertilization the sperm enters the ovum and formation of zygote happens inside the nucleous.