Gravity would have a lot to do with it. the Mediteranean sea is a lot lower then the mountains in the south where the water comes from.
As with all rivers - Gravity.
Northward
The White Nile begins in rainforests at the edge of the savannah and goes northward through sahel and desert to meet with the Blue Nile. The Blue Nile starts in the Ethiopian Hill-Country before going northwest into desert where it meets with the Blue Nile. The two rivers join to create the Nile River, which continues uninterruptedly northward through desert.
It flows in Egypt. it flows northward though the eastern Sahara.
The River Nile is in Africa. It originates in Burundi, south of the equator, and flows northward through northeastern Africa, eventually flowing through Egypt and finally draining into the Mediterranean Sea.
warm-water currents
warm-water currents
River Nile
The Nile river flows from south to north and no it is not the only river that goes northward. Other rivers that flow northward include the Red River (North Dakota), the Lena River (Russia), and the Shennandoah River (Virginia). +++ Most of the major Russian rivers flow North, because the Siberian Plain tilts very gently down to the North, and is fringed by mountains all along its Southern side.
Apart from fish and amphibians, sediment.
The river Nile flow into Mediterranean sea
No. The Nile flows northward. Note: This question makes an implicit assumption which is partially incorrect. There are other rivers that flow from south to north in the World, but not any others of repute in Africa.