Different components of blood can be separated by their densities in a centrifuge. this is because blood is:

This is because blood is a SUSPENSION. Blood is composed of different type of particles with different densities. Blood is made up of platelets, white blood cells, red blood cells and the plasma. Blood is an heterogeneous mixture, which mean that all the components of the blood can be separated from one another. A suspension is a mixture which separate out when left standing; blood can be described as a suspension. 

It helps to preserve biodiversity.