It's the Immune system!
good luck
A variation is a reference to the differences or deviations, such as the structure and form, as for crossing over is the exchange of genetic material between the non-sister chromatids of the homologous chromosomes during meiosis.
First, ISA means Industry Standard Architecture. it is a standard bus architecture that is associated with the IBM AT motherboard. The Industry Standard Architecture has three key functions. first is it is informative, the second is it is directional and the last one is it is locational.