ICSE Class 10 Answered

Blood groups are of different typres based on the antigen present on the red blood cells. However, science has yet to explain why some groups of people are more likely to have one blood type over another and how different people have different blood groups.

Blood group A is thought to be the most ancient. Pre-humans began with type A blood before early humanoids began to exhibit certain mutations in the form of other blood types.

Similarlly, the presence of antigen over the RBC surface is a result of evolutionary changes that have happended in the past. The occurrence of one type most dominantly over the other is still an area of research. Primarily, there are two main antigens that form around our red blood cells, they are known as A and B. If the blood group is AB, then you have both the A and B antigens. Group O lacks the A and B antigens, so the antibodies of a group O patient would attack A or B blood from a transfusion.