Final answer:
The precipitin test is the standard method for determining if blood is human or animal by observing the reaction between human-specific antibodies and the blood sample. Blood types, classified by the ABO system, are determined through agglutination reactions between blood antigens and corresponding antibodies.
Step-by-step explanation:
The standard test used to determine whether blood is of human or animal origin is the precipitin test. This test is based on the principle that the serum of an animal that has been immunized with human blood will contain antibodies specific to human proteins. When human blood is introduced to this serum, the antibodies bind to the human proteins and form a precipitate, indicating the blood is of human origin. In forensic sciences, such tests are used to identify whether bloodstains are from a human or an animal.
Blood types are determined based on the presence or absence of specific antigens on the surface of red blood cells. The most common blood type classification system is the ABO system, which categorizes blood into four types: A, B, AB, and O. The presence of anti-A or anti-B antibodies will cause agglutination when mixed with the corresponding antigen, helping to determine the blood type of the sample.