Final answer:
Not all species have IgD antibodies as these are specific to certain mammals, such as humans, and are involved in B cell antigen recognition and maturation processes. IgD levels in serum are usually low, and the presence of such antibodies vary among different species due to genetic and evolutionary differences.
Step-by-step explanation:
Not all species have IgD antibodies; they are primarily found in certain mammals, including humans. IgD is one of the five classes of antibodies present in humans, which also include IgM, IgG, IgA, and IgE. Specifically, IgD is a membrane-bound monomer that is found on the surface of naive B cells and is associated with the antigen recognition process. These B cell receptors (BCRs) of the IgD class play an important role in the maturation of B cells into plasma cells. However, IgD is not typically secreted by B cells into the bloodstream, and only trace amounts are found in serum, likely from the degradation of B cells. Since antibody diversity and immunoglobulin classes are influenced by genetic factors and evolutionary processes, different species have developed distinct sets of antibodies, and not all animals have IgD.