Hypermutation is the central aspect to making the Acquired immune system possible. Large creatures such as vertebrates typically have a long generation time, while (micro-)parasites (such as viruses, bacteria, fungi or worms) that they play host to often have a short generation time. Typical classes Petromyzontidae (lampreys) Placodermi - extinct Chondrichthyes (cartilaginous fish) Acanthodii - extinct Actinopterygii (ray-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) Amphibia (amphibians) Reptilia (reptiles) Aves (birds) Mammalia (mammals) Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... A parasite is an organism that lives in or on the living tissue of a host organism at the expense of it. ... A virus is a microscopic parasite that infects cells in biological organisms. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Divisions Chytridiomycota Zygomycota Ascomycota Basidiomycota The Fungi (singular: fungus) are a large group of organisms ranked as a kingdom within the Domain Eukaryota. ... Worm can refer to: The worm, a collection of animal phyla. ...

This means that the parasites will evolve much faster than their hosts, potentially overwhelming them if there's no rapid defence. To be able to deal with these attackers, some form of adaptation mechanism is needed.

Organisms with an acquired immune system will pick up invasions using the less efficient innate immune system , and small amounts of dead invader material will be presented to ... cells in the lymph nodes. In biology and ecology, an organism (in Greek organon = instrument) is a complex adaptive system of organs that influence each other in such a way that they function as a more or less stable whole and have properties of life. ... The immune system is the system of specialised cells and organs that protect an organism from outside biological influences. ... Lymph nodes are components of the lymphatic system. ...

These cells unlock a certain part of their DNA related to antibody (alpha-?)unit production, and proceed to rapidly divide, all the while mutating this section of DNA. While dividing, the lymph-cells will auto-select for antibody binding affinity to the invader fragments. Space-filling model of a section of DNA molecule Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and most viruses). ... Schematic of antibody binding to an antigen An antibody is a protein used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ... Cell division is the process by which a cell (called the parent cell) divides into two cells (called daughter cells). ...

This process takes 3 weeks, and speeds up that which would otherwise require centuries of evolution. The survivors of this selection process will continue to divide, and go on to produce T-cells, ...-cells, ... , and antibodies, which will now be capable of detecting and destroying the invader with exceptional efficiency. T cells are a subset of lymphocytes that play a large role in the immune response. ...

Also a small number will be distributed to lymph nodes throughout the body as memory-cells. If the same invader ever invades again, the memory cells will rapidly divide, and confer the same defensive capability to the body again. The organism is now immune. A request has been made on Wikipedia for this article to be deleted in accordance with the deletion policy. ...

Some worm species avoid the acquired immune response by modifying their external skin or secretions every couple of weeks.

The hypermutation process also has cells auto-select against the organism's own cells: their 'signature'. Failure to auto-select against the own signature causes an auto-immune response, which is often dangerous to the organism itself. Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body. ...

See also

• Immune system
• Evolution