Information About ™Eusociality |
| CATEGORIES ABOUT EUSOCIALITY | |
| ecology | |
| superorganisms | |
| SHOPPER'S DELIGHT | |
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Eusociality is the phenomenon of reproductive specialisation found in some animals. There are two causes of eusociality: Kin-selected Altruism and high Inbreeding . Its defining features are: # reproductive division of labor # overlap of generations # sterile castes (not always present) The most familiar examples are insects such as Ant s, Bee s, and Wasp s (the order Hymenoptera ), with reproductive queens and Sterile workers. Eusociality may be easier for these species to evolve due to their Haplodiploidy , which increases the significance of Kin Selection . Sisters are more related to each other than to their offspring. This mechanism of sex determination gives rise to what W. D. Hamilton first termed "supersisters" who share 75 per cent of their genes. Sterile workers are more closely related to their supersisters than to any offspring they might have, if they were to breed themselves. From the " Selfish Gene 's" point-of-view, it is advantageous to raise more sisters. Even though workers cannot reproduce, they are passing on more of their genes by caring for their sisters than they would by having their own offspring (which would only have 50% of their genes). This unusual situation where females have greater fitness when they are sterile has led to the independent evolution of eusociality occurring 11 separate times within the haplodiploid group Hymenoptera. However, Hymenoptera is a large group and the vast majority of Hymenopterans do not exhibit any social behavior. In spite of the obvious advantages of common '', Darwin called this altruistic behavior the "one special difficulty, which at first appeared to me insuperable, and actually fatal to my theory." Darwin anticipated that the resolution to the paradox would lie in the close family relationship, but the complete answer (kin selection or inclusive fitness) had to wait for the discovery of the mechanisms for genetic inheritance. Superorganism theory explains the evolutionary stability of eusociality by dictating that only reproductive individuals are counted as individuals and sterile individuals are simply independent parts of their reproductive parent. This theory makes sense only when the sterile caste is physically sterile and not simply being repressed. In this way the sterile caste provide for their reproductive parents so that their genes can spread through them. Another widespread insect group exhibiting eusociality is the is a clear case, and, less rigorously some Canid s can be argued to be eusocial, since only the Alpha Male and female will breed. In this case, the other members of the pack are not sterile, but are dissuaded from breeding by aggressive behavior on the part of the breeding pair. Eusociality has arisen among some Crustacean s and other Arthropod s. On some tropical reefs, several species of minute synalpheid Pistol Shrimp that depend on certain sponges for the survival of their colony, live eusocially, with a single breeding female and a preponderance of male defenders, armed with outsize snapping claws. Eusociality with biologically sterile individuals represents the most extreme form of Kin Altruism . The analysis of eusociality played a key role in the development of theories in Sociobiology . The idea of a human eusocial group was investigated in-depth in Stephen Baxter 's novel '' Coalescent ''. SEE ALSO EXTERNAL LINKS |