This is an important term, so I list a number of definitions. They mean the same thing, so try to integrate all the definitions in your understanding: - Change of shape with increase or decrease in size (Gould, 1977). - The dependence of shape variables on size variables (Bookstein et al, 1985). - Growth of a feature during ontogeny at a rate different from that of another feature with which it is compared (Futuyma, 1986). - The relationship between the size of an organism and the size of any of its parts: for example there is an allometric relationship between brain size and body size such that animals with bigger bodies have bigger brains. - Allometric relationships can be studied during the growth of a single organism (ontogenetic allometry), between different organisms within a species (e.g. males and females), or between organisms in different species (phylogenetic, or interspecific allometry) (Ridley, 1993) The allometric equation is: y=bxa where x and y are two measurements taken on a number of specime