 There has also been some debate to what extent there is a strong parallel between model organisms and theoretical models in science, for example, the Lotka-Volterra predator-prey model in population ecology. A strong parallel is suggested by the fact that there is a widespread agreement in the literature on scientific modeling (see entry Models in Science) that scientific models need not be abstract (i.e., consist of mathematical equations or something of this sort); they can also be concrete and physical. Watson’s and Crick’s 1953 DNA model made of cardboard and wire qualifies as a model in this sense. Could a fruit fly bred in a laboratory to do genetic experiments also be considered as a scientific model in the standard sense? Ankeny and Leonelli (2011) answer this question in the affirmative, on the grounds that (1) model organisms are used to represent a whole range of other organisms and (2) that they are used to represent specific phenomena.