 Most of the properties that developmental biologists attempt to explain are structural rather than functional. For example, a developmental biologist concentrates more on how tissue layers fold or how shape is generated than on what the folded tissue layers do or how the shape functions. The ontogeny of function, at all levels of organization, is an element of developmental biology, but it is often bracketed because of the predominance (both past and present) of questions surrounding the ontogeny of form or structure (Love 2008).