Types of developmental change

Developmental changes have likely been involved in important morphological changes — like the evolution of novel and complex structures.

Here are a few of the sorts of developmental changes that may have been important:

• Module duplication and adaptation
  A module refers to a unit that can be duplicated and further adapted. For example, arthropods have various numbers of body segments. Segment duplication and loss is a developmental change that probably occurred many times in the evolution of this clade. The graphic below shows a hypothetical example of module duplication and adaptation.

• Individualization
  This is the modification of a particular module, usually when there is selection for a specialized function.

  One set of scorpions' appendages has evolved into pincers whereas the same appendage in many spiders has evolved into colorful pompoms used in mating rituals.