1. Traits or features of an organism that originally evolved for one function but are now used for a different function; evolutionary repurposing of biological structures.
Usage: biology; evolutionary biology; plural form of exaptation

Examples

• Feathers are classic exaptations: they originally evolved for insulation but were later co-opted for flight.
• The swim bladder in fish represents one of evolution's most successful exaptations, having been repurposed from a lung-like structure.
• Scientists study exaptations to understand how organisms adapt existing structures to new environmental challenges.
• Bird wings are exaptations of forelimbs that originally served different purposes in ancestral species.
• The evolution of exaptations shows that natural selection can work with pre-existing biological material in creative ways.