Vestigial structures are anatomical features that have become reduced in size or function over evolutionary time, often due to a change in the organism's environment or lifestyle.
Here's a breakdown:
* Reduced size or function: These structures are remnants of a structure that was larger or more functional in an ancestor.
* Evolutionary change: They are not useless, but they are not as essential as they once were, suggesting they lost their original function due to environmental changes.
* Example: The appendix in humans is thought to be a vestigial structure, once used to digest plant material, but now serves no real purpose.
Key points to remember:
* Vestigial structures provide evidence for evolution because they show how organisms change over time.
* They are not necessarily useless, they may have secondary functions, but their original function is reduced.
* Examples include the tailbone in humans, wings on flightless birds, and pelvic bones in whales.