![]() Adaptations, therefore, need not be adaptive, as long as they were at some point. ![]() Vestigial traits can still be considered adaptations because an adaptation is often defined as a trait that has been favored by natural selection. We highlighted a mechanism whereby the daughter vesicles acted as osmotically active solutes (osmoticants), contributing an extra vestigial osmotic pressure. Vestigial structures are often called vestigial organs, although many of them are not actually organs. ![]() We contend that these and all other alleged. Homologous structures indicate common ancestry with those organisms that have a functional version of the structure. The so-called vestigial organs, or remnants, selected for this video are structures and reflexes that are easily visible: a tendon in the forearm, seemingly useless muscles attached to your ears, goose bumps, the tailbone you may have bumped in a fall, and a tiny baby’s strong grasp. The vestigial versions of a structure can be compared to the original version of the structure in other species in order to determine the homology of the structure. Some vestigial structures persist due to limitations in development, such that complete loss of the structure could not occur without major alterations of the organism’s developmental pattern, and such alterations would likely produce numerous negative side-effects. This provides some selective pressure for the removal of parts that do not contribute to an organism’s fitness, but a structure that is not directly harmful will take longer to be ‘phased out’ than one that is. If there are no selection pressures actively lowering the fitness of the individual, the trait will persist in future generations unless the trait is eliminated through genetic drift or other random events.Īlthough in many cases the vestigial structure is of no direct harm, all structures require extra energy in terms of development, maintenance, and weight and are also a risk in terms of disease (e.g., infection, cancer). Another type of evidence for evolution is the presence of structures in organisms that share the same basic form. In the Mammalia, vestigial skeletal structures abound but have not previously been the focus of study, with a few exceptions (e.g., whale pelves). Letter c in the picture indicates the undeveloped hind legs of a baleen whale. ![]() \): Whale Skeleton: The pelvic bones in whales are also a good example of vestigial evolution (whales evolved from four-legged land mammals and secondarily lost their hind legs).
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