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Vestigiality. In humans, the vermiform appendix is sometimes called a vestigial structure as it has lost much of its ancestral digestive function. Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. [1]
Human vestigiality. The muscles connected to the ears of a human do not develop enough to have the same mobility allowed to monkeys. Arrows show the vestigial structure called Darwin's tubercle. In the context of human evolution, vestigiality involves those traits occurring in humans that have lost all or most of their original function through ...
Evidence for common descent comes from the existence of vestigial structures. [72] These rudimentary structures are often homologous to structures that correspond in related or ancestral species. A wide range of structures exist such as mutated and non-functioning genes, parts of a flower, muscles, organs, and even behaviors.
This phenomenon is an automatic-response mechanism that activates even before a human becomes consciously aware that a startling, unexpected or unknown sound has been "heard". [2] That this vestigial response occurs even before becoming consciously aware of a startling noise would explain why the function of ear-perking had evolved in animals.
Double dewclaws on rear leg of dog. A dewclaw is a digit – vestigial in some animals – on the foot of many mammals, birds, and reptiles (including some extinct orders, like certain theropods). It commonly grows higher on the leg than the rest of the foot, such that in digitigrade or unguligrade species, it does not make contact with the ...
Analogous structures - structures similar in different organisms because, in convergent evolution, they evolved in a similar environment, rather than were inherited from a recent common ancestor. They usually serve the same or similar purposes. An example is the streamlined torpedo body shape of porpoises and sharks. So even though they evolved ...
Atavism. Reappearance of a genetic trait once thought extinct. Early embryos of various species display some ancestral features, like the tail on this human embryo. These features normally disappear in later development, but it may not happen if the animal has an atavism. [1][2] In biology, an atavism is a modification of a biological structure ...
Pelvic spur. Pelvic spurs (also known as vestigial legs) are external protrusions found around the cloaca in certain superfamilies of snakes belonging to the greater infraorder Alethinophidia. [1] These spurs are made up of the remnants of the femur bone, which is then covered by a corneal spur, or claw-like structure. [1]