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Ileum, caecum and colon of rabbit, showing Appendix vermiformis on fully functional caecum The human vermiform appendix on the vestigial caecum. The appendix was once believed to be a vestige of a redundant organ that in ancestral species had digestive functions, much as it still does in extant species in which intestinal flora hydrolyze cellulose and similar indigestible plant materials. [10]
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]
Palm trees form are in unrelated plants: cycads (from the Jurassic period) and older tree ferns. [231] Flower petals came about independently in a number of different plant lineages. [232] Bilateral flowers, with distinct up-down orientation, came about independently in a number of different plants like: violets, orchids and peas. [233] [234]
Atavism can also be seen in humans who possess large teeth, like those of other primates. [9] In addition, a case of "snake heart", the presence of "coronary circulation and myocardial architecture [that closely] resemble those of the reptilian heart", has also been reported in medical literature. [ 10 ]
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.
Human evolution (origins of society and culture) – Transition of human species to anthropologically modern behavior Inversion (evolutionary biology) – Hypothesis in developmental biology Mosaic evolution – Evolution of characters at various rates both within and between species
Birds have only one functional ovary (the left), while the other remains vestigial. In mammals including humans, the female ovary is homologous to the male testicle, in that they are both gonads and endocrine glands. Ovaries of some kind are found in the female reproductive system of many invertebrates that employ sexual reproduction. However ...
Likewise, there is no evidence for any accessory olfactory bulb in adult human beings, [48] and the key genes involved in VNO function in other mammals have pseudogenized in human beings. Therefore, while many debate the structure's presence in adult human beings, a review of the scientific literature by Tristram Wyatt concluded that on current ...