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The three small bones in the middle ear of mammals including humans, the malleus, incus, and stapes, are today used to transmit sound from the eardrum to the inner ear. The malleus and incus develop in the embryo from structures that form jaw bones (the quadrate and the articular) in lizards, and in fossils of lizard-like ancestors of mammals.
They may or may not perform the same function. An example is the forelimb structure shared by cats and whales. 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 ...
Homologous structures in the external genitalia. This list of related male and female reproductive organs shows how the male and female reproductive organs and the development of the reproductive system are related, sharing a common developmental path. This makes them biological homologues. These organs differentiate into the respective sex ...
The statocyst is a balance sensory receptor independently found in different organisms like: some aquatic invertebrates, including bivalves, [206] cnidarians, [207] echinoderms, [208] cephalopods, [209] and crustaceans. [210] Also found in single-cell ciliate. A similar structure is also found in Xenoturbella. [211]
Human vestigial structures also include leftover embryological remnants that once served a function during development, such as the belly button, and analogous structures between biological sexes. For example, men are also born with two nipples, which are not known to serve a function compared to women. [47]
Functionally similar features that have arisen through convergent evolution are analogous, whereas homologous structures or traits have a common origin but can have dissimilar functions. Bird, bat, and pterosaur wings are analogous structures, but their forelimbs are homologous, sharing an ancestral state despite serving different functions.
Skeletons of a human and an elephant. Comparative foot morphology involves comparing the form of distal limb structures of a variety of terrestrial vertebrates.Understanding the role that the foot plays for each type of organism must take account of the differences in body type, foot shape, arrangement of structures, loading conditions and other variables.
Two organisms that are very closely related are likely to display very similar DNA sequences between two orthologs. Conversely, an organism that is further removed evolutionarily from another organism is likely to display a greater divergence in the sequence of the orthologs being studied. [citation needed]