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The opposite of homologous organs are analogous organs which do similar jobs in two taxa that were not present in their most recent common ancestor but rather evolved separately. For example, the wings of insects and birds evolved independently in widely separated groups, and converged functionally to support powered flight, so they are analogous.
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 ...
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 ...
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.
In arthropods, an appendage refers to any of the homologous body parts that may extend from a body segment, including antennae, mouthparts (including mandibles, maxillae and maxillipeds), gills, locomotor legs (pereiopods for walking, and pleopods for swimming), sexual organs , and parts of the tail . Typically, each body segment carries one ...
These organs connect the mother and the fetus. Placentas are a defining characteristic of placental mammals, but are also found in marsupials and some non-mammals with varying levels of development. [6] The homology of such structures in various viviparous organisms is debatable, and in invertebrates such as Arthropoda, is analogous at best.
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]
Reproductive organs are found within the cloaca of reptiles. Most male reptiles have copulatory organs, which are usually retracted or inverted and stored inside the body. In turtles and crocodilians, the male has a single median penis-like organ, while male snakes and lizards each possess a pair of penis-like organs.