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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 ...
The smelling organs of the terrestrial coconut crab are similar to those of insects. [ 141 ] In an odd cross-phyla example, an insect, the hummingbird hawk-moth ( Macroglossum stellatarum ), also feeds by hovering in front of flowers and drinking their nectar in the same way as hummingbirds and sunbirds .
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.
Homoplasy can arise from both similar selection pressures acting on adapting species, and the effects of genetic drift. [2] [3] Homoplasy is the similarity in a feature that is not parsimoniously explained by descent from a common ancestor. Most often, homoplasy is viewed as a similarity in morphological characters.
The development and spread of antibiotic resistant bacteria provides evidence that evolution due to natural selection is an ongoing process in the natural world. Natural selection is ubiquitous in all research pertaining to evolution, taking note of the fact that all of the following examples in each section of the article document the process.
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]
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]
The spur may arise from various parts of the flower: the sepals, petals, or hypanthium, and often contain tissues that secrete nectar (nectaries). [ 1 ] [ 2 ] Nectar spurs are present in many clades across the angiosperms , and are often cited as an example of convergent evolution .