Analogy (biology)
An analogy is a trait or an organ that appears similar in two unrelated organisms. The cladistic term for the same phenomenon is homoplasy, from Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 for same form. Biological anologies are often the result of convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...


Analogies in taxonomy

The classical example of an analogy is the ability to fly in birds and bats
A bat is a flying mammal in the Chiroptera order.Bats may also refer to:-Films:*Bats , starring Lou Diamond Phillips and Bob Gunton*Bats: Human Harvest -Groups:...

. Both groups can move by powered flight, but flight has evolved independently in the two groups. The ability to fly does not make birds and bats close relatives. The opposite of analogy is homology
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...

, where the ability or organ in question has been inherited from a common ancestor. The British
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 anatomist Richard Owen
Richard Owen
Sir Richard Owen, FRS KCB was an English biologist, comparative anatomist and palaeontologist.Owen is probably best remembered today for coining the word Dinosauria and for his outspoken opposition to Charles Darwin's theory of evolution by natural selection...

 was the first scientist to recognise the fundamental difference between analogies and homologies, and named them.

Similar problems - similar solutions

Analogous traits will often arise due to convergence, where different species live in similar ways and/or similar environment, and thus face the same environmental factors. Both herring
Herring is an oily fish of the genus Clupea, found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Three species of Clupea are recognized. The main taxa, the Atlantic herring and the Pacific herring may each be divided into subspecies...

s and dolphins are streamlined. Both are active predators in a high drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...

 environment, but the herring is a bony fish, the dolphin a mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

. In the Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...

, similarly streamlined ichthyosaur
Ichthyosaurs were giant marine reptiles that resembled fish and dolphins...

s navigated the worlds oceans, yet another example of a group evolving a similar shape due to the same environmental factors. A similar phenomenon is earless seal
Earless seal
The true seals or earless seals are one of the three main groups of mammals within the seal superfamily, Pinnipedia. All true seals are members of the family Phocidae . They are sometimes called crawling seals to distinguish them from the fur seals and sea lions of the family Otariidae...

s and eared seals. It was long debated whether the two groups are a single marine group, or represent two separate episodes of carnivora
The diverse order Carnivora |Latin]] carō "flesh", + vorāre "to devour") includes over 260 species of placental mammals. Its members are formally referred to as carnivorans, while the word "carnivore" can refer to any meat-eating animal...

ns turning to a marine environment.
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