63-404: (unranked) Hedylopsacea (unranked) Microhedylacea Acochlidiomorpha Acochlidiida Acochlidea Acochlidia Acochlidiacea , common name acochlidians , are a taxonomic clade of very unusual sea snails and sea and freshwater slugs , aquatic gastropod mollusks within the large clade Heterobranchia . Acochlidia is a variant spelling. These are mostly very small animals, without
126-444: A Brownian motion model of trait evolution along a phylogeny. More recent methods also quantify the strength of convergence. One drawback to keep in mind is that these methods can confuse long-term stasis with convergence due to phenotypic similarities. Stasis occurs when there is little evolutionary change among taxa. Distance-based measures assess the degree of similarity between lineages over time. Frequency-based measures assess
189-428: A nucleophile . In order to activate that nucleophile, they orient an acidic and a basic residue in a catalytic triad . The chemical and physical constraints on enzyme catalysis have caused identical triad arrangements to evolve independently more than 20 times in different enzyme superfamilies . Threonine proteases use the amino acid threonine as their catalytic nucleophile . Unlike cysteine and serine, threonine
252-676: A shell or gills , distinguished by the visceral mass being sharply set off from the rest of the body. Being a small group with only 47 species worldwide known in 2023, this group has been the subject of active research since 2010, by which date only 32 species were named. These slugs are morphologically and biologically highly aberrant and diverse, comprising a series of unusual characters (e.g. secondary gonochorism , lack of copulatory organs, asymmetric radulae ). Most acochlidians live interstitially in marine sands, while some have conquered limnic systems (uniquely within opisthobranch gastropods). Nils Hjalmar Odhner established this taxon as
315-671: A shell or gills , distinguished by the visceral mass being sharply set off from the rest of the body. Being a small group with only 47 species worldwide known in 2023, this group has been the subject of active research since 2010, by which date only 32 species were named. These slugs are morphologically and biologically highly aberrant and diverse, comprising a series of unusual characters (e.g. secondary gonochorism , lack of copulatory organs, asymmetric radulae ). Most acochlidians live interstitially in marine sands, while some have conquered limnic systems (uniquely within opisthobranch gastropods). Nils Hjalmar Odhner established this taxon as
378-546: A clade with Pyramidelloidea , Amphiboloidea and Eupulmonata . However, only three derived acochlids were included into analysis prior to 2010, with partially missing data. The taxonomy of Bouchet & Rocroi (2005) tentatively follows Starobogatov (1983), but they have downgraded his taxonomic ranks (suborders to superfamilies, superfamilies to families). The group Acochlidiacea is arranged as follows: A first comprehensive cladistic analysis of their phylogeny has been established by Schrödl & Neusser (2010), but
441-539: A clade with Pyramidelloidea , Amphiboloidea and Eupulmonata . However, only three derived acochlids were included into analysis prior to 2010, with partially missing data. The taxonomy of Bouchet & Rocroi (2005) tentatively follows Starobogatov (1983), but they have downgraded his taxonomic ranks (suborders to superfamilies, superfamilies to families). The group Acochlidiacea is arranged as follows: A first comprehensive cladistic analysis of their phylogeny has been established by Schrödl & Neusser (2010), but
504-423: A comprehensive parsimony analysis of morphological characters. During the last years a series of studies have redescribed key acochlidian taxa in great detail, including 3D reconstructions , and added considerably to the morphological and biological knowledge of this previously little understood group. Most recent morphological analyses suggested a common origin with either the equally enigmatic Rhodopemorpha ,
567-421: A comprehensive parsimony analysis of morphological characters. During the last years a series of studies have redescribed key acochlidian taxa in great detail, including 3D reconstructions , and added considerably to the morphological and biological knowledge of this previously little understood group. Most recent morphological analyses suggested a common origin with either the equally enigmatic Rhodopemorpha ,
630-866: A family in 1937, when he created the families Microhedylidae and Acochlidiidae . In 1939, he treated this taxon as an order. Rankin (1979) treated this taxon as an order, the order Acochlidioidea. Salvini-Plawen (1983) wrote this taxon as Acochlidiomorpha. Anderson (1992) treated this taxon as the order Acochlidiida. Burn in Beesley et al. (1998), wrote this taxon as the order Acochlidea. Wawra (1987) and various authors (2007–2010) spelled this taxon as Acochlidia. Three families ( Hedylopsidae , Microhedylidae and Acochlidiidae ) are classically recognized. Two controversial classifications (Rankin 1979, Starobogatov 1983) have been proposed recently, but they have not been evaluated since. An alternative classification by Burn (in Beesley et al., 1998) for
693-792: A family in 1937, when he created the families Microhedylidae and Acochlidiidae . In 1939, he treated this taxon as an order. Rankin (1979) treated this taxon as an order, the order Acochlidioidea. Salvini-Plawen (1983) wrote this taxon as Acochlidiomorpha. Anderson (1992) treated this taxon as the order Acochlidiida. Burn in Beesley et al. (1998), wrote this taxon as the order Acochlidea. Wawra (1987) and various authors (2007–2010) spelled this taxon as Acochlidia. Three families ( Hedylopsidae , Microhedylidae and Acochlidiidae ) are classically recognized. Two controversial classifications (Rankin 1979, Starobogatov 1983) have been proposed recently, but they have not been evaluated since. An alternative classification by Burn (in Beesley et al., 1998) for
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#1733084625270756-575: A high concentration of cerebrosides in the skin of their wings. This improves skin flexibility, a trait useful for flying animals; other mammals have a far lower concentration. The extinct pterosaurs independently evolved wings from their fore- and hindlimbs, while insects have wings that evolved separately from different organs. Flying squirrels and sugar gliders are much alike in their mammalian body plans, with gliding wings stretched between their limbs, but flying squirrels are placentals while sugar gliders are marsupials, widely separated within
819-635: A molecular level to toxins. One well-characterized example is the evolution of resistance to cardiotonic steroids (CTSs) via amino acid substitutions at well-defined positions of the α-subunit of Na ,K -ATPase (ATPalpha). Variation in ATPalpha has been surveyed in various CTS-adapted species spanning six insect orders. Among 21 CTS-adapted species, 58 (76%) of 76 amino acid substitutions at sites implicated in CTS resistance occur in parallel in at least two lineages. 30 of these substitutions (40%) occur at just two sites in
882-568: A phylogenetic reconstruction, and are sometimes explicitly sought by investigators. The methods applied to infer convergent evolution depend on whether pattern-based or process-based convergence is expected. Pattern-based convergence is the broader term, for when two or more lineages independently evolve patterns of similar traits. Process-based convergence is when the convergence is due to similar forces of natural selection . Earlier methods for measuring convergence incorporate ratios of phenotypic and phylogenetic distance by simulating evolution with
945-501: A steadily decreasing probability of retaining potential functionality over time. The time scale of this process varies greatly in different phylogenies; in mammals and birds, there is a reasonable probability of remaining in the genome in a potentially functional state for around 6 million years. When two species are similar in a particular character, evolution is defined as parallel if the ancestors were also similar, and convergent if they were not. Some scientists have argued that there
1008-827: A tendency toward reduction of complexity in major organ systems. (unranked) Microhedylacea has no superfamilies defined: A multi-locus molecular study by Jörger et al. (2010), included six out of seven acochlidian families. It confirmed Acochlidiacea in a pulmonate relationship, as sister to Eupulmonata. Euthyneura, Opisthobranchia and Pulmonata as traditionally defined were found non-monophyletic. The enigmatic amphibious and insectivorous Aitengidae clusters within Acochlidiacea, as sister to meiofaunal and brackish Pseudunelidae and limnic Acochlidiidae. Inclusion of this small acochlidian group resulted in redefinition of major groups within Heterobranchia , that has led to creation of
1071-708: A tendency toward reduction of complexity in major organ systems. (unranked) Microhedylacea has no superfamilies defined: A multi-locus molecular study by Jörger et al. (2010), included six out of seven acochlidian families. It confirmed Acochlidiacea in a pulmonate relationship, as sister to Eupulmonata. Euthyneura, Opisthobranchia and Pulmonata as traditionally defined were found non-monophyletic. The enigmatic amphibious and insectivorous Aitengidae clusters within Acochlidiacea, as sister to meiofaunal and brackish Pseudunelidae and limnic Acochlidiidae. Inclusion of this small acochlidian group resulted in redefinition of major groups within Heterobranchia , that has led to creation of
1134-438: A trait presently identified with at least primates , corvids , and cetaceans . In cladistics, a homoplasy is a trait shared by two or more taxa for any reason other than that they share a common ancestry. Taxa which do share ancestry are part of the same clade ; cladistics seeks to arrange them according to their degree of relatedness to describe their phylogeny . Homoplastic traits caused by convergence are therefore, from
1197-421: Is divergent evolution , where related species evolve different traits. Convergent evolution is similar to parallel evolution , which occurs when two independent species evolve in the same direction and thus independently acquire similar characteristics; for instance, gliding frogs have evolved in parallel from multiple types of tree frog . Many instances of convergent evolution are known in plants , including
1260-427: Is a secondary alcohol (i.e. has a methyl group). The methyl group of threonine greatly restricts the possible orientations of triad and substrate, as the methyl clashes with either the enzyme backbone or the histidine base. Consequently, most threonine proteases use an N-terminal threonine in order to avoid such steric clashes . Several evolutionarily independent enzyme superfamilies with different protein folds use
1323-517: Is a classic example, as flying insects , birds , pterosaurs , and bats have independently evolved the useful capacity of flight. 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. The opposite of convergence
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#17330846252701386-443: Is a continuum between parallel and convergent evolution, while others maintain that despite some overlap, there are still important distinctions between the two. When the ancestral forms are unspecified or unknown, or the range of traits considered is not clearly specified, the distinction between parallel and convergent evolution becomes more subjective. For instance, the striking example of similar placental and marsupial forms
1449-463: Is a membrane stretched across four extremely elongated fingers and the legs. The airfoil of the bird wing is made of feathers , strongly attached to the forearm (the ulna) and the highly fused bones of the wrist and hand (the carpometacarpus ), with only tiny remnants of two fingers remaining, each anchoring a single feather. So, while the wings of bats and birds are functionally convergent, they are not anatomically convergent. Birds and bats also share
1512-664: Is described by Richard Dawkins in The Blind Watchmaker as a case of convergent evolution, because mammals on each continent had a long evolutionary history prior to the extinction of the dinosaurs under which to accumulate relevant differences. The enzymology of proteases provides some of the clearest examples of convergent evolution. These examples reflect the intrinsic chemical constraints on enzymes, leading evolution to converge on equivalent solutions independently and repeatedly. Serine and cysteine proteases use different amino acid functional groups (alcohol or thiol) as
1575-578: Is likely that convergent adaptations to the interstitial habitat mask the truly phylogenetic signals. Schrödl & Neusser (2010) split Acochlidiacea into two (unranked) taxa and into six families like this: Hedylopsacean Acochlidiacea, whose evolution involves several habitat shifts from marine interstitial to amphibious or freshwater benthic habitats, possess complex excretory and reproductive systems . (unranked) Hedylopsacea has no superfamilies defined: Microhedylacean Acochlidiacea are exclusively found in interstitial spaces in sediment, and show
1638-574: Is likely that convergent adaptations to the interstitial habitat mask the truly phylogenetic signals. Schrödl & Neusser (2010) split Acochlidiacea into two (unranked) taxa and into six families like this: Hedylopsacean Acochlidiacea, whose evolution involves several habitat shifts from marine interstitial to amphibious or freshwater benthic habitats, possess complex excretory and reproductive systems . (unranked) Hedylopsacea has no superfamilies defined: Microhedylacean Acochlidiacea are exclusively found in interstitial spaces in sediment, and show
1701-560: Is poorly known. With a typically low reproductive output in Acochlidiacea (max. of 40 eggs in Pontohedyle milaschewitchii ), free veliger larvae are assumed to stay in the interstices of the sand grains rather than entering the water column thereby avoiding long distance dispersal . Fertilized eggs are attached to sand grains and might promote dispersal via current driven sediment transport along shorelines. This article incorporates CC-BY-2.0 text from references and CC-BY-SA-3.0 text from
1764-504: Is poorly known. With a typically low reproductive output in Acochlidiacea (max. of 40 eggs in Pontohedyle milaschewitchii ), free veliger larvae are assumed to stay in the interstices of the sand grains rather than entering the water column thereby avoiding long distance dispersal . Fertilized eggs are attached to sand grains and might promote dispersal via current driven sediment transport along shorelines. This article incorporates CC-BY-2.0 text from references and CC-BY-SA-3.0 text from
1827-542: Is responsible, say with brown dominant to blue eye colour . However, a single locus is responsible for about 80% of the variation. In lemurs, the differences between blue and brown eyes are not completely known, but the same gene locus is not involved. While most plant species are perennial , about 6% follow an annual life cycle, living for only one growing season. The annual life cycle independently emerged in over 120 plant families of angiosperms. The prevalence of annual species increases under hot-dry summer conditions in
1890-409: Is the camera eye of cephalopods (such as squid and octopus), vertebrates (including mammals) and cnidarians (such as jellyfish). Their last common ancestor had at most a simple photoreceptive spot, but a range of processes led to the progressive refinement of camera eyes —with one sharp difference: the cephalopod eye is "wired" in the opposite direction, with blood and nerve vessels entering from
1953-522: The Chenopodiaceae and the Amaranthaceae . Fruits with a wide variety of structural origins have converged to become edible. Apples are pomes with five carpels ; their accessory tissues form the apple's core, surrounded by structures from outside the botanical fruit, the receptacle or hypanthium . Other edible fruits include other plant tissues; the fleshy part of a tomato is the walls of
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2016-818: The Mesozoic , between the Triassic and Jurassic periods. The diversification of Acochlidia is estimated to have happened in the Jurassic with the split between Hedylopsacea and Microhedylacea . A cladogram showing phylogenetic relations of some genera and species within Acochlidiacea: Asperspina sp. Pontohedyle milaschewitchii Paraganitus ellynnae Microhedyle glandulifera Hedylopsis spiculifera Hedylopsis ballantinei Aiteng sp. Pseudunela sp. ► Strubellia paradoxa Acochlidium fijiiensis The life cycle of Acochlidiacea
2079-664: The Mesozoic , between the Triassic and Jurassic periods. The diversification of Acochlidia is estimated to have happened in the Jurassic with the split between Hedylopsacea and Microhedylacea . A cladogram showing phylogenetic relations of some genera and species within Acochlidiacea: Asperspina sp. Pontohedyle milaschewitchii Paraganitus ellynnae Microhedyle glandulifera Hedylopsis spiculifera Hedylopsis ballantinei Aiteng sp. Pseudunela sp. ► Strubellia paradoxa Acochlidium fijiiensis The life cycle of Acochlidiacea
2142-619: The pericarp . This implies convergent evolution under selective pressure, in this case the competition for seed dispersal by animals through consumption of fleshy fruits. Seed dispersal by ants ( myrmecochory ) has evolved independently more than 100 times, and is present in more than 11,000 plant species. It is one of the most dramatic examples of convergent evolution in biology. Carnivory has evolved multiple times independently in plants in widely separated groups. In three species studied, Cephalotus follicularis , Nepenthes alata and Sarracenia purpurea , there has been convergence at
2205-446: The proboscis of flower-visiting insects such as bees and flower beetles , or the biting-sucking mouthparts of blood-sucking insects such as fleas and mosquitos . Opposable thumbs allowing the grasping of objects are most often associated with primates , like humans and other apes, monkeys, and lemurs. Opposable thumbs also evolved in giant pandas , but these are completely different in structure, having six fingers including
2268-609: The Australian species recognizes 2 superfamilies and 5 families. The Acochlidia, a traditional "order" of the Opisthobranchia since their establishment by Odhner have formed one of the unsolved mysteries within Euthyneura . Their monophyly is widely accepted especially since a proposed sister group relationship of the acochlidian family Ganitidae with Sacoglossa (based on the dagger-shaped radula teeth) could be rejected based on
2331-443: The Australian species recognizes 2 superfamilies and 5 families. The Acochlidia, a traditional "order" of the Opisthobranchia since their establishment by Odhner have formed one of the unsolved mysteries within Euthyneura . Their monophyly is widely accepted especially since a proposed sister group relationship of the acochlidian family Ganitidae with Sacoglossa (based on the dagger-shaped radula teeth) could be rejected based on
2394-570: The Mesozoic ) all converged on the same streamlined shape. A similar shape and swimming adaptations are even present in molluscs, such as Phylliroe . The fusiform bodyshape (a tube tapered at both ends) adopted by many aquatic animals is an adaptation to enable them to travel at high speed in a high drag environment. Similar body shapes are found in the earless seals and the eared seals : they still have four legs, but these are strongly modified for swimming. The marsupial fauna of Australia and
2457-517: The N-terminal residue as a nucleophile. This commonality of active site but difference of protein fold indicates that the active site evolved convergently in those families. Conus geographus produces a distinct form of insulin that is more similar to fish insulin protein sequences than to insulin from more closely related molluscs, suggesting convergent evolution, though with the possibility of horizontal gene transfer . Distant homologues of
2520-471: The back of the retina, rather than the front as in vertebrates. As a result, vertebrates have a blind spot . Birds and bats have homologous limbs because they are both ultimately derived from terrestrial tetrapods , but their flight mechanisms are only analogous, so their wings are examples of functional convergence. The two groups have independently evolved their own means of powered flight. Their wings differ substantially in construction. The bat wing
2583-419: The diaphanid cephalaspidean Toledonia , or with runcinid or philinoid cephalaspideans . Molecular markers independent from direct ecological pressures suggested an unresolved basal opisthobranch origin for Acochlidia (based on nuclear 18S rRNA and 28S rRNA) (Vonnemann et al. 2005). A first combined multi-gene dataset led to the surprising result of Acochlidia clustering in a pulmonate relationship, united in
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2646-416: The diaphanid cephalaspidean Toledonia , or with runcinid or philinoid cephalaspideans . Molecular markers independent from direct ecological pressures suggested an unresolved basal opisthobranch origin for Acochlidia (based on nuclear 18S rRNA and 28S rRNA) (Vonnemann et al. 2005). A first combined multi-gene dataset led to the surprising result of Acochlidia clustering in a pulmonate relationship, united in
2709-437: The dolphin; among marine mammals; between giant and red pandas; and between the thylacine and canids. Convergence has also been detected in a type of non-coding DNA , cis-regulatory elements , such as in their rates of evolution; this could indicate either positive selection or relaxed purifying selection . Swimming animals including fish such as herrings , marine mammals such as dolphins , and ichthyosaurs ( of
2772-617: The exposed surfaces of the proteins, where they might interact with other components of the cell or the digestive fluid. The authors also found that homologous genes in the non-carnivorous plant Arabidopsis thaliana tend to have their expression increased when the plant is stressed, leading the authors to suggest that stress-responsive proteins have often been co-opted in the repeated evolution of carnivory. Phylogenetic reconstruction and ancestral state reconstruction proceed by assuming that evolution has occurred without convergence. Convergent patterns may, however, appear at higher levels in
2835-480: The four species-rich families of annuals ( Asteraceae , Brassicaceae , Fabaceae , and Poaceae ), indicating that the annual life cycle is adaptive. C 4 photosynthesis , one of the three major carbon-fixing biochemical processes, has arisen independently up to 40 times . About 7,600 plant species of angiosperms use C 4 carbon fixation, with many monocots including 46% of grasses such as maize and sugar cane , and dicots including several species in
2898-401: The identity of their sister group remained uncertain. Morphology-based analyses by Schrödl & Neusser, demonstrated that Acochlidia usually group with other mesopsammic (they live in interstitial spaces of marine sands) taxa, if any were included (i.e. with the sacoglossan Platyhedyle , the rhodopemorph Rhodope or the cephalaspideans Philinoglossa or Philine exigua ). Thus, it
2961-399: The identity of their sister group remained uncertain. Morphology-based analyses by Schrödl & Neusser, demonstrated that Acochlidia usually group with other mesopsammic (they live in interstitial spaces of marine sands) taxa, if any were included (i.e. with the sacoglossan Platyhedyle , the rhodopemorph Rhodope or the cephalaspideans Philinoglossa or Philine exigua ). Thus, it
3024-407: The lineages diverged and became genetically isolated, the skin of both groups lightened more, and that additional lightening was due to different genetic changes. Lemurs and humans are both primates. Ancestral primates had brown eyes, as most primates do today. The genetic basis of blue eyes in humans has been studied in detail and much is known about it. It is not the case that one gene locus
3087-516: The mammal lineage from the placentals. Hummingbird hawk-moths and hummingbirds have evolved similar flight and feeding patterns. Insect mouthparts show many examples of convergent evolution. The mouthparts of different insect groups consist of a set of homologous organs, specialised for the dietary intake of that insect group. Convergent evolution of many groups of insects led from original biting-chewing mouthparts to different, more specialised, derived function types. These include, for example,
3150-454: The metal ion transporters ZIP in land plants and chlorophytes have converged in structure, likely to take up Fe efficiently. The IRT1 proteins from Arabidopsis thaliana and rice have extremely different amino acid sequences from Chlamydomonas ' s IRT1, but their three-dimensional structures are similar, suggesting convergent evolution. Many examples of convergent evolution exist in insects in terms of developing resistance at
3213-405: The molecular level. Carnivorous plants secrete enzymes into the digestive fluid they produce. By studying phosphatase , glycoside hydrolase , glucanase , RNAse and chitinase enzymes as well as a pathogenesis-related protein and a thaumatin -related protein, the authors found many convergent amino acid substitutions. These changes were not at the enzymes' catalytic sites, but rather on
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#17330846252703276-436: The new clades Euopisthobranchia and Panpulmonata . Two more families were established. Both include slugs that are unusual among acochlidians for their anatomy and habitat (amphibious, terrestrial, or benthic in deeper waters): There is no fossil record of Acochlidiacea. Application of a molecular clock allowed estimation of divergence times for these groups. The split between Eupulmonata and Acochlidiacea took place in
3339-435: The new clades Euopisthobranchia and Panpulmonata . Two more families were established. Both include slugs that are unusual among acochlidians for their anatomy and habitat (amphibious, terrestrial, or benthic in deeper waters): There is no fossil record of Acochlidiacea. Application of a molecular clock allowed estimation of divergence times for these groups. The split between Eupulmonata and Acochlidiacea took place in
3402-474: The placental mammals of the Old World have several strikingly similar forms, developed in two clades, isolated from each other. The body, and especially the skull shape, of the thylacine (Tasmanian tiger or Tasmanian wolf) converged with those of Canidae such as the red fox, Vulpes vulpes . As a sensory adaptation, echolocation has evolved separately in cetaceans (dolphins and whales) and bats, but from
3465-401: The point of view of cladistics, confounding factors which could lead to an incorrect analysis. In some cases, it is difficult to tell whether a trait has been lost and then re-evolved convergently, or whether a gene has simply been switched off and then re-enabled later. Such a re-emerged trait is called an atavism . From a mathematical standpoint, an unused gene ( selectively neutral ) has
3528-404: The protein (positions 111 and 122). CTS-adapted species have also recurrently evolved neo-functionalized duplications of ATPalpha, with convergent tissue-specific expression patterns. Convergence occurs at the level of DNA and the amino acid sequences produced by translating structural genes into proteins . Studies have found convergence in amino acid sequences in echolocating bats and
3591-427: The reference. Convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last common ancestor of those groups. The cladistic term for the same phenomenon is homoplasy . The recurrent evolution of flight
3654-444: The reference. Hedylopsacea (unranked) Hedylopsacea (unranked) Microhedylacea Acochlidiomorpha Acochlidiida Acochlidea Acochlidia Acochlidiacea , common name acochlidians , are a taxonomic clade of very unusual sea snails and sea and freshwater slugs , aquatic gastropod mollusks within the large clade Heterobranchia . Acochlidia is a variant spelling. These are mostly very small animals, without
3717-462: The repeated development of C 4 photosynthesis , seed dispersal by fleshy fruits adapted to be eaten by animals, and carnivory . In morphology, analogous traits arise when different species live in similar ways and/or a similar environment, and so face the same environmental factors. When occupying similar ecological niches (that is, a distinctive way of life) similar problems can lead to similar solutions. The British anatomist Richard Owen
3780-401: The same conditions were encountered again, evolution could take a very different course." Simon Conway Morris disputes this conclusion, arguing that convergence is a dominant force in evolution, and given that the same environmental and physical constraints are at work, life will inevitably evolve toward an "optimum" body plan, and at some point, evolution is bound to stumble upon intelligence,
3843-467: The same genetic mutations. The Gymnotiformes of South America and the Mormyridae of Africa independently evolved passive electroreception (around 119 and 110 million years ago, respectively). Around 20 million years after acquiring that ability, both groups evolved active electrogenesis , producing weak electric fields to help them detect prey. One of the best-known examples of convergent evolution
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#17330846252703906-554: The thumb, which develops from a wrist bone entirely separately from other fingers. Convergent evolution in humans includes blue eye colour and light skin colour. When humans migrated out of Africa , they moved to more northern latitudes with less intense sunlight. It was beneficial to them to reduce their skin pigmentation . It appears certain that there was some lightening of skin colour before European and East Asian lineages diverged, as there are some skin-lightening genetic differences that are common to both groups. However, after
3969-408: Was the first to identify the fundamental difference between analogies and homologies . In biochemistry, physical and chemical constraints on mechanisms have caused some active site arrangements such as the catalytic triad to evolve independently in separate enzyme superfamilies . In his 1989 book Wonderful Life , Stephen Jay Gould argued that if one could "rewind the tape of life [and]
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