Category: Biochemistry

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The vital processes that occur in every living cell depend on chemical interactions between biological molecules. To name but a few of these biomolecules, nucleic acids (DNA and RNA) carry genetic information that is converted into proteins which themselves fulfil a diversity of roles, from cell structure to reaction catalysis. Lipids are key components of cell membranes and transport systems, and carbohydrates serve as signature molecules and raw material for generating energy. Convergent evolution is frequently found at the biochemical level, as fundamental compounds from metabolic enzymes to venomous toxins have repeatedly appeared in independent living groups.

Biochemical convergence is exemplified in an astonishing diversity of molecular contexts, a very few of which are mentioned here (see the main list below for more). Among several cases of toxin-related convergence, the potentially lethal saxitoxin and tetrodotoxin stand out. Both toxins are employed in a range of distantly related marine organisms and microbes as well as - in the instance of tetrodotoxin - in a few amphibians. Also on the theme of poisons, venom fangs are now known to have evolved not only in the snakes but also in various other reptile groups and in a few mammals and their close relatives. Animal eyes lenses are built from crystallin proteins of various kinds, independently recruited whenever needed. In one squid transparent crystallins form a pair of 'reverse eyes', allowing bioluminescent light out. Bioluminescence based on luciferin and the enzyme luciferase has evolved in a myriad of marine species, from dinoflagellates to jellyfish, crustaceans, squid and deep-sea fish as well as a few terrestrial insects such as the well-known 'fire-flies' (actually beetles) and predatory fungus gnats. Another enzyme, carbonic anhydrase, stands out as it is plays a critical role in CO2 metabolism throughout the living world and yet it has evolved independently as many six times. Turning briefly to plants, one intriguing biochemical convergence is the independent synthesis of anthocyanins for red autumn leaf pigmentation in many tree species. Latex and waxy compounds have also evolved many times in plants, as have specialised modes of carbon dioxide concentration (notably C4 and CAM photosynthesis) and the all-important capacity to fix nitrogen using microbial assistance.

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Topic Title Teaser text Availablity
Light producing chemicals: how to make bioluminescence

The most remarkable luciferin in terms of its distribution is known as coelenterazine. This nitrogen-ring based molecule is found in nine separate groups, ranging from radiolarians to fish.


Flying through the air on a summer's evening or sparkling in the ocean you may see magical flashes of light that signal some of nature's most enchanting creatures, those that are bioluminescent.

Luciferases n/a Not Available
Pheromone use in animals, fungi and plants n/a Not Available
Bioluminescence in arthropods n/a Not Available
Bioluminescence in marine animals n/a Not Available
Sponge spicules: form, genes and fibre-optics n/a Not Available
Carnivorous plants

All plants are harmless? Well, not quite - at least not when you're an insect...

Carbon dioxide concentration in plants n/a Not Available
Venom compounds n/a Not Available
Pufferfish (and inflation)

Pufferfish are some of the most extraordinary fish to have evolved, especially because of their capacity to swallow water and inflate themselves to something like a football. Not only that but some representatives can be deadly to the unwary diner...

Mimicry in fungi

Insects pollinating flowers are a familiar sight. But what happens when the "flower" is actually a fungus? Still "pollination", but now it is fungal spores. Read on to learn more about the fungi that mimic flowers...

Bioluminescence in fungi n/a Not Available
Autumn leaf colouration

Autumn colours are likely to be adaptive, as the 'default' is simply to remain green up to leaf fall, and both red and yellow leaf colouration have evolved independently on many occasions in gymnosperms and woody angiosperms.


Not many foods served in a restaurant can kill you, but pufferfish is the exception. Tetrodotoxin, the toxin responsible for such culinary fatalities, reveals a fascinating story of convergent evolution...

Venom and venom fangs in snakes, lizards and synapsids

Although the evolution of snake fangs itself provides us with a window on convergence, the presence of fang-like teeth in lizards, therapsids and mammals provides an even broader and more remarkable perspective.

Saxitoxin synthesis: from molluscs to algae

Saxitoxin has a similar molecular structure to tetrodoxin and a wide distribution amongst living organisms, with evidence that is has been recruited independently several times.

SNARE protein receptors and the evolution of multicellularity

There is an intriguing correlation with larger numbers of SNAREs and multicellularity, at least in plants and animals.

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Dandruff, Malassezia and Candida

The presence of Malassezia does not guarantee dandruff, as this fungus is commonly present on healthy skin, but it evidently central to dandruff production if other key factors support it.

Magnetotactic bacteria

Magnetotactic bacteria provide some excellent examples of convergent evolution.  In particular the ability to synthesize iron compounds has evolved at least twice, respectively employing iron oxide (magnetite) and iron sulphide.

Ink production in cephalopods and gastropods

A series of striking convergences can be found in the sea-hares (Aplysia), a group of gastropods and only remotely related to the cephalopods.  Not only do they emit ink clouds (the colour is derived from ingested red algae), but they also employ chemical cues that assist in defense.

Latex in plants and fungi

Latex is important in terms of defence not only because it typically gums-up attackers, notably insects, but often contains toxins.

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Sodium voltage-gated ion channels

Sodium voltage-gated ion channels are vital to electric signal transmission, but it is less widely appreciated that they are convergent and have evolved at least twice in groups outside the animals.

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Light sensitivity and optics in sponges

Some of the silica spicules of glass sponges are very long, and extraordinarily have a striking similarity to the optical fibres employed in the telecommunications industry.

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Venom in mammals (and other synapsids)

Beware the venomous shrew! Yes, venomous. And convergent on some formidable lizards...

Lipocalins for milk and pheromone transport

Lipocalins are proteins that bind to and transport small hydrophobic molecules such as lipids and steroids, and have been associated with biological processes such as milk production, pheromone transport and immune responses.

Haptoglobins: convergence of Hp2 allele

One of the allelic forms of haptoglobin, known as Hp2, in the case of humans and cow shows a striking convergence, notably in the so-called complement control protein (CCP) domain.

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Functions of plant waxes

Plant waxes are employed in contexts other than water retention, notably to deter insects or to provide a lethal glissade across which the prey of carnivorous pitcher plants slide to their doom.

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Silk production and use in arthropods

Remarkably, fossil silk is known, especially from amber of Cretaceous age. Material includes both silk with trapped insects, possibly from an orb-web, and strands with the characteristic viscid droplets that are the key in trapping prey.

Bacterial carboxysomes (and other microcompartments)

It is now clear that the cellular construction of at least the eubacteria is more complex than realized, and includes organelle-like structures known as microcompartments, of which the best known are the carboxysomes.

Alkaloids and other chemical defences n/a Not Available
Enzymes: convergence on active sites and reaction types

Enzymes make the world go round, each an evolutionary marvel - and convergent.

Evolution of fungicide resistance

Just as with insecticides, we see both evolution in action and also striking instances of convergence where resistance is acquired independently

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Evolution of herbicide resistance

Unfortunately, just as in insecticides, resistance rapidly develops and is not only an excellent example of evolution in action, but also is strikingly convergent.

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Pigmentation in birds

The striking plumage of the turaco owes its colour to turacoverdin. Interestingly, this is a copper based pigment and is also convergent in the jacanas, a group of wading birds.

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Carbonic anhydrase in vertebrates, plants, algae and bacteria

Carbonic anhydrase is extremely convergent and may have evolved as many as six times. The most familiar variants are α, β and γ carbonic anhydrases.

Gene regulation and cell cycles in bacteria and eukaryotes

Regulation of gene networks and cell cycles are of particular importance for convergence because genomic organization in bacteria shows significant differences from the eukaryotes.

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Sap feeding and honey-dew production in insects

Interestingly, it has now been shown that the saliva of the aphids has an analogue to the anti-coagulant properties of blood suckers, subverting the wound repair mechanism of the plant.

Chloroplast and mitochondrial plastid origins

Not only are there intriguing parallels in the story of gene loss in chloroplasts and mitochondria, but there is also the re-invention of bacterial pathways, such as oxidation of quinols.

Myriapods (centipedes and millipedes): defence and terrestrialisation

This group of arthropods is also important because they show independent invasion of the land (terrestrialization), which not surprisingly has led to important convergences.

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Zinc in teeth

On land, we find the employment of zinc to reinforce feeding structures in the fangs of spiders, and also in a variety of insect groups.

Plumage in birds

Exampes of convergece in bird plumage are the well-known tendency for different groups of tropical sea-birds to have dark plumage, and what may represent Müllerian mimicry in the pitohuis, which are famous for their convergent use of toxic alkaloids.

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Insecticide production: from plants to primates

Application of insecticides, such as against mosquitoes, has been documented in several primates and birds.

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Pheromones in arthropods

Not surprisingly this is a rich area of insights into evolutionary convergence because if an animal, such as a spider, can independently evolve the pheromone then a sexual lure is turned into a metaphorical honey trap.

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Haemocyanin in arthropods and molluscs

The degree of similarity between the active sites in arthropod and molluscan haemocyanin has been called “remarkable” and “startling”, but actually suggests that wherever in the universe life employs copper for aerobic respiration it will call upon haemocyanin.

Crystallins: eye lens proteins

Whereas typically technology demands furnaces, so that the glass for a lens is produced at hundreds of degrees Celsius and then requires most careful grinding, so nature calls upon proteins known as crystallins.

Annelids: insights into convergence

Notable instances of convergence involving annelids include luminescence, moulting and the independent evolution of both compound eyes (e.g. in sabellids) and camera eyes (in alciopids).

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Defence in frogs: toxins and camouflage

The many striking examples of convergence most famously include the case of mimicry, but the question of defence also extends to the use of toxins (and venoms), such as alkaloids, where we also find molecular convergence.

Moulting in arthopods, annelids and other animals

Moulting has, however, evolved independently in other groups, including the annelids where some polychaetes shed their jaws.

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Bioluminescent reverse eyes in squid

Normally one thinks of an eye as a structure that allows light to pour into the body, but in at least some squid (cephalopods) the opposite has been achieved.

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Reflective tissues

Other cephalopods achieve reflectivity by employing collagen fibrils, of which the deep-sea Vampyroteuthis is perhaps the most striking example.

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Ultraviolet (UV) absorption in vertebrates and cephalopods

In some vertebrates (fish, mammals) and cephalopods we find an interesting convergence whereby some of the incoming ultraviolet is screened out.

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