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The largest organism found on earth can be measured using a variety of methods. It could be defined as the largest by volume, mass, height, or length. Some creatures group together to form a superorganism, though this cannot truly be classed as one large organism. (The Great Barrier Reef, the world's largest coral reef (stretching 2,000 km) has been shown to be a collection of many organisms and is the largest known superorganism.)

The Aspen tree (Populus tremuloides) forms large stands of genetically identical trees (technically, stems) connected by a single underground root system. These trees form through root sprouts coming off an original parent tree, though the root system may not remain a single unit in all specimens. The largest known fully-connected Aspen is a grove in Utah nicknamed Pando, and some experts call it the largest organism in the world, by mass or volume. It covers .43 km² (106 acres) and is estimated to weigh 6,600 short tons (6,000 t).

A giant fungus of the species Armillaria ostoyae (Honey Mushrooms) in the Malheur National Forest in Oregon was found to span 8.9 km² (2,200 acres), which would make it the largest organism by area. Whether or not this is an actual individual organism, however, is disputed: some tests have indicated that they have the same genetic makeup , but unless its mycelium is fully connected, it is a clonal colony of numerous smaller individuals. Another clonal colony that rivals the Armillaria and the Populus colonies in size is a strand of the giant marine plant, Posidonia oceanica, discovered in the Mediterranean Sea near the Balearic Islands. It covers a band roughly 8 km (4.3 miles) in length.

Excluding multi-stem trees, the General Sherman, an individual Giant Sequoia tree with a volume of 1487 m³, would hold the title of the world's largest living organism, if measured in volume. This tree stands 83.8 m (274 ft 11 in) tall and the trunk alone is estimated to weigh over 2,000 tons. The largest single-stem tree ever measured was the “Lindsey Creek Tree,” a coast redwood with a minimum trunk volume of over 2,500 m³ and a mass of over 3,600 tons, which fell over during a storm in 1905.

By volume and weight, the largest known living animal is the blue whale, an endangered species whose official record length is 33.58 m (110 ft 2 in), and weight 210 tons (for a pregnant female). The largest land animals today are male Savannah Elephants; one known example weighed roughly 12,272 kg (27,000 lb), although some extinct species, including many dinosaurs, were much larger.

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Invertebrates

Sponges (Porifera)

Arguably the most primitive form of animals in existence, the largest species of sponge is the barrel sponge, Xestospongia muta. These massively-built sponges can reach 2.42 m (8 ft) in height and can be of about the same number of feet across the thickest part of the "body".

• Calcareous sponges (Calcarea). The largest of these small, inconspicuous sponges is probably the species Pericharax heteroraphis, attaining a height of 30 cm (1 ft). Most calcareous sponges do not exceed 10 cm (4 in) tall.
• Hexactinellid sponges (Hexactinellida). A relatively common species, Rhabdocalyptus dawsoni, can reach a height of 1 m (3.3 ft) once they are of a very old age. This is the maximum size recorded for a hexactinellid sponge.

Cnidarians (Cnidaria)

The lion's mane jellyfish is the largest cnidaria species, of the class Scyphozoa. The largest specimens of this giant can attain a bell diameter of 2.5 m (8 ft), a weight of 150 kg (330 lb.) and can possess tentacles as long as 40 m (120 ft) or more.

• Corals and sea-anemones (Anthozoa). The largest individual species are the sea-anemones of the genus Discoma, which can attain a mouth disc diameter of 60 cm (2 ft). Longer, but much less massive overall, are the anemones of the genus Ceriantharia, at up to 2 m (6.6 ft) tall. Communities of coral can be truly massive, a single colony of the Porites genus can be over 10 m (33 ft), but the actual individual organisms are quite small.
• Box jellyfish (Cubozoa). The largest of the box jellyfish is the species Chironex fleckeri, which can attain a mass of 6 kg (13.2 lb in weight), a 30 cm (1 ft) bell and a tentacle length up to 2 m (6.6 ft). This species is also the most common and dangerous box jelly.
• Hydrozoans (Hydrozoa). The colonial siphonophore Praya dubia can attain lengths of 40-50 m (130-165 ft).

Flatworms (Platyhelminthes)

The largest terrestrial species of this phylum of mostly parasites, called flatworms in common language, is the greenhouse planarian, Bipalium kewense, of the class Turbellaria. This planarian can reach a length of 60 cm (2 ft) and is quite massive for a flatworm.

• Monogenean flatworms (Monogenea). The largest members of this group of very small parasites are among the genus of capsalids , Listrocephalos, reaching a length of 2 cm (0.8 in).
• Flukes (Trematoda). The largest species of fluke is Fasciolopsis buski, which most often attacks humans and livestock. One of these flukes can be up to 7.5 cm (3 in) long and 2 cm (0.8 in) thick.
• Tapeworms (Cestoda). The largest species of tapeworm is commonly called the fish tapeworm, Diphyllobothrium latum, since they are commonly contracted from eating fish. This devastating parasite has been recorded as reaching a length of 20 m (66 ft) in the internal organs of a human, and a length of 30 m in other hosts.

Roundworms (Nematoda)

The largest roundworm, Placentonema gigantisma, is a parasite found in the placentas of sperm whales which can reach up to 9 m in length.

Segmented worms (Annelida)

The largest of the segmented worms is the African giant earthworm, Microchaetus rappi. This huge worm can reach a length of as much as 6.7 m (22 ft) and can weigh over 1.5 kg (3.1 lb). Only the giant Gippsland earthworm, Megascolides australis, and a few giant polychaetes reach nearly comparable sizes, reaching 4 m (13 ft) and 3.6 m (11.9 ft), respectively.

Echinoderms (Echinodermata)

The largest species of echinoderm in terms of bulk is the starfish species, Thromidia catalai, of the class Asteroidea, which reaches a weight of over 6 kg (13.2 lb). However, at a maximum span of 63 cm (25 in), it is quite a bit shorter than some other echinoderms. The longest-bodied echinoderm is the brisingid starfish Midgardia xandaros, reaching a span of 1.4 m (4.5 ft), despite being quite slender.

• Crinoids (Crinoidea). The largest species of crinoid is the unstalked feather-star, Heliometra glacialis, reaching a total width of 78 cm (31 in) and an individual arm length of 35 cm (14  in). In the past, crinoids grew much larger, and stalk lengths up to 40 m (130 ft) have been found in the fossil record.
• Sea-urchins & allies (Echinoidea). The largest sea urchin is the species Sperosoma giganteum, which can reach a shell width of 33 cm (13 in).
• Sea-cucumbers (Holothuroidea). The bulkiest species of sea cucumber is Stichopus variegatus, weighing several pounds, being about 21 cm (8.3 in) in diameter, and reaching a length of 1 m (3.3 ft) when fully extended. Species of sea cucumber in the genus Synapta can reach an extended length of 2 m (6.6 ft), but are extremely slender.
• Brittle stars (Ophiuroidea). The largest known specimen of brittle star is Gorgonocephalus stimpsoni. This species can measure 70 cm (28 in) in arm length and has a disk diameter of about 14.3 cm (5.63 in).

Ribbon worms (Nemertea)

The largest nemertean, and the longest extant animal, is the bootlace worm, Lineus longissimus. A specimen found washed ashore on a beach in St. Andrews, Scotland in 1864 was recorded at a length of 55 m (180 ft).

Molluscs (Mollusca)

Both the largest mollusk and the largest of all invertebrates is believed to be the Colossal Squid, Mesonychoteuthis hamiltoni. Current estimates put its maximum size at 12 to 14 metres (39–46 ft) long, based on analysis of smaller specimens. On February 22, 2007, authorities in New Zealand announced the capture of the largest colossal squid seen. It was later measured at 10 m (33 ft) long and 494 kg (1,098 lb) in weight.

The Giant Squid (Architeuthis dux) was previously thought to be the largest squid, and while it is less massive and has a smaller mantle than the Colossal Squid, it may exceed the colossal squid in overall length including tentacles. The giant squid can measure up to 13 m (43 ft) or more from tentacle tip to tail tip, or 2.25 m (7.4 ft) in mantle length, and can weigh up to 275 kg (600 lb).

• Aplacophorans (Aplacophora). The largest of these worm-like, shell-less mollusks are represented in the genus Epimenia, which can reach 30 cm (12 in) long. Most aplacophorans are less than 5 cm (2 in) long.
• Chitons (Polyplacophora). The largest of the chitons is the gumboot chiton, Cryptochiton stelleri, which can reach a length of 33 cm (13 in).
• Bivalves (Bivalvia). The largest of the bivalve mollusks is the giant clam, Tridacna gigas. Although even more enormous sizes have been reported for this monstrous but passive animal, the top verified size is 273 kg (600 lb), 1.16 m (3.85 ft) in length and 76 cm (30 in) wide. The largest bivalve ever was Platyceramus platinus, a Cretaceous giant that reached an axial length of up to 3 m (nearly 10 ft).
• Gastropods (Gastropoda). The largest of this most diverse and successful mollusk class is the baler conch, Syrinx aruanus, reaching a size of 16.4 kg (36 lb), a length of 70 cm (28 in) and a width of 96 cm (38 in). The largest of the terrestrial snails is the Giant African land snail, Achatina fulica, at up to 1 kg (2.2 lb) and 35 cm (14 in) long.
• Cephalopods (Cephalopoda). (See Cephalopod size.) While generally much smaller than the giant Architeuthis and Mesonychoteuthis, the largest of the octopuses, the North Pacific Giant Octopus, Enteroctopus dofleini, can be very large. The largest confirmed weight of a giant octopus is 71 kg, with a 7-metre (23 ft) arm span.

Arthropods (Arthropoda)

The Japanese spider crab, Macrocheira kaempferi, a crustacean of the class Malacostraca, is the largest arthropod in the world in overall size, weighing up to 20 kg (44 lb), having a body up to 60 cm (2 ft) long and having a leg span of almost 4 m (13 ft). It is indisputably the largest member of Brachyura (crabs).

However, the American lobster, Homarus americanus, another crustacean and the largest member of Astacidea (lobsters and crayfish), rivals the Japanese spider crab in mass, if not dimension. This lobster has been recorded at heavier weights, up to 22 kg (48.4 lb), and can measure 1.18 m (3.9 ft) along the body.

The coconut crab, Birgus latro, also a crustacean, is the largest land arthropod and the largest land invertebrate, up to 40 cm (1.3 ft) long and weighing up to 4 kg (8.8 lb). Its legs may span 1 m (3.25 ft).

The largest arthropod ever known to exist was the eurypterid (sea scorpion) Jaekelopterus, which was between 2.5 and 2.6 m (8.2-8.5 ft) in length . It was closely followed by Pterygotus, an aquatic eurypterid that was up to 2.3 m (7.5 ft) in length. The closest living relatives of Eurypterida are the arachnids, horseshoe crabs, and sea spiders.

• Arachnids (Arachnida). The largest species of arachnid is probably the Goliath birdeater, Theraphosa blondi. However, of very comparable dimensions and possibly even greater mass, are the Chaco golden knee, Grammostola aureostriata, and the Brazilian salmon pink, Lasiodora parahybana. Some of these huge New World "tarantulas" have been recorded as reaching a leg span of 28 cm (11 in), a body length over 9 cm (3.5 in) and a body weight exceeding 85 g (3 oz). The largest of the scorpions is the species Heterometrus swammerdami, which can reach 29 cm (11.5 in) long and a weight of up to 57 g (2 oz). However, they were dwarfed by Pulmonoscorpius kirktonensis, a giant extinct species of scorpion from Scotland.
• Branchiopods (Branchiopoda). The largest of these primarily freshwater crustaceans is probably Branchinecta gigas, which can reach a length 10 cm (3.9 in).
• Centipedes (Chilopoda). The biggest of the centipedes is the Amazonian giant centipede, Scolopendra gigantea, reaching a relatively enormous length of 33 cm (13 in).
• Millipedes (Diplopoda). Two species of millipede both reach a very large size Archispirostreptus gigas and Scaphistostreptus seychellarum. Both of these species can slightly exceed a length of 28 cm (11 in). The 300-million year old Arthropleura, either a primitive millipede or a close relative, was the largest land invertebrate ever, having measured at least 2.5 m (8.2 ft) long and 45 cm (18 in) wide.
• Barnacles & allies (Maxillopoda). The largest species is a copepod (Pennella balaenopterae), known exclusively as a parasite from the backs of Fin Whales. The maximum size attained is 32 cm (about 13 in). The largest of the barnacles is the giant acorn barnacle, Balanus nubilis, reaching 7 cm (2.8 in) in diameter and 12.7 cm (5 in) high.
• Horseshoe crabs (Merostomata). The four modern horseshoe crabs are of roughly the same sizes, at up to 60 cm (2 ft) in length. Easily the best known species is Limulus polyphemus of North America.
• Ostracods (Ostracoda). The largest of these small and little-known but numerous crustaceans is the species Gigantocypris agassizii, reaching a maximum length of 3 cm (1.3 in).
• Amphipods, Isopods, and allies (Peracarida). The largest species is the giant isopod, which can reach a length of 45 cm (18 inches) and a weight of 1.7 kg (3.7 lb).
• Sea spiders (Pycnogonida). The largest of the sea spiders is the deep-sea species Colossendeis colossea, attaining a leg span of nearly 60 cm (2 ft).
• Remipedes (Remipedia). The largest of these cave-dwelling crustaceans is the species Godzillius robustus, at up to 4.5 cm (1.8 in).
• Trilobites (Trilobita). The largest of these extinct marine arthropods, a specimen of Isotelus rex from Manitoba attained a length over 70 cm (27 inches).

Insects (Insecta)

Insects, which are a type of arthropod, are easily the most numerous group of organisms on the planet, with about a million species identified so far. The title of heaviest insect in the world has many rivals, the most frequently-crowned of which is the larval stage of the goliath beetle, Goliathus goliatus, the top size of which is at least 115 g (4.1 oz) and 11.5 cm (4.5 in). The largest confirmed weight of an adult insect is 71 grams for a giant weta, Deinacrida heteracantha, although it is likely one of the elephant beetles, Megasoma elephas & Megasoma actaeon, or goliath beetles, both of which can commonly exceed 50 g (3 oz) and 10 cm (4 in), can reach a higher weight.

The longest insects are the stick insects, see below.

Representatives of the extinct dragonfly-like order Protodonata such as the Carboniferous Meganeura monyi and the Permian Meganeuropsis permiana are the largest insect species ever known. These creatures had a wingspan of some 70 cm (28 in) and a body weight of over 452 g (1 lb), making them about the size of a crow.

• Cockroaches (Blattodea). The largest cockroach is the giant burrowing cockroach (Macropanesthia rhinoceros). This species can attain a length of 8.3 cm (3.3 in) and a weight of 36 g (1.3 oz).
• Beetles (Coleoptera). The beetles are the largest order of organisms on earth, with about 350,000 species so far identified. The most massive species are the Goliathus, Megasoma and Titanus beetles already mentioned. The longest species is the Hercules beetle, Dynastes hercules with a maximum overall length of at least 19 cm (7.5 in) including the very long antennae, and a weight of up to 85 g (3 oz), about an ounce less than the bulkier beetles.
• Earwigs (Dermaptera). The largest of the earwigs is the St. Helena earwig, Labidura herculeana, which is up to 8.4 cm (3.3 in) in length.
• True flies (Diptera). The largest species of this huge order is the species Gauromydas heros, which can reach a length of 6 cm (2.4 in) and a wingspan of 10 cm (4 in). Species of crane fly, the largest of which is Holorusia brobdignagius, can attain a length of 23 cm (9 in) but are extremely slender and much lighter in weight than Mydas.
• Mayflies (Ephemeroptera). The largest mayflies are members of the genus Proboscidoplocia from Madagascar. These insects can reach a length of 5 cm (2 in).
• True bugs (Hemiptera). The largest species of this diverse, huge order is a giant water bug, Lethocerus maximus. This species can attain a length of 11.6 cm (4.6 in), although it is more slender and less heavy than most other insects of this size (principally the huge beetles).
• Ants & allies (Hymenoptera). The largest of the ants, and the heaviest species of the order, are the females of Dorylus helvolus, reaching a length of 5 cm (2 in). The ant that averages the largest for the mean size of the whole colony is Dinoponera gigantea, averaging up to 3.3 cm (1.3 in). The largest of the bee species, also in the order Hymenoptera, is Megachile pluto, the females of which can be 3.8 cm (1.5 in) long, with a 6.3 cm (2.5 in) wingspan. The largest wasp is probably the so-called tarantula hawk species Pepsis pulszkyi, at up to 6.8 cm (2.8 in) long and 11.6 cm (4.6 in) wingspan, although many other Pepsis approach a similar size.
• Termites (Isoptera). The largest of the termites is the African species Macrotermes bellicosus. The huge larvae of this species can attain a length of 10.6 cm (4.2 in) and breadth of 5.5 cm (2.2 in); the adults, on the other hand, are about a third of the size.

• Moths & allies (Lepidoptera). The largest species is probably either the Queen Alexandra's birdwing, Ornithoptera alexandrae, a butterfly, or the Atlas moth, Attacus atlas, a moth. Both of these species can exceed a length of 8 cm (3.2 in), a wingspan of 28 cm (11 in) and a weight of 12 g. Their larvae can weigh up to 58 g (1.9 oz). However, the White Witch, Thysania agrippina, has the longest recorded wingspan of the order, and indeed of any living insect, at up to at least 30 cm (12 in), though it is exceeded in surface area and mass by both Ornithoptera and Attacus.
• Praying mantises (Mantodea). The largest species of this order is the Chinese mantis, Tenodera aridifolia. The females of this species can attain a length of up to 10.6 cm (4.2 in).
• Dragonflies (Odonata). The largest living species of dragonfly is Megaloprepus caeruleata, attaining a size of as much as 19 cm (7.5 in) across the wings and a body length of over 12 cm (4.7 in). The largest species of dragonfly ever is the extinct Meganeura.
• Grasshoppers & allies (Orthoptera). The largest of this widespread, varied complex of insects is the giant weta, Deinacrida heteracantha, of New Zealand. This formidable insect can weigh over 75 g (2.6 oz) and measure up to nearly 10 cm (4 in), rivaling the huge beetles in size.
• Stick insects (Phasmatodea). The longest known stick insect is Phobaeticus chani, with one specimen held in the Natural History Museum in London measuring 567 millimetres (22.3 in) in total length. This measurement is however with the front legs fully extended. The body alone still measures 357 millimetres (14.1 in). The species with the second longest body is Phobaeticus kirbyi, which measures up to 328 millimetres (12.9 in), while the overall length (from the hind to the front legs) is up to 546 millimetres (21.5 in), and the body weight is up to 72 g (2.5 oz). The second longest insect in terms of total length is Phobaeticus serratipes, measuring up to 555 millimetres (21.9 in).
• Stoneflies (Plecoptera). The largest species of stonefly is Pteronarcys californica, a species favored by fishermen as lures. This species can attain a length of 5 cm (2 in) and a wingspan of nearly 7.5 cm (3 in).
• Booklice (Psocoptera). The largest of this order of very small insects are the barklouse of the genus Psocus, the top size of which is about 1 cm (0.4 in).
• Fleas (Siphonaptera). The largest species of flea is Hystrichopsylla schefferi. This parasite is known exclusively from the fur of the Mountain Beaver and can reach a length of 1.2 cm (0.5 in).
• Thrips (Thysanoptera). Members of the genus Phasmothrips are the largest kinds of thrips. The maximum size of these species is approximately 1.3 cm (0.5 in).

Plants

The largest single-stem plants are all members of the conifer division. By volume and mass, the largest tree is the Giant Sequoia (Sequoiadendron giganteum). They grow to an average height of 70 – 85 m (230 – 280 ft) and 5 – 7 m (16 – 23 ft) in diameter. Specimens have been recorded to be up to 94.9 m (307 ft) in height and (not the same individual) 8.98 m (29 ft) in diameter; the largest individual is the General Sherman tree, with a volume of 1,489 m³. Although not so large in volume, the closely related Coast Redwood (Sequoia sempervirens) is taller, reaching a maximum height of 115.55 m (379.1 ft). These trees dwarf any other non-communal organism, as even the largest Blue Whales are likely to weigh one-sixteenth as much as a large Giant Sequoia or Coast Redwood. See record trees for other tree records.

• Algae. The largest form of algae is the huge form of seaweed from the northwestern Pacific known as the giant kelp (Macrocystis pyrifera). The record-sized stem from one of these just slightly exceeded 60 m (200 ft).
• Liverworts (Marchantiophyta). The largest species of liverwort is a New Zealand species, Schistochila appendiculata. The top size of this species is 1.1 m (3.6 ft) long, a diameter of 2.5 cm (1 in) and a stem length of 10 cm (4 in).
• Mosses (Bryophyta). The world's largest moss is Dawsonia superba, of New Zealand. This species can be 50 cm (20 in) tall.
• Horsetails (Equisetophyta). The largest of horsetails is the species Equisetum myriochaetum, of central Mexico. The biggest specimen known was 8 m (26.4 ft) tall and had a diameter of 2.5 cm (1 in).
• Ferns (Pteridophyta). The largest species of fern is the majestic King Fern (Angiopteris evecta), of the Australasian area. A single frond of this plant can exceed 5 m (16.5 ft) in height.
• Conifers (Pinophyta). Besides the giant Sequoiadendron and Sequoia already mentioned, the conifers also include the largest tree by circumference in the world, the Montezuma Cypress (Taxodium mucronatum). The thickest recorded tree, found in Mexico, is called Árbol del Tule, with a circumference of 35.87 m (118.3 ft) and a diameter of 11.42 m (37.5 ft) at 1.5 m (5 ft) above ground level.
• Cycads (Cycadophyta). The largest species of cycad is Hope's Cycad (Lepidozamia hopei), of the Queensland area of Australia. The largest examples of this species have been over 17 m (56 ft) tall and have had a diameter of over 50 cm (20 in).
• Flowering plants (Magnoliophyta). This is the most diverse and numerous division of plants, with upwards of 400,000 species. Typically the largest flowering plant (angiosperm) has been considered Eucalyptus regnans, which can reach heights of 99.6 m (327 ft).

Stands of trees connected to a single root system (a single organism genetically) may be considered the largest organisms, and the largest flowering plants. The largest known such colony is a male Aspen in Utah, nicknamed Pando (Populus tremuloides), which is estimated to weigh in at approximately 6,000 tonnes (6,615 tons).

Another form of flowering plant that rivals Pando as the largest organism on earth in breadth, if not mass, is the giant marine plant, Posidonia oceanica, discovered in the Mediterranean Sea near the Balearic Islands, Spain. Its length is about 8 km (4.3 miles). Although this plant has not been proven to be a single connected organism, all the samples do have the same DNA. It may also be the oldest living organism in the world, with an estimated age of 100,000 years.

Other records among flowering plants include, the title of largest flower, which belongs to the species Rafflesia arnoldii. One of these flowers can reach a diameter of 1 m (3.3 ft) and weigh up to 11 kg (24 lb). The largest unbranched inflorescence, resembling (but not qualifying as) a giant flower, belongs to the Titan Arum (Amorphophallus titanum), reaching almost 3 m (10 ft) in height. The absolute largest inflorescence, at up to 8 m (26.5 ft) long, is borne by the Talipot palm (Corypha umbraculifera) of India.

Fungi

The largest living fungus may be a honey fungus of the species Armillaria ostoyae.

A mushroom of this type in the Malheur National Forest in the Blue Mountains of eastern Oregon, U.S. was found to be the largest fungal colony in the world, spanning 8.9 km² (2200 acres) of area. This organism is estimated to be 2400 years old. The fungus was written about in the April 2003 issue of the Canadian Journal of Forest Research. While an accurate estimate has not been made, the total mass of the colony may be as much as 605 tons. If this colony is considered a single organism, then it is the largest known organism in the world by area, and rivals the aspen grove "Pando" as the known organism with the highest living biomass. It is not known, however, whether it is a single organism with all parts of the mycelium connected.

In Armillaria ostoyae each individual mushroom (the fruiting body, similar to a flower on a plant) has only a 5 cm (2 inch) stem and a bell of up to 12.5 cm (5 in) across. There are many other fungi which produce a larger individual size mushroom, the largest being Rigidoporus ulmarius. Rigidoporus is up to 284 kg (626 lb), 1.66 m (5 ft 6 in) tall, 1.46 m (4 ft 10 in) across, and has a circumference of 4.9 m (16 ft 2 in). 2 in).

Other kingdoms

• Protists. Among the organisms that are not multicellular, the largest are the slime moulds, such as Physarum polycephalum, some of which can cover an area more than 1,000 cm² (1 sq ft). The largest species traditionally considered protozoa are giant amoeboids like foraminiferans. One such species, the xenophyophore Syringammina fragilissima, can attain a size of 20 cm (8 in). The largest ciliates, such as Stentor, can attain a length over 1 mm. The largest stramenopiles are the giant kelps, Macrocystis pyrifera, which can grow to a height of over 45 m (150 ft).

• Bacteria. The largest species of bacterium ever discovered is Thiomargarita namibiensis, which grows to 0.75 mm (0.03 in) in diameter, making it visible to the naked eye and up to a million times the size of more typical bacteria.

• Viruses. The largest known virus is the mimivirus (the Acanthamoeba polyphaga mimivirus), with mature particles of 400 nm in diameter (icosahedral capsid), 800,000 bases and 900 genes. Later research suggested that it could be up to 800 nm long, 1.2 Mbp and 1,260 genes.

See also

• Smallest organisms
• Deep-sea gigantism
• Giant animal
• Largest body part
• List of "largest" articles

Notes

1. ^ Consensus Document on the Biology of Populus, OECD (.doc file)
2. Quaking Aspen by the Bryce Canyon National Park Service
3. largest living thing
4. ^ The Humongous Fungus--Ten Years Later at the University of Wisconsin, Department of Botany. Accessed 20 August 2005.
5. ^ Beale, Bob. 10 April 2003. Humungous fungus: world's largest organism? at Environment & Nature News, ABC Online. Accessed 20 August 2005.
6. ^ Ibiza's Monster Marine Plant. Ibiza Spotlight, 28 May 2006.
7. The General Sherman Tree, Sequoia National Park at the National Park Service. Accessed 20 August 2005.
8. superlative trees
9. Worm Digest - The Mighty Worm
10. Ponsonby, Dr. David (2005). The Anatomy of the Sea. Vancouver: Raincoast Books. p. 129. ISBN 0-8118-4633-4. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
11. Carwardine, M. 1995. The Guinness Book of Animal Records. Guinness Publishing. p. 232.
12. "NZ's colossal squid to be microwaved", New Zealand Herald
13. O'Shea, S. 2003. "Giant Squid and Colossal Squid Fact Sheet". The Octopus News Magazine Online.
14. Paleoecology of giant Inoceramidae (Platyceramus) on a Santonian (Cretaceous) seafloor in Colorado
15. Cosgrove, J.A. 1987. Aspects of the Natural History of Octopus dofleini, the Giant Pacific Octopus. M.Sc. Thesis. Department of Biology, University of Victoria (Canada), 101 pp.
16. "Octopus - Species".
17. Goliath Beetle
18. David M. Williams (2001-04-21). "Chapter 30 — Largest Insect". Book of Insect Records. University of Florida.
19. "World's longest insect revealed". Natural History Museum. 2008-10-16. Retrieved 2008-10-16.
20. "Revision of Oriental Phasmatodea: The tribe Pharnaciini Günther, 1953, including the description of the world's longest insect, and a survey of the family Phasmatidae Gray, 1835 with keys to the subfamilies and tribes (Phasmatodea: "Anareolatae": Phasmatidae)" (PDF). Zootaxa. 1906. Auckland, New Zealand: Magnolia Press: 1-316 pp. 2008. ISSN 1175-5326. Retrieved 2008-10-16. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
21. ^ Brock, P.D. 1999. The amazing world of stick and leaf-insects. Cravitz Printing Co., Essex, England.
22. Seow-Choen, F. (1995). The longest insect in the world. Malayan Nat. 48: 12.
23. Gymnosperm Database: Sequoiadendron giganteum
24. Redwood, Sequoia sempervirens
25. The large hairy cap mosses (family Polytrichaceae)
26. "Eucaypt redemption". Eastern Native Tree Society. Retrieved 2008-11-19.
27. Mycologist's site about giant Armillaria in Michigan's Upper Peninsula
28. BBC News report about the largest Armillaria in the world

References

• Wood, The Guinness Book of Animal Facts and Feats. Sterling Pub Co Inc (1983), ISBN 978-0851122359

• Organisms
• World records
• Superlatives