World's Largest Organism

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, though Gaia theory would consider the whole of the biosphere as a sort of superorganism.)

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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 hectares (.43 km²) and is estimated to weigh 6,600 tons.

A giant fungus of the species Armillaria ostoyae 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 is about 8 km (4.3 miles) in length.

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Excluding multi-stem trees, the General Sherman tree, an individual Giant Sequoia with a volume of 1487 m³, would hold the title of the world's largest living organism, if measured in volume and mass. This tree stands 83.8 m (274 ft 11 in) tall and the trunk alone is estimated to weigh over 2000 tons.

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The largest single-stem tree ever measured was the “Lindsey Creek Tree,” a coastal redwood with a minimum trunk volume of over 2500 m³ and a mass of over 3600 tons, which fell over during a storm in 1905.

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By volume and weight, the largest known animal ever to have lived is the blue whale, an endangered species whose official record length is 33.58 m (110 ft 2 inches), and weight 210 tons (for a pregnant female).

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The largest land animals today are male Savannah Elephants, with one known example weighing around 12,272 kg (27,000 lb), though many extinct species, such as many dinosaurs, were much larger.

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