Largest organisms

(Grizzly Giant pictured) is the world's most massive tree The largest single-stem tree by wood volume and mass is the giant sequoia (Sequoiadendron giganteum), native to California's Sierra Nevada; it typically grows to a height of and in diameter. The largest organism in the world, according to mass, is the aspen tree whose colonies of clones can grow up to in size. The largest such colony is Pando, in the Fishlake National Forest in Utah. A form of flowering plant that far exceeds Pando as the largest organism on Earth in area and potentially also mass, is the giant marine plant, Posidonia australis, living in Shark Bay, Australia. Its length is about and it covers an area of . It is also among the oldest known clonal plants. Another giant marine plant of the genus Posidonia, Posidonia oceanica discovered in the Mediterranean near the Balearic Islands, Spain may be the oldest living organism in the world, with an estimated age of 100,000 years. The largest individual flower in the world is Rafflesia arnoldii, while the flowering plant with the largest unbranched inflorescence in the world is Amorphophallus titanum. Both are native to Sumatra in Indonesia. Green algae Green algae are photosynthetic unicellular and multicellular "green plants" that are related to land plants. The thallus of the unicellular mermaid's wineglass, Acetabularia, can grow to several inches (perhaps 0.1 to 0.2 m) in length. The fronds of the similarly unicellular Caulerpa taxifolia can grow up to a foot (0.3 m) long. ==Animals==

'' is potentially the largest animal to have walked the earth. ==Fungi==

''|315x315px 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 of area and possibly weighing as much as 35,000 tons. This organism is estimated to be 2,400 years old. The fungus was written about in the April 2003 issue of the Canadian Journal of Forest Research. 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 stipe, and a pileus up to across. There are many other fungi which produce a larger individual size mushroom. The largest known fruiting body of a fungus is a specimen of Phellinus ellipsoideus (formerly Fomitiporia ellipsoidea) found on Hainan Island. The fruiting body masses up to . Until P. ellipsoideus replaced it, the largest individual fruit body came from Rigidoporus ulmarius. R. ulmarius can grow up to , tall, across, and has a circumference of up to . Lichen Umbilicaria mammulata is among the largest lichens in the world. The thallus of U. mammulata is usually in diameter, but specimens have been known to reach in the Smoky Mountains of Tennessee. The longest lichen is Usnea longissima, which may grow to exceed in length. ==Protists==

'', the largest species of giant kelp|283x283px (Note: the group Protista is not used in current taxonomy.) ===Amoebozoans (Amoebozoa)=== :Among the organisms that are not multicellular, the largest are the slime molds, such as Physarum polycephalum, some of which can reach a diameter over . These organisms are unicellular, but they are multinucleate. ===Euglenozoans (Euglenozoa)=== :Some euglenophytes, such as certain species of Euglena, reach lengths of 400 μm. ===Alveolates (Alveolata)=== :The largest ciliates, such as Spirostomum, can attain a length over . ===Stramenopiles (Stramenopila)=== :The largest stramenopiles are giant kelp from the northwestern Pacific. The floating stem of Macrocystis pyrifera can grow to a height of over . :Macrocystis also qualifies as the largest brown alga, the largest chromist, and the largest protist generally. Heliozoa , the largest known heliozoan is Berkeleyaesol magnus (formerly Raphidiophrys magna): its axopodial sphere can reach a diameter up to 6350 μm (6.35 mm), with a cell body diameter of 1486 μm, a mucilaginous envelope 540 μm thick, and up to 1892 μm long axopodia. ==Bacteria==

'' with a tardigrade for scale. The largest known species of bacterium is named Thiomargarita magnifica, which grows to in length, making it visible to the naked eye and also about five thousand times the size of more typical bacteria. BBC News described it as possessing the "size and shape of a human eyelash." Science published a new paper on the bacterium on June 23, 2022. According to a study coauthored by Jean-Marie Volland, a marine biologist and scientist at California's Laboratory for Research in Complex Systems, and an affiliate at the US Department of Energy Joint Genome Institute, T. magnifica can grow up to 2 centimeters long. • Cyanobacteria :One of the largest "blue green algae" is Lyngbya, whose filamentous cells can be 50 μm wide. == Archaea ==

The largest reported archaea is Spaphylothermus marinus, with a cell diameter of up to 15 micrometres. Although it typically only achieves a diameter of 0.5-1 micrometres, cells with larger diameter may form when high concentrations of yeast extract are present. ==Viruses==

The largest virus on record is Megaklothovirus horridgei, with the length of 3.9 micrometres, comparable to the typical size of a bacterium and large enough to be seen in light microscopes. It was discovered in 2018 (being mistaken for bristles beforehand), having been found on an arrow worm in the genus Spadella. Prior to this discovery, the largest virus was the peculiar virus genus Pandoravirus, which have a size of approximately 1 micrometer and whose genome contains 1,900,000 to 2,500,000 base pairs of DNA. Pandoravirus infects amoebas specifically, however Megaklothovirus infects Spadella arrow worms. ==See also==