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More than 99 percent of all species, amounting to over five billion species, [7] that ever lived on Earth are estimated to be extinct. [8] [9] Estimates on the number of Earth's current species range from 10 million to 14 million, [10] of which about 1.2 million have been documented and over 86 percent have not yet been described. [11]
Most groups are primarily aquatic (two notable exceptions being woodlice and hexapods, which are both purely terrestrial) and are characterized by having biramous appendages. The most abundant group of pancrustaceans are the terrestrial hexapods, which comprise insects, diplurans, springtails, and proturans, with six thoracic legs.
Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million in total. Animals range in size from 8.5 millionths of a metre to 33.6 metres (110 ft) long and have complex interactions with each other and their environments, forming intricate food webs.
Lists only exist for some orders; for example, the most diverse order - rodents - is missing. Much of the data in these lists were created by the International Union for Conservation of Nature (IUCN) Global Mammal Assessment Team, which consists of 1700 mammalogists from over 130 countries. They recognize 5488 species in the class. [1] [2]
Insects make up the vast majority of animal species. [14]Chapman, 2005 and 2009 [9] has attempted to compile perhaps the most comprehensive recent statistics on numbers of extant species, drawing on a range of published and unpublished sources, and has come up with a figure of approximately 1.9 million estimated described taxa, as against possibly a total of between 11 and 12 million ...
One of the 25 most endangered primates. [7] Delacour's langur: Trachypithecus delacouri: 234–275 [8] CR [8] [8] The population of the species has radically decreased over the past decade. [8] Silky sifaka: Propithecus candidus: 250 [9] CR [9] [9] Estimate is believed to be a maximum. [9] Tonkin snub-nosed monkey: Rhinopithecus avunculus: 250 ...
These abundant species are often generalists, with many rare species being specialists. [4] High density of a species in multiple localities will usually lead to it being relatively abundant over all in an ecosystem. [4] Therefore, high local abundance can be directly linked to high regional distribution. Species with high abundance are likely ...
Life arose from the Earth's first ocean, which formed some 3.8 billion years ago. [33] Since then, water continues to be the most abundant molecule in every organism. Water is important to life because it is an effective solvent, capable of dissolving solutes such as sodium and chloride ions or other small molecules to form an aqueous solution.