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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.
In 2011 a study published in PLoS Biology estimated there to be 8.7 million ± 1.3 million eukaryotic species on Earth. [11] By 2017, most estimates projected there to be around 11 million species or fewer on Earth. [4] A 2017 study estimated there are around at least 1 to 6 billion species, 70-90% of which are bacteria. [4]
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 ...
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.
[192] [193] In Africa, locally abundant species of locusts and termites are a common traditional human food source. [194] Some, especially deep-fried cicadas , are considered to be delicacies . Insects have a high protein content for their mass, and some authors suggest their potential as a major source of protein in human nutrition . [ 195 ]
Between 950,000–1,000,000 of all described animal species are considered insects, so over 50% of all described eukaryotes (1.8 million species) are insects (see illustration). With only 950,000 known non-insects, if the actual total number of insects is 5.5 million, they may represent over 80% of the total, and with only about 20,000 new ...