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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 .
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]
The human population exploits a large number of other animal species for food, both of domesticated livestock species in animal husbandry and, mainly at sea, by hunting wild species. [160] [161] Marine fish of many species are caught commercially for food. A smaller number of species are farmed commercially.
Many animals on this second table are at least somewhat altered from wild-type animals due to their extensive interactions with humans, albeit not to the point that they are regarded as distinct forms (therefore, no separate wild ancestors are noted) or would be unable to survive if reintroduced to the wild.
The following is a list of the classes in each phylum of the kingdom Animalia. There are 107 classes of animals in 33 phyla in this list. However, different sources give different numbers of classes and phyla. For example, Protura, Diplura, and Collembola are often considered to be the three orders in the class Entognatha. This list should by ...
Animals are a major group of organisms, classified as the kingdom Animalia. This category includes animals, their study , and their classification . Subcategories
Humans have introduced more different species to new environments than any single document can record. This list is generally for established species with truly wild populations— not kept domestically, that have been seen numerous times, and have breeding populations. While most introduced species can cause a negative impact to new ...
Holozoa (from Ancient Greek ὅλος (holos) 'whole' and ζῷον (zoion) 'animal') is a clade of organisms that includes animals and their closest single-celled relatives, but excludes fungi and all other organisms. Together they amount to more than 1.5 million species of purely heterotrophic organisms, including around 300 unicellular species