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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]
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 .
The Catalogue of Life (CoL) is an online database that provides an index of known species of animals, plants, fungi, and microorganisms.It was created in 2001 as a partnership between the global Species 2000 and the American Integrated Taxonomic Information System.
The list of organisms by chromosome count describes ploidy or numbers of chromosomes in the cells of various plants, animals, protists, and other living organisms.This number, along with the visual appearance of the chromosome, is known as the karyotype, [1] [2] [3] and can be found by looking at the chromosomes through a microscope.
An organism is any living thing that functions as an individual. [1] Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have been proposed to define what an organism is.
Animal corpses, like this African buffalo, are recycled by the ecosystem, providing energy and nutrients for living organisms. Death is the termination of all vital functions or life processes in an organism or cell. [31] [32] One of the challenges in defining death is in distinguishing it from life.
[51] [52] Proteins are vital parts of living organisms, as they are the main components of the physiological metabolic pathways of cells. The proteome is the entire set of proteins, [53] produced or modified by an organism or system. This varies with time and distinct requirements, or stresses, that a cell or organism undergoes.
In biological taxonomy, a domain (/ d ə ˈ m eɪ n / or / d oʊ ˈ m eɪ n /) (Latin: regio [1]), also dominion, [2] superkingdom, realm, or empire, is the highest taxonomic rank of all organisms taken together. It was introduced in the three-domain system of taxonomy devised by Carl Woese, Otto Kandler and Mark Wheelis in 1990. [1]