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The term "organism" (from the Ancient Greek ὀργανισμός, derived from órganon, meaning ' instrument, implement, tool ', ' organ of sense ', or ' apprehension ') [2] [3] first appeared in the English language in the 1660s with the now-obsolete meaning of an organic structure or organization. [3]
The total number of undescribed organisms is unknown, but marine microbial species alone could number 20,000,000. [12] For this reason, the number of quantified species will always lag behind the number of described species, and species contained in these lists tend to be on the K side of the r/K selection continuum.
Stentor coeruleus, used in molecular biology (its genome has been sequenced), [5] and is studied as a model of single-cell regeneration.; Dictyostelium discoideum, used in molecular biology and genetics (its genome has been sequenced), and is studied as an example of cell communication, differentiation, and programmed cell death.
For example, zoology is the study of animals, while botany is the study of plants. Other life sciences focus on aspects common to all or many life forms, such as anatomy and genetics . Some focus on the micro-scale (e.g. molecular biology , biochemistry ) other on larger scales (e.g. cytology , immunology , ethology , pharmacy, ecology).
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.
In 1937 Édouard Chatton introduced the terms "prokaryote" and "eukaryote" to differentiate these organisms. [9] In 1938, Herbert F. Copeland proposed a four-kingdom classification by creating the novel Kingdom Monera of prokaryotic organisms; as a revised phylum Monera of the Protista, it included organisms now classified as Bacteria and Archaea.
Halophiles (organisms that thrive in highly salty environments) and hyperthermophiles (organisms that thrive in extremely hot environments) are examples of Archaea. [1] Archaea evolved many cell sizes, but all are relatively small. Their size ranges from 0.1 μm to 15 μm diameter and up to 200 μm long.
The following outline is provided as an overview of and topical guide to life forms: . A life form (also spelled life-form or lifeform) is an entity that is living, [1] [2] such as plants (), animals (), and fungi ().