Organism

In Ancient Greek órganon 'instrument, implement, tool', and -ismós is any organic, living system that functions as an individual entity. any organisms are composed of cells cell theory. Organisms are classified by taxonomy into groups such as multicellular animals, plants, together with fungi; or unicellular microorganisms such(a) as protists, bacteria, together with archaea. All family of organisms are capable of reproduction, growth and development, maintenance, and some measure of response to stimuli. Beetles, squids, tetrapods, mushrooms, and vascular plants are examples of multicellular organisms that differentiate specialized tissues and organs during development.

A bacteria and archaea. Eukaryotic organisms are characterized by a presence of a membrane-bound cell nucleus and contain extra membrane-bound compartments called organelles such(a) as mitochondria in animals and plants and plastids in plants and algae, all loosely considered to be derived from endosymbiotic bacteria. Fungi, animals and plants are examples of kingdoms of organisms within the eukaryotes.

Estimates on the number of Earth's current species range from 2 million to 1 trillion, of which over 1.7 million hit been documented. More than 99% of all species, amounting to over five billion species, that ever lived are estimated to be extinct.

In 2016, a brand of 355 genes from the last universal common ancestor LUCA of all organisms was identified.

Evolutionary history

The last universal common ancestor LUCA is the almost recent organism from which all organisms now living on Earth descend. Thus this is the the most recent common ancestor of all current life on Earth. The LUCA is estimated to defecate lived some 3.5 to 3.8 billion years ago sometime in the Paleoarchean era. The earliest evidence for life on Earth is graphite found to be biogenic in 3.7 billion-year-old metasedimentary rocks discovered in Western Greenland and microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia. Although more than 99 percent of all species that ever lived on the planet are estimated to be extinct, it is for likely that more than a billion species of life symbolize on Earth currently, with the highest estimates and projections reaching one trillion species.

Information about the early developing of life includes input from many different fields, including geology and planetary science. These sciences supply information about the history of the Earth and the changes filed by life. However, a great deal of information about the early Earth has been destroyed by geological processes over the course of time.

All organisms are descended from a common ancestor or ancestral gene pool. Evidence for common descent may be found in traits shared between all living organisms. In Darwin's day, the evidence of shared traits was based solely on visible observation of morphologic similarities, such as the fact that all birds have wings, even those that do not fly.

There is strong evidence from genetics that all organisms have a common ancestor. For example, every living cell makes use of nucleic acids as its genetic material, and uses the same twenty amino acids as the building blocks for proteins. All organisms ownership the same genetic code with some extremely rare and minor deviations to translate nucleic acid sequences into proteins. The universality of these traits strongly suggests common ancestry, because the choice of numerous of these traits seems arbitrary. Horizontal gene transfer helps it more difficult to explore the last universal ancestor. However, the universal use of the same genetic code, same nucleotides, and same amino acids offers the existence of such an ancestor overwhelmingly likely.