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Life forms live in every part of the Earth's biosphere, including soil, hot springs, inside rocks at least 19 km (12 mi) deep underground, and at least 64 km (40 mi) high in the atmosphere. [ 26 ] [ 27 ] [ 28 ] Marine life under many forms has been found in the deepest reaches of the world ocean while much of the deep sea remains to be explored.
Many philosophical definitions of living systems have been proposed, such as self-organizing systems. Viruses in particular make definition difficult as they replicate only in host cells. Life exists all over the Earth in air, water, and soil, with many ecosystems forming the biosphere. Some of these are harsh environments occupied only by ...
The English language uses many Greek and Latin roots, stems, and prefixes. These roots are listed alphabetically on three pages: Greek and Latin roots from A to G; Greek and Latin roots from H to O; Greek and Latin roots from P to Z. Some of those used in medicine and medical technology are listed in the List of medical roots, suffixes and ...
The origin of life on Earth is not well understood, but it is known to have occurred at least 3.5 billion years ago, [65] [66] [67] during the hadean or archean eons on a primordial Earth that had a substantially different environment than is found at present. [68] These life forms possessed the basic traits of self-replication and inheritable ...
All life on Earth can be traced back to a Last Universal Common Ancestor, or LUCA. A new study suggests that this organism likely lived on Earth only 400 million years after its formation.
Geography is an all-encompassing discipline that seeks an understanding of Earth and its human and natural complexities—not merely where objects are, but also how they have changed and come to be. While geography is specific to Earth, many concepts can be applied more broadly to other celestial bodies in the field of planetary science. [2]
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.
The idea of a tree of life arose from ancient notions of a ladder-like progression from lower into higher forms of life (such as in the Great Chain of Being).Early representations of "branching" phylogenetic trees include a "paleontological chart" showing the geological relationships among plants and animals in the book Elementary Geology, by Edward Hitchcock (first edition: 1840).