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For levels larger than Biosphere or Ecosphere, see Earth's location in the Universe More complex schemes incorporate many more levels. For example, a molecule can be viewed as a grouping of elements , and an atom can be further divided into subatomic particles (these levels are outside the scope of biological organisation).
Forests harbour most of Earth's terrestrial biodiversity. The conservation of the world's biodiversity is thus utterly dependent on the way in which we interact with and use the world's forests. [78] A new method used in 2011, put the total number of species on Earth at 8.7 million, of which 2.1 million were estimated to live in the ocean. [79]
A trophic level (from Greek troph, τροφή, trophē, meaning "food" or "feeding") is "a group of organisms acquiring a considerable majority of its energy from the lower adjacent level (according to ecological pyramids) nearer the abiotic source."
The history of life on Earth traces how organisms have evolved from the earliest emergence of life to present day. Earth formed about 4.5 billion years ago and all life on Earth, both living and extinct, descended from a last universal common ancestor that lived about 3.5 billion years ago .
Differing levels of biological organisation give rise to potentially different understandings of the nature of organisms. A unicellular organism is a microorganism such as a protist , bacterium , or archaean , composed of a single cell , which may contain functional structures called organelles . [ 22 ]
Halophiles (organisms that thrive in highly salty environments) and hyperthermophiles (organisms that thrive in extremely hot environments) are examples of Archaea. [1] Archaea are relatively small. They range from 0.1 μm to 15 μm diameter and up to 200 μm long, about the size of bacteria and the mitochondria found in eukaryotic cells.
For example, ecosystems can be quite different if situated in a small depression on the landscape, versus one present on an adjacent steep hillside. [ 9 ] : 39 [ 10 ] : 66 Other external factors that play an important role in ecosystem functioning include time and potential biota , the organisms that are present in a region and could ...
Like all other organisms, bacteria contain ribosomes for the production of proteins, but the structure of the bacterial ribosome is different from that of eukaryotes and archaea. [ 69 ] Some bacteria produce intracellular nutrient storage granules, such as glycogen , [ 70 ] polyphosphate , [ 71 ] sulfur [ 72 ] or polyhydroxyalkanoates . [ 73 ]