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The cell is the basic structural and functional unit of all forms of life. Every cell consists of cytoplasm enclosed within a membrane; many cells contain organelles, each with a specific function. The term comes from the Latin word cellula meaning 'small room'. Most cells are only visible under a microscope.
Cells are the basic unit of structure in every living thing, and all cells arise from pre-existing cells by division. [ 142 ] [ 143 ] Cell theory was formulated by Henri Dutrochet , Theodor Schwann , Rudolf Virchow and others during the early nineteenth century, and subsequently became widely accepted. [ 144 ]
This was a major advance in the field of biology since little was known about animal structure up to this point compared to plants. From these conclusions about plants and animals, two of the three tenets of cell theory were postulated. 1. All living organisms are composed of one or more cells 2. The cell is the most basic unit of life
Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. [1] [2] All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living and functioning of organisms. [3] Cell biology is the study of the structural and functional ...
In 1838, Schleiden and Schwann began promoting the now universal ideas that (1) the basic unit of organisms is the cell and (2) that individual cells have all the characteristics of life, although they opposed the idea that (3) all cells come from the division of other cells, continuing to support spontaneous generation.
History of life. Origin of life – hierarchy of life – Miller–Urey experiment; Macroevolution: adaptive radiation – convergent evolution – extinction – mass extinction – fossil – taphonomy – geologic time – plate tectonics – continental drift – vicariance – Gondwana – Pangaea – endosymbiosis
A life form (also spelled life-form or lifeform) is an entity that is living, [1] [2] such as plants , animals , and fungi . It is estimated that more than 99% of all species that ever existed on Earth, amounting to over five billion species, [3] are extinct. [4] [5] Earth is the only celestial body known to harbor life forms. No form of ...
Evolution of life with Proline, Glycine, or Ornithine as the basic structure for protein-like polymers would lead to parallel biological worlds. They would have morphologically radically different body plans and genetics from the living organisms of the known biosphere .