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  2. Life - Wikipedia

    en.wikipedia.org/wiki/Life

    Life has been studied since ancient times, with theories such as Empedocles's materialism asserting that it was composed of four eternal elements, and Aristotle's hylomorphism asserting that living things have souls and embody both form and matter. Life originated at least 3.5 billion years ago, resulting in a universal common ancestor.

  3. Living systems - Wikipedia

    en.wikipedia.org/wiki/Living_systems

    A presentation on information flow in living systems. Living systems are life forms (or, more colloquially known as living things) treated as a system. They are said to be open self-organizing and said to interact with their environment. These systems are maintained by flows of information, energy and matter. Multiple theories of living systems ...

  4. Cell theory - Wikipedia

    en.wikipedia.org/wiki/Cell_theory

    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

  5. Outline of life forms - Wikipedia

    en.wikipedia.org/wiki/Outline_of_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 . 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 ...

  6. Outline of biology - Wikipedia

    en.wikipedia.org/wiki/Outline_of_biology

    Marine biology – study of ocean ecosystems, plants, animals, and other living beings. Microbiology – study of microscopic organisms (microorganisms) and their interactions with other living things. Bacteriology – study of bacteria; Immunology – study of immune systems in all organisms. Mycology – study of fungi

  7. List of life sciences - Wikipedia

    en.wikipedia.org/wiki/List_of_life_sciences

    Different kinds of living creatures studied in life sciences top: an animal (Goliath beetle) and microorganisms (E. coli bacteria) bottom: a plant (tree fern) and humans Part of a series on Science General History Literature Method Philosophy Branches Formal Natural Physical Life Social Applied In society Communication Community Education Funding Policy Pseudoscience Scientist Science portal ...

  8. Biology - Wikipedia

    en.wikipedia.org/wiki/Biology

    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.

  9. Kingdom (biology) - Wikipedia

    en.wikipedia.org/wiki/Kingdom_(biology)

    The classification of living things into animals and plants is an ancient one. Aristotle (384–322 BC) classified animal species in his History of Animals, while his pupil Theophrastus (c. 371 –c. 287 BC) wrote a parallel work, the Historia Plantarum, on plants. [7]