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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. Biology - Wikipedia

    en.wikipedia.org/wiki/Biology

    Biochemistry is the study of chemical processes within and relating to living organisms. Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including molecular synthesis, modification, mechanisms, and interactions.

  6. Biological roles of the elements - Wikipedia

    en.wikipedia.org/wiki/Biological_roles_of_the...

    Essential for almost all living things; needed for chlorophyll, and is a co-factor for many other enzymes; has multiple medical uses. [11] Large doses can have toxic effects. [11] manganese: 25: 5a: Essential for almost all living things, although in very small amounts; it is a cofactor for many classes of enzymes.

  7. 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]

  8. Domain (biology) - Wikipedia

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

    Carl Linnaeus made the classification "domain" popular in the famous taxonomy system he created in the middle of the eighteenth century. This system was further improved by the studies of Charles Darwin later on but could not classify bacteria easily, as they have very few observable features to compare to the other domains.

  9. Animal - Wikipedia

    en.wikipedia.org/wiki/Animal

    Animals have several characteristics that set them apart from other living things. Animals are eukaryotic and multicellular. [14] Unlike plants and algae, which produce their own nutrients, [15] animals are heterotrophic, [16] [17] feeding on organic material and digesting it internally. [18] With very few exceptions, animals respire aerobically.