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Classis 14. Didynamia: flowers with 4 stamens, 2 long and 2 short Gymnospermia [8] Angiospermia [9] Classis 15. Tetradynamia: flowers with 6 stamens, 4 long and 2 short [10] Classis 16. Monadelphia; flowers with the anthers separate, but the filaments united, at least at the base Pentandria [11] Decandria [12] Polyandria [13] Classis 17.
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]
He divided all living things into two groups: plants and animals. [36] Some of his groups of animals, such as Anhaima (animals without blood, translated as invertebrates) and Enhaima (animals with blood, roughly the vertebrates), as well as groups like the sharks and cetaceans, are commonly used. [39] [40] [41]
Systematics is the study of the diversification of living forms, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees (synonyms: phylogenetic trees, phylogenies).
In biology, taxonomic rank (which some authors prefer to call nomenclatural rank [1] because ranking is part of nomenclature rather than taxonomy proper, according to some definitions of these terms) is the relative or absolute level of a group of organisms (a taxon) in a hierarchy that reflects evolutionary relationships.
The term phylum was coined in 1866 by Ernst Haeckel from the Greek phylon (φῦλον, "race, stock"), related to phyle (φυλή, "tribe, clan"). [4] [5] Haeckel noted that species constantly evolved into new species that seemed to retain few consistent features among themselves and therefore few features that distinguished them as a group ("a self-contained unity"): "perhaps such a real and ...
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 ...
An order can also be defined as a group of related families. What does and does not belong to each order is determined by a taxonomist , as is whether a particular order should be recognized at all. Often there is no exact agreement, with different taxonomists each taking a different position.