Plants are a major group of living things (about 300,000 species), including familiar organisms such as trees, flowers, herbs, and ferns. Aristotle divided all living things between plants, which generally do not move or have sensory organs, and animals. In Linnaeus' system, these became the Kingdoms Vegetabilia (later Plantae) and Animalia. Since then, it has become clear that the Plantae as originally defined included several unrelated groups, and the fungi and several groups of algae were removed to new kingdoms. However, these are still often considered plants in many contexts. Indeed, any attempt to match "plant" with a single taxon is doomed to fail, because plant is a vaguely defined concept unrelated to the presumed phylogenic concepts on which modern taxonomy is based.
The photosynthesis and carbon fixation conducted by land plants and algae are the ultimate source of energy and organic material in nearly all habitats. These processes also radically changed the composition of the Earth's atmosphere, which as a result contains a large proportion of oxygen. Animals and most other organisms are aerobic, relying on oxygen; those that do not are confined to relatively few, anaerobic environments.
Much of human nutrition depends on cereals. Other plants that are eaten include fruits, vegetables, herbs, and spices. Some vascular plants, referred to as trees and shrubs, produce woody stems and are an important source of building material. A number of plants are used decoratively, including a variety of flowers
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