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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 ...
The scientific use of life-form schemes emphasizes plant function in the ecosystem and that the same function or "adaptedness" to the environment may be achieved in a number of ways, i.e. plant species that are closely related phylogenetically may have widely different life-form, for example Adoxa moschatellina and Sambucus nigra are from the ...
Raunkiær's life-form scheme has subsequently been revised and modified by various authors, [6] [7] [8] but the main structure has survived. Raunkiær's life-form system may be useful in researching the transformations of biotas and the genesis of some groups of phytophagous animals.
Carbon-based photosynthesis life caused a rise in oxygen on Earth. This increase of oxygen helped plate tectonics form the first continents. [10] It is frequently assumed in astrobiology that if life exists elsewhere in the Universe, it will also be carbon-based. [11] [12] Critics, like Carl Sagan in 1973, refer to this assumption as carbon ...
For example, zoology is the study of animals, while botany is the study of plants. Other life sciences focus on aspects common to all or many life forms, such as anatomy and genetics . Some focus on the micro-scale (e.g. molecular biology , biochemistry ) other on larger scales (e.g. cytology , immunology , ethology , pharmacy, ecology).
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.
A team of international researchers has challenged the long-held belief that complex life forms first emerged on Earth 635 million years ago, presenting findings that show life may have existed ...
False-color Cassini radar mosaic of Titan's north polar region; the blue areas are lakes of liquid hydrocarbons. "The existence of lakes of liquid hydrocarbons on Titan opens up the possibility for solvents and energy sources that are alternatives to those in our biosphere and that might support novel life forms altogether different from those on Earth."—NASA Astrobiology Roadmap 2008 [1]