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The definition of life has long been a challenge for scientists and philosophers. [ 2 ] [ 3 ] [ 4 ] This is partially because life is a process, not a substance. [ 5 ] [ 6 ] [ 7 ] This is complicated by a lack of knowledge of the characteristics of living entities, if any, that may have developed outside Earth.
Earth system science – Scientific study of the Earth's spheres and their natural integrated systems; Extraterrestrial life – Life that does not originate on Earth; Information metabolism – Psychological theory of interaction between biological organisms and their environment; Organism – Individual living life form
Although there is no universal agreement on the definition of life, scientists generally accept that the biological manifestation of life is characterized by organization, metabolism, growth, adaptation, response to stimuli, and reproduction. [48] Life may also be said to be simply the characteristic state of organisms.
Earth science generally recognizes four spheres, the lithosphere, the hydrosphere, the atmosphere and the biosphere [3] as correspondent to rocks, water, air and life respectively. Some scientists include as part of the spheres of the Earth, the cryosphere (corresponding to ice ) as a distinct portion of the hydrosphere, as well as the ...
Biologists can study life at multiple levels of organization, [1] from the molecular biology of a cell to the anatomy and physiology of plants and animals, and the evolution of populations. [1] [6] Hence, there are multiple subdisciplines within biology, each defined by the nature of their research questions and the tools that they use.
Ecology addresses the full scale of life, from tiny bacteria to processes that span the entire planet. Ecologists study many diverse and complex relations among species, such as predation and pollination. The diversity of life is organized into different habitats, from terrestrial to aquatic ecosystems.
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Science is a systematic discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe. [1] [2] Modern science is typically divided into two or three major branches: [3] the natural sciences (e.g., physics, chemistry, and biology), which study the physical world; and the behavioural sciences (e.g., economics, psychology, and sociology ...