The Nitrogen Cycle: Of Microbes and Men
Nitrogen compounds have a very long history, ammonium chloride having been known to herelovstory.com were well known by the Middle Ages. Alchemists knew nitric acid as aqua fortis (strong water), as well as other nitrogen compounds such as ammonium salts and nitrate salts. The mixture of nitric and hydrochloric acids was known as aqua regia (royal water), celebrated for its ability to . Cystic fibrosis (also known as CF or mucoviscidosis) is an autosomal recessive genetic disorder affecting most critically the lungs, and also the pancreas, liver, and intestine.
Ammoniacal nitrogen NH 3 -N is a measure for the amount of ammoniaa toxic pollutant often found in landfill leachate  and in waste products, what is nitrogen used for in humans as sewageliquid manure and other liquid organic waste products.
The values of ammoniacal nitrogen in water how to test blood type for free waste liquids are measured in milligram per liter and are used for specifying water treatment systems and facilities. The ammonium nitrogen value is also used in the context of properly designed landfill systems, where the leachate is being pumped to the surface and treated before it enters the ground water, testing the quality of the water exiting the treatment system.
The term NH 3 -N removal is also commonly used in scientific publications as a short way to depict Ammonia in water, and not the measure of its quantity. Ammonium is an ionized form of ammonia. The chemical structure for ammonia is NH 3. Ammonia is highly soluble in water. Ammonia reacts with water H 2 O and forms the ionized form:.
The reaction is reversible. The percentage of ammonia increases with increasing alkalinity of dissolved ammonium in water. Ammonium ions are formed with increasing acidity of dissolved ammonia in water. Ammonia is what is nitrogen used for in humans to fish and humans.
The toxicity is decreased with lower alkalinity and increases with higher alkalinity as ammonium is converted to ammonia. Molecular nitrogen is the gas form of nitrogen in the atmosphere. The chemical structure for nitrogen gas is N 2. Ammoniums ions are nitrified and are converted by microorganisms into nitrate. Fish and humans are more tolerant of nitrate nitrogen than they are of ammonium nitrogen. In well aerated water, most of the mineral nitrogen is in the form of nitrate. From Wikipedia, the free encyclopedia.
Ammonia can directly poison humans and upset the equilibrium of water systems. Main article: Nitrogen cycle. PMID Tyson, Danielle D. Treadwell and Eric H. Simonne Categories : Ecological data. Hidden categories: Webarchive template wayback links.
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Urea, also known as carbamide, is an organic compound with chemical formula CO(NH 2) herelovstory.com amide has two –NH 2 groups joined by a carbonyl (C=O) functional group.. Urea serves an important role in the metabolism of nitrogen-containing compounds by animals and is the main nitrogen-containing substance in the urine of herelovstory.com is a colorless, odorless solid, highly soluble in water, and. Ammoniacal nitrogen (NH 3-N) is a measure for the amount of ammonia, a toxic pollutant often found in landfill leachate and in waste products, such as sewage, liquid manure and other liquid organic waste products. It can also be used as a measure of the health of water in natural bodies such as rivers or lakes, or in man made water reservoirs. The term is used widely in waste treatment and. Life is a characteristic that distinguishes physical entities that have biological processes, such as signaling and self-sustaining processes, from those that do not, either because such functions have ceased (they have died), or because they never had such functions and are classified as herelovstory.coms forms of life exist, such as plants, animals, fungi, protists, archaea, and bacteria.
Life is a characteristic that distinguishes physical entities that have biological processes , such as signaling and self-sustaining processes, from those that do not, either because such functions have ceased they have died , or because they never had such functions and are classified as inanimate.
Various forms of life exist, such as plants , animals , fungi , protists , archaea , and bacteria. Biology is the science concerned with the study of life. There is currently no consensus regarding the definition of life. One popular definition is that organisms are open systems that maintain homeostasis , are composed of cells , have a life cycle , undergo metabolism , can grow , adapt to their environment, respond to stimuli , reproduce and evolve.
Other definitions sometimes include non-cellular life forms such as viruses and viroids. Abiogenesis is the natural process of life arising from non-living matter, such as simple organic compounds. The prevailing scientific hypothesis is that the transition from non-living to living entities was not a single event, but a gradual process of increasing complexity.
Life on Earth first appeared as early as 4. Complex organic molecules occur in the Solar System and in interstellar space , and these molecules may have provided starting material for the development of life on Earth. Since its primordial beginnings, life on Earth has changed its environment on a geologic time scale , but it has also adapted to survive in most ecosystems and conditions.
Some microorganisms, called extremophiles , thrive in physically or geochemically extreme environments that are detrimental to most other life on Earth. The cell is considered the structural and functional unit of life.
Cells reproduce through a process of cell division , in which the parent cell divides into two or more daughter cells. In the past, there have been many attempts to define what is meant by "life" through obsolete concepts such as odic force , hylomorphism , spontaneous generation and vitalism , that have now been disproved by biological discoveries.
Aristotle is considered to be the first person to classify organisms. Later, Carl Linnaeus introduced his system of binomial nomenclature for the classification of species. Eventually new groups and categories of life were discovered, such as cells and microorganisms, forcing dramatic revisions of the structure of relationships between living organisms.
Though currently only known on Earth , life need not be restricted to it, and many scientists speculate in the existence of extraterrestrial life. Artificial life is a computer simulation or human-made reconstruction of any aspect of life, which is often used to examine systems related to natural life.
Death is the permanent termination of all biological processes which sustain an organism, and as such, is the end of its life. Extinction is the term describing the dying out of a group or taxon , usually a species.
Fossils are the preserved remains or traces of organisms. The definition of life has long been a challenge for scientists and philosophers, with many varied definitions put forward. Since there is no unequivocal definition of life, most current definitions in biology are descriptive.
Life is considered a characteristic of something that preserves, furthers or reinforces its existence in the given environment. This characteristic exhibits all or most of the following traits:       . These complex processes, called physiological functions , have underlying physical and chemical bases, as well as signaling and control mechanisms that are essential to maintaining life.
From a physics perspective, living beings are thermodynamic systems with an organized molecular structure that can reproduce itself and evolve as survival dictates.
Others take a systemic viewpoint that does not necessarily depend on molecular chemistry. One systemic definition of life is that living things are self-organizing and autopoietic self-producing. Variations of this definition include Stuart Kauffman 's definition as an autonomous agent or a multi-agent system capable of reproducing itself or themselves, and of completing at least one thermodynamic work cycle. Whether or not viruses should be considered as alive is controversial.
They are most often considered as just gene coding replicators rather than forms of life. However, viruses do not metabolize and they require a host cell to make new products.
Virus self-assembly within host cells has implications for the study of the origin of life , as it may support the hypothesis that life could have started as self-assembling organic molecules. To reflect the minimum phenomena required, other biological definitions of life have been proposed,  with many of these being based upon chemical systems. Biophysicists have commented that living things function on negative entropy.
Living systems are open self-organizing living things that interact with their environment. These systems are maintained by flows of information, energy , and matter. This system is able to regulate and control metabolism and energy supply and contains at least one subsystem that functions as an information carrier genetic information.
Cells as self-sustaining units are parts of different populations that are involved in the unidirectional and irreversible open-ended process known as evolution. Some scientists have proposed in the last few decades that a general living systems theory is required to explain the nature of life.
Instead of examining phenomena by attempting to break things down into components, a general living systems theory explores phenomena in terms of dynamic patterns of the relationships of organisms with their environment. The idea that the Earth is alive is found in philosophy and religion, but the first scientific discussion of it was by the Scottish scientist James Hutton.
In , he stated that the Earth was a superorganism and that its proper study should be physiology. Hutton is considered the father of geology, but his idea of a living Earth was forgotten in the intense reductionism of the 19th century.
Robert Rosen devoted a large part of his career, from  onwards, to developing a comprehensive theory of life as a self-organizing complex system, "closed to efficient causation"  He defined a system component as "a unit of organization; a part with a function, i. A systems view of life treats environmental fluxes and biological fluxes together as a "reciprocity of influence,"  and a reciprocal relation with environment is arguably as important for understanding life as it is for understanding ecosystems.
As Harold J. Morowitz explains it, life is a property of an ecological system rather than a single organism or species.
Robert Ulanowicz highlights mutualism as the key to understand the systemic, order-generating behavior of life and ecosystems. Complex systems biology CSB is a field of science that studies the emergence of complexity in functional organisms from the viewpoint of dynamic systems theory.
A closely related approach to CSB and systems biology called relational biology is concerned mainly with understanding life processes in terms of the most important relations, and categories of such relations among the essential functional components of organisms; for multicellular organisms, this has been defined as "categorical biology", or a model representation of organisms as a category theory of biological relations, as well as an algebraic topology of the functional organization of living organisms in terms of their dynamic, complex networks of metabolic, genetic, and epigenetic processes and signaling pathways.
It has also been argued that the evolution of order in living systems and certain physical systems obeys a common fundamental principle termed the Darwinian dynamic. The underlying order-generating process was concluded to be basically similar for both types of systems. Another systemic definition called the operator theory proposes that "life is a general term for the presence of the typical closures found in organisms; the typical closures are a membrane and an autocatalytic set in the cell"  and that an organism is any system with an organisation that complies with an operator type that is at least as complex as the cell.
Some of the earliest theories of life were materialist, holding that all that exists is matter, and that life is merely a complex form or arrangement of matter. Empedocles BC argued that everything in the universe is made up of a combination of four eternal "elements" or "roots of all": earth, water, air, and fire. All change is explained by the arrangement and rearrangement of these four elements. The various forms of life are caused by an appropriate mixture of elements.
Democritus BC thought that the essential characteristic of life is having a soul psyche. Like other ancient writers, he was attempting to explain what makes something a living thing. His explanation was that fiery atoms make a soul in exactly the same way atoms and void account for any other thing. He elaborates on fire because of the apparent connection between life and heat, and because fire moves.
Plato's world of eternal and unchanging Forms , imperfectly represented in matter by a divine Artisan , contrasts sharply with the various mechanistic Weltanschauungen , of which atomism was, by the fourth century at least, the most prominent This debate persisted throughout the ancient world. Atomistic mechanism got a shot in the arm from Epicurus The choice seems simple: either show how a structured, regular world could arise out of undirected processes, or inject intelligence into the system.
In the 19th century, the advances in cell theory in biological science encouraged this view. The evolutionary theory of Charles Darwin is a mechanistic explanation for the origin of species by means of natural selection. Hylomorphism is a theory first expressed by the Greek philosopher Aristotle BC. The application of hylomorphism to biology was important to Aristotle, and biology is extensively covered in his extant writings. In this view, everything in the material universe has both matter and form, and the form of a living thing is its soul Greek psyche , Latin anima.
There are three kinds of souls: the vegetative soul of plants, which causes them to grow and decay and nourish themselves, but does not cause motion and sensation; the animal soul , which causes animals to move and feel; and the rational soul , which is the source of consciousness and reasoning, which Aristotle believed is found only in man. Aristotle believed that while matter can exist without form, form cannot exist without matter, and that therefore the soul cannot exist without the body.
This account is consistent with teleological explanations of life, which account for phenomena in terms of purpose or goal-directedness. Thus, the whiteness of the polar bear's coat is explained by its purpose of camouflage. The direction of causality from the future to the past is in contradiction with the scientific evidence for natural selection, which explains the consequence in terms of a prior cause.
Biological features are explained not by looking at future optimal results, but by looking at the past evolutionary history of a species, which led to the natural selection of the features in question. Spontaneous generation was the belief that living organisms can form without descent from similar organisms.
Typically, the idea was that certain forms such as fleas could arise from inanimate matter such as dust or the supposed seasonal generation of mice and insects from mud or garbage. The theory of spontaneous generation was proposed by Aristotle ,  who compiled and expanded the work of prior natural philosophers and the various ancient explanations of the appearance of organisms; it held sway for two millennia.
It was decisively dispelled by the experiments of Louis Pasteur in , who expanded upon the investigations of predecessors such as Francesco Redi. Vitalism is the belief that the life-principle is non-material. This originated with Georg Ernst Stahl 17th century , and remained popular until the middle of the 19th century.
It is of historical significance because for the first time an organic compound was produced in inorganic reactions. During the s, Hermann von Helmholtz , anticipated by Julius Robert von Mayer , demonstrated that no energy is lost in muscle movement, suggesting that there were no "vital forces" necessary to move a muscle.
The age of the Earth is about 4. Although the number of Earth's catalogued species of lifeforms is between 1. Estimates range from 8 million to million,   with a more narrow range between 10 and 14 million,  but it may be as high as 1 trillion with only one-thousandth of one percent of the species described according to studies realized in May All known life forms share fundamental molecular mechanisms, reflecting their common descent ; based on these observations, hypotheses on the origin of life attempt to find a mechanism explaining the formation of a universal common ancestor , from simple organic molecules via pre-cellular life to protocells and metabolism.
Models have been divided into "genes-first" and "metabolism-first" categories, but a recent trend is the emergence of hybrid models that combine both categories. There is no current scientific consensus as to how life originated. However, most accepted scientific models build on the Miller—Urey experiment and the work of Sidney Fox , which show that conditions on the primitive Earth favored chemical reactions that synthesize amino acids and other organic compounds from inorganic precursors,  and phospholipids spontaneously form lipid bilayers , the basic structure of a cell membrane.
Living organisms synthesize proteins , which are polymers of amino acids using instructions encoded by deoxyribonucleic acid DNA. Protein synthesis entails intermediary ribonucleic acid RNA polymers. One possibility for how life began is that genes originated first, followed by proteins;  the alternative being that proteins came first and then genes. However, because genes and proteins are both required to produce the other, the problem of considering which came first is like that of the chicken or the egg.