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{{BioPsy}}
 
{{PsyPerspective}}
 
''Biology'' is the branch of [[science]] dealing with the study of [[life]]. It is concerned with the characteristics, [[scientific classification|classification]], and [[behavior]]s of [[organism]]s, how [[species]] come into existence, and the interactions they have with each other and with the [[natural environment|environment]]. Biology encompasses a broad spectrum of academic fields that are often viewed as independent disciplines. However, together they address phenomena related to living organisms (biological phenomena) over a wide range of scales, from [[biochemistry]] to [[ecology]].
 
 
<div class="thumb tright" style="background-color: #f9f9f9; border: 1px solid #CCCCCC; margin:0.5em;">
 
{| border="0" cellpadding="10" cellspacing="0" style="font-size: 85%; border: 1px solid #CCCCCC; margin: 0.3em;"
 
|valign="top"|[[Image:EscherichiaColi NIAID.jpg|90px|''Escherichia coli'']]
 
|valign="top"|[[Image:Tree_Fern.jpg|90px|Tree fern]]
 
|-
 
|valign="bottom"|[[Image:Goliath_beetle.jpg|90px|Goliath beetle]]
 
|valign="bottom"|[[Image:Thompson's_Gazelle.jpeg|90px|Gazelle]]
 
|}
 
<div style="border: none; width:200px;"><div class="thumbcaption">Biology studies the variety of life ''(clockwise from top-left)'' ''[[E. coli]]'', tree [[fern]], [[gazelle]], Goliath [[beetle]]</div></div></div>
 
 
At the organism level, biology has explained phenomena such as [[childbirth|birth]], [[growth]], [[ageing]], [[death]] and [[decomposition|decay]] of living organisms, similarities between the offsprings and parents ([[heredity]]) and flowering of plants have puzzled humanity ever since antiquity. Other phenomena, such as [[lactation]], [[metamorphosis]], [[Egg (biology)|egg-hatching]], [[healing]], and [[tropism]] have been addressed. On a wider scale of time and space, biologists have studied [[domestication]] of animals and plants, the wide variety of living organisms ([[biodiversity]]), changes in living organisms through ages ([[evolution]]), [[extinction]], [[speciation]], [[social behaviour]] among animals, etc.
 
 
While [[botany]] encompasses the study of plants, [[zoology]] is the branch of science that is concerned about the study of animals and [[anthropology]] is the branch of biology to study human beings. However, at the [[molecule|molecular]] scale, life is studied in the disciplines of [[molecular biology]], [[biochemistry]], and [[molecular genetics]]. At the next level of the [[cell (biology)|cell]], it is studied in [[cell biology]], and at [[multicellular]] scales, it is examined in [[physiology]], [[anatomy]], and [[histology]]. [[Developmental biology]] studies life at the level of an individual organism's development or [[ontogeny]]. Moving up the scale towards more than one organism, [[genetics]] considers how [[heredity]] works between parent and offspring. [[Ethology]] considers group behavior of more than one individual. [[Population genetics]] looks at the level of an entire [[population]], and [[systematics]] considers the multi-species scale of [[lineage]]s. Interdependent populations and their [[Habitat (ecology)|habitats]] are examined in [[ecology]] and [[evolutionary biology]]. A speculative new field is [[astrobiology]] (or xenobiology), which examines the possibility of life beyond the Earth.
 
 
==Principles of biology==
 
Unlike [[physics]], biology does not usually describe systems in terms of objects which obey immutable physical laws described by [[mathematics]]. Nevertheless, the biological sciences are characterized and unified by several major underlying principles and concepts: universality, evolution, diversity, continuity, genetics, homeostasis, and interactions.
 
 
=== Universality: Biochemistry, cells, and the genetic code ===
 
[[Image:DNA-structure-and-bases.png|thumb|Schematic representation of [[DNA]], the primary [[genetic material]].]]
 
 
''Main article:'' [[Life]]
 
 
The most salient example of biological universality is that all
 
living things share a common [[carbon]]-[[Carbon-based|based]] [[biochemistry]] and in particular pass on their [[heredity|characteristics]] via [[genetic material]], which is based on [[nucleic acid]]s such as [[DNA]] and which uses a common [[genetic code]] with only minor variations.
 
 
Another universal principle is that all [[organism]]s (that is, all forms of life on Earth except for [[virus]]es) are made of [[cell (biology)|cell]]s. Similarly, all organisms share common developmental processes. For example, in most [[metazoan]] organisms, the basic stages of early [[embryo|embryonic]] development share similar morphological characteristics and include similar [[gene]]s.
 
 
=== Evolution: The central principle of biology ===
 
''Main article:'' [[Evolution]]
 
 
The central organizing concept in biology is that all life has a common origin and has changed and developed through the process of [[evolution]] (see [[Common descent]]). This has led to the striking similarity of units and processes discussed in the previous section. [[Charles Darwin]] established evolution as a viable theory by articulating its driving force, [[natural selection]] ([[Alfred Russell Wallace]] is recognized as the co-discoverer of this concept). [[Genetic drift]] was embraced as an additional mechanism of evolutionary development in the [[modern synthesis]] of the theory.
 
 
The evolutionary history of a [[species]]&mdash; which describes the characteristics of the various species from which it descended&mdash; together with its genealogical relationship to every other species is called its [[phylogeny]]. Widely varied approaches to biology generate information about phylogeny. These include the comparisons of [[DNA sequence]]s conducted within [[molecular biology]] or [[genomics]], and comparisons of [[fossil]]s or other records of ancient organisms in [[paleontology]]. Biologists organize and analyze evolutionary relationships through various methods, including [[phylogenetics]], [[phenetics]], and [[cladistics]] (The major events in the evolution of life, as biologists currently understand them, are summarized on this [[evolutionary timeline]]).
 
 
=== Diversity: The variety of living organisms ===
 
[[image:PhylogeneticTree.jpg|thumb|340px|A [[phylogenetic tree]] of [[evolutionary tree|all living things]], based on [[rRNA]] [[gene]] data, showing the separation of the three domains [[bacterium|bacteria]], [[archaea]], and [[eukaryote]]s as described initially by [[Carl Woese]]. Trees constructed with other genes are generally similar, although they may place some early-branching groups very differently, presumably owing to rapid rRNA evolution. The exact relationships of the three domains are still being debated.]]
 
 
Despite its underlying unity, life exhibits an astonishingly wide diversity in [[Morphology (biology)|morphology]], [[behavior]], and [[life history|life histories]]. In order to grapple with this diversity, biologists attempt to classify all living things. Scientific classification seeks to reflect the evolutionary trees ([[phylogenetic tree]]s) of the organism being classified. Classification is the province of the disciplines of [[systematics]] and [[taxonomy]]. Taxonomy places organisms in groups called [[taxa]], while systematics seeks to define their relationships with each other. This clasification technique has evolved to reflect advances in [[cladistics]] and [[genetics]], shifting the focus from physical similarities and shared characteristics to [[phylogenetics]].
 
 
Traditionally, living things have been divided into five kingdoms:
 
 
:[[Monera]] -- [[Protist]]a -- [[Fungi]] -- [[Plant|Plantae]] -- [[Animal|Animalia]]
 
 
However, many scientists now consider this five-kingdom system to be outdated. Modern alternative classification systems generally begin with the [[three-domain system]]:
 
 
:[[Archaea]] (originally Archaebacteria) -- [[Bacterium|Bacteria]] (originally Eubacteria) -- [[Eukaryote|Eukaryota]]
 
 
These domains reflect whether the cells have nuclei or not, as well as differences in the cell exteriors.
 
 
Further, each kingdom is broken down continuously until each species is seperately classified. The order is 1)Kingdom, 2)Phylum, 3)Class, 4)Order, 5)Family, 6)Genus, 7)Species. The scientific name of an organism is obtained from its Genus and Species. For example, humans would be listed as ''Homo sapien''. Homo would be the Genus and Sapien is the species. Whenever writing the scientific name of an organism it is proper to capitalize the first letter in the genus and all of the species is lowercase; in addition the entire term would be put in italics. The term used for classification is called Taxonomy.
 
 
There is also a series of intracellular [[parasite]]s that are progressively "less alive" in terms of [[metabolism|metabolic]] activity:
 
 
:[[virus (biology)|Viruses]] -- [[Viroid]]s -- [[Prion]]s
 
 
===Continuity: The common descent of life===
 
''Main article:'' [[Common descent]]
 
 
Up into the [[19th century]], it was commonly believed that life forms could appear spontaneously under certain conditions (see [[abiogenesis]]). This misconception was challenged by [[William Harvey]]'s diction that "all life [is] from [an] egg" (from the [[Latin]] "[[Omne vivum ex ovo]]"), a foundational concept of modern biology. It simply means that there is an unbroken continuity of life from its initial origin to the present time.
 
 
A group of organisms is said to share a common descent if they share a common [[ancestor]]. All [[organism]]s on the [[Earth]] have been and are descended from a common ancestor or an ancestral [[gene pool]]. This last universal common ancestor of all organisms is believed to have appeared about [[Timeline of evolution|3.5 billion years ago]]. Biologists generally regard the universality of the [[genetic code]] as definitive evidence in favor of the theory of universal common descent (UCD) for all [[bacterium|bacteria]], [[archaea]], and [[eukaryote]]s (see: [[origin of life]]).
 
 
===Homeostasis: Adapting to change ===
 
<!--[[Image:Lac_operon.png|thumb|left|250px|An example of [[homeostasis]]: the [[Lac operon]] is mechanism of [[gene regulation]] which prevents the build-up of [[lactose]].]] in the process of checking this is actually homeostatic-->
 
''Main article:'' [[Homeostasis]]
 
 
Homeostasis is the ability of an [[open system]] to regulate its internal environment to maintain a stable condition by means of multiple [[dynamic equilibrium]] adjustments controlled by interrelated regulation mechanisms. All living [[organism]]s, whether [[unicellular]] or [[multicellular]], exhibit homeostasis. Homeostasis manifests itself at the cellular level through the maintenance of a stable internal acidity ([[pH]]); at the organismic level, [[warm-blooded]] animals maintain a constant internal body temperature; and at the level of the [[ecosystem]], as when atmospheric [[carbon dioxide]] levels rise and [[plant]]s are theoretically able to grow healthier and remove more of the gas from the atmosphere. [[Biological tissue|Tissue]]s and [[organ (biology)|organ]]s can also maintain homeostasis.
 
 
===Interactions: Groups and environments===
 
[[image:Common_clownfish.jpg|thumb|250px|right|Mutual [[symbiosis]] between [[clownfish]] of the genus [[Amphiprion]] that dwell among the tentacles of tropical [[sea anemone]]s. The territorial fish protects the anemone from anemone-eating fish, and in turn the stinging tentacles of the anemone protects the clown fish from its predators]]
 
 
Every living thing interacts with other organisms and its [[natural environment|environment]]. One reason that biological systems can be difficult to study is that so many different interactions with other organisms and the environment are possible, even on the smallest of scales. A microscopic [[bacterium]] responding to a local sugar gradient is responding to its environment as much as a [[lion]] is responding to its environment when it searches for food in the [[Africa]]n [[Savanna|savannah]]. For any given species, [[behavior]]s can be [[co-operation|co-operative]], [[aggression|aggressive]], [[parasite|parasitic]] or [[symbiosis|symbiotic]]. Matters become more complex when two or more different species interact in an [[ecosystem]]. Studies of this type are the province of [[ecology]].
 
 
==Scope of biology==
 
''Main article:'' [[List of biology disciplines]]
 
 
Biology has become such a vast research enterprise that it is not generally regarded as a single discipline, but as a number of clustered sub-disciplines. This article considers four broad groupings. The first group consists of those disciplines that study the basic structures of living systems: [[cell (biology)|cell]]s, [[gene]]s etc.; the second group considers the operation of these structures at the level of tissues, organs, and bodies; the third group considers organisms and their histories; the final constellation of disciplines focuses on their interactions. It is important to note, however, that these boundaries, groupings, and descriptions are a simplified characterization of biological research. In reality, the boundaries between disciplines are fluid, and most disciplines frequently borrow techniques from each other. For example, evolutionary biology leans heavily on techniques from molecular biology to determine [[DNA sequence]]s, which assist in understanding the genetic variation of a population; and physiology borrows extensively from cell biology in describing the function of organ systems.
 
 
===Structure of life===
 
[[image:biological_cell.png|thumb|300px|Schematic of typical animal [[cell (biology)|cell]] depicting the various [[organelle]]s and structures]]
 
 
''Main articles:'' [[Molecular biology]], [[Cell biology]], [[Genetics]], [[Developmental biology]]
 
 
[[Molecular biology]] is the study of biology at a [[molecular]] level. This field overlaps with other areas of biology, particularly with [[genetics]] and [[biochemistry]]. Molecular biology chiefly concerns itself with understanding the interactions between the various systems of a cell, including the interrelationship of DNA, RNA, and protein synthesis and learning how these interactions are regulated.
 
 
[[Cell biology]] studies the [[physiology|physiological]] properties of [[cell (biology)|cell]]s, as well as their [[behavior]]s, interactions, and [[natural environment|environment]]. This is done both on a [[microscope|microscopic]] and [[molecule|molecular]] level. Cell biology researches both single-celled organisms like [[bacterium|bacteria]] and specialized cells in multicellular organisms like [[human]]s.
 
 
Understanding cell composition and how they function is fundamental to all of the biological sciences. Appreciating the similarities and differences between cell types is particularly important in the fields of cell and [[molecular biology]]. These fundamental similarities and differences provide a unifying theme, allowing the principles learned from studying one cell type to be extrapolated and generalized to other cell types.
 
 
[[Genetics]] is the [[science]] of [[gene]]s, [[heredity]], and the [[variation]] of [[organism]]s. In modern research, genetics provides important tools in the investigation of the function of a particular gene, or the analysis of [[genetic interaction]]s. Within [[organism]]s, genetic information generally is carried in [[chromosome]]s, where it is represented in the [[DNA sequence|chemical structure]] of particular [[DNA]] [[molecule]]s.
 
 
[[Gene]]s encode the information necessary for synthesizing proteins, which in turn play a large role in influencing (though, in many instances, not completely determining) the final [[phenotype]] of the organism.
 
 
Developmental biology studies the process by which organisms grow and develop. Originating in [[embryology]], modern developmental biology studies the genetic control of [[cell growth]], [[cellular differentiation|differentiation]], and "[[morphogenesis]]," which is the process that gives rise to [[biological tissue|tissue]]s, [[organ (anatomy)|organ]]s, and [[anatomy]].
 
[[Model organism]]s for developmental biology include the round worm ''[[Caenorhabditis elegans]]'', the fruit fly ''[[Drosophila melanogaster]]'', the zebrafish ''[[Brachydanio rerio]]'', the mouse ''[[Mus musculus]]'', and the weed ''[[Arabidopsis thaliana]]''.
 
 
===Physiology of organisms===
 
''Main articles:'' '''[[Physiology]]''', [[Anatomy]]
 
 
Physiology studies the mechanical, physical, and biochemical processes of living organisms by attempting to understand how all of the structures function as a whole. The theme of "structure to function" is central to biology. Physiological studies have traditionally been divided into [[plant physiology]] and [[animal physiology]], but the principles of physiology are universal, no matter what particular [[organism]] is being studied. For example, what is learned about the physiology of [[yeast]] cells can also apply to [[human]] cells. The field of animal physiology extends the tools and methods of [[human physiology]] to non-human [[species]]. Plant physiology also borrows techniques from both fields.
 
 
[[Anatomy]] is an important branch of physiology and considers how [[organ (biology)|organ]] systems in animals, such as the [[nervous system|nervous]], [[immune system|immune]], [[endocrine system|endocrine]], [[respiratory system|respiratory]], and [[circulatory system|circulatory]] systems, function and interact. The study of these systems is shared with [[medicine|medically]] oriented disciplines such as [[neurology]] and [[immunology]].
 
 
===Diversity and evolution of organisms===
 
[[Image:fitness-landscape-cartoon.png|thumb|300px|In [[population genetics]] the [[evolution]] of a [[population]] of organisms is sometimes depicted as if travelling on a [[fitness landscape]]. The arrows indicate the preferred flow of a population on the landscape, and the points A, B, and C are local optima. The red ball indicates a population that moves from a very low fitness value to the top of a peak]]
 
 
''Main articles:'' '''[[Evolutionary biology]]''', [[Biodiversity]], [[Botany]], [[Zoology]]
 
 
Evolutionary biology is concerned with the origin and descent of [[species]], as well as their change over time, and includes scientists from many [[taxonomy|taxonomically]]-oriented disciplines. For example, it generally involves scientists who have special training in particular [[organism]]s such as [[mammalogy]], [[ornithology]], or [[herpetology]], but use those organisms as systems to answer general questions about evolution. Evolutionary biology is mainly based on [[paleontology]], which uses the [[fossil]] record to answer questions about the mode and tempo of evolution, as well as the developments in areas such as [[population genetics]] and evolutionary theory. In the [[1990s]], [[developmental biology]] re-entered evolutionary biology from its initial exclusion from the modern synthesis through the study of [[evolutionary developmental biology]]. Related fields which are often considered part of evolutionary biology are [[phylogenetics]], [[systematics]], and [[taxonomy]].
 
 
The two major traditional taxonomically-oriented disciplines are [[botany]] and [[zoology]].
 
Botany is the scientific study of [[plant|plants]]. Botany covers a wide range of scientific disciplines that study the [[growth]], [[reproduction]], [[metabolism]], [[morphogenesis|development]], [[phytopathology|diseases]], and [[evolution]] of plant life.
 
Zoology involves the study of [[animal]]s, including the study of their [[physiology]] within the fields of [[anatomy]] and [[embryology]]. The common [[genetics|genetic]] and developmental mechanisms of animals and plants is studied in [[molecular biology]], [[molecular genetics]], and [[developmental biology]]. The [[ecology]] of animals is covered under [[behavioral ecology]] and other fields.
 
 
==== Classification of life ====
 
The dominant classification system is called [[Linnaean taxonomy]], which includes ranks and [[binomial nomenclature]]. How organisms are named is governed by international agreements such as the [[International Code of Botanical Nomenclature]] (ICBN), the [[International Code of Zoological Nomenclature]] (ICZN), and the [[International Code of Nomenclature of Bacteria]] (ICNB). A fourth Draft BioCode was published in 1997 in an attempt to standardize naming in these three areas, but it has yet to be formally adopted. The [[International Code of Virus Classification and Nomenclature]] (ICVCN) remains outside the BioCode.
 
 
===Interactions of organisms===
 
[[Image:Foodweb.png|frame|A [[food web]], a generalization of the food chain, depicting the complex interrelationships among organisms in an [[ecosystem]].]]
 
''Main articles:'' [[Ecology]], [[Ethology]], [[Behavior]], [[Biogeography]]
 
 
[[Ecology]] studies the distribution and abundance of [[life|living organisms]], and the interactions between organisms and their [[natural environment|environment]]. The environment of an organism includes both its habitat, which can be described as the sum of local abiotic factors such as [[climate]] and [[geology]], as well as the other the organisms that share its habitat. Ecological systems are studied at several different levels, from individuals and [[population]]s to [[ecosystem]]s and the [[biosphere]]. As can be surmised, ecology is a science that draws on several disciplines.
 
 
[[Ethology]] studies [[animal]] [[behavior]] (particularly of social animals such as [[primate]]s and [[canidae|canids]]), and is sometimes considered a branch of [[zoology]]. Ethologists have been particularly concerned with the [[evolution]] of behavior and the understanding of behavior in terms of the theory of [[natural selection]]. In one sense, the first modern ethologist was [[Charles Darwin]], whose book ''The expression of the emotions in animals and men'' influenced many ethologists.
 
 
[[Biogeography]] studies the spatial distribution of organisms on the [[Earth]], focusing on topics like [[plate tectonics]], [[climate change]], dispersal and migration, and [[cladistics]].
 
 
== History of the word "biology" ==
 
Formed by combining the Greek &#946;&#943;&#959;&#962; ''(bios)'', meaning 'life', and &#955;&#972;&#947;&#959;&#962; ''(logos)'', meaning 'study of', the word "biology" in its modern sense seems to have been introduced independently by [[Gottfried Reinhold Treviranus]] (''Biologie oder Philosophie der lebenden Natur'', [[1802]]) and by [[Jean-Baptiste Lamarck]] (''Hydrogéologie'', 1802). The word itself is sometimes said to have been coined in [[1800]] by [[Karl Friedrich Burdach]], but it appears in the title of Volume 3 of [[Michael Christoph Hanov]]'s ''Philosophiae naturalis sive physicae dogmaticae'': ''Geologia, biologia, phytologia generalis et dendrologia'', published in [[1766]].
 
 
==History==
 
''Main articles: [[History of biology]], [[History of medicine]], [[History of genetics]]''
 
 
Major discoveries in biology include:
 
* [[Cell theory]]
 
* [[Germ theory of disease]]
 
* [[Genetics]]
 
* [[Evolution]]
 
* [[DNA]]
 
 
==See also==
 
''Main articles:'' [[List of biology topics]]
 
 
{| width="100%" bgcolor="#fff4f4" id="toc"
 
!align="center" colspan="2"|[[List of biology topics|Topics related to biology]] ([[:Category:Biology|Category]])
 
 
|-align="center"
 
!align="left" valign="top"|People and history
 
|align="left" valign="top"|[[Biologist]] - [[List of biologists|Notable biologists]] - [[History of biology]] - [[Nobel Prize in Physiology or Medicine]] - [[Timeline of biology and organic chemistry]] - [[List of geneticists and biochemists]]
 
|-align="center"
 
!align="left" valign="top"|Institutions, publications
 
|align="left" valign="top"|[[NASA Ames Research Center]] - [[Bachelor of Science]] - [[List of publications in biology|Publications]]
 
|-align="center"
 
!align="left" valign="top"|Terms and phrases
 
|align="left" valign="top"|''[[Omne vivum ex ovo]]'' - ''[[In vivo]]'' - ''[[In vitro]]'' - ''[[In utero]]'' - ''[[In silico]]''
 
|-align="center"
 
!align="left" valign="top"|Related disciplines
 
|align="left" valign="top"|[[Medicine]] ([[Physician]]) - [[Physical anthropology]] - [[Environmental science]]
 
|}
 
*[[Biochemistry]]
 
*[[Biological symbiosis]]
 
*[[Biosynthesis]]
 
*[[Neurobiology]]
 
*[[Phylogenesis]]
 
*[[Psychobiology]]
 
*[[Sociobiology]]
 
*[[Zoology]]
 
 
==Further reading==
 
* [[Lynn Margulis]], ''Five Kingdoms: An Illustrated Guide to the Phyla of Life on Earth,'' 3rd ed., St. Martin's Press, [[1997]], paperback, ISBN 0805072527 (many other editions)
 
* [[Neil Campbell]], ''Biology (7th edition)'', Benjamin-Cummings Publishing Company, [[2004]], hardcover, ISBN 080537146X
 
 
==External links==
 
*[http://www.biologynews.net/ ''Biology News Net'']: Daily updated biology news & community website.
 
*[http://www.bionews.in/ ''BioNews :Latest Biology News '']: Research News and Articles from Biological Science and related fields.
 
*[http://www.rom.on.ca/biodiversity/biocode/biocode1997.html ''BioCode'']: A proposal for organism naming.
 
* [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=Books NCBI Open-Access Books]
 
*[[PhyloCode]], [http://www.ohiou.edu/phylocode/index.html]
 
*[http://tolweb.org/tree/phylogeny.html ''The Tree of Life'']: A multi-authored, distributed Internet project containing information about phylogeny and biodiversity.
 
*[http://www.bioone.org/perlserv/?request=index-html BioOne] Bioscience research journals.
 
*[http://www.everythingbio.com EverythingBio] Protocols, graduate school information, hard to find definitions.
 
 
=='''Journal Links'''==
 
*[http://biology.plosjournals.org/perlserv/?request=index-html&issn=1545-7885 PLos Biology] A peer-reviewed, open-access journal published by the Public Library of Science
 
*[http://www.press.jhu.edu/journals/perspectives_in_biology_and_medicine/index.html Perspectives in Biology and Medicine]
 
 
 
 
{{Natural sciences-footer}}
 
   
 
[[Category:Biology|*]]
 
[[Category:Biology|*]]
 
[[Category:Sciences]]
 
[[Category:Sciences]]
 
{{enWP|Biology}}
 

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