Biology

Biology

Biology deals with the study of the many living organisms.
(top: E. coli bacteria and gazelle)
(bottom: Goliath beetle and tree fern)

Biology is a energy and by regulating their internal environment to maintain a stable and vital condition.

Subdisciplines of biology are defined by the scale at which organisms are studied, the kinds of organisms studied, and the methods used to study them: environment.[2]

Contents

  • History 1
  • Foundations of modern biology 2
    • Cell theory 2.1
    • Evolution 2.2
    • Genetics 2.3
    • Homeostasis 2.4
    • Energy 2.5
  • Study and research 3
    • Structural 3.1
    • Physiological 3.2
    • Evolutionary 3.3
    • Systematic 3.4
    • Ecological and environmental 3.5
  • Basic unresolved problems in biology 4
  • Branches 5
  • See also 6
  • References 7
  • Further reading 8
  • External links 9

History

A Diagram of a fly from Robert Hooke's innovative Micrographia, 1665
Ernst Haeckel's Tree of Life (1879)

The term Karl Friedrich Burdach used the term in 1800 in a more restricted sense of the study of human beings from a morphological, physiological and psychological perspective (Propädeutik zum Studien der gesammten Heilkunst). The term came into its modern usage with the six-volume treatise Biologie, oder Philosophie der lebenden Natur (1802–22) by Gottfried Reinhold Treviranus, who announced:[5]

The objects of our research will be the different forms and manifestations of life, the conditions and laws under which these phenomena occur, and the causes through which they have been effected. The science that concerns itself with these objects we will indicate by the name biology [Biologie] or the doctrine of life [Lebenslehre].

Although modern biology is a relatively recent development, sciences related to and included within it have been studied since ancient times. Natural philosophy was studied as early as the ancient civilizations of Mesopotamia, Egypt, the Indian subcontinent, and China. However, the origins of modern biology and its approach to the study of nature are most often traced back to ancient Greece.[6][7] While the formal study of medicine dates back to Hippocrates (ca. 460 BC – ca. 370 BC), it was Aristotle (384 BC – 322 BC) who contributed most extensively to the development of biology. Especially important are his History of Animals and other works where he showed naturalist leanings, and later more empirical works that focused on biological causation and the diversity of life. Aristotle's successor at the Lyceum, Theophrastus, wrote a series of books on botany that survived as the most important contribution of antiquity to the plant sciences, even into the Middle Ages.[8]

Scholars of the medieval Islamic world who wrote on biology included al-Jahiz (781–869), Al-Dīnawarī (828–896), who wrote on botany,[9] and Rhazes (865–925) who wrote on anatomy and physiology. Medicine was especially well studied by Islamic scholars working in Greek philosopher traditions, while natural history drew heavily on Aristotelian thought, especially in upholding a fixed hierarchy of life.

Biology began to quickly develop and grow with Anton van Leeuwenhoek's dramatic improvement of the microscope. It was then that scholars discovered spermatozoa, bacteria, infusoria and the diversity of microscopic life. Investigations by Jan Swammerdam led to new interest in entomology and helped to develop the basic techniques of microscopic dissection and staining.[10]

Advances in life, although they opposed the idea that (3) all cells come from the division of other cells. Thanks to the work of Robert Remak and Rudolf Virchow, however, by the 1860s most biologists accepted all three tenets of what came to be known as cell theory.[11][12]

Meanwhile, taxonomy and classification became the focus of natural historians. common descent. Though he was opposed to evolution, Buffon is a key figure in the history of evolutionary thought; his work influenced the evolutionary theories of both Lamarck and Darwin.[14]

Serious evolutionary thinking originated with the works of natural selection; similar reasoning and evidence led Alfred Russel Wallace to independently reach the same conclusions.[17][18] Although it was the subject of controversy (which continues to this day), Darwin's theory quickly spread through the scientific community and soon became a central axiom of the rapidly developing science of biology.

The discovery of the physical representation of heredity came along with evolutionary principles and viruses and bacteria, along with the discovery of the double helical structure of DNA in 1953, marked the transition to the era of molecular genetics. From the 1950s to present times, biology has been vastly extended in the molecular domain. The genetic code was cracked by Har Gobind Khorana, Robert W. Holley and Marshall Warren Nirenberg after DNA was understood to contain codons. Finally, the Human Genome Project was launched in 1990 with the goal of mapping the general human genome. This project was essentially completed in 2003,[19] with further analysis still being published. The Human Genome Project was the first step in a globalized effort to incorporate accumulated knowledge of biology into a functional, molecular definition of the human body and the bodies of other organisms.

Foundations of modern biology

Cell theory

Human cancer cells with nuclei (specifically the DNA) stained blue. The central and rightmost cell are in interphase, so the entire nuclei are labeled. The cell on the left is going through mitosis and its DNA has condensed.

Cell theory states that the egg. The cell is also considered to be the basic unit in many pathological processes.[20] In addition, the phenomenon of energy flow occurs in cells in processes that are part of the function known as metabolism. Finally, cells contain hereditary information (DNA), which is passed from cell to cell during cell division.

Evolution

Natural selection of a population for dark coloration.

A central organizing concept in biology is that life changes and develops through evolution, and that all life-forms known have a 3.5 billion years ago.[21] Biologists generally regard the universality and ubiquity of the genetic code as definitive evidence in favor of the theory of universal common descent for all bacteria, archaea, and eukaryotes (see: origin of life).[22]

Introduced into the scientific lexicon by Jean-Baptiste de Lamarck in 1809,[23] evolution was established by Charles Darwin fifty years later as a viable scientific model when he articulated its driving force: natural selection.[24][25][26] (Alfred Russel Wallace is recognized as the co-discoverer of this concept as he helped research and experiment with the concept of evolution.)[27] Evolution is now used to explain the great variations of life found on Earth.

Darwin theorized that species and breeds developed through the processes of natural selection and artificial selection or selective breeding.[28] Genetic drift was embraced as an additional mechanism of evolutionary development in the modern synthesis of the theory.[29]

The evolutionary history of the phylogenetics, phenetics, and cladistics. (For a summary of major events in the evolution of life as currently understood by biologists, see evolutionary timeline.)

Genetics

A Punnett square depicting a cross between two pea plants heterozygous for purple (B) and white (b) blossoms

  • PLos Biology A peer-reviewed, open-access journal published by the Public Library of Science
  • Current Biology General journal publishing original research from all areas of biology
  • Biology Letters A high-impact Royal Society journal publishing peer-reviewed Biology papers of general interest
  • Science Magazine Internationally Renowned AAAS Science Publication – See Sections of the Life Sciences
  • International Journal of Biological Sciences A biological journal publishing significant peer-reviewed scientific papers
  • Perspectives in Biology and Medicine An interdisciplinary scholarly journal publishing essays of broad relevance
  • Life Science Log
Journal links
  • Biology at DMOZ
  • OSU's Phylocode
  • Biology Online – Wiki Dictionary
  • MIT video lecture series on biology
  • Biology and Bioethics.
  • Biological Systems – Idaho National Laboratory
  • The Tree of Life: A multi-authored, distributed Internet project containing information about phylogeny and biodiversity.
  • The Study of Biology
  • Using the Biological Literature Web Resources

External links

Further reading

  1. ^ Based on definition from:
  2. ^
  3. ^
  4. ^
  5. ^
  6. ^
  7. ^
  8. ^ Public Domain One or more of the preceding sentences incorporates text from a publication now in the public domain
  9. ^
  10. ^
  11. ^ Sapp, Jan (2003) Genesis: The Evolution of Biology, Ch. 7. Oxford University Press: New York. ISBN 0-19-515618-8
  12. ^ Coleman, William (1977) Biology in the Nineteenth Century: Problems of Form, Function, and Transformation, Ch. 2. Cambridge University Press: New York. ISBN 0-521-29293-X
  13. ^ Mayr, The Growth of Biological Thought, chapter 4
  14. ^ Mayr, The Growth of Biological Thought, chapter 7
  15. ^ Gould, Stephen Jay. The Structure of Evolutionary Theory. The Belknap Press of Harvard University Press: Cambridge, 2002. ISBN 0-674-00613-5. p. 187.
  16. ^ Lamarck (1914)
  17. ^ Mayr, The Growth of Biological Thought, chapter 10: "Darwin's evidence for evolution and common descent"; and chapter 11: "The causation of evolution: natural selection"
  18. ^
  19. ^
  20. ^
  21. ^
  22. ^
  23. ^
  24. ^ The Complete Works of Darwin Online – Biography. darwin-online.org.uk. Retrieved on 2006-12-15
  25. ^
  26. ^ As Darwinian scholar Joseph Carroll of the University of Missouri–St. Louis puts it in his introduction to a modern reprint of Darwin's work: "The Origin of Species has special claims on our attention. It is one of the two or three most significant works of all time—one of those works that fundamentally and permanently alter our vision of the world ... It is argued with a singularly rigorous consistency but it is also eloquent, imaginatively evocative, and rhetorically compelling."
  27. ^ Shermer p. 149.
  28. ^ Darwin, Charles (1859). On the Origin of Species, John Murray.
  29. ^
  30. ^
  31. ^ Marcial, Gene G. (August 13, 2007) From SemBiosys, A New Kind Of Insulin. businessweek.com
  32. ^
  33. ^
  34. ^ Raven, PH; Johnson, GB. (1999) Biology, Fifth Edition, Boston: Hill Companies, Inc. p. 1058. ISBN 0697353532.
  35. ^ Rodolfo, Kelvin (2000-01-03) What is homeostasis? Scientific American.
  36. ^
  37. ^
  38. ^ Edwards, Katrina. Microbiology of a Sediment Pond and the Underlying Young, Cold, Hydrologically Active Ridge Flank. Woods Hole Oceanographic Institution.
  39. ^
  40. ^ Bartsch, John and Colvard, Mary P. (2009) The Living Environment. New York State Prentice Hall. ISBN 0133612023.
  41. ^
  42. ^ Gray, Henry (1918) "Anatomy of the Human Body". 20th edition.
  43. ^
  44. ^
  45. ^
  46. ^
  47. ^
  48. ^
  49. ^
  50. ^
  51. ^
  52. ^
  53. ^ Gillespie, John H. (1998) Population Genetics: A Concise Guide, Johns Hopkins Press. ISBN 0-8018-5755-4.
  54. ^ Vassiliki Betta Smocovitis (1996) Unifying Biology: the evolutionary synthesis and evolutionary biology. Princeton University Press. ISBN 0-691-03343-9.
  55. ^
  56. ^
  57. ^
  58. ^ a b
  59. ^
  60. ^ Recommendation 60F
  61. ^
  62. ^
  63. ^ Index of Viruses – Pospiviroidae (2006). In: ICTVdB – The Universal Virus Database, version 4. Büchen-Osmond, C (Ed), Columbia University, New York, USA. Version 4 is based on Virus Taxonomy, Classification and Nomenclature of Viruses, 8th ICTV Report of the International Committee on Taxonomy of Viruses. Fauquet, CM, Mayo, MA, Maniloff, J, Desselberger, U, and Ball, LA (EDS) (2005) Elsevier/Academic Press, pp. 1259.
  64. ^
  65. ^
  66. ^
  67. ^
  68. ^
  69. ^
  70. ^
  71. ^
  72. ^
  73. ^
  74. ^
  75. ^ Bernstein, Harris; Bernstein, Carol and Michod, Richard E. (2011). "Meiosis as an Evolutionary Adaptation for DNA Repair". Chapter 19 in DNA Repair. Inna Kruman editor. InTech Open Publisher.
  76. ^ Hörandl, Elvira (2013). Meiosis and the Paradox of Sex in Nature, Meiosis, Dr. Carol Bernstein (Ed.), ISBN 978-953-51-1197-9, InTech, .
  77. ^
  78. ^
return p

end

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%s
function p._hatnote(s, options) checkType('_hatnote', 1, s, 'string') checkType('_hatnote', 2, options, 'table', true) local classes = {'hatnote'} local extraclasses = options.extraclasses local selfref = options.selfref if type(extraclasses) == 'string' then classes[#classes + 1] = extraclasses end if selfref then classes[#classes + 1] = 'selfref' end return string.format( '

function p.hatnote(frame) local args = getArgs(frame) local s = args[1] local options = {} if not s then return p.makeWikitextError( 'no text specified', 'Template:Hatnote#Errors', args.category ) end options.extraclasses = args.extraclasses options.selfref = args.selfref return p._hatnote(s, options) end


-- Hatnote -- -- Produces standard hatnote text. Implements the template.


function p._formatLink(link, display) -- Find whether we need to use the colon trick or not. We need to use the -- colon trick for categories and files, as otherwise category links -- categorise the page and file links display the file. checkType('_formatLink', 1, link, 'string') checkType('_formatLink', 2, display, 'string', true) link = removeInitialColon(link) local namespace = p.findNamespaceId(link, false) local colon if namespace == 6 or namespace == 14 then colon = ':' else colon = end -- Find whether a faux display value has been added with the | magic -- word. if not display then local prePipe, postPipe = link:match('^(.-)|(.*)$') link = prePipe or link display = postPipe end -- Find the display value. if not display then local page, section = link:match('^(.-)#(.*)$') if page then display = page .. ' § ' .. section end end -- Assemble the link. if display then return string.format('%s', colon, link, display) else return string.format('%s%s', colon, link) end end

function p.formatLink(frame) local args = getArgs(frame) local link = args[1] local display = args[2] if not link then return p.makeWikitextError( 'no link specified', 'Template:Format hatnote link#Errors', args.category ) end return p._formatLink(link, display) end


-- Format link -- -- Makes a wikilink from the given link and display values. Links are escaped -- with colons if necessary, and links to sections are detected and displayed -- with " § " as a separator rather than the standard MediaWiki "#". Used in -- the template.


function p.makeWikitextError(msg, helpLink, addTrackingCategory) -- Formats an error message to be returned to wikitext. If -- addTrackingCategory is not false after being returned from -- Module:Yesno, and if we are not on a talk page, a tracking category -- is added. checkType('makeWikitextError', 1, msg, 'string') checkType('makeWikitextError', 2, helpLink, 'string', true) yesno = require('Module:Yesno') local title = mw.title.getCurrentTitle() -- Make the help link text. local helpText if helpLink then helpText = ' (help)' else helpText = end -- Make the category text. local category if not title.isTalkPage and yesno(addTrackingCategory) ~= false then category = 'Hatnote templates with errors' category = string.format( '%s:%s', mw.site.namespaces[14].name, category ) else category = end return string.format( '%s', msg, helpText, category ) end

function p.formatPageTables(...) -- Takes a list of page/display tables and returns it as a list of -- formatted links. Nil values are not allowed. local pages = {...} local links = {} for i, t in ipairs(pages) do checkType('formatPageTables', i, t, 'table') local link = t[1] local display = t[2] links[i] = p._formatLink(link, display) end return links end

function p.formatPages(...) -- Formats a list of pages using formatLink and returns it as an array. Nil -- values are not allowed. local pages = {...} local ret = {} for i, page in ipairs(pages) do ret[i] = p._formatLink(page) end return ret end

function p.findNamespaceId(link, removeColon) -- Finds the namespace id (namespace number) of a link or a pagename. This -- function will not work if the link is enclosed in double brackets. Colons -- are trimmed from the start of the link by default. To skip colon -- trimming, set the removeColon parameter to true. checkType('findNamespaceId', 1, link, 'string') checkType('findNamespaceId', 2, removeColon, 'boolean', true) if removeColon ~= false then link = removeInitialColon(link) end local namespace = link:match('^(.-):') if namespace then local nsTable = mw.site.namespaces[namespace] if nsTable then return nsTable.id end end return 0 end

local function removeInitialColon(s) -- Removes the initial colon from a string, if present. return s:match('^:?(.*)') end

local function getArgs(frame) -- Fetches the arguments from the parent frame. Whitespace is trimmed and -- blanks are removed. mArguments = require('Module:Arguments') return mArguments.getArgs(frame, {parentOnly = true}) end


-- Helper functions


local p = {}

local libraryUtil = require('libraryUtil') local checkType = libraryUtil.checkType local mArguments -- lazily initialise Module:Arguments local yesno -- lazily initialise Module:Yesno


return p-------------------------------------------------------------------------------- -- Module:Hatnote -- -- -- -- This module produces hatnote links and links to related articles. It -- -- implements the and meta-templates and includes -- -- helper functions for other Lua hatnote modules. --

end

', table.concat(classes, ' '), s )
%s
function p._hatnote(s, options) checkType('_hatnote', 1, s, 'string') checkType('_hatnote', 2, options, 'table', true) local classes = {'hatnote'} local extraclasses = options.extraclasses local selfref = options.selfref if type(extraclasses) == 'string' then classes[#classes + 1] = extraclasses end if selfref then classes[#classes + 1] = 'selfref' end return string.format( '

function p.hatnote(frame) local args = getArgs(frame) local s = args[1] local options = {} if not s then return p.makeWikitextError( 'no text specified', 'Template:Hatnote#Errors', args.category ) end options.extraclasses = args.extraclasses options.selfref = args.selfref return p._hatnote(s, options) end


-- Hatnote -- -- Produces standard hatnote text. Implements the template.


function p._formatLink(link, display) -- Find whether we need to use the colon trick or not. We need to use the -- colon trick for categories and files, as otherwise category links -- categorise the page and file links display the file. checkType('_formatLink', 1, link, 'string') checkType('_formatLink', 2, display, 'string', true) link = removeInitialColon(link) local namespace = p.findNamespaceId(link, false) local colon if namespace == 6 or namespace == 14 then colon = ':' else colon = end -- Find whether a faux display value has been added with the | magic -- word. if not display then local prePipe, postPipe = link:match('^(.-)|(.*)$') link = prePipe or link display = postPipe end -- Find the display value. if not display then local page, section = link:match('^(.-)#(.*)$') if page then display = page .. ' § ' .. section end end -- Assemble the link. if display then return string.format('%s', colon, link, display) else return string.format('%s%s', colon, link) end end

function p.formatLink(frame) local args = getArgs(frame) local link = args[1] local display = args[2] if not link then return p.makeWikitextError( 'no link specified', 'Template:Format hatnote link#Errors', args.category ) end return p._formatLink(link, display) end


-- Format link -- -- Makes a wikilink from the given link and display values. Links are escaped -- with colons if necessary, and links to sections are detected and displayed -- with " § " as a separator rather than the standard MediaWiki "#". Used in -- the template.


function p.makeWikitextError(msg, helpLink, addTrackingCategory) -- Formats an error message to be returned to wikitext. If -- addTrackingCategory is not false after being returned from -- Module:Yesno, and if we are not on a talk page, a tracking category -- is added. checkType('makeWikitextError', 1, msg, 'string') checkType('makeWikitextError', 2, helpLink, 'string', true) yesno = require('Module:Yesno') local title = mw.title.getCurrentTitle() -- Make the help link text. local helpText if helpLink then helpText = ' (help)' else helpText = end -- Make the category text. local category if not title.isTalkPage and yesno(addTrackingCategory) ~= false then category = 'Hatnote templates with errors' category = string.format( '%s:%s', mw.site.namespaces[14].name, category ) else category = end return string.format( '%s', msg, helpText, category ) end

function p.formatPageTables(...) -- Takes a list of page/display tables and returns it as a list of -- formatted links. Nil values are not allowed. local pages = {...} local links = {} for i, t in ipairs(pages) do checkType('formatPageTables', i, t, 'table') local link = t[1] local display = t[2] links[i] = p._formatLink(link, display) end return links end

function p.formatPages(...) -- Formats a list of pages using formatLink and returns it as an array. Nil -- values are not allowed. local pages = {...} local ret = {} for i, page in ipairs(pages) do ret[i] = p._formatLink(page) end return ret end

function p.findNamespaceId(link, removeColon) -- Finds the namespace id (namespace number) of a link or a pagename. This -- function will not work if the link is enclosed in double brackets. Colons -- are trimmed from the start of the link by default. To skip colon -- trimming, set the removeColon parameter to true. checkType('findNamespaceId', 1, link, 'string') checkType('findNamespaceId', 2, removeColon, 'boolean', true) if removeColon ~= false then link = removeInitialColon(link) end local namespace = link:match('^(.-):') if namespace then local nsTable = mw.site.namespaces[namespace] if nsTable then return nsTable.id end end return 0 end

local function removeInitialColon(s) -- Removes the initial colon from a string, if present. return s:match('^:?(.*)') end

local function getArgs(frame) -- Fetches the arguments from the parent frame. Whitespace is trimmed and -- blanks are removed. mArguments = require('Module:Arguments') return mArguments.getArgs(frame, {parentOnly = true}) end


-- Helper functions


local p = {}

local libraryUtil = require('libraryUtil') local checkType = libraryUtil.checkType local mArguments -- lazily initialise Module:Arguments local yesno -- lazily initialise Module:Yesno


-- Module:Hatnote -- -- -- -- This module produces hatnote links and links to related articles. It -- -- implements the and meta-templates and includes -- -- helper functions for other Lua hatnote modules. --


References

See also

  • Aerobiology – the study of airborne organic particles
  • Agriculture – the study of producing crops and raising livestock, with an emphasis on practical applications
  • Anatomy – the study of form and function, in plants, animals, and other organisms, or specifically in humans
    • Histology – the study of cells and tissues, a microscopic branch of anatomy
  • Astrobiology (also known as exobiology, exopaleontology, and bioastronomy) – the study of evolution, distribution, and future of life in the universe
  • Biochemistry – the study of the chemical reactions required for life to exist and function, usually a focus on the cellular level
  • Bioengineering – the study of biology through the means of engineering with an emphasis on applied knowledge and especially related to biotechnology
  • Biogeography – the study of the distribution of species spatially and temporally
  • Bioinformatics – the use of information technology for the study, collection, and storage of genomic and other biological data
  • Biomathematics (or Mathematical biology) – the quantitative or mathematical study of biological processes, with an emphasis on modeling
  • Biomechanics – often considered a branch of medicine, the study of the mechanics of living beings, with an emphasis on applied use through prosthetics or orthotics
  • Biomedical research – the study of health and disease
    • Pharmacology – the study and practical application of preparation, use, and effects of drugs and synthetic medicines
  • Biomusicology – the study of music from a biological point of view.
  • Biophysics – the study of biological processes through physics, by applying the theories and methods traditionally used in the physical sciences
  • Biosemiotics – the study of biological processes through semiotics, by applying the models of meaning-making and communication
  • Biotechnology – the study of the manipulation of living matter, including genetic modification and synthetic biology
    • Synthetic biology – research integrating biology and engineering; construction of biological functions not found in nature
  • Building biology – the study of the indoor living environment
  • Botany – the study of plants
  • Cell biology – the study of the cell as a complete unit, and the molecular and chemical interactions that occur within a living cell
  • Cognitive biology – the study of cognition as a biological function
  • Conservation biology – the study of the preservation, protection, or restoration of the natural environment, natural ecosystems, vegetation, and wildlife
  • Cryobiology – the study of the effects of lower than normally preferred temperatures on living beings
  • Developmental biology – the study of the processes through which an organism forms, from zygote to full structure
    • Embryology – the study of the development of embryo (from fecundation to birth)
  • Ecology – the study of the interactions of living organisms with one another and with the non-living elements of their environment
  • Environmental biology – the study of the natural world, as a whole or in a particular area, especially as affected by human activity
  • Epidemiology – a major component of public health research, studying factors affecting the health of populations
  • Evolutionary biology – the study of the origin and descent of species over time
  • Genetics – the study of genes and heredity.
    • Epigenetics – the study of heritable changes in gene expression or cellular phenotype caused by mechanisms other than changes in the underlying DNA sequence
  • Hematology (also known as Haematology) – the study of blood and blood-forming organs.
  • Integrative biology – the study of whole organisms
  • Limnology – the study of inland waters
  • Marine biology (or Biological oceanography) – the study of ocean ecosystems, plants, animals, and other living beings
  • Microbiology – the study of microscopic organisms (microorganisms) and their interactions with other living things
  • Molecular biology – the study of biology and biological functions at the molecular level, some cross over with biochemistry
  • nanoscale level of organization
  • Neurobiology – the study of the nervous system, including anatomy, physiology and pathology
  • Population biology – the study of groups of conspecific organisms, including
  • Paleontology – the study of fossils and sometimes geographic evidence of prehistoric life
  • Pathobiology or pathology – the study of diseases, and the causes, processes, nature, and development of disease
  • Physiology – the study of the functioning of living organisms and the organs and parts of living organisms
  • Phytopathology – the study of plant diseases (also called Plant Pathology)
  • Psychobiology – the study of the biological bases of psychology
  • Quantum biology - the study of quantum mechanics to biological objects and problems.
  • Sociobiology – the study of the biological bases of sociology
  • Structural biology – a branch of molecular biology, biochemistry, and biophysics concerned with the molecular structure of biological macromolecules
  • Zoology – the study of animals, including classification, physiology, development, and behavior, including:

These are the main branches of biology:[77][78]

Branches

Another basic unresolved problem in biology is the biologic basis of aging. At present, there is no consensus view on the underlying cause of aging. Various competing theories are outlined in Ageing Theories.

Despite the profound advances made over recent decades in our understanding of life's fundamental processes, some basic problems have remained unresolved. For example, one of the major unresolved problems in biology is the primary adaptive function of sex, and particularly its key processes in eukaryotes, meiosis and homologous recombination. One view is that sex evolved primarily as an adaptation for increasing genetic diversity (see references e.g.[73][74]). An alternative view is that sex is an adaptation for promoting accurate DNA repair in germ-line DNA, and that increased genetic diversity is primarily a byproduct that may be useful in the long run.[75][76] (See also Evolution of sexual reproduction).

Basic unresolved problems in biology

Earth, focusing on topics like plate tectonics, climate change, dispersal and migration, and cladistics.

Ethology studies animal behavior (particularly that of social animals such as primates and 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 Man and Animals, influenced many ethologists to come.[72]

Ecological systems are studied at several different levels, from individuals and populations to ecosystems and the biosphere. The term population biology is often used interchangeably with population ecology, although population biology is more frequently used when studying diseases, viruses, and microbes, while population ecology is more commonly used when studying plants and animals. Ecology draws on many subdisciplines.

bacterium in a local sugar gradient is responding to its environment as much as a lion searching for food in the African savanna. For any species, behaviors can be co-operative, competitive, parasitic, or symbiotic. Matters become more complex when two or more species interact in an ecosystem.

Mutual symbiosis between clownfish of the genus Amphiprion that dwell among the tentacles of tropical sea anemones. 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.

Ecological and environmental

A merging draft, BioCode, was published in 1997 in an attempt to standardize nomenclature in these three areas, but has yet to be formally adopted.[66] The BioCode draft has received little attention since 1997; its originally planned implementation date of January 1, 2000, has passed unnoticed. A revised BioCode that, instead of replacing the existing codes, would provide a unified context for them, was proposed in 2011.[67][68][69] However, the International Botanical Congress of 2011 declined to consider the BioCode proposal. The ICVCN remains outside the BioCode, which does not include viral classification.

The dominant classification system is called the International Code of Nomenclature for algae, fungi, and plants (ICN), the International Code of Zoological Nomenclature (ICZN), and the International Code of Nomenclature of Bacteria (ICNB). The classification of viruses, viroids, prions, and all other sub-viral agents that demonstrate biological characteristics is conducted by the International Committee on Taxonomy of Viruses (ICTV) and is known as the International Code of Viral Classification and Nomenclature (ICVCN).[62][63][64][65] However, several other viral classification systems do exist.

[61] Additionally, the entire term may be italicized or underlined.[60] The scientific name of an organism is generated from its genus and species. For example, humans are listed as

Outside of these categories, there are obligate intracellular parasites that are "on the edge of life"[59] in terms of metabolic activity, meaning that many scientists do not actually classify these structures as alive, due to their lack of at least one or more of the fundamental functions or characteristics that define life. They are classified as viruses, viroids, prions, or satellites.

Further, each kingdom is broken down recursively until each species is separately classified. The order is: Domain; Kingdom; Phylum; Class; Order; Family; Genus; Species.

Traditionally, living things have been divided into five kingdoms: Monera; Protista; Fungi; Plantae; Animalia.[57] However, many scientists now consider this five-kingdom system outdated. Modern alternative classification systems generally begin with the three-domain system: Archaea (originally Archaebacteria); Bacteria (originally Eubacteria) and Eukaryota (including protists, fungi, plants, and animals)[58] These domains reflect whether the cells have nuclei or not, as well as differences in the chemical composition of key biomolecules such as ribosomes.[58]

Multiple speciation events create a tree structured system of relationships between species. The role of systematics is to study these relationships and thus the differences and similarities between species and groups of species.[55] However, systematics was an active field of research long before evolutionary thinking was common.[56]

The hierarchy of biological classification's eight major taxonomic ranks. Intermediate minor rankings are not shown. This diagram uses a 3 Domains / 6 Kingdoms format
A phylogenetic tree of all living things, based on rRNA gene data, showing the separation of the three domains bacteria, archaea, and eukaryotes 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.

Systematic

Evolutionary biology is partly based on paleontology, which uses the fossil record to answer questions about the mode and tempo of evolution,[52] and partly on the developments in areas such as population genetics.[53] In the 1980s, developmental biology re-entered evolutionary biology from its initial exclusion from the modern synthesis through the study of evolutionary developmental biology.[54] Related fields often considered part of evolutionary biology are phylogenetics, systematics, and taxonomy.

mammalogy, ornithology, botany, or herpetology, but use those organisms as systems to answer general questions about evolution.

Evolutionary

Physiology studies how for example nervous, immune, endocrine, respiratory, and circulatory systems, function and interact. The study of these systems is shared with medically oriented disciplines such as neurology and immunology.

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 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 borrows techniques from both research fields.

Physiological

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chromosomes, where it is represented in the chemical structure of particular DNA molecules.

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humans. Understanding the structure and function of cells is fundamental to all of the biological sciences. The similarities and differences between cell types are particularly relevant to molecular biology.

Molecular biology is the study of biology at a molecular level.[41] 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.

Schematic of typical animal organelles and structures.

Structural

Study and research

Some of the captured energy is used to produce biomass to sustain life and provide energy for growth and development. The majority of the rest of this energy is lost as heat and waste molecules. The most important processes for converting the energy trapped in chemical substances into energy useful to sustain life are metabolism[39] and cellular respiration.[40]

The organisms responsible for the introduction of energy into an ecosystem are known as producers or ATP, whose bonds can be broken to release energy.[37] A few ecosystems, however, depend entirely on energy extracted by chemotrophs from methane, sulfides, or other non-luminal energy sources.[38]

The survival of a living organism depends on the continuous input of energy. Chemical reactions that are responsible for its structure and function are tuned to extract energy from substances that act as its food and transform them to help form new cells and sustain them. In this process, molecules of chemical substances that constitute food play two roles; first, they contain energy that can be transformed for biological chemical reactions; second, they develop new molecular structures made up of biomolecules.

Energy

Basic overview of energy and human life.

To maintain dynamic equilibrium and effectively carry out certain functions, a system must detect and respond to perturbations. After the detection of a perturbation, a biological system normally responds through glucagon when sugar levels are too low.

Homeostasis is the ability of an unicellular or multicellular, exhibit homeostasis.[35]

The hypothalamus secretes CRH, which directs the pituitary gland to secrete ACTH. In turn, ACTH directs the adrenal cortex to secrete glucocorticoids, such as cortisol. The GCs then reduce the rate of secretion by the hypothalamus and the pituitary gland once a sufficient amount of GCs has been released.[34]

Homeostasis

DNA usually occurs as linear genotype.[33]

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