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Biology

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It contains such topics as classifying the various forms of organisms, how species come into existence, and the interactions they have with each other and with the natural 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 disciplines, many of which, for example, botany, zoology, and medicine are considered ancient fields of study.</p>

<p>Biology as a unified science was first developed in the nineteenth century, as scientists discovered that all living things shared certain fundamental characteristics and were best studied as a whole. Over a million papers are published annually in a wide array of biology and medicine journals,<sup ~~class="reference"~~ id="_ref-0" class="reference">[1]</sup> and biology is a standard subject of instruction at schools and universities around the world.</p>

<p>As such a vast field, biology is divided into a number of disciplines. The old divisions by type of organism remains with subjects such as botany encompassing the study of plants, zoology with the study of animals, and microbiology as the study of microorganisms. The field may also be divided based on the scale at which it is studied: biochemistry examines the fundamental chemistry of life; cellular biology examines the basic building block of all life, the cell; Physiology examines the mechanical and physical functions of an organism; and ecology examines how various organisms interrelate. Applied fields of biology such as medicine are more complex and involve many specialized sub-disciplines.</p>

<h2><span class="mw-headline">Foundations of modern biology</span></h2>

<h3><span class="mw-headline">Gene theory</span></h3>

Schematic representation of DNA, the primary genetic material.</div>

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<p>All terrestrial organisms use DNA and RNA-based genetic mechanisms to hold genetic information. Another universal principle is that all observed organisms with the exception of viruses are made of cells. Similarly, all organisms share common developmental processes.</p>

<h3><span class="mw-headline">Homeostasis</span></h3>

<p>[[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 organisms, 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 plants are theoretically able to grow healthier and remove more of the gas from the atmosphere. Tissues and organs can also maintain homeostasis.</p>

<h3><span class="mw-headline">Structure of life</span></h3>

Schematic of typical animal cell depicting the various organelles and structures.</div>

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<h3><span class="mw-headline">Diversity and evolution of organisms</span></h3>

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.</div>

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<p><em>Main ~~<a href="http://webspacehosting.com">web page</a>~~ articles:</em> <strong>Evolutionary biology</strong>, Biodiversity, Botany, Zoology is concerned with the origin and descent of species, as well as their change over time, and includes scientists from many taxonomically-oriented disciplines. For example, it generally involves scientists who have special training in particular organisms 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.</p>

<p>The two major traditional taxonomically-oriented disciplines are botany and zoology. Botany is the scientific study of plants. Botany covers a wide range of scientific disciplines that study the growth, reproduction, metabolism, development, diseases, and evolution of plant life. Zoology involves the study of animals, including the study of their physiology within the fields of anatomy and embryology. The common 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.</p>

<h3><span class="mw-headline">Taxonomy</span></h3>

<div class="messagebox cleanup metadata plainlinks"><strong>This article or section does not cite any references or sources.</strong><br />

Any material not supported by sources may be challenged and removed at any time. This article has been tagged since <strong>September 2006</strong>.</small></div>

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.</div>

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<p>Traditionally, living things have been divided into five kingdoms:</p>

<dl><dd>Monera -- Protista -- Fungi -- Plantae -- Animalia</dd></dl>

<p>However, many scientists now consider this five-kingdom system to be outdated. Modern alternative classification systems generally begin with the three-domain system:<sup ~~class="reference"~~ id="_ref-2" class="reference">[3]</sup></p>

<dl><dd>Archaea (originally Archaebacteria) -- Bacteria (originally Eubacteria) -- Eukaryota</dd></dl>

<p>These domains reflect whether the cells have nuclei or not, as well as differences in the cell exteriors.</p>

<h2><span class="mw-headline">History</span></h2>

<p>Although the concept of <em><strong class="selflink">biology</strong></em> as a single coherent field arose in the 19th century, the biological sciences emerged from traditions of medicine and natural history reaching back to Galen and Aristotle in ancient Greece. During the Renaissance and early modern period, biological thought was revolutionized by a renewed interest in empiricism and the discovery of many novel organisms. Prominent in this movement were Vesalius and Harvey, who used experimentation and careful observation in physiology, and naturalists such as Linnaeus and Buffon who began to classify the diversity of life and the fossil record, as well as the development and behavior of organisms. Microscopy revealed the previously unknown world of microorganisms, laying the groundwork for cell theory. The growing importance of natural theology, partly a response to the rise of mechanical philosophy, encouraged the growth of natural history (though it entrenched the argument from design).<sup ~~class="reference"~~ id="_ref-3" class="reference">[4]</sup></p><p>Over the 18th and 19th centuries, biological sciences such as botany and zoology became increasingly professional scientific disciplines. Lavoisier and other physical scientists began to connect the animate and inanimate worlds through physics and chemistry. Explorer-naturalists such as Alexander von Humboldt investigated the interaction between organisms and their environment, and the ways this relationship depends on geography—laying the foundations for biogeography, ecology and ethology. Naturalists began to reject essentialism and consider the importance of extinction and the mutability of species. Cell theory provided a new perspective on the fundamental basis of life. These developments, as well as the results from embryology and paleontology, were synthesized in Charles Darwin's theory of evolution by natural selection. The end of the 19th century saw the fall of spontaneous generation and the rise of the germ theory of disease, though the mechanism of inheritance remained a mystery.<sup ~~class="reference"~~ id="_ref-4" class="reference">[5]</sup></p><p>In the early 20th century, the rediscovery of Mendel's work led to the rapid development of genetics by Thomas Hunt Morgan and his students, and by the 1930s the combination of population genetics and natural selection in the "neo-Darwinian synthesis". New disciplines developed rapidly, especially after Watson and Crick proposed the structure of DNA. Following the establishment of the Central Dogma and the cracking of the genetic code, biology was largely split between <em>organismal biology</em>—the fields that deal with whole organisms and groups of organisms—and the fields related to <em>cellular and molecular biology</em>. By the late 20th century, new fields like genomics and proteomics were reversing this trend, with organismal biologists using molecular techniques, and molecular and cell biologists investigating the interplay between genes and the environment, as well as the genetics of natural populations of organisms.<sup ~~class="reference"~~ id="_ref-5" class="reference">[6]</sup></p>

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<th ~~align~~colspan="~~center~~2" ~~colspan~~align="2center">Topics related to biology (Category)</th>

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<h2><span class="mw-headline">References</span></h2>

<li id="_note-0"><strong>^</strong> <em>Biology: A Functional Approach</em> By Michael Bliss Vaughan Roberts. Cheltenham: Thomas Nelson and Sons, 1986. pg. 1 </li>

<h2><span class="mw-headline">Further reading</span></h2>

<ul>

<li><cite ~~class~~style="~~book~~FONT-STYLE: normal" id="Reference-Margulis-.5B.5B1997.5D.5D" ~~style~~class="~~FONT-STYLE: normal~~book">Margulis, Lynn (1997). <em>Five Kingdoms: An Illustrated Guide to the Phyla of Life on Earth</em>, 3rd edition, St. Martin's Press. ISBN 0-8050-7252-7.</cite><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Five+Kingdoms%3A+An+Illustrated+Guide+to+the+Phyla+of+Life+on+Earth&rft.aulast=Margulis&rft.aufirst=Lynn&rft.date=%5B%5B1997%5D%5D&rft.edition=3rd+edition&rft.pub=St.+Martin%27s+Press&rft.isbn=0-8050-7252-7"> </span> (many other editions) </li> <li><cite ~~class~~style="~~book~~FONT-STYLE: normal" id="Reference-Campbell-.5B.5B2004.5D.5D" ~~style~~class="~~FONT-STYLE: normal~~book">Campbell, Neil (2004). <em>Biology</em>, 7th edition, Benjamin-Cummings Publishing Company. ISBN 0-8053-7146-X.</cite><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Biology&rft.aulast=Campbell&rft.aufirst=Neil&rft.date=%5B%5B2004%5D%5D&rft.edition=7th+edition&rft.pub=Benjamin-Cummings+Publishing+Company&rft.isbn=0-8053-7146-X"> </span> </li> <li><cite ~~class~~style="~~book~~FONT-STYLE: normal" id="Reference-Johnson-.5B.5B2005.5D.5D" ~~style~~class="~~FONT-STYLE: normal~~book">Johnson, George B. (2005). <em>Biology, Visualizing Life</em>. Holt, Rinehart, and Winston. ISBN 0-03-016723-X.</cite><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Biology%2C+Visualizing+Life&rft.aulast=Johnson&rft.aufirst=George+B.&rft.date=%5B%5B2005%5D%5D&rft.pub=Holt%2C+Rinehart%2C+and+Winston&rft.isbn=0-03-016723-X"> </span> </li>

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