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Biology studies the variety of life ''(clockwise from top-left)'' '' E. Coli '', tree Fern , Gazelle , Goliath Beetle Biology (from Greek: βίος, ''bio'', " Life "; and λόγος, ''logos'', " Knowledge "), also referred to as the '''biological sciences''', is the study of Living Organisms utilizing the Scientific Method . Biology examines the structure, function, growth, origin, evolution, and distribution of living things. It classifies and describes organisms, their function, how species come into existence, and the interactions they have with each other and with the Natural Environment . Most biological sciences are specialized disciplines. Traditionally, they are grouped by the type of organism being studied:
The fields within biology are further divided based on the scale at which organisms are studied and the methods used to study them:
Applied Fields of biology such as Medicine and genetic research involve many specialized sub-disciplines. Biology as a separate Science was developed in the nineteenth century, as scientists discovered that organisms shared fundamental characteristics. Biology is now a standard subject of instruction at schools and universities around the world, and over a million papers are published annually in a wide array of biology and medicine Journals .1 FOUNDATIONS OF MODERN BIOLOGY There are four unifying principles of biology:
Cell theory See Also: Cell theory The cell is the fundamental unit of life. Cell theory states that all living things are composed of one or more cells, or the Secreted products of those cells, for example, Shell and Bone . Cells arise from other cells through Cell Division , and in multicellular organisms, every cell in the organism's body is produced from a single cell in a fertilized egg. Furthermore, the cell is considered to be the basic part of the pathological processes of an organism.2 Evolution See Also: Evolution A central organizing concept in biology is that all life has a common origin (see Common Descent ) and has changed and developed through Evolution . 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 Russel Wallace is recognized as the co-discoverer of this concept). Darwin theorized that species and breeds developed through the processes of Natural Selection as well as by Artificial Selection or Selective Breeding . Genetic Drift was embraced as an additional mechanism of evolutionary development in the Modern Synthesis of the theory. The evolutionary history of the Species — which describes the characteristics of the various species from which it descended— 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 . For a summary of major events in the evolution of life as currently understood by biologists, see Evolutionary Timeline . Up into the 19th Century , it was commonly believed that life forms could appear spontaneously under certain conditions (see Spontaneous Generation ). This misconception was challenged by William Harvey 's diction that "all life 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 shares a ). Evolution does not always give rise to progressively more complex organisms. For example, the process of Dysgenic s has been observed among the human population.3 Gene theory , the primary Genetic Material .]] See Also: Gene Biological form and function is created from and is passed on to the next generation by genes, which are the primary units of inheritance. Physiological adaption to an organism's environment cannot be coded into its genes and cannot be inherited by its offspring (see Lamarckism ). Remarkably, widely different organisms, including bacteria, plants, animals, and fungi, all share the same basic machinery that copies and transcribes DNA into proteins. For example, bacteria with inserted human DNA will correctly yield the corresponding human protein. The total complement of genes in an organism or cell is known as its Genome which is stored on one or more Chromosomes . A chromosome is a single, long DNA strand on which thousands of genes, depending on the organism, are encoded. When a gene is active, the DNA code is Transcribed into an RNA copy of the gene's information. A Ribosome then Translates the RNA into a structural Protein or Catalytic Protein . Homeostasis See Also: 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 exists at the cellular level, for example cells maintain a stable internal acidity ( PH ); and at the level of the organism, for example Warm-blooded animals maintain a constant internal body temperature. Homeostasis is a term that is also used in association with Ecosystems , for example, the atmospheric concentration of Carbon Dioxide on Earth has been regulated by the concentration of plant life on Earth because Plants remove more Carbon Dioxide from the atmosphere during the daylight hours than they emit to the atmosphere at night. Tissues and Organs can also maintain homeostasis. RESEARCH See Also: List of biology disciplines Structural depicting the various Organelle s and structures.]] See Also: 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 Physiological properties of Cells , as well as their Behavior s, interactions, and Environment . This is done both on a Microscopic and Molecular level. Cell biology researches both single-celled organisms like 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. 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. 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 Chemical Structure of particular DNA Molecule s. Developmental biology studies the process by which organisms grow and develop. Originating in Embryology , modern developmental biology studies the genetic control of Cell Growth , Differentiation , and " Morphogenesis ," which is the process that gives rise to Tissues , Organs , 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 ''. Physiological See Also: 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 systems in animals, such as the 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 . Evolution 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.]] See Also: Evolutionary biology Evolution Evolutionary synthesis Natural selection Evolution 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 Organism s such as Mammalogy , Ornithology , Botany , 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 . Up into the 19th Century , it was believed that life forms were being continuously created under certain conditions (see Spontaneous Generation ). This misconception was challenged by William Harvey 's diction that "all life 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 shares a common descent if they share a common ). The two major traditional taxonomically-oriented disciplines are Botany and Zoology . Botany is the scientific study of Plant s. 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 Animal s, 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. Taxonomy of All Living Things , based on RRNA Gene data, showing the separation of the three domains 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.]] See Also: Taxonomy 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 classification 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:4 : Monera -- Protist a -- Fungi -- Plant ae -- Animal ia However, many scientists now consider this five-kingdom system to be outdated. Modern alternative classification systems generally begin with the Three-domain System :5 : Archaea (originally Archaebacteria) -- Bacteria (originally Eubacteria) -- Eukarya 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 separately classified. The order is: # Domain # Kingdom # Phylum # Class # Order # Family # Genus # Species The scientific name of an organism is obtained from its genus and species. For example, humans would be listed as '' Homo Sapiens ''. ''Homo'' would be the genus and ''sapiens'' is the species. Whenever writing the scientific name of an organism, it is proper to capitalize the first letter in the genus and put all of the species in lowercase; in addition the entire term would be put in italics or underlined. 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 Metabolic activity: : Viruses -- Viroid s -- Prion s 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 Virus CInternational Code Of Virus Classification And Nomenclature (ICVCN) remains outside the BioCode. Environmental See Also: Ecology Ethology Behavior Biogeography Ecology studies the distribution and abundance of Living Organisms , and the interactions between organisms and their 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 Ecology , 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 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. Biogeography studies the spatial distribution of organisms on the Earth , focusing on topics like Plate Tectonics , Climate Change , dispersal and migration, and Cladistics . Every living thing interacts with other organisms and its 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 h. For any given species, Behavior s can be Co-operative , Aggressive , Parasitic or Symbiotic . Matters become more complex when two or more different species interact in an Ecosystem . Studies of this type are the province of Ecology . HISTORY See Also: History of biology History of medicine Although the concept of '' Biology '' 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.67 Over the 18th and 19th centuries, biological sciences such as Botany and Zoology became increasingly professional Scientific Discipline s. 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 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.89 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 ''organismal biology''—the fields that deal with whole organisms and groups of organisms—and the fields related to '' Cellular and Molecular Biology ''. 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.10111213 SEE ALSO : ''Main lists: List Of Biology Topics , List Of Basic Biology Topics and List Of Biologists '' REFERENCES FURTHER READING EXTERNAL LINKS
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