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History of biology

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The history of biology traces man's understanding of the living world from the earliest recorded history to modern times. Though the concept of biology as a single coherent field of knowledge only arose in the 19th century, the biological sciences emerged from traditions of medicine and natural history reaching back to the ancient Greeks (particularly Galen and Aristotle, respectively).

During the Renaissance and Age of Discovery, renewed interest in empiricism as well as the rapidly increasing number of known organisms led to significant developments in biological thought; Vesalius inaugurated the rise of experimentation and careful observation in physiology, and a series of naturalists culminating with Linnaeus and Buffon began to create a conceptual framework for analyzing the diversity of life and the fossil record, as well as the development and behavior of plants and animals. The growing importance of natural theology—partly a response to the rise of mechanical philosophy—was also an important impetus for the growth of natural history (though it also further entrenched the argument from design).

In the 18th century many fields of science—including botany, zoology, and geology—began to professionalize, forming the precursors of scientific disciplines in the modern sense (though the process would not be complete until the late 1800s). Lavoisier and other physical scientists began to connect the animate and inanimate worlds through the techniques and theory of physics and chemistry. Into the 19th century, explorer-naturalists such as Alexander von Humboldt tried to elucidate the interactions between organisms and their environment, and the ways these relationships depend on geography—creating the foundations for biogeography, ecology and ethology. Many naturalists began to reject essentialism and seriously consider the possibilities of extinction and the mutability of species. These developments, as well as the results of new fields such as embryology and paleontology, were synthesized in Darwin's theory of evolution by natural selection. The end of the 19th century saw debates over spontaneous generation and the rise of the germ theory of disease and the fields of cytology, bacteriology and physiological chemistry, though the problem of inheritance was still a mystery.

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 led to the "neo-Darwinian synthesis" and the rise of the discipline of evolutionary biology. New biological disciplines developed rapidly, especially after Watson and Crick discovered the structure of DNA in 1953. Following the cracking of the genetic code and the establishment of the Central Dogma, biology has largely split between organismal biology—consisting of ecology, ethology, systematics, paleontology, evolutionary biology, developmental biology, and other disciplines that deal with whole organisms or groups of organisms—and the constellation of disciplines related to molecular biology—including cell biology, biophysics, biochemistry, neuroscience, immunology, and many other overlapping subjects.

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Etymology

The word biology is formed by combining the Greek βίος (bios), meaning "life", and the suffix '-logy', meaning "science of", "knowledge of", "study of", based on the Greek verb λεγειν, 'legein' = "to select", "to gather" (cf. the noun λόγος, 'logos' = "word"). The term "biology" in its modern sense appears to have been introduced independently by :

The word itself 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.

Before biology, there were several terms used for study of animals and plants. Natural history referred to the descriptive aspects of biology, though it also included mineralogy and other non-biological fields; from the Middle Ages through the Renaissance, the unifying framework of natural history was the scala naturae or Great Chain of Being. Natural philosophy and natural theology encompassed the conceptual basis of plant and animal life, dealing with problems of why organisms exist and behave the way they do, though these subjects also included what is now geology, physics, chemistry, and astronomy. Physiology and (botanical) pharmacology were the province of medicine. Botany, zoology, and (in the case of fossils) geology replaced natural history and natural philosophy in the 18th and 19th century before biology was widely adopted.

Ancient and medieval knowledge

Before the 5th century

From early times, perhaps predating the appearance of modern humans, people must have had and passed on knowledge about plants and animals to increase their chances of survival. For example, they had to know how to avoid (or sometimes use) poisonous plants and animals and how to track, capture, and butcher different species of animals. They had to know which plants could be prepared to make good nets or baskets. In this sense, biology predates the written history of humans.

Agriculture requires specialised knowledge on plants and animals. Ancient Oriental people knew about the pollination of date palm from a very early point of time. In Mesopotamia they knew that pollen could be used in fertilizing plants. A business contract of the Hammurabi period (c. 1800 BCE) mentions flowers of the date palm as an article of commerce.

In India texts described some aspects of bird life. In Egypt the metamorphosis of insects and frogs was described. Egyptians and Babylonians also knew of anatomy and physiology in various forms. In Mesopotamia, animals were sometimes kept in what can be described as the first zoological gardens.

However, superstition often blended with facts. In Babylon and Assyria organs of animals were used in prediction, and in Egypt medicine included a large amount of mysticism.

Aristotle (sculpture)
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Aristotle (sculpture)

In the Ancient Greek and Hellenistic worlds scholars became more interested in empiricism. Aristotle is one of the most prolific natural philosophers of Antiquity. He made countless observations of nature, especially the habits and attributes of plants and animals in the world around him, which he devoted considerable attention to categorizing. Aristotle's successor, Theophrastus, wrote a series of books on botany, History of Plants, which survived as the most important contribution of antiquity to botany, even into the Middle Ages.

In ancient Rome, Pliny the Elder was known for his knowledge of plants and nature. Later, Claudius Galen became a pioneer in medicine and anatomy.

Medieval knowledge

The decline of the Roman Empire led to the disappearance or destruction of much knowledge. This time is often called the dark ages. However, some people who dealt with medical issues still studied plants and animals as well. In Byzantium and the Islamic world, natural philosophy was kept alive. Many of the Greek works were translated into Arabic and many of the works of Aristotle were preserved. Of the Arab biologists, al-Jahiz, who died about 868, is particularly noteworthy. He wrote Kitab al Hayawan (Book of animals). In the 1200's the German scholar named Albertus Magnus wrote De vegetabilibus, seven books, and De animalibus, 26 books. He was particularly interested in plant propagation and reproduction and discussed in some detail the sexuality of plants and animals. He was also, by the way, among the teachers of Thomas Aquinas.

Persian and Islamic biology

Persia and other Islamic areas became important in the development of science. Based on Greek and Indian science and connected to Europe they were in a good position to help science develop. There were also Arab and Turkish scientists but the most important ones were Persians. Avicenna (commemorated in the genus Avicennia) was very important in biology and recorded many findings. He is sometimes regarded as the father of modern medicine. Rhazes was also very important and he was also a good biologist.

The Renaissance

Albrecht Dürer's woodcut of a rhinoceros, an animal he had never actually seen
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Albrecht Dürer's woodcut of a rhinoceros, an animal he had never actually seen

Interestingly, as many visual artists were interested in the bodies of animals and humans, they studied the physiology in detail. Such comparisons as that between a horse leg and a human leg were made. Otto Brunfels, Hieronymus Bock (also known as Hieronymus Tragus) and Leonhart Fuchs were three men who wrote books about wild plants; they have been referred to as the fathers of German botany. Books about animals were also made, such as those by Conrad Gesner, illustrated by, among others, Albrecht Dürer.

Seventeenth and eighteenth century developments

Cabinets of curiosities, such as that of Ole Worm, were centers of biological knowledge in the early modern period, bringing organisms from across the world together in one place.  Before the Age of Exploration, naturalists had little idea of the sheer scale of biological diversity.
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Cabinets of curiosities, such as that of Ole Worm, were centers of biological knowledge in the early modern period, bringing organisms from across the world together in one place. Before the Age of Exploration, naturalists had little idea of the sheer scale of biological diversity.

In 1628 William Harvey explained that blood circulates throughout the body, and is pumped by the heart. Antony van Leeuwenhoek's invention of the microscope in about 1650 opened up the micro-world of biology. The History of Plants was greatly extended, almost into an encyclopedia, by Giovanni Bodeo da Stapel in 1644 AD. In 1658 Jan Swammerdam was the first to observe and describe red blood cells, while Leeuwenhoek was the first to describe spermatozoa, bacteria and infusoria in the 1670's and 1680's. By the 1690's plants were, like animals, known to be sexual, having stamens and pistils.

Systematizing, naming and classifying dominated biology throughout much of the 17th and 18th centuries. Carolus Linnaeus published a basic taxonomy for the natural world in 1735, and in the 1750's introduced scientific names for all his species. The discovery and description of new species, and collecting specimens became a widespread passion of scientific gentlemen.

Nineteenth century: the emergence of biological disciplines

Up through the nineteenth century, the scope of biology was largely divided between medicine, which investigated questions of form and function, and natural history, which was concerned with the diversity of life and interactions among different forms of life and between life and non-life. By 1900, much of these domains overlapped, while natural history and (and its counterpart natural philosophy) had largely given way to more specialized scientific disciplines—cytology, bacteriology, morphology, embryology, geography, and geology.

Physiology

Wöhler showed In 1828 that organic molecules, such as urea, can be created by synthetic means that do not involve life, and thus provided a powerful argument against vitalism. The first enzyme, diastase, was described in 1833, and scientists began to explore connections between chemistry and biology.

Advances in microscopy also had a profound impact on biological thinking: in 1839, Schleiden and Schwann proposed the cell theory—that the basic unit of organisms is the cell and all cells come from preexisting cells. The cytologist Walther Flemming in 1882 was the first to demonstrate that the discrete stages of mitosis were not an artifact of staining, but occurred in living cells, and moreover, that chromosomes doubled in number just before the cell divided and a daughter cell was produced. In 1887 August Weismann proposed that the chromosome number must then be halved in the case of the sexual cells, the gametes. This was shortly proved to be the case and the process of meiosis began to be understood.

By the mid 1850's the miasma theory of disease was largely superseded by the germ theory of disease, creating extensive interest in microorganisms and their interactions with other forms of life. By the 1880's, bacteriology was becoming a coherent discipline, especially through the work of Robert Koch, who introduced methods for growing pure cultures on agar gels containing specific nutrients in Petri dishes. The long-held idea that living organisms could easily originate from nonliving matter (spontaneous generation) was attacked in a series of experiments carried out by Louis Pasteur, while debates over vitalism vs. mechanism continued apace.

Natural history and natural philosophy

In the course of his travels, Alexander von Humboldt mapped the distribution of plants across landscapes and recorded a variety of physical conditions such as pressure and temperature.
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In the course of his travels, Alexander von Humboldt mapped the distribution of plants across landscapes and recorded a variety of physical conditions such as pressure and temperature.

Widespread travel by naturalists in the early- to mid-nineteenth century resulted in a wealth of new information about the diversity and distribution of living organisms. Of particular importance was the work of Alexander von Humboldt, which analyzed the relationship between organisms and their environment using the quantitative approaches of natural philosophy (i.e., physics and chemisty). Humboldt's work laid the foundations of biogeography and inspired several generations of scientists.[1]

The emerging discipline of geology also brought natural history and natural philosophy closer together; the establishment of the stratigraphic column linked the spacial distribution of organisms to the temporal distribution, a key precursors to concepts of evolution. Georges Cuvier and others made great strides in comparative anatomy and paleontology in the late 1790s and early 1800s. Cuvier helped establish that some fossils were remains of animal species that had become extinct—rather than being still alive somewhere else in the world, as had been widely believed. Gideon Mantell, William Buckland, Mary Anning, and Richard Owen among others helped establish that there had been an 'age of reptiles' that had preceded even the prehistoric mammals. These discoveries captured the public imagination and focused attention on the history of life on earth.[2] Most of these geologists held to catastrophism, but Charles Lyell's influential Principles of Geology (1830) introduced uniformitarianism, a theory that explained the geological past and present on equal terms.[3]

Charles Darwin's first sketch of an evolutionary tree from his First Notebook on Transmutation of Species (1837)
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Charles Darwin's first sketch of an evolutionary tree from his First Notebook on Transmutation of Species (1837)

The first to propose an evolutionary theory was Jean-Baptiste Lamarck; based on the inheritance of acquired characteristics (an inheritance mechanism that was widely accepted until the 20th century), it described a chain of development stretching from the lowliest microbe to humans.[4] The British naturalist Charles Darwin, combining the biogeographical approach of Humboldt, the uniformitarian geology of Lyell, and his own morphological expertise, created a more successful evolutionary theory based on natural selection.[5] Though natural selection would not be accepted as the primary mechanism of evolution until well into the 20th century, most scientists were convinced of evolution and common descent by the end of the 19th century.[6]

The study of scientific study of heredity grew rapidly in the wake of Darwin's On the Origin of Species (1859) with the work of Francis Galton and the biometricians. The origin of genetics is usually traced to the 1866 work of the Austrian monk Gregor Mendel, who would later be credited with the laws of inheritance. However, his work was not recognized as significant until 35 years afterward. In the meantime, a variety of theories of inheritance (based on pangenesis, orthogenesis, or other mechanisms) were debated and investigated vigorously.[7] Embryology and ecology also became central biological fields, especially as linked to evolution and popularized in the work of Ernst Haeckel.

Twentieth century biological sciences

At the beginning of the 20th century, biological research was largely a professional endeavour. However, most work was still in the natural history mode, which emphasized morhphological and phylogenetic analysis over experiment-based causal explanations. However, anti-vitalist experimental physiologists and embryologists, especially in Europe, were increasingly influential. The tremendous success of experimental approaches to development, heredity, and metabolism in the 1900's and 1910's demonstrated the power of experimentation in biology. In the following decades, experimental work replaced natural history as the dominant mode of research.

Classical genetics and evolutionary synthesis

Thomas Hunt Morgan's illustration of crossing over, part of the Mendelian-chromosome theory of heredity
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Thomas Hunt Morgan's illustration of crossing over, part of the Mendelian-chromosome theory of heredity

1900 marked the so-called rediscovery of Mendel: Hugo de Vries, Carl Correns, and Erich von Tschermak independently arrived at Mendel's laws (which were not actually present in Mendel's work).[8] Soon after, cytologists proposed that chromosomes were the hereditary material. Between 1910 and 1915, Thomas Hunt Morgan and his fly lab forged these two ideas—both controversial—into the "Mendelian-chromosome theory" of heredity. They quantified the phenomon of genetic linkage and postulated that genes reside on chromosomes like beads on string; they hypothesized crossing over to explain linkage and contructed genetic maps of the fruit fly Drosophila melanogaster, which became a widely used model organism.[9]

Building on his work on heredity and hybridization, Hugo de Vries proposed a mutation theory of evolution, which was widely accepted in the early 20th century. Lamarckism also had many adherents. Darwinism was seen as incompatible with the continuosly-variable traits studied by biometricians, which seemed only partially heritable. In the 1920's and 1930's—following the acceptance of the Mendelian-chromosome theory—a unification of the idea of evolution by natural selection with Mendelian genetics produced the modern synthesis; inheritance of acquired characters was rejected, while mutationism gave way as genetic theories matured. These ideas continued to be developed in the discipline of population genetics and in the second half of the century began to be applied in the new discipline of the genetics of behavior, sociobiology, and, especially in humans, evolutionary psychology.

By the end of the 19th century all of the major pathways of drug metabolism had been discovered. In the early decades of the twentieth century the role of minor components of foods in human nutrition, the vitamins, began to be isolated and synthesized. Then in the 1920's and 1930's the metabolic pathways of life, such as the citric acid cycle and glycolysis, finally began to be worked out by biochemists. This work continued to be very actively pursued for the rest of the century and into the next. During 1939-1941 Fritz Lipmann showed that ATP is the universal carrier of energy in the cell and then in the mid-1950's the power generators of the cell, the mitochondria, also began to be understood.

Microbiology, biochemistry, and molecular biology

Oswald Avery conclusively showed in 1943 that DNA was the genetic material of the chromosome, not its protein. By 1953 James Watson and Francis Crick showed that the structure of DNA was a double helix and showed its probable connection to replication. The nature of the genetic code was unraveled experimentally starting with the work of Nirenberg, Khorana and others in the late 1950's. This discovery, and others, especially the discovery of the first restriction enzyme in 1968 and PCR in 1983 gave rise to the vigorous science that we know today as molecular biology.

In 1965 it was shown that normal cells in culture divide only a fixed number of times (the Hayflick Limit) then aged and died. About the same time, stem cells were shown to be exceptions to this rule and began to be studied in earnest. Toward the end of the century, totipotent stem cells came to be recognized as crucial for the understanding of developmental biology and raised hopes for new medical applications. In 1983 the unity of much of the morphogenesis of organisms from fertilized egg to adult began to be unraveled by the discovery of the homeobox genes, first in the fruit fly, then in other insects and animals, including man.

Starting in 1990 an important mechanism of gene regulation, RNA interference began to be understood and became an important laboratory technique to knockdown genes in order to determine their function in model organisms. In 2006 a large international consortium began a collaborative effort to enable researchers to conveniently obtain mice that have any one of its approximately 20000 genes knocked out. This US$100 million effort is the largest biological research endeavor since the human genome project.

The study of organisms, their reproduction, and the functions of their organs had come to be the study of molecules. Reductionism was triumphant. Even the methods of scientific classification of organisms, especially cladistics, began in the last quarter of the century to use RNA and DNA sequences as characters. By the mid 1980's even the overall division of the tree of life into three domains (as opposed to the classical two), the Archaea, the Bacteria, and the Eukarya, based on Woese's pioneering work on 16S rRNA sequencing, became generally accepted in the scientific community.

Biotechnology

While cloning in plants was known for millennia it was only in 1951 that the first animal, the tadpole, was cloned by nuclear transfer. Dolly, the sheep was cloned by transfer of a mature somatic cell nucleus into an enucleated oocyte in 1997. Within a few years, several other animals, including dogs, cats, horses and cattle were cloned by similar methods.

The largest, most costly single biological study ever undertaken, the Human genome project began in 1988 under the leadership of James Watson, and a first draft of the human DNA sequence was announced in 2000. By 2003 99% of the genome had been sequenced to an accuracy of one part in ten thousand. The HapMap project to determine patterns of differences in the human genome began in 2002 and by 2005 completed its first phase work by of discovering on the order of one million SNPs in 270 people sampled from four distinct populations of people: Han Chinese, Japanese, Yoruba Nigerians, and Northern Europeans. The advent of whole-genome sequencing and surveys of their variation in different populations (races), together with new statistical methods, permitted researchers by 2006 to systematically identify candidate loci for recent natural selection during evolution in humans. Some of these genes were also shown to be ancestry-informative markers which came to be used in genealogical studies and to understand ancient human migrations.

The first genome of a plant model organism, Arabidopsis thaliana was sequenced in 2000. Dozens of bacteria, the mouse, the nematode Caenorhabditis elegans and other model organisms were sequenced and their genes mapped, often by large international collaborations. The first decade of the twenty-first century saw the rise of proteomics, computational biology and bioinformatics, with an emphasis on huge databases of experimentally derived data, all connected by the Internet and available to researchers everywhere, which has fundamentally changed the structure of the science of biology itself.

Ecology, ethology, and environmental science

References

  1. ^ Bowler, The Earth Encompassed, pp 204-211
  2. ^ Bowler, The Earth Encompassed, pp 211-220
  3. ^ Bowler, The Earth Encompassed, pp 237-247
  4. ^ Mayr, The Growth of Biological Thought, pp 343-357
  5. ^ 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"
  6. ^ Larson, Evolution, chapter 5: "Ascent of Evolutionism"; see also: Bowler, The Eclipse of Darwinism
  7. ^ Mayr, The Growth of Biological Thought, pp 693-710
  8. ^ Randy Moore, "The 'Rediscovery' of Mendel's Work", Bioscene, Volume 27(2), May 2001.
  9. ^ Garland Allen, Thomas Hunt Morgan: The Man and His Science (1978), chapter 5.
  • Allen, Garland Thomas Hunt Morgan: The Man and His Science. Princeton University Press: Princeton, 1978. ISBN 0-691-08200-6
  • Asimov, Isaac Asimov's Biographical Encyclopedia of Science and Technology: The Lives & Achievements of 1510 Great Scientists from Ancient Times to the Present Revised second edition, Doubleday (1982) ISBN 0-385-17771-2.
  • Bowler, Peter J. The Earth Encompassed: A History of the Environmental Sciences. W. W. Norton & Company: New York, 1992. ISBN 0-393-32080-4
  • Bowler, Peter J. The Eclipse of Darwinism: Anti-Darwinian Evolution Theories in the Decades around 1900. The Johns Hopkins University Press: Baltimore, 1983. ISBN 0801829321
  • Coleman, William. Biology in the Nineteenth Century: Problems of Form, Function, and Transformation. Cambridge University Press: New York, 1977. ISBN 0-521-29293-X
  • Larson, Edward J. Evolution: The Remarkable History of a Scientific Theory. The Modern Library: New York, 2004. ISBN 0-679-64288-9
  • Mayr, Ernst. The Growth of Biological Thought: Diversity, Evolution, and Inheritance. The Belknap Press of Harvard University Press: Cambridge, Massachusetts, 1982. ISBN 0-674-36445-7

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