The philosopher Aristotle was the most influential scholar of the living world from classical antiquity. Though his early work in natural philosophy was speculative, Aristotle's later biological writings were more empirical, focusing on biological causation and the diversity of life. 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.
In all, Aristotle classified animal species, and dissected at least He believed that intellectual purposes, formal causes , guided all natural processes. Aristotle, and nearly all Western scholars after him until the 18th century, believed that creatures were arranged in a graded scale of perfection rising from plants on up to humans: the scala naturae or Great Chain of Being.
Many of Theophrastus' names survive into modern times, such as carpos for fruit, and pericarpion for seed vessel. Dioscorides wrote a pioneering and encyclopaedic pharmacopoeia , De Materia Medica , incorporating descriptions of some plants and their uses in medicine. Pliny the Elder , in his Natural History , assembled a similarly encyclopaedic account of things in nature, including accounts of many plants and animals.
A few scholars in the Hellenistic period under the Ptolemies —particularly Herophilus of Chalcedon and Erasistratus of Chios —amended Aristotle's physiological work, even performing dissections and vivisections. Though a few ancient atomists such as Lucretius challenged the teleological Aristotelian viewpoint that all aspects of life are the result of design or purpose, teleology and after the rise of Christianity , natural theology would remain central to biological thought essentially until the 18th and 19th centuries. Ernst W. Mayr argued that "Nothing of any real consequence happened in biology after Lucretius and Galen until the Renaissance.
The decline of the Roman Empire led to the disappearance or destruction of much knowledge, though physicians still incorporated many aspects of the Greek tradition into training and practice. In Byzantium and the Islamic world, many of the Greek works were translated into Arabic and many of the works of Aristotle were preserved.
The rise of European universities , though important for the development of physics and philosophy, had little impact on biological scholarship.
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The European Renaissance brought expanded interest in both empirical natural history and physiology. In , Andreas Vesalius inaugurated the modern era of Western medicine with his seminal human anatomy treatise De humani corporis fabrica , which was based on dissection of corpses. Vesalius was the first in a series of anatomists who gradually replaced scholasticism with empiricism in physiology and medicine, relying on first-hand experience rather than authority and abstract reasoning. Via herbalism , medicine was also indirectly the source of renewed empiricism in the study of plants.
Otto Brunfels , Hieronymus Bock and Leonhart Fuchs wrote extensively on wild plants, the beginning of a nature-based approach to the full range of plant life. Alchemists subjected organic matter to chemical analysis and experimented liberally with both biological and mineral pharmacology. Systematizing , naming and classifying dominated natural history throughout much of the 17th and 18th centuries. Carl Linnaeus published a basic taxonomy for the natural world in variations of which have been in use ever since , and in the s introduced scientific names for all his species.
Though he was opposed to evolution, Buffon is a key figure in the history of evolutionary thought ; his work would influence the evolutionary theories of both Lamarck and Darwin.
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The discovery and description of new species and the collection of specimens became a passion of scientific gentlemen and a lucrative enterprise for entrepreneurs; many naturalists traveled the globe in search of scientific knowledge and adventure. Extending the work of Vesalius into experiments on still living bodies of both humans and animals , William Harvey and other natural philosophers investigated the roles of blood, veins and arteries. Harvey's De motu cordis in was the beginning of the end for Galenic theory, and alongside Santorio Santorio 's studies of metabolism, it served as an influential model of quantitative approaches to physiology.
In the early 17th century, the micro-world of biology was just beginning to open up. A few lensmakers and natural philosophers had been creating crude microscopes since the late 16th century, and Robert Hooke published the seminal Micrographia based on observations with his own compound microscope in But it was not until Antonie van Leeuwenhoek 's dramatic improvements in lensmaking beginning in the s—ultimately producing up to fold magnification with a single lens—that scholars discovered spermatozoa , bacteria , infusoria and the sheer strangeness and diversity of microscopic life.
Similar investigations by Jan Swammerdam led to new interest in entomology and built the basic techniques of microscopic dissection and staining. As the microscopic world was expanding, the macroscopic world was shrinking. Botanists such as John Ray worked to incorporate the flood of newly discovered organisms shipped from across the globe into a coherent taxonomy, and a coherent theology natural theology. Although Steno's ideas about fossilization were well known and much debated among natural philosophers, an organic origin for all fossils would not be accepted by all naturalists until the end of the 18th century due to philosophical and theological debate about issues such as the age of the earth and extinction.
Up through the 19th century, the scope of biology was largely divided between medicine, which investigated questions of form and function i. By , much of these domains overlapped, while natural history and its counterpart natural philosophy had largely given way to more specialized scientific disciplines— cytology , bacteriology , morphology , embryology , geography , and geology. Widespread travel by naturalists in the early-to-midth 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 i. Humboldt's work laid the foundations of biogeography and inspired several generations of scientists. The emerging discipline of geology also brought natural history and natural philosophy closer together; the establishment of the stratigraphic column linked the spatial distribution of organisms to their temporal distribution, a key precursor to concepts of evolution. Georges Cuvier and others made great strides in comparative anatomy and paleontology in the late s and early 19th century.
In a series of lectures and papers that made detailed comparisons between living mammals and fossil remains Cuvier was able to establish that the fossils were remains of species that had become extinct —rather than being remains of species still alive elsewhere in the world, as had been widely believed. These discoveries captured the public imagination and focused attention on the history of life on earth.
The most significant evolutionary theory before Darwin's was that of 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. The publication of Darwin's theory in On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life is often considered the central event in the history of modern biology.
Darwin's established credibility as a naturalist, the sober tone of the work, and most of all the sheer strength and volume of evidence presented, allowed Origin to succeed where previous evolutionary works such as the anonymous Vestiges of Creation had failed. Most scientists were convinced of evolution and common descent by the end of the 19th century. However, natural selection would not be accepted as the primary mechanism of evolution until well into the 20th century, as most contemporary theories of heredity seemed incompatible with the inheritance of random variation.
Wallace, following on earlier work by de Candolle , Humboldt and Darwin, made major contributions to zoogeography. Because of his interest in the transmutation hypothesis, he paid particular attention to the geographical distribution of closely allied species during his field work first in South America and then in the Malay archipelago. His key question, as to why the fauna of islands with such similar climates should be so different, could only be answered by considering their origin.
In he wrote The Geographical Distribution of Animals , which was the standard reference work for over half a century, and a sequel, Island Life , in that focused on island biogeography.
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He extended the six-zone system developed by Philip Sclater for describing the geographical distribution of birds to animals of all kinds. His method of tabulating data on animal groups in geographic zones highlighted the discontinuities; and his appreciation of evolution allowed him to propose rational explanations, which had not been done before. The scientific study of heredity grew rapidly in the wake of Darwin's Origin of Species with the work of Francis Galton and the biometricians. The origin of genetics is usually traced to the work of the 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. Most of the 19th century work on heredity, however, was not in the realm of natural history, but that of experimental physiology.
Over the course of the 19th century, the scope of physiology expanded greatly, from a primarily medically oriented field to a wide-ranging investigation of the physical and chemical processes of life—including plants, animals, and even microorganisms in addition to man. Living things as machines became a dominant metaphor in biological and social thinking. Advances in microscopy also had a profound impact on biological thinking. In the early 19th century, a number of biologists pointed to the central importance of the cell.
In and , Schleiden and Schwann began promoting the ideas that 1 the basic unit of organisms is the cell and 2 that individual cells have all the characteristics of life , though 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 s most biologists accepted all three tenets of what came to be known as cell theory. Cell theory led biologists to re-envision individual organisms as interdependent assemblages of individual cells. Scientists in the rising field of cytology , armed with increasingly powerful microscopes and new staining methods, soon found that even single cells were far more complex than the homogeneous fluid-filled chambers described by earlier microscopists.
Robert Brown had described the nucleus in , and by the end of the 19th century cytologists identified many of the key cell components: chromosomes , centrosomes mitochondria , chloroplasts , and other structures made visible through staining.
Between and Walther Flemming described the discrete stages of mitosis, showing that they were not artifacts 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. Much of the research on cell reproduction came together in August Weismann 's theory of heredity: he identified the nucleus in particular chromosomes as the hereditary material, proposed the distinction between somatic cells and germ cells arguing that chromosome number must be halved for germ cells, a precursor to the concept of meiosis , and adopted Hugo de Vries 's theory of pangenes.
Weismannism was extremely influential, especially in the new field of experimental embryology. By the mids 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 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. In chemistry, one central issue was the distinction between organic and inorganic substances, especially in the context of organic transformations such as fermentation and putrefaction. Since Aristotle these had been considered essentially biological vital processes. Cell extracts "ferments" that could effect chemical transformations were discovered, beginning with diastase in By the end of the 19th century the concept of enzymes was well established, though equations of chemical kinetics would not be applied to enzymatic reactions until the early 20th century.
Physiologists such as Claude Bernard explored through vivisection and other experimental methods the chemical and physical functions of living bodies to an unprecedented degree, laying the groundwork for endocrinology a field that developed quickly after the discovery of the first hormone , secretin , in , biomechanics , and the study of nutrition and digestion. The importance and diversity of experimental physiology methods, within both medicine and biology, grew dramatically over the second half of the 19th century. The control and manipulation of life processes became a central concern, and experiment was placed at the center of biological education.
At the beginning of the 20th century, biological research was largely a professional endeavour. Most work was still done in the natural history mode, which emphasized morphological 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 s and s demonstrated the power of experimentation in biology. In the following decades, experimental work replaced natural history as the dominant mode of research. In the early 20th century, naturalists were faced with increasing pressure to add rigor and preferably experimentation to their methods, as the newly prominent laboratory-based biological disciplines had done.
Ecology had emerged as a combination of biogeography with the biogeochemical cycle concept pioneered by chemists; field biologists developed quantitative methods such as the quadrat and adapted laboratory instruments and cameras for the field to further set their work apart from traditional natural history. Zoologists and botanists did what they could to mitigate the unpredictability of the living world, performing laboratory experiments and studying semi-controlled natural environments such as gardens; new institutions like the Carnegie Station for Experimental Evolution and the Marine Biological Laboratory provided more controlled environments for studying organisms through their entire life cycles.
The ecological succession concept, pioneered in the s and s by Henry Chandler Cowles and Frederic Clements , was important in early plant ecology. Evelyn Hutchinson 's studies of the biogeography and biogeochemical structure of lakes and rivers limnology and Charles Elton's studies of animal food chains were pioneers among the succession of quantitative methods that colonized the developing ecological specialties. Ecology became an independent discipline in the s and s after Eugene P. Odum synthesized many of the concepts of ecosystem ecology , placing relationships between groups of organisms especially material and energy relationships at the center of the field.
In the s, as evolutionary theorists explored the possibility of multiple units of selection , ecologists turned to evolutionary approaches. In population ecology , debate over group selection was brief but vigorous; by , most biologists agreed that natural selection was rarely effective above the level of individual organisms. The evolution of ecosystems, however, became a lasting research focus. Ecology expanded rapidly with the rise of the environmental movement; the International Biological Program attempted to apply the methods of big science which had been so successful in the physical sciences to ecosystem ecology and pressing environmental issues, while smaller-scale independent efforts such as island biogeography and the Hubbard Brook Experimental Forest helped redefine the scope of an increasingly diverse discipline.
Between and , Thomas Hunt Morgan and the " Drosophilists " in his fly lab forged these two ideas—both controversial—into the "Mendelian-chromosome theory" of heredity. Hugo de Vries tried to link the new genetics with evolution; building on his work with heredity and hybridization , he proposed a theory of mutationism , which was widely accepted in the early 20th century. Lamarckism , or the theory of inheritance of acquired characteristics also had many adherents. Darwinism was seen as incompatible with the continuously variable traits studied by biometricians , which seemed only partially heritable.
In the s and s—following the acceptance of the Mendelian-chromosome theory— the emergence of the discipline of population genetics , with the work of R. Fisher , J. Haldane and Sewall Wright , unified the idea of evolution by natural selection with Mendelian genetics , producing the modern synthesis. The inheritance of acquired characters was rejected, while mutationism gave way as genetic theories matured. In the second half of the century the ideas of population genetics began to be applied in the new discipline of the genetics of behavior, sociobiology , and, especially in humans, evolutionary psychology.
In the s W. Hamilton and others developed game theory approaches to explain altruism from an evolutionary perspective through kin selection. The possible origin of higher organisms through endosymbiosis , and contrasting approaches to molecular evolution in the gene-centered view which held selection as the predominant cause of evolution and the neutral theory which made genetic drift a key factor spawned perennial debates over the proper balance of adaptationism and contingency in evolutionary theory.
In the s Stephen Jay Gould and Niles Eldredge proposed the theory of punctuated equilibrium which holds that stasis is the most prominent feature of the fossil record, and that most evolutionary changes occur rapidly over relatively short periods of time. Raup led to a better appreciation of the importance of mass extinction events to the history of life on earth.
By the end of the 19th century all of the major pathways of drug metabolism had been discovered, along with the outlines of protein and fatty acid metabolism and urea synthesis.
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Improved laboratory techniques such as chromatography and electrophoresis led to rapid advances in physiological chemistry, which—as biochemistry —began to achieve independence from its medical origins. In the s and s, biochemists—led by Hans Krebs and Carl and Gerty Cori —began to work out many of the central metabolic pathways of life: the citric acid cycle , glycogenesis and glycolysis , and the synthesis of steroids and porphyrins. Between the s and s, Fritz Lipmann and others established the role of ATP as the universal carrier of energy in the cell, and mitochondria as the powerhouse of the cell.
Such traditionally biochemical work continued to be very actively pursued throughout the 20th century and into the 21st. Following the rise of classical genetics, many biologists—including a new wave of physical scientists in biology—pursued the question of the gene and its physical nature. Warren Weaver —head of the science division of the Rockefeller Foundation —issued grants to promote research that applied the methods of physics and chemistry to basic biological problems, coining the term molecular biology for this approach in ; many of the significant biological breakthroughs of the s and s were funded by the Rockefeller Foundation.
Like biochemistry, the overlapping disciplines of bacteriology and virology later combined as microbiology , situated between science and medicine, developed rapidly in the early 20th century. The development of standard, genetically uniform organisms that could produce repeatable experimental results was essential for the development of molecular genetics. After early work with Drosophila and maize , the adoption of simpler model systems like the bread mold Neurospora crassa made it possible to connect genetics to biochemistry, most importantly with Beadle and Tatum 's one gene-one enzyme hypothesis in Genetics experiments on even simpler systems like tobacco mosaic virus and bacteriophage , aided by the new technologies of electron microscopy and ultracentrifugation , forced scientists to re-evaluate the literal meaning of life ; virus heredity and reproducing nucleoprotein cell structures outside the nucleus "plasmagenes" complicated the accepted Mendelian-chromosome theory.
In their famous paper " Molecular structure of Nucleic Acids ", Watson and Crick noted coyly, "It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material. Between and , there were few known biological sequences—either DNA or protein—but an abundance of proposed code systems, a situation made even more complicated by expanding knowledge of the intermediate role of RNA. To actually decipher the code, it took an extensive series of experiments in biochemistry and bacterial genetics, between and —most importantly the work of Nirenberg and Khorana.
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In addition to the Division of Biology at Caltech , the Laboratory of Molecular Biology and its precursors at Cambridge , and a handful of other institutions, the Pasteur Institute became a major center for molecular biology research in the late s. A number of biochemists led by Frederick Sanger later joined the Cambridge lab, bringing together the study of macromolecular structure and function.
The late s to the early s was a period of intense research and institutional expansion for molecular biology, which had only recently become a somewhat coherent discipline. In what organismic biologist E. Wilson called "The Molecular Wars", the methods and practitioners of molecular biology spread rapidly, often coming to dominate departments and even entire disciplines. Resistance to the growing influence of molecular biology was especially evident in evolutionary biology. Protein sequencing had great potential for the quantitative study of evolution through the molecular clock hypothesis , but leading evolutionary biologists questioned the relevance of molecular biology for answering the big questions of evolutionary causation.
Departments and disciplines fractured as organismic biologists asserted their importance and independence: Theodosius Dobzhansky made the famous statement that " nothing in biology makes sense except in the light of evolution " as a response to the molecular challenge. The issue became even more critical after ; Motoo Kimura 's neutral theory of molecular evolution suggested that natural selection was not the ubiquitous cause of evolution, at least at the molecular level, and that molecular evolution might be a fundamentally different process from morphological evolution.
Biotechnology in the general sense has been an important part of biology since the late 19th century. With the industrialization of brewing and agriculture , chemists and biologists became aware of the great potential of human-controlled biological processes. In particular, fermentation proved a great boon to chemical industries. By the early s, a wide range of biotechnologies were being developed, from drugs like penicillin and steroids to foods like Chlorella and single-cell protein to gasohol —as well as a wide range of hybrid high-yield crops and agricultural technologies, the basis for the Green Revolution.
Biotechnology in the modern sense of genetic engineering began in the s, with the invention of recombinant DNA techniques. Beginning with the lab of Paul Berg in aided by EcoRI from Herbert Boyer 's lab, building on work with ligase by Arthur Kornberg 's lab , molecular biologists put these pieces together to produce the first transgenic organisms. Soon after, others began using plasmid vectors and adding genes for antibiotic resistance , greatly increasing the reach of the recombinant techniques. Wary of the potential dangers particularly the possibility of a prolific bacteria with a viral cancer-causing gene , the scientific community as well as a wide range of scientific outsiders reacted to these developments with both enthusiasm and fearful restraint.
Prominent molecular biologists led by Berg suggested a temporary moratorium on recombinant DNA research until the dangers could be assessed and policies could be created. This moratorium was largely respected, until the participants in the Asilomar Conference on Recombinant DNA created policy recommendations and concluded that the technology could be used safely. Following Asilomar, new genetic engineering techniques and applications developed rapidly.
DNA sequencing methods improved greatly pioneered by Frederick Sanger and Walter Gilbert , as did oligonucleotide synthesis and transfection techniques.
However, this was a more daunting task than molecular biologists had expected; developments between and showed that, due to the phenomena of split genes and splicing , higher organisms had a much more complex system of gene expression than the bacteria models of earlier studies. This marked the beginning of the biotech boom and with it, the era of gene patents , with an unprecedented level of overlap between biology, industry, and law. By the s, protein sequencing had already transformed methods of scientific classification of organisms especially cladistics but biologists soon began to use RNA and DNA sequences as characters ; this expanded the significance of molecular evolution within evolutionary biology, as the results of molecular systematics could be compared with traditional evolutionary trees based on morphology.
Following the pioneering ideas of Lynn Margulis on endosymbiotic theory , which holds that some of the organelles of eukaryotic cells originated from free living prokaryotic organisms through symbiotic relationships, even the overall division of the tree of life was revised. The unity of much of the morphogenesis of organisms from fertilized egg to adult began to be unraveled after the discovery of the homeobox genes, first in fruit flies, then in other insects and animals, including humans.
These developments led to advances in the field of evolutionary developmental biology towards understanding how the various body plans of the animal phyla have evolved and how they are related to one another. The Human Genome Project —the largest, most costly single biological study ever undertaken—began in under the leadership of James D. Watson , after preliminary work with genetically simpler model organisms such as E. Shotgun sequencing and gene discovery methods pioneered by Craig Venter —and fueled by the financial promise of gene patents with Celera Genomics — led to a public—private sequencing competition that ended in compromise with the first draft of the human DNA sequence announced in At the beginning of the 21st century, biological sciences converged with previously differentiated new and classic disciplines like Physics into research fields like Biophysics.
Advances were made in analytical chemistry and physics instrumentation including improved sensors, optics, tracers, instrumentation, signal processing, networks, robots, satellites, and compute power for data collection, storage, analysis, modeling, visualization, and simulations. These technology advances allowed theoretical and experimental research including internet publication of molecular biochemistry, biological systems , and ecosystems science.
This enabled worldwide access to better measurements, theoretical models, complex simulations, theory predictive model experimentation, analysis, worldwide internet observational data reporting , open peer-review, collaboration, and internet publication. New fields of biological sciences research emerged including Bioinformatics , Neuroscience , Theoretical biology , Computational genomics , Astrobiology and Synthetic Biology.
As far as biology as a whole is concerned, it was not until the late eighteenth and early nineteenth century that the universities became centers of biological research. From Wikipedia, the free encyclopedia. For the video game, see History of Biology video game. Big Think Edge For Business. Preview an Edge video. Sponsored by the Institute for Humane Studies Become an intellectual explorer: Master the art of conversation. Videos You should be skeptical when it comes to hyped-up AI.
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