1.
Caprella mutica
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Caprella mutica, commonly known as the Japanese skeleton shrimp, is a species of skeleton shrimp. They are relatively large caprellids, reaching a length of 50 mm. They are sexually dimorphic, with the males usually being larger than the females. They are characterized by their hairy first and second thoracic segments, body color ranges from green to red to blue, depending on the environment. They are omnivorous highly adaptable opportunistic feeders, in turn, they provide a valuable food source for fish, crabs, and other larger predators. They are usually found in colonies attached to submerged man-made structures, floating seaweed. C. mutica are native to shallow protected bodies of water in the Sea of Japan, in as little as 40 years, they have become an invasive species in the North Atlantic, North Pacific, and along the coasts of New Zealand. They are believed to have been introduced to these areas through the global maritime traffic. Outside of their range, C. mutica are often exclusively synanthropic, being found in large numbers in. Their ecological and economic impact as a species is unknown. Like all caprellid amphipods, Caprella mutica are characterized by slender bodies, C. mutica vary in coloration from translucent pale green, brown, cream, orange, deep red, purple, and even turquoise, depending on the substrate they are found in. The brood pouches of the females are speckled with red spots, a relatively large amphipod, C. mutica are sexually dimorphic with males considerably larger than females. Males average at a length of 25 to 30 mm, though specimens have been recorded to reach 50 mm in length, females, on the other hand, average at only 15 to 20 mm long. The body can be divided into three parts – the cephalon, the pereon, and the abdomen, the pereon comprises most of the length of the body. It is divided into seven segments known as pereonites, the rounded and smooth cephalon is fused to the first pereonite, while the highly reduced and almost invisible abdomen is attached to the posterior of the seventh pereonite. In males the first two pereonites are elongated, with the second pereonite being the longest of all the pereonites and they are densely covered with long setae, giving them a hairy appearance. The second pereonite also has two to three pairs of spines on the back, with a two pairs at the sides near the base of the limbs. The remaining pereonites lack the dense setae of the first two pereonites, the third pereonite has seven pairs of spines at the back while the fourth pereonite has eight pairs
2.
Biology
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Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, evolution, distribution, identification and taxonomy. Modern biology is a vast and eclectic field, composed of branches and subdisciplines. However, despite the broad scope of biology, there are certain unifying concepts within it that consolidate it into single, coherent field. In general, biology recognizes the cell as the unit of life, genes as the basic unit of heredity. It is also understood today that all organisms survive by consuming and transforming energy and by regulating their internal environment to maintain a stable, the term biology is derived from the Greek word βίος, bios, life and the suffix -λογία, -logia, study of. The Latin-language form of the term first appeared in 1736 when Swedish scientist Carl Linnaeus used biologi in his Bibliotheca botanica, the first German use, Biologie, was in a 1771 translation of Linnaeus work. In 1797, Theodor Georg August Roose used the term in the preface of a book, 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. The science that concerns itself with these objects we will indicate by the biology or the doctrine of life. Although modern biology is a recent development, sciences related to. Natural philosophy was studied as early as the ancient civilizations of Mesopotamia, Egypt, the Indian subcontinent, however, the origins of modern biology and its approach to the study of nature are most often traced back to ancient Greece. While the formal study of medicine back to Hippocrates, it was Aristotle 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. Aristotles 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. Scholars of the medieval Islamic world who wrote on biology included al-Jahiz, Al-Dīnawarī, who wrote on botany, biology began to quickly develop and grow with Anton van Leeuwenhoeks dramatic improvement of the microscope. It was then that scholars discovered spermatozoa, bacteria, infusoria, investigations by Jan Swammerdam led to new interest in entomology and helped to develop the basic techniques of microscopic dissection and staining. Advances in microscopy also had a impact on biological thinking. In the early 19th century, a number of biologists pointed to the importance of the cell. Thanks to the work of Robert Remak and Rudolf Virchow, however, meanwhile, taxonomy and classification became the focus of natural historians
3.
Pattern
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A pattern, apart from the terms use to mean Template, is a discernible regularity in the world or in a manmade design. As such, the elements of a repeat in a predictable manner. A geometric pattern is a kind of pattern formed of geometric shapes, any of the senses may directly observe patterns. Conversely, abstract patterns in science, mathematics, or language may be only by analysis. Direct observation in practice means seeing visual patterns, which are widespread in nature, visual patterns in nature are often chaotic, never exactly repeating, and often involve fractals. Natural patterns include spirals, meanders, waves, foams, tilings, cracks, Patterns have an underlying mathematical structure, indeed, mathematics can be seen as the search for regularities, and the output of any function is a mathematical pattern. Similarly in the sciences, theories explain and predict regularities in the world, in art and architecture, decorations or visual motifs may be combined and repeated to form patterns designed to have a chosen effect on the viewer. In computer science, a design pattern is a known solution to a class of problems in programming. In fashion, the pattern is a used to create any number of similar garments. Nature provides examples of many kinds of pattern, including symmetries, trees and other structures with a dimension, spirals, meanders, waves, foams, tilings, cracks. Symmetry is widespread in living things, animals that move usually have bilateral or mirror symmetry as this favours movement. Plants often have radial or rotational symmetry, as do many flowers, as well as animals which are largely static as adults, fivefold symmetry is found in the echinoderms, including starfish, sea urchins, and sea lilies. Among non-living things, snowflakes have striking sixfold symmetry, each flake is unique, crystals have a highly specific set of possible crystal symmetries, they can be cubic or octahedral, but cannot have fivefold symmetry. Many natural patterns are shaped by this apparent randomness, including vortex streets, waves are disturbances that carry energy as they move. Mechanical waves propagate through a medium – air or water, making it oscillate as they pass by, wind waves are surface waves that create the chaotic patterns of the sea. As they pass over sand, such waves create patterns of ripples, similarly, as the passes over sand. Foams obey Plateaus laws, which films to be smooth and continuous. Foam and bubble patterns occur widely in nature, for example in radiolarians, sponge spicules, cracks form in materials to relieve stress, with 120 degree joints in elastic materials, but at 90 degrees in inelastic materials
4.
Anatomy
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Anatomy is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is inherently tied to embryology, comparative anatomy, evolutionary biology, Human anatomy is one of the basic essential sciences of medicine. The discipline of anatomy is divided into macroscopic and microscopic anatomy, macroscopic anatomy, or gross anatomy, is the examination of an animals body parts using unaided eyesight. Gross anatomy also includes the branch of superficial anatomy, microscopic anatomy involves the use of optical instruments in the study of the tissues of various structures, known as histology, and also in the study of cells. The history of anatomy is characterized by an understanding of the functions of the organs. Anatomy and physiology, which study the structure and function of organisms and their parts, make a pair of related disciplines. Derived from the Greek ἀνατομή anatomē dissection, anatomy is the study of the structure of organisms including their systems, organs. It includes the appearance and position of the parts, the materials from which they are composed, their locations. Anatomy is quite distinct from physiology and biochemistry, which deal respectively with the functions of those parts, the discipline of anatomy can be subdivided into a number of branches including gross or macroscopic anatomy and microscopic anatomy. Gross anatomy is the study of large enough to be seen with the naked eye, and also includes superficial anatomy or surface anatomy. Microscopic anatomy is the study of structures on a scale, including histology. Anatomy can be studied using both invasive and non-invasive methods with the goal of obtaining information about the structure and organization of organs, angiography using X-rays or magnetic resonance angiography are methods to visualize blood vessels. The term anatomy is commonly taken to refer to human anatomy, however, substantially the same structures and tissues are found throughout the rest of the animal kingdom and the term also includes the anatomy of other animals. The term zootomy is also used to specifically refer to animals. The structure and tissues of plants are of a dissimilar nature, the kingdom Animalia or metazoa, contains multicellular organisms that are heterotrophic and motile. Most animals have bodies differentiated into separate tissues and these animals are known as eumetazoans. They have a digestive chamber, with one or two openings, the gametes are produced in multicellular sex organs, and the zygotes include a blastula stage in their embryonic development. Metazoans do not include the sponges, which have undifferentiated cells, unlike plant cells, animal cells have neither a cell wall nor chloroplasts
5.
Johann Wolfgang von Goethe
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Johann Wolfgang von Goethe was a German writer and statesman. In addition, numerous literary and scientific fragments, more than 10,000 letters and he was an early participant in the Sturm und Drang literary movement. He also contributed to the planning of Weimars botanical park and the rebuilding of its Ducal Palace and his first major scientific work, the Metamorphosis of Plants, was published after he returned from a 1788 tour of Italy. During this period, Goethe published his novel, Wilhelm Meisters Apprenticeship, the verse epic Hermann and Dorothea, and, in 1808. Goethes comments and observations form the basis of several biographical works, Goethes father, Johann Caspar Goethe, lived with his family in a large house in Frankfurt, then an Imperial Free City of the Holy Roman Empire. Though he had studied law in Leipzig and had been appointed Imperial Councillor, Johann Caspar married Goethes mother, Catharina Elizabeth Textor at Frankfurt on 20 August 1748, when he was 38 and she was 17. All their children, with the exception of Johann Wolfgang and his sister, Cornelia Friederica Christiana and his father and private tutors gave Goethe lessons in all the common subjects of their time, especially languages. Goethe also received lessons in dancing, riding and fencing, Johann Caspar, feeling frustrated in his own ambitions, was determined that his children should have all those advantages that he had not. Although Goethes great passion was drawing, he became interested in literature, Friedrich Gottlieb Klopstock. He also took pleasure in reading works on history and religion. He writes about this period, Goethe became also acquainted with Frankfurt actors, among early literary attempts, he was infatuated with Gretchen, who would later reappear in his Faust and the adventures with whom he would concisely describe in Dichtung und Wahrheit. He adored Caritas Meixner, a wealthy Worms traders daughter and friend of his sister, Goethe studied law at Leipzig University from 1765 to 1768. He detested learning age-old judicial rules by heart, preferring instead to attend the lessons of Christian Fürchtegott Gellert. In Leipzig, Goethe fell in love with Anna Katharina Schönkopf, in 1770, he anonymously released Annette, his first collection of poems. His uncritical admiration for many contemporary poets vanished as he became interested in Gotthold Ephraim Lessing, already at this time, Goethe wrote a good deal, but he threw away nearly all of these works, except for the comedy Die Mitschuldigen. The restaurant Auerbachs Keller and its legend of Fausts 1525 barrel ride impressed him so much that Auerbachs Keller became the real place in his closet drama Faust Part One. As his studies did not progress, Goethe was forced to return to Frankfurt at the close of August 1768, Goethe became severely ill in Frankfurt. During the year and a half that followed, because of several relapses, during convalescence, Goethe was nursed by his mother and sister
6.
Georges Cuvier
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Jean Léopold Nicolas Frédéric Cuvier, known as Georges Cuvier, was a French naturalist and zoologist, sometimes referred to as the father of paleontology. Cuvier is also known for establishing extinction as a fact—at the time, in his Essay on the Theory of the Earth Cuvier was interpreted to have proposed that new species were created after periodic catastrophic floods. In this way, Cuvier became the most influential proponent of catastrophism in geology in the early 19th century and his study of the strata of the Paris basin with Alexandre Brongniart established the basic principles of biostratigraphy. Cuvier is also remembered for strongly opposing theories of evolution, which at the time were mainly proposed by Jean-Baptiste de Lamarck, Cuvier believed there was no evidence for evolution, but rather evidence for cyclical creations and destructions of life forms by global extinction events such as deluges. Cuvier supported function and rejected Lamarcks thinking and his most famous work is Le Règne Animal. In 1819, he was created a peer for life in honor of his scientific contributions, thereafter, he was known as Baron Cuvier. He died in Paris during an epidemic of cholera, some of Cuviers most influential followers were Louis Agassiz on the continent and in the United States, and Richard Owen in Britain. His name is one of the 72 names inscribed on the Eiffel Tower, Cuvier was born in Montbéliard, France, where his Protestant ancestors had lived since the time of the Reformation. His father, Jean George Cuvier, was a lieutenant in the Swiss Guards, at the time, the town, which was annexed to France on 10 October 1793, belonged to the Duchy of Württemberg. His mother, who was younger than his father, tutored him diligently throughout his early years. During his gymnasium years, he had trouble acquiring Latin and Greek, and was always at the head of his class in mathematics, history. At the age of 10, soon entering the gymnasium, he encountered a copy of Conrad Gessners Historiae Animalium. He then began frequent visits to the home of a relation, all of these he read and reread, retaining so much of the information, that by the age of 12, he was as familiar with quadrupeds and birds as a first-rate naturalist. He remained at the gymnasium for four years, Cuvier spent an additional four years at the Caroline Academy in Stuttgart, where he excelled in all of his coursework. Although he knew no German on his arrival, after nine months of study. Upon graduation, he had no money on which to live as he awaited appointment to an academic office, so in July 1788, he took a job at Fiquainville chateau in Normandy as tutor to the only son of the Comte dHéricy, a Protestant noble. There, during the early 1790s, he began his comparisons of fossils with extant forms, Cuvier regularly attended meetings held at the nearby town of Valmont for the discussion of agricultural topics. There, he acquainted with Henri Alexandre Tessier, who had assumed a false identity
7.
Richard Owen
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Sir Richard Owen KCB FRMS FRS was an English biologist, comparative anatomist and paleontologist. Despite being a figure, Owen is generally considered to have been an outstanding naturalist with a remarkable gift for interpreting fossils. Owen produced a vast array of work, but is probably best remembered today for coining the word Dinosauria. Owens approach to evolution can be seen as having anticipated the issues that have gained attention with the recent emergence of evolutionary developmental biology. Owen also campaigned for the specimens in the British Museum to be given a new home. This resulted in the establishment, in 1881, of the now world-famous Natural History Museum in South Kensington, London, bill Bryson argues that, by making the Natural History Museum an institution for everyone, Owen transformed our expectations of what museums are for. Owen was feared and even hated by some such as Thomas Henry Huxley. His later career was tainted by a number of controversies, many of which involved accusations that he took credit for other peoples work, Owen was born in Lancaster in 1804, one of six children of a West Indian Merchant named Richard Owen. His mother, Catherine Parrin, was descended from Huguenots and he was educated at Lancaster Royal Grammar School, in 1820, he was apprenticed to a local surgeon and apothecary and, in 1824, he proceeded as a medical student to the University of Edinburgh. He left the university in the year and completed his medical course in St Bartholomews Hospital, London. In July 1835 Owen married Caroline Amelia Clift in St Pancras by whom he had one son, Richard sadly outlived both his wife and only son. After his death, in 1892, he was survived by his three grandchildren and daughter-in-law Emily Owen, to whom he left much of his £33,000 fortune. Upon completing his education, he contemplated the usual professional career and he was induced by Abernethy to accept the position of assistant to William Clift, conservator of the museum of the Royal College of Surgeons. This congenial occupation soon led him to abandon his intention of medical practice, in 1836, Owen was appointed Hunterian professor, in the Royal College of Surgeons and, in 1849, he succeeded Clift as conservator. He held the office until 1856, when he became superintendent of the natural history department of the British Museum. He retained office until the completion of work, in December,1883. He lived quietly in retirement at Sheen Lodge, Richmond Park and his career was tainted by accusations that he failed to give credit to the work of others and even tried to appropriate it in his own name. This came to a head in 1846, when he was awarded the Royal Medal for a paper he had written on belemnites, Owen had failed to acknowledge that the belemnite had been discovered by Chaning Pearce, an amateur biologist, four years earlier
8.
Ernst Haeckel
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The published artwork of Haeckel includes over 100 detailed, multi-colour illustrations of animals and sea creatures. As a philosopher, Ernst Haeckel wrote Die Welträtsel, the genesis for the term world riddle, Ernst Haeckel was born on 16 February 1834, in Potsdam. In 1852, Haeckel completed studies at the Domgymnasium, the high school of Merseburg. He then studied medicine in Berlin and Würzburg, particularly with Albert von Kölliker, Franz Leydig, Rudolf Virchow, together with Hermann Steudner he attended botany lectures in Würzburg. In 1857, Haeckel attained a doctorate in medicine, and afterwards he received a license to practice medicine, the occupation of physician appeared less worthwhile to Haeckel, after contact with suffering patients. Between 1859 and 1866, Haeckel worked on many phyla such radiolarians, poriferans, during a trip to the Mediterranean, Haeckel named nearly 150 new species of radiolarians. In 1867, he married Agnes Huschke and their son Walter was born in 1868, their daughters Elizabeth in 1871 and Emma in 1873. In 1869, he traveled as a researcher to Norway, in 1871 to Croatia, and in 1873 to Egypt, Turkey, Haeckel retired from teaching in 1909, and in 1910 he withdrew from the Evangelical church. Haeckels wife, Agnes, died in 1915, and Haeckel became substantially frailer, with a broken leg and he sold his Villa Medusa in Jena in 1918 to the Carl Zeiss foundation, and it presently contains a historic library. Haeckel died on 9 August 1919, Haeckels political beliefs were influenced by his affinity for the German Romantic movement coupled with his acceptance of a form of Lamarckism. Rather than being a strict Darwinian, Haeckel believed that the characteristics of an organism were acquired through interactions with the environment and he believed the social sciences to be instances of applied biology, and that phrase was picked up and used for Nazi propaganda. In 1905, Haeckel founded a group called the Monist League to promote his religious and this group lasted until 1933 and included such notable members as Wilhelm Ostwald, Georg von Arco, Helene Stöcker and Walter Arthur Berendsohn. Haeckel was the first person known to use the term First World War. Shortly after the start of the war Haeckel wrote, There is no doubt that the course, Haeckel was a zoologist, an accomplished artist and illustrator, and later a professor of comparative anatomy. For example, Haeckel described and named hypothetical ancestral microorganisms that have never been found and he was one of the first to consider psychology as a branch of physiology. He also proposed the kingdom Protista in 1866 and his chief interests lay in evolution and life development processes in general, including development of nonrandom form, which culminated in the beautifully illustrated Kunstformen der Natur. Haeckel did not support natural selection, rather believing in Lamarckism and it proposed a link between ontogeny and phylogeny, summed up by Haeckel in the phrase ontogeny recapitulates phylogeny. His concept of recapitulation has been refuted in the form he gave it, the strong recapitulation hypothesis views ontogeny as repeating forms of the ancestors, while weak recapitulation means that what is repeated is the ancestral embryonic development process
9.
Polymer
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A polymer is a large molecule, or macromolecule, composed of many repeated subunits. Because of their range of properties, both synthetic and natural polymers play an essential and ubiquitous role in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure, Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. The units composing polymers derive, actually or conceptually, from molecules of low molecular mass. The term was coined in 1833 by Jöns Jacob Berzelius, though with a distinct from the modern IUPAC definition. The modern concept of polymers as covalently bonded macromolecular structures was proposed in 1920 by Hermann Staudinger, Polymers are studied in the fields of biophysics and macromolecular science, and polymer science. Polyisoprene of latex rubber is an example of a polymer. In biological contexts, essentially all biological macromolecules—i. e, proteins, nucleic acids, and polysaccharides—are purely polymeric, or are composed in large part of polymeric components—e. g. Isoprenylated/lipid-modified glycoproteins, where small molecules and oligosaccharide modifications occur on the polyamide backbone of the protein. The simplest theoretical models for polymers are ideal chains, Polymers are of two types, Natural polymeric materials such as shellac, amber, wool, silk and natural rubber have been used for centuries. A variety of natural polymers exist, such as cellulose. Most commonly, the continuously linked backbone of a used for the preparation of plastics consists mainly of carbon atoms. A simple example is polyethylene, whose repeating unit is based on ethylene monomer, however, other structures do exist, for example, elements such as silicon form familiar materials such as silicones, examples being Silly Putty and waterproof plumbing sealant. Oxygen is also present in polymer backbones, such as those of polyethylene glycol, polysaccharides. Polymerization is the process of combining many small molecules known as monomers into a covalently bonded chain or network, during the polymerization process, some chemical groups may be lost from each monomer. This is the case, for example, in the polymerization of PET polyester, the distinct piece of each monomer that is incorporated into the polymer is known as a repeat unit or monomer residue. Laboratory synthetic methods are divided into two categories, step-growth polymerization and chain-growth polymerization. However, some methods such as plasma polymerization do not fit neatly into either category
10.
Species
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In biology, a species is the basic unit of biological classification and a taxonomic rank. A species is defined as the largest group of organisms in which two individuals can produce fertile offspring, typically by sexual reproduction. While this definition is often adequate, looked at more closely it is problematic, for example, with hybridisation, in a species complex of hundreds of similar microspecies, or in a ring species, the boundaries between closely related species become unclear. Other ways of defining species include similarity of DNA, morphology, all species are given a two-part name, a binomial. The first part of a binomial is the genus to which the species belongs, the second part is called the specific name or the specific epithet. For example, Boa constrictor is one of four species of the Boa genus, Species were seen from the time of Aristotle until the 18th century as fixed kinds that could be arranged in a hierarchy, the great chain of being. In the 19th century, biologists grasped that species could evolve given sufficient time, Charles Darwins 1859 book The Origin of Species explained how species could arise by natural selection. Genes can sometimes be exchanged between species by horizontal transfer, and species may become extinct for a variety of reasons. In his biology, Aristotle used the term γένος to mean a kind, such as a bird or fish, a kind was distinguished by its attributes, for instance, a bird has feathers, a beak, wings, a hard-shelled egg, and warm blood. A form was distinguished by being shared by all its members, Aristotle believed all kinds and forms to be distinct and unchanging. His approach remained influential until the Renaissance, when observers in the Early Modern period began to develop systems of organization for living things, they placed each kind of animal or plant into a context. Many of these early delineation schemes would now be considered whimsical, animals likewise that differ specifically preserve their distinct species permanently, one species never springs from the seed of another nor vice versa. In the 18th century, the Swedish scientist Carl Linnaeus classified organisms according to shared physical characteristics and he established the idea of a taxonomic hierarchy of classification based upon observable characteristics and intended to reflect natural relationships. At the time, however, it was widely believed that there was no organic connection between species, no matter how similar they appeared. However, whether or not it was supposed to be fixed, by the 19th century, naturalists understood that species could change form over time, and that the history of the planet provided enough time for major changes. Jean-Baptiste Lamarck, in his 1809 Zoological Philosophy, described the transmutation of species, proposing that a species could change over time, in 1859, Charles Darwin and Alfred Russel Wallace provided a compelling account of evolution and the formation of new species. Darwin argued that it was populations that evolved, not individuals and this required a new definition of species. Darwin concluded that species are what appear to be, ideas
11.
Convergent evolution
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Convergent evolution is the independent evolution of similar features in species of different lineages. Convergent evolution creates analogous structures that have similar form or function but were not present in the last common ancestor of those groups, the cladistic term for the same phenomenon is homoplasy. The recurrent evolution of flight is an example, as flying insects, birds. Functionally similar features that have arisen through convergent evolution are analogous, whereas homologous structures or traits have a common origin, bird, bat and pterosaur wings are analogous structures, but their forelimbs are homologous, sharing an ancestral state despite serving different functions. The opposite of convergence is divergent evolution, where related species evolve different traits, convergent evolution is similar to but different from parallel evolution. Many instances of convergent evolution are known in plants, including the development of C4 photosynthesis, seed dispersal by fleshy fruits adapted to be eaten by animals. In morphology, analogous traits arise when different species live in similar ways and/or a similar environment, when occupying similar ecological niches similar problems can lead to similar solutions. The British anatomist Richard Owen was the first to identify the difference between analogies and homologies. In biochemistry, physical and chemical constraints on mechanisms have caused some active site arrangements such as the triad to evolve independently in separate enzyme superfamilies. In his 1989 book Wonderful Life, Stephen Jay Gould argued that if one could rewind the tape of life the same conditions were encountered again, evolution could take a very different course. In cladistics, a homoplasy is a trait shared by two or more taxa for any other than that they share a common ancestry. Taxa which do share ancestry are part of the same clade, homoplastic traits caused by convergence are therefore, from the point of view of cladistics, confounding factors which could lead to an incorrect analysis. In some cases, it is difficult to tell whether a trait has been lost and then re-evolved convergently, or whether a gene has simply been switched off, such a re-emerged trait is called an atavism. From a mathematical standpoint, a gene has a steadily decreasing probability of retaining potential functionality over time. When two species are similar in a character, evolution is defined as parallel if the ancestors were also similar. When the ancestral forms are unspecified or unknown, or the range of traits considered is not clearly specified, the enzymology of proteases provides some of the clearest examples of convergent evolution. These examples reflect the intrinsic chemical constraints on enzymes, leading evolution to converge on equivalent solutions independently and repeatedly, serine and cysteine proteases use different amino acid functional groups as a nucleophile. In order to activate that nucleophile, they orient an acidic, the chemical and physical constraints on enzyme catalysis have caused identical triad arrangements to evolve independently more than 20 times in different enzyme superfamilies
