Cladistics is an approach to biological classification in which organisms are categorized in groups based on the most recent common ancestor. Hypothesized relationships are based on shared derived characteristics that can be traced to the most recent common ancestor and are not present in more distant groups and ancestors. A key feature of a clade is that all its descendants are part of the clade. All descendants stay in their overarching ancestral clade. For example, if within a strict cladistic framework the terms animals, bilateria/worms, fishes/vertebrata, or monkeys/anthropoidea were used, these terms would include humans. Many of these terms are used paraphyletically, outside of cladistics, e.g. as a'grade'. Radiation results in the generation of new subclades by bifurcation; the techniques and nomenclature of cladistics have been applied to other disciplines. Cladistics is now the most used method to classify organisms; the original methods used in cladistic analysis and the school of taxonomy derived from the work of the German entomologist Willi Hennig, who referred to it as phylogenetic systematics.
Cladistics in the original sense refers to a particular set of methods used in phylogenetic analysis, although it is now sometimes used to refer to the whole field. What is now called the cladistic method appeared as early as 1901 with a work by Peter Chalmers Mitchell for birds and subsequently by Robert John Tillyard in 1921, W. Zimmermann in 1943; the term "clade" was introduced in 1958 by Julian Huxley after having been coined by Lucien Cuénot in 1940, "cladogenesis" in 1958, "cladistic" by Cain and Harrison in 1960, "cladist" by Mayr in 1965, "cladistics" in 1966. Hennig referred to his own approach as "phylogenetic systematics". From the time of his original formulation until the end of the 1970s, cladistics competed as an analytical and philosophical approach to systematics with phenetics and so-called evolutionary taxonomy. Phenetics was championed at this time by the numerical taxonomists Peter Sneath and Robert Sokal, evolutionary taxonomy by Ernst Mayr. Conceived, if only in essence, by Willi Hennig in a book published in 1950, cladistics did not flourish until its translation into English in 1966.
Today, cladistics is the most popular method for constructing phylogenies from morphological data. In the 1990s, the development of effective polymerase chain reaction techniques allowed the application of cladistic methods to biochemical and molecular genetic traits of organisms, vastly expanding the amount of data available for phylogenetics. At the same time, cladistics became popular in evolutionary biology, because computers made it possible to process large quantities of data about organisms and their characteristics; the cladistic method interprets each character state transformation implied by the distribution of shared character states among taxa as a potential piece of evidence for grouping. The outcome of a cladistic analysis is a cladogram – a tree-shaped diagram, interpreted to represent the best hypothesis of phylogenetic relationships. Although traditionally such cladograms were generated on the basis of morphological characters and calculated by hand, genetic sequencing data and computational phylogenetics are now used in phylogenetic analyses, the parsimony criterion has been abandoned by many phylogeneticists in favor of more "sophisticated" but less parsimonious evolutionary models of character state transformation.
Cladists contend. Every cladogram is based on a particular dataset analyzed with a particular method. Datasets are tables consisting of molecular, ethological and/or other characters and a list of operational taxonomic units, which may be genes, populations, species, or larger taxa that are presumed to be monophyletic and therefore to form, all together, one large clade. Different datasets and different methods, not to mention violations of the mentioned assumptions result in different cladograms. Only scientific investigation can show, more to be correct; until for example, cladograms like the following have been accepted as accurate representations of the ancestral relations among turtles, lizards and birds: If this phylogenetic hypothesis is correct the last common ancestor of turtles and birds, at the branch near the ▼ lived earlier than the last common ancestor of lizards and birds, near the ♦. Most molecular evidence, produces cladograms more like this: If this is accurate the last common ancestor of turtles and birds lived than the last common ancestor of lizards and birds.
Since the cladograms provide competing accounts of real events, at most one of them is correct. The cladogram to the right represents the current universally accepted hypothesis that all primates, including strepsirrhines like the lemurs and lorises, had a common ancestor all of whose descendants were primates, so form a clade. Within the primates, all anthropoids are hypothesized to have had a common ancestor all of whose descendants were anthropoids, so they form the clade called Anthropoidea; the "prosimians", on the other hand, form a paraphyletic taxon. The name Prosimii is not used in phylogenetic nomenclature, whic
Biology is the natural science that studies life and living organisms, including their physical structure, chemical processes, molecular interactions, physiological mechanisms and evolution. Despite the complexity of the science, there are certain unifying concepts that consolidate it into a single, coherent field. Biology recognizes the cell as the basic unit of life, genes as the basic unit of heredity, evolution as the engine that propels the creation and extinction of species. Living organisms are open systems that survive by transforming energy and decreasing their local entropy to maintain a stable and vital condition defined as homeostasis. Sub-disciplines of biology are defined by the research methods employed and the kind of system studied: theoretical biology uses mathematical methods to formulate quantitative models while experimental biology performs empirical experiments to test the validity of proposed theories and understand the mechanisms underlying life and how it appeared and evolved from non-living matter about 4 billion years ago through a gradual increase in the complexity of the system.
See branches of biology. 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. It was used again in 1766 in a work entitled Philosophiae naturalis sive physicae: tomus III, continens geologian, phytologian generalis, by Michael Christoph Hanov, a disciple of Christian Wolff; the first German use, was in a 1771 translation of Linnaeus' work. In 1797, Theodor Georg August Roose used the term in the preface of a book, Grundzüge der Lehre van der Lebenskraft. Karl Friedrich Burdach used the term in 1800 in a more restricted sense of the study of human beings from a morphological and psychological perspective; the term came into its modern usage with the six-volume treatise Biologie, oder Philosophie der lebenden Natur by Gottfried Reinhold Treviranus, who announced: The objects of our research will be the different forms and manifestations of life, the conditions and laws under which these phenomena occur, the causes through which they have been effected.
The science that concerns itself with these objects we will indicate by the name biology or the doctrine of life. Although modern biology is a recent development, sciences related to and included within it have been studied since ancient times. Natural philosophy was studied as early as the ancient civilizations of Mesopotamia, the Indian subcontinent, China. However, the origins of modern biology and its approach to the study of nature are most traced back to ancient Greece. While the formal study of medicine dates back to Hippocrates, it was Aristotle who contributed most extensively to the development of biology. Important are his History of Animals and other works where he showed naturalist leanings, more empirical works that focused on biological causation and the diversity of life. Aristotle's successor at the Lyceum, wrote a series of books on botany that survived as the most important contribution of antiquity to the plant sciences into the Middle Ages. Scholars of the medieval Islamic world who wrote on biology included al-Jahiz, Al-Dīnawarī, who wrote on botany, Rhazes who wrote on anatomy and physiology.
Medicine was well studied by Islamic scholars working in Greek philosopher traditions, while natural history drew on Aristotelian thought in upholding a fixed hierarchy of life. Biology began to develop and grow with Anton van Leeuwenhoek's dramatic improvement of the microscope, it was that scholars discovered spermatozoa, bacteria and the diversity of microscopic life. 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 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 1838, Schleiden and Schwann began promoting the now universal ideas that the basic unit of organisms is the cell and that individual cells have all the characteristics of life, although they opposed the idea that all cells come from the division of other cells. Thanks to the work of Robert Remak and Rudolf Virchow, however, by the 1860s most biologists accepted all three tenets of what came to be known as cell theory.
Meanwhile and classification became the focus of natural historians. Carl Linnaeus published a basic taxonomy for the natural world in 1735, in the 1750s introduced scientific names for all his species. Georges-Louis Leclerc, Comte de Buffon, treated species as artificial categories and living forms as malleable—even suggesting the possibility of common descent. Although he was opposed to evolution, Buffon is a key figure in the history of evolutionary thought. Serious evolutionary thinking originated with the works of Jean-Baptiste Lamarck, the first to present a coherent theory of evolution, he posited that evolution was the result of environmental stress on properties of animals, meaning that the more and rigorously an organ was used, the more complex and efficient it would become, thus adapting the animal to its environment. Lamarck believed that these acquired traits could be passed on to the animal's offspring, who would
A Venn diagram is a diagram that shows all possible logical relations between a finite collection of different sets. These diagrams depict elements as points in the plane, sets as regions inside closed curves. A Venn diagram consists of multiple overlapping closed curves circles, each representing a set; the points inside a curve labelled S represent elements of the set S, while points outside the boundary represent elements not in the set S. This lends to read visualizations. In Venn diagrams the curves are overlapped in every possible way, showing all possible relations between the sets, they are thus a special case of Euler diagrams, which do not show all relations. Venn diagrams were conceived around 1880 by John Venn, they are used to teach elementary set theory, as well as illustrate simple set relationships in probability, statistics and computer science. A Venn diagram in which the area of each shape is proportional to the number of elements it contains is called an area-proportional or scaled Venn diagram.
This example involves A and B, represented here as coloured circles. The orange circle, set A, represents all living creatures; the blue circle, set B, represents the living creatures. Each separate type of creature can be imagined as a point somewhere in the diagram. Living creatures that both can fly and have two legs—for example, parrots—are in both sets, so they correspond to points in the region where the blue and orange circles overlap, it is important to note that this overlapping region would only contain those elements that are members of both set A and are members of set B Humans and penguins are bipedal, so are in the orange circle, but since they cannot fly they appear in the left part of the orange circle, where it does not overlap with the blue circle. Mosquitoes have six legs, fly, so the point for mosquitoes is in the part of the blue circle that does not overlap with the orange one. Creatures that are not two-legged and cannot fly would all be represented by points outside both circles.
The combined region of sets A and B is called the union of A and B, denoted by A ∪ B. The union in this case contains all living creatures that can fly; the region in both A and B, where the two sets overlap, is called the intersection of A and B, denoted by A ∩ B. For example, the intersection of the two sets is not empty, because there are points that represent creatures that are in both the orange and blue circles. Venn diagrams were introduced in 1880 by John Venn in a paper entitled On the Diagrammatic and Mechanical Representation of Propositions and Reasonings in the "Philosophical Magazine and Journal of Science", about the different ways to represent propositions by diagrams; the use of these types of diagrams in formal logic, according to Frank Ruskey and Mark Weston, is "not an easy history to trace, but it is certain that the diagrams that are popularly associated with Venn, in fact, originated much earlier. They are rightly associated with Venn, because he comprehensively surveyed and formalized their usage, was the first to generalize them".
Venn himself did not use the term "Venn diagram" and referred to his invention as "Eulerian Circles". For example, in the opening sentence of his 1880 article Venn writes, "Schemes of diagrammatic representation have been so familiarly introduced into logical treatises during the last century or so, that many readers those who have made no professional study of logic, may be supposed to be acquainted with the general nature and object of such devices. Of these schemes one only, viz. that called'Eulerian circles,' has met with any general acceptance..." Lewis Carroll includes "Venn's Method of Diagrams" as well as "Euler's Method of Diagrams" in an "Appendix, Addressed to Teachers" of his book "Symbolic Logic". The term "Venn diagram" was used by Clarence Irving Lewis in 1918, in his book "A Survey of Symbolic Logic". Venn diagrams are similar to Euler diagrams, which were invented by Leonhard Euler in the 18th century. M. E. Baron has noted that Leibniz in the 17th century produced similar diagrams before Euler, but much of it was unpublished.
She observes earlier Euler-like diagrams by Ramon Llull in the 13th Century. In the 20th century, Venn diagrams were further developed. D. W. Henderson showed in 1963 that the existence of an n-Venn diagram with n-fold rotational symmetry implied that n was a prime number, he showed that such symmetric Venn diagrams exist when n is five or seven. In 2002 Peter Hamburger found symmetric Venn diagrams for n = 11 and in 2003, Griggs and Savage showed that symmetric Venn diagrams exist for all other primes, thus rotationally symmetric Venn diagrams exist. Venn diagrams and Euler diagrams were incorporated as part of instruction in set theory as part of the new math movement in the 1960s. Since they have been adopted in the curriculum of other fields such as reading. A Venn diagram is constructed with a collection of simple closed curves drawn in a plane. According to Lewis, the "principle of these diagrams is that classes be represented by regions in such relation to one another that all the possible logical relations of these classes can be indicated in the same diagram.
That is, the diagram leaves room for any possible relation
In biology, an organism is any individual entity that exhibits the properties of life. It is a synonym for "life form". Organisms are classified by taxonomy into specified groups such as the multicellular animals and fungi. All types of organisms are capable of reproduction and development, some degree of response to stimuli. Humans are multicellular animals composed of many trillions of cells which differentiate during development into specialized tissues and organs. An organism may be either a eukaryote. Prokaryotes are represented by two separate domains -- archaea. Eukaryotic organisms are characterized by the presence of a membrane-bound cell nucleus and contain additional membrane-bound compartments called organelles. Fungi and plants are examples of kingdoms of organisms within the eukaryotes. Estimates on the number of Earth's current species range from 10 million to 14 million, of which only about 1.2 million have been documented. More than 99% of all species, amounting to over five billion species, that lived are estimated to be extinct.
In 2016, a set of 355 genes from the last universal common ancestor of all organisms was identified. The term "organism" first appeared in the English language in 1703 and took on its current definition by 1834, it is directly related to the term "organization". There is a long tradition of defining organisms as self-organizing beings, going back at least to Immanuel Kant's 1790 Critique of Judgment. An organism may be defined as an assembly of molecules functioning as a more or less stable whole that exhibits the properties of life. Dictionary definitions can be broad, using phrases such as "any living structure, such as a plant, fungus or bacterium, capable of growth and reproduction". Many definitions exclude viruses and possible man-made non-organic life forms, as viruses are dependent on the biochemical machinery of a host cell for reproduction. A superorganism is an organism consisting of many individuals working together as a single functional or social unit. There has been controversy about the best way to define the organism and indeed about whether or not such a definition is necessary.
Several contributions are responses to the suggestion that the category of "organism" may well not be adequate in biology. Viruses are not considered to be organisms because they are incapable of autonomous reproduction, growth or metabolism; this controversy is problematic because some cellular organisms are incapable of independent survival and live as obligatory intracellular parasites. Although viruses have a few enzymes and molecules characteristic of living organisms, they have no metabolism of their own; this rules out autonomous reproduction: they can only be passively replicated by the machinery of the host cell. In this sense, they are similar to inanimate matter. While viruses sustain no independent metabolism and thus are not classified as organisms, they do have their own genes, they do evolve by mechanisms similar to the evolutionary mechanisms of organisms; the most common argument in support of viruses as living organisms is their ability to undergo evolution and replicate through self-assembly.
Some scientists argue. In fact, viruses are evolved by their host cells, meaning that there was co-evolution of viruses and host cells. If host cells did not exist, viral evolution would be impossible; this is not true for cells. If viruses did not exist, the direction of cellular evolution could be different, but cells would be able to evolve; as for the reproduction, viruses rely on hosts' machinery to replicate. The discovery of viral metagenomes with genes coding for energy metabolism and protein synthesis fueled the debate about whether viruses belong in the tree of life; the presence of these genes suggested. However, it was found that the genes coding for energy and protein metabolism have a cellular origin. Most these genes were acquired through horizontal gene transfer from viral hosts. Organisms are complex chemical systems, organized in ways that promote reproduction and some measure of sustainability or survival; the same laws that govern non-living chemistry govern the chemical processes of life.
It is the phenomena of entire organisms that determine their fitness to an environment and therefore the survivability of their DNA-based genes. Organisms owe their origin and many other internal functions to chemical phenomena the chemistry of large organic molecules. Organisms are complex systems of chemical compounds that, through interaction and environment, play a wide variety of roles. Organisms are semi-closed chemical systems. Although they are individual units of life, they are not closed to the environment around them. To operate they take in and release energy. Autotrophs produce usable energy using light from the sun or inorganic compounds while heterotrophs take in organic compounds from the environment; the primary chemical element in these compounds is carbon. The chemical properties of this element such as its grea
The Anacardiaceae known as the cashew family or sumac family, are a family of flowering plants, including about 83 genera with about 860 known species. Members of the Anacardiaceae bear fruits that are drupes and in some cases produce urushiol, an irritant; the Anacardiaceae include numerous genera, several of which are economically important, notably cashew, poison ivy, smoke tree, yellow mombin, Peruvian pepper and cuachalalate. The genus Pistacia is now included, but was placed in its own family, the Pistaciaceae. Trees or shrubs, each has inconspicuous flowers and resinous or milky sap that may be poisonous, as in black poisonwood and sometimes foul-smelling. Resin canals located in the inner fibrous bark of the fibrovascular system found in the plant's stems and leaves are characteristic of all members of this family. Tannin sacs are widespread among the family; the wood of the Anacardiaceae has the frequent occurrence of simple small holes in the vessels in some species side by side with scalariform holes (in Campnosperma and Heeria argentea.
The simple pits are located in contact with the parenchyma. Leaves are deciduous or evergreen alternate and imparipinnate with opposite leaflats, while others are trifoliolate or simple or unifoliolate. Leaf architecture is diverse. Primary venation is pinnate. Secondary venation is eucamptodromous, craspedodromous or cladodromous Cladodromous venation, if present is considered diagnostic for Anacardiaceae. Flowers grow at the end of a branch or stem or at an angle from where the leaf joins the stem and have bracts. With this family and male flowers occur on some plants, bisexual and female flowers are on others, or flowers have both stamens and pistils. A calyx with three to seven cleft sepals and the same number of petals no petals, overlap each other in the bud. Stamens are twice as many or equal to the number of petals, inserted at the base of the fleshy ring or cup-shaped disk, inserted below the pistil. Stamen stalks are separate, anthers are able to move. Flowers have the ovary free. In the stamenate flowers, ovaries are single-celled.
In the pistillate flowers, ovaries are sometimes quadri - or quinticelled. One to three styles and one ovule occur in each cavity. Fruits open at maturity and are most drupes. Seed coats are thin or are crust-like. Little or no endosperm is present. Cotyledons are fleshy. Seeds are solitary with no albumen around the embryo. In 1759, Bernard de Jussieu arranged the plants in the royal garden of the Trianon at Versailles, according to his own scheme; that classification included a description of an order called the Terebintaceæ which contained a suborder that included Cassuvium, Mangifera, Connarus and Rourea. In 1789, Antoine Laurent de Jussieu, nephew of Bernard de Jussieu, published that classification scheme. Robert Brown described a subset of the Terebintaceae called Cassuvlæ or Anacardeæ in 1818, using the herbarium, collected by Christen Smith during a fated expedition headed by James Hingston Tuckey to explore the River Congo; the name and genera were based on the order with the same name, described by Bernard de Jussieu in 1759.
The herbarium from that expedition contained only one genus from Rhus. Augustin Pyramus de Candolle in 1824, used Robert Browns name Cassuvlæ or Anacardeæ, wrote another description of the group and filled it with the genera Anacardium, Holigarna, Buchanania, Astronium and Picramnia. John Lindley described the "Essential character" of the Anacardiaceæ, the "Cashew Tribe" in 1831, adopting the order, described by Jussieu, but abandoning the name Terebintaceæ, he includes the genera which were found in de Candolle's Anacardieæ and Sumachineæ: Anacardium, Mangifera and Mauria. The genus Pistacia has sometimes been separated into its own family, the Pistaciaceae, based on the reduced flower structure, differences in pollen, the feathery style of the flowers. However, the nature of the ovary does suggest it belongs in the Anacardiaceae, a position, supported by morphological and molecular studies, recent classifications have included Pistacia in the Anacardiaceae; the genus Abrahamia was separated from Protorhus in 2004.
The family has been treated as a series of five tribes by Engler, into subfamilies by Takhtajan, as Anacardioideae and Spondiadoideae. Pell's molecular analysis reinstated the two subfamilies without further division into tribes. Min and Barfod, in the Flora of China reinstated the five tribes, the single tribe Spondiadeae as Spondiadoideae; the cashew family is more abundant in warm or tropical regions with only a few species living in the temperate zones. Native to tropical Americas and India. Pistacia and some species of Rhus can be found in southern Europe, Rhus species can be found in much of North America and Schinus inhabits South America exclusively. Members of this f
The flowering plants known as angiosperms, Angiospermae or Magnoliophyta, are the most diverse group of land plants, with 64 orders, 416 families 13,164 known genera and c. 369,000 known species. Like gymnosperms, angiosperms are seed-producing plants. However, they are distinguished from gymnosperms by characteristics including flowers, endosperm within the seeds, the production of fruits that contain the seeds. Etymologically, angiosperm means a plant; the term comes from the Greek words sperma. The ancestors of flowering plants diverged from gymnosperms in the Triassic Period, 245 to 202 million years ago, the first flowering plants are known from 160 mya, they diversified extensively during the Early Cretaceous, became widespread by 120 mya, replaced conifers as the dominant trees from 100 to 60 mya. Angiosperms differ from other seed plants in several ways, described in the table below; these distinguishing characteristics taken together have made the angiosperms the most diverse and numerous land plants and the most commercially important group to humans.
Angiosperm stems are made up of seven layers. The amount and complexity of tissue-formation in flowering plants exceeds that of gymnosperms; the vascular bundles of the stem are arranged such that the phloem form concentric rings. In the dicotyledons, the bundles in the young stem are arranged in an open ring, separating a central pith from an outer cortex. In each bundle, separating the xylem and phloem, is a layer of meristem or active formative tissue known as cambium. By the formation of a layer of cambium between the bundles, a complete ring is formed, a regular periodical increase in thickness results from the development of xylem on the inside and phloem on the outside; the soft phloem becomes crushed, but the hard wood persists and forms the bulk of the stem and branches of the woody perennial. Owing to differences in the character of the elements produced at the beginning and end of the season, the wood is marked out in transverse section into concentric rings, one for each season of growth, called annual rings.
Among the monocotyledons, the bundles are more numerous in the young stem and are scattered through the ground tissue. They once formed the stem increases in diameter only in exceptional cases; the characteristic feature of angiosperms is the flower. Flowers show remarkable variation in form and elaboration, provide the most trustworthy external characteristics for establishing relationships among angiosperm species; the function of the flower is to ensure fertilization of the ovule and development of fruit containing seeds. The floral apparatus may arise terminally from the axil of a leaf; as in violets, a flower arises singly in the axil of an ordinary foliage-leaf. More the flower-bearing portion of the plant is distinguished from the foliage-bearing or vegetative portion, forms a more or less elaborate branch-system called an inflorescence. There are two kinds of reproductive cells produced by flowers. Microspores, which will divide to become pollen grains, are the "male" cells and are borne in the stamens.
The "female" cells called megaspores, which will divide to become the egg cell, are contained in the ovule and enclosed in the carpel. The flower may consist only of these parts, as in willow, where each flower comprises only a few stamens or two carpels. Other structures are present and serve to protect the sporophylls and to form an envelope attractive to pollinators; the individual members of these surrounding structures are known as petals. The outer series is green and leaf-like, functions to protect the rest of the flower the bud; the inner series is, in general, white or brightly colored, is more delicate in structure. It functions to attract bird pollinators. Attraction is effected by color and nectar, which may be secreted in some part of the flower; the characteristics that attract pollinators account for the popularity of flowers and flowering plants among humans. While the majority of flowers are perfect or hermaphrodite, flowering plants have developed numerous morphological and physiological mechanisms to reduce or prevent self-fertilization.
Heteromorphic flowers have short carpels and long stamens, or vice versa, so animal pollinators cannot transfer pollen to the pistil. Homomorphic flowers may employ a biochemical mechanism called self-incompatibility to discriminate between self and non-self pollen grains. In other species, the male and female parts are morphologically separated, developing on different flowers; the botanical term "Angiosperm", from the Ancient Greek αγγείον, angeíon and σπέρμα, was coined in the form Angiospermae by Paul Hermann in 1690, as the name of one of his primary divisions of the plant kingdom. This included flowering plants possessing seeds enclosed in capsules, distinguished from his Gymnospermae, or flowering plants with achenial or schizo-carpic fruits, the whole fruit or each of its pieces being here regarded as a seed and naked; the term and its antonym were maintained by Carl Linnaeus with the same sense, but with restricted application, in the names of the orders of his class Didynamia. Its use with any