1.
Chordate
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Chordates are deuterostomes, as during the embryo development stage the anus forms before the mouth. They are also bilaterally symmetric coelomates, in the case of vertebrate chordates, the notochord is usually replaced by a vertebral column during development, and they may have body plans organized via segmentation. There are also additional extinct taxa, the Vertebrata are sometimes considered as a subgroup of the clade Craniata, consisting of chordates with a skull, the Craniata and Tunicata compose the clade Olfactores. Of the more than 65,000 living species of chordates, the worlds largest and fastest animals, the blue whale and peregrine falcon respectively, are chordates, as are humans. Fossil chordates are known from at least as early as the Cambrian explosion, Hemichordata, which includes the acorn worms, has been presented as a fourth chordate subphylum, but it now is usually treated as a separate phylum. The Hemichordata, along with the Echinodermata, form the Ambulacraria, the Chordata and Ambulacraria form the superphylum Deuterostomia, composed of the deuterostomes. Attempts to work out the relationships of the chordates have produced several hypotheses. All of the earliest chordate fossils have found in the Early Cambrian Chengjiang fauna. Because the fossil record of early chordates is poor, only molecular phylogenetics offers a prospect of dating their emergence. However, the use of molecular phylogenetics for dating evolutionary transitions is controversial and it has also proved difficult to produce a detailed classification within the living chordates. Attempts to produce family trees shows that many of the traditional classes are paraphyletic. While this has been known since the 19th century, an insistence on only monophyletic taxa has resulted in vertebrate classification being in a state of flux. Although the name Chordata is attributed to William Bateson, it was already in prevalent use by 1880, ernst Haeckel described a taxon comprising tunicates, cephalochordates, and vertebrates in 1866. Though he used the German vernacular form, it is allowed under the ICZN code because of its subsequent latinization, among the vertebrate sub-group of chordates the notochord develops into the spine, and in wholly aquatic species this helps the animal to swim by flexing its tail. In fish and other vertebrates, this develops into the spinal cord, the pharynx is the part of the throat immediately behind the mouth. In fish, the slits are modified to form gills, a muscular tail that extends backwards behind the anus. This is a groove in the wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus and it also stores iodine, and may be a precursor of the vertebrate thyroid gland
2.
Leaf
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A leaf is an organ of a vascular plant and is the principal lateral appendage of the stem. The leaves and stem together form the shoot, Leaves are collectively referred to as foliage, as in autumn foliage. Although leaves can be seen in different shapes, sizes and textures, typically a leaf is a thin, dorsiventrally flattened organ, borne above ground. Most leaves have distinctive upper surface and lower surface that differ in colour, hairiness, broad, flat leaves with complex venation are known as megaphylls and the species that bear them, the majority, as broad-leaved or megaphyllous plants. In others, such as the clubmosses, with different evolutionary origins, some leaves, such as bulb scales are not above ground, and in many aquatic species the leaves are submerged in water. Succulent plants often have thick juicy leaves, but some leaves are without major photosynthetic function and may be dead at maturity, as in some cataphylls, furthermore, several kinds of leaf-like structures found in vascular plants are not totally homologous with them. Examples include flattened plant stems called phylloclades and cladodes, and flattened leaf stems called phyllodes which differ from both in their structure and origin. Many structures of plants, such as the phyllids of mosses and liverworts and even of some foliose lichens. Leaves are the most important organs of most vascular plants and these are then further processed by chemical synthesis into more complex organic molecules such as cellulose, the basic structural material in plant cell walls. The plant must therefore bring these three together in the leaf for photosynthesis to take place. Once sugar has been synthesized, it needs to be transported to areas of growth such as the plant shoots and roots. Vascular plants transport sucrose in a tissue called the phloem. The phloem and xylem are parallel to each other but the transport of materials is usually in opposite directions. Within the leaf these vascular systems branch to form veins which supply as much as the leaf as possible and they are arranged on the plant so as to expose their surfaces to light as efficiently as possible without shading each other, but there are many exceptions and complications. For instance plants adapted to windy conditions may have pendent leaves, such as in many willows, the flat, or laminar, shape also maximises thermal contact with the surrounding air, promoting cooling. Functionally, in addition to photosynthesis the leaf is the site of transpiration and guttation. Many gymnosperms have thin needle-like or scale-like leaves that can be advantageous in cold climates with frequent snow and these are interpreted as reduced from megaphyllous leaves of their Devonian ancestors. For xerophytes the major constraint is not light flux or intensity, some window plants such as Fenestraria species and some Haworthia species such as Haworthia tesselata and Haworthia truncata are examples of xerophytes. and Bulbine mesembryanthemoides
3.
Plant morphology
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Plant morphology or phytomorphology is the study of the physical form and external structure of plants. This is usually considered distinct from plant anatomy, which is the study of the structure of plants. Plant morphology is useful in the identification of plants. Plant morphology represents a study of the development, form, and structure of plants, and, by implication, there are four major areas of investigation in plant morphology, and each overlaps with another field of the biological sciences. When structures in different species are believed to exist and develop as a result of common, inherited genetic pathways, for example, the leaves of pine, oak, and cabbage all look very different, but share certain basic structures and arrangement of parts. The homology of leaves is a conclusion to make. This aspect of plant morphology overlaps with the study of plant evolution, secondly, plant morphology observes both the vegetative structures of plants, as well as the reproductive structures. The vegetative structures of plants includes the study of the shoot system, composed of stems and leaves. The reproductive structures are varied, and are usually specific to a particular group of plants, such as flowers and seeds, fern sori. The detailed study of structures in plants led to the discovery of the alternation of generations found in all plants. This area of plant morphology overlaps with the study of biodiversity, thirdly, plant morphology studies plant structure at a range of scales. At the smallest scales are ultrastructure, the structural features of cells visible only with the aid of an electron microscope, and cytology. At this scale, plant morphology overlaps with plant anatomy as a field of study, at the largest scale is the study of plant growth habit, the overall architecture of a plant. The pattern of branching in a tree will vary from species to species, as will the appearance of a plant as a tree, herb, fourthly, plant morphology examines the pattern of development, the process by which structures originate and mature as a plant grows. While animals produce all the parts they will ever have from early in their life. A living plant always has embryonic tissues, a morphologist studies this process, the causes, and its result. This area of plant morphology overlaps with plant physiology and ecology, a plant morphologist makes comparisons between structures in many different plants of the same or different species. Making such comparisons between structures in different plants tackles the question of why the structures are similar
4.
Taxonomy (biology)
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Taxonomy is the science of defining groups of biological organisms on the basis of shared characteristics and giving names to those groups. The exact definition of taxonomy varies from source to source, but the core of the remains, the conception, naming. There is some disagreement as to whether biological nomenclature is considered a part of taxonomy, the broadest meaning of taxonomy is used here. The word taxonomy was introduced in 1813 by Candolle, in his Théorie élémentaire de la botanique, the term alpha taxonomy is primarily used today to refer to the discipline of finding, describing, and naming taxa, particularly species. In earlier literature, the term had a different meaning, referring to morphological taxonomy, ideals can, it may be said, never be completely realized. They have, however, a value of acting as permanent stimulants. Some of us please ourselves by thinking we are now groping in a beta taxonomy, turrill thus explicitly excludes from alpha taxonomy various areas of study that he includes within taxonomy as a whole, such as ecology, physiology, genetics, and cytology. He further excludes phylogenetic reconstruction from alpha taxonomy, thus, Ernst Mayr in 1968 defined beta taxonomy as the classification of ranks higher than species. This activity is what the term denotes, it is also referred to as beta taxonomy. How species should be defined in a group of organisms gives rise to practical and theoretical problems that are referred to as the species problem. The scientific work of deciding how to define species has been called microtaxonomy, by extension, macrotaxonomy is the study of groups at higher taxonomic ranks, from subgenus and above only, than species. While some descriptions of taxonomic history attempt to date taxonomy to ancient civilizations, earlier works were primarily descriptive, and focused on plants that were useful in agriculture or medicine. There are a number of stages in scientific thinking. Early taxonomy was based on criteria, the so-called artificial systems. Later came systems based on a complete consideration of the characteristics of taxa, referred to as natural systems, such as those of de Jussieu, de Candolle and Bentham. The publication of Charles Darwins Origin of Species led to new ways of thinking about classification based on evolutionary relationships and this was the concept of phyletic systems, from 1883 onwards. This approach was typified by those of Eichler and Engler, the advent of molecular genetics and statistical methodology allowed the creation of the modern era of phylogenetic systems based on cladistics, rather than morphology alone. Taxonomy has been called the worlds oldest profession, and naming and classifying our surroundings has likely been taking place as long as mankind has been able to communicate
5.
Leaflet (botany)
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A leaflet in botany is a leaf-like part of a compound leaf. Though it resembles a leaf, a leaflet is not borne on a main plant stem or branch, as a leaf is. Compound leaves are common in many plant families and they differ widely in morphology, the two main classes of compound leaf morphology are palmate and pinnate. For example, a plant has palmate compound leaves, whereas some species of Acacia have pinnate leaves. The ultimate free division of a leaf, or a pinnate subdivision of a multipinnate leaf is called a pinnule or pinnula
6.
Petiole (botany)
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In botany, the petiole is the stalk that attaches the leaf blade to the stem. The petiole is the transition between the stem and the leaf blade, outgrowths appearing on each side of the petiole in some species are called stipules. Leaves lacking a petiole are called sessile or epetiolate, the petiole is a stalk that attaches a leaf to the plant stem. In petiolate leaves, the stalk may be long, as in the leaves of celery and rhubarb, short or completely absent. Subpetiolate leaves are petiolate, or have an extremely short petiole. The broomrape family Orobanchaceae is an example of a family in which the leaves are always sessile, in some other plant groups, such as the speedwell genus Veronica, petiolate and sessile leaves may occur in different species. In the grasses the leaves are apetiolate, but the blade may be narrowed at the junction with the leaf sheath to form a pseudopetiole. In plants with leaves, the leaflets are attached to a continuation of the petiole called the rachis. Each leaflet may be attached to the rachis by a stalk called the petiolule. There may be swollen regions at either end of the known as pulvina that are composed of a flexible tissue that allows leaf movement. Pulvina are common in the bean family Fabaceae and the plant family Marantaceae. A pulvinus on a petiolule is called a pulvinulus, in some plants, the petioles are flattened and widened, to become phyllodes or phyllodia, or cladophylls and the true leaves may be reduced or absent. Thus, the comes to serve the functions of the leaf. Phyllodes are common in the genus Acacia, especially the Australian species, in Acacia koa, the phyllodes are leathery and thick, allowing the tree to survive stressful environments. The petiole allows partially submerged hydrophytes to have leaves floating at different depths, in plants such as rhubarb, celery, artichokes and cardoons the petioles are cultivated as edible crops. The petiole of rhubarb grows directly from the rhizome and produces the leaf at its end, botanically it is categorized as a vegetable and culinarily used as a fruit. Petiole is pronounced /ˈpiːtᵻoʊl/ and comes from Latin petiolus, or peciolus little foot, stem, the regular diminutive pediculus is also used for foot stalk
7.
Rachis
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Rachis /ˈreɪkᵻs/ is a biological term for a main axis or shaft. In vertebrates a rachis can refer to the series of articulated vertebrae, in this case the rachis usually forms the supporting axis of the body and is then called the spine or vertebral column. Rachis can also mean the central shaft of pennaceous feathers, in the gonad of the invertebrate nematode C. The rachis is filled with cytoplasm, in plants, a rachis is the main axis of a compound structure. It can be the stem of a compound leaf, such as in Acacia or ferns, or the main. A ripe head of wheat is easily shattered into dispersal units when touched or blown by the wind. A series of abscission layers forms that divides the rachis into dispersal units consisting of a group of flowers attached to a short segment of the rachis. This is significant in the history of agriculture, and referred to by archaeologists as a brittle rachis, one type of shattering in crop plants
8.
Flowering plant
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The flowering plants, also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants, with 416 families, approx. 13,164 known genera and a total of c.295,383 known species, etymologically, angiosperm means a plant that produces seeds within an enclosure, in other words, a fruiting plant. The term angiosperm comes from the Greek composite word meaning enclosed seeds, the ancestors of flowering plants diverged from gymnosperms in the Triassic Period, during the range 245 to 202 million years ago, and the first flowering plants are known from 160 mya. They diversified extensively during the Lower Cretaceous, became widespread by 120 mya, angiosperms differ from other seed plants in several ways, described in the table. These distinguishing characteristics taken together have made the angiosperms the most diverse and numerous land plants, 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 xylem and phloem form concentric rings, in the dicotyledons, the bundles in the very 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, the soft phloem becomes crushed, but the hard wood persists and forms the bulk of the stem and branches of the woody perennial. Among the monocotyledons, the bundles are more numerous in the stem and are scattered through the ground tissue. They contain no cambium and 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, and 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 on a shoot or from the axil of a leaf, occasionally, as in violets, a flower arises singly in the axil of an ordinary foliage-leaf. There are two kinds of cells produced by flowers. Microspores, which divide to become pollen grains, are the male cells and are borne in the stamens. The female cells called megaspores, which divide to become the egg cell, are contained in the ovule. The flower may consist only of parts, as in willow. Usually, other structures are present and serve to protect the sporophylls, the individual members of these surrounding structures are known as sepals and petals. The outer series is usually green and leaf-like, and functions to protect the rest of the flower, the inner series is, in general, white or brightly colored, and is more delicate in structure. It functions to attract insect or bird pollinators, attraction is effected by color, scent, and nectar, which may be secreted in some part of the flower
9.
Stipule
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In botany, stipule is a term coined by Linnaeus which refers to outgrowths borne on either side of the base of a leafstalk. A pair of stipules is considered part of the anatomy of the leaf of a flowering plant. In some older botanical writing, the term stipule was used generally to refer to any small leaves or leaf-parts. The position of stipules on a plant varies widely from species to species, stipules are most common on dicotyledons, where they appear in pairs alongside each leaf. Some monocotyledon plants display stipule-like structures, but only one per leaf. A relationship exists between the anatomy of the node and the presence or absence of stipules, most plants with trilacunar nodes have stipules, species with unilacunar nodes lack stipules. Stipules are morphologically variable and might appear as glands, scales, hairs, spines, if a single stipule goes all the way around the stem, it is known as an ochrea. The three types of stipules according to duration are caducous, deciduous and persistent, caducous stipules fall off before the leaf unfolds, while deciduous stipules fall off immediately after the leaf unfolds. Persistent stipules remain attached to the plant, stipules can be considered free lateral, adnate, interpetiolar, intrapetiolar, ochreate, foliaceous, bud scales, tendrillar or spiny. A stipule can be fused to the stem, or to the other stipule from the same node, a stipule is adnate if its fused together on part of the petiole length, but the anterior is still free. A stipule is intrapetiolar if it is located in the angle thats between a stem and a petiole, in this case, the two stipules generally form together and appear to be one stipule. A stipule is ochreate if a single stipule appears to be a tube that goes all the way around the stem. A stipule is foliaceous if it is leaf-like and these are generally used to photosynthesize. A stipule is considered a bud scale if it is hard or scaly and these generally fall off as soon as the leaf unfolds. A stipule is considered tendrillar if they are long thin tendrils, a stipule is considered spiny if they are long and pointy. These are generally used to deter animals, a stipule is considered to be abaxial, counter or leaf opposed if its located on the opposite side to where the leaf meets the stem. Stipules can be used by the plants in various ways, and it is known that foliaceous stipules are used like leaves to make energy for the plants. Sometimes stipules protect the next leaf or bud as it grows in, then falls off after the leaf unfolds, stipules can be used as climbing tendrils by climbing plants
10.
Parity (mathematics)
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Parity is a mathematical term that describes the property of an integers inclusion in one of two categories, even or odd. An integer is even if it is divisible by two and odd if it is not even. For example,6 is even there is no remainder when dividing it by 2. By contrast,3,5,7,21 leave a remainder of 1 when divided by 2, examples of even numbers include −4,0,8, and 1738. In particular, zero is an even number, some examples of odd numbers are −5,3,9, and 73. Parity does not apply to non-integer numbers and this classification applies only to integers, i. e. non-integers like 1/2,4.201, or infinity are neither even nor odd. The sets of even and odd numbers can be defined as following and that is, if the last digit is 1,3,5,7, or 9, then it is odd, otherwise it is even. The same idea will work using any even base, in particular, a number expressed in the binary numeral system is odd if its last digit is 1 and even if its last digit is 0. In an odd base, the number is according to the sum of its digits – it is even if. The following laws can be verified using the properties of divisibility and they are a special case of rules in modular arithmetic, and are commonly used to check if an equality is likely to be correct by testing the parity of each side. As with ordinary arithmetic, multiplication and addition are commutative and associative in modulo 2 arithmetic, however, subtraction in modulo 2 is identical to addition, so subtraction also possesses these properties, which is not true for normal integer arithmetic. The structure is in fact a field with just two elements, the division of two whole numbers does not necessarily result in a whole number. For example,1 divided by 4 equals 1/4, which is neither even nor odd, since the concepts even, but when the quotient is an integer, it will be even if and only if the dividend has more factors of two than the divisor. The ancient Greeks considered 1, the monad, to be neither odd nor fully even. It is this, that two relatively different things or ideas there stands always a third, in a sort of balance. Thus, there is here between odd and even numbers one number which is neither of the two, similarly, in form, the right angle stands between the acute and obtuse angles, and in language, the semi-vowels or aspirants between the mutes and vowels. A thoughtful teacher and a pupil taught to think for himself can scarcely help noticing this, integer coordinates of points in Euclidean spaces of two or more dimensions also have a parity, usually defined as the parity of the sum of the coordinates. For instance, the cubic lattice and its higher-dimensional generalizations
