name two phyla of animals that are radially symmetrical
Echinodermata Cnidaria
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Most radially symmetric animals are symmetrical about an axis extending from the center of the oral surface, which contains the mouth to the center of the opposite, , end. Radial symmetry is especially suitable for sessile animals such as the sea anemone, floating animals such as jellyfish, and slow moving organisms such as starfish. Animals in the phyla Cnidaria and Echinodermata are radially symmetric, although many sea anemones and some corals have bilateral symmetry defined by a single structure, the siphonoglyph. Many flowers are radially symmetric or actinomorphic. Roughly identical flower parts – petals, sepals, and stamens – occur at
Symmetry in biology
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All known bilaterian animals are triploblastic, and all known triploblastic animals are bilaterian. Living echinoderms (sea stars, sea urchins, sea cucumbers, etc.) 'look' radially symmetrical (like wheels) rather than bilaterian, but their larvae exhibit bilateral symmetry and some of the earliest echinoderms may have been bilaterally symmetrical. Porifera and Cnidaria are radially symmetrical, not bilaterian, and not triploblastic. The term "Coelomate" means having a body cavity (coelom) containing the internal organs. Most of the phyla featured in the debate about the Cambrian explosion are coelomates: arthropods, annelid worms, molluscs, echinoderms, and chordates – the noncoelomate priapulids are an important exception.
Cambrian explosion
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Most radially symmetric animals are symmetrical about an axis extending from the center of the oral surface, which contains the mouth to the center of the opposite, , end. Radial symmetry is especially suitable for sessile animals such as the sea anemone, floating animals such as jellyfish, and slow moving organisms such as starfish. Animals in the phyla Cnidaria and Echinodermata are radially symmetric, although many sea anemones and some corals have bilateral symmetry defined by a single structure, the siphonoglyph. Many flowers are radially symmetric or actinomorphic. Roughly identical flower parts – petals, sepals, and stamens – occur at
Symmetry in biology
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system of internal radial canals and tentacles along the outer margin of the fossil, with the three oval ridges described as imprints of mouth lobes or gonades. Later, with the discovery of the closely related "Anfesta" and with their seeming affinities to "Tribrachidium", Fedonkin appointed these animals to the Trilobozoa , an extinct group of the tri-radially symmetrical coelenterate-like animals that only superficially resembled cnidarians. Originally, Trilobozoa was established as a class in the phylum Coelenterata, but since Coelenterata has been divided into two separate phyla, Cnidaria and Ctenophora, Trilobozoa itself has been promoted to the rank of phylum. According
Albumares
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"Albumares" and "Anfesta", along with the discoveries of much better-preserved Russian specimens, Mikhail Fedonkin proposed for these animals the new taxon, Trilobozoa – an extinct group of tri-radially symmetrical coelenterate-grade animals. Originally, Trilobozoa was erected as a separate class in the phylum Coelenterata, but since Coelenterata was divided into separate phyla Cnidaria and Ctenophora, the Trilobozoa have been transferred to the rank of phylum. M. Fedonkin has shown that the fossil of "Tribrachidium" is an imprint of the upper side of the animal's body, with some elements of its external and internal anatomy. The radial furrows on the fossil are
Tribrachidium
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Gastrovascular cavity The gastrovascular cavity is the primary organ of digestion and circulation in two major animal phyla: the Cnidaria (including jellyfish and corals) and Platyhelminthes (flatworms). The cavity may be extensively branched into a system of canals. In cnidarians, the gastrovascular system is also known as the coelenteron, and is commonly known as a "blind gut" or "blind sac", since food enters and waste exits through the same orifice. The radially symmetrical cnidarians have a sac-like body in two distinct layers, the epidermis and gastrodermis, with a jellylike layer called the mesoglea between. Extracellular digestion takes place within the
Gastrovascular cavity
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central cavity of the sac-like body. This cavity has only one opening to the outside which, in most cnidarians, is surrounded by tentacles for capturing prey. Gastrovascular cavity The gastrovascular cavity is the primary organ of digestion and circulation in two major animal phyla: the Cnidaria (including jellyfish and corals) and Platyhelminthes (flatworms). The cavity may be extensively branched into a system of canals. In cnidarians, the gastrovascular system is also known as the coelenteron, and is commonly known as a "blind gut" or "blind sac", since food enters and waste exits through the same orifice. The radially symmetrical cnidarians
Gastrovascular cavity
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Cnidaria Cnidaria () is a phylum under Kingdom Animalia containing over 11,000 species of animals found exclusively in aquatic (freshwater and marine) environments: they are a predominantly marine species. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick. They have two basic body forms: swimming medusae and sessile polyps, both of which are radially symmetrical with mouths surrounded by tentacles that bear cnidocytes. Both forms have a single orifice and body cavity that are
Cnidaria
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animals as "Anfesta", "Albumares" and "Tribrachidium" to the separate group Trilobozoa, populated by three-lobed, radially symmetric, coelenterate-grade animals that only superficially resemble cnidarians. Originally, Trilobozoa was established as a class within the phylum Coelenterata, but since Coelenterata was divided into separate phyla - Cnidaria and Ctenophora - the Trilobozoa have been transferred to rank of phylum. According to the latest research, "Anfesta" was a soft-bodied benthic organism that temporarily attached (but did not adhere) to the substrate of its habitat (microbial mats). This fossil is an imprint of the upper side of the animal body, with some elements of its
Anfesta stankovskii
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Coelenterata Coelenterata is an obsolete term encompassing the animal phyla Cnidaria (coral animals, true jellies, sea anemones, sea pens, and their allies) and Ctenophora (comb jellies). The name comes from the Greek ""koilos"" ("hollow") and ""enteron"" ("intestine"), referring to the hollow body cavity common to these two phyla. They have very simple tissue organization, with only two layers of cells (external and internal), and radial symmetry. Some examples are corals, which are typically colonial, and hydra, jelly fish and sea anemones which are solitary. Coelenterata lack a specialized circulatory system relying instead on diffusion across the tissue layers. All coelenterates
Coelenterata
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are aquatic, mostly marine. The bodyform is radially symmetrical, diploblastic and does not have a coelom. The body has a single opening, the hypostome, surrounded by sensory tentacles equipped with either nematocysts or colloblasts to capture mostly planktonic prey. These tentacles are surrounded by a spacious cavity called the gastrovascular cavity or coelenteron. Digestion is both intracellular and extracellular. Respiration and excretion are accomplished by simple diffusion. A network of nerves is spread throughout the body. Many Cnidaria exhibit polymorphism, wherein different types of individuals are present in a colony for different functions. These individuals are called Zooids. These animals
Coelenterata
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including homeodomain proteins involved in the control of development. The phylogenetic tree (of major lineages only) indicates approximately how many millions of years ago () the lineages split. Several animal phyla lack bilateral symmetry. Among these, the sponges (Porifera) probably diverged first, representing the oldest animal phylum. Sponges lack the complex organization found in most other animal phyla; their cells are differentiated, but in most cases not organised into distinct tissues. They typically feed by drawing in water through pores. The Ctenophora (comb jellies) and Cnidaria (which includes jellyfish, sea anemones, and corals) are radially symmetric and have digestive chambers
Animal
534255
analyses by molecular phylogeny are confident that members of Lophotrochozoa are more closely related to each other than of non-members, the relationships between members are mostly unclear. Most protostome phyla outside the Lophotrochozoa are members of Ecdysozoa ("animals that molt"), which include Arthropoda, Nematoda and Priapulida. Most other bilaterian phyla are in the Deuterostomia, which include Echinodermata and Chordata. The Acoelomorpha, which are neither protostomes nor deuterostomes, are regarded as basal bilaterians. Nemertea Nemertea is a phylum of invertebrate animals also known as "ribbon worms" or "proboscis worms". Alternative names for the phylum have included Nemertini, Nemertinea and Rhynchocoela. Although
Nemertea
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unmistakable bilateral symmetry as larvae, and are now in the Bilateria. Ctenophores exhibit biradial or rotational symmetry, defined by tentacular and pharyngeal axes, on which two anal canals are located in two diametrically opposed quadrants. Some species within the cnidarian class Anthozoa are bilaterally symmetric (For example, "Nematostella vectensis"). It has been suggested that bilateral symmetry may have evolved before the split between Cnidaria and Bilateria, and that the radially symmetrical cnidarians have secondarily evolved radial symmetry, meaning the bilaterality in cnidarian species like "N. vectensis" has a primary origin. The differing definitions assigned by zoologists are listed in the
Radiata
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zoology. Animals may be listed or indexed by many criteria, including taxonomy, status as endangered species, their geographical location, and their portrayal and/or naming in human culture. List of extinct animals List of fictional bears The animal Kingdom contains some 35 extant phyla. Basal animals are according to the following cladogram: Animals: Porifera, Diploblasts Diploblasts: Ctenophora, ParaHoxozoa ParaHoxozoa: Placozoa, Cnidaria, Bilateria/Triploblast Bilateria: Xenacoelomorpha, Nephrozoa Nephrozoa: Protostomes, Deuterostomes Lists of animals Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, reproduce sexually, and grow from a
Lists of animals
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other animals. A series of studies that looked at the presence and absence of members of gene families and signalling pathways (e.g., homeoboxes, nuclear receptors, the Wnt signaling pathway, and sodium channels) showed evidence congruent with the latter two scenarios, that ctenophores are either sister to Cnidaria, Placozoa, and Bilateria or sister to all other animal phyla. Several more recent studies comparing complete sequenced genomes of ctenophores with other sequenced animal genomes have also supported ctenophores as the sister lineage to all other animals. This position would suggest that neural and muscle cell types either were lost in major animal
Ctenophora
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Ernst Haeckel's Gastraea hypothesis. He proposed that the Bilaterogastraea had a two-stage life cycle, with a pelagic juvenile and a benthic adult stage. The invagination of the original gastrula stage he saw as bilaterally symmetric rather than radially symmetric. Proposed by Élie Metchnikoff. Urmetazoan The Urmetazoan is the name for the hypothetical last common ancestor of all animals. It was undoubtedly a flagellate marine eukaryote, but beyond this its form is difficult to determine because the relationships of animal phyla are not completely understood. All animals are posited by biologists to have evolved from a flagellated eukaryote. Their closest known
Urmetazoan
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of longitudinal muscles, that shorten the body; these enable soft-bodied animals with a hydrostatic skeleton to move by peristalsis. They also have a gut that extends through the basically cylindrical body from mouth to anus. Many bilaterian phyla have primary larvae which swim with cilia and have an apical organ containing sensory cells. However, there are exceptions to each of these characteristics; for example, adult echinoderms are radially symmetric (unlike their larvae), while some parasitic worms have extremely simplified body structures. Genetic studies have considerably changed zoologists' understanding of the relationships within the Bilateria. Most appear to belong to two
Animal
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The earliest trilobite fossils are about 530 million years old, but the class was already quite diverse and worldwide, suggesting they had been around for quite some time. The fossil record of trilobites began with the appearance of trilobites with mineral exoskeletons – not from the time of their origin. The earliest generally accepted echinoderm fossils appeared a little bit later, in the Late Atdabanian; unlike modern echinoderms, these early Cambrian echinoderms were not all radially symmetrical. These provide firm data points for the "end" of the explosion, or at least indications that the crown groups of modern phyla were
Cambrian explosion
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symmetry "from a presumably radially symmetrical ancestor." Not all animals are symmetric. Many members of the phylum Porifera (sponges) have no symmetry, though some are radially symmetric. It is normal for essentially symmetric animals to show some measure of asymmetry. Usually in humans the left brain is structured differently to the right; the heart is positioned towards the left; and the right hand functions better than the left hand. The scale-eating cichlid "Perissodus microlepis" develops left or right asymmetries in their mouths and jaws that allow them to be more effective when removing scales from the left or right flank
Symmetry in biology
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jelly-like layer. Hence, cnidarians and ctenophores have traditionally been labelled diploblastic, along with sponges. However, both cnidarians and ctenophores have a type of muscle that, in more complex animals, arises from the middle cell layer. As a result, some recent text books classify ctenophores as triploblastic, and it has been suggested that cnidarians evolved from triploblastic ancestors. Most adult cnidarians appear as either free-swimming medusae or sessile polyps, and many hydrozoans species are known to alternate between the two forms. Both are radially symmetrical, like a wheel and a tube respectively. Since these animals have no heads, their ends are
Cnidaria
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rely on maintaining a constant water flow through their bodies to obtain food and oxygen and to remove wastes. Sponges were first to branch off the evolutionary tree from the common ancestor of all animals, making them the sister group of all other animals. The term sponge derives from the Ancient Greek word (). Sponges are similar to other animals in that they are multicellular, heterotrophic, lack cell walls and produce sperm cells. Unlike other animals, they lack true tissues and organs. Some of them are radially symmetrical, but most are asymmetrical. The shapes of their bodies are adapted for
Sponge
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as the radially symmetrical Hydrozoa, show some degree of cephalization. The Anthomedusae have a head end with their mouth, photoreceptive cells, and a concentration of neural cells. Cephalization is a characteristic feature of the Bilateria, a large group containing the majority of animal phyla. These have the ability to move, using muscles, and a body plan with a front end that encounters stimuli first as the animal moves forwards, and accordingly has evolved to contain many of the body's sense organs, able to detect light, chemicals, and often sound. There is often also a collection of nerve cells able to
Cephalization
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way of life. Minerva has an atmosphere similar to Earth's and breathable by humans, and liquid water exists in significant quantities on the surface. The planet's mean atmospheric temperature is lower than Earth's due to the greater distance from the sun, although the greenhouse effect of its thicker atmosphere means that it is not as cold as our universe's Mars. The ancient astronomers of the novel name the bright blue/gray planet Minerva after the goddess of wisdom. Minervan animals (including the sentient Minervans) are hexameristically radially symmetrical. This means that they have six eyes spaced equally all around, see in
A World of Difference (novel)
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shorten the body; these enable soft-bodied animals with a hydrostatic skeleton to move by peristalsis. They also have a gut that extends through the basically cylindrical body from mouth to anus. Many bilaterian phyla have primary larvae which swim with cilia and have an apical organ containing sensory cells. However, there are exceptions to each of these characteristics; for example, adult echinoderms are radially symmetric (unlike their larvae), and certain parasitic worms have extremely simplified body structures. The hypothetical most recent common ancestor of all bilateria is termed the "Urbilaterian". The nature of the first bilaterian is a matter of
Bilateria
9446
oesophagus, respiratory airways, and blood vessels. Cardiac muscle is found only in the heart, allowing it to contract and pump blood round the body. Nervous tissue is composed of many nerve cells known as neurons which transmit information. In some slow-moving radially symmetrical marine animals such as ctenophores and cnidarians (including sea anemones and jellyfish), the nerves form a nerve net, but in most animals they are organized longitudinally into bundles. In simple animals, receptor neurons in the body wall cause a local reaction to a stimulus. In more complex animals, specialized receptor cells such as chemoreceptors and photoreceptors are
Anatomy
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important in animal taxonomy; the Radiata, animals with radial symmetry, formed one of the four branches of Georges Cuvier's classification of the animal kingdom. Radially symmetric organisms resemble a pie where several cutting planes produce roughly identical pieces. Such an organism exhibits no left or right sides. They have a top and a bottom surface, or a front and a back. Symmetry has been important historically in the taxonomy of animals; Georges Cuvier classified animals with radial symmetry in the taxon Radiata ("Zoophytes"), which is now generally accepted to be a polyphyletic assemblage of different phyla of the Animal kingdom.
Symmetry in biology
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taxon Agnotozoa. There are a few likely reasons for this. Wikispecies places the mesozoans in kingdom protista. Agnotozoa Agnotozoa is the name of a taxon of simple animals. The name first appeared in an invertebrate paleontology book as one of the "branches" of the subkingdom Metazoa. The branch contained only one group: Mesozoa. More recently, some have used the name to refer to a sub-kingdom of three small phyla of simple animals without organs. These phyla are Placozoa, Orthonectida, and Rhombozoa. They still have differentiated tissue, but that tissue is only organized in simple ways; for example, by being layered.
Agnotozoa
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Agnotozoa Agnotozoa is the name of a taxon of simple animals. The name first appeared in an invertebrate paleontology book as one of the "branches" of the subkingdom Metazoa. The branch contained only one group: Mesozoa. More recently, some have used the name to refer to a sub-kingdom of three small phyla of simple animals without organs. These phyla are Placozoa, Orthonectida, and Rhombozoa. They still have differentiated tissue, but that tissue is only organized in simple ways; for example, by being layered. The Orthonectida and Rhombozoa are also grouped into the Mesozoa. Biologists today generally do not use the
Agnotozoa
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Bilateria The Bilateria , bilaterians, or triploblasts, are animals with bilateral symmetry, i.e., they have a head (anterior) and a tail (posterior) as well as a back (dorsal) and a belly (ventral); therefore they also have a left side and a right side. The bilateria are a major group of animals, including the majority of phyla but not sponges, ctenophores, placozoans, and cnidarians. For the most part, bilateral embryos are triploblastic, having three germ layers: endoderm, mesoderm, and ectoderm. Nearly all are bilaterally symmetrical, or approximately so; the most notable exception is the echinoderms, which achieve near-radial symmetry as adults,
Bilateria
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subgroup of "Epilobium". "Chamaenerion" can be distinguished from "Epilobium" by features which include: having leaves mostly spirally arranged rather than mostly opposite; having flowers that are zygomorphic rather than mainly radially symmetrical; and lacking a floral tube and a notch in the petals. A 2007 monograph on the classification of the family Onagraceae accepted the separation of "Epilobium" and "Chamaenerion" (under the name "Chamerion"), dividing "Chamaenerion" into two sections, "Chamaenerion" and "Rosmarinifolium". Differences between the species in the two sections are summarized in the table below. , eight species were recognized, in two sections: "Chamaenerion" is native to the northern
Chamaenerion
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filaments can be fused in various configurations, often in a group of nine stamens plus one separate stamen. Various genes in the "CYCLOIDEA (CYC)/DICHOTOMA (DICH)" family are expressed in the upper (also called dorsal or adaxial) petal; in some species, such as "Cadia", these genes are expressed throughout the flower, producing a radially symmetrical flower. The ovary most typically develops into a legume. A legume is a simple dry fruit that usually dehisces (opens along a seam) on two sides. A common name for this type of fruit is a "pod", although that can also be applied to a few
Fabaceae
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covered with branched hairs (giving rise to the common name of Lamb's-tail). The flowers are radially symmetrical. The Asteliaceae is a family of two to four genera of plants found in the Southern Hemisphere. They are more or less rhizomatous, with spiral leaves and an inflorescence that may form a raceme or a spike. There are large bracts at the base of the inflorescence. The individual flowers are small, with tepals joined at the base. The family includes some 150 species with a worldwide distribution, excluding Europe and northern Asia. Species can be recognized by their rosettes of more or
Families of Asparagales
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3 seeds and small green flowers. The flowers are radially symmetrical, dioecious and have umbel inflorescence of 12 flowers. The berries are produced in the fall or in the late summer and stays intact through the winter for animals and birds to eat. Thus the pollination occurs as the unharmed seeds are found in the feces. The surface of the stem is smooth; it also is bent and have thorns at the joints. The hairy roots of sarsaparilla are fibrous and may have few rootlets growing out. They have stiff surface and are deep-rooted, which grows from 2 to 2.5
Smilax aristolochiifolia
118276
alternate or whorled, simple and without stipules. Their flowers are hermaphrodite and show considerable variability. The petals are often fused (sympetalous) with shapes ranging from narrowly tubular to funnelform or widely urn-shaped. The corollas are usually radially symmetrical (actinomorphic) and urn-shaped, but many flowers of the genus "Rhododendron" are somewhat bilaterally symmetrical (zygomorphic). Anthers open by pores. Adanson used the term Vaccinia to describe a similar family, but Jussieu first used the term Ericaceae. The name comes from the type genus "Erica", which appears to be derived from the Greek word "ereike". The exact meaning is difficult to interpret, but
Ericaceae
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the planet Minerva (a more habitable analogue of Mars). Minervan animals (including the sentient Minervans) are hexameristically radially symmetrical. This means that they have six eyes spaced equally all around, see in all directions and have no "back" where somebody could sneak on them unnoticed. Females (referred to as "mates" by the Minervans) give birth to litters that consist of one male and five females, and the "mates" always die after reproducing because of torrential bleeding from the places where the six fetuses were attached; this gives a population multiplication of 5 per generation if all females live to adolescence
Sex and sexuality in speculative fiction
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structures characteristic of cacti, called "areoles", then occur at the ends of the segments of the stem. In two species the stems are less flattened, more cylinder-shaped, and the areoles are arranged in a more or less spiral pattern all over the segments. In both cases, the areoles, which may have wool and bristles, are where the flower buds appear. The flowers either hang downwards and are almost regular (radially symmetrical or actinomorphic) or, as in most species, are held more or less horizontally with the higher side of the flower different from the lower side (radially asymmetrical or zygomorphic).
Schlumbergera
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of the trunk. Each annulus is essentially identical to its neighbours; the only trunk differentiation is at the anterior and posterior. The anterior is radially symmetrical, typically comprising an introvert, whereas the trunk is bilaterally symmetrical. The posterior hosts the terminal anus and sometimes one or two hooks. There is no one character that unites the palaeoscolecids as a clade (indeed they are likely paraphyletic), and few individual specimens contain all characteristic palaeosolecid traits. Palaeoscolecids are a little tricky to define, and probably represent a paraphyletic grouping. Their most current systematic diagnosis references their annulated worm-like body form, the presence
Palaeoscolecid
18119405
or bilaterian was segmented and that segmentation disappeared in many descendant phyla. The current view is that annelids are grouped with molluscs, brachiopods and several other phyla that have lophophores (fan-like feeding structures) and/or trochophore larvae as members of Lophotrochozoa. Bryozoa may be the most basal phylum (the one that first became distinctive) within the Lophotrochozoa, and the relationships between the other members are not yet known. Arthropods are now regarded as members of the Ecdysozoa ("animals that molt"), along with some phyla that are unsegmented. The "Lophotrochozoa" hypothesis is also supported by the fact that many phyla within this
Annelid
39027
tree of animals, and even about whether they should be regarded as members of the protostomes or deuterostomes, the two major groups that account for all moderately complex animals. Molecular phylogeny, which attempts to work out the evolutionary family tree of organisms by comparing their biochemistry and especially their genes, has done much to clarify the relationships between the better-known invertebrate phyla. However, the shortage of genetic data about "minor phyla" such as bryozoans and entoprocts has left their relationships to other groups unclear. The traditional view is that the Bryozoa are a monophyletic group, in which the class Phylactolaemata
Bryozoa
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divided, sometimes peltate, opposite or alternate and usually have stipules. The flowers are generally regular, or symmetrical. They are hermaphrodite, actinomorphic (radially symmetrical, like in "Geranium") or slightly zygomorphic (with a bilateral symmetry, like in "Pelargonium"). The calyx and the corolla are both pentamerous (with five lobes), petals are free while sepals are connate or united at the base. The androecium consists in two whorls of five stamens each, some of which can be unfertile; the pistil consists of five (less commonly three) merged carpels. The linear stigmas are free, and the ovary is superior. The nectaries are localised at
Geraniaceae
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with a single opening, which serves as both mouth and anus. Animals in both phyla have distinct tissues, but these are not organised into organs. They are diploblastic, having only two main germ layers, ectoderm and endoderm. The tiny placozoans are similar, but they do not have a permanent digestive chamber. The remaining animals, the great majority—comprising some 29 phyla and over a million species—form a clade, the Bilateria. The body is triploblastic, with three well-developed germ layers, and their tissues form distinct organs. The digestive chamber has two openings, a mouth and an anus, and there is an internal
Animal
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digestion of food particles. Albumares Albumares brunsae is a tri-radially symmetrical fossil animal that lived in the late Ediacaran (Vendian) seafloor. It is a member of the extinct group Trilobozoa. The generic name "Albumares" derives from the Latin "Mare Album" (White Sea). The specific name honors Elizabeth P. Bruns, an early 20th-century Russian geologist noted for her extensive and important research of the Upper Precambrian stratigraphy of European Russia. Fossils of the "Albumares brunsae" are known from deposits on the Verkhovka formation on the Syuzma River in the Onega Peninsula of the White Sea, Arkhangelsk Region, Russia. There are reports
Albumares
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Albumares Albumares brunsae is a tri-radially symmetrical fossil animal that lived in the late Ediacaran (Vendian) seafloor. It is a member of the extinct group Trilobozoa. The generic name "Albumares" derives from the Latin "Mare Album" (White Sea). The specific name honors Elizabeth P. Bruns, an early 20th-century Russian geologist noted for her extensive and important research of the Upper Precambrian stratigraphy of European Russia. Fossils of the "Albumares brunsae" are known from deposits on the Verkhovka formation on the Syuzma River in the Onega Peninsula of the White Sea, Arkhangelsk Region, Russia. There are reports about "Albumares" sp. from
Albumares
3521000
blue flowers appear in late spring to early summer (May to June in their native habitat). They are arranged in a raceme at the end of the stem. Each of the radially symmetrical, star-shaped flowers has six petals. There are eight subspecies; The superseded name for "Camassia quamash" "supsp. quamash", "Camassia esculenta" (Nutt.) Lindl., should not be confused with the superseded name "Camassia esculenta" (Ker Gawl.) B.L.Rob., ("nom. illeg".) for "Camassia scilloides". The genus name comes from the Nez Perce Indian name for this plant, and means "sweet". "Qém'es", a term for the plant's bulb, which was gathered and used
Camassia quamash
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a non-living jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick. They have two basic body forms: swimming medusae and sessile polyps, both of which are radially symmetrical with mouths surrounded by tentacles that bear cnidocytes. Both forms have a single orifice and body cavity that are used for digestion and respiration. Fossil cnidarians have been found in rocks formed about . Fossils of cnidarians that do not build mineralized structures are rare. Scientists currently think cnidarians, ctenophores and bilaterians are more closely related to calcareous sponges than these are to other sponges, and that
Marine life
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flower into symmetrical halves by the same number of longitudinal planes passing through the axis: Oleander is an example of a flower without such mirror planes. Actinomorphic flowers are also called radially symmetrical or regular flowers. Other examples of actinomorphic flowers are the lily ("Lilium", Liliaceae) and the buttercup ("Ranunculus", Ranunculaceae). Zygomorphic ("yoke shaped", "bilateral" – from the Greek ζυγόν, "zygon", yoke, and μορφή, "morphe", shape) flowers can be divided by only a single plane into two mirror-image halves, much like a yoke or a person's face. Examples are orchids and the flowers of most members of the Lamiales (e.g.,
Floral symmetry
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animal phyla, making the term almost meaningless for taxonomic purpose. Invertebrate sea life includes the following groups, some of which are phyla: Arthropods total about 1,113,000 described extant species, molluscs about 85,000 and chordates about 52,000. Sponges are animals of the phylum Porifera (Modern Latin for "bearing pores" ). They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through them, consisting of jelly-like mesohyl sandwiched between two thin layers of cells. They have unspecialized cells that can transform into other types and that often migrate between the main cell layers and the mesohyl
Marine invertebrates
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Convolvulaceae Convolvulaceae, known commonly as the bindweed or morning glory family, is a family of about 60 genera and more than 1,650 species of mostly herbaceous vines, but also trees, shrubs and herbs, and also including the sweet potato and a few other food tubers. Convolvulaceae can be recognized by their funnel-shaped, radially symmetrical corolla; the floral formula for the family has five sepals, five fused petals, five epipetalous stamens (stamens fused to the petals), and a two-part syncarpous and superior gynoecium. The stems of these plants are usually winding, hence their Latin name (from "convolvere", "to wind"). The leaves
Convolvulaceae
19576965
Physaria arctica Physaria arctica is a perennial flowering herb of the mustard family, known by the common name arctic bladderpod. Plants are 6–12 cm high with a short taproot and woody stem-base. Basal leaves, 2–6 cm and arranged in a rosette predominate, and are obovate to oblanceolate, while cauline leaves, sessile or shortly petiolate, are oblanceolate or lingulate and 0.5-1.5 cm. Inflorescences are loosely racemose, with flower stalks ascending or erect and 5–20 mm. There are 3-8 radially symmetrical flowers per inflorescence, and the petals are spaulate, 5-6mm, with blades that narrow gradually to the claw. "P. arctica" grows in
Physaria arctica
14527798
medium with dazzling technical and artistic virtuosity. On the outside of the lid there are symmetrical images of a man surrounded by two wolves, a version of the ancient Master of Animals motif. In between these images are two more symmetrical figures, this time depicting an eagle swooping down upon its prey. To the ancient Anglo-Saxons, these images probably held great significance, but to modern historians it is difficult to be sure of the symbolism in these figures. It is possible that the heraldic composition of the men and the wolves alludes to the family name of the Sutton Hoo
Sutton Hoo purse-lid
4676659
Platyzoa The paraphyletic "Platyzoa" are a group of protostome unsegmented animals proposed by Thomas Cavalier-Smith in 1998. Cavalier-Smith included in Platyzoa the phylum Platyhelminthes (or flatworms), and a new phylum, the Acanthognatha, into which he gathered several previously described phyla of microscopic animals. More recently it has been described as paraphyletic, containing the Rouphozoa and the Gnathifera. One scheme placed the following phyla in Platyzoa: None of the Platyzoa groups have a respiration or circulation system because of their small size, flat body or parasitic lifestyle. The Platyhelminthes and Gastrotricha are acoelomate. The other phyla have a pseudocoel, and share
Platyzoa
11427676
thick. They have two basic body forms: swimming medusae and sessile polyps, both of which are radially symmetrical with mouths surrounded by tentacles that bear cnidocytes. Both forms have a single orifice and body cavity that are used for digestion and respiration. Fossil cnidarians have been found in rocks formed about . Fossils of cnidarians that do not build mineralized structures are rare. Scientists currently think cnidarians, ctenophores and bilaterians are more closely related to calcareous sponges than these are to other sponges, and that anthozoans are the evolutionary "aunts" or "sisters" of other cnidarians, and the most closely related
Marine invertebrates
6470060
Invertebrate zoology Invertebrate zoology is the subsystem of zoology that consists of the study of invertebrates, animals without a backbone (a structure which is found only in fish, amphibians, reptiles, birds and mammals.) Invertebrates are a vast and very diverse group of animals that includes sponges, echinoderms, tunicates, numerous different phyla of worms, molluscs, arthropods and many additional phyla. Single-celled organisms or protists are usually not included within the same group as invertebrates. Invertebrates represent 97% of all named animal species, and because of that fact, this subdivision of zoology has many further subdivisions, including but not limited to: These
Invertebrate zoology
6218366
radial grooves on the surface of the living animal, while the three hooked ridges in central part of the fossil are imprints of cavities within the body. "Tribrachidium" was a soft-bodied benthic organism that temporarily attached (but did not accrete) to the substrate of its habitat (microbial mats). Tribrachidium Tribrachidium heraldicum is a tri-radially symmetrical fossil animal that lived in the late Ediacaran (Vendian) seas. In life, it was hemispherical in form. "T. heraldicum" is the best known member of the extinct group Trilobozoa. The generic name "Tribrachidium" is derived from combination of the Greek "τρία" (tria, "three") + Latin
Tribrachidium
1288318
exoskeletons often contain "muscle scars", marks where muscles have been attached to the exoskeleton, which may allow the reconstruction of much of an organism's internal parts from its exoskeleton alone. The most significant limitation is that, although there are 30-plus phyla of living animals, two-thirds of these phyla have never been found as fossils, because most animal species are soft-bodied and decay before they can become fossilized. Mineralized skeletons first appear in the fossil record shortly before the base of the Cambrian period, . The evolution of a mineralized exoskeleton is seen by some as a possible driving force of
Exoskeleton
1448442
jellies. Adult echinoderms, such as starfish, sea urchins, sea cucumbers and others are also included, since they are pentaradial, meaning they have five discrete rotational symmetry. Echinoderm larvae are not included, since they are bilaterally symmetrical. Radially symmetrical organisms always have one distinctive axis. Cnidarians (jellyfish, sea anemones and corals) have an incomplete digestive system, meaning that one end of the organism has a mouth, and the opposite end has no opening from the gut (coelenteron). For this reason, the end of the organism with the mouth is referred to as the oral end (), and the opposite surface is
Anatomical terms of location
10172465
as most probably being early sponges. The oldest animals are found in the Ediacaran biota, towards the end of the Precambrian, around 610 million years ago. It had long been doubtful whether these included animals, but the discovery of the animal lipid cholesterol in fossils of "Dickinsonia" establishes that these were indeed animals. Many animal phyla first appear in the fossil record during the Cambrian explosion, starting about 542 million years ago, in beds such as the Burgess shale. Extant phyla in these rocks include molluscs, brachiopods, onychophorans, tardigrades, arthropods, echinoderms and hemichordates, along with numerous now-extinct forms such as
Animal
8384309
and inconspicuous with lots of pollen grains and large, feathery stigmas to catch the pollen. However, this is relatively uncommon (only 2% of pollination is hydrophily) and most aquatic plants are insect-pollinated, with flowers that emerge into the air. "Vallisneria" is an example. Bee-pollinated flowers can be very variable in their size, shape and colouration. They can be open and bowl-shaped (radially symmetrical) or more complex and non-radially symmetric ("zygomorphic"), as is the case with many peas and foxgloves. Some bee flowers tend to be yellow or blue, often with ultraviolet nectar guides and scent. Nectar, pollen, or both are
Pollination syndrome
12477032
while the phyla may have diversified in this time period, representatives of the crown groups of many phyla do not appear until much later in the Phanerozoic. Further, the mineralised phyla that form the basis of the fossil record may not be representative of other phyla, since most mineralised phyla originated in a benthic setting. The fossil record is consistent with a Cambrian explosion that was limited to the benthos, with pelagic phyla evolving much later. Ecological complexity among marine animals increased in the Cambrian, as well later in the Ordovician. However, recent research has overthrown the once-popular idea that
Cambrian explosion
13009715
Urmetazoan The Urmetazoan is the name for the hypothetical last common ancestor of all animals. It was undoubtedly a flagellate marine eukaryote, but beyond this its form is difficult to determine because the relationships of animal phyla are not completely understood. All animals are posited by biologists to have evolved from a flagellated eukaryote. Their closest known living relatives are the choanoflagellates – collared flagellates whose cell morphology is similar to the choanocyte cells of certain sponges. Molecular studies place animals in a supergroup called the opisthokonts, which also include the choanoflagellates, fungi, and a few small parasitic protists. The
Urmetazoan
15596991
epiphytes) that are perennial, with the exception of four species. Most genera grow from bulbs, but a few such as "Agapanthus", "Clivia" and "Scadoxus" develop from rhizomes (underground stems). The leaves are simple rather fleshy and two-ranked with parallel veins. Leaf shape may be linear, strap like, oblong, elliptic, lanceolate (lance shaped) or filiform (threadlike). The leaves which are either grouped at the base or arranged alternatively on the stem may be sessile or petiolate and possess a meristem. The flowers, which are hermaphroditic (bisexual), are actinomorphic (radially symmetrical), rarely zygomorphic, pedicellate or sessile, and are typically arranged in umbels
Amaryllidaceae
20508938
Pelorism Pelorism is the term, said to be first used by Charles Darwin, for the formation of 'peloric flowers' which botanically is the abnormal production of actinomorphic flowers in a species that usually produces zygomorphic flowers. These flowers are spontaneous floral symmetry mutants. The term epanody is also applied to this phenomenon. Bilaterally symmetrical (zygomorphic) flowers are known to have evolved several times from radially symmetrical (actinomorphic) flowers, these changes being linked to increasing specialisation in pollinators. Pelorism has been of interest since a five-spurred variety of the common toad-flax ("Linaria vulgaris" L.) was first discovered in 1742 by a
Pelorism
328071
and bottom surfaces and distinct head and tail ends. Like other bilaterians, they have three main cell layers (endoderm, mesoderm, and ectoderm), while the radially symmetrical cnidarians and ctenophores (comb jellies) have only two cell layers. Beyond that, they are "defined more by what they do not have than by any particular series of specializations." Unlike other bilaterians, Platyhelminthes have no internal body cavity, so are described as acoelomates. They also lack specialized circulatory and respiratory organs, both of these facts are defining features when classifying a flatworm's anatomy. Their bodies are soft and unsegmented. The lack of circulatory and
Flatworm
18683349
becomes the lead arm and the other arms take on the subordinate role. This shows that a radially symmetrical animal can employ fully coordinated, bilaterally symmetrical locomotion. When attacked by a predator, "O. echinata" sometimes autotomises (sheds) one or more of its arms. In a back-reef habitat in the Florida Keys, up to 47% of the individuals were found to have missing or damaged arms, and it took about two years for individuals with three missing arms to completely regenerate them. Losing a limb rather than its life is beneficial to the brittle star. Although energy must be diverted to
Ophiocoma echinata
6766546
Fibrobacteres Fibrobacteres is a small bacterial phylum which includes many of the major rumen bacteria, allowing for the degradation of plant-based cellulose in ruminant animals. Members of this phylum were categorized in other phyla. The genus "Fibrobacter" (the only genus of Fibrobacteres) was removed from the genus "Bacteroides" in 1988. Although "Fibrobacteres", which consists of a single genus "Fibrobacter" containing two species, is currently recognized as a distinct phylum, phylogenetic studies based RpoC and Gyrase B protein sequences, indicate that "Fibrobacter succinogenes" is closely related to the species from the phyla "Bacteroidetes" and "Chlorobi". The species from these three phyla
Fibrobacteres
19576966
sand and gravel from calcareous bedrock, river bars and terraces, cliff ledges, scree and talus slopes. Physaria arctica Physaria arctica is a perennial flowering herb of the mustard family, known by the common name arctic bladderpod. Plants are 6–12 cm high with a short taproot and woody stem-base. Basal leaves, 2–6 cm and arranged in a rosette predominate, and are obovate to oblanceolate, while cauline leaves, sessile or shortly petiolate, are oblanceolate or lingulate and 0.5-1.5 cm. Inflorescences are loosely racemose, with flower stalks ascending or erect and 5–20 mm. There are 3-8 radially symmetrical flowers per inflorescence, and the
Physaria arctica
1351619
into sufficiently deep soils. "H. non-scripta" differs from "H. hispanica", which occurs as an introduced species in the British Isles, in a number of ways. "H. hispanica" has paler flowers which are borne in radially symmetrical racemes; their tepals are less recurved, and are only faintly scented. The outer stamens are fused with the tepals for less than 75% of their length, and the anthers are the same colour as the tepals. These two species are thought to have diverged 8000 years ago. The two species hybridise readily to produce fertile offspring known as "Hyacinthoides" × "massartiana"; the hybrids are
Hyacinthoides non-scripta
312248
organism or parts of organisms. Further, only the parts of organisms that were already mineralised are usually preserved, such as the shells of molluscs. Since most animal species are soft-bodied, they decay before they can become fossilised. As a result, although there are 30-plus phyla of living animals, two-thirds have never been found as fossils. Occasionally, unusual environments may preserve soft tissues. These lagerstätten allow paleontologists to examine the internal anatomy of animals that in other sediments are represented only by shells, spines, claws, etc. – if they are preserved at all. However, even lagerstätten present an incomplete picture of
Paleontology
289916
that generally set them apart from other living things. Animals are eukaryotic and usually multicellular (although see Myxozoa), which separates them from bacteria, archaea, and most protists. They are heterotrophic, generally digesting food in an internal chamber, which separates them from plants and algae. They are also distinguished from plants, algae, and fungi by lacking cell walls. With a few exceptions—most notably the two phyla consisting of sponges and placozoans—animals have bodies that are differentiated into tissues. These include muscles, which are able to contract and control locomotion, and a nervous system, which sends and processes signals. There is also
Nature
39030
phylogeny, based on anatomy and on the development of the adult forms from embryos, has produced no enduring consensus about the position of ectoprocts. Attempts to reconstruct the family tree of animals have largely ignored ectoprocts and other "minor phyla", which have received little scientific study because they are generally tiny, have relatively simple body plans, and have little impact on human economies – despite the fact that the "minor phyla" include most of the variety in the evolutionary history of animals. In the opinion of Ruth Dewel, Judith Winston, and Frank McKinney, ""Our standard interpretation of bryozoan morphology and
Bryozoa
294303
ganglia. All animals more advanced than sponges have nervous systems. However, even sponges, unicellular animals, and non-animals such as slime molds have cell-to-cell signalling mechanisms that are precursors to those of neurons. In radially symmetric animals such as the jellyfish and hydra, the nervous system consists of a nerve net, a diffuse network of isolated cells. In bilaterian animals, which make up the great majority of existing species, the nervous system has a common structure that originated early in the Ediacaran period, over 550 million years ago. The nervous system contains two main categories or types of cells: neurons and
Nervous system
12750761
cloaca. Bilaterians likely evolved from an ancestor, which was radially symmetrical. There have been suggestions that the blastopore started out as the digestive surface on a radial organism, which became elongated (and thus bilaterially symmetrical) before its sides closed over to leave a mouth at the front and an anus at the rear. This matches with the "flaps-folding-over" model of gut formation, but an alternative view is that the original blastopore migrated forwards to one end of the ancestral organism, before deepening to become a blind gut. This is consistent with living Xenacoelomorpha, which are the sister taxon to protostomes
Embryological origins of the mouth and anus
723176
species, ctenophores have a wide range of body plans. Coastal species need to be tough enough to withstand waves and swirling sediment particles, while some oceanic species are so fragile that it is very difficult to capture them intact for study. In addition oceanic species do not preserve well, and are known mainly from photographs and from observers' notes. Hence most attention has until recently concentrated on three coastal genera – "Pleurobrachia", "Beroe" and "Mnemiopsis". At least two textbooks base their descriptions of ctenophores on the cydippid "Pleurobrachia". Since the body of many species is "almost" radially symmetrical, the main
Ctenophora
5328300
were found in Cambrian lagerstätten that preserved soft-bodied animals. Invertebrates are grouped into different phyla. Informally phyla can be thought of as a way of grouping organisms according to their body plan. A body plan refers to a blueprint which describes the shape or morphology of an organism, such as its symmetry, segmentation and the disposition of its appendages. The idea of body plans originated with vertebrates, which were grouped into one phylum. But the vertebrate body plan is only one of many, and invertebrates consist of many phyla or body plans. The history of the discovery of body plans
Marine life
1837079
Ranunculaceae Ranunculaceae (buttercup or crowfoot family; Latin "little frog", from "frog") is a family of over 2,000 known species of flowering plants in 43 genera, distributed worldwide. The largest genera are "Ranunculus" (600 species), "Delphinium" (365), "Thalictrum" (330), "Clematis" (325), and "Aconitum" (300). Ranunculaceae are mostly herbaceous annuals or perennials, but some woody climbers (such as "Clematis") or shrubs (e.g. "Xanthorhiza"). Most members of the family have bisexual flowers which can be showy or inconspicuous. Flowers may be solitary, but are frequently found aggregated in cymes, panicles, or spikes. The flowers are usually radially symmetrical but are strongly bilaterally symmetrical
Ranunculaceae
534254
divisions make a spiral pattern) such as sipunculans, echiurans and many annelids. Nemerteans' affinities with Annelida (including Echiura, Pogonophora, Vestimentifera and perhaps Sipuncula) and Mollusca make the ribbon-worms members of Lophotrochozoa, which include about half of the extant animal phyla. Lophotrochozoa groups: those animals that feed using a lophophore (Brachiopoda, Bryozoa, Phoronida, Entoprocta); phyla in which most members' embryos develop into trochophore larvae (for example Annelida and Mollusca); and some other phyla (such as Platyhelminthes, Sipuncula, Gastrotricha, Gnathostomulida, Micrognathozoa, Nemertea, Phoronida, Platyhelminthes and Rotifera). These groupings are based on molecular phylogeny, which compares sections of organisms DNA and RNA. While
Nemertea
12365387
can be tentatively considered diploblastic, in other words made of two main tissue layers. Later shellies are more convincingly triploblastic, as all "higher" animals are. Subsequently, the Helcionellids are the first shelly fossils that can be placed in the stem group to a phylum (mollusca). As one looks at more recent SSFs, the arguments for stem group placements become stronger, and by the Atdabanian, some SSFs can be assigned to the crown group of a modern phylum, echinoderms. This gives the impression that the first SSF animals, from the late Ediacaran, were basal members of later clades, with the phyla
Small shelly fauna
18119404
Annelids are members of the protostomes, one of the two major superphyla of bilaterian animals – the other is the deuterostomes, which includes vertebrates. Within the protostomes, annelids used to be grouped with arthropods under the super-group Articulata ("jointed animals"), as segmentation is obvious in most members of both phyla. However, the genes that drive segmentation in arthropods do not appear to do the same in annelids. Arthropods and annelids both have close relatives that are unsegmented. It is at least as easy to assume that they evolved segmented bodies independently as it is to assume that the ancestral protostome
Annelid
12425060
lengths of the branches are not proportional to evolutionary distances. The major phyla (sometimes called divisions) of fungi have been classified mainly on the basis of characteristics of their sexual reproductive structures. Currently, seven phyla are proposed: Microsporidia, Chytridiomycota, Blastocladiomycota, Neocallimastigomycota, Glomeromycota, Ascomycota, and Basidiomycota. Phylogenetic analysis has demonstrated that the Microsporidia, unicellular parasites of animals and protists, are fairly recent and highly derived endobiotic fungi (living within the tissue of another species). One 2006 study concludes that the Microsporidia are a sister group to the true fungi; that is, they are each other's closest evolutionary relative. Hibbett and colleagues
Fungus
12590260
The suborders Spirurina and Tylenchina and the infraorders Rhabditomorpha, Panagrolaimomorpha, and Tylenchomorpha are paraphytic. The monophyly of the Ascaridomorph is uncertain. Nematodes are small, slender worms: typically about 5 to 100 µm thick, and 0.1 to 2.5 mm long. The smallest nematodes are microscopic, while free-living species can reach as much as , and some parasitic species are larger still, reaching over in length. The body is often ornamented with ridges, rings, bristles, or other distinctive structures. The head of a nematode is relatively distinct. Whereas the rest of the body is bilaterally symmetrical, the head is radially symmetrical, with
Nematode
722572
but are bilaterally symmetrical as larvae. Except for a few phyla (i.e. flatworms and gnathostomulids), bilaterians have complete digestive tracts with a separate mouth and anus. Some bilaterians lack body cavities (acoelomates, i.e. Platyhelminthes, Gastrotricha and Gnathostomulida), while others display primary body cavities (deriving from the blastocoel, as pseudocoeloms) or secondary cavities (that appear "de novo", for example the coelom). Some of the earliest bilaterians were wormlike, and a bilaterian body can be conceptualized as a cylinder with a gut running between two openings, the mouth and the anus. Around the gut it has an internal body cavity, a coelom
Bilateria
6218362
Tribrachidium Tribrachidium heraldicum is a tri-radially symmetrical fossil animal that lived in the late Ediacaran (Vendian) seas. In life, it was hemispherical in form. "T. heraldicum" is the best known member of the extinct group Trilobozoa. The generic name "Tribrachidium" is derived from combination of the Greek "τρία" (tria, "three") + Latin "brachium" ("arm") + diminutive suffix -"idium". The specific name "T. heraldicum" references the similarity of the pattern of this fossil with the well-known heraldic triskelion design, such as the coat of arms of the Isle of Man. "Tribrachidium" fossils were first discovered in the Ediacara Member of the
Tribrachidium
1462915
three or six petals, although there are many exceptions to this rule. The petal whorl or corolla may be either radially or bilaterally symmetrical (see Symmetry in biology and Floral symmetry). If all of the petals are essentially identical in size and shape, the flower is said to be regular or actinomorphic (meaning "ray-formed"). Many flowers are symmetrical in only one plane (i.e., symmetry is bilateral) and are termed irregular or zygomorphic (meaning "yoke-" or "pair-formed"). In "irregular" flowers, other floral parts may be modified from the "regular" form, but the petals show the greatest deviation from radial symmetry. Examples
Petal
678230
Gould laid to rest Haeckel's interpretation of evolutionary embryology, while Jacob set out an alternative theory. This led to a second synthesis, at last including embryology as well as molecular genetics, phylogeny, and evolutionary biology to form evo-devo. In 1978, Edward B. Lewis discovered homeotic genes that regulate embryonic development in "Drosophila" fruit flies, which like all insects are arthropods, one of the major phyla of invertebrate animals. Bill McGinnis quickly discovered homeotic gene sequences, homeoboxes, in animals in other phyla, in vertebrates such as frogs, birds, and mammals; they were later also found in fungi such as yeasts, and
Evolutionary developmental biology
16051598
Rhipsalideae The Rhipsalideae are a small tribe of cacti, comprising four genera (and around 60 species). They grow on trees (epiphytes) or on rocks (lithophytes), where they either hang down or form creeping or upright shrubs. Their flowers open in the day and remain open at night; they may be either radially symmetrical (regular) or bilaterally symmetrical (zygomorphic). The fruits are berry-like, fleshy with smallish seeds. They are found mainly in the east of South America, with a centre of diversity in Bolivia, but some species occur in Central America and North America; one species, "Rhipsalis baccifera", also occurs in
Rhipsalideae
15502119
proposed by Cavalier-Smith are generally disregarded by the molecular phylogeny community ("e.g".) ("vide supra"). For the "Archaea" the suffix "-archaeota" is used. For bacterial phyla it was proposed that the suffix "-bacteria" be used for phyla. Consequently for main phyla the name of the phyla is the same as the first described class: Whereas for others where the -ia suffix for class is used regardless of grammar they differ: An exception is the phylum "Deinococcus–Thermus", which bears a hyphenated pair of genera—only non-accented Latin letters are accepted for valid names, but phyla are not officially recognised. More recently it has
Bacterial taxonomy
677542
were later separated into two genera by Charles L’Héritier in 1789. Other former members of the genus are now classified in "Erodium", including the plants known as filarees in North America. The term "hardy geranium" is often applied to horticultural "Geranium"s to distinguish them from the "Pelargonium"s, which are not winter-hardy in temperate horticulture. However, not all "Geranium" species are winter-hardy (see below). The shape of the flowers offers one way of distinguishing between the two genera "Geranium" and "Pelargonium". "Geranium" flowers have five very similar petals, and are thus radially symmetrical (actinomorphic), whereas "Pelargonium" (and also "Erodium") flowers have
Geranium
12476990
organisms that were already mineralised are usually preserved, such as the shells of molluscs. Since most animal species are soft-bodied, they decay before they can become fossilised. As a result, although 30-plus phyla of living animals are known, two-thirds have never been found as fossils. The Cambrian fossil record includes an unusually high number of lagerstätten, which preserve soft tissues. These allow paleontologists to examine the internal anatomy of animals, which in other sediments are only represented by shells, spines, claws, etc. – if they are preserved at all. The most significant Cambrian lagerstätten are the early Cambrian Maotianshan shale
Cambrian explosion
19326710
had been subdivided into twelve phyla: The protozoa were originally classified as members of the animal kingdom. Now they are classified as multiple separate groups. Zoology is the study of animals while botany is the study of plants. While zoologists divided the animal kingdom into phyla, botanists carved the plant kingdom into "divisions". By 1940, five divisions were recognized: Fungi and bacteria were included within the plant division thallophyta. Today, bacteria are no longer classified as plants and fungi are known to be more closely related to animals than to plants. By mid-nineteenth century, microscopic organisms were generally classified into
Cavalier-Smith's system of classification
16051325
Individual segments are about long by wide. Special structures characteristic of cacti, called "areoles", occur in the notches at the side of a segment and at the end. The areoles, which bristles up to long, are where the flower buds appear. The flowers hang downwards and are radially symmetrical (regular). They are about long by across. The tepals, which are of various shades of pink, are arranged in two groups, giving the appearance of a "flower within a flower". The inner tepals are longer and fused together at the base to form a floral tube about long; nectar is produced
Schlumbergera russelliana
12333539
cm. long. Flowers are radially symmetrical, about 1 centimeter in diameter, with white and spatulate petals. "Flabellaria paniculata" is widely distributed in equatorial Africa in thickets, woodlands, and forests, especially along rivers, at an altitude of . Flabellaria Flabellaria is a genus in the Malpighiaceae, a family of about 75 genera of flowering plants in the order Malpighiales. "Flabellaria" includes one variable species, Flabellaria paniculata. The genus name "Flabellaria" comes from the Latin word "flabellum" meaning small fan, referring to the shape of the samara. This genus is known in the fossil record from the Cretaceous to the Eocene (age
Flabellaria
13972007
stipules. Cystoliths are always present and some members of this family possess laticifers. Cannabaceae are often dioecious (distinct male and female plants). The flowers are actinomorphic (radially symmetrical) and not showy, as these plants are pollinated by the wind. As an adaptation to this kind of pollination, the calyx is short and there is no corolla. Flowers are grouped to form cymes. In the dioecious plants the masculine inflorescences are long and look like panicles, while the feminine are shorter and bear fewer flowers. The pistil is made of two connate carpels, the usually superior ovary is unilocular; there is
Cannabaceae
4676661
sister group of the Rouphozoa (the Gastrotricha and Platyhelminthes). The Lophotrochozoa and Rouphozoa are then named the Platytrochozoa. This makes the Platyzoa a paraphyletic group. Platyzoa The paraphyletic "Platyzoa" are a group of protostome unsegmented animals proposed by Thomas Cavalier-Smith in 1998. Cavalier-Smith included in Platyzoa the phylum Platyhelminthes (or flatworms), and a new phylum, the Acanthognatha, into which he gathered several previously described phyla of microscopic animals. More recently it has been described as paraphyletic, containing the Rouphozoa and the Gnathifera. One scheme placed the following phyla in Platyzoa: None of the Platyzoa groups have a respiration or circulation
Platyzoa
18089608
towards it, from planes perpendicular to it. When we consider 2-D flows on the perpendicular plane, it appears as a point sink. By symmetry, we assume the fluid flows radially inwards towards the source. The strength of a sink is given by the volume flow rate formula_15 of the fluid it absorbs. A radially symmetrical flow field directed outwards from a common point is called a source flow. The central common point is the line source described above. Fluid is supplied at a constant rate formula_15 from the source. As the fluid flows outward, the area of flow increases. As
Two-dimensional flow
6037923
weakly succulent, growing upright or pendent; spines are usually missing. The flowers are borne terminally; they are actinomorphic (radially symmetrical) and are always coloured. The fruit is a berry. "Hatiora" species have been divided into two groups or subgenera which are well differentiated by their morphology. Members of subgenus "Hatiora" have cylindrical stems. They grow more or less upright and become woody at the base of the stems when plants become older. The flowers are small, with a diameter of about , and yellow, orange or pink. Members of subgenus "Rhipsalidopsis" have flattened, weakly succulent, segmented stems. The flowers of
Hatiora
2745515
either alternate and spiraling, or opposite. Stipules are present. These leaves are modified into spines in many genera, in some (e.g. "Paliurus spina-christi" and "Colletia cruciata") spectacularly so. "Colletia" stands out by having two axillary buds instead of one, one developing into a thorn, the other one into a shoot. The flowers are radially symmetrical. There are 5 (sometimes 4) separate sepals and 5 (sometimes 4 or none) separate petals. The petals may be white, yellowish, greenish, pink or blue, and are small and inconspicuous in most genera, though in some (e.g. "Ceanothus") the dense clusters of flowers are conspicuous.
Rhamnaceae
12366126
are not as abundant or varied as in the two other tropical regions. However, Euphorbiaceae also has many species in nontropical areas such as the Mediterranean Basin, the Middle East, South Africa, and the southern United States. The leaves are alternate, seldom opposite, with stipules. They are mainly simple, but where compound, are always palmate, never pinnate. Stipules may be reduced to hairs, glands, or spines, or in succulent species are sometimes absent. The plants can be monoecious or dioecious. The radially symmetrical flowers are unisexual, with the male and female flowers usually on the same plant. As can be
Euphorbiaceae
99283
are known to be pollinated by bats—an unusually high proportion, exceeded among eudicots by only two other families, both with very few genera. Columnar cacti growing in semidesert areas are among those most likely to be bat-pollinated; this may be because bats are able to travel considerable distances, so are effective pollinators of plants growing widely separated from one another. The pollination syndrome associated with bats includes a tendency for flowers to open in the evening and at night, when bats are active. Other features include a relatively dull color, often white or green; a radially symmetrical shape, often tubular;
Cactus
7372869
or "embranchements": Grouping animals with these body plans resulted in four branches: vertebrates, molluscs, articulata (including insects and annelids) and zoophytes or radiata. Ernst Haeckel, in his 1866 "Generelle Morphologie der Organismen", asserted that all living things were monophyletic (had a single evolutionary origin), being divided into plants, protista, and animals. His protista were divided into moneres, protoplasts, flagellates, diatoms, myxomycetes, myxocystodes, rhizopods, and sponges. His animals were divided into groups with distinct body plans: he named these phyla. Haeckel's animal phyla were coelenterates, echinoderms, and (following Cuvier) articulates, molluscs, and vertebrates. Stephen J. Gould explored the idea that the
Body plan
5324071
cm long. Its sweetly scented flowers are radially symmetrical and pink, or sometimes white. Each of the five flat petals have two small scales in the throat of the corolla. They are about wide. They are arranged in dense, terminal clusters on the main stem and its branches. The long tubular calyx has five pointed red teeth. The individual flowers open in the evening, and stay open for about three days. They produce a stronger scent at night and supplement nectar production during the night. The flowers are protandrous: on the second night of blooming, the pollen is released, and
Saponaria officinalis