Nostoc is a genus of cyanobacteria found in various environments that forms colonies composed of filaments of moniliform cells in a gelatinous sheath. The name Nostoc was coined by Paracelsus. Nostoc can be found in soil, on moist rocks, at the bottom of lakes and springs, in marine habitats, it may grow symbiotically within the tissues of plants, such as the evolutionarily ancient angiosperm Gunnera and the hornworts, providing nitrogen to its host through the action of terminally differentiated cells known as heterocysts. These bacteria contain photosynthetic pigments in their cytoplasm to perform photosynthesis. Nostoc is a member of the family Nostocaceae of the order Nostocales. Species include: When it is on the ground, a Nostoc colony is ordinarily not seen, but after a rain, it swells up into a conspicuous, jellylike mass, once thought to have fallen from the sky, hence the popular names, star jelly, troll’s butter, witch's butter, witch’s jelly. Containing protein and vitamin C, Nostoc species are cultivated and consumed as a foodstuff in Asia.
The species N. flagelliforme and N. commune are consumed in China, where it was used to survive famines. The preferred variety in Central Asia is N. ellipsosporum. "Nikon MicroscopyU: Confocal Image Gallery - Nostoc". Web.archive.org. 9 March 2005. Retrieved 15 January 2019. Office, NOAA Sea Grant Extension. "GLERL/Sea Grant: Great Lakes Water Life Photo Gallery - Blue-green Algae - Cyanophtya". Www.glerl.noaa.gov. Retrieved 2019-02-20. Davidson, Alan. Oxford Companion to Food, "Nostoc". ISBN 0-19-211579-0 "Aktuelle News, Schlagzeilen und Berichte aus aller Welt - Arcor.de". Www.arcor.de. Retrieved 15 January 2019. Nostoc spec. in lichens Guiry, M. D.. M.. "Nostoc". AlgaeBase. World-wide electronic publication, National University of Ireland, Galway
Symbiosis is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasitic. The organisms, each termed a symbiont, may be of different species. In 1879, Heinrich Anton de Bary defined it as "the living together of unlike organisms"; the term was subject to a century-long debate about whether it should denote mutualism, as in lichens. Symbiosis can be obligatory, which means that one or both of the symbionts depend on each other for survival, or facultative when they can live independently. Symbiosis is classified by physical attachment; when one organism lives on the surface of another, such as head lice on humans, it is called ectosymbiosis. The definition of symbiosis was a matter of debate for 130 years. In 1877, Albert Bernhard Frank used the term symbiosis to describe the mutualistic relationship in lichens. In 1879, the German mycologist Heinrich Anton de Bary defined it as "the living together of unlike organisms".
The definition has varied among scientists, with some advocating that it should only refer to persistent mutualisms, while others thought it should apply to all persistent biological interactions, in other words mutualisms, commensalism, or parasitism, but excluding brief interactions such as predation. Current biology and ecology textbooks use the latter "de Bary" definition, or an broader one where symbiosis means all interspecific interactions. In 1949, Edward Haskell proposed an integrative approach, proposing a classification of "co-actions" adopted by biologists as "interactions". Biological interactions can involve individuals of the same species or individuals of different species; these can be further classified by either the mechanism of the interaction or the strength and direction of their effects. Relationships can be obligate, meaning that one or both of the symbionts depend on each other for survival. For example, in lichens, which consist of fungal and photosynthetic symbionts, the fungal partners cannot live on their own.
The algal or cyanobacterial symbionts in lichens, such as Trentepohlia, can live independently, their symbiosis is, facultative. Endosymbiosis is any symbiotic relationship in which one symbiont lives within the tissues of the other, either within the cells or extracellularly. Examples include diverse microbiomes, nitrogen-fixing bacteria that live in root nodules on legume roots. Ectosymbiosis is any symbiotic relationship in which the symbiont lives on the body surface of the host, including the inner surface of the digestive tract or the ducts of exocrine glands. Examples of this include ectoparasites such as lice. Competition can be defined as an interaction between organisms or species, in which the fitness of one is lowered by the presence of another. Limited supply of at least one resource used by both facilitates this type of interaction, although the competition may exist over other'amenities', such as females for reproduction. Mutualism or interspecies reciprocal altruism is a long-term relationship between individuals of different species where both individuals benefit.
Mutualistic relationships may be either obligate for both species, obligate for one but facultative for the other, or facultative for both. A large percentage of herbivores have mutualistic gut flora to help them digest plant matter, more difficult to digest than animal prey; this gut flora is made up of cellulose-digesting protozoans or bacteria living in the herbivores' intestines. Coral reefs are the result of mutualisms between coral organisms and various types of algae which live inside them. Most land plants and land ecosystems rely on mutualisms between the plants, which fix carbon from the air, mycorrhyzal fungi, which help in extracting water and minerals from the ground. An example of mutualism is the relationship between the ocellaris clownfish that dwell among the tentacles of Ritteri sea anemones; the territorial fish protects the anemone from anemone-eating fish, in turn the stinging tentacles of the anemone protect the clownfish from its predators. A special mucus on the clownfish protects it from the stinging tentacles.
A further example is a fish which sometimes lives together with a shrimp. The shrimp cleans up a burrow in the sand in which both the shrimp and the goby fish live; the shrimp is blind, leaving it vulnerable to predators when outside its burrow. In case of danger, the goby touches the shrimp with its tail to warn it; when that happens both the shrimp and goby retreat into the burrow. Different species of gobies clean up ectoparasites in other fish another kind of mutualism. A non-obligate symbiosis is seen in encru
In biology, a colony is composed of two or more conspecific individuals living in close association with, or connected to, one another. This association is for mutual benefit such as stronger defense or the ability to attack bigger prey, it is a cluster of identical cells on the surface of a solid medium derived from a single parent cell, as in bacterial colony. In contrast, a solitary organism is one in which all individuals live independently and have all of the functions needed to survive and reproduce. Colonies, in the context of development, may be composed of two or more unitary organisms or be modular organisms. Unitary organisms have determinate development from zygote to adult form and individuals or groups of individuals are visually distinct. Modular organisms have indeterminate growth forms through repeated iteration of genetically identical modules, it can be difficult to distinguish between the colony as a whole and the modules within. In the latter case, modules may have specific functions within the colony.
Some organisms are independent and form facultative colonies in reply to environmental conditions while others must live in a colony to survive. For example, some carpenter bees will form colonies when a dominant hierarchy is formed between two or more nest foundresses, while corals are animals that are physically connected by living tissue that contains a shared gastrovascular cavity. Unicellular and multicellular unitary organisms may aggregate to form colonies. For example, Protists such as slime molds are many unicellular organisms that aggregate to form colonies when food resources are hard to come by, as together they are more reactive to chemical cues released by preferred prey. Eusocial insects like ants and honey bees are multicellular animals that live in colonies with a organized social structure. Colonies of some social insects may be deemed superorganisms. Animals, such as humans and rodents, form breeding or nesting colonies for more successful mating and to better protect offspring.
The Bracken Cave is the summer home to a colony of around 20 million Mexican free-tailed bats making it the largest known concentration of mammals. Modular organisms are those in which a genet asexually reproduces to form genetically identical clones called ramets. A clonal colony is when the ramets of a genet are physically connected. Ramets may have all of the functions needed to survive on their own or be interdependent on other ramets. For example, some sea anemones go through the process of pedal laceration in which a genetically identical individual is asexually produced from tissue broken off from the anemone's pedal disc. In plants, clonal colonies are created through the propagation of genetically identical trees by stolons or rhizomes. Colonial organisms are clonal colonies composed of many physically connected, interdependent individuals; the subunits of colonial organisms can be unicellular, as in the alga Volvox, or multicellular, as in the phylum Bryozoa. The former type may have been the first step toward multicellular organisms.
Individuals within a multicellular colonial organism may be called modules, or zooids. Structural and functional variation, when present, designates ramet responsibilities such as feeding and defense. To that end, being physically connected allows the colonial organism to distribute nutrients and energy obtained by feeding zooids throughout the colony. An example of colonial organisms, well known are hydrozoans, like Portuguese man o' wars. A microbial colony is defined as a visible cluster of microorganisms growing on the surface of or within a solid medium cultured from a single cell; because the colony is clonal, with all organisms in it descending from a single ancestor, they are genetically identical, except for any mutations. Obtaining such genetically identical organisms can be useful. A biofilm is a colony of microorganisms comprising several species, with properties and capabilities greater than the aggregate of capabilities of the individual organisms. Individuals in social colonies and modular organisms receive benefit to such a lifestyle.
For example, it may be easier to seek out food, defend a nesting site, or increase competitive ability against other species. Modular organisms' ability to reproduce asexually in addition to sexually allows them unique benefits that social colonies do not have; the energy required for sexual reproduction varies based on the frequency and length of reproductive activity and size of offspring, parental care. While solitary individuals bear all of those energy costs, individuals in some social colonies share a portion of those costs. Modular organisms save energy by using asexual reproduction during their life. Energy reserved in this way allows them to put more energy towards colony growth, regenerating lost modules, or response to environmental conditions
Mucus is a polymer. It is a slippery aqueous secretion produced by, covering, mucous membranes, it is produced from cells found in mucous glands, although it may originate from mixed glands, which contain both serous and mucous cells. It is a viscous colloid containing inorganic salts, antiseptic enzymes and glycoproteins such as lactoferrin and mucins, which are produced by goblet cells in the mucous membranes and submucosal glands. Mucus serves to protect epithelial cells in the respiratory, urogenital and auditory systems. Most of the mucus produced is in the gastrointestinal tract. Bony fish, snails and some other invertebrates produce external mucus. In addition to serving a protective function against infectious agents, such mucus provides protection against toxins produced by predators, can facilitate movement and may play a role in communication. In the human respiratory system, mucus known as airway surface liquid, aids in the protection of the lungs by trapping foreign particles that enter them, in particular, through the nose, during normal breathing.
Further distinction exists between the superficial and cell-lining layers of ASL, which are known as mucus layer and pericilliary liquid layer, respectively. "Phlegm" is a specialized term for mucus, restricted to the respiratory tract, whereas the term "nasal mucus" describes secretions of the nasal passages. Nasal mucus is produced by the nasal mucosa. Small particles such as dust, particulate pollutants, allergens, as well as infectious agents and bacteria are caught in the viscous nasal or airway mucus and prevented from entering the system; this event along with the continual movement of the respiratory mucus layer toward the oropharynx, helps prevent foreign objects from entering the lungs during breathing. This explains why coughing occurs in those who smoke cigarettes; the body's natural reaction is to increase mucus production. In addition, mucus aids in moisturizing the inhaled air and prevents tissues such as the nasal and airway epithelia from drying out. Nasal and airway mucus is produced continuously, with most of it swallowed subconsciously when it is dried.
Increased mucus production in the respiratory tract is a symptom of many common illnesses, such as the common cold and influenza. Hypersecretion of mucus can occur in inflammatory respiratory diseases such as respiratory allergies and chronic bronchitis; the presence of mucus in the nose and throat is normal, but increased quantities can impede comfortable breathing and must be cleared by blowing the nose or expectorating phlegm from the throat. In general, nasal mucus is thin, serving to filter air during inhalation. During times of infection, mucus can change color to yellow or green either as a result of trapped bacteria or due to the body's reaction to viral infection; the green color of mucus comes from the heme group in the iron-containing enzyme myeloperoxidase secreted by white blood cells as a cytotoxic defense during a respiratory burst. In the case of bacterial infection, the bacterium becomes trapped in already-clogged sinuses, breeding in the moist, nutrient-rich environment. Sinusitis is an uncomfortable condition.
A bacterial infection in sinusitis will cause discolored mucus and would respond to antibiotic treatment. All sinusitis infections are viral and antibiotics are ineffective and not recommended for treating typical cases. In the case of a viral infection such as cold or flu, the first stage and the last stage of the infection cause the production of a clear, thin mucus in the nose or back of the throat; as the body begins to react to the virus, mucus may turn yellow or green. Viral infections cannot be treated with antibiotics, are a major avenue for their misuse. Treatment is symptom-based. Increased mucus production in the upper respiratory tract is a symptom of many common ailments, such as the common cold. Nasal mucus may be removed by using nasal irrigation. Excess nasal mucus, as with a cold or allergies, due to vascular engorgement associated with vasodilation and increased capillary permeability caused by histamines, may be treated cautiously with decongestant medications. Thickening of mucus as a "rebound" effect following overuse of decongestants may produce nasal or sinus drainage problems and circumstances that promote infection.
During cold, dry seasons, the mucus lining nasal passages tends to dry out, meaning that mucous membranes must work harder, producing more mucus to keep the cavity lined. As a result, the nasal cavity can fill up with mucus. At the same time, when air is exhaled, water vapor in breath condenses as the warm air meets the colder outside temperature near the nostrils; this causes an excess amount of water to build up inside nasal cavities. In these cases, the excess fluid spills out externally through the nostrils. Excess mucus production in the bronchi and bronchioles, as may occur in asthma, bronchitis or influenza, results from chronic airway inflammation, hence may be treated with anti-inflammatory medications. Impaired mucociliary clearance due to conditions such as primary ciliary dyskinesia may result in its accumulation in the bronchi; the dysregulation of
Cycads are seed plants with a long fossil history that were more abundant and more diverse than they are today. They have a stout and woody trunk with a crown of large and stiff, evergreen leaves, they have pinnate leaves. The individual plants are all female. Cycads vary in size from having trunks only a few centimeters to several meters tall, they grow slowly and live long, with some specimens known to be as much as 1,000 years old. Because of their superficial resemblance, they are sometimes mistaken for palms or ferns, but they are not related to either group. Cycads are gymnosperms, meaning their unfertilized seeds are open to the air to be directly fertilized by pollination, as contrasted with angiosperms, which have enclosed seeds with more complex fertilization arrangements. Cycads have specialized pollinators a specific species of beetle, they have been reported to fix nitrogen in association with various cyanobacteria living in the roots. These photosynthetic bacteria produce a neurotoxin called BMAA, found in the seeds of cycads.
This neurotoxin may enter a human food chain as the cycad seeds may be eaten directly as a source of flour by humans or by wild or feral animals such as bats, humans may eat these animals. It is hypothesized. Cycads have a cylindrical trunk which does not branch. Leaves grow directly from the trunk, fall when older, leaving a crown of leaves at the top; the leaves grow with new foliage emerging from the top and center of the crown. The trunk may be buried, so the leaves appear to be emerging from the ground, so the plant appears to be a basal rosette; the leaves are large in proportion to the trunk size, sometimes larger than the trunk. The leaves are pinnate, with a central leaf stalk from which parallel "ribs" emerge from each side of the stalk, perpendicular to it; the leaves are either compound, or have edges so cut so as to appear compound. Some species have leaves that are bipinnate, which means the leaflets each have their own subleaflets, growing in the same form on the leaflet as the leaflets grow on the stalk of the leaf.
Due to superficial similarities in foliage and plant structure between cycads and palms they are confused with each other. In reality, they belong to different phyla, are not related at all; the similar structure may be evidence of convergent evolution. Despite this, there are still a number of differences between them. For one, both male and female cycads bear a cone-like reproductive structure called a strobilus, while palms are angiosperms and so flower and bear fruit; the mature foliage looks similar between both groups, but the young emerging leaves of a cycad resemble a fiddlehead fern before they unfold and take their place in the rosette, while the leaves of palms are never coiled up and instead are just small versions of the mature frond. Another difference is in the stem. Both plants leave scars on the stem below the rosette where there used to be leaves, but the scars of a cycad are helically arranged and small, while the scars of palms are a circle that wraps around the whole stem.
The stems of cycads are in general rougher and shorter than those of palms. The three extant families of cycads all belong to the order Cycadales, are Cycadaceae and Zamiaceae; these cycads have changed little since the Jurassic, compared to some major evolutionary changes in other plant divisions. Five additional families belonging to the Medullosales became extinct by the end of the Paleozoic Era. Cycads have been traditionally put as related to the extinct Bennettitales, however recent findings show marked differences In reproductive biology and general anatomy putting doubt on the traditional view; as of yet the evidence points to a pteridospermalean origin of cycads and to a close relation to the Ginkgoales, as shown in the following phylogeny: Classification of the Cycadophyta to the rank of family. Class Cycadopsida Order Medullosales † Family Alethopteridaceae Family Cyclopteridaceae Family Neurodontopteridaceae Family ParispermaceaeOrder Cycadales Suborder Cycadineae Family Cycadaceae Suborder Zamiineae Family Stangeriaceae Family Zamiaceae The probable former range of cycads can be inferred from their global distribution.
For example, the family Stangeriaceae only contains three extant species in Australia. Diverse fossils of this family have been dated to 135 mya, indicating that diversity may have been much greater before the Jurassic and late Triassic mass extinction events. However, the cycad fossil record is poor and little can be deduced about the effects of each mass extinction event on their diversity. Instead, correlations can be made between the number of extant angiosperms, it is that cycad diversity was affected more by the great angiosperm radiation in the mid-Cretaceous than by extinctions. Slow cambial growth was first used to define cycads, because of this characteristic the group could not compete with the growing short-lived angiosperms, which now number over 250,000 species, compared to the 1080 remaining gymnosperms, it is surprising that the cycads are still extant, having been faced with extreme competition and five major extinctions. The ability of cycads to survive in dry environments, where plant diversity is lower, may explain their long persistence and longevity.
The cycad fossil record dates to the e
Carl Adolph Agardh
Carl Adolph Agardh was a Swedish botanist specializing in algae, appointed bishop of Karlstad. In 1807 he was appointed teacher of mathematics at Lund University, in 1812 appointed professor of botany and natural sciences, was elected a member of the Royal Swedish Academy of Sciences in 1817, of the Swedish Academy in 1831, he was ordained a clergyman in 1816, received two parishes as prebend, was a representative in the clerical chamber of the Swedish Parliament on several occasions from 1817. He was rector magnificus of Lund University 1819-1820 and was appointed bishop of Karlstad in 1835, where he remained until his death, he was the father of Jacob Georg Agardh a botanist. He devoted considerable attention to political economy and as "a leading liberal", he "succeeded in improving and raising the standards of education in Sweden", he wrote on theological and other subjects, but his reputation chiefly rests on his botanical works Systema algarum, Species algarum rite cognitae and Classes plantarum on biological classification, Icones Algarum.
The greatest part of his Manual of Botany has been translated into German. Agardh, Carl Adolph. Classes Plantarum. Lund: Literis Berlingianis. Retrieved 21 December 2015. Algarum decas prima /auctore Carolo Ad. Agardh Dispositio algarum Sueciae /cuctore Carolo Adolfo Agardh Caroli A. Agardh Synopsis algarum Scandinaviae: adjecta dispositione universali algarum Aphorismi botanici. Classes plantarum Adnotationes botanicae Short biography in French https://web.archive.org/web/20070406080639/http://www.biomus.lu.se/indexBe.html Lund University, Botanical Museum https://web.archive.org/web/20060621021532/http://www.biomus.lu.se/indexBsamae.html Lund Museum - Collections: algae Note: This is a selected list of the more influential systems. There are many other systems, for instance a review of earlier systems, published by Lindley in his 1853 edition, Dahlgren. Examples include the works of Scopoli and Grisebach
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence and other forms of luminescence, in which a material emits light. Most materials selectively absorb certain wavelengths of light. Materials that humans have chosen and developed for use as pigments have special properties that make them useful for coloring other materials. A pigment must have a high tinting strength relative to the materials colors, it must be stable in solid form at ambient temperatures. For industrial applications, as well as in the arts and stability are desirable properties. Pigments that are not permanent are called fugitive. Fugitive pigments fade over time, or with exposure to light, while some blacken. Pigments are used for coloring paint, plastic, cosmetics and other materials. Most pigments used in manufacturing and the visual arts are dry colorants ground into a fine powder. For use in paint, this powder is added to a binder, a neutral or colorless material that suspends the pigment and gives the paint its adhesion.
A distinction is made between a pigment, insoluble in its vehicle, a dye, which either is itself a liquid or is soluble in its vehicle. A colorant can act as either a dye depending on the vehicle involved. In some cases, a pigment can be manufactured from a dye by precipitating a soluble dye with a metallic salt; the resulting pigment is called a lake pigment. The term biological pigment is used for all colored substances independent of their solubility. In 2006, around 7.4 million tons of inorganic and special pigments were marketed worldwide. Asia has the highest rate on a quantity basis followed by North America; the global demand on pigments was US$20.5 billion in 2009. Pigments appear colored because they selectively reflect and absorb certain wavelengths of visible light. White light is a equal mixture of the entire spectrum of visible light with a wavelength in a range from about 375 or 400 nanometers to about 760 or 780 nm; when this light encounters a pigment, parts of the spectrum are absorbed by the pigment.
Organic pigments such as diazo or phthalocyanine compounds feature conjugated systems of double bonds. Some inorganic pigments, such as vermilion or cadmium yellow, absorb light by transferring an electron from the negative ion to the positive ion; the other wavelengths or parts of the spectrum are scattered. The new reflected. Pigments, unlike fluorescent or phosphorescent substances, can only subtract wavelengths from the source light, never add new ones; the appearance of pigments is intimately connected to the color of the source light. Sunlight has a high color temperature and a uniform spectrum and is considered a standard for white light, while artificial light sources tend to have strong peaks in parts of their spectra. Viewed under different lights, pigments will appear different colors. Color spaces used to represent colors. Lab color measurements, unless otherwise noted, assume that the measurement was taken under a D65 light source, or "Daylight 6500 K", the color temperature of sunlight.
Other properties of a color, such as its saturation or lightness, may be determined by the other substances that accompany pigments. Binders and fillers added to pure pigment chemicals have their own reflection and absorption patterns, which can affect the final spectrum. For example, in pigment/binder mixtures, individual rays of light may not encounter pigment molecules and may be reflected unchanged; these stray rays of source light make. Pure pigment allows little white light to escape, producing a saturated color, while a small quantity of pigment mixed with a lot of white binder will appear unsaturated and pale due to incident white light escaping unchanged. Occurring pigments such as ochres and iron oxides have been used as colorants since prehistoric times. Archaeologists have uncovered evidence that early humans used paint for aesthetic purposes such as body decoration. Pigments and paint grinding equipment believed to be between 350,000 and 400,000 years old have been reported in a cave at Twin Rivers, near Lusaka, Zambia.
Before the Industrial Revolution, the range of color available for art and decorative uses was technologically limited. Most of the pigments in use were pigments of biological origin. Pigments from unusual sources such as botanical materials, animal waste and mollusks were harvested and traded over long distances; some colors were impossible to obtain, given the range of pigments that were available. Blue and purple came to be associated with royalty because of their rarity. Biological pigments were difficult to acquire, the details of their production were kept secret by the manufacturers. Tyrian Purple is a pigment made from the mucus of one of several species of Murex snail. Production of Tyrian Purple for use as a fabric dye began as early as 1200 BCE by the Phoenicians, was continued by the Greeks and Romans until 1453 CE, with the fall of Constantinople; the pigment was expensive and complex to produce, items colored with it became associated with power and wealth. Greek historian Theopompus, writing in the 4th century BCE, reported that "purple for dyes fetched its weight in silver at Colophon."Mineral pigments were traded over long distances.
The only w