1.
Black rat
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The black rat, also known as the ship rat, roof rat, house rat, is a common long-tailed rodent of the genus Rattus in the subfamily Murinae. The species originated in tropical Asia and spread through the Near East in Roman times before reaching Europe by the 1st century and they are serious pests to farmers as they eat a wide range of agricultural crops. The black rat was one of the species originally described by Linnaeus in his 18th century work, Systema Naturae. It is the species of the genus Rattus. A typical adult black rat is 12.75 to 18.25 cm long, not including a 15 to 22 cm tail, despite its name, the black rat exhibits several colour forms. It is usually black to brown in colour with a lighter underside. In England during the 1920s, several variations were bred and shown alongside domesticated brown rats and this included an unusual green tinted variety. The black rat also has a coat of black fur. Rattus rattus bone remains that date back to the Norman Period have been discovered in Britain, evidence also suggests that R. rattus existed in prehistoric Europe as well as the Levant during post-glacial periods. The specific origin of the rat is uncertain due to the rats disappearance. Evidence such as DNA and bone fragments suggests that the rats did not originally come from Europe. Rats are resilient vectors for many diseases because of their ability to hold so many infectious bacteria in their blood, Rats played a primary role in spreading bacteria, such as Yersinia pestis, which is responsible for the Justinianic plague and bubonic plague. A recent study indicates that other Asiatic rodents served as reservoirs, from which infections spread as far west as Europe via trade routes. The modern black rat was probably spread across Europe in the wake of the Roman conquest and arose from an ancestor that originated in southeast Asia, the Mediterranean black rats differ genetically from their southeast Asian ancestors by having 38 instead of 42 chromosomes. Therefore, it seems that speciation could have occurred when the rats colonized southwest India, because Rattus rattus is a passive traveler, they could have easily traveled to Europe during the trading between Rome and southwestern Asian countries. Evidence also suggests that, in 321–331 BC, Egyptian birds were preying on Mediterranean rats, Black rats are considered omnivores and eat a wide range of foods, including seeds, fruit, stems, leaves, fungi, and a variety of invertebrates and vertebrates. They are generalists, and thus not very specific in their preferences, which is indicated by their tendency to feed on any meal provided for cows, swine, chickens, cats. They are similar to the squirrel in their preference of fruits and nuts
2.
Natural reservoir
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A natural reservoir or nidus is the long-term host of a pathogen of an infectious disease. Hosts often do not get the disease carried by the pathogen, or it is carried as an infection and so is asymptomatic. Once discovered, natural reservoirs elucidate the life cycle of infectious diseases, providing effective prevention. Some viruses have no non-human reservoir, poliomyelitis and smallpox are prominent examples, the lack of a non-human reservoir makes these viruses good candidates for eradication efforts. The natural reservoir of some diseases remain unclear and this is the case of the Ebola virus disease. Traces of EBOV were detected in the carcasses of gorillas and chimpanzees during outbreaks in 2001 and 2003, however, the high lethality from infection in these species makes them unlikely as a natural reservoir. However, a subsequent study, in an outbreak, found 31. 8% of the dogs closest to an outbreak contained antigens that indicate a previous active viral load. Whether dogs passed the virus to humans, or both were infected by a species is unknown. Plants, arthropods, and birds have also considered as possible reservoirs, however. Of 24 plant species and 19 vertebrate species experimentally inoculated with EBOV, the absence of clinical signs in these bats is characteristic of a reservoir species. In a 2002–2003 survey of 1,030 animals including 679 bats from Gabon, as of 2005, three types of fruit bats have been identified as being in contact with EBOV. They are now suspected to represent the EBOV reservoir hosts, however, it has to be stressed that infectious ebolaviruses have not yet been isolated from any nonhuman animal. Bats drop partially eaten fruits and pulp, then terrestrial mammals such as gorillas and this chain of events forms a possible indirect means of transmission from the natural host to animal populations, which have led to research towards viral shedding in the saliva of bats. Fruit production, animal behavior, and other factors vary at different times and places that may trigger outbreaks among animal populations. Transmission between natural reservoirs and humans are rare, and outbreaks are usually traceable to an index case where an individual has handled the carcass of gorilla, chimpanzee. The virus then spreads person-to-person, especially families, hospitals
3.
Oriental rat flea
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The Oriental rat flea, also known as the tropical rat flea, is a parasite of rodents, primarily of the genus Rattus, and is a primary vector for bubonic plague and murine typhus. This occurs when the flea has fed on an infected rodent, the Oriental rat flea has no genal or pronotal combs. This characteristic can be used to differentiate the oriental rat flea from the cat flea, dog flea, the fleas body is only about one tenth of an inch long. A fleas body is constructed to make it easier to jump long distances, the fleas body consists of three regions, head, thorax, and abdomen. The head and the thorax have rows of bristles, and the abdomen consists of eight visible segments, a fleas mouth has two functions, one for squirting saliva or partly digested blood into the bite, and one for sucking up blood from the host. This process mechanically transmits pathogens that may cause diseases the flea might have, fleas smell exhaled carbon dioxide from humans and animals and jump rapidly to the source to feed on the newly found host. A flea is wingless so it can not fly, but it can jump long distances with the help of small, a fleas leg consists of four parts, the part that is closest to the body is the coxa, next are the femur, tibia, and tarsus. A flea can use its legs to jump up to 200 times its own body length, there are four stages in a fleas life. The first stage is the egg stage, microscopic white eggs fall easily from the female to the ground or from the animal she lays on. If they are laid on an animal, they fall off in the dust or in the animals bedding. If the eggs do fall immediately on the ground, then fall into crevices on the floor where they will be safe until they hatch one to ten days later. They hatch into a larva that looks similar to a worm and is about two millimeters long. It only has a body and a mouth part. At this stage, the flea does not drink blood, instead it eats dead skin cells, flea droppings, when the larva is mature it makes a silken cocoon around itself and pupates. The flea remains a pupa from one week to six months changing in a process called metamorphosis, when the flea emerges, it begins the final cycle, called the adult stage. A flea can now suck blood from host and mate with other fleas, a single female flea can mate once and lay eggs every day with up to 50 eggs per day. Experimentally, it has shown that the fleas flourish in dry climatic conditions with temperatures of 20–25 °C. They can live up to a year and can stay in the stage for up to a year if the conditions are not favourable
4.
Vector (epidemiology)
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Arthropods form a major group of pathogen vectors with mosquitoes, flies, sand flies, lice, fleas, ticks and mites transmitting a huge number of pathogens. Many such vectors are haematophagous, which feed on blood at some or all stages of their lives, when the insects blood feed, the pathogen enters the blood stream of the host. This can happen in different ways, the Anopheles mosquito, a vector for malaria, filariasis, and various arthropod-borne-viruses, inserts its delicate mouthpart under the skin and feeds on its hosts blood. The parasites the mosquito carries are usually located in its salivary glands, therefore, the parasites are transmitted directly into the hosts blood stream. Leishmania parasites then infect the host through the saliva of the sand fly, onchocerca force their own way out of the insects head into the pool of blood. Triatomine bugs are responsible for the transmission of a trypanosome, Trypanosoma cruzi, the Triatomine bugs defecate during feeding and the excrement contains the parasites which are accidentally smeared into the open wound by the host responding to pain and irritation from the bite. Some plants and fungi act as vectors for various pathogens, for example, the big-vein disease of lettuce was long thought to be caused by a member of the fungal division Chytridiomycota, namely Olpidium brassicae. Eventually however, the disease was shown to be viral, later it transpired that the virus was transmitted by the zoospores of the fungus and also survived in the resting spores. Since then, many fungi in the Chytridiomycota have been shown to vector plant viruses. Many plant pests that seriously damage important crops depend on plants, often weeds, to harbour or vector them. In the case of Puccinia graminis for example, Berberis and related genera act as hosts in a cycle of infection of grain. More directly, when they twine from one plant to another, parasitic plants such as Cuscuta, in April 2014, WHO launched a campaign called “Small bite, big threat” to educate people about vector-borne illnesses. WHO issued reports indicating that vector-borne illnesses affect poor people, especially people living in areas that do not have levels of sanitation, drinking water. Several articles, recent to early 2014, warn that human activities are spreading vector-borne zoonotic diseases, examples of vector-borne zoonotic diseases include, Dengue fever Lyme disease Plague West Nile virus Many factors affect the incidence of vector-borne diseases. These factors include animals hosting the disease, vectors, and people, the Health and Environment Linkages Initiative. Fort Collins, Colorado, Centers for Disease Control and Prevention, malaria control, the power of integrated action. The Health and Environment Linkages Initiative, transmission of the Paralytic Rabies in Trinidad of the Vampire Bat, Desmodus rotundus murinus Wagner,1840. Annual Tropical Medicine and Parasitol,30, April 8,1936, pawan, J. L. Rabies in the Vampire Bat of Trinidad with Special Reference to the Clinical Course and the Latency of Infection
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Biology
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Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, evolution, distribution, identification and taxonomy. Modern biology is a vast and eclectic field, composed of branches and subdisciplines. However, despite the broad scope of biology, there are certain unifying concepts within it that consolidate it into single, coherent field. In general, biology recognizes the cell as the unit of life, genes as the basic unit of heredity. It is also understood today that all organisms survive by consuming and transforming energy and by regulating their internal environment to maintain a stable, the term biology is derived from the Greek word βίος, bios, life and the suffix -λογία, -logia, study of. The Latin-language form of the term first appeared in 1736 when Swedish scientist Carl Linnaeus used biologi in his Bibliotheca botanica, the first German use, Biologie, was in a 1771 translation of Linnaeus work. In 1797, Theodor Georg August Roose used the term in the preface of a book, karl Friedrich Burdach used the term in 1800 in a more restricted sense of the study of human beings from a morphological, physiological and psychological perspective. The science that concerns itself with these objects we will indicate by the biology or the doctrine of life. Although modern biology is a recent development, sciences related to. Natural philosophy was studied as early as the ancient civilizations of Mesopotamia, Egypt, the Indian subcontinent, however, the origins of modern biology and its approach to the study of nature are most often traced back to ancient Greece. While the formal study of medicine back to Hippocrates, it was Aristotle who contributed most extensively to the development of biology. Especially important are his History of Animals and other works where he showed naturalist leanings, and later more empirical works that focused on biological causation and the diversity of life. Aristotles successor at the Lyceum, Theophrastus, wrote a series of books on botany that survived as the most important contribution of antiquity to the plant sciences, even into the Middle Ages. Scholars of the medieval Islamic world who wrote on biology included al-Jahiz, Al-Dīnawarī, who wrote on botany, biology began to quickly develop and grow with Anton van Leeuwenhoeks dramatic improvement of the microscope. It was then that scholars discovered spermatozoa, bacteria, infusoria, investigations by Jan Swammerdam led to new interest in entomology and helped to develop the basic techniques of microscopic dissection and staining. Advances in microscopy also had a impact on biological thinking. In the early 19th century, a number of biologists pointed to the importance of the cell. Thanks to the work of Robert Remak and Rudolf Virchow, however, meanwhile, taxonomy and classification became the focus of natural historians
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Medicine
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Medicine is the science and practice of the diagnosis, treatment, and prevention of disease. The word medicine is derived from Latin medicus, meaning a physician, Medicine encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness. Medicine has existed for thousands of years, during most of which it was an art frequently having connections to the religious and philosophical beliefs of local culture. For example, a man would apply herbs and say prayers for healing, or an ancient philosopher. In recent centuries, since the advent of modern science, most medicine has become a combination of art, while stitching technique for sutures is an art learned through practice, the knowledge of what happens at the cellular and molecular level in the tissues being stitched arises through science. Prescientific forms of medicine are now known as medicine and folk medicine. They remain commonly used with or instead of medicine and are thus called alternative medicine. For example, evidence on the effectiveness of acupuncture is variable and inconsistent for any condition, in contrast, treatments outside the bounds of safety and efficacy are termed quackery. Medical availability and clinical practice varies across the world due to differences in culture. In modern clinical practice, physicians personally assess patients in order to diagnose, treat, the doctor-patient relationship typically begins an interaction with an examination of the patients medical history and medical record, followed by a medical interview and a physical examination. Basic diagnostic medical devices are typically used, after examination for signs and interviewing for symptoms, the doctor may order medical tests, take a biopsy, or prescribe pharmaceutical drugs or other therapies. Differential diagnosis methods help to rule out conditions based on the information provided, during the encounter, properly informing the patient of all relevant facts is an important part of the relationship and the development of trust. The medical encounter is then documented in the record, which is a legal document in many jurisdictions. Follow-ups may be shorter but follow the general procedure. The diagnosis and treatment may take only a few minutes or a few weeks depending upon the complexity of the issue, the components of the medical interview and encounter are, Chief complaint, the reason for the current medical visit. They are in the patients own words and are recorded along with the duration of each one, also called chief concern or presenting complaint. History of present illness, the order of events of symptoms. Distinguishable from history of illness, often called past medical history
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Organism
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In biology, an organism is any contiguous living system, such as an animal, plant, fungus, protist, archaeon, or bacterium. All known types of organisms are capable of some degree of response to stimuli, reproduction, growth and development and homeostasis. An organism consists of one or more cells, when it has one cell it is known as an organism. Most unicellular organisms are of microscopic scale and are thus described as microorganisms. Humans are multicellular organisms composed of trillions of cells grouped into specialized tissues. An organism may be either a prokaryote or a eukaryote, prokaryotes are represented by two separate domains—bacteria and archaea. Eukaryotic organisms are characterized by the presence of a cell nucleus. Fungi, animals and plants are examples of kingdoms of organisms within the eukaryotes, estimates on the number of Earths current species range from 10 million to 14 million, of which only about 1.2 million have been documented. More than 99% of all species, amounting to five billion species. In 2016, a set of 355 genes from the last universal ancestor of all living organisms living was identified. The term organism first appeared in the English language in 1703 and it is directly related to the term organization. There is a tradition of defining organisms as self-organizing beings. An organism may be defined as an assembly of molecules functioning as a more or less stable whole that exhibits the properties of life. Dictionary definitions can be broad, using such as any living structure, such as a plant, animal, fungus or bacterium, capable of growth. Many definitions exclude viruses and possible man-made non-organic life forms, as viruses are dependent on the machinery of a host cell for reproduction. A superorganism is an organism consisting of individuals working together as a single functional or social unit. There has been controversy about the best way to define the organism, several contributions are responses to the suggestion that the category of organism may well not be adequate in biology. Viruses are not typically considered to be organisms because they are incapable of autonomous reproduction and this controversy is problematic because some cellular organisms are also incapable of independent survival and live as obligatory intracellular parasites
8.
Parasitism
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In biology/ecology, parasitism is a non-mutual relationship between species, where one species, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred primarily to organisms visible to the naked eye, Parasites can be microparasites, which are typically smaller, such as protozoa, viruses, and bacteria. Examples of parasites include the plants mistletoe and cuscuta, and animals such as hookworms, unlike predators, parasites typically do not kill their host, are generally much smaller than their host, and will often live in or on their host for an extended period. Both are special cases of consumer-resource interactions, Parasites show a high degree of specialization, and reproduce at a faster rate than their hosts. Classic examples of parasitism include interactions between vertebrate hosts and tapeworms, flukes, the Plasmodium species, and fleas, parasitism differs from the parasitoid relationship in that parasitoids generally kill their hosts. Parasites reduce host biological fitness by general or specialized pathology, such as parasitic castration and impairment of secondary sex characteristics, Parasites increase their own fitness by exploiting hosts for resources necessary for their survival, e. g. food, water, heat, habitat, and transmission. Although parasitism applies unambiguously to many cases, it is part of a continuum of types of interactions between species, rather than an exclusive category, in many cases, it is difficult to demonstrate harm to the host. In others, there may be no apparent specialization on the part of the parasite, coined in English in 1611, the word parasitism comes from the Greek παρά + σιτισμός feeding, fattening. Parasites are classified based on their interactions with their hosts and on their life cycles, an obligate parasite is totally dependent on the host to complete its life cycle, while a facultative parasite is not. A direct parasite has one host while an indirect parasite has multiple hosts. For indirect parasites, there always be a definitive host. Parasites that live on the outside of the host, either on the skin or the outgrowths of the skin, are called ectoparasites and those that live inside the host are called endoparasites. Endoparasites can exist in one of two forms, intercellular parasites or intracellular parasites, intracellular parasites, such as protozoa, bacteria or viruses, tend to rely on a third organism, which is generally known as the carrier or vector. The vector does the job of transmitting them to the host, an example of this interaction is the transmission of malaria, caused by a protozoan of the genus Plasmodium, to humans by the bite of an anopheline mosquito. Those parasites living in a position, being half-ectoparasites and half-endoparasites, are called mesoparasites. An epiparasite is one that feeds on another parasite and this relationship is also sometimes referred to as hyperparasitism, exemplified by a protozoan living in the digestive tract of a flea living on a dog. Social parasites take advantage of interactions between members of social organisms such as ants, termites, and bumblebees, an extreme example of social parasitism is the ant species of Tetramorium inquilinum of the Alps, which spend their whole lives on the back of Tetramorium host ants. With tiny and deprecated bodies they have evolved for one single task, if they fall off, they most likely would not have the strength to climb back on top of another ant, and eventually they will die
9.
Mutualism (biology)
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Mutualism is the way two organisms of different species exist in a relationship in which each individual benefits from the activity of the other. Similar interactions within a species are known as co-operation, symbiosis involves two species living in close proximity and includes relationships that are mutualistic, parasitic, and commensal. Symbiotic relationships are sometimes, but not always, mutualistic, a well-known example of mutualism is the relationship between ungulates and bacteria within their intestines. The ungulates benefit from the produced by the bacteria, which facilitates digestion. This can also be found in many different symbiotic relationships. Mutualism plays a key part in ecology, in addition, mutualism is thought to have driven the evolution of much of the biological diversity we see, such as flower forms and co-evolution between groups of species. However mutualism has historically received less attention than other such as predation. It is therefore common to categorise mutualisms according to the closeness of the association, using such as obligate. Defining closeness, however, is also problematic and it can refer to mutual dependency or the biological intimacy of the relationship in relation to physical closeness. The term mutualism was introduced by Pierre-Joseph van Beneden in 1876, other examples include rhizobia bacteria that fix nitrogen for leguminous plants in return for energy-containing carbohydrates. Pollination in which nectar or pollen are traded for pollen dispersal or ant protection of aphids, phagophiles feed on ectoparasites, thereby providing anti-pest service, as in cleaning symbiosis. Elacatinus and Gobiosoma, genus of gobies, also feed on ectoparasites of their clients while cleaning them, zoochory is the dispersal of the seeds of plants by animals. This is similar to pollination in that the plant produces food resources for animals that disperse the seeds, strict service-service interactions are very rare, for reasons that are far from clear. Therefore, what appears to be a service-service mutualism in fact has a service-resource component, a second example is that of the relationship between some ants in the genus Pseudomyrmex and trees in the genus Acacia, such as the whistling thorn and bullhorn acacia. The ants nest inside the plants thorns, in exchange for shelter, the ants protect acacias from attack by herbivores and competition from other plants by trimming back vegetation that would shade the acacia. In addition, another component is present, as the ants regularly feed on lipid-rich food-bodies called Beltian bodies that are on the Acacia plant. In the neotropics, the ant, Myrmelachista schumanni makes its nest in cavities in Duroia hirsute. Plants in the vicinity that belong to other species are killed with formic acid and this selective gardening can be so aggressive that small areas of the rainforest are dominated by Duroia hirsute
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Commensalism
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Commensalism, in ecology, is a class of relationships between two organisms where one organism benefits from the other without affecting it. Originally, the term was used to describe the use of food by second animals, like the carcass eaters that follow hunting animals. Commensalism, in biology, is a relation between individuals of two species in one species obtains food or other benefits from the other without either harming or benefiting the latter. The commensal may obtain nutrients, shelter, support, or locomotion from the host species, both remora and pilot fish feed on the leftovers of their hosts’ meals. Numerous birds feed on the turned up by grazing mammals. The commensal pathway was traveled by animals that fed on refuse around human habitats or by animals that preyed on other animals drawn to human camps and those animals established a commensal relationship with humans in which the animals benefited but the humans received little benefit or harm. Those animals that were most capable of taking advantage of the associated with human camps would have been the tamer. Later, these animals developed closer social or economic bonds with humans, commensal pathway animals include dogs, cats, fowl, and possibly pigs. The dog is an example of a domestic animal that likely traveled a commensal pathway into domestication. This process may have begun during the initial stage of dog domestication. One study has identified the remains of a population of extinct Pleistocene Beringian wolves with unique mitochondrial signatures, whether the relationship between humans and some types of gut flora is commensal or mutualistic is still unanswered. For example, epiphytes are nutritional pirates that may intercept substantial amounts of nutrients that would go to the host plant. Large numbers of epiphytes can also cause tree limbs to break or shade the host plant, similarly, phoretic mites may hinder their host by making flight more difficult, which may affect its aerial hunting ability or cause it to expend extra energy while carrying these passengers. Like all ecological interactions, commensalisms vary in strength and duration from intimate, long-lived symbioses to brief, phoresy is one animal attached to another exclusively for transport, mainly arthropods, examples of which are mites on insects, pseudoscorpions on mammals or beetles, and millipedes on birds. Phoresy can be obligate or facultative. Inquilinism is the use of an organism for permanent housing. Examples are epiphytic plants grow on trees, or birds that live in holes in trees. Metabiosis is a more indirect dependency, in one organism creates or prepares a suitable environment for a second
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Symbiosis
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Symbiosis is any type of a close and long-term biological interaction between two different species, be it mutualistic, commensalistic, or parasitic. In 1879, Heinrich Anton de Bary defined it as the living together of unlike organisms, Symbiosis can be obligatory, which means that one or both of the symbionts entirely depend on each other for survival, or facultative when they can generally live independently. When one organism lives on another such as mistletoe, it is called ectosymbiosis, or endosymbiosis when one partner lives inside the tissues of another, as in Symbiodinium in corals. In 1877, Albert Bernhard Frank used the term symbiosis which previously had used to depict people living together in community 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, symbiotic relationships can be obligate, meaning that one or both of the symbionts entirely depend on each other for survival. For example, in lichens, which consist of fungal and photosynthetic symbionts, the algal or cyanobacterial symbionts in lichens, such as Trentepohlia, can generally live independently, and their symbiosis is, therefore, facultative. Endosymbiosis is any relationship in which one symbiont lives within the tissues of the other, either within the cells or extracellularly. Mutualism or interspecies reciprocal altruism is a relationship between individuals of different species where both individuals benefit, in general, only lifelong interactions involving close physical and biochemical contact can properly be considered symbiotic. 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, which is 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, and mycorrhyzal fungi, which help in extracting water, an example of mutual symbiosis 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, and 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 the fish, which sometimes lives together with a shrimp. The shrimp digs and cleans up a burrow in the sand in which both the shrimp and the fish live. The shrimp is almost blind, leaving it vulnerable to predators when outside its burrow, in case of danger the goby fish touches the shrimp with its tail to warn it. When that happens both the shrimp and goby fish quickly retreat into the burrow, different species of gobies also exhibit mutualistic behavior through cleaning up ectoparasites in other fish. Another non-obligate symbiosis is known from encrusting bryozoans and hermit crabs, the bryozoan colony develops a cirumrotatory growth and offers the crab a helicospiral-tubular extension of its living chamber that initially was situated within a gastropod shell. A spectacular examples of mutualism is between the siboglinid tube worms and symbiotic bacteria that live at hydrothermal vents and cold seeps
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Animal
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Animals are multicellular, eukaryotic organisms of the kingdom Animalia. The animal kingdom emerged as a clade within Apoikozoa as the group to the choanoflagellates. Animals are motile, meaning they can move spontaneously and independently at some point in their lives and their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later in their lives. All animals are heterotrophs, they must ingest other organisms or their products for sustenance, most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago. Animals can be divided broadly into vertebrates and invertebrates, vertebrates have a backbone or spine, and amount to less than five percent of all described animal species. They include fish, amphibians, reptiles, birds and mammals, the remaining animals are the invertebrates, which lack a backbone. These include molluscs, arthropods, annelids, nematodes, flatworms, cnidarians, ctenophores, the study of animals is called zoology. The word animal comes from the Latin animalis, meaning having breath, the biological definition of the word refers to all members of the kingdom Animalia, encompassing creatures as diverse as sponges, jellyfish, insects, and humans. Aristotle divided the world between animals and plants, and this was followed by Carl Linnaeus, in the first hierarchical classification. In Linnaeuss original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, in 1874, Ernst Haeckel divided the animal kingdom into two subkingdoms, Metazoa and Protozoa. The protozoa were later moved to the kingdom Protista, leaving only the metazoa, thus Metazoa is now considered a synonym of Animalia. Animals have several characteristics that set apart from other living things. Animals are eukaryotic and multicellular, which separates them from bacteria and 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. All animals are motile, if only at life stages. In most animals, embryos pass through a stage, which is a characteristic exclusive to animals. With a few exceptions, most notably the sponges and Placozoa and these include muscles, which are able to contract and control locomotion, and nerve tissues, which send and process signals
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Worm
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Worms /ˈwɜːrm/ are many different distantly related animals that typically have a long cylindrical tube-like body and no limbs. Various types of worm occupy a variety of parasitic niches. Free-living worm species do not live on land, but instead live in marine or freshwater environments, in biology, worm refers to an obsolete taxon, vermes, used by Carolus Linnaeus and Jean-Baptiste Lamarck for all non-arthropod invertebrate animals, now seen to be paraphyletic. The name stems from the Old English word wyrm, most animals called worms are invertebrates, but the term is also used for the amphibian caecilians and the slow worm Anguis, a legless burrowing lizard. Invertebrate animals commonly called worms include annelids, nematodes, platyhelminthes, marine worms, marine Chaetognatha, priapulid worms. Worms may also be called helminths, particularly in medical terminology when referring to parasitic worms, when an animal or human is said to have worms, it means that it is infested with parasitic worms, typically roundworms or tapeworms. Lungworm is also a parasitic worm found in various animal species such as fish. Worms can be divided into groups, but are still technically decomposers. The first of these, Platyhelminthes, includes the flatworms, tapeworms and they have a flat, ribbon- or leaf-shaped body with a pair of eyes at the front. The second group contains the threadworms, roundworms, and hookworms, threadworms may be microscopic, such as the vinegar eelworm, or more than 1 metre long. They are found in earth, moss, decaying substances, fresh water. The Guinea worm, for example, gets under the skin of the feet, the third group consists of the segmented worms, with bodies divided into segments, or rings. Among these are the earthworms and the worms of the sea. In earlier taxonomic classification, all the above were included in the now obsolete group Vermes, familiar worms include the earthworms, members of phylum Annelida. Other invertebrate groups may be called worms, especially colloquially, in particular, many unrelated insect larvae are called worms, such as the railroad worm, woodworm, glowworm, bloodworm, inchworm, mealworm, silkworm, and wooly bear worm. Worms may also be called helminths, particularly in medical terminology when referring to parasitic worms, hence helminthology is the study of parasitic worms. When a human or an animal, such as a dog or horse, is said to have worms, it means that it is infested with parasitic worms, deworming is a method to kill off the worms that have infected a human or animal by giving anthelmintic drugs. Ringworm is not a worm at all, but a skin fungus, wurm, or wyrm was the Old English term for carnivorous reptiles, and mythical dragons
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Nematode
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The nematodes or roundworms constitute the phylum Nematoda. They are an animal phylum inhabiting a broad range of environments. Nematodes are classified along with insects and other moulting animals in the clade Ecdysozoa, Nematodes have successfully adapted to nearly every ecosystem from marine to fresh water, to soils, and from the polar regions to the tropics, as well as the highest to the lowest of elevations. They are found in part of the earths lithosphere, even at great depths below the surface of the Earth in gold mines in South Africa. They represent 90% of all animals on the ocean floor, the many parasitic forms include pathogens in most plants and animals. The location of towns would be decipherable, since for every massing of human beings there would be a corresponding massing of certain nematodes, trees would still stand in ghostly rows representing our streets and highways. In 1758, Linnaeus described some nematode genera, then included in Vermes, the name of the group Nematoda, informally called nematodes, came from Nematoidea, originally defined by Karl Rudolphi, from Ancient Greek νῆμα and -eiδἠς. It was treated as family Nematodes by Burmeister, at its origin, the Nematoidea erroneously included Nematodes and Nematomorpha, attributed by von Siebold. Along with Acanthocephala, Trematoda and Cestoidea, it formed the obsolete group Entozoa and they were also classed along with Acanthocephala in the obsolete phylum Nemathelminthes by Gegenbaur. In 1861, K. M. Diesing treated the group as order Nematoda, in 1877, the taxon Nematoidea, including the family Gordiidae, was promoted to the rank of phylum by Ray Lankester. In 1919, Nathan Cobb proposed that nematodes should be recognized alone as a phylum and he argued they should be called nema in English rather than nematodes and defined the taxon Nemates, listing Nematoidea sensu restricto as a synonym. Since Cobb was the first to all but nematodes from the group, some sources consider the valid taxon name to be Nemates or Nemata. The phylogenetic relationships of the nematodes and their close relatives among the protostomian Metazoa are unresolved, traditionally, they were held to be a lineage of their own but in the 1990s, they were proposed to form the group Ecdysozoa together with moulting animals, such as arthropods. The identity of the closest living relatives of the Nematoda has always considered to be well resolved. Morphological characters and molecular phylogenies agree with placement of the roundworms as a taxon to the parasitic Nematomorpha. Together with the Scalidophora, the Nematoida form the clade Cycloneuralia, the Cycloneuralia or the Introverta—depending on the validity of the former—are often ranked as a superphylum. Due to the lack of knowledge regarding many nematodes, their systematics is contentious, an earliest and influential classification was proposed by Chitwood and Chitwood—later revised by Chitwood—who divided the phylum into two—the Aphasmidia and the Phasmidia. These were later renamed Adenophorea and Secernentea, respectively, the Secernentea share several characteristics, including the presence of phasmids, a pair of sensory organs located in the lateral posterior region, and this was used as the basis for this division
15.
Cell (biology)
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The cell is the basic structural, functional, and biological unit of all known living organisms. A cell is the smallest unit of life that can replicate independently, the study of cells is called cell biology. Cells consist of cytoplasm enclosed within a membrane, which contains many such as proteins. Organisms can be classified as unicellular or multicellular, while the number of cells in plants and animals varies from species to species, humans contain more than 10 trillion cells. Most plant and animal cells are only under a microscope. The cell was discovered by Robert Hooke in 1665, who named the unit for its resemblance to cells inhabited by Christian monks in a monastery. Cells emerged on Earth at least 3.5 billion years ago, Cells are of two types, eukaryotic, which contain a nucleus, and prokaryotic, which do not. Prokaryotes are single-celled organisms, while eukaryotes can be either single-celled or multicellular, prokaryotic cells were the first form of life on Earth, characterised by having vital biological processes including cell signaling and being self-sustaining. They are simpler and smaller than eukaryotic cells, and lack membrane-bound organelles such as the nucleus, prokaryotes include two of the domains of life, bacteria and archaea. The DNA of a prokaryotic cell consists of a chromosome that is in direct contact with the cytoplasm. The nuclear region in the cytoplasm is called the nucleoid, most prokaryotes are the smallest of all organisms ranging from 0.5 to 2.0 µm in diameter. Though most prokaryotes have both a cell membrane and a wall, there are exceptions such as Mycoplasma and Thermoplasma which only possess the cell membrane layer. The envelope gives rigidity to the cell and separates the interior of the cell from its environment, the cell wall consists of peptidoglycan in bacteria, and acts as an additional barrier against exterior forces. It also prevents the cell from expanding and bursting from osmotic pressure due to a hypotonic environment, some eukaryotic cells also have a cell wall. Inside the cell is the region that contains the genome, ribosomes. The genetic material is found in the cytoplasm. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are usually circular, linear bacterial plasmids have been identified in several species of spirochete bacteria, including members of the genus Borrelia notably Borrelia burgdorferi, which causes Lyme disease. Though not forming a nucleus, the DNA is condensed in a nucleoid, plasmids encode additional genes, such as antibiotic resistance genes
16.
Fabaceae
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The Fabaceae, Leguminosae or Papilionaceae, commonly known as the legume, pea, or bean family, are a large and economically important family of flowering plants. It includes trees, shrubs, and perennial or annual herbaceous plants, the five largest of the genera are Astragalus, Acacia, Indigofera, Crotalaria and Mimosa, which constitute about a quarter of all legume species. The ca.19,000 known legume species amount to about 7% of flowering plant species, Fabaceae is the most common family found in tropical rainforests and in dry forests in the Americas and Africa. Recent molecular and morphological evidence supports the fact that the Fabaceae is a monophyletic family. These studies confirm that the Fabaceae are a group that is closely related to the Polygalaceae, Surianaceae and Quillajaceae families. Along with the cereals, some fruits and tropical roots a number of Leguminosae have been a human food for millennia. A number of species are also weedy pests in different parts of the world, including, Cytisus scoparius, Robinia pseudoacacia, Ulex europaeus, Pueraria lobata, the name Fabaceae comes from the defunct genus Faba, now included in Vicia. The term faba comes from Latin, and appears to simply mean bean, Leguminosae is an older name still considered valid, and refers to the fruit of these plants, which are called legumes. Fabaceae range in habit from giant trees to small annual herbs, plants have indeterminate inflorescences, which are sometimes reduced to a single flower. The flowers have a short hypanthium and a single carpel with a short gynophore, the Leguminosae have a wide variety of growth forms including trees, shrubs or herbaceous plants or even vines or lianas. The herbaceous plants can be annuals, biennials or perennials, without basal or terminal leaf aggregations and they are upright plants, epiphytes or vines. The latter support themselves by means of shoots that twist around a support or through cauline or foliar tendrils, plants can be heliophytes, mesophytes or xerophytes. The leaves are alternate and compound. Most often they are even- or odd-pinnately compound, often trifoliate and rarely palmately compound, in the Mimosoideae and they always have stipules, which can be leaf-like, thorn-like or be rather inconspicuous. Leaf margins are entire or, occasionally, serrate, both the leaves and the leaflets often have wrinkled pulvini to permit nastic movements. In some species, leaflets have evolved into tendrils, many species have leaves with structures that attract ants that protect the plant from herbivore insects. Extrafloral nectaries are common among the Mimosoideae and the Caesalpinioideae, and are found in some Faboideae. In some Acacia, the modified hollow stipules are inhabited by ants and are known as domatia, many Fabaceae host bacteria in their roots within structures called root nodules
17.
Rhizobia
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Rhizobia are soil bacteria that fix nitrogen after becoming established inside root nodules of legumes. In order to express genes for nitrogen fixation, rhizobia require a plant host, in general, they are Gram-negative, motile, non-sporulating rods. The first known species of rhizobia, Rhizobium leguminosarum, was identified in 1889, however, more advanced methods of analysis have revised this classification, and now there are many in other genera. Most research has been done on crop and forage legumes such as clover, alfalfa, beans, peas, the word rhizobia comes from the Ancient Greek ῥίζα, rhíza, meaning root and βίος, bios, meaning life. The word rhizobium is still used as the singular form of rhizobia Rhizobia are a paraphyletic group that fall into two classes of the proteobacteria—the alpha- and beta-proteobacteria. As shown below, most belong to the order Rhizobiales, and these groups include a variety of non-symbiotic bacteria. For instance, the plant pathogen Agrobacterium is a relative of Rhizobium than the Bradyrhizobium that nodulate soybean. The genes responsible for the symbiosis with plants, however, may be closely related than the organisms themselves. Evidence suggests that symbiosis islands exist and share similarities to pathogenicity islands, although much of the nitrogen is removed when protein-rich grain or hay is harvested, significant amounts can remain in the soil for future crops. This is especially important when nitrogen fertilizer is not used, as in organic rotation schemes or some less-industrialized countries, Nitrogen is the most commonly deficient nutrient in many soils around the world and it is the most commonly supplied plant nutrient. Supply of nitrogen through fertilizers has severe environmental concerns, Rhizobia is “the group of soil bacteria that infect the roots of legumes to form root nodules”. Rhizobia are found in the soil and after infection, produce nodules in the legume where they fix nitrogen gas from the atmosphere turning it into a more useful form of nitrogen. From here, the nitrogen is exported from the nodules and used for growth in the legume, once the legume dies, the nodule breaks down and releases the rhizobia back into the soil where they can live individually or reinfect a new legume host. Specific strains of rhizobia are required to make functional nodules on the roots able to fix the N2, having this specific rhizobia present is beneficial to the legume, as the N2 fixation can increase crop yield. Inoculation with rhizobia tends to increase yield, Legume inoculation has been an agriculture practice for many years and has continuously improved over time. 12-20 million hectares of soybeans are inoculated annually, the technology to produce these inoculants are microbial fermenters. Once this ideal inoculant in produced it is most likely in a liquid or powder form where it is applied directly to the seed before planting, many poor countries have trouble with the introduction of new crops and reaching attainable yield. As they introduce new crops into their soils, these inoculants may foster legume growth and success in the area, using these inoculants provide many other benefits as well such as not having to use nitrogen fertilizers
18.
Botany
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Botany, also called plant science, plant biology or phytology, is the science of plant life and a branch of biology. A botanist or plant scientist is a scientist who specialises in this field, the term botany comes from the Ancient Greek word βοτάνη meaning pasture, grass, or fodder, βοτάνη is in turn derived from βόσκειν, to feed or to graze. Nowadays, botanists study approximately 410,000 species of plants of which some 391,000 species are vascular plants. Medieval physic gardens, often attached to monasteries, contained plants of medical importance and they were forerunners of the first botanical gardens attached to universities, founded from the 1540s onwards. One of the earliest was the Padua botanical garden and these gardens facilitated the academic study of plants. Efforts to catalogue and describe their collections were the beginnings of plant taxonomy, in the last two decades of the 20th century, botanists exploited the techniques of molecular genetic analysis, including genomics and proteomics and DNA sequences to classify plants more accurately. Modern botany is a broad, multidisciplinary subject with inputs from most other areas of science, dominant themes in 21st century plant science are molecular genetics and epigenetics, which are the mechanisms and control of gene expression during differentiation of plant cells and tissues. Botany originated as herbalism, the study and use of plants for their medicinal properties, many records of the Holocene period date early botanical knowledge as far back as 10,000 years ago. This early unrecorded knowledge of plants was discovered in ancient sites of human occupation within Tennessee, the early recorded history of botany includes many ancient writings and plant classifications. Examples of early works have been found in ancient texts from India dating back to before 1100 BC, in archaic Avestan writings. His major works, Enquiry into Plants and On the Causes of Plants, constitute the most important contributions to science until the Middle Ages. De Materia Medica was widely read for more than 1,500 years, important contributions from the medieval Muslim world include Ibn Wahshiyyas Nabatean Agriculture, Abū Ḥanīfa Dīnawarīs the Book of Plants, and Ibn Bassals The Classification of Soils. In the early 13th century, Abu al-Abbas al-Nabati, and Ibn al-Baitar wrote on botany in a systematic and scientific manner and these gardens continued the practical value of earlier physic gardens, often associated with monasteries, in which plants were cultivated for medical use. They supported the growth of botany as an academic subject, lectures were given about the plants grown in the gardens and their medical uses demonstrated. Botanical gardens came much later to northern Europe, the first in England was the University of Oxford Botanic Garden in 1621, throughout this period, botany remained firmly subordinate to medicine. German physician Leonhart Fuchs was one of the three German fathers of botany, along with theologian Otto Brunfels and physician Hieronymus Bock, Fuchs and Brunfels broke away from the tradition of copying earlier works to make original observations of their own. Bock created his own system of plant classification, physician Valerius Cordus authored a botanically and pharmacologically important herbal Historia Plantarum in 1544 and a pharmacopoeia of lasting importance, the Dispensatorium in 1546. Naturalist Conrad von Gesner and herbalist John Gerard published herbals covering the medicinal uses of plants, naturalist Ulisse Aldrovandi was considered the father of natural history, which included the study of plants
19.
Nutrient
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A nutrient is a component in foods that an organism uses to survive and grow. Macronutrients provide the energy an organisms metabolic system needs to function while micronutrients provide the necessary cofactors for metabolism to be carried out. Both types of nutrients can be acquired from the environment, micronutrients are used to build and repair tissues and to regulate body processes while macronutrients are converted to, and used for, energy. Methods of nutrient intake are different for plants and animals, plants take in nutrients directly from the soil through their roots and from the atmosphere through their leaves. Animals and protists have specialized digestive systems that work to break down macronutrients for energy, organic nutrients consist of carbohydrates, fats, proteins, and vitamins. Inorganic chemical compounds such as minerals, water, and oxygen may also be considered nutrients. A nutrient is considered if it must be obtained from an external source either because the organism cannot synthesize it or because insufficient quantities are produced. Nutrients needed in small amounts are called micronutrients while those needed in large quantities are called macronutrients. The effects of nutrients are dose-dependent, shortages are called deficiencies, macronutrients are defined in several different ways. The chemical elements humans consume in the largest quantities are carbon, hydrogen, nitrogen, oxygen, phosphorus, the classes of chemical compounds humans consume in the largest quantities and which provide bulk energy are carbohydrates, proteins, and fats. Water and atmospheric oxygen also must be consumed in large quantities, calcium, salt, magnesium, and potassium are sometimes added to the list of macronutrients because they are required in large quantities compared to other vitamins and minerals. They are sometimes referred to as the macrominerals, carbohydrates are compounds made up of types of sugars. Carbohydrates are classified by their number of units, monosaccharides, disaccharides, oligosaccharides. Proteins are organic compounds that consist of amino acids joined by peptide bonds, the body cannot manufacture some of the amino acids, the diet must supply them. Proteins, in nutrition, are broken down through digestion by proteases back into free amino acids, fats consist of a glycerin molecule with three fatty acids attached. Fatty acids are unbranched hydrocarbon chains,1 connected by single bonds alone or by double and single bonds. Fats are needed to keep cell membranes functioning properly, to insulate body organs against shock, to body temperature stable. The body does not manufacture certain fatty acids and the diet must supply them, although alcohol provides energy, and can thus be compared to macronutrients, it is not a substance that is essential for normal function
20.
Parasitoid
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A parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism in a relationship where the host is ultimately killed. Thus, parasitoidy is an evolutionary strategy to typical parasitism. There are parasitoids in a variety of taxa, including microbial diseases, plants, crustaceans, insects. Especially among the Hymenoptera, ichneumons and many wasps are highly specialised for a way of life. Some parasitoidal wasps are used in biological pest control, the term parasitoid was coined in 1913 by the Swedo-Finnish writer Odo Morannal Reuter, and adopted in English by his reviewer, William Morton Wheeler. Reuter used it to describe the strategy where the parasite develops in or on the body of a single host individual, eventually killing that host, since that time, the concept has been variously generalised and widely applied. These are adaptive peaks, with possible intermediate strategies. Parasitoids eventually kill their host, typically before it can produce offspring, a nonlethal parasitic organism, especially if it is a fungus, is sometimes termed a biotroph, while a parasitoidal fungus may be called a necrotroph. Idiobiont parasitoids prevent further development of the host after initially immobilizing it, koinobiont parasitoids allow the host to continue its development while feeding upon it, and may parasitise any host life stage. There is no separation between conventional parasitism and parasitoidy. For example, blood-sucking mites sometimes overwhelm nestlings of birds such as swallows to the point that the birds cannot fledge successfully. At the opposite extreme, parasitoidy grades into predation, differences between various hunting wasps provide convenient illustrations. Predatory social wasps hunt flies, caterpillars and the like, grab them, butcher them, carry them home and feed them to their young. Similarly, some solitary wasps such as beewolves, sting prey, sometimes fatally, before saving it, usually entire, in contrast, the best-known protelean solitary hunting wasps sting prey to paralyse it before storing it for the young in the nest. Other wasps paralyse prey in the plant or other environment in which it feeds, before laying eggs nearby, some insect parasitoids lay their eggs where the larvae must locate the prey for themselves when they hatch from the eggs. Examples include flies in the families Tachinidae and Bombyliidae, often with sophisticated physiological, in another strategy, some parasitoids influence the hosts behaviour in ways that favour the propagation of the parasitoid, often at the cost of the hosts life. Similarly, as strepsipteran parasitoids of ants mature, they cause the hosts to climb high on grass stalks, positions that are risky, but favour the emergence of the strepsipterans. Other species of endoparasitoids cause infected woodlice and land Amphipoda such as Talitroides to run about in the open by day, the rabies virus affects the hosts central nervous system, eventually killing it, but perhaps helping to disseminate the virus by modifying the hosts behaviour
21.
Predation
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In an ecosystem, predation is a biological interaction where a predator feeds on its prey. Predators may or may not kill their prey prior to feeding on it, but the act of predation often results in the death of the prey, thus predation is often, though not always, carnivory. Other categories of consumption are herbivory, fungivory, and detritivory, all of these are consumer-resource systems. It can often be difficult to separate various types of feeding behaviors. For example, some parasites prey on their host and then lay their eggs on it, for their offspring to feed on it while it continues to live, the key characteristic of predation is the predators direct impact on the prey population. Selective pressures imposed on one another leads to an evolutionary arms race between prey and predator, resulting in various antipredator adaptations. Ways of classifying predation include grouping by trophic level or diet, by specialization, Predators can be classified by their interactions with their prey. Two factors are considered here, how close the predator and prey are, and whether the prey is killed by the predator. A true predator is one that kills and eats another living thing, Predators may hunt actively for prey in pursuit predation, or sit and wait for prey to approach within striking distance, as in ambush predators. Some predation entails venom that subdues a prey before the predator ingests it, as in the box jellyfish, or disables it, in some cases, the venom contributes to the digestion of the prey, as in rattlesnakes and some spiders. In contrast, baleen whales eat millions of microscopic plankton at once, seed and egg predation are true predation, as seeds and eggs are potential organisms. Predators need not eat prey entirely, for example, some predators cannot digest bones, some may eat only part of an organism, but still consistently cause its death. Grazing organisms do not often kill their prey, while some herbivores like zooplankton live on unicellular phytoplankton and therefore, by the individualized nature of the organism, kill their prey, many others only eat a small part of the plant. Grazing livestock may pull some grass out at the roots, but most is simply grazed upon, kelp is frequently grazed in subtidal kelp forests, but regrows at the base of the blade continuously to cope with browsing pressure. Animals may also be grazed upon, female mosquitos land on hosts briefly to gain sufficient proteins for the development of their offspring, starfish may be grazed on, being capable of regenerating lost arms. Parasites can at times be difficult to distinguish from grazers and their feeding behavior is similar in many ways, however they are noted for their close association with their host species. This close living arrangement may be described by the symbiosis, living together. Parasitic organisms range from the mistletoe, a parasitic plant
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Herbivore
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A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthparts adapted to rasping or grinding, horses and other herbivores have wide flat teeth that are adapted to grinding grass, tree bark, and other tough plant material. A large percentage of herbivores have mutualistic gut flora that help them digest plant matter and this gut flora is made up of cellulose-digesting protozoans or bacteria living in the herbivores intestines. Herbivore is the form of a modern Latin coinage, herbivora. Richard Owen employed the term in an 1854 work on fossil teeth. Herbivora is derived from the Latin herba meaning a small plant or herb, Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms feed on autotrophs in general are known as primary consumers. Herbivory usually refers to eating plants, fungi, bacteria and protists that feed on living plants are usually termed plant pathogens. Flowering plants that obtain nutrition from other living plants are usually termed parasitic plants, there is however no single exclusive and definitive ecological classification of consumption patterns, each textbook has its own variations on the theme. Insects fed on the spores of early Devonian plants, and the Rhynie chert also provides evidence that organisms fed on plants using a pierce, during the next 75 million years, plants evolved a range of more complex organs, such as roots and seeds. There is no evidence of any organism being fed upon until the middle-late Mississippian,330.9 million years ago, further than their arthropod status, the identity of these early herbivores is uncertain. Hole feeding and skeletonisation are recorded in the early Permian, with surface fluid feeding evolving by the end of that period, Herbivory among four-limbed terrestrial vertebrates, the tetrapods developed in the Late Carboniferous. Early tetrapods were large amphibious piscivores, while amphibians continued to feed on fish and insects, some reptiles began exploring two new food types, tetrapods and plants. The entire dinosaur order ornithischia was composed with herbivores dinosaurs, carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation. In contrast, a set of adaptations was necessary for feeding on highly fibrous plant materials. Arthropods evolved herbivory in four phases, changing their approach to it in response to changing plant communities, tetrapod herbivores made their first appearance in the fossil record of their jaws near the Permio-Carboniferous boundary, approximately 300 million years ago. The earliest evidence of their herbivory has been attributed to dental occlusion, the evolution of dental occlusion led to a drastic increase in plant food processing and provides evidence about feeding strategies based on tooth wear patterns. Examination of phylogenetic frameworks of tooth and jaw morphologes has revealed that dental occlusion developed independently in several lineages tetrapod herbivores and this suggests that evolution and spread occurred simultaneously within various lineages
23.
Brood parasite
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Brood parasites are organisms that rely on others to raise their young. The strategy appears among birds, insects and some fish, the brood parasite manipulates a host, either of the same or of another species, to raise its young as if it were its own. Bird parasite species mitigate the risk of egg loss by distributing eggs amongst a number of different hosts, as this behaviour damages the host, it often results in an evolutionary arms race between parasite and host as the pair of species coevolve. This form of cuckoldry is taken a step further when females of the goldeneye often lay their eggs in the nests of other individuals, intraspecific brood parasitism is seen in a number of duck species, where females often lay their eggs in the nests of others. Interspecific brood-parasites include the indigobirds, whydahs, and honeyguides in Africa, cowbirds, Old World cuckoos, black-headed ducks, seven independent origins of obligate interspecific brood parasitism in birds have been proposed. They usually lay one egg per nest, although in some cases, particularly the cowbirds. Genes regulating egg coloration appear to be passed down exclusively along the maternal line, females generally parasitize nests of the species which raised them. Male common cuckoos fertilize females of all lines, which maintains sufficient gene flow among the different maternal lines to prevent speciation, the mechanisms of host selection by female cuckoos are somewhat unclear, though several hypotheses have been suggested in attempt to explain the choice. Of these hypotheses the nest-site selection and habitat selection have been most supported by experimental analysis, among specialist avian brood parasites, mimetic eggs are a nearly universal adaptation. There is even evidence that the generalist brown-headed cowbird may have evolved an egg coloration mimicking a number of their hosts. Most avian brood parasites remove a host egg when they lay one of their own in a nest, depending upon the species, this can happen either in the same visit to the host nest or in a separate visit before or after the parasitism. This both prevents the host species from realizing their nest has been parasitized and reduces competition for the parasitic nestling once it hatches, most avian brood parasites have very short egg incubation periods and rapid nestling growth. This gives the parasitic nestling a head start on growth over its nestmates, in many brood parasites, such as cuckoos and honeyguides, this short egg incubation period is due to internal incubation periods up to 24 hours longer in cuckoos than hosts. Where the host nestlings are significantly smaller than the parasite nestling, some brood parasites eliminate all their nestmates shortly after hatching, either by ejecting them from the nest or killing them with sharp mandible hooks which fall off after a few days. There is a question as to why the majority of the hosts of brood parasites care for the nestlings of their parasites. Not only do these parasites usually differ significantly in size and appearance. The mafia hypothesis evolved through studies in an attempt to answer this question and this hypothesis revolves around host manipulations induced by behaviors of the brood parasite. Upon the detection and rejection of a brood egg, the hosts nest is depredated upon, its nest destroyed
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Cuckoo
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The cuckoos are a family of birds, Cuculidae, the sole taxon in the order Cuculiformes. The cuckoo family includes the common or European cuckoo, roadrunners, koels, malkohas, couas, coucals, the coucals and anis are sometimes separated as distinct families, the Centropodidae and Crotophagidae respectively. The cuckoos are generally medium-sized slender birds, the majority are arboreal, with a sizeable minority that are terrestrial. The family has a distribution, with the majority of species being tropical. The cuckoos feed on insects, insect larvae and a variety of other animals, some species are brood parasites, laying their eggs in the nests of other species, but the majority of species raise their own young. Cuckoos have played a role in culture for thousands of years. In Europe, the cuckoo is associated with spring, and with cuckoldry, in India, cuckoos are sacred to Kamadeva, the god of desire and longing, whereas in Japan, the cuckoo symbolises unrequited love. Cuckoos are medium-sized birds that range in size from the little cuckoo, at 17 g and 15 cm, to the channel-billed cuckoo. There is generally sexual dimorphism in size, but where it exists. One of the most important distinguishing features of the family are the feet, there are two basic body forms, arboreal species which are slender and have short tarsi, and terrestrial species which are more heavy set and have long tarsi. Almost all species have long tails which are used for steering in terrestrial species, the subfamily Cuculinae are the brood-parasitic cuckoos of the Old World. They tend to conform to the shape, with long tails, short legs, long narrow wings. The largest species, the cuckoo, also has the most outsized bill in the family. The subfamily Phaenicophaeinae are the cuckoos of the Old World, and include the couas, malkohas. They are more terrestrial cuckoos, with strong and often long legs, the subfamily typically has brighter plumage and brightly coloured bare skin around the eye. The coucals are another terrestrial subfamily of long tailed long legged and they are large heavyset birds with the largest, the greater black coucal, being around the same size as the channel-billed cuckoo. The subfamily Coccyzinae are arboreal and long tailed as well, with a number of large insular forms, the final subfamily are the atypical anis, which include the small clumsy anis and the larger guira cuckoo. The anis have massive bills and smooth glossy feathers, the feathers of the cuckoos are generally soft, and often become waterlogged in heavy rain
25.
Gene polymorphism
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A gene is said to be polymorphic if more than one allele occupies that gene’s locus within a population. For example in dogs the E locus, which controls coat pattern, can have any of five different alleles, known as E, Em, Eg, Eh, and e. A polymorphic variant of a gene may lead to the expression or to the production of an abnormal form of the gene. Most notably, the coding for the Major Histocompatibility Complex are in fact the most polymorphic genes known. In fact there are more than 800 different alleles of human MHC class I, in contrast, gene polymorphism is defined as a variation that occurs in allele in a DNA sequence. Gene polymorphisms are caused by duplications, deletions, and a mutation of triplication of high quantity of DNA base pairs sequences, in addition, Polymorphisms may occur due to changes inside introns or changes in regions that one or multiple DNA bases that are between genes. If the changes occur in a coding sequence, then different phenotypes may appear as a result of protein variation that is caused by sequence changes. These changes are located exactly in genes’ coding sequence, there are four types of gene polymorphisms, SNPs are a single nucleotide changes that happen in the genome in a particular location. The Single Nucleotide Polymorphism is known to be the most common form of genetic variation, a major and the cause of this SNPs is the replacement of the nucleotide Cytosine with Thymine in a part of the DNA. SNPs may cause a disease through the affection in a gene or regulatory region near this gene resulting in disturbance in the genes function. Small insertions and deletion are called INDELs and this type of polymorphism is dependent on insertion or deletion of DNA bases in an organism. Nowadays, two million INDELs have been discovered in approximately seventy-nine various humans genomes, furthermore, small insertions/ deletions are existed on genes coding exons and this may consider a fundamental factor that leads to diseases inheritance in humans. Alu which is an element from Alu family, can trigger a polymorphism in human genome. Alu element is defined as an area of DNA sequence with 300 base pairs. Alu element also has a role in RNA polymerase III for its compression of a RNA promoter and it has been found that Alu is repeated in more than 10% of human genome. Insertion and repetitive of Alu element in human genome can cause mutations, microsatellites are characterized for the repetition for 1-6 base pairs of DNA sequence. In Genetics, microsatellites are used as a molecular markers especially for identifying the relationship between alleles. Diseases that are correlated with microsatellites are Fragile X Syndrome, Myotonic dystrophy, Friedreich ataxia, Kennedy disease, Huntington disease, Haw river syndrome, Polymorphisms have been discovered in multiple XPD exons
26.
Disease
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A disease is a particular abnormal condition, a disorder of a structure or function, that affects part or all of an organism. The study of disease is called pathology which includes the study of cause, Disease is often construed as a medical condition associated with specific symptoms and signs. When caused by pathogens, even in the literature, the term disease is often misleadingly used in the place of its causal agent. This language habitat can cause confusion in the communication of the principle in epidemiology. Diseases can affect not only physically, but also emotionally. Death due to disease is called death by natural causes, there are four main types of disease, infectious diseases, deficiency diseases, genetic diseases, and physiological diseases. Diseases can also be classified as communicable and non-communicable, the deadliest diseases in humans are coronary artery disease, followed by cerebrovascular disease and lower respiratory infections. In many cases, terms such as disease, disorder, morbidity, there are situations, however, when specific terms are considered preferable. Disease The term disease broadly refers to any condition that impairs the normal functioning of the body, for this reason, diseases are associated with dysfunctioning of the bodys normal homeostatic processes. The term disease has both a count sense and a noncount sense, by contrast, an infection that is asymptomatic during its incubation period, but expected to produce symptoms later, is usually considered a disease. Non-infectious diseases are all other diseases, including most forms of cancer, heart disease, acquired disease disease that began at some point during ones lifetime, as opposed to disease that was already present at birth, which is congenital disease. Acquired sounds like it could mean caught via contagion, but it simply means acquired sometime after birth and it also sounds like it could imply secondary disease, but acquired disease can be primary disease. It is often, genetic and can be inherited and it can also be the result of a vertically transmitted infection from the mother such as HIV/AIDS. Genetic disease disease that is caused by genetic mutation and it is often inherited, but some mutations are random and de novo. Hereditary or inherited disease a type of disease caused by mutation that is hereditary Iatrogenic disease A disease condition caused by medical intervention. Idiopathic disease disease whose cause is unknown, as medical science has advanced, many diseases whose causes were formerly complete mysteries have been somewhat explained or even extensively explained. Bacterial infections can be primary or secondary to a viral infection or burn. Terminal disease disease with death as an inevitable result Illness Illness is generally used as a synonym for disease, however, this term is occasionally used to refer specifically to the patients personal experience of his or her disease
27.
Mosquito
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Mosquitoes are small, midge-like flies that constitute the family Culicidae. Females of most species are ectoparasites, whose tube-like mouthparts pierce the skin to consume blood. The word mosquito is Spanish for little fly, thousands of species feed on the blood of various kinds of hosts, mainly vertebrates, including mammals, birds, reptiles, amphibians, and even some kinds of fish. Some mosquitoes also attack invertebrates, mainly other arthropods, though the loss of blood is seldom of any importance to the victim, the saliva of the mosquito often causes an irritating rash that is a serious nuisance. Much more serious though, are the roles of species of mosquitoes as vectors of diseases. The oldest known mosquito with a similar to modern species was found in 79-million-year-old Canadian amber from the Cretaceous. An older sister species with more primitive features was found in Burmese amber that is 90 to 100 million years old, two mosquito fossils have been found that show very little morphological change in modern mosquitoes against their counterpart from 46 million years ago. These fossils are also the oldest ever found to have blood preserved within their abdomens, the Old and New World Anopheles species are believed to have subsequently diverged about 95 million years ago. The mosquito Anopheles gambiae is currently undergoing speciation into the M and S molecular forms, consequently, some pesticides that work on the M form no longer work on the S form. Over 3,500 species of the Culicidae have already been described and they are generally divided into two subfamilies which in turn comprise some 43 genera. These figures are subject to change, as more species are discovered. The two main subfamilies are the Anophelinae and Culicinae, with their genera as shown in the subsection below, the distinction is of great practical importance because the two subfamilies tend to differ in their significance as vectors of different classes of diseases. Roughly speaking, arboviral diseases such as fever and dengue fever tend to be transmitted by Culicine species. Some transmit various species of malaria, but it is not clear that they ever transmit any form of human malaria. Some species do however transmit various forms of filariasis, much as many Simuliidae do, Anopheline mosquitoes, again not necessarily in the genus Anopheles, sometimes bear pathogenic arboviruses, but it is not yet clear that they ever transmit them as effective vectors. However, all the most important vectors of malaria are Anopheline. Anophelinae Culicinae Mosquitoes are members of a family of nematocerid flies, superficially, mosquitoes resemble crane flies and chironomid flies. In particular, the females of species of mosquitoes are blood-eating pests and dangerous vectors of diseases
28.
Trypanosoma brucei
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Trypanosoma brucei is a species of parasitic kinetoplastid belonging to the genus Trypanosoma. The parasite is the cause of a disease of vertebrate animals, including humans. In humans T. brucei causes African trypanosomiasis, or sleeping sickness, in animals it causes animal trypanosomiasis, also called nagana in cattle and horses. T. brucei has traditionally been grouped into three subspecies, T. b. brucei, T. b. gambiense and T. b. rhodesiense, the first is a parasite of non-human vertebrates, while the latter two are the known parasites of humans. Only rarely can the T. b. brucei infect a human, T. brucei is transmitted between mammal hosts by an insect vector belonging to different species of tsetse fly. Transmission occurs by biting during the blood meal. The parasites undergo complex morphological changes as they move between insect and mammal over the course of their life cycle, T. brucei is one of only a few pathogens known to cross the blood brain barrier. There is an urgent need for the development of new drug therapies, the parasite was discovered in 1894 by Sir David Bruce, after whom the scientific name was given in 1899. T. brucei comprises a complex that includes, T. brucei gambiense — Causes slow onset chronic trypanosomiasis in humans. Most common in central and western Africa, where humans are thought to be the primary reservoir, T. brucei rhodesiense — Causes fast onset acute trypanosomiasis in humans. Most common in southern and eastern Africa, where game animals, T. brucei brucei — Causes animal trypanosomiasis, along with several other species of Trypanosoma. T. b. brucei is not infective to humans due to its susceptibility to lysis by trypanosome lytic factor-1, however, it is closely related to, and shares fundamental features with the human-infective subspecies. T. brucei is a typical eukaryotic cell, and measures 8 to 50 μm in length. It has a body having a streamlined and tapered shape. Its cell membrane encloses the cell organelles, including the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, in addition, there is an unusual organelle called the kinetoplast, which is made up of numerous circular DNA and functions as a single large mitochondrion. The kinetoplast lies near the body with which it is indistinguishable under microscope. From the basal body arises a single flagellum that run towards the anterior end, along the body surface, the flagellum is attached to the cell membrane forming an undulating membrane. Only the tip of the flagellum is free at the anterior end and its kinetoplast and basal body lie anterior to the nucleus, with a long flagellum attached along the cell body
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Human
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Modern humans are the only extant members of Hominina tribe, a branch of the tribe Hominini belonging to the family of great apes. Several of these hominins used fire, occupied much of Eurasia and they began to exhibit evidence of behavioral modernity around 50,000 years ago. In several waves of migration, anatomically modern humans ventured out of Africa, the spread of humans and their large and increasing population has had a profound impact on large areas of the environment and millions of native species worldwide. Humans are uniquely adept at utilizing systems of communication for self-expression and the exchange of ideas. Humans create complex structures composed of many cooperating and competing groups, from families. Social interactions between humans have established a wide variety of values, social norms, and rituals. These human societies subsequently expanded in size, establishing various forms of government, religion, today the global human population is estimated by the United Nations to be near 7.5 billion. In common usage, the word generally refers to the only extant species of the genus Homo—anatomically and behaviorally modern Homo sapiens. In scientific terms, the meanings of hominid and hominin have changed during the recent decades with advances in the discovery, there is also a distinction between anatomically modern humans and Archaic Homo sapiens, the earliest fossil members of the species. The English adjective human is a Middle English loanword from Old French humain, ultimately from Latin hūmānus, the words use as a noun dates to the 16th century. The native English term man can refer to the species generally, the species binomial Homo sapiens was coined by Carl Linnaeus in his 18th century work Systema Naturae. The generic name Homo is a learned 18th century derivation from Latin homō man, the species-name sapiens means wise or sapient. Note that the Latin word homo refers to humans of either gender, the genus Homo evolved and diverged from other hominins in Africa, after the human clade split from the chimpanzee lineage of the hominids branch of the primates. The closest living relatives of humans are chimpanzees and gorillas, with the sequencing of both the human and chimpanzee genome, current estimates of similarity between human and chimpanzee DNA sequences range between 95% and 99%. The gibbons and orangutans were the first groups to split from the leading to the humans. The splitting date between human and chimpanzee lineages is placed around 4–8 million years ago during the late Miocene epoch, during this split, chromosome 2 was formed from two other chromosomes, leaving humans with only 23 pairs of chromosomes, compared to 24 for the other apes. There is little evidence for the divergence of the gorilla, chimpanzee. Each of these species has been argued to be an ancestor of later hominins
30.
Tsetse fly
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Tsetse, sometimes spelled tzetze and also known as tik-tik flies, are large biting flies that inhabit much of tropical Africa. Tsetse flies include all the species in the genus Glossina, which are placed in their own family, the tsetse are obligate parasites that live by feeding on the blood of vertebrate animals. They are economically important in sub-Saharan Africa as the vectors of trypanosomes. Tsetse have been studied because of their disease transmission. These flies are multivoltine, typically producing about four generations yearly, Tsetse are similar to other large flies, such as the housefly, but can be distinguished by various characteristics of their anatomy, two of which are easy to observe. Tsetse fold their wings completely when they are resting so that one wing rests directly on top of the other over their abdomens, Tsetse also have a long proboscis, which extends directly forward and is attached by a distinct bulb to the bottom of their heads. Fossilized tsetse have been recovered from the Florissant Fossil Beds in Colorado, twenty-three extant species of tsetse flies are known from Africa. The word tsetse means fly in Tswana, a Bantu language of southern Africa, recently, tsetse without the fly has become more common in English, particularly in the scientific and development communities. The word is pronounced tseh-tseh in the Sotho languages and is rendered in other African languages. During World War II, a de Havilland antisubmarine aircraft was known as the Tsetse Mosquito, the biology of tsetse is relatively well understood by Entomologists. Tsetse flies can be seen as independent individuals in two forms, as larvae, and as adults. Tsetse first become separate from their mothers during the third larval instar, however, this life stage is short, lasting at most a few hours, and is almost never observed outside of the laboratory. Tsetse next develop an external case, the puparium, and become pupae—small, hard-shelled. Tsetse pupae are under 1.0 cm long, within the puparial shell, tsetse complete the last two larval instars and the pupal stage. At the end of the stage, tsetse emerge as adult flies. The adults are large flies, with lengths of 0. 5-1.5 cm. Tsetse have large heads, distinctly separated eyes, and unusual antennae, the thorax is quite large, while the abdomen is wide rather than elongated and shorter than the wings. The head has large eyes, distinctly separated on each side, the thorax is large, made of three fused segments
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Cestoda
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Cestoda is a class of parasitic flatworms of the phylum Platyhelminthes. Biologists informally refer to them as cestodes, the best-known species are commonly called tapeworms. All cestodes are parasitic and their life histories vary, but typically they live in the tracts of vertebrates as adults. Over a thousand species have been described, and all species may be parasitised by at least one species of tapeworm. Humans are subject to infection by several species of tapeworms if they eat undercooked meat such as pork, beef, and fish, or if they live in, or eat food prepared in, conditions of poor hygiene. T. saginata, the tapeworm, can grow up to 20 m, the largest species. Species using small vertebrates as hosts, though, tend to be small, for example, vole and lemming tapeworms are only 13–240 mm in length, and those parasitizing shrews only 0. 8–60 mm. The worms scolex attaches to the intestine of the definitive host, in some species, the scolex is dominated by bothria, or sucking grooves that function like suction cups. Other species have hooks and suckers that aid in attachment, cyclophyllid cestodes can be identified by the presence of four suckers on their scolices. While the scolex is often the most distinctive part of a tapeworm, it is often unnoticed in a clinical setting. Therefore, identifying eggs and proglottids in feces is the simplest way to diagnose an infection, the main nerve centre of a cestode is a cerebral ganglion in its scolex. Motor and sensory innervation depends on the number of nerves in, smaller nerves emanate from the ganglion to supply the general body muscular and sensory ending. The cirrus and vagina are innervated, and sensory endings around the genital pore are more plentiful than other areas, sensory function includes both tactoreception and chemoreception. The body is composed of segments called proglottids. The sum of the proglottids is called a strobila, which is thin, from this is derived the common name tapeworm. Proglottids are continually produced by the region of the scolex, as long as the scolex is attached. Like some other flatworms, cestodes use flame cells, located in the proglottids, mature proglottids are released from the tapeworms end segment and leave the host in feces or migrate as independent motile proglottids. The proglottids farthest away from the scolex are the ones containing eggs
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Flatworm
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The flatworms, flat worms, Platyhelminthes, Plathelminthes, or platyhelminths are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates. The digestive cavity has one opening for both ingestion and egestion, as a result, the food cannot be processed continuously. Free-living flatworms are mostly predators, and live in water or in shaded, humid terrestrial environments, cestodes and trematodes have complex life-cycles, with mature stages that live as parasites in the digestive systems of fish or land vertebrates, and intermediate stages that infest secondary hosts. Unlike the other groups, the monogeneans are external parasites infesting aquatic animals. Because they do not have internal body cavities, Platyhelminthes were regarded as a stage in the evolution of bilaterians. However, analyses since the mid-1980s have separated out one subgroup, the remaining Platyhelminthes form a monophyletic group, one that contains all and only descendants of a common ancestor that is itself a member of the group. The redefined Platyhelminthes is part of the Lophotrochozoa, one of the three groups of more complex bilaterians. Hence, the traditional platyhelminth subgroup Turbellaria is now regarded as paraphyletic, since it excludes the wholly parasitic groups, over half of all known flatworm species are parasitic, and some do enormous harm to humans and their livestock. Schistosomiasis, caused by one genus of trematodes, is the second-most devastating of all diseases caused by parasites. Neurocysticercosis, which arises when larvae of the pork tapeworm Taenia solium penetrate the central system, is the major cause of acquired epilepsy worldwide. The threat of parasites to humans in developed countries is rising because of the popularity of raw or lightly cooked foods. However, there is now concern that these planarians may themselves become a threat to native snails. In northwest Europe, there are concerns about the spread of the New Zealand planarian Arthurdendyus triangulatus, like other bilaterians, they have three main cell layers, while the radially symmetrical cnidarians and ctenophores 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 flatworms anatomy and their bodies are soft and unsegmented. The lack of circulatory and respiratory organs limits platyhelminths to sizes and shapes that enable oxygen to reach, hence, many are microscopic and the large species have flat ribbon-like or leaf-like shapes. The guts of large species have many branches, allowing nutrients to diffuse to all parts of the body, the mesenchyme contains all the internal organs and allows the passage of oxygen, nutrients and waste products. Most platyhelminths have no anus and regurgitate undigested material through the mouth, however, some long species have an anus and some with complex, branched guts have more than one anus, since excretion only through the mouth would be difficult for them
33.
Life cycle (biology)
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In biology, a biological life cycle is a series of changes in form that an organism undergoes, returning to the starting state. The concept is related to those of the life history, development and ontogeny. Transitions of form may involve growth, asexual reproduction, and/or sexual reproduction, in some organisms, different generations of the species succeed each other during the life cycle. For plants and many algae, there are two stages, and the life cycle is referred to as alternation of generations. The term life history is used, particularly for organisms such as the red algae which have three multicellular stages, rather than two. Life cycles that include sexual reproduction involve alternating haploid and diploid stages, to return from a diploid stage to a haploid stage, meiosis must occur. In regard to changes of ploidy, there are 3 types of cycles, haplontic life cycle — the haploid stage is multicellular, diplontic life cycle — the diploid stage is multicellular and haploid gametes are formed, meiosis is gametic. Haplodiplontic life cycle — multicellular diploid and haploid stages occur, meiosis is sporic, the cycles differ in when mitosis occurs. Zygotic meiosis and gametic meiosis have one stage, mitosis occurs during the n phase in zygotic meiosis. Therefore, zygotic and gametic meiosis are collectively termed haplobiontic, sporic meiosis, on the other hand, has mitosis in two stages, both the diploid and haploid stages, termed diplobiontic. The study of reproduction and development in organisms was carried out by botanists and zoologists. Wilhelm Hofmeister demonstrated that alternation of generations is a feature that unites plants, some terms used for the description of life cycles were proposed initially for algae by Nils Svedelius, and then became used for other organisms. Other terms used in protist life cycles were introduced by Karl Gottlieb Grell, the description of the complex life cycles of various organisms contributed to the disproof of the ideas of spontaneous generation in the 1840s and 1850s. A zygotic meiosis is a meiosis of a zygote immediately after karyogamy and this way, the organism ends its diploid phase and produces several haploid cells. These cells divide mitotically to form larger, multicellular individuals. Two opposite types of gametes from these individuals or cells fuse to become a zygote, in the whole cycle, zygotes are the only diploid cell, mitosis occurs only in the haploid phase. The individuals or cells as a result of mitosis are haplonts, haplonts are, In archaeplastidans, some green algae In stramenopiles, some golden algae In alveolates, many dinoflagellates eg. Cells from the individuals then undergo meiosis to produce haploid cells or gametes
34.
Sludge worm
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Tubifex tubifex, also called the sludge worm, or sewage worm, is a species of tubificid segmented worm that inhabits the sediments of lakes and rivers on several continents. These worms ingest sediments, selectively digest bacteria, and absorb molecules through their body walls and they can also survive in areas heavily polluted with organic matter that almost no other species can endure. By forming a protective cyst and lowering its rate, T. tubifex can survive drought. Encystment may also function in the dispersal of the worm and they usually inhabit the bottom sediments of lakes, rivers, and occasionally sewer lines and outlets
35.
Salmonidae
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Salmonidae is a family of ray-finned fish, the only living family currently placed in the order Salmoniformes. It includes salmon, trout, chars, freshwater whitefishes, and graylings, the Atlantic salmon and trout of the genus Salmo give the family and order their names. Salmonids have a primitive appearance among the teleost fish, with the pelvic fins being placed far back. They are slender fish, with rounded scales and forked tails and their mouths contain a single row of sharp teeth. Although the smallest species is just 13 cm long as an adult, most are much larger, all salmonids spawn in fresh water, but in many cases, the fish spend most of their lives at sea, returning to the rivers only to reproduce. This lifecycle is described as anadromous and they are predators, feeding on small crustaceans, aquatic insects, and smaller fish. Current salmonids comprise three lineages, taxonomically treated as subfamilies, whitefish, graylings, and the char, trout, generally, all three lineages are accepted to allocate a suite of derived traits indicating a monophyletic group. This genus shares traits found in the Salmoninae, whitefish, hence, E. driftwoodensis is an archaic salmonid, representing an important stage in salmonid evolution. A gap appears in the fossil record after E. driftwoodensis until about seven million years ago, in the late Miocene. Several of these appear to be Oncorhynchus—the current genus for Pacific salmon. Consequently, the split between Oncorhynchus and Salmo must have occurred well before the Pliocene, suggestions have gone back as far as the early Miocene. Based on the most current evidence, salmonids diverged from the rest of teleost fish no later than 88 million years ago and this divergence was marked by a whole-genome duplication event in the ancestral salmonid, where the diploid ancestor became tetraploid. Extant salmonids all show evidence of partial tetraploidy, as show the genome has undergone selection to regain a diploid state. Work done in the trout has shown that the genome is still partially-tetraploid. This pattern of partial tetraploidy is thought to be reflected in the rest of extant salmonids, the first fossil species representing a true salmonid fish does not appear until the middle Eocene. This fossil is also younger than the proposed salmonid divergence from the rest of the teleost fishes. This means that the salmonids have a ghost lineage of approximately 33 million years and this more precise dating and examination of the salmonid whole-genome duplication event has allowed more speculation on the radiation of species within the group. Historically, the duplication event was thought to be the reason for the variation within Salmonidae
36.
Myxobolus cerebralis
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Myxobolus cerebralis is a myxosporean parasite of salmonids that causes whirling disease in farmed salmon and trout and also in wild fish populations. It was first described in rainbow trout in Germany a century ago, but its range has spread and it has appeared in most of Europe, in the 1980s, M. cerebralis was found to require a tubificid oligochaete to complete its life cycle. The parasite infects its hosts with its cells after piercing them with polar filaments ejected from nematocyst-like capsules, Whirling disease afflicts juvenile fish and causes skeletal deformation and neurological damage. Fish whirl forward in an awkward, corkscrew-like pattern instead of swimming normally, find feeding difficult, the mortality rate is high for fingerlings, up to 90% of infected populations, and those that do survive are deformed by the parasites residing in their cartilage and bone. They act as a reservoir for the parasite, which is released into water following the fishs death, M. cerebralis is one of the most economically important myxozoans in fish, as well as one of the most pathogenic. It was the first myxosporean whose pathology and symptoms were described scientifically, the parasite is not transmissible to humans. The taxonomy and naming of both M. cerebralis, and of myxozoans in general, have complicated histories and it was originally thought to infect fish brains and nervous systems, though it soon was found to primarily infect cartilage and skeletal tissue. Attempts to change the name to Myxobolus chondrophagus, which would more accurately describe the organism, similarly, other actinosporeans were folded into the life cycles of various myxosporeans. Today, the myxozoans, previously thought to be protozoans, are considered animals by most scientists. Recent molecular studies suggest they are related to Bilateria or Cnidaria, M. cerebralis has many diverse stages ranging from single cells to relatively large spores, not all of which have been studied in detail. The stages that infect fish, called triactinomyxon spores, are made of a style that is about 150 micrometers long. A sporoplasm packet at the end of the style contains 64 germ cells surrounded by a cellular envelope, there are also three polar capsules, each of which contains a coiled polar filament between 170 and 180 µm long. Polar filaments in both stage and in the myxospore stage rapidly shoot into the body of the host. Upon contact with fish hosts and firing of the polar capsules, firstly, this sporoplasm undergoes mitosis to produce more amoeboid cells, which migrate into deeper tissue layers, to reach the cerebral cartilage. Myxospores, which develop from sporogonic cell stages inside fish hosts, are lenticular and they have a diameter of about 10 micrometers and are made of six cells. Two of these cells form polar capsules, two merge to form a binucleate sporoplasm, and two form protective valves, myxospores are infective to oligochaetes, and are found among the remains of digested fish cartilage. They are often difficult to distinguish from related species because of morphological similarities across genera, though M. cerebralis is the only myxosporean ever found in salmonid cartilage, other visually similar species may be present in the skin, nervous system, or muscle. Myxobolus cerebralis has a two-host life cycle involving a salmonid fish, so far, the only worm known to be susceptible to M. cerebralis infection is Tubifex tubifex, though what scientists currently call T. tubifex may in fact be more than one species
37.
Biological life cycle
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In biology, a biological life cycle is a series of changes in form that an organism undergoes, returning to the starting state. The concept is related to those of the life history, development and ontogeny. Transitions of form may involve growth, asexual reproduction, and/or sexual reproduction, in some organisms, different generations of the species succeed each other during the life cycle. For plants and many algae, there are two stages, and the life cycle is referred to as alternation of generations. The term life history is used, particularly for organisms such as the red algae which have three multicellular stages, rather than two. Life cycles that include sexual reproduction involve alternating haploid and diploid stages, to return from a diploid stage to a haploid stage, meiosis must occur. In regard to changes of ploidy, there are 3 types of cycles, haplontic life cycle — the haploid stage is multicellular, diplontic life cycle — the diploid stage is multicellular and haploid gametes are formed, meiosis is gametic. Haplodiplontic life cycle — multicellular diploid and haploid stages occur, meiosis is sporic, the cycles differ in when mitosis occurs. Zygotic meiosis and gametic meiosis have one stage, mitosis occurs during the n phase in zygotic meiosis. Therefore, zygotic and gametic meiosis are collectively termed haplobiontic, sporic meiosis, on the other hand, has mitosis in two stages, both the diploid and haploid stages, termed diplobiontic. The study of reproduction and development in organisms was carried out by botanists and zoologists. Wilhelm Hofmeister demonstrated that alternation of generations is a feature that unites plants, some terms used for the description of life cycles were proposed initially for algae by Nils Svedelius, and then became used for other organisms. Other terms used in protist life cycles were introduced by Karl Gottlieb Grell, the description of the complex life cycles of various organisms contributed to the disproof of the ideas of spontaneous generation in the 1840s and 1850s. A zygotic meiosis is a meiosis of a zygote immediately after karyogamy and this way, the organism ends its diploid phase and produces several haploid cells. These cells divide mitotically to form larger, multicellular individuals. Two opposite types of gametes from these individuals or cells fuse to become a zygote, in the whole cycle, zygotes are the only diploid cell, mitosis occurs only in the haploid phase. The individuals or cells as a result of mitosis are haplonts, haplonts are, In archaeplastidans, some green algae In stramenopiles, some golden algae In alveolates, many dinoflagellates eg. Cells from the individuals then undergo meiosis to produce haploid cells or gametes
38.
Trematode life cycle stages
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Trematodes or flukes are small parasitic flatworms that use vertebrates as their definitive host, and molluscs as their intermediate host. To accomplish this, they have varied life cycle stages. The life cycle of a typical digenean trematode can be thought to begin when its egg is immersed in water, following this, a miracidium hatches, which swims to find a mollusc host. The miracidia go through stages in the mollusc host, eventually emerging as motile cercarial larvae. The cercaria either infects vertebrates through the skin or is ingested, in its vertebrate host, the cercaria matures to an adult form, the fluke, and lays eggs that are discharged with the host feces or urine. In the presence of water, the eggs hatch and the miracidium stage of life is reached again. Sporocyst – an elongated sac, it produces either rediae or more sporocysts, redia – a larval form with an oral sucker, it will produce either more rediae, or cercariae. Cercaria – the larval form of the parasite, it develops within the cells of the sporocyst or redia. A cercaria has a head with large penetration glands. It may or may not have a long swimming tail, depending on the species, the motile cercaria finds and settles in a host where it will become either an adult, or a mesocercaria, or a metacercaria, according to species. Mesocercaria – a cercaria little modified but resting Metacercaria – a cercaria encysted and resting Adult – the fully developed mature stage, not all trematodes follow the typical sequence of eggs, miracidia, sporocysts, rediae, cercariae, and adults. In some species, the stage is omitted, and sporocysts produce cercariae. In some species, the cercaria develops into an adult within the same host, many digenean trematodes require two hosts, one where asexual reproduction occurs in sporocysts, the other a vertebrate where the adult form engages in sexual reproduction to produce eggs. In some species the cercaria encysts, and waits until the host is eaten by a third host, in whose gut it emerges, most trematodes are hermaphroditic, but members of the family Schistosomatidae are dioecious. Males are shorter and stouter than the females, bucephalus polymorphus Trematode infection Apicomplexa lifecycle stages Life cycle of Schistosoma mansoni
39.
Tadpole
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A tadpole is the larval stage in the life cycle of an amphibian, particularly that of a frog or toad. They are usually wholly aquatic, though some species have tadpoles that are terrestrial, when first hatched from the egg they have a more or less globular body, a laterally compressed tail and internal or external gills. As they grow they undergo metamorphosis, during which process they grow limbs, develop lungs, most tadpoles are herbivorous and during metamorphosis the mouth and internal organs are rearranged to prepare for an adult carnivorous lifestyle. Having no hard parts, it might be expected that fossil tadpoles would not exist, however, traces of biofilms have been preserved and fossil tadpoles have been found dating back to the Miocene. Tadpoles are eaten in parts of the world and are mentioned in folk tales. The name tadpole is from Middle English taddepol, made up of the elements tadde, toad, similarly, pollywog / polliwog is from Middle English polwygle, made up of the same pol, head, and wiglen, to wiggle. Tadpoles are young amphibians that live in the water, though a few tadpoles are semi-terrestrial and terrestrial. During the tadpole stage of the life cycle, most respire by means of autonomous external or internal gills. They do not usually have arms or legs until the transition to adulthood, as a tadpole matures, it most commonly metamorphosizes by gradually growing limbs and then outwardly absorbing its tail by apoptosis. Lungs develop around the time of leg development, and tadpoles late in development will often be found near the surface of the water, where they breathe air. During the final stages of external metamorphosis, the mouth changes from a small. The intestines shorten to accommodate the new diet, most tadpoles are herbivorous, subsisting on algae and plants. Some species are omnivorous, eating detritus and, when available, tadpoles vary greatly in size, both during their development and between species. For example, in a family, Megophryidae, length of late-stage tadpoles varies between 33 millimetres and 106 millimetres. The tadpoles of Pseudis paradoxa grow to 25 centimetres, the largest of any frog, despite their soft-bodied nature and lack of mineralised hard parts, fossil tadpoles have been recovered from Upper Miocene strata. They are preserved by virtue of biofilms, with more robust structures preserved as a carbon film, in Miocene fossils from Libros, Spain, the brain case is preserved in calcium carbonate, and the nerve cord in calcium phosphate. Other parts of the tadpoles bodies exist as organic remains and bacterial biofilms, tadpole remains with telltale external gills are also known from several of the Labyrinthodont groups. Some tadpoles are used as food, tadpoles of megophryid frog Oreolalax rhodostigmatus are particularly large, more than 10 cm in length, and are collected for human consumption in China
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. PMID 24229807.