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Protozoans
Protozoa (: protozoan or protozoon; alternative plural: protozoans) are a polyphyletic group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic debris. Historically, protozoans were regarded as "one-celled animals". When first introduced by Georg Goldfuss, in 1818, the taxon Protozoa was erected as a class within the Animalia, with the word 'protozoa' meaning "first animals", because they often possess animal-like behaviours, such as motility and predation, and lack a cell wall, as found in plants and many algae. This classification remained widespread in the 19th and early 20th century, and even became elevated to a variety of higher ranks, including phylum, subkingdom, kingdom, and then sometimes included within the paraphyletic Protoctista or Protista. By the 1970s, it became usual to require that all taxa be monophyletic (derived from a common ancestor that would also be regarded as protozo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parasitism
Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson characterised parasites' way of feeding as "predators that eat prey in units of less than one". Parasites include single-celled protozoans such as the agents of malaria, sleeping sickness, and amoebic dysentery; animals such as hookworms, lice, mosquitoes, and vampire bats; fungi such as honey fungus and the agents of ringworm; and plants such as mistletoe, dodder, and the broomrapes. There are six major parasitic strategies of exploitation of animal hosts, namely parasitic castration, directly transmitted parasitism (by contact), trophicallytransmitted parasitism (by being eaten), vector-transmitted parasitism, parasitoidism, and micropredation. One major axis of classification concerns invasiveness: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protist
A protist ( ) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural group, or clade, but are a paraphyletic grouping of all descendants of the last eukaryotic common ancestor excluding land plants, animals, and fungi. Protists were historically regarded as a separate taxonomic kingdom known as Protista or Protoctista. With the advent of phylogenetic analysis and electron microscopy studies, the use of Protista as a formal taxon was gradually abandoned. In modern classifications, protists are spread across several eukaryotic clades called supergroups, such as Archaeplastida ( photoautotrophs that includes land plants), SAR, Obazoa (which includes fungi and animals), Amoebozoa and " Excavata". Protists represent an extremely large genetic and ecological diversity in all environments, including extreme habitats. Their diversity, larger than for all other eukaryotes, has only been discovered in rece ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unicellular Organism
A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and eukaryotic organisms. Most prokaryotes are unicellular and are classified into bacteria and archaea. Many eukaryotes are multicellular, but some are unicellular such as protozoa, unicellular algae, and unicellular fungi. Unicellular organisms are thought to be the oldest form of life, with early organisms emerging 3.5–3.8 billion years ago. Although some prokaryotes live in colonies, they are not specialised cells with differing functions. These organisms live together, and each cell must carry out all life processes to survive. In contrast, even the simplest multicellular organisms have cells that depend on each other to survive. Most multicellular organisms have a unicellular life-cycle stage. Gametes, for example, are reprodu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rotifer
The rotifers (, from Latin 'wheel' and 'bearing'), sometimes called wheel animals or wheel animalcules, make up a phylum (Rotifera ) of microscopic and near-microscopic Coelom#Pseudocoelomates, pseudocoelomate animals. They were first described by John Harris (writer), Rev. John Harris in 1696, and other forms were described by Antonie van Leeuwenhoek in 1703. Most rotifers are around long (although their size can range from to over ), and are common in freshwater environments throughout the world with a few Seawater, saltwater species. Some rotifers are free swimming and truly planktonic, others move by inchworming along a substrate, and some are Sessility (zoology), sessile, living inside tubes or gelatinous holdfast (biology), holdfasts that are attached to a substrate. About 25 species are colonial (e.g., ''Sinantherina semibullata''), either sessile or planktonic. Rotifers are an important part of the freshwater zooplankton, being a major foodsource and with many specie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eukaryote
The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms are eukaryotes. They constitute a major group of Outline of life forms, life forms alongside the two groups of prokaryotes: the Bacteria and the Archaea. Eukaryotes represent a small minority of the number of organisms, but given their generally much larger size, their collective global biomass is much larger than that of prokaryotes. The eukaryotes emerged within the archaeal Kingdom (biology), kingdom Asgard (Archaea), Promethearchaeati and its sole phylum Promethearchaeota. This implies that there are only Two-domain system, two domains of life, Bacteria and Archaea, with eukaryotes incorporated among the Archaea. Eukaryotes first emerged during the Paleoproterozoic, likely as Flagellated cell, flagellated cells. The leading evolutiona ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sponge
Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a basal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and are one of the most ancient members of macrobenthos, with many historical species being important reef-building organisms. Sponges are multicellular organisms consisting of jelly-like mesohyl sandwiched between two thin layers of cells, and usually have tube-like bodies full of pores and channels that allow water to circulate through them. They have unspecialized cells that can transform into other types and that often migrate between the main cell layers and the mesohyl in the process. They do not have complex nervous, digestive or circulatory systems. Instead, most rely on maintaining a constant water flow through their bodies to obtain food and oxygen and to remove wastes, usually via flagella movements of the so-called " collar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coral
Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria. They typically form compact Colony (biology), colonies of many identical individual polyp (zoology), polyps. Coral species include the important Coral reef, reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton. A coral "group" is a colony of very many cloning, genetically identical polyps. Each polyp is a sac-like animal typically only a few millimeters in diameter and a few centimeters in height. A set of tentacles surround a central mouth opening. Each polyp excretes an exoskeleton near the base. Over many generations, the colony thus creates a skeleton characteristic of the species which can measure up to several meters in size. Individual colonies grow by asexual reproduction of polyps. Corals also breed sexually by spawning: polyps of the same species release gametes simultaneously overnight, often around a full moon. Fertilized eggs form ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multicellular Organism
A multicellular organism is an organism that consists of more than one cell (biology), cell, unlike unicellular organisms. All species of animals, Embryophyte, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- and partially multicellular, like slime molds and social Amoeba, amoebae such as the genus ''Dictyostelium''. Multicellular organisms arise in various ways, for example by cell division or by aggregation of many single cells. Colonial organisms are the result of many identical individuals joining together to form a colony (biology), colony. However, it can often be hard to separate colonial protists from true multicellular organisms, because the two concepts are not distinct; colonial protists have been dubbed "pluricellular" rather than "multicellular". There are also macroscopic organisms that are multinucleate though technically unicellular, such as the Xenophyophorea that can reach 20 cm. Evolutionary history ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zoologist
Zoology ( , ) is the scientific study of animals. Its studies include the structure, embryology, classification, habits, and distribution of all animals, both living and extinct, and how they interact with their ecosystems. Zoology is one of the primary branches of biology. The term is derived from Ancient Greek , ('animal'), and , ('knowledge', 'study'). Although humans have always been interested in the natural history of the animals they saw around them, and used this knowledge to domesticate certain species, the formal study of zoology can be said to have originated with Aristotle. He viewed animals as living organisms, studied their structure and development, and considered their adaptations to their surroundings and the function of their parts. Modern zoology has its origins during the Renaissance and early modern period, with Carl Linnaeus, Antonie van Leeuwenhoek, Robert Hooke, Charles Darwin, Gregor Mendel and many others. The study of animals has largely mov ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Georg August Goldfuss Protozoa Infusoria Monades
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Trypanosoma
''Trypanosoma'' is a genus of kinetoplastids (class Trypanosomatidae), a monophyletic group of unicellular parasitic flagellate protozoa. Trypanosoma is part of the phylum Euglenozoa. The name is derived from the Ancient Greek ''trypano-'' (borer) and ''soma'' (body) because of their corkscrew-like motion. Most trypanosomes are heteroxenous (requiring more than one obligatory host to complete life cycle) and most are transmitted via a vector. The majority of species are transmitted by blood-feeding invertebrates, but there are different mechanisms among the varying species. '' Trypanosoma equiperdum'' is spread between horses and other equine species by sexual contact. They are generally found in the intestine of their invertebrate host, but normally occupy the bloodstream or an intracellular environment in the vertebrate host. Trypanosomes infect a variety of hosts and cause various diseases, including the fatal human diseases sleeping sickness, caused by '' Trypanosoma br ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
