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Gonozooid
In biology, Gonozooids are any of the reproductive individuals of Tunicates, Bryozoan, or Hydrozoan colonies that produce gametes. Gonozooids may play a role in labour division or in alternation of generations. A gonozooid typically has hardly any other function than reproduction, amounting to little more than a motile gonad. The production of gonozooids amounts to one aspect of certain classes of alternation of generations. In biological terms the various forms are examples of evolutionary strategies and are largely analogous rather than homologous; the gonozooid phases of say, the Tunicata did not evolve from anything like say, a Bryozoan. Examples of species with gonozooids ''Hydractinia symbiolongicarpus'' Polyps from the Cnidaria ''Hydractinia symbiolongicarpus'' form colonies where labour is divided between reproduction (gonozooids), feeding (gastrozooids) and defense (dactylozooid). Even though they are genetically identical, there is a distinct morphological dif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bryozoa
Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a lophophore, a "crown" of tentacles used for filter feeding. Most marine bryozoans live in tropical waters, but a few are found in oceanic trenches and polar waters. The bryozoans are classified as the marine bryozoans (Stenolaemata), freshwater bryozoans (Phylactolaemata), and mostly-marine bryozoans (Gymnolaemata), a few members of which prefer brackish water. 5,869living species are known. At least two genera are solitary (''Aethozooides'' and ''Monobryozoon''); the rest are colonial. The terms Polyzoa and Bryozoa were introduced in 1830 and 1831, respectively. Soon after it was named, another group of animals was discovered whose filtering mechanism looked similar, so it was included in Bryozoa until 1869, when the two groups were no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tunicate
A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata (). It is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates). The subphylum was at one time called Urochordata, and the term urochordates is still sometimes used for these animals. They are the only chordates that have lost their myomeric segmentation, with the possible exception of the 'seriation of the gill slits'. Some tunicates live as solitary individuals, but others replicate by budding and become colonies, each unit being known as a zooid. They are marine filter feeders with a water-filled, sac-like body structure and two tubular openings, known as siphons, through which they draw in and expel water. During their respiration and feeding, they take in water through the incurrent (or inhalant) siphon and expel the filtered water through the excurrent (or exhalant) siphon. Most adult tunicates are sessile, immobile and perman ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrozoa
Hydrozoa (hydrozoans; ) are a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial species can be large, and in some cases the specialized individual animals cannot survive outside the colony. A few genera within this class live in freshwater habitats. Hydrozoans are related to jellyfish and corals and belong to the phylum Cnidaria. Some examples of hydrozoans are the freshwater jelly (''Craspedacusta sowerbyi''), freshwater polyps ('' Hydra''), ''Obelia'', Portuguese man o' war (''Physalia physalis''), chondrophores (Porpitidae), "air fern" (''Sertularia argentea''), and pink-hearted hydroids (''Tubularia''). Anatomy Most hydrozoan species include both a polyp (zoology), polypoid and a medusa (biology), medusoid stage in their lifecycles, although a number of them have only one or the other. For example, ''Hydra'' has no medusoid stage, while ''Liriope tetraphylla, Lir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetic Variance
Genetic variance is a concept outlined by the England, English biologist and statistics, statistician Ronald Fisher in his Fisher's fundamental theorem of natural selection, fundamental theorem of natural selection. In his 1930 book ''The Genetical Theory of Natural Selection'', Fisher postulates that the rate of change of fitness (biology), biological fitness can be calculated by the genetic variance of the fitness itself. Fisher tried to give a statistical formula about how the change of fitness in a population can be attributed to changes in the allele frequency. Fisher made no restrictive assumptions in his formula concerning fitness parameters, mate choices or the number of alleles and locus (genetics), loci involved. Definition Phenotypic variance, usually combines the genotype variance with the environmental variance. Genetic variance has three major components: the additive genetic variance, dominance variance, and epistatic variance. Additive genetic variance involves ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metamorphosis
Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some insects, fish, amphibians, mollusks, crustaceans, cnidarians, echinoderms, and tunicates undergo metamorphosis, which is often accompanied by a change of nutrition source or behavior. Animals can be divided into species that undergo complete metamorphosis (" holometaboly"), incomplete metamorphosis ("hemimetaboly"), or no metamorphosis (" ametaboly"). Scientific usage of the term is technically precise, and it is not applied to general aspects of cell growth, including rapid growth spurts. Generally organisms with a larva stage undergo metamorphosis, and during metamorphosis the organism loses larval characteristics. References to "metamorphosis" in mammals are imprecise and only colloquial, but historically idealist ideas of transformation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sterility (physiology)
Sterility is the physiological inability to effect sexual reproduction in a living thing, members of whose kind have been produced sexually. Sterility has a wide range of causes. It may be an inherited trait, as in the mule; or it may be acquired from the environment, for example through physical injury or disease, or by exposure to radiation. Sterility is the inability to produce a biological child, while infertility is the inability to conceive after a certain period. Sterility is rarely discussed in clinical literature and is often used synonymously with infertility. Infertility affects about 12-15% of couples globally. Still, the prevalence of sterility remains unknown. Sterility can be divided into three subtypes natural, clinical, and hardship. Natural sterility is the couple’s physiological inability to conceive a child naturally. Clinical sterility is natural sterility for which treatment of the patient will not result in conception. Hardship sterility is the inability to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Celleporella Hyalina
''Celleporella hyalina'' is a species of bryozoans belonging to the family Hippothoidae. It has almost cosmopolitan distribution In biogeography, cosmopolitan distribution is the term for the range of a taxon that extends across all or most of the world in appropriate habitats. Such a taxon, usually a species, is said to exhibit cosmopolitanism or cosmopolitism. The ext .... The species has numerous subspecies, eg: * ''Celleporella hyalina'' subsp. ''hyalina'' * ''Celleporella hyalina'' subsp. ''marcusi'' (Morris, 1980) References {{Taxonbar, from=Q6402965 Bryozoans ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Budding
Budding or blastogenesis is a type of asexual reproduction in which a new organism develops from an outgrowth or bud due to cell division at one particular site. For example, the small bulb-like projection coming out from the yeast cell is known as a bud. Since the reproduction is asexual, the newly created organism is a clone and excepting mutations is genetically identical to the parent organism. Organisms such as hydra use regenerative cells for reproduction in the process of budding. In hydra, a bud develops as an outgrowth due to repeated cell division at one specific site. These buds develop into tiny individuals and, when fully mature, detach from the parent body and become new independent individuals. Internal budding or endodyogeny is a process of asexual reproduction, favored by parasites such as ''Toxoplasma gondii''. It involves an unusual process in which two daughter cells are produced inside a mother cell, which is then consumed by the offspring prior to their s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asexual Reproduction
Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the full set of genes of their single parent and thus the newly created individual is genetically and physically similar to the parent or an exact clone of the parent. Asexual reproduction is the primary form of reproduction for single-celled organisms such as archaea and eubacteria, bacteria. Many Eukaryote, eukaryotic organisms including plants, animals, and Fungus, fungi can also reproduce asexually. In vertebrates, the most common form of asexual reproduction is parthenogenesis, which is typically used as an alternative to sexual reproduction in times when reproductive opportunities are limited. Komodo dragons and some monitor lizards can also reproduce asexually. While all prokaryotes reproduce without the formation and fusion of gametes, m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Egg Cell
The egg cell, or ovum (plural ova), is the female reproductive cell, or gamete, in most anisogamous organisms (organisms that reproduce sexually with a larger, female gamete and a smaller, male one). The term is used when the female gamete is not capable of movement (non-motile). If the male gamete (sperm) is capable of movement, the type of sexual reproduction is also classified as oogamous. A nonmotile female gamete formed in the oogonium of some algae, fungi, oomycetes, or bryophytes is an oosphere. When fertilized the oosphere becomes the oospore. When egg and sperm fuse during fertilisation, a diploid cell (the zygote) is formed, which rapidly grows into a new organism. History While the non-mammalian animal egg was obvious, the doctrine ''ex ovo omne vivum'' ("every living nimal comes froman egg"), associated with William Harvey (1578–1657), was a rejection of spontaneous generation and preformationism as well as a bold assumption that mammals also reproduced via ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Doliolum Nationalis
''Doliolum'' is a genus of tunicates, the members of which move via jet propulsion. A detailed description can be found at . Species The World Register of Marine Species lists the following species: World Register of Marine Species. Retrieved 2011-11-17. *'''' Quoy & Gaimard, 1834 *'''' Neumann, 1906 *'' |
Hydractinia Symbiolongicarpus
''Hydractinia symbiolongicarpus'' is one of the 30 + ''Hydractinia'' species known worldwide. This saltwater animal, from here on referred to as ''Hydractinia'', is at the base of the Cnidaria phylum and in many ways, is similar to the freshwater ''Hydra''. In the wild, ''Hydractinia'' feed on smaller invertebrates found in the shallow mud, however in laboratory environments they are fed brine shrimp. ''Hydractinia symbiolongicurpus'' and its sibling species, ''Hydractinia echinata'', are the two species from the genus ''Hydractinia'' on which most work has been published. Description ''Hydractinia'' consist of a network of gastrovascular canals embedded in a plate of tissue called the mat. When gastrovascular canals extend outside of the mat, they are called stolons. The stolon tips on the outer edge of the colony secrete SIF (Stolon Inducing Factor) allowing for the creation of branching stolons In the field, colonies exhibit morphologies that range from highly stolonife ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
