|
Platemys
The twist-necked turtle (''Platemys platycephala''), also known as the flat-headed turtle, is distributed widely across northern South America. Twist-necked turtles have extremely flat shells that help them hide from predators under rocks and debris. When threatened, this turtle withdraws by twisting its head into its shell. ''P. platycephala'' is the only species of the genus ''Platemys'' and occurs in northern and central South America. ''Platemys platycephala'' means "flat turtle, flat-head" and accurately describes the structure of the head and shell. This species inhabits shallow creek beds and frequently forages on the floor of the Amazon rainforest for insects, amphibians, and mollusks. Camouflage, head and body shape, and advanced sexual anatomy allow this species of turtle to effectively populate much of South America. Mating occurs during rainy months (March–December) and egg deposit occurs during dry months (January–March). Males have been known to behave aggressive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acanthochelys
''Acanthochelys'' is a genus of turtles, the spiny swamp turtles, in the family Chelidae, subfamily Chelinae, found in South America. Until recently, the species of this genus were considered to be members of the genus '' Platemys'', but were moved to the resurrected genus originally described by Gray (1873) based on the type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ... by monotypy ''Acanthochelys spixii''.Iverson, J. B. 1992. A Revised Checklist with Distribution Maps of the Turtles of the World. Privately Printed, Richmond: Indiana. 364pp. Taxonomy Current nomenclature for this genus follows that of van Dijk et al. (2012):Peter Paul van Dijk, John B. Iverson, H. Bradley Shaffer, Roger Bour, and Anders G.J. Rhodin. 2012. Turtles of the World, 2012 Update: Annotated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chimerism
A genetic chimerism or chimera ( or ) is a single organism composed of cells of different genotype, genotypes. Animal chimeras can be produced by the fusion of two (or more) embryos. In plants and some animal chimeras, Mosaic (genetics), mosaicism involves distinct types of tissue that originated from the same zygote but differ due to mutation during ordinary cell division. Normally, genetic chimerism is not visible on casual inspection; however, it has been detected in the course of proving parentage. More practically, in agronomy, "chimera" indicates a plant or portion of a plant whose tissues are made up of two or more types of cells with different genetic makeup; it can derive from a bud mutation or, more rarely, at the grafting point, from the concrescence of cells of the two bionts; in this case it is commonly referred to as a "graft hybrid", although it is not a hybrid in the genetic sense of "hybrid". In contrast, an individual where each cell contains genetic materi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phoxinus
''Phoxinus'' is a genus of freshwater fish in the family Leuciscidae of order Cypriniformes, and the only members of the subfamily Phoxininae, or Eurasian minnows. The other species in this genus are also commonly known as minnows. The name "minnow" was what early English fisherman used to describe "small and insignificant". The genus ''Phoxinus'' is found throughout Eurasia, and includes 21 known species. Previously, members of the North American genus '' Chrosomus'' were also believed to form part of this genus. Species ''Phoxinus'' contains the following species: * '' Phoxinus abanticus'' Turan, Bayçelebi, Özuluğ, Gaygusuz & Aksu, 2023 * '' Phoxinus adagumicus'' Artaev, Turbanov, Bolotovskiy, Gandlin & Levin, 2024 * '' Phoxinus bigerri'' Kottelat, 2007 (Pyrenean minnow) * '' Phoxinus brachyurus'' Berg, 1912 (Seven Rivers minnow) * '' Phoxinus chrysoprasius'' (Pallas, 1814) * '' Phoxinus colchicus'' Berg, 1910. * '' Phoxinus csikii'' Hankó, 1922 (Danube minnow) * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lacertidae
The Lacertidae are the family of the wall lizards, true lizards, or sometimes simply lacertas, which are native to Afro-Eurasia. It is a diverse family with at about 360 species in 39 genera. They represent the dominant group of reptiles found in Europe. Habitat The European and Mediterranean species of lacertids live mainly in forest and scrub habitats. ''Eremias'' and ''Ophisops'' species replace these in the grassland and desert habitats of Asia. African species usually live in rocky, arid areas. '' Holaspis'' species are among the few arboreal lacertids, and its two species, '' Holaspis guentheri'' and '' Holaspis laevis'', are gliders (although apparently poor ones), using their broad tail and flattened body as an aerofoil. Description Lacertids are small to medium-sized lizards. Most species are less than 9cm long, excluding the tail. The largest living species, '' Gallotia stehlini'', reaches 46cm, and some extinct forms were larger still. They are primarily insect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triploid
Polyploidy is a condition in which the cells of an organism have more than two paired sets of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two complete sets of chromosomes, one from each of two parents; each set contains the same number of chromosomes, and the chromosomes are joined in pairs of homologous chromosomes. However, some organisms are polyploid. Polyploidy is especially common in plants. Most eukaryotes have diploid somatic cells, but produce haploid gametes (eggs and sperm) by meiosis. A monoploid has only one set of chromosomes, and the term is usually only applied to cells or organisms that are normally diploid. Males of bees and other Hymenoptera, for example, are monoploid. Unlike animals, plants and multicellular algae have life cycles with two alternating multicellular generations. The gametophyte generation is haploid, and produces gametes by mitosis; the sporophyte generation is diploid and p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orinoco
The Orinoco () is one of the longest rivers in South America at . Its drainage basin, sometimes known as the Orinoquia, covers approximately 1 million km2, with 65% of it in Venezuela and 35% in Colombia. It is the List of rivers by discharge, fourth largest river in the world by Discharge (hydrology), discharge volume of water (39,000 m3/s at Orinoco Delta, delta) due to the high precipitation throughout its catchment area (ca 2,300 mm/a). The Orinoco River and its tributaries are the major transportation system for eastern and interior Venezuela and the Llanos of Colombia. The environment and wildlife in the Orinoco's basin are extremely diverse. Etymology The river's name is derived from the Warao language, Warao term for "a place to paddle", itself derived from the terms ''güiri'' (paddle) and ''noko'' (place) i.e. a navigable place. History The mouth of the Orinoco River at the Atlantic Ocean was documented by Christopher Columbus on 1 August 1498, during his Christo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamete
A gamete ( ) is a Ploidy#Haploid and monoploid, haploid cell that fuses with another haploid cell during fertilization in organisms that Sexual reproduction, reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. The name gamete was introduced by the German cytologist Eduard Strasburger in 1878. Gametes of both mating individuals can be the same size and shape, a condition known as isogamy. By contrast, in the majority of species, the gametes are of different sizes, a condition known as anisogamy or heterogamy that applies to humans and other mammals. The human ovum has approximately 100,000 times the volume of a single human sperm cell. The type of gamete an organism produces determines its sex and sets the basis for the sexual roles and sexual selection. In humans and other species that produce two Morphology (biology), morphologically distinct types of gametes, and in which Gonochorism, each individual produces only one type, a femal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Somatic (biology)
In cellular biology, the term somatic is derived from the French somatique which comes from Ancient Greek σωματικός (sōmatikós, “bodily”), and σῶμα (sôma, “body”.) is often used to refer to the cells of the body, in contrast to the reproductive ( germline) cells, which usually give rise to the egg or sperm (or other gametes in other organisms). These somatic cells are diploid, containing two copies of each chromosome, whereas germ cells are haploid, as they only contain one copy of each chromosome (in preparation for fertilisation). Although under normal circumstances all somatic cells in an organism contain identical DNA, they develop a variety of tissue-specific characteristics. This process is called differentiation, through epigenetic and regulatory alterations. The grouping of similar cells and tissues creates the foundation for organs. Somatic mutations are changes to the genetics of a multicellular organism that are not passed on to its offspr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
