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Parietal Eye
A parietal eye (third eye, pineal eye) is a part of the epithalamus in some vertebrates. The eye is at the top of the head; is photoreceptive; and is associated with the pineal gland, which regulates circadian rhythmicity and hormone production for thermoregulation. The hole that contains the eye is known as the pineal foramen or parietal foramen, because it is often enclosed by the parietal bones. The parietal eye was discovered by Franz Leydig, in 1872, from work with lizards. Discovery Franz Leydig, a professor of zoology at the University of Tübingen, dissected four species of European lizards—the slow worm ('' Anguis fragilis'') and three species of '' Lacerta''. in 1872; He found cup-like protrusions under the middles of their brains. He believed the protrusions to be glandular and called them frontal organs (German ''Stirnorgan''). In 1886, Walter Baldwin Spencer, an anatomist at the University of Oxford, reported the results of his dissection of 29 species of li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frog Parietal Eye
A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order (biology), order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough skin texture due to wart-like parotoid glands tend to be called toads, but the distinction between frogs and toads is informal and purely cosmetic, not from taxonomy (biology), taxonomy or evolutionary history. Frogs are widely distributed, ranging from the tropics to subarctic regions, but the greatest concentration of species diversity is in tropical rainforest and associated wetlands. They account for around 88% of extant amphibian species, and are one of the five most diverse vertebrate orders. The oldest fossil "proto-frog" ''Triadobatrachus'' is known from the Early Triassic of Madagascar (250Myr, million years ago), but molecular clock, molecular clock dating suggests their divergent evolution, divergence from other amphibians may exte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Swedes
Swedes (), or Swedish people, are an ethnic group native to Sweden, who share a common ancestry, Culture of Sweden, culture, History of Sweden, history, and Swedish language, language. They mostly inhabit Sweden and the other Nordic countries, Swedish-speaking population of Finland, in particular, neighboring Finland, where they are an officially recognized minority, with Swedish being one of the official languages of the country, and with a substantial Swedish diaspora, diaspora in other countries, especially the Swedish Americans, United States. Etymology The English term "Swede" has been attested in English since the late 16th century and is of Middle Dutch or Middle Low German origin. In Swedish language, Swedish, the term is ''svensk'', which is from the name of ''svear'' (or Swedes), the people who inhabited Svealand in eastern central Sweden, and were listed as ''Suiones'' in Tacitus' history ''Germania (book), Germania'' from the first century AD. The term is believed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endotherm
An endotherm (from Greek ἔνδον ''endon'' "within" and θέρμη ''thermē'' "heat") is an organism that maintains its body at a metabolically favorable temperature, largely by the use of heat released by its internal bodily functions instead of relying almost purely on ambient heat. Such internally generated heat is mainly an incidental product of the animal's routine metabolism, but under conditions of excessive cold or low activity an endotherm might apply special mechanisms adapted specifically to heat production. Examples include special-function muscular exertion such as shivering, and uncoupled oxidative metabolism, such as within brown adipose tissue. Only birds and mammals are considered truly endothermic groups of animals. However, Argentine black and white tegu, leatherback sea turtles, lamnid sharks, tuna and billfishes, cicadas, and winter moths are mesothermic. Unlike mammals and birds, some reptiles, particularly some species of python and tegu, po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extinction
Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and recover. As a species' potential Range (biology), range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxon, Lazarus taxa, where a species presumed extinct abruptly "reappears" (typically in the Fossil, fossil record) after a period of apparent absence. Over five billion species are estimated to have died out. It is estimated that there are currently around 8.7 million species of eukaryotes globally, possibly many times more if microorganisms are included. Notable extinct animal species include Dinosaur, non-avian dinosaurs, Machairodontinae, saber-toothed cats, and mammoths. Through evolution, species arise through the process of specia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mammal
A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three Evolution of mammalian auditory ossicles, middle ear bones. These characteristics distinguish them from reptiles and birds, from which their ancestors Genetic divergence, diverged in the Carboniferous Period over 300 million years ago. Around 6,640 Neontology#Extant taxon, extant species of mammals have been described and divided into 27 Order (biology), orders. The study of mammals is called mammalogy. The largest orders of mammals, by number of species, are the rodents, bats, and eulipotyphlans (including hedgehogs, Mole (animal), moles and shrews). The next three are the primates (including humans, monkeys and lemurs), the Artiodactyl, even-toed ungulates (including pigs, camels, and whales), and the Carnivora (including Felidae, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lamprey
Lampreys (sometimes inaccurately called lamprey eels) are a group of Agnatha, jawless fish comprising the order (biology), order Petromyzontiformes , sole order in the Class (biology), class Petromyzontida. The adult lamprey is characterized by a toothed, funnel-like sucking mouth. The common name "lamprey" is probably derived from Latin , which may mean "stone licker" ( "to lick" + "stone"), though the etymology is uncertain. "Lamprey" is sometimes seen for the plural form. About 38 extant species of lampreys are known, with around seven known extinct species. They are classified in three families—two small families in the Southern Hemisphere (Geotriidae, Mordaciidae) and one large family in the Northern Hemisphere (Petromyzontidae). Genetic evidence suggests that lampreys are more closely related to hagfish, the only other living group of jawless fish, than they are to jawed vertebrates, forming the superclass Cyclostomi. The oldest fossils of stem-group lampreys are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shark
Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the Division (taxonomy), division Selachii and are the sister group to the Batoidea, Batomorphi (Batoidea, rays and skate (fish), skates). Some sources extend the term "shark" as an informal category including Extinction, extinct members of Chondrichthyes (cartilaginous fish) with a shark-like morphology, such as hybodonts. Shark-like chondrichthyans such as ''Cladoselache'' and ''Doliodus'' first appeared in the Devonian Period (419–359 million years), though some fossilized chondrichthyan-like scales are as old as the Ordovician, Late Ordovician (458–444 million years ago). The earliest confirmed modern sharks (Selachii) are known from the Early Jurassic around , with the oldest known member being ''Agaleus'', though records of true shar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Osteichthyes
Osteichthyes ( ; ), also known as osteichthyans or commonly referred to as the bony fish, is a Biodiversity, diverse clade of vertebrate animals that have endoskeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes (cartilaginous fish) and the extinct placoderms and acanthodians, which have endoskeletons primarily composed of cartilage. The vast majority of extant taxon, extant fish are members of Osteichthyes, being an extremely diverse and abundant group consisting of 45 order (biology), orders, over 435 family (biology), families and 28,000 species. The group is divided into two main clades, the ray-finned fish (Actinopterygii, which makes up the vast majority of extant fish) and the lobe-finned fish (Sarcopterygii, which gave rise to all land vertebrates, i.e. tetrapods). The oldest known fossils of bony fish are about 425 million years old from the late Silurian, which are also transitional fossils showing a dentition, tooth pattern th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salamander
Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten extant salamander families are grouped together under the order Urodela, the sole surviving order from the group Caudata. ''Urodela'' is a scientific Latin term based on the Ancient Greek : ourà dēlē "conspicuous tail". ''Caudata'' is the Latin for "tailed ones", from : "tail". Salamander diversity is highest in eastern North America, especially in the Appalachian Mountains; most species are found in the Holarctic realm, with some species present in the Neotropical realm. Salamanders never have more than four toes on their front legs and five on their rear legs, but some species have fewer digits and others lack hind limbs. Their permeable skin usually makes them reliant on habitats in or near water or other cool, damp places. So ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tuatara
The tuatara (''Sphenodon punctatus'') is a species of reptile endemic to New Zealand. Despite its close resemblance to lizards, it is actually the only extant member of a distinct lineage, the previously highly diverse order Rhynchocephalia. The name is derived from the Māori language and means "peaks on the back". The single extant species of tuatara is the only surviving member of its order, which was highly diverse during the Mesozoic era. Rhynchocephalians first appeared in the fossil record during the Triassic, around 240 million years ago, and reached worldwide distribution and peak diversity during the Jurassic, when they represented the world's dominant group of small reptiles. Rhynchocephalians declined during the Cretaceous, with their youngest records outside New Zealand dating to the Paleocene. Their closest living relatives are squamates (lizards and snakes). Tuatara are of interest for studying the evolution of reptiles. Tuatara are greenish brown an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoreceptor Cell
A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiation) into signals that can stimulate biological processes. To be more specific, photoreceptor proteins in the cell absorb photons, triggering a change in the cell's membrane potential. There are currently three known types of photoreceptor cells in mammalian eyes: rod cell, rods, cone cell, cones, and intrinsically photosensitive retinal ganglion cells. The two classic photoreceptor cells are rods and cones, each contributing information used by the visual system to form an image of the environment, Visual perception, sight. Rods primarily mediate scotopic vision (dim conditions) whereas cones primarily mediate photopic vision (bright conditions), but the processes in each that supports phototransduction is similar. The intrinsically photosen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
