It has been suggested that the larger dinosaurs would have been gigantothermic, rendering them virtually homeothermic.
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A class of endothermic organisms known as homeotherms maintain internal temperatures with minimal metabolic regulation within a range of ambient temperatures called the thermal neutral zone (TNZ). Within the TNZ the basal rate of heat production is equal to the rate of heat loss to the environment. Homeothermic organisms adjust to the temperatures within the TNZ through different responses requiring little energy. Environmental temperatures can cause fluctuations in a homeothermic organism’s metabolic rate.
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This also suggests that body temperature rhythms, as controlled by the SCN in homeothermic mammals, is a potential mechanism through which the master clock may synchronize circadian oscillators within tissues throughout the body.
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Dimetrodon may have angled its sail away from the sun to cool off or restricted blood flow to the sail to maintain heat at night. In 1986, J. Scott Turner and C. Richard Tracy proposed that the evolution of a sail in Dimetrodon was related to the evolution of warm-bloodedness in mammal ancestors. They thought that the sail of Dimetrodon enabled it to be homeothermic, maintaining a constant, albeit low, body temperature. Mammals are also homeothermic, although they differ from Dimetrodon in being endothermic, controlling their body temperature internally through heightened metabolism.
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For example, the study found out that homeothermic vertebrae such as elephant nose fish, Gnathonemus petersii has a large brain that is related to a smaller intestine and stomach size. Which suggested that energy constraints on brain size evolution are found in at least highly encephalized tropical species. Additionally, the study found that the evolution of brain size is associated with an increase in egg size can lead to an extended period of parental care. This also shows that the presence of the energetic constraints of encephalization is also being applied to homeothermic vertebrates.
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Usually the fluctuations are consequence of variation in the ambient environmental temperature. Many terrestrial ectotherms are poikilothermic. However some ectotherms remain in temperature-constant environments to the point that they are actually able to maintain a constant internal temperature (i.e. are homeothermic).
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The great white shark is also capable of speed bursts. These exceptions may be due to the warm-blooded, or homeothermic, nature of these sharks' physiology. Sharks can travel 70 to 80 km in a day.The secret life of sharks , Maria Moscaritolo, The Adelaide Advertiser, 3 March 2012.
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Homeothermy and poikilothermy refer to how stable an organism's deep-body temperature is. Most endothermic organisms are homeothermic, like mammals. However, animals with facultative endothermy are often poikilothermic, meaning their temperature can vary considerably. Most fish are ectotherms, as most of their heat comes from the surrounding water.
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Steen, J.B, Steen, H. & Stenseth, N.C. (1991): Population Dynamics of Poikilotherm and Homeotherm Vertebrates: Effects of Food Shortage. OICOS Vol. 60, No 2 (March, 1991), pp 269-272. summary This is reflected in the predator- prey ratio which is usually higher in poikilothermic fauna compared to homeothermic ones.
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The infrared sense enables Desmodus to localize homeothermic (warm-blooded) animals (cattle, horses, wild mammals) within a range of about 10 to 15 cm. This infrared perception is possibly used in detecting regions of maximal blood flow on targeted prey. Recent researchBálint, A., Andics, A., Gácsi, M. et al. Dogs can sense weak thermal radiation.
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They brood the chicks over a period of 12 to 14 days, by which point they are feathered and homeothermic. The female feeds the chicks from 1 to 3 times every hour by regurgitation, usually while the female continues hovering. When they are 18 to 22 days old, the young leave the nest and make their first flight.
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The dynamic mass of neonates modifies the thermal environment at the burrow entrance such that the young can occupy a location that would ordinarily become lethally hot for an individual neonate (or even an adult). Because of the constant movements of the neonates, the aggregate assumes stable temperature properties reminiscent of a homeothermic organism (i.e., maintains tight temperature tolerance ± 2 °C).
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Common vampire bats (Desmodus rotundus) have specialized IR sensors in their nose-leaf. Vampire bats are the only mammals that feed exclusively on blood. The IR sense enables Desmodus to localize homeothermic animals such as cattle and horses within a range of about 10 to 15 cm. This infrared perception may be used in detecting regions of maximal blood flow on targeted prey.
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It has been shown through experimentation that animals subjected to inability to enter REM sleep show an immediate attempt to quickly enter REM stages and long-term effects on motor coordination and habitual motor habits, eventually leading to the death of the animal. It has also been shown that homeothermic animals might require sleep to maintain body weight and temperature.
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Because many homeothermic animals use enzymes that are specialized for a narrow range of body temperatures, hypothermia rapidly leads to torpor and then death. Additionally, homeothermy obtained from endothermy is a high energy strategy and many environments will offer lower carrying capacity to these organisms. In cold weather the energy expenditure to maintain body temperature accelerates starvation and may lead to death.
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Heterothermic animals are those that can switch between poikilothermic and homeothermic strategies. These changes in strategies typically occur on a daily basis or on an annual basis. More often than not, it is used as a way to dissociate the fluctuating metabolic rates seen in some small mammals and birds (e.g. bats and hummingbirds), from those of traditional cold blooded animals.
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In many bat species, body temperature and metabolic rate are elevated only during activity. When at rest, these animals reduce their metabolisms drastically, which results in their body temperature dropping to that of the surrounding environment. This makes them homeothermic when active, and poikilothermic when at rest. This phenomenon has been termed 'daily torpor' and was intensively studied in the Djungarian hamster.
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An osmoreceptor is a sensory receptor primarily found in the hypothalamus of most homeothermic organisms that detects changes in osmotic pressure. Osmoreceptors can be found in several structures, including two of the circumventricular organs – the vascular organ of the lamina terminalis, and the subfornical organ. They contribute to osmoregulation, controlling fluid balance in the body. Osmoreceptors are also found in the kidneys where they also modulate osmolality.
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It is comparatively easy for a poikilotherm to accumulate enough energy to reproduce. Poikilotherms at the same trophic level often have much shorter generations than homeotherms: weeks rather than years. Such applies even to animals with similar ecological roles such as cats and snakes. This difference in energy requirement also means that a given food source can support a greater density of poikilothermic animals than homeothermic animals.
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The opah's pectoral muscles generate most of its body heat. The opah retains heat with insulating layers of fat, which insulates the heart from the gills, and the pectoral muscles from the surrounding water. The opah is not homeothermic (maintaining a stable internal temperature) like birds and mammals. Fish like the opah maintain an internal temperature higher than the surrounding water but not a constant temperature the way that mammals do.
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At birth, S. saturatus are ectothermic. Development of endothermy occurs gradually as individuals grow, increasing both body mass and amount of body fur. Individuals removed from their mother at 6 days of age lost body temperature at a faster rate than at 36 days, when individuals were able to maintain a high internal body temperature and determined to be homeothermic. This 36-day mark is conveniently the age at which offspring leave their burrows.
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Individuals remained homeothermic in response to a 2-day removal of food and water at 2-week intervals. Even with this drastically reduced body mass, torpor was not induced. Smaller individuals did become hypothermic, however, and were returned to the mother to be re-warmed. Daily energy expenditures showed a small but significant increase of 10% as litter size increased, across a range of 3 to 5 offspring, the norm for the species.
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Allen's rule is an ecogeographical rule formulated by Joel Asaph Allen in 1877, broadly stating that animals adapted to cold climates have shorter limbs and bodily appendages than animals adapted to warm climates. More specifically, it states that the body surface area-to- volume ratio for homeothermic animals varies with the average temperature of the habitat to which they are adapted (i.e. the ratio is low in cold climates and high in hot climates).
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Thermographic image: a cold-blooded snake is shown eating a warm-blooded mouse Warm-blooded are those animal species which can maintain a body temperature higher than their environment. In particular, homeothermic species maintain a stable body temperature by regulating metabolic processes. The only known living homeotherms are birds and mammals, though ichthyosaurs, pterosaurs, plesiosaurs and non-avian dinosaurs are believed to have been homeotherms. Other species have various degrees of thermoregulation.
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Siberian tiger In zoology, mammalogy is the study of mammals – a class of vertebrates with characteristics such as homeothermic metabolism, fur, four- chambered hearts, and complex nervous systems. Mammalogy has also been known as "mastology," "theriology," and "therology." The archive of number of mammals on earth is constantly growing, but is currently set at 6,495 different mammal species including recently extinct. There are 5,416 living mammals identified on earth and roughly 1,251 have been newly discovered since 2006.
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The gradient steepness (the amount of change in species richness with latitude) is not influenced by dispersal, animal physiology (homeothermic or ectothermic) trophic level, hemisphere, or the latitudinal range of study. The study could not directly falsify or support any of the above hypotheses, however, results do suggest a combination of energy/climate and area processes likely contribute to the latitudinal species gradient. Notable exceptions to the trend include the ichneumonidae, shorebirds, penguins, and freshwater zooplankton.
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The spurs of Catopsbaatar and other Mesozoic mammals may have been used for protection against theropod dinosaurs and other predators. Multituberculates are thought to have given live birth, and the fact that they had hair indicates they were homeothermic ("warmblooded"). Multituberculates would have been omnivorous; Catopsbaatar had powerful jaw muscles, and its incisors were well adapted for gnawing hard seeds, using a backwards chewing stroke. Multituberculates are thought to have had a sprawling posture, and Catopsbaatar may have been able to jump.
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As with other ratites, the emu has great homeothermic ability, and can maintain this status from . The thermoneutral zone of emus lies between . As with other ratites, emus have a relatively low basal metabolic rate compared to other types of birds. At , the metabolic rate of an emu sitting down is about 60% of that when standing, partly because the lack of feathers under the stomach leads to a higher rate of heat loss when standing from the exposed underbelly.
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The naked mole-rat does not regulate its body temperature in typical mammalian fashion. They are thermoconformers rather than thermoregulators in that, unlike other mammals, body temperature tracks ambient temperatures. However, it has also been claimed that "the Naked Mole- Rat has a distinct temperature and activity rhythm that is not coupled to environmental conditions." The relationship between oxygen consumption and ambient temperature switches from a typical poikilothermic pattern to a homeothermic mode when temperature is at 29 °C or higher.
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Common ostriches are homeothermic endotherms; they regulate a constant body temperature via regulating their metabolic heat rate. They closely regulate their core body temperature, but their appendages may be cooler in comparison as found with regulating species. The temperature of their beak, neck surfaces, lower legs, feet and toes are regulated through heat exchange with the environment. Up to 40% of their produced metabolic heat is dissipated across these structures, which account for about 12% of their total surface area.
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The study analyzed seasonal variations in the body temperature and differences in temperature between skeletal regions, to determine whether the dinosaurs maintained their temperature seasonally. A varanid lizard fossil sampled for the study showed isotopic variation consistent with it being an heterothermic ectotherm. The variation of the dinosaurs, including Achelousaurus, was consistent with them being homeothermic endotherms. The metabolic rate of these dinosaurs was likely not as high as that of modern mammals and birds, and they may have been intermediate endotherms.
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As a result, poikilotherms often have larger, more complex genomes than homeotherms in the same ecological niche. Frogs are a notable example of this effect, though their complex development is also an important factor in their large genome. Because their metabolism is variable and generally below that of homeothermic animals, sustained high-energy activities like powered flight in large animals or maintaining a large brain is generally beyond poikilotherm animals.Willmer, P., Stone, G., & Johnston, I. A. (2000): Environmental physiology of animals.
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A large proportion of the creatures traditionally called "warm- blooded", like birds and mammals, fit all three of these categories (i.e., they are endothermic, homeothermic, and tachymetabolic). However, over the past 30 years, studies in the field of animal thermophysiology have revealed many species belonging to these two groups that do not fit all these criteria. For example, many bats and small birds are poikilothermic and bradymetabolic when they sleep for the night (or, in nocturnal species, for the day).
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The neck was strong and the pectoral girdle proportionally small. Part of the family Carcharodontosauridae, Giganotosaurus is one of the most completely known members of the group, which includes other very large theropods, such as the closely related Mapusaurus and Carcharodontosaurus. Giganotosaurus is thought to have been homeothermic (a type of "warm-bloodedness"), with a metabolism between that of a mammal and a reptile, which would have enabled fast growth. It may have been relatively fast moving, with a calculated maximal running speed of .
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It has been stated that REM sleep is a recent evolutionary behavior in homeothermic animals. In both, there is increased REM sleep in the early stages of life. In humans, REM sleep peaks during the third trimester of gestation, and quickly falls after birth as primary consciousness declines and secondary consciousness grows with the development of the brain. The developing control over stages of sleep and waking suggests that sleep and REM has developed as a way to self-activate in order to anticipate awake-state circumstances.
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This principle is used industrially in building and piping insulation such as (glass wool), cellulose, rock wool, polystyrene foam (styrofoam), urethane foam, vermiculite, perlite, and cork. Trapping air is also the principle in all highly insulating clothing materials such as wool, down feathers and fleece. The air-trapping property is also the insulation principle employed by homeothermic animals to stay warm, for example down feathers, and insulating hair such as natural sheep's wool. In both cases the primary insulating material is air, and the polymer used for trapping the air is natural keratin protein.
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Thermographic image of a bat using trapped air as insulation Most bats are homeothermic (having a stable body temperature), the exception being the vesper bats (Vespertilionidae), the horseshoe bats (Rhinolophidae), the free-tailed bats (Molossidae), and the bent-winged bats (Miniopteridae), which extensively use heterothermy (where body temperature can vary). Compared to other mammals, bats have a high thermal conductivity. The wings are filled with blood vessels, and lose body heat when extended. At rest, they may wrap their wings around themselves to trap a layer of warm air.
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They are known as hummingbirds because of the humming sound created by their beating wings, which flap at high frequencies audible to humans. They hover in mid-air at rapid wing-flapping rates, which vary from around 12 beats per second in the largest species, to in excess of 80 in some of the smallest. Of those species that have been measured in wind tunnels, their top speeds exceed and some species can dive at speeds in excess of . Hummingbirds have the highest mass-specific metabolic rate of any homeothermic animal.
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One famous fossil is that of a mother and baby that died in childbirth (ichthyosaurs were viviparous). This proved that ichthyosaur infants were born tail-first, just like cetaceans, to prevent them from drowning before fully clearing the birth canal. Stenopterygius was a very fast swimmer, with a cruising speed similar to that of tuna, which is among the fastest of all living fishes. In 2018, a Stenopterygius specimen was reported with evidence of having had blubber, which indicates that other ichthyosaurs and it were homeothermic ("warm blooded").
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Richet in 1922 He was born on 25 August 1850 in Paris the son of Alfred Richet. He was educated at the Lycee Bonaparte in Paris then studied Medicine at university in Paris. Richet spent a period of time as an intern at the Salpêtrière hospital in Paris, where he observed Jean-Martin Charcot's work with then so called "hysterical" patients. In 1887, Richet became professor of physiology at the Collège de France investigating a variety of subjects such as neurochemistry, digestion, thermoregulation in homeothermic animals, and breathing.
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Endothermic/homeothermic animals can be optimally active at more times during the diurnal cycle in places of sharp temperature variations between day and night and during more of the year in places of great seasonal differences of temperature. This is accompanied by the need to expend more energy to maintain the constant internal temperature and a greater food requirement. Endothermy may be important during reproduction, for example, in expanding the thermal range over which a species can reproduce, as embryos are generally intolerant of thermal fluctuations that are easily tolerated by adults. Endothermy may also provide a protection against fungal infection.
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However, as a homeothermic endotherm it is still faced with the challenge of maintaining a constant body temperature while being exposed to both the day (light period) and night (dark period) temperatures of its environments. Phoenicopterus ruber have evolved a number of thermoregulatory mechanisms to keep itself cool during the light period and warm during the dark period without expending too much energy. The American flamingo has been observed in a temperature niche between . In order to prevent water loss through evaporation when temperatures are elevated the flamingo will employ hyperthermia as a nonevaporative heat loss method keeping its body temperature between .
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Restoration with size comparison In 1999, the paleontologist Reese E. Barrick and the geologist William J. Showers found that the bones of Giganotosaurus and Tyrannosaurus had very similar oxygen isotope patterns, with similar heat distribution in the body. These thermoregulatory patterns indicate that these dinosaurs had a metabolism intermediate between that of mammals and reptiles, and were therefore homeothermic (with a stable core body-temperature, a type of "warm-bloodedness"). The metabolism of an Giganotosaurus would be comparable to that of a mammalian carnivore, and would have supported rapid growth. In 2001, the physicist Rudemar Ernesto Blanco and Mazzetta evaluated the cursorial (running) capability of Giganotosaurus.
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Most sharks are "cold-blooded" or, more precisely, poikilothermic, meaning that their internal body temperature matches that of their ambient environment. Members of the family Lamnidae (such as the shortfin mako shark and the great white shark) are homeothermic and maintain a higher body temperature than the surrounding water. In these sharks, a strip of aerobic red muscle located near the center of the body generates the heat, which the body retains via a countercurrent exchange mechanism by a system of blood vessels called the rete mirabile ("miraculous net"). The common thresher and bigeye thresher sharks have a similar mechanism for maintaining an elevated body temperature.
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However, the fairly derived Sinoconodon appears to have uniquely discarded milk altogether. Prior to hatching, the milk glands would provide moisture to the leathery eggs, a situation still found in monotremes. The early mammaliaforms did have a harderian gland. In modern mammals, this is used for cleaning the fur, indicating that they, contrary to their Cynodont ancestors, had a furry covering. An insulative covering is necessary to keep a homeothermic animal warm if it is very small, less than 5 cm (1.97 in) long; The 3.2 cm (1.35 in) Hadrocodium must have had fur, therefore, but the 10 cm (3.94 in) Morganucodon might not have needed it.
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Even though the study provided distinct evidence to prove that brain size and gut size are negatively correlated with one another, however, there wasn't strong evidence to prove that. For instance, most of the study done on the live-bearing and egg-bearing species within Chondrichthyans, cannot be generalized across all homeothermic and ectothermic vertebrates. Further studies did show that there is definitely a positive correlation between brain mass residuals and BMS residuals in mammals, but the relationship is only significant in primates. When considering the expensive tissue hypothesis, we also need to consider how the Energy Trade-off Hypothesis affects the body too.
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Megabats were generally believed to be homeothermic, but three species of small megabats, with a mass of about , have been known to use torpor: the common blossom bat (Syconycteris australis), the long-tongued nectar bat (Macroglossus minimus), and the eastern tube-nosed bat (Nyctimene robinsoni). Torpid states last longer in the summer for megabats than in the winter. During hibernation, bats enter a torpid state and decrease their body temperature for 99.6% of their hibernation period; even during periods of arousal, when they return their body temperature to normal, they sometimes enter a shallow torpid state, known as "heterothermic arousal". Some bats become dormant during higher temperatures to keep cool in the summer months.
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There has long been debate about the thermoregulation of dinosaurs, centered around whether they were ectotherms ("cold-blooded") or endotherms ("warm-blooded"). Mammals and birds are homeothermic endotherms, which generate their own body heat and have a high metabolism, whereas reptiles are heterothermic ectotherms, which receive their body heat from their surroundings. A 1996 study examined the oxygen isotopes from bone phosphates of animals from the Two Medicine Formation, including the juvenile Achelousaurus specimen MOR 591\. δ18O values of phosphate in vertebrate bones depend on the δ18O values in their body water and the temperature when the bones were deposited, making it possible to measure fluctuations in temperature for each bone of an individual when they were deposited.
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During this time, the female is fed four or five times a day by the male, approximately once every two hours, outside the nest hole. The young are brooded by the female, and are left unattended most of the day from two weeks after hatching. Nestlings about two weeks old were observed being fed by a parent with intervals of up to 79 minutes. It is unclear if one or both parents feed the young, but, as in other parrots, the female probably stays with them for the first few days while fed by the male, and when the young are homeothermic (have a stable body temperature), both take care of and feed the nestlings.
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Despite the low likelihood of its occurrence, oceanic dispersal remains the most accepted explanation for numerous vertebrate colonizations of Madagascar, including that of the lemurs. Although unlikely, over long periods of time terrestrial animals can occasionally raft to remote islands on floating mats of tangled vegetation, which get flushed out to sea from major rivers by floodwaters. Any extended ocean voyage without fresh water or food would prove difficult for a large, warm-blooded (homeothermic) mammal, but today many small, nocturnal species of lemur exhibit heterothermy, which allows them to lower their metabolism and become dormant while living off fat reserves. Such a trait in a small, nocturnal lemur ancestor would have facilitated the ocean voyage and could have been passed on to its descendants.
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Like other sauropods, Brachiosaurus was probably homeothermic (maintaining a stable internal temperature) and endothermic (controlling body temperature through internal means) at least while growing, meaning that it could actively control its body temperature ("warm-blooded"), producing the necessary heat through a high basic metabolic rate of its cells. Russel (1989) used Brachiosaurus as an example of a dinosaur for which endothermy is unlikely, because of the combination of great size (leading to overheating) and great caloric needs to fuel endothermy. Sander (2010) found that these calculations were based on incorrect body mass estimates and faulty assumptions on the available cooling surfaces, as the presence of large air sacs was unknown at the time of the study. These inaccuracies resulted in the overestimation of heat production and the underestimation of heat loss.
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Some of these animals live in environments where temperatures are practically constant, as is typical of regions of the abyssal ocean and hence can be regarded as homeothermic ectotherms. In contrast, in places where temperature varies so widely as to limit the physiological activities of other kinds of ectotherms, many species habitually seek out external sources of heat or shelter from heat; for example, many reptiles regulate their body temperature by basking in the sun, or seeking shade when necessary in addition to a whole host of other behavioral thermoregulation mechanisms. For home captivity of pet reptiles, owners can use a UVB/UVA light system to assist the animals' basking behaviour. In contrast to ectotherms, endotherms rely largely, even predominantly, on heat from internal metabolic processes, and mesotherms use an intermediate strategy.
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The pre-flight warm-up behavior of a moth Insect thermoregulation is the process whereby insects maintain body temperatures within certain boundaries. Insects have traditionally been considered as poikilotherms (animals in which body temperature is variable and dependent on ambient temperature) as opposed to being homeothermic (animals that maintain a stable internal body temperature regardless of external influences). However, the term temperature regulation, or thermoregulation, is currently used to describe the ability of insects and other animals to maintain a stable temperature (either above or below ambient temperature), at least in a portion of their bodies by physiological or behavioral means. While many insects are ectotherms (animals in which their heat source is primarily from the environment), others are endotherms (animals that can produce heat internally by biochemical processes).
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Similar to other hummingbird species, the green-headed hillstar has one of the highest mass-specific metabolic rates of all homeothermic animals, and therefore must consume a large quantity of sugar everyday in order to sustain this high metabolism. To reduce the metabolic cost of energy during the night when they are not feeding, hummingbirds are one of the few bird species that enter a state of torpor, or deep sleep, to reduce their metabolic rate to 1/15 of its normal rate. Hillstar species, like the green-headed hillstar, have further developed these behavioural adaptations in order to live in the especially cold climate of the Andes. For example, on cold nights the green-headed hillstar enters a state of torpor and will sleep in sheltered places like cavities in rocks or caves, and often sleep nestled close together with several other hillstars in order to reduce heat loss from their bodies.
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A resting Kosmoceratops being disturbed by the troodontid Talos In a 2013 Master's thesis (summarized in a published paper by different authors in 2019), paleontologist Carolyn Gale Levitt histologically studied the long bones of Kosmoceratops (femora of the adult holotype and the assigned subadult or adult UMNH VP 21339) and Utahceratops to examine indicators of growth and maturity in the bone microstructure (until then the only chasmosaurines ever sampled for this). The bone tissue had a high number of osteocytes (bone cells) as well as a dense network of blood vessels, including radially oriented vascular canals (blood canals running towards the bone interior), indicating sustained rapid growth. These features also indicate that ceratopsians had an elevated metabolism and were homeothermic endotherms (or "warm-blooded"), like modern birds and mammals. The Kosmoceratops and Utahceratops bones sampled by Levitt did not show evidence of lines of arrested growth (annual growth lines), and compared with the ceratopsids Pachyrhinosaurus, Centrosaurus, and Einosaurus from further north which did have growth lines, this may indicate that bone growth reacted to climate and that Kosmoceratops and Utahceratops could sustain their growth throughout the year due to their more equitable southern climate.
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