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Bird

Bird

Many - see section below. Birds are bipedal, warm-blooded, egg-laying vertebrates characterized primarily by feathers, forelimbs modified as wings, and hollow bones. Birds range in size from the tiny hummingbirds to the huge Ostrich and Emu. Depending on taxonomic viewpoint, there are about 8,800–10,200 living bird species (plus about 120–130 that have become extinct in the span of human history) in the world, making them the most diverse class of terrestrial vertebrates. Birds are a very differentiated class, with some feeding on nectar, plants, seeds, insects, rodents, fish, carrion, or other birds. Most birds are diurnal, or active during the day. Some birds, such as the owls and nightjars, are nocturnal or crepuscular (active during twilight hours). Many birds migrate long distances to utilise optimum habitats (e.g., Arctic Tern) while others spend almost all their time at sea (e.g. the Wandering Albatross). Some, such as frigatebirds, stay aloft for days at a time, even sleeping on the wing. Common characteristics of birds include a bony beak with no teeth, the laying of hard-shelled eggs, high metabolic rate, and a light but strong skeletons. Most birds are characterised by flight, though the ratites are flightless, and several other species, particularly on islands, have also lost this ability. Flightless birds include the penguins, Ostrich, kiwi, and the extinct Dodo. Flightless species are vulnerable to extinction when humans or the mammals they introduce arrive in their habitat, for example the Great Auk, flightless rails, and the moa of New Zealand.

Bird orders

New Zealand This is a list of the taxonomic orders in the class Aves. The list of birds gives a more detailed summary, including families.
- Struthioniformes, Ostrich, emus, kiwis, and allies
- Tinamiformes, tinamous
- Anseriformes, waterfowl
- Galliformes, fowl
- Sphenisciformes, penguins
- Gaviiformes, loons
- Podicipediformes, grebes
- Procellariiformes, albatrosses, petrels, and allies
- Pelecaniformes, pelicans and allies
- Ciconiiformes, storks and allies
- Phoenicopteriformes, flamingos
- Accipitriformes, eagles, hawks and allies
- Falconiformes, falcons
- Turniciformes, button-quail
- Gruiformes, cranes and allies
- Charadriiformes, plovers and allies
- Pteroclidiformes, sandgrouse
- Columbiformes, doves and pigeons
- Psittaciformes, parrots and allies
- Cuculiformes, cuckoos
- Strigiformes, owls
- Caprimulgiformes, nightjars and allies
- Apodiformes, swifts
- Trochiliformes, hummingbirds
- Coraciiformes, kingfishers
- Piciformes, woodpeckers and allies
- Trogoniformes, trogons
- Coliiformes, mousebirds
- Passeriformes, passerines Note: This is the traditional classification (the so-called Clements order). A more recent, radically different classification based on molecular data has been developed (the so-called Sibley order) and is gaining acceptance.

Evolution

Birds are generally considered to have evolved from theropod dinosaurs. Specifically, birds are members of Maniraptora, a group of theropods which includes dromaeosaurs and oviraptorids. As more non-avian theropods that are closely related to birds are discovered, the formerly clear distinction between non-birds and birds becomes less so. Recent discoveries in North-east China (Liaoning Province) demonstrating that many small theropod dinosaurs had feathers contribute to this ambiguity. The basal bird Archaeopteryx, from the Jurassic, is well-known as one of the first "missing links" to be found in support of evolution in the late 19th century. It remains the most primitive known bird. Other Mesozoic birds include the Confuciusornithidae, Enantiornithes, Ichthyornis, and Hesperornithiformes, a group of flightless divers resembling grebes and loons. The recently discovered dromaeosaur, Cryptovolans, was capable of powered flight, contained a keel and had ribs with uncinate processes. In fact, Cryptovolans makes a better "bird" than Archaeopteryx which is missing some of these modern bird features. Because of this, some paleontologists have suggested that dromaeosaurs are actually basal birds whose larger members are secondarily flightless, i.e. dromaeosaurs evolved from birds and not the other way around. Evidence for this theory is currently inconclusive, but digs continue to unearth fossils (especially in China) of the strange feathered dromaeosaurs. It should be noted that although ornithischian (bird-hipped) dinosaurs share the same hip structure as birds, birds actually originated from the saurischian (lizard-hipped) dinosaurs, and thus arrived at their hip structure condition independently. In fact, the bird-like hip structure developed a third time among a peculiar group of theropods, the Therizinosauridae. Modern birds are classified in Neornithes, which are split into the Paleognathae and Neognathae. The paleognaths include the tinamous (found only in Central and South America) and the ratites. The ratites are large flightless birds, and include ostriches, cassowaries, kiwis and emus; some scientists suspect that the ratites represent an artificial grouping of birds which have independently lost the ability to fly, others contend that the ratites never had the ability to fly and are more directly related to the dinosaurs. The basal divergence from the remaining Neognathes was that of the Galloanseri, the superorder containing the Anseriformes (ducks, geese and swans), and the Galliformes (the pheasants, grouse, and their allies). See the chart. The classification of birds is a contentious issue. Sibley & Ahlquist's Phylogeny and Classification of Birds (1990) is a landmark work on the classification of birds (although frequently debated and constantly revised). Evidence for the various orders seems to be fairly good, but the relationships between the orders are in a state of disarray. Evidence from modern bird anatomy, fossils and DNA have all been brought to bear on the problem but no strong consensus has emerged. See also: Sibley-Ahlquist taxonomy.

Reproduction

Although most male birds have no external sex organs, the male does have two testes which become hundreds of times larger during the breeding season to produce sperm. The female's ovaries also become larger, although only the left ovary actually functions. In the males of species without a phallus (see below), sperm is stored within the proctodeum compartment within the cloaca prior to copulation. During copulation, the female moves her tail to the side and the male either mounts the female from behind or moves very close to her. He moves the opening of his cloaca, or vent, close to hers, so that the sperm can enter the female's cloaca, in what is referred to as a cloacal kiss. This can happen very fast, sometimes in less than one second. The sperm is stored in the female's cloaca for anywhere from a week to a year, depending on the species of bird. Then, one by one, eggs will descend from the female's ovaries and become fertilized by the male's sperm, before being subsequently laid by the female. The eggs will then continue their development in the nest. cloacal kiss.]] Many waterfowl and some other birds, such as the ostrich and turkey, do possess a phallus. Except during copulation, it is hidden within the proctodeum compartment within the cloaca, just inside the vent. The avian phallus differs from the mammalian penis in several ways, most importantly in that it is purely a copulatory organ and is not used for dispelling urine. After the eggs hatch, parent birds provide varying degrees of care in terms of food and protection. Precocial birds can care for themselves independently within minutes of hatching; altricial hatchlings are helpless, blind, and naked, and require extended parental care. The chicks of many ground-nesting birds such as partridges and waders are often able to run virtually immediately after hatching; such birds are referred to as nidifugous. The young of hole-nesters, on the other hand, are often totally incapable of unassisted survival. "Fledging" is the process of a chick acquiring feathers until it can fly. Some birds, such as pigeons, geese, and Red-crowned Cranes, remain with their mates for life (or for a long period) and may produce offspring on a regular basis.

Mating systems and parental care

Sources for this section include:
- Gowaty, Patricia Adair: Male Parental Care and Apparent Monogamy among Eastern Bluebirds (Sialia Sialis). The American Naturalist 121(2): 149-160 (1983).
- Ketterson, Ellen D. and Nolan, Val: Male Parental Behavior in Birds. Annual Review of Ecology and Systematics 25: 601-28 (1994).
- Zeveloff, Samuel and Boyce, Mark: Parental Investment and Mating Systems in Mammals. Evolution 34(5): 973-982 (1980).

The three predominant mating systems are polyandry, polygyny, and monogamy. Monogamy is seen in approximately 91% of all bird species. Polygyny constitutes 2% of all birds and polyandry is seen in less than 1%. Monogamous species of males and females pair for the breeding season. In some cases, the individuals may pair for life. One reason for the high rate of monogamy among birds is due to the fact that male birds are just as adept at parental care as females. In most groups of animals, male parental care is rare, but in birds it is quite common; it is more extensive in birds than in any other vertebrate class. In fact, male care can be seen as important or essential to female fitness. "In one form of monogamy such as with obligate monogamy a female cannot rear a litter without the aid of a male" (Gowaty, 1983). obligate The parental behavior most associated with monogamy was male incubation. This is very interesting, because male incubation is the most confining male parental behavior. It not only consumes time, but also may require physiological changes that interfere with usual mating. With the extreme loss of mating opportunities, there is a reduction in the reproductive success among males. "This information then suggests that sexual selection may be less intense in taxa where males incubate, hypothetically because males allocate more effort to parental care and less to mating" (Ketterson and Nolan, 1994). It is understood then that the females associated with these males base their choice of mate on parental behaviors rather than physical appearance.

Respiration

Birds respire by means of crosscurrent flow: the air flows at a 90° angle to the flow of blood in the lungs' capillaries. In addition to the lungs themselves, birds have posterior and anterior air sacs (typically nine) which control air flow through the lungs, but do not play a direct role in gas exchange. There are three parts involved in respiration:
- the anterior air sacs (interclavicular, cervicals, and anterior thoracics),
- the lungs, and
- the posterior air sacs (posterior thoracics and abdominals). It takes a bird two full breaths, to completely cycle the air from each inhalation through the lungs and out again. The air flows through the air sacs and lungs as follows:
- First inhalation: air flows through the trachea and bronchi into the posterior air sacs.
- First exhalation: air flows from the posterior air sacs to the lungs.
- Second inhalation: air flows from the lungs to the anterior air sacs.
- Second exhalation: air flows from the anterior sacs back through the trachea and out of the body. Since during inhalation and exhalation fresh air flows through the lungs in only one direction, birds are able to diffuse more oxygen into their blood. Unlike humans and other mammals, there is no mixing of oxygen rich air and carbon dioxide rich air. Thus, the partial pressure of oxygen in a bird's lungs is the same as the environment. This is why you would more likely see a bird on Mount Everest than, say, a mouse. Avian lungs do not have alveoli, as mammalian lungs do, but instead contain millions of tiny passages known as parabronchi, connected at either ends by the dorsobronchi and ventrobronchi. Air flows through the honeycombed walls of the parabronchi and into air capillaries, where oxygen and carbon dioxide are traded with cross-flowing blood capillaries by diffusion.

Other anatomy

mouse Birds possess a ventriculus, or gizzard, that is composed of four muscular bands that act to rotate and crush food by shifting the food from one area to the next within the gizzard. Depending on the species, the gizzard may contain small pieces of grit or stone that the bird has swallowed to aid in the grinding process of digestion. For birds in captivity, only certain species of birds require grit in their diet for digestion. The use of gizzard stones is a similarity between birds and dinosaurs, which left gizzard stones called gastroliths as trace fossils. Birds also have skeletons possessing unique characteristics. See bird skeleton. The region between the eye and bill on the side of a bird's head is called a lore. This region is sometimes featherless, and the skin may be tinted (as in many species of the cormorant family).

Birds and humans

cormorant cormorant cormorant Birds are an important food source for humans. The most commonly eaten species is the domestic chicken and its eggs, although geese, pheasants, turkeys, and ducks are also widely eaten. Other birds that have been utilized for food include emus, ostriches, pigeons, grouse, quails, doves, woodcocks, songbirds, and others, including small passerines such as finches. At one time swans and flamingos were delicacies of the rich and powerful, although these are generally protected now. Many species have become extinct through over-hunting, such as the Passenger Pigeon, and many others have become endangered or extinct through habitat destruction, deforestation and intensive agriculture being common causes for declines. Numerous species have come to depend on human activities for food and are widespread to the point of being pests. For example the common pigeon or Rock Dove (Columba livia) thrives in urban areas around the world. In North America, introduced House Sparrows, Common Starlings, and House Finches are similarly widespread. Other birds have been used by humans: for example Homing pigeons to carry messages (many are still kept for sport), falcons for hunting, cormorants for fishing. Chickens and pigeons are popular subjects in experimental research in biology and comparative psychology. As birds are extra-sensitive to toxins, the Canary was often used in coal mines to indicate the presence of poisonous gases, so that the miners could escape. Colorful, particularly tropical, birds (e.g., parrots, and mynahs) are often kept as pets although this has led to smuggling of some endangered species; CITES does considerable work to deter this. Bird diseases that can be contracted by humans include these: psittacosis, salmonellosis, campylobacteriosis, Newcastle's disease, mycobacteriosis (avian tuberculosis), avian influenza, giardiasis, and cryptosporiadiosis.

Trivia

- To preen or groom their feathers, birds use their bills to brush away foreign particles.
- The birds of a region are called the avifauna.
- Few birds use chemical defences against predators. Tubenoses can eject an unpleasant slime against an aggressor, and some species of pitohui, found in New Guinea secrete a powerful neurotoxin in their feathers.
- Birds are among the most extensively studied animal groups, with hundreds of academic journals devoted to their study.

References and external links

- [http://www.bsc-eoc.org/avibase/avibase.jsp?lang=EN&pg=home Avibase - The World Bird Database]
- [http://www.i-o-c.org/IOComm/index.htm International Ornithological Committee]
- [http://www.birdlife.org/ Birdlife International] - Dedicated to bird conservation worldwide; has a database with about 250,000 records on endangered bird species
- [http://birdingonthe.net/ Birdingonthe.net]
- [http://www.surfbirds.com/ Surfbirds Birdwatching and World Birding]
- [http://worldtwitch.com/ Worldtwitch - rare bird news around the world]
- [http://www.birdforum.net/ BirdForum] Category:Chordates
- Category:Ornithology ko:새 ms:Burung ja:鳥類 simple:Bird th:นก

Biped

A biped is an animal that travels across surfaces supported by two legs.

Bipedalism in general

Bipedal locomotion is walking, running, and standing on two legs (as opposed to four). It is a process requiring complex interaction of mechanical and control-system characteristics. Humans are capable of performing such motion because their spines are s-curved and their heels are round. Whether such a system has evolved in an animal species or been engineered in a robot, many of the same issues are inevitably involved. Energy-efficient means of standing bipedally involve constant adjustment of balance, and of course these must avoid overcorrection. Efficient walking complicates these issues, as it entails tipping slightly off-balance forward and to the side, and correcting balance with the right timing. Running is an inherently continuous process, in contrast to walking; a bipedal creature or device, when efficiently running, is in a constant state of falling forward, that is maintained as relatively smooth motion only by repeatedly "catching oneself" with, again, the right timing, but in the case of running only delaying the nearly inevitable fall for the duration of another step. The phenomenon of "tripping" is also informative in this regard. One popular way to think of it is as having one's leg pulled out from under them. In fact, however, merely stopping the movement of one leg of a walker, and merely slowing one leg of a runner, is sufficient to amount to tripping them. They were already falling, and preventing the tripped leg from aborting that fall is sufficient to literally "drop them like a sack of dirt". Engineers who study bipedal walking describe it as a repeatedly interrupted fall.

Animals and humans

Many animals, including humans, have evolved bipedalism, with anatomical adaptations constituting the required mechanical systems and neurological adaptations the control-system ones. As to anatomy, contrast in domesticated poultry the meaty drumstick and thigh, against measures like the assertive flavors that Buffalo-wing recipes use to "dress up" the small and bony wing. The technique of power-lifters highlights the similar difference in dimensions, even in untrained humans, between the muscles of the thigh and the upper arm. This difference is extreme: the large muscle in the human upper arm is the biceps, which bends the arm at the elbow; few people know the name of, or pay any attention to, the muscle that is used to straighten the arm; the quadriceps and hamstring muscles of the thigh are both so crucial to bipedal activities, that each alone is much larger than even a well-developed biceps. The famous knee jerk (or patellar reflex) emphasizes the necessary bipedal control system: the only function served by the nerves involved being connected as they are is to ensure quick response to imminent disturbance of erect posture; it not only occurs without conscious mental activity, but also involves none of the nerves which lead from the leg to the brain. A less well-known aspect of bipedal neuroanatomy can be demonstrated in human infants who have not yet developed toward the ability to stand up. They can nevertheless run with great dexterity, provided they are supported in a vertical position and offered the stimulus of a moving treadmill beneath their feet. Human walking is composed of several separate processes:
- rocking back and forth between feet
- pushing with the toe to maintain speed
- combined intruption in rocking and ankle twist to turn
- shortening and extending the knees to prolong the "forward fall"

Evolution of bipedalism

Bipedalism and associated traits can offer a species several advantages:
- Some evolutionary biologists have suggested that a crucial stage in the evolution of some or all bipeds was the ability to stand, which generally improves the ability to see (and perhaps otherwise detect) distant dangers or resources.
- In vertebrate species, for whom evolution of additional limbs would be an enormous genetic change, it can serve to free the front limbs for such other functions as manipulation (in primates) and flight (in birds).
- In some species with predominantly prone locomotion and often inability to stand erect while stationary, bipedal behavior appears only for rapid motion, "rearing up" on their hind legs.
- Humans are generally thought to have evolved bipedalism either through living on plains (the Savanna Theory), or wading like their semi-bipedal wading cousins the bonobo chimps and proboscis monkeys, the Aquatic Ape Theory. Many animals that do not use bipedal locomotion in nature can be trained to walk on hind legs. This includes dogs, elephants, horses and pretty much every mammal or reptile that have 4 legs. Some animals can also be trained to walk on front limbs, although this method lacks any practical benefits. Humans too, can learn to walk using their arms (this can be painful, however). Primates usually use both forms of locomotion - bipedal and walking on all fours, though there has been one recorded case of a macaque switching to bipedal walking completely after recovering from a serious illness, and at least one example of a captive chimp who only walked upright.

Bipedal biological taxa

Biological examples of bipedality beyond humans and other primates are mostly vertebrates. Birds are bipeds, whether flying or ratite, and the ostrich and kin demonstrate that not even large bipeds have to be mammals. Another mammalian group of bipeds are the kangaroos. The pattern of bipedality only in the form of "reared-up" running can be seen in some of the cockroaches, and in at least one genus of lizard (the basilisk lizards) that can run across the surface of water. A biped also has the ability to breath whilst it runs. Humans usually take a breath every other stride when their aerobic system is functioning. During a sprint, at which point the anaerobic system kicks in, breathing slows until the anaerobic system can no longer sustain a sprint. Bipeds are almost exclusively terrestrial animals, perhaps because the advantages of erect motion are offset, for aquatic animals, by the greater resistance to motion, in dense and somewhat viscous water in contrast to air, incurred by presenting a large cross-sectional area perpendicular to the direction of motion. Obvious exceptions to this rule include several animals which are partially bipedal, semi-aquatic mammals, including the bonobo and proboscis, and also the raccoon, which does not walk on its hind feet but often stands erect, or squats in water to use its hands to manipulate food and rocks/sticks. Another bird which exhibits a bipedal posture is the penguin, whose efficiency in water is far greater than that on land; noticeable in the way it walks. At least two types of octopus are known to walk bipedally. This form of locomotion appears to allow them to remain somewhat camouflaged while moving quickly.

Robots

For nearly the whole of the 20th century, bipedal robots were very difficult to construct. Robots which could move usually did so using wheels, treads, or multiple legs. Increasingly cheap and compact computing power, however, has made two-legged robots more feasible. In recent years, Honda and Sony have developed these machines.

External link

- [http://news.nationalgeographic.com/news/2004/09/0902_040902_upright_hominid.html#main Study pushes bipedalism back 2 million years]
- [http://www.world.honda.com/HDTV/ASIMO/200412-run/index.html Video of Honda's humanoid robot Asimo running] (Dec 16 2004) (see also Asimo) category:Transportation
- [http://ist-socrates.berkeley.edu/~chuffard/index_files/Bipedal_octopuses.htm] Information about bipedal octopuses, with link to original paper and videos

Homeothermic

Warm-blooded is an archaic term used to describe an animal that keeps its core body temperature at a nearly constant level regardless of the temperature of the surrounding environment (that is, to maintain thermal homeostasis). This can involve not only the ability to generate heat, but also the ability to cool down. Warm-blooded animals control their body temperature by regulating their metabolic rates (e.g. increasing their metabolic rate as the surrounding temperature begins to decrease). Thanks to more thorough research in the field of animal physiology, scientists have come to realize that body temperature types do not easily fit a simple either/or scenario. Body temperature maintenance incorporates a wide range of different techniques that result in a body temperature spectrum, with the traditional ideals of warm blooded and cold-blooded being at opposite extremes. Because of the generalness of the terms, as well as an increased understanding in this field, both warm blooded and cold-blooded have mostly fallen out of favour. They have since been replaced with one, or more, of their variants (see: #Breaking down Warm Bloodedness).

Breaking down Warm Bloodedness

Warm bloodedness generally refers to three separate aspects of thermoregulation. #Endothermy #Homeothermy #Tachymetabolism
- Endothermy - This term refers to creatures that are able to control their body temperatures through internal means such as muscle shivering, fat burning, and panting (Greek: endo = "within," therm = "heat").
- Homeothermy - A term used to define a creature that maintains a stable internal body temperature regardless of external influence. This temperature is often higher than the immediate environment (Greek: homoios = "same, identical," therm = "heat").
- Tachymetabolism - A term used for creatures that maintain a high resting metabolism (Greek: tachy = "fast, swift," metabol = "to change"). Tachymetabolic creatures are, essentially, "on" all the time. Though their resting metabolism is still many times slower than their active metabolism, the difference is often not as large as that seen in bradymetabolic creatures. Tachymetabolic creatures have a harder time dealing with a scarcity of food. A large proportion of the creatures traditionally called "Warm Blooded" (namely mammals and birds) fit all three of these categories. Over the past 30 years, studies in the field of animal thermophysiology has shown that there are still quite a few members of these two groups that don't fit all this criteria (e.g. many bats and small birds are poikilothermic and bradymetabolic when they sleep for the night, or day). For creatures such as these, another term was coined: heterothermy. Further studies on animals that were traditionally assumed to be cold-blooded have shown that most creatures incorporate different variations of the three terms defined above, along with their counterparts (ectothermy, poikilothermy and bradymetabolism). Thus creating a broad spectrum of body temperature types (see #In between cold and warm blooded).

Mechanisms

Endotherms include birds and mammals. The advantages of endothermy are increased enzyme activity and a constant body temperature, allowing these animals to be active in cold temperatures. On the other hand, the disadvantage is the need to maintain thermoregulation, even during inactivity, otherwise the organism will die.
Other living creatures such as fish and reptiles are called ectothermic or cold blooded, meaning that they cannot control their internal temperature and so were assumed to have the same temperature as their surroundings. In winter, there may not be enough food to enable an endotherm to keep its metabolic rate stable all day, so some organisms go into a controlled state of hypothermia called hibernation, or torpor. This deliberately lowers the body temperature to conserve energy. In hot weather, endotherms expend considerable energy to avoid overheating: they may pant, sweat, lick, or seek shelter or water. Diverse mechanisms can come into play to regulate body temperature such as shivering (to generate heat from muscle contractions), blanching (circulatory changes to direct less heat to the skin), flushing (circulatory changes to radiate more heat from the skin), panting or sweating (to increase heat loss through evaporation).

Warm-blooded versus cold-blooded

Biochemical processes are heat dependent. The rule of thumb is that they go faster when they are warm and slower when they are cold. The advantage of being homeothermic is that you can always maintain yourself near one optimum temperature and you will now have all your internal chemical reactions functioning at their best. This means that you can think, move, digest, etc. with your best possible speed and efficiency. Warm blooded animals warm themselves by digesting food. The disadvantage of being warm blooded is that you must always consume large amounts of food energy. Once you get accustomed to being warm blooded you are committed to it. When the core temperature of a warm blooded animal does change, even by a few degrees, the animal will rapidly lose its ability to function. The advantage of being cold blooded is that an organism needs much less food. This means that it can survive famine, long ocean voyages, and shortage of prey when warm blooded organisms would surely die. The disadvantage of being cold blooded is that an organism needs to have multiple chemical pathways available to it, some of them for cooler temperature functioning, others for warm. Such an organism may also find itself moving or thinking more slowly than normal, simply because the temperature is colder.

Between cold and warm blooded

It has been a while since the original distinction was made between warm and cold blooded animals. Time has passed, science has advanced, the warm cold business has been studied in closer detail. It turns out that the cold blooded animals all use behavioral means to adjust their temperatures, sometimes quite effectively. There are also creatures that do not properly fall into either category. Some examples of in between creatures include:
- Tuna and Swordfish. Fish have long been thought to be cold blooded. Tuna and swordfish dive deep into the ocean to where the water is quite cold. Swordfish are able to raise the temperature of their brains and eyes in cold water, allowing for faster eye movements when hunting. Tuna are able to warm their entire bodies through a heat exchange mechanism called the rete mirabile, which helps keep heat inside the body, and prevents the loss of heat through the fish's gills into the cold water. As well as having their active muscles for swimming near the center of their body instead of closer to the cold surface.
- Bees. An individual bee is perfectly cold blooded. Bees, however, do not live by themselves. In summer if the nest starts to overheat they will go to the entrances to the nest and fan air in and out of the nest to cool it. In winter if the nest becomes too cold, they will shiver their wing muscles until they grow warm from their efforts. Any one bee doing this by itself would just get tired for no reason. Done collectively, this will raise the temperature of the nest.
- Skunk Cabbage. Plants are normally thought of as having the exact same temperature as their surroundings. The skunk cabbage uses chemical means to warm itself at the end of winter. The warming is modest by animal standards, but is enough to enable them to get an early start in the spring. This permits them to start growing while all their predators and competition are still asleep because of the cold.

References

- Mark Blumberg (2002), , Harvard University Press

External links

- [http://www.earthlife.net/mammals/warm.html www.earthlife.net]
- [http://www.dinosauria.com/jdp/misc/blood.htm Dinosauria.com: What is Warm-bloodedness anyway?]
- [http://reptilis.net/cold-blood.html The Reptipage: What is cold-blooded?] Category:animal physiology ja:恒温動物

Feather

---- Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds. They are the outstanding characteristic that distinguishes the Class Aves from all other living groups. Other Theropoda also had feathers (see Feathered dinosaurs).

Characteristics

Feathers are among the most complex structural organs found in vertebrates: integumentary appendages, formed by controlled proliferation of cells in the epidermis, or outer skin layer, that produce keratin proteins. The β-keratins in feathers, beaks and claws — and the claws, scales and shells of reptiles — are composed of protein strands hydrogen-bonded into β-pleated sheats, which are then further twisted and crosslinked by disulfide bridges into structures even tougher than the α-keratins of mammalian hair, horns and hooves. Feathers insulate birds from water and cold temperatures. Individual feathers in the wings and tail play important roles in controlling flight. These have their own identity and are not just randomly distributed. Although feathers are light, a bird's plumage weighs two or three times more than its skeleton, since many bones are hollow and contain air sacks. Colour patterns serve as camouflage against predators for birds in their habitats, and by predators looking for a meal. As with fish, the top and bottom colors may be different to provide camouflage during flight. Striking differences in feather patterns and colours are part of the sexual dimorphism of many bird species and are particularly important in selection of mating pairs. The remarkable colors and feather sizes of some species have never been fully explained. There are two basic types of feather: vaned feathers which cover the exterior of the body, and down feathers which are underneath the vaned feathers. The pennaceous feathers are vaned feathers. Also called contour feathers, pennaceous feathers are distributed over the whole body. Some of them are modified into remiges, the flight feathers of the wing, and rectrices, the flight feathers of the tail. A typical vaned feather features a main shaft, called the rachis. Fused to the rachis are a series of branches, or barbs; the barbs themselves are also branched and form the barbules. These barbules have minute hooks called barbicels for cross-attachment. Down feathers are fluffy because they lack barbicels, so the barbules float free of each other, allowing the down to trap much air and provide excellent thermal insulation. At the base of the feather, the rachis expands to form the hollow tubular calamus, or quill, which inserts into a follicle in the skin. skin A bird's feathers are replaced periodically during its life through molting, new feathers are formed through the same follicle from which the old ones were fledged. Some birds have a supply of powder-down feathers which grow continuously, with small particles regularly breaking off from the ends of the barbules. These particles produce a powder that sifts through the feathers on the bird's body and acts as a waterproofing agent and a feather conditioner. Most waterbirds produce a large amount of powder down. Waterproofing can be lost by exposure to emulsifying agents due to human pollution. Feathers can become waterlogged and birds may sink. It is also very difficult to clean and rescue birds whose feathers have been fouled by oil spills. Bristles are stiff, tapering feathers with a large rachis but few barbs. Rictal bristles are bristles found around the eyes and bill. They serve a similar purpose to eyelashes and vibrissae in mammals.

Origins

Feathers most likely originated as a filamentous insulation structure, or possibly as markers for mating, with flight emerging only as a secondary purpose. It had been thought that feathers evolved from the scales of reptiles, but recent research casts doubt on this homology (see Quarterly Review of Biology 77:3 (September 2002): 261-95). Experiments show that the same protein (when missing before birth) that causes bird feet to stay webbed, causes reptile scales to become feathers. [http://www.dinosauria.com/jdp/archie/scutes.htm]

Feathered dinosaurs

Main article: Feathered dinosaurs Although birds use feathers primarily for flight, several dinosaurs have been discovered with feathers on their limbs that would not have functioned for flight. One theory is that feathers originally developed on dinosaurs as a means of insulation; those small dinosaurs that then grew longer feathers may have found them helpful in gliding, which would have begun the evolutionary process that resulted in some proto-birds like Archaeopteryx and Microraptor zhaoianus. Other dinosaurs discovered with feathers include Pedopenna daohugouensis, Sinosauropteryx, and Dilong paradoxus. Currently the question is whether birds are deinonychosaurians or dromaeosaurids, not whether birds are dinosaurs. It has been suggested that Pedopenna is older than Archaeopteryx, however, their age remains doubted by some experts. Dilong is a tyrannosauroid which predates Tyrannosaurus rex by 60 to 70 million years.

Human uses

Feathers are both soft and excellent at trapping heat; thus, they are sometimes used in high-class bedding, especially pillows, blankets, and mattresses. They are also used as filling for winter clothing, such as quilted coats and sleeping bags; goose down especially has great loft, the ability to expand from a compressed, stored state to trap large amounts of compartmentalized, insulating air. Bird feathers have long been used for fletching arrows and in the past were used for ink pens. They have also been put to use as sexual aids; see feather dancing. Colorful feathers such as those belonging to pheasants have been used in the past to decorate hats and fishing lures. Eagle feathers have great cultural value to American Indians. Various birds and their plumages serve as cultural icons throughout the world, from the hawk in ancient Egypt to the bald eagle and the turkey in the United States. In Greek mythology, Icarus tried to escape his prison by attaching feathered wings to his shoulders with wax, which melted near the Sun.

References

Category:Animal products ja:羽根

Wing

:For some other uses of the word "wing" please see Wing (disambiguation). Wing (disambiguation).]] Wing (disambiguation) A wing is a surface used to produce an aerodynamic force normal to the direction of motion by travelling in air or another gaseous medium, facilitating flight. It is a specific form of airfoil. The first use of the word was for the foremost limbs of birds, but has been extended to include other animal limbs and man-made devices. A wing is an extremely efficient device for generating lift. Its aerodynamic quality, expressed as a Lift-to-drag ratio, can be up to 60 on some gliders and even more. This means that a significantly smaller thrust force can be applied to propel the wing through the air in order to obtain a specified lift.

Use

The most common use of wings is to fly by deflecting air downwards to produce lift, but upside-down wings are also commonly used as a way to produce downforce and hold objects to the ground (for example racing cars). A sailing boat moves by using its sails as wings to produce lift (in the horizontal plane) from the force of the wind.

Artificial wings

Terms used to describe aeroplane wings

Image:Aircraft wing flaps small dsc06830.jpg|Flaps partially deployed Image:Aircraft wing flaps full dsc06835.jpg|Full flaps Image:Aircraft wing flaps full airbrakes dsc06838.jpg|Full flaps, with airbrakes and spoilers deployed for ground braking
- Leading edge: the front edge of the wing
- Trailing edge: the back edge of the wing
- Span: distance from wing tip to wing tip
- Chord: distance from wing leading edge to wing trailing edge, usually measured parallel to the long axis of the fuselage
- Aspect ratio: ratio of span to standard mean chord
- Aerofoil (or Airfoil in US English): the shape of the top and bottom surfaces when viewed as cross sections cut from leading edge to trailing edge.
- Sweep angle: the angle between the perpendicular to the design centreline of the wing in the wing plane, and either the leading edge or 1/4 chord line.
- Twist: gradual change of the airfoil (aerodynamic twist) and/or angle of incidence of the wing cross-sections (geometrical twist) along the span.

Design features

Aeroplane wings may feature some of the following:
- A rounded (rarely sharp) leading edge cross-section
- A sharp trailing edge cross-section
- Leading-edge devices such as slats, slots, or extensions
- Trailing-edge devices such as flaps
- Ailerons (usually near the wingtips) to provide roll control
- Spoilers on the upper surface to disrupt lift and additional roll control
- Vortex generators to help prevent flow separation
- Wing fences to keep flow attached to the wing
- Dihedral, or a positive wing angle to the horizontal. This gives inherent stability in roll. Anhedral, or a negative wing angle to the horizontal, has a destabilising effect
- Folding wings allow more aircarft to be carried in the confined space of the hangar of an aircraft carrier.

Wing types

- Swept wings are wings that are bent back at some angle, instead of sticking straight out from the fuselage.
- Forward-swept wings are high performance wings that are bent forward, the reverse of a traditional swept wing. Forward swept wings are also used in some two seat gliders.
- Elliptical wings (technically wings with an elliptical lift distribution) are theoretically optimum for efficiency at subsonic speeds.
- Delta wings have reasonable performance at subsonic and supersonic speeds and are good at high angles of attack.
- Waveriders are efficient supersonic wings that take advantage of shock waves.
- Rogallo wings are two hollow half-cones of fabric, one of the simplest wings to construct.
- Swing-wings (or variable geometry wings) are able to move in flight to give the benefits of dihedral and delta wing. Although they were originally proposed by German aerodynamicists during the 1940s, they are currently only found on some military aircraft such as the Grumman F-14, Panavia Tornado, General Dynamics F-111, B-1 Lancer, Tupolev Tu-160, MiG-23 and Sukhoi Su-24.
- Ring wings are optimally loaded closed lifting surfaces with higher aerodynamic efficiency than planar wings having the same aspect-ratios. Other non planar wing systems display an aerodynamic efficiency intermediate between ring wings and planar wings. Ring wing

Science of wings

The science behind how wings work can be complex and is one of the principal applications of the science of aerodynamics. However at the simplest level, both the upper and lower surfaces of a wing produces lift by deflecting air downward, which propels the flying body upward with an equal and opposite force (see Newton's Third Law). The air is deflected downwards because of Bernoulli's principle. This relates the pressure of air to its local velocity. If the velocity of the air changes as it flows around an object, such as a wing, the pressure of the air also changes. The shape and the angle of attack of the wing causes the air to flow faster above the wing than below, and so the pressure above the wing is less than below the wing. This pressure difference causes a force, called lift that acts at right angles to the air-flow. The science of wings applies in other areas beyond conventional fixed-wing aircraft, including:
- Helicopters which use a rotating wing with a variable pitch or angle to provide a directional force
- The space shuttle which uses its wings only for lift during its descent
- Formula One cars which use upside-down wings to give cars greater adhesion at high speeds
- Sailing boats which use sails as vertical wings with variable fullness and direction to move across water. Structures with the same purpose as wings, but designed to operate in liquid media, are generally called fins or hydroplanes, with hydrodynamics as the governing science. Applications arise in craft such as hydrofoils and submarines. Interestingly sailing boats use both fins and wings.

Evolution of wings in animals

Biologists believe that animal wings evolved at least four separate times, an example of convergent evolution. Insect wings are believed to have evolved about 300 million years ago, pterosaur wings about 225 million years ago, bird wings about 150 million years ago, and bat wings about 55 million years ago. Wings in these groups are analogous structures because they evolved independently rather than being passed from a common ancestor. See also flight.

External links

- [http://www.av8n.com/how/ An Excellent treatment of why and how wings generate lift]
- [http://www.npr.org/templates/story/story.php?storyId=3875411 Demystifying the Science of Flight] - Audio segment on NPR's Talk of the Nation Science Friday
- [http://www.grc.nasa.gov/WWW/K-12/airplane/short.html NASA's explanations and simulations]
- [http://aerodyn.org/Wings/ Advanced Topics in Aerodynamics] Wings for all speeds
- [http://www.nurseminerva.co.uk/adapt/evolutio.htm Evolution of flight] in animals
- [http://jef.raskincenter.org/published/coanda_effect.html Explanation invoking Coanda Effect] Category:Aerospace engineering Category:Aerodynamics Category:Aircraft components ja:翼

Ostrich

The ostrich (Struthio camelus) is a flightless bird native to Africa. It is the only living species of its family, Struthionidae, and its genus, Struthio. They are distinct in their appearance, with a long neck and legs and the ability to run at speeds of about 65 km/h (40 mph). Ostriches are considered the largest living species of bird and are farmed all over the world. The scientific name for the ostrich is from the Greek for "sparrow camel."

Description

Ostriches usually weigh from 90 to 130 kg (198 to 286 pounds), although some male ostriches have been recorded with weights of up to 155 kg (342 pounds). The feathers of adult males are mostly black, with some white on the wings and tail. Females and young males are grayish-brown, with a bit of white. The small vestigial wings are used by males in mating displays. They can also provide shadow to chicks. The feathers are soft and serve as insulation, and are quite different from the stiff airfoil feathers of flying birds. There are claws on two of the wings' fingers. The strong legs of the ostrich lack feathers. The bird stands on two toes, with the bigger one resembling a hoof. This is an adaption unique to ostriches that appears to aid in running. The eyes of ostriches with their thick black eyelashes are the biggest eyes of all living land animals. Ostrichs are bilaterally symmetric and endothermic. At sexual maturity (two to four years old), male ostriches can be between 1.8 m (6 feet) and 2.7 m (9 feet) in height, while female ostriches range from 1.7 m (5.5 feet) to 2 m (6.5 feet). During the first year of life, chicks grow about 25.4 cm (10 inches) per month. At one year, ostrichs weigh around 45.5 kg (100 pounds).

Classification and distribution

endothermic] endothermic Ostriches occur naturally on the savannas and Sahel of Africa, both north and south of the equatorial forest zone. The species belong to the Struthioniformes order (ratites). Other members of this group include rheas, emus, cassowaries and the largest bird ever, the now-extinct Aepyornis. Five subspecies are recognized:
- S.c. australis in Southern Africa
- S.c. camelus in North Africa, sometimes called the North African ostrich or red-necked ostrich.
- S.c. massaicus in East Africa, sometimes called the Masai ostrich. During the mating season, the male's neck and thighs turn pink-orange. Their range is from Ethiopia and Kenya in the east to Senegal in the west, and from eastern Mauritania in the north to southern Morocco in the south.
- S.c. molybdophanes in Somalia, Ethiopia, and northern Kenya, sometimes called the Somali ostrich. During the mating season, the male's neck and thighs turn blue. Its range overlaps with S.c. massaicus in northeastern Kenya. Some authorities consider the Somali Ostrich a full species. According to someone from singapore, a researcher by the name of Koh Liquan states that an Ostrich egg is a single cell. Hence forth all cell theory has been modified to integrate a 5th theory, 'Ostrich egg is the largest unicellular egg found in the world.
- S.c. syriacus in the Middle East, sometimes called the Arabian ostrich or Middle Eastern ostrich, was a subspecies formerly very common in the Arabian Peninsula, Syria, and Iraq; it became extinct around 1940.

Behavior

Ostriches live in nomadic groups of 5 to 50 birds that often travel together with other grazing animals, such as zebras or antelopes. They mainly feed on seeds and other plant matter; occasionally they also eat animals such as locusts. Lacking teeth, they swallow pebbles that help to grind the swallowed foods in the gizzard. They can go without water for a long time, exclusively living off the moisture in the ingested plants. However, they enjoy water and frequently take baths. With their acute eyesight and hearing, they can sense predators such as lions from far away. In popular mythology, the ostrich is famous for hiding its head in the sand at the first sign of danger. The Roman writer Pliny the Elder is noted for his descriptions of the ostrich in his Naturalis Historia, where he describes the ostrich and the fact that it hides its head in a bush. There have been no recorded observations of this behavior. A common counter-argument is that a species that displayed this behavior would not likely survive very long. The myth may have resulted from the fact that, from a distance, when ostriches feed they appear to be burying their head in the sand because they deliberately swallow sand and pebbles to help grind up their food. When lying down and hiding from predators, the birds are known to lay their head and neck flat on the ground. When threatened, ostriches run away, but they can also seriously injure with kicks from their powerful legs.

Reproduction

Naturalis Historia Naturalis Historia thumb Ostriches become sexually mature when 2 to 4 years old; females mature about six months earlier than males. The species is iteroparous, with the mating season beginning in March or April and ending sometime before September. The mating process differs in different geographical regions. Territorial males will typically use hisses and other sounds to fight for a harem of 2 to 5 females (which are called hens). The winner of these fights will breed with all the females in an area but only form a pair bond with one, the dominant female. The female cowers on the ground and is mounted from behind by the male. Ostriches are oviparous. The females will lay their fertilized eggs in a single communal nest, a simple pit scraped in the ground and 30 to 60 cm deep. Ostrich eggs can weigh 1.3 kg and are the largest of all eggs (and the largest single cells), though they are actually the smallest eggs relative to the size of the bird. The nest may contain 15 to 60 eggs, with an average egg being 15.2 cm (6 inches) long, 12.7 cm (5 inches) wide, and weigh 1.4 kg (3 pounds). They are shiny and whitish in color. The eggs are incubated by the females by day and by the male by night, making use of the different colors of the two sexes to escape detection. The gestation period is 35 to 45 days. Typically, the male will tend to the hatchlings. The life span can extend from 30 to 70 years, with 50 being typical.

Ostriches and humans

life span In the past, ostriches were mostly hunted and farmed for their feathers, which used to be very popular as ornaments in ladies' hats and such. Their skins were also valued to make a fine leather. In the 18th century, they were almost hunted to extinction; farming for feathers began in the 19th century. The market for feathers collapsed after World War I,but commercial farming for feathers and later for skins,took off during the 1970's. The ostriches in Arabia and Southwest Asia were hunted to extinction by the middle of the 20th century. Today, ostriches are bred all over the world, including climates as cold as that of Sweden. Considering they will prosper in climates between 30° and -10° it is no wonder that they are farmed in over 50 countries around the world, but the majority is still found in Southern Africa. Since they also have the best feed to weight ratio gain of any land animal (3.5:1 whereas that of cattle is 6:1) in the world, they are bound to appear attractive to farmers. Although they are farmed primarily for leather and secondarily for meat, additional useful byproducts are the eggs, offal, and feathers. It is claimed that ostriches produce the strongest commercially available leather¹. Ostrich meat tastes similar to lean beef and compares favourably, being low in fat and cholesterol. beef Ostriches are large enough for a small human to ride them; typically, the human will hold on to the wings while riding. They have been trained in some areas of northern Africa and Arabia as racing mounts. Ostrich races in the United States have been criticized by animal rights organizations, however there is little possibility of this becoming a widespread practice due to the fact that the animals are difficult to saddle. Ostriches are classified as dangerous animals in Australia, the US and the UK. There are a number of recorded incidents of people being attacked and killed. Big males can be very territorial and aggressive and can attack and kick very powerfully with their legs. An ostrich will easily outrun any athlete.

External link

- [http://www.geocities.com/ostrichwonderland/photos.htm Photos of hatchlings and mating ostriches]
- [http://animaldiversity.ummz.umich.edu/site/accounts/information/Struthio_camelus.html Animal Diversity Web]
- [http://montereybay.com/creagrus/ostrich.html Bird Families of the World]
- [http://www.watchtower.org/library/g/1999/7/22/article_01.htm Fleet-Footed, Flightless, and Fascinating — The Ostrich]

Sources

- [http://www.ostrich-association.co.nz/index.cfm/Facts Ostrich farming facts in New Zealand] ^{Note 1}
- [http://www.honoluluzoo.org/ostrich.htm Honolulu Zoo page on Ostriches]
- [http://www.krugerpark.co.za/africa_ostrich.html Kruger Park page on Ostriches]
- [http://www.saobc.co.za/ South African Ostrich Business Chamber] Category:Heraldic birds Category:Livestock Category:Poultry Category:Ratites Category:Wildlife of Africa ms:Burung Unta ja:ダチョウ

Emu

Dromaius novaehollandiae
Dromaius baudinianus (extinct)
Dromaius ater (extinct) :Note that the acronym EMU has several meanings. The Emu(the 'u' sounds like 'you') (Dromaius novaehollandiae, Latin for "fast-footed New Hollander.") is the largest bird native to Australia and, after the Ostrich, the second-largest bird that survives today. It inhabits most of the less-populated areas of the continent, avoiding only dense forest and severe desert. Like all birds in the Ratite group, it is flightless, although unlike some it does have tiny wings hidden under the feathers. The soft-feathered, brown birds reach 1.5 to 2 metres in height and weigh up to 60 kilograms, with the male marginally smaller. Emus are opportunistically nomadic and follow rain, feeding on grains, flowers, fruit, soft shoots, insects, grubs, and whatever else is available. They are able to travel great distances at a fast, economical trot and, if need be, can sprint at 50 km/h. Three different emu species were common prior to European settlement in 1788:
- The Emu, Dromaius novaehollandiae, remains common in most of the more lightly settled parts of mainland Australia. Overall population varies from decade to decade according to rainfall; as low as 200,000 and as high as a million, but a typical figure is about half a million individuals. Although no longer found in the densely settled southern and south-western agricultural areas, the provision of permanent stock water in arid regions has allowed the mainland species to extend its range. There are three current sub-species or races of the emu across Australia:
- D. novaehollandiae novaehollandiae - South-east Australia - whitish ruff when breeding.
- D. novaehollandiae woodwardi - North Australia - slender, paler.
- D. novaehollandiae rothschildi - South-west Australia - darker, no ruff during breeding.
- D. novaehollandiae diemenensis - Tasmania - The Tasmanian Emu, became extinct around 1850.
- The Kangaroo Island Emu, D. baudinianus became extinct around 1827 as a result of hunting and frequent fires. The larger mainland species was introduced to Kangaroo Island in the 1920s.
- The small King Island Emu D. ater was about half the size of the mainland species. By 1805 it had been hunted to extinction by sealers and visiting sailors.

Breeding

Kangaroo Island They pair in high summer and defend a territory of around 30 square km. Breeding takes place in the cooler months. As the days shorten, males undergo hormonal changes, lose appetite and construct a rough nest in a semi-sheltered hollow on the ground from bark, grass, sticks and leaves. The pair mate every day or two and, every second or third day, the female lays a very large, thick-shelled dark green egg weighing about half a kilogram. The male becomes broody after about the seventh egg and begins sitting. From this time on, he does not eat, drink or defecate, and only stands to turn the eggs, which he does about 10 times a day. For the next eight weeks, he will survive on accumulated body fat and any morning dew he can reach from the nest, losing up to one third of his body weight and become ever-weaker and more dazed. The female usually continues laying but does not mate with the male again after he goes broody. About 8 or 10 eggs is typical but clutches of almost double this size are not uncommon. As with a great many other Australian birds (see Blue Wren), despite the nominal pair-bond, infidelity is the norm: once the male starts brooding, the female mates with other males instead. As many as half the chicks in the brood may be fathered by others. Blue WrenSome females stay and defend the nest until the chicks start hatching but most leave the nesting area completely after a time and often nest again—in a good season a female emu may nest three times. (In the tropical north, where the seasons are reversed and it rains in summer, mating starts just before "the wet", and emus are reliably reported to delay mating if the season is late. The mechanism for this remains unknown.) Despite the determined attention of the male, emu eggs are heavily predated, particularly by goannas, but it is estimated that four out of five chicks that hatch successfully survive to adulthood. Newly hatched chicks are active and can leave the nest within a few days. They stand about 25 cm tall, and have distinctive brown and cream stripes for camouflage, which fade after three months or so. The male stays with the growing chicks for at least six months, defending them and teaching them how to find food. A male emu will often adopt any strange chick found wandering, so long as it is no bigger than his own brood. Chicks grow very quickly (up to a kilogram a week) and are full-grown in 12 to 14 months, but many remain with their family group for another six months or so before they split up to breed in their second season. In the wild, emus live for about 10 years; captive birds can more than double that.

Adaptation

The Ratite group to which emus belong is very old. Emus have been walking the plains of Australia in something reasonably close to their present form for about 80 million years—Old Man Emu was around when the dinosaurs still walked. Emus have evolved a number of adaptions as the continent gradually became less fertile, hotter and dryer. On very hot days, emus pant: they breathe rapidly, using their lungs as evaporative coolers. They can keep it up indefinitely and seem immune to the ill-effects of low blood CO2 levels, but must recharge their fluids by drinking every day. Nevertheless, emus do not waste water: for normal breathing in cooler weather, they have large, multi-folded nasal passages. Cool air warms as it passes through into the lungs, in turn extracting heat from the nasal region. On exhalation, the emu's cold nasal turbinates condense moisture back out of the air and absorb it for reuse. Emu feathers are light in colour except for the dark tips: solar radiation is absorbed by the feather tips, while the loose-packed inner plumage insulates the skin: in combination, the dark and light areas of the plumage deflect or absorb all but 2% of the sun's radiant heat. A unique feature of the emu feather is its double rachis emerging from a single shaft. The emu's steady walking pace of 4 to 7 km/h creates just enough breeze for optimum convective cooling of the hot black outer tips, and emus are thus able to forage right through the heat of the day when nearly all other animals must take shelter. Emus are largely solitary creatures; unlike many other birds, they seem to have no need for company and mutual grooming. They roam the continent searching for the best feeding areas, and although they can form enormous flocks, this is not a truly social behaviour, simply a matter of going where the food is. According to folklore, emus have a mysterious mechanism to tell them where the rain is, and will travel for hundreds of miles to take advantage of a deluge. In fact, they are very keenly attuned to subtle weather cues: particularly the sight of distant cloud formations but probably also the sound of thunder from afar. In Western Australia, emu movements follow a distinct seasonal pattern—north in summer and south in winter—but further east their wanderings are more random. It's nothing unusual for a bird to walk 1000 km in a season, with 10 to 25 km a day being normal. (Male birds with chicks in tow must move more slowly, of course). Emus are also powerful swimmers capable of crossing rivers— something they need to do from time to time as part of their wandering. Generally though, emus prefer to play in water rather than cross it: if a stream or dam is available, they take full advantage of it on hot days, sometimes rolling on their backs and kicking their legs in the air.

Reference

- Underhill D (1993) Australia's Dangerous Creatures, Reader's Digest, Sydney, New South Wales, ISBN 0-86438-018-6 Category:Ratites Category:Birds of Australia Category:Heraldic birds ja:エミュー

Vertebrate

Conodonta
Hyperoartia
:Petromyzontidae (lampreys)
Pteraspidomorphi (early jawless fish)
Thelodonti
Anaspida
Cephalaspidomorphi (early jawless fish)
:Galeaspida
:Pituriaspida
:Osteostraci
Gnathostomata (jawed vertebrates)
:Placodermi
:Chondrichthyes (cartilaginous fish)
:Acanthodii
:Osteichthyes (bony fish)
::Actinopterygii (ray-finned fish)
::Sarcopterygii (lobe-finned fish)
:::Actinistia (coelacanths)
:::Dipnoi (lungfish)
:::Tetrapoda ::::Amphibia
::::Amniota
:::::Sauropsida/(Reptiles)
::::::Aves (Birds)
:::::Synapsida
::::::Mammalia Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. Vertebrates started to evolve about 530 million years ago during the Cambrian explosion, which is part of the Cambrian period (first known vertebrate is Myllokunmingia). The bones of the spinal column (or vertebral column) are called vertebrae. Vertebrata is the largest subphylum of chordates, and contains most animals with which people are generally familiar (except insects). Fish (including lampreys, but traditionally not hagfish, though this is now disputed), amphibians, reptiles, birds, and mammals (including humans) are vertebrates. Additional characteristics of the subphylum are a muscular system that mostly consists of paired masses, as well as a central nervous system which is partly located inside the backbone. The internal skeleton which defines vertebrates consists of cartilage or bone, or in some cases both. The skeleton provides support to the organism during the period of growth. For this reason vertebrates can achieve larger sizes than invertebrates, and on average vertebrates are in fact larger. The skeleton of most vertebrates, that is excluding the most primitive ones, consists of a skull, the vertebral column and two pairs of limbs. In some forms of vertebrates, one or both of these pairs of limbs may be absent, such as in snakes or whales. These limbs have been lost in the course of evolution. The skull is thought to have facilitated the development of intelligence as it protects vital organs such as the brain, the eyes and the ears. The protection of these organs is also thought to have positively influenced the development of high responsiveness to the environment often found in vertebrates. Both the vertebral column and the limbs support the body of the vertebrate overall. This support facilitates movement. Movement is normally achieved with muscles that are attached directly to the bones or cartilages. The contour of the body of a vertebrate is formed by the muscles. A skin covers the inner parts of a vertebrate's body. The skin sometimes acts as a structure for protective features, such as horny scales or fur. Feathers are also attached to the skin. The trunk of a vertebrate is hollow and houses the internal organs. The heart and the respiratory organs are protected in the trunk. The heart is located behind the gills, or where there are lungs, in between the lungs. The central nervous system of a vertebrate consists of the brain and the spinal cord. Both of these are characterized by being hollow. In lower vertebrates the brain mostly controls the functioning of the sense organs. In higher vertebrates the size of the brain relative to the size of the body is larger. This larger brain enables more intensive exchange of information between the different parts of the brain. The nerves from the spinal cord, which lies behind the brain, extend to the skin, the inner organs and the muscles. Some nerves are directly connected to the brain, linking the brain with the ears and lungs. Vertebrates have been traced back to the ostracoderms of the Silurian Period (444 million to 409 million years ago) and the conodonts, a group of eel-like vertebrates characterized by multiple pairs of bony toothplates. All vertebrates have: the ability to form bones; paired, specialised sensory organs and a brain.

External links

- [http://tolweb.org/tree?group=Amniota&contgroup=Terrestrial_vertebrates Tree of Life]
- [http://reference.allrefer.com/encyclopedia/categories/vertz.html Vertebrate Zoology] Category:Chordates ko:척추동물 ms:Vertebrata ja:脊椎動物 simple:Vertebrate th:สัตว์มีกระดูกสันหลัง

Nectar

Nectar may mean:
- Nectar source — in botany, the sugar-rich liquid produced by the flowers of plants in order to attract pollinating animals. It is also the principal raw ingredient of honey. The nectary is the gland that secretes nectar. It is usually located at the base of the flower, forcing pollinators to brush against the flower's reproductive structures to reach it. It is not a modified stamen. Nectar that is produced outside the flower is generally produced to attract predatory insects. They will eat both the nectar and any plant-eating insects around, thus functioning as 'bodyguards'. Some carnivorous plants will use nectar to lure prey insects into the trap organs of the plant.
- Nectar loyalty card — a loyalty card scheme issued by a partnership of UK retailers, including supermarket chain Sainsburys.
- Nectar and ambrosia — the food of the gods in Greek mythology. It is believed that the two terms were not originally distinguished—though in Homer's poems and later works, nectar is the drink and ambrosia the food. On the other hand, in Alcman nectar is the food, and in Sappho and Anaxandrides ambrosia the drink. Each is used in Homer as an unguent (Iliad, xiv. 170; xix. 38). Both are fragrant, and maybe used as perfume. According to W. H. Röscher (Nektar und Ambrosia, 1883; see also his article in Röscher's 'Lexikon der Mythologie) nectar and ambrosia were originally only different forms of the same substance - honey, regarded as a dew, like manna, fallen from heaven, which was used both as food and drink. See also Ichor, mead. Nectar is also mentioned in Hindu mythology, specifically in the Upanishads and the Puranas.

Plant

- Land plants (embryophytes)
- Non-vascular plants (bryophytes)
- Marchantiophyta - liverworts
- Anthocerotophyta - hornworts
- Bryophyta - mosses
- Vascular plants (tracheophytes)
- Lycopodiophyta - clubmosses
- Equisetophyta - horsetails
- Pteridophyta - "true" ferns
- Psilotophyta - whisk ferns
- Ophioglossophyta - adderstongues
- Seed plants (spermatophytes)
- †Pteridospermatophyta - seed ferns
- Pinophyta - conifers
- Cycadophyta - cycads
- Ginkgophyta - ginkgo
- Gnetophyta - gnetae
- Magnoliophyta - flowering plants Magnoliophyta Plants are a major group of living things (about 300,000 species), including familiar organisms such as trees, flowers, herbs, and ferns. Aristotle divided all living things between plants, which generally do not move or have sensory organs, and animals. In Linnaeus' system, these became the Kingdoms Vegetabilia (later Plantae) and Animalia. Since then, it has become clear that the Plantae as originally defined included several unrelated groups, and the fungi and several groups of algae were removed to new kingdoms. However, these are still often considered plants in many contexts. Indeed, any attempt to match "plant" with a single taxon is doomed to fail, because plant is a vaguely defined concept unrelated to the presumed phylogenic concepts on which modern taxonomy is based.

Embryophytes

:See main article at Embryophytes Most familiar are the multicellular land plants, called embryophytes. They include the vascular plants, plants with full systems of leaves, stems, and roots. They also include a few of their close relatives, often called bryophytes, of which mosses and liverworts are the most common. All of these plants have eukaryotic cells with cell walls composed of cellulose, and most obtain their energy through photosynthesis, using light and carbon dioxide to synthesize food. About three hundred plant species do not photosynthesize but are parasites on other species of photosynthetic plants. Plants are distinguished from green algae, from which they evolved, by having specialized reproductive organs protected by non-reproductive tissues. Bryophytes first appeared during the early Palaeozoic. They can only survive where moisture is available for significant periods, although some species are desiccation tolerant. Most species of bryophyte remain small throughout their life-cycle. This involves an alternation between two generations: a haploid stage, called the gametophyte, and a diploid stage, called the sporophyte. The sporophyte is short-lived and remains dependent on its parent gametophyte. Vascular plants first appeared during the Silurian period, and by the Devonian had diversified and spread into many different land environments. They have a number of adaptations that allowed them to overcome the limitations of the bryophytes. These include a cuticle resistant to desiccation, and vascular tissues which transport water throughout the organism. In most the sporophyte acts as a separate individual, while the gametophyte remains small. Devonians (Pteridophyta) more closely allied to seed plants than they are to clubmosses (Lycopodiophyta)]] The first primitive seed plants, Pteridosperms (seed ferns) and Cordaites, both groups now extinct, appeared in the late Devonian and diversified through the Carboniferous, with further evolution through the Permian and Triassic periods. In these the gametophyte stage is completely reduced, and the sporophyte begins life inside an enclosure called a seed, which develops while on the parent plant, and with fertilisation by means of pollen grains. Whereas other vascular plants, such as ferns, reproduce by means of spores and so need moisture to develop, some seed plants can survive and reproduce in extremely arid conditions. Early seed plants are referred to as gymnosperms (naked seeds), as the seed embryo is not enclosed in a protective structure at pollination, with the pollen landing directly on the embryo. Four surviving groups remain widespread now, particularly the conifers, which are dominant trees in several biomes. The angiosperms, comprising the flowering plants, were the last major group of plants to appear, emerging from within the gymnosperms during the Jurassic and diversifying rapidly during the Cretaceous. These differ in that the seed embryo is enclosed, so the pollen has to grow a tube to penetrate the protective seed coat; they are the predominant group of flora in most biomes today.

Algae and Fungi

The algae comprise several different groups of organisms that produce energy through photosynthesis. However, they are not classified within the kingdom plantae but in the kingdom protista instead. The most conspicuous are the seaweeds, multicellular algae that often closely resemble terrestrial plants, but as stated above are not plants, found among the green, red, and brown algae. These and other algal groups also include various single-celled creatures and forms that are simple collections of cells, without differentiated tissues. Many can move about, and some have even lost their ability to photosynthesize; when first discovered, these were considered as both plants and animals. Now they are considered neither, but protists. The embryophytes developed from green algae; the two are collectively referred to as the green plants or Viridiplantae. The kingdom Plantae is now usually taken to mean this monophyletic group, as shown above. With a few exceptions among the green algae, all such forms have cell walls containing cellulose and chloroplasts containing chlorophylls a and b, and store food in the form of starch. They undergo closed mitosis without centrioles, and typically have mitochondria with flat cristae. The chloroplasts of green plants are surrounded by two membranes, suggesting they originated directly from endosymbiotic cyanobacteria. The same is true of the red algae, and the two groups are generally believed to have a common origin. In contrast, most other algae have chloroplasts with three or four membranes. They are not in general close relatives of the green plants, acquiring chloroplasts separately from ingested or symbiotic green and red algae. Unlike embryophytes and algae, fungi are not photosynthetic, but are saprophytes: they obtain their food by breaking down and absorbing surrounding materials. Most fungi are formed by microscopic tubes called hyphae, which may or may not be divided into cells but contain eukaryotic nuclei. Fruiting bodies, of which mushrooms are the most familiar, are actually only the reproductive structures of fungi. They are not related to any of the photosynthetic groups, but are close relatives of animals. Therefore, fungus has a kingdom of its own.

Importance

The photosynthesis and carbon fixation conducted by land plants and algae are the ultimate source of energy and organic material in nearly all habitats. These processes also radically changed the composition of the Earth's atmosphere, which as a result contains a large proportion of oxygen. Animals and most other organisms are aerobic, relying on oxygen; those that do not are confined to relatively few, anaerobic environments. Much of human nutrition depends on cereals. Other plants that are eaten include fruits, vegetables, herbs, and spices. Some vascular plants, referred to as trees and shrubs, produce woody stems and are an important source of building material. A number of plants are used decoratively, including a variety of flowers.

Growth

It is a common misconception that most of the solid material in a plant is taken from the soil, when in fact almost all of it is actually taken from the air. Through a process known as photosynthesis, plants use the energy in sunlight to convert carbon dioxide from the air into simple sugars. These sugars are then used as building blocks and form the main structural component of the plant. Plants rely on soil primarily for water (in quantitative terms), but also obtain nitrogen, phosphorus and other crucial nutrients. phosphorus Simple plants like algae may have short life spans as individuals, but their populations are commonly seasonal. Other plants may be organized according to their seasonal growth pattern:
- Annual: live and reproduce within one growing season.
- Biennial: live for two growing seasons; usually reproduce in second year.
- Perennial: live for many growing seasons; continue to reproduce once mature. Among the vascular plants, perennials include both evergreens that keep their leaves the entire year, and deciduous plants which lose their leaves for some part. In temperate and boreal climates, they generally lose their leaves during the winter; many tropical plants lose their leaves during the dry season. The growth rate of plants is extremely variable. Some mosses grow less than 0.001 mm/h, while most trees grow 0.025-0.250 mm/h. Some climbing species, such as kudzu, which do not need to produce thick supportive tissue, may grow up to 12.5 mm/h.

Fossils

Plant fossils include roots, wood, leaves, seeds, fruit, pollen, spores, phytoliths, and amber (the fossilized resin produced by some plants). Fossil land plants are recorded in terrestrial, lacustrine, fluvial and nearshore marine sediments. Pollen, spores and algae (dinoflagellates and acritarchs) are used for dating sedimentary rock sequences. The remains of fossil plants are not as common as fossil animals, although plant fossils are locally abundant in many regions worldwide. Early fossils of these ancient plants show the individual cells within the plant tissue. The Devonian period also saw the evolution of what many believe to be the first modern tree, Archaeopteris. This fern-like tree combined a woody trunk with the fronds of a fern, but produced no seeds. Archaeopteris The Coal Measures are a major source of Palaeozoic plant fossils, with many groups of plants in existence at this time. The spoil heaps of coal mines are the best places to collect; coal itself is the remains of fossilised plants, though structural detail of the plant fossils is rarely visible in coal. In the Fossil Forest at Victoria Park in Glasgow, Scotland, the stumps of Lepidodendron trees are found in their original growth positions. The fossilized remains of conifer and angiosperm roots, stems and branches may be locally abundant in lake and inshore sedimentary rocks from the Mesozoic and Caenozoic eras. Sequoia and its allies, magnolia, oak, and palms are often found. Petrified wood is common in some parts of the world, and is most frequently found in arid or desert areas were it is more readily exposed by erosion. Petrified wood is often heavily silicified (the organic material replaced by