Monkey

Monkey (animal), any of about 160 species of primates that have grasping hands, forward-facing eyes, and highly developed brains. Most monkeys also have tails, a characteristic that distinguishes them from their larger primate cousins, the apes. Monkeys are highly skilled climbers, and most spend much of their lives in trees. Some have prehensile tails—that is, tails capable of grasping—that they can use as a fifth limb while foraging for food or climbing.

Zoologists classify monkeys into three distinct families: marmosets, Capuchin-like monkeys, and Old World monkeys. Marmosets and Capuchin-like monkeys are found only in Central and South America and are known collectively as New World monkeys. Marmosets are dainty animals with luxurious fur, which is sometimes strikingly colored. One species, the pygmy marmoset, is the world's smallest monkey, measuring just 30 cm (12 in) long, at least half of which is tail, and weighing as little as 113 g (4 oz) when fully grown. The average life span of a pygmy marmoset in the wild is 10 to 12 years. By comparison, the Capuchin-like monkeys, which include capuchin monkeys, douroucoulis, spider monkeys, woolly monkeys, and howler monkeys, are more robust, although they are still lightly built. Howler monkeys, for example, are among the largest species and measure up to 1.8 m (6 ft) from the top of the head to the tip of the tail. Even so, their maximum weight is only about 10 kg (22 lb). Howler monkeys living in the wild have an average life span of around 16 to 20 years. Many New World monkeys have prehensile tails, and all have broad noses with sideways-opening nostrils.

Old World monkeys include guenons, mangabeys, colobus monkeys, macaques, langurs, and baboons. Compared to New World monkeys, their noses are narrower and have downward-opening nostrils. Old World monkeys do not have prehensile tails; instead, most use their tails simply for balance. As a result, these monkeys are less acrobatic than their New World cousins. Most Old World monkeys spend at least part of their time on the ground. While many are careful not to stray too far from the protective cover of trees, baboons are strong and aggressive enough to defend themselves in the open. Armed with fearsome canine teeth and weighing up to 41 kg (90 lb), male baboons are more than a match for many predators. A baboon in the wild can live as long as 30 years.

PREDATORS

The predators of Capuchin-like monkeys are humans and birds of prey. The predators of marmosets include small cats, birds of prey, and snakes. The predators of macaques include large cats, such as leopards, tigers, and panthers, and large snakes, such as pythons. The predators of langurs and colobus monkeys include large cats, humans, and some birds of prey. The biggest threat to all monkeys, however, is the loss of habitat

RANGE AND HABITAT

Monkeys are restricted to South and Central America, Africa, and the southern parts of Asia. Most monkeys live in the forests of the tropics and subtropics, where warm temperatures ensure a year-round supply of food. In rain forests, where food is abundant, monkeys often stay in the same area all year, but in drier habitats, they have to range further afield, possibly traveling more than 18 km (10 mi) a day.

Although most monkeys live in warm climates, some do survive in extreme environments. The Japanese macaque manages to survive the winter cold on the Japanese island of Honshū—the only nonhuman primate to survive that far north. A few tropical monkeys survive on high mountains well above the snow line, some at elevations as high as 4,000 m (13,000 ft). These high-altitude species include the Asian snub-nosed langurs, the African vervet, and several species of macaques. Monkeys can also survive in extreme deserts. In southwest Africa, for example, a troop of yellow baboons lives in the Namib Desert, where rainfall averages just a few inches a year.

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Dog

Dogs

Dog, mammal generally considered to be the first domesticated animal. This trusted work partner and beloved pet learned to live with humans more than 14,000 years ago. A direct descendant of the wolves that once roamed Europe, Asia, and North America, the domestic dog belongs to the dog family, which includes wolves, coyotes, foxes, and jackals. Dog ancestry has been traced to small, civet-like mammals, called miacis, which had short legs and a long body and lived approximately 40 million years ago.The evolving relationship between the domestic dog and humans has been documented in fossil evidence, artifacts, and records left by earlier civilizations. Prehistoric dog skeletal remains, excavated from sites in Denmark, England, Germany, Japan, and China, indicate the early coexistence of dogs with people. An ancient Persian cemetery, dating to the 5th century bc, contained thousands of dog skeletons. Their formal burial and the positioning of the dog remains reveal the esteem in which the ancient Persians held their dogs. The relationship shared by dogs and humans also is evident in cave drawings, early pottery, and Asian ivory carvings that depict dogs. A statue of Anubis, the half dog, half jackal Egyptian god, was discovered inside King Tutankhamen’s tomb, constructed in about 1330 bc.

Literary references to the dog include those found in the Bible and in the Greek classic the Odyssey by Homer. In 1576 an English physician and dog fancier, John Caius, wrote a detailed text on dog breeds, Of English Dogges. Dogs are featured in tapestries that were created in the Middle Ages (5th century to 15th century), and in the work of many artists, including 17th- and 18th-century European painters Peter Paul Rubens and Thomas Gainsborough.

Although it is not known how humans and dogs first learned to coexist, people soon discovered the many ways dogs could enrich their lives. Dogs have been used to hunt for food, herd animals, guard livestock and property, destroy rats and other vermin, pull carts and sleds, perform rescues, and apprehend lawbreakers. They have been used during wartime as sentinels and message carriers. Today trained dogs are used to alert deaf people to common household sounds, such as the ringing telephone or doorbell; guide the blind; or retrieve objects for quadriplegics. Perhaps the most common of the many roles served by the domestic dog, however, is that of companion. As animals with strong social tendencies, dogs typically crave close contact with their owners. And people tend to form loving bonds with dogs. This companionship often helps to ease the pain and isolation of the elderly or people whose physical or mental health requires long-term convalescence or institutionalization.

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Snake

Snake (reptile), legless animal with a long, flexible body covered with overlapping scales. Snakes are reptiles, a diverse group of animals that also includes lizards, turtles, and crocodiles. Snakes are thought to have evolved from lizards and share many characteristics with this group—particularly the so-called legless lizards, which have tiny, almost imperceptible legs. But unlike most lizards, snakes have thin, forked tongues, and they lack external ears. And while most lizards have movable eyelids that periodically close to protect and lubricate the eyes, a snake’s eyes are always open, protected by immobile, transparent scales.
Like all reptiles, snakes are cold-blooded, or more correctly, ectothermic—that is, they cannot produce their own body heat. Instead, they rely on the sun to heat their bodies and then regulate their temperature with behavior. Because they do not rely on energy from food to generate body heat, snakes can survive on an extremely meager diet. Some wait for months between successive meals, and a few survive by eating a single, large meal just once or twice a year. When they do eat, snakes swallow their prey whole rather than biting off small pieces. Many snakes have specialized jaws that enable them to swallow animals that are far larger than their own heads. Although uncommon, some snakes, such as the African rock python, have been observed eating animals as large as an antelope or a small cow.
With over 2,500 species belonging to more than 10 families, snakes are a large and successful group. They owe much of this success to their versatility—snakes occupy habitats ranging from underground burrows to the tops of trees to ocean depths as great as 150 m (490 ft). They are found on every continent except Antarctica, and although they are most abundant in tropical areas, many survive in regions marked by extreme cold. The range of the European adder, for instance, extends north of the Arctic Circle. The only places without snakes are parts of the polar regions and isolated islands, such as Ireland and New Zealand.
PHYSICAL CHARACTERISTICS

  Although all snakes have a long, cylindrical body, many species boast unique modifications suited to particular habitats and lifestyles. Burrowing snakes, for example, have muscular, stout bodies and solidly built heads that they use to push through soil. Sea snakes have flattened, paddlelike tails for swimming, and the long, thin shape of many arboreal, or tree-dwelling, snakes provides agility when navigating between branches. Some snakes, including pythons, retain characteristics that reflect their evolution from lizards or from lizardlike ancestors. These snakes have traces of hind limbs called spurs, which are usually more prominent in males than in females.The smallest snakes are the blind snakes. One member of this group, the Texas slender blind snake, reaches just 13 cm (slightly more than 5 in) in length when full grown and weighs less than 2 g (less than 0.1 oz). The largest snakes are the anaconda and the reticulated python, both of which grow as long as 10 m (about 33 ft) and can weigh up to 250 kg (about 550 lb). Among most species of snakes, females are larger than males.

Skin

Snake bodies are covered in overlapping scales composed of a horny material called keratin. These transparent scales make up the dry, smooth, outer layer of skin, whose primary function is to prevent water loss. Snakes owe their coloration to pigment cells located in the skin layer below the scales. Most snakes display drab earth tone colors to blend with their natural surroundings. Arboreal species, such as the emerald tree boa, are often vibrant shades of green, a coloration that helps them hide among leafy foliage. Some snakes, such as coral snakes, have brilliant yellow and orange stripes that warn predators of their venomous bite.

Snakes regularly shed the outer layer of their skin as they grow. Even in snakes that are not growing, the scales become drab and worn over time, and must be periodically replaced by a new, healthy layer. Some species of snakes shed their skin about every 20 days, but other species shed it only once a year. In the shedding process, a new layer develops below the surface of the old one, which gradually separates in preparation for being shed, or sloughed. The snake begins the shedding process by rubbing its nose against rocks or other hard objects to separate the old layer from its lips. After the old layer is loosened, the snake crawls out of its old skin, typically shedding it in a single piece.

Internal Organs


Snakes share an internal anatomy similar to that of other reptiles, but modified to fit within an extremely narrow space. The snake’s three-chambered heart can move sideways to accommodate large prey animals traveling from the mouth to the stomach. The snake’s respiratory system is also compact: Most snakes rely exclusively on the right lung for respiration. In these animals, the left lung is either very small or nonexistent. Snakes have two kidneys, which are positioned so that the left one lies behind the right one rather than beside it. Similarly, the reproductive organs—a pair of testes for males and a pair of ovaries for females—are situated end-to-end. The snake has an extremely muscular and flexible stomach, a narrow liver, and both large and small intestines. Unlike the small intestines of many other vertebrates, those of snakes are stretched out instead of coiled. Like other reptiles, snakes have a cloaca, an internal chamber that receives wastes from the digestive system and eggs or sperm from the reproductive system before they leave the body. Snakes do not have a urinary bladder; instead, they excrete all their wastes through the rectum.
Senses


A snake obtains information about its environment primarily through the Jacobson’s organ located in the roof of its mouth. The snake continuously flicks out its forked tongue to collect scent particles from the air and the ground. When the tongue draws back into the mouth, the forked tips fit into cell-lined pockets in the Jacobson’s organ, which detects the odors of the particles it receives. This system is keenly sensitive, and snakes rely on it to locate both mates and prey.

Vision and the ability to detect vibrations are also important to the survival of most snakes. Snakes lack eardrums and external ear openings, but they have small bones in their heads that conduct sound. They are able to hear low-frequency sounds and to sense vibrations that travel through the ground or water. The majority of snakes have good eyesight, especially for detecting moving objects, although most burrowing snakes can only distinguish between light and dark.

Pit vipers, boas, and pythons have an unusual adaptation for detecting warm-blooded prey and predators. On the heads of these snakes are small pits lined with cells that are extremely sensitive to heat. These pits enable the snakes to sense the presence of a warm-blooded animal and strike accurately, even in total darkness.

Feeding

Snakes have a wide range of food preferences. Many snakes eat worms, insects, lizards, small mammals, birds, and frogs. Some snakes, such as the Australian bandy-bandy, feed only on other snakes. Several groups of snakes, including the egg-eating snakes of Asia, prefer the eggs of other animals; these snakes have modified teeth and vertebrae in the throat for breaking eggshells. These teeth snag the shell as the egg, swallowed whole, starts down the digestive tract; the broken shell is regurgitated. Among some species, males and females eat different types of food. For example, male Arafura filesnakes eat small fish that inhabit shallow water, while females of the same species eat larger fish that live in deeper water. Many snakes change their diet as they grow larger, as in the reticulated pythons. When young, these snakes feed mostly on rats. When they reach about 4 m (13 ft) in length, they switch to larger prey, such as wild pigs, monkeys, and small deer.
Snakes use diverse strategies for capturing their prey. Slender and agile snakes actively pursue their prey, but snakes with thicker bodies, such as pythons, are more likely to wait in a coiled position and ambush their prey as it passes by. Many snakes begin to swallow their prey while it is still alive. The teeth of snakes point backward and are not designed for chewing—instead, snakes use their teeth to pin down their prey to prevent its escape. Others kill prey animals before eating them.

Snakes that kill their prey use one of two methods: constriction or envenomation—the injection of venom. Constrictors, such as pythons and kingsnakes, wrap their coils around a prey animal, tightening their grip each time the prey exhales. In this way, constrictors gradually suffocate their victims. Several groups of snakes kill their prey with venom. Copperheads, bushmasters, and other vipers inject their venom and then release the prey immediately, later following the scent trail to find the dead animal. Others, such as cobras, simply hang onto the prey they have poisoned and swallow it when its struggles have ceased.

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Dinosaur

Dinosaur

Dinosaur, one of a group of extinct reptiles that lived from about 230 million to about 65 million years ago. The word dinosaur was coined in 1842 by British anatomist Sir Richard Owen, derived from the Greek words deinos, meaning “marvelous” or “terrible,” and sauros, meaning “lizard.” For more than 140 million years, dinosaurs reigned as the dominant animals on land.

Owen distinguished dinosaurs from other prehistoric reptiles by their upright rather than sprawling legs and by the presence of three or more vertebrae supporting the pelvis, or hipbone. Dinosaurs are classified into two orders according to differences in pelvic structure: Saurischia, or lizard-hipped dinosaurs, and Ornithischia, or bird-hipped dinosaurs. Dinosaur bones occur in sediments that were deposited during the Mesozoic Era, the so-called era of middle animals, also known as the age of reptiles. This era is divided into three periods: the Triassic (251 million to 200 million years ago), the Jurassic (200 million to 145 million years ago), and the Cretaceous (145 million to 65 million years ago).

Historical references to dinosaur bones may extend as far back as the 5th century bc. Some scholars think that Greek historian Herodotus was referring to fossilized dinosaur skeletons and eggs when he described griffins—legendary beasts that were part eagle and part lion—guarding nests in central Asia. “Dragon bones” mentioned in a 3rd century ad text from China are thought to refer to bones of dinosaurs.

The first dinosaurs studied by paleontologists (scientists who study prehistoric life) were Megalosaurus and Iguanodon, whose partial bones were discovered early in the 19th century in England. The shape of their bones indicates that these animals resembled large, land-dwelling reptiles. The teeth of Megalosaurus, which are pointed and have serrated edges, indicate that this animal was a flesh eater, while the flattened, grinding surfaces of Iguanodon teeth indicate that it was a plant eater. Megalosaurus lived during the Jurassic Period, and Iguanodon lived during the early part of the Cretaceous Period. Later in the 19th century, paleontologists collected and studied more complete skeletons of related dinosaurs found in New Jersey. From these finds they learned that Megalosaurus and Iguanodon walked on two legs, not four, as had been thought.

In the late 19th and early 20th centuries, as the science of paleontology grew and the search for dinosaur remains was extended around the world, new kinds of dinosaurs were discovered. Hundreds of different varieties of dinosaur have been identified from bones found on all of the continents as well as on the islands of Greenland, Madagascar, and New Zealand.

ANCESTRY

Dinosaurs belong to a group of advanced reptiles called archosaurs, which appeared late in the Permian Period. Archosaurs survive today in the form of crocodiles and birds. In addition to dinosaurs, extinct archosaurs included pterosaurs (flying reptiles) and a number of other types of reptiles formerly grouped together under the name thecodonts. During the Triassic, two distinct groups of archosaurs evolved, one related to crocodiles and the other related to dinosaurs, birds, and pterosaurs.

Scientists were once confused about the early ancestors of dinosaurs because some of the archosaurs related to crocodiles developed a number of dinosaur-like features, including walking upright on two hind legs. This phenomenon is known as parallel evolution, in which animals that are not directly related come to resemble each other because they have similar life styles or diets. New fossils have allowed paleontologists to better recognize the true ancestors of dinosaurs. The ancestors of dinosaurs also walked on two hind legs, but had S-shaped necks; simple, hingelike ankle bones; and other distinctive features.

Fossil evidence of the earliest dinosaurs dates from about 230 million years ago. This evidence, found in Madagascar in 1999, consists of bones of an animal about the size of a kangaroo. This dinosaur was a type of saurischian and was a member of the plant-eating prosauropods, which were related to ancestors of the giant, long-necked sauropods that included the Apatosaurus. Prior to this discovery, the earliest known dinosaur on record was the Eoraptor, which lived 227 million years ago. Discovered in Argentina in 1992, the Eoraptor was an early saurischian, 1 m (3 ft) long, with a primitive skull.

Scientists have identified remains of a few small dinosaurs representing ornithischians dating from the end of the Triassic Period before about 200 million years ago. By the middle of the Jurassic Period, around 180 million years ago, most of the basic varieties of saurischian and ornithischian dinosaurs had appeared, including some that far surpassed modern elephants in size. Dinosaurs had evolved into the most abundant large animals on land, and the dinosaurian age had begun.

HABITAT

Earth’s environment during the dinosaurian era was far different than it is today. The days were several minutes shorter than they are today because the gravitational pull of the sun and the moon have over time had a braking influence on Earth’s rotation. Radiation from the Sun was not as strong as it is today because the Sun has been slowly brightening over time.

Other changes in the environment may be linked to the atmosphere. Carbon dioxide, a gas that traps heat from the Sun in Earth’s atmosphere—the so-called greenhouse effect—was several times more abundant in the air during the dinosaurian age. As a result, surface temperatures were warmer and no polar ice caps could form.

The pattern of continents and oceans was also very different during the age of dinosaurs. At the beginning of the dinosaurian era, the continents were united into a gigantic supercontinent called Pangaea (all lands), and the oceans formed a vast world ocean called Panthalassa (all seas). About 200 million years ago, movements of Earth’s crust caused the supercontinent to begin slowly separating into northern and southern continental blocks, which broke apart further into the modern continents by the end of the dinosaurian era.

give the egg

As a result of these movements of Earth’s crust (see Plate Tectonics), there was less land in equatorial regions than there is at present. Deserts, possibly produced by the warm, greenhouse atmosphere, were widespread across equatorial land, and the tropics were not as rich an environment for life forms as they are today. Plants and animals may have flourished instead in the temperate zones north and south of the equator.

The most obvious differences between dinosaurian and modern environments are the types of life forms present. There were fewer than half as many species of plants and animals on land during the Mesozoic Era than there are today. Bushes and trees appear to have provided the most abundant sources of food for dinosaurs, rather than the rich grasslands that feed most animals today. Although flowering plants appeared during the dinosaurian era, few of them bore nuts or fruit.

The animals of the period had slower metabolisms and smaller brains, suggesting that the pace of life was relatively languid and the behavior patterns were simple. The more active animals—such as ants, wasps, birds, and mammals—first made their appearance during the dinosaurian era but were not as abundant as they are now.

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Honey Bee

Honey bee in the field

Honey Bee From Egg to Adult

Honey Bee, common name for any of several species of highly social bees known for their honey-hoarding behavior and their use as a domesticated species (see Beekeeping). The European honey bee is important in modern agriculture and in nature, providing pollination for many valuable crops and wild plants. It is native to Asia and the Middle East and was introduced to North America by early European colonists. By the mid-1800s honey bees had become widespread. Today, they are naturalized on every continent except Antarctica. Honey bees can be easily reared, are adaptable to many climates and to laboratory conditions, and have a complex social life. They are among the most studied and best known insects.]DIVERSITY

In addition to the familiar European honey bee, there are six other recognized species of honey bees, including the Indian honey bee, Koschevnikov’s honey bee, the dwarf honey bee, the andreniform dwarf honey bee, the giant honey bee, and the mountain giant honey bee. The European, the Indian, and to some extent the dwarf honey bees are the species that have been domesticated, although the European honey bee is by far the most widespread domesticated bee and the only species kept in North America. There are many races of the European honey bee. The ones most popular in modern beekeeping are the Italian, Carniolan, and Caucasian. Most honey bees used in hives today are mixtures of these and sometimes other races. Africanized honey bees, also known as killer bees, are a hybrid of African and European races naturalized in the western hemisphere.
  III. SOCIAL ORGANIZATION

The honey bee is a social insect that can survive only as a member of a community, or colony. The colony inhabits an enclosed cavity, its nest. Domesticated colonies are kept in artificial containers, usually wooden boxes, known as hives.  
Castes
The honey bee community consists of three structurally different forms—the queen (reproductive female), the drone (male), and the worker (nonreproductive female). These castes are associated with different functions in the colony; each caste possesses its own special instincts geared to the needs of the colony.

1.

The Queen

The queen is the only sexually productive female in the colony and thus is the mother of all drones, workers, and future queens. Her capacity for laying eggs is outstanding; her daily output often exceeds 1500 eggs, the weight of which is equivalent to that of her own body.

Anatomically, the queen is strikingly different from the drones and workers. Her body is long, with a much larger abdomen than a worker bee. Her mandibles, or jaws, contain sharp cutting teeth, whereas her offspring have toothless jaws. The queen has a curved, smooth stinger that she can use repeatedly without endangering her own life. In contrast, the worker honey bees are armed with straight, barbed stingers, so that when a worker stings, the barbed, needlesharp organ remains firmly anchored in the flesh of its victim. In trying to withdraw the stinger, the bee tears its internal organs and dies shortly thereafter. The queen bee lacks the working tools possessed by worker bees, such as pollen baskets, beeswax-secreting glands, and a well-developed honey sac. Her larval food consists almost entirely of a secretion called royal jelly that is produced by worker bees. The average lifespan of the queen is one to three years.

Workers bee 

Worker bees are the most numerous members of the colony. A healthy colony may contain 80,000 worker bees or more at its peak growth in early summer. Workers build and maintain the nest and care for the brood. They build the nest from wax secreted from glands in their abdomen. The hexagonal cells, or compartments, constructed by the workers are arranged in a latticework known as the comb. The cells of the comb provide the internal structure of the nest and are used for storage of the developing young bees and all the provisions used by the colony. Comb used for storage of honey is called honeycomb. Workers leave the hive to gather nectar, pollen, water, and propolis, a gummy substance used to seal and caulk the exterior of the nest. They convert the nectar to honey, clean the comb, and feed the larvae, drones, and the queen. They also ventilate the nest and when necessary, defend the colony with their stings. Workers do not mate and therefore can not produce fertile eggs. They occasionally lay infertile eggs, which give rise to drones.

As with all bees, pollen is the principal source of protein, fat, minerals, and vitamins, the food elements essential for the growth and development of larvae of all three castes. Adult bees can subsist on honey or sugar, a pure carbohydrate diet. Besides gathering and storing food for all the members of the colony, the workers are responsible for maintaining the brood at 33.9°C (93°F), the optimum temperature required for hatching the eggs and rearing the young. When the nest or hive becomes too hot the workers collectively ventilate it by fanning their wings. During cool weather, they cluster tightly about the nursery and generate heat. The eggs, which are laid one per cell, hatch in three days. The larvae are fed royal jelly for at least two days and then pollen and nectar or honey. Each of the hundreds of larvae in a nest or hive must be fed many times a day.

For the first three weeks of their adult lives, the workers confine their labors to building the honeycomb, cleaning and polishing the cells, feeding the young and the queen, controlling the temperature, evaporating the water from the nectar until it thickens as honey, and many other miscellaneous tasks. At the end of this period, they function as field bees and defenders of the colony. The workers that develop early in the season live extremely busy lives, which, from egg to death, last about six weeks. Worker bees reared late in the fall usually live until spring, since they have little to do in the winter except eat and keep warm. Unlike other species of bees, honey bees do not hibernate; the colony survives the winter as a group of active adult bees.

3.	The Drone Bee

Drones are male honey bees. They are stingless, defenseless, and unable to feed themselves—they are fed by worker bees. Drones have no pollen baskets or wax glands and cannot secrete royal jelly. Their one function is to mate with new queens. After mating, which always takes place on the wing in the open air, a drone dies immediately. Early investigators of the mating habits of the honey bee concluded that a queen mates only once in her life. Recent scientific studies, however, have established that she usually mates with six or more drones in the course of a few days. The motile sperm of the drones find their way into a small, saclike organ, called the spermatheca, in the queen’s abdomen. The sperm remain viable in this sac throughout the life of the queen.

Drones are prevalent in colonies of bees in the spring and summer months. As fall approaches, they are driven out of the nests or hives by the workers and left to perish.

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Human Nutrition

Human Nutrition, study of how food affects the health and survival of the human body. Human beings require food to grow, reproduce, and maintain good health. Without food, our bodies could not stay warm, build or repair tissue, or maintain a heartbeat. Eating the right foods can help us avoid certain diseases or recover faster when illness occurs. These and other important functions are fueled by chemical substances in our food called nutrients. Nutrients are classified as carbohydrates, proteins, fats, vitamins, minerals, and water.When we eat a meal, nutrients are released from food through digestion. Digestion begins in the mouth by the action of chewing and the chemical activity of saliva, a watery fluid that contains enzymes, certain proteins that help break down food. Further digestion occurs as food travels through the stomach and the small intestine, where digestive enzymes and acids liquefy food and muscle contractions push it along the digestive tract. Nutrients are absorbed from the inside of the small intestine into the bloodstream and carried to the sites in the body where they are needed. At these sites, several chemical reactions occur that ensure the growth and function of body tissues. The parts of foods that are not absorbed continue to move down the intestinal tract and are eliminated from the body as feces.Once digested, carbohydrates, proteins, and fats provide the body with the energy it needs to maintain its many functions. Scientists measure this energy in kilocalories, the amount of energy needed to raise 1 kilogram of water 1 degree Celsius. In nutrition discussions, scientists use the term calorie instead of kilocalorie as the standard unit of measure in nutrition.
ESSENTIAL NUTRIENTS

Nutrients are classified as essential or nonessential. Nonessential nutrients are manufactured in the body and do not need to be obtained from food. Examples include cholesterol, a fatlike substance present in all animal cells. Essential nutrients must be obtained from food sources, because the body either does not produce them or produces them in amounts too small to maintain growth and health. Essential nutrients include water, carbohydrates, proteins, fats, vitamins, and minerals.

An individual needs varying amounts of each essential nutrient, depending upon such factors as gender and age. Specific health conditions, such as pregnancy, breast-feeding, illness, or drug use, make unusual demands on the body and increase its need for nutrients. Dietary guidelines, which take many of these factors into account, provide general guidance in meeting daily nutritional needs.

WATER

If the importance of a nutrient is judged by how long we can do without it, water ranks as the most important. A person can survive only eight to ten days without water, whereas it takes weeks or even months to die from a lack of food. Water circulates through our blood and lymphatic system, transporting oxygen and nutrients to cells and removing wastes through urine and sweat. Water also maintains the natural balance between dissolved salts and water inside and outside of cells. Our joints and soft tissues depend on the cushioning that water provides for them. While water has no caloric value and therefore is not an energy source, without it in our diets we could not digest or absorb the foods we eat or eliminate the body’s digestive waste.

The human body is 65 percent water, and it takes an average of eight to ten cups to replenish the water our bodies lose each day. How much water a person needs depends largely on the volume of urine and sweat lost daily, and water needs are increased if a person suffers from diarrhea or vomiting or undergoes heavy physical exercise. Water is replenished by drinking liquids, preferably those without caffeine or alcohol, both of which increase the output of urine and thus dehydrate the body. Many foods are also a good source of water—fruits and vegetables, for instance, are 80 to 95 percent water; meats are made up of 50 percent water; and grains, such as oats and rice, can have as much as 35 percent water.

Carbohydrates

Carbohydrates are the human body’s key source of energy, providing 4 calories of energy per gram. When carbohydrates are broken down by the body, the sugar glucose is produced; glucose is critical to help maintain tissue protein, metabolize fat, and fuel the central nervous system.

Glucose is absorbed into the bloodstream through the intestinal wall. Some of this glucose goes straight to work in our brain cells and red blood cells, while the rest makes its way to the liver and muscles, where it is stored as glycogen (animal starch), and to fat cells, where it is stored as fat. Glycogen is the body’s auxiliary energy source, tapped and converted back into glucose when we need more energy. Although stored fat can also serve as a backup source of energy, it is never converted into glucose. Fructose and galactose, other sugar products resulting from the breakdown of carbohydrates, go straight to the liver, where they are converted into glucose.

Starches and sugars are the major carbohydrates. Common starch foods include whole-grain breads and cereals, pasta, corn, beans, peas, and potatoes. Naturally occurring sugars are found in fruits and many vegetables; milk products; and honey, maple sugar, and sugar cane. Foods that contain starches and naturally occurring sugars are referred to as complex carbohydrates, because their molecular complexity requires our bodies to break them down into a simpler form to obtain the much-needed fuel, glucose. Our bodies digest and absorb complex carbohydrates at a rate that helps maintain the healthful levels of glucose already in the blood.

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Common Chemistry Equations

Density:

where m is the mass of a substance and V is its volume

Charles’s Law:

where V is volume, k is Boltzmann’s constant, and T is the temperature in Kelvin

Ideal Gas Equation:

where P is pressure, V is volume, n is the number of moles of gas, R is the gas constant, and T is the temperature in Kelvin

Molarity:

where n is the number of moles of solute and V is the volume of solution in liters

Molarity equation:

where M₁ is the initial molarity of a solution, V₁ is its initial volume, M₂ is its diluted molarity, and V₂ is its diluted volume

Molality:

where n is the number of moles of solute and m_s is the mass of solvent in kilograms

pH:

where H⁺ is the concentration of hydronium ions (H₃O⁺) in the solution

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CAT

Cat, small, mainly carnivorous animal, Felis silvestris catus, member of the family Felidae, popular as a household pet, and valuable for killing mice and rats. Like other members of the cat family, the domestic cat has retractile claws; keen hearing and smell; remarkable night vision; and a compact, muscular, and highly supple body. Cats possess excellent memory and exhibit considerable aptitude for learning by observation and experience. The natural life span of a domestic cat is about 15 years. There are an estimated 600 million house cats in the world.
ORIGIN OF SPECIES
Debate has surrounded the origin of the domestic cat. A common theory held that cats were first domesticated by ancient Egyptians perhaps as early as 2500 bc from the African or Near Eastern wildcat Felis silvestris libyca, also called the Caffre cat. Crusaders then transported the cat to Europe, where it interbred with the indigenous smaller wildcats Felis silvestris silvestris. The idea that domestic cats in different parts of the world had originated from, or interbred with, populations of local wildcats and other small cat species was proposed by a number of experts. For example, the longhaired breeds of domestic cats were said to come from the Asian Pallas’s cat, Felis manul.

However, a study published in 2007 compared the mitochondrial DNA of domestic cats and wildcats and concluded that the domestic cat derives only from Felis silvestris libyca. Members of this particular subspecies of wildcat were domesticated in the Middle East, likely around the time that farming villages first developed in the Fertile Crescent region between 10,000 and 12,000 years ago. Wildcats probably began associating with human settlements to prey on the rodents and other pests attracted by stored grains and cereals. Some of the wildcats then gave up their more aggressive wild behaviors to adapt to life with people.

The DNA study indicates that at least five individual female cats from the Middle East served as founders for all the domestic cats that were later carried around the world by humans. This new DNA evidence appears to contradict theories that domestic cats carry genes that come from other types of small cats and from wildcats found in different parts of the world. Some interbreeding between domestic cats and local wildcats probably took place, however. Over the centuries, cats have remained virtually the same in size, weighing about 3.6 kg (about 8 lb) when full-grown, and have preserved their instinct for solitary hunting.

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Heliophysics

       We live in the extended atmosphere of an active star. While sunlight enables and sustains life, the Sun's variability produces streams of high energy particles and radiation that can harm life or alter its evolution.
Under the protective shield of a magnetic field and atmosphere, the Earth is an island in the Universe where life has developed and flourished. The origins and fate of life on Earth are intimately connected to the way the Earth responds to the Sun's variations.
Understanding the Sun, Heliosphere, and Planetary Environments as a single connected system is the goal of the Science Mission Directorate's Heliophysics Research Program. In addition to solar processes, our domain of study includes the interaction of solar plasma and radiation with Earth, the other planets, and the Galaxy. By analyzing the connections between the Sun, solar wind, planetary space environments, and our place in the Galaxy, we are uncovering the fundamental physical processes that occur throughout the Universe. Understanding the connections between the Sun and its planets will allow us to predict the impacts of solar variability on humans, technological systems, and even the presence of life itself.
We have already discovered ways to peer into the internal workings of the Sun and understand how the Earth's magnetosphere responds to solar activity. Our challenge now is to explore the full system of complex interactions that characterize the relationship of the Sun with the solar system. Understanding these connections is especially critical as we contemplate our destiny in the third millennium. Heliophysics is needed to facilitate the accelerated expansion of human experience beyond the confines of our Earthly home. Recent advances in technology allow us, for the first time, to realistically contemplate voyages beyond the solar system.

There are three primary objectives that define the multi-decadal studies needed:

• To understand the changing flow of energy and matter throughout the Sun, Heliosphere, and Planetary Environments.
• To explore the fundamental physical processes of space plasma systems.
• To define the origins and societal impacts of variability in the Earth-Sun System.

A combination of interrelated elements is used to achieve these objectives. They include complementary missions of various sizes; timely development of enabling and enhancing technologies; and acquisition of knowledge through research, analysis, theory, and modeling.
sorces    

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