Big Book of Knowledge

Holding hands You can pick up things Not a word because you are able The chimp is one to fold your thumb of the few mammals across your hand. Frightened Angry that can make faces to Like you, Apes and monkeys show its feelings. apes have sensitive have these useful, hands. “opposable” thumbs, too. Male gorillas stand up to 6.5 feet (two meters) tall. They live in Africa. Is it a bird? Gorillas have about the An orangutan’s big Every night, orangs build a cozy same number of hairs as toes can grip things, too! nest to sleep in. It takes just five you.They look hairier minutes to build a mattress of because their hair is long Big branches and a blanket of leaves. and thick. brain Baby gorillas learn Apes see things Gorillas can climb trees, to crawl at nine weeks, in color—just but they spend most of the climb at six or seven like you. day relaxing on the ground. months, and walk at eight months. All apes They may live can sit to be forty. and stand up straight.

MONKEYS Monkeys are primates. It is easy to tell them apart from the smarter primates, people, and apes, because they have tails. Some, such as mandrills, live on the ground, but most monkeys are light enough to jump or swing through the trees. They always look before they leap, though, Squirrel because there is danger all around. Large monkey eagles may swoop down from above and leopards lurk Built to balance below. If they miss their footing, monkeys may plunge If you start to lose up to 200 feet (60 meters) to the ground! your balance, you can use your arms to steady yourself. Monkeys use their tails instead—leaving their Keep it clean! arms free for climbing. These rhesus monkeys are lining up to have insects and dirt picked out of their fur. They Groups of monkeys are even pick one another’s called troops. teeth clean! This grooming helps to keep them tidy and also good friends. Face to face Telltale tail Mandrill (male) Proboscis monkey (male) Ring-tailed lemurs are primitive primates and live in troops like monkeys. They keep together in tall grass by pointing their tails upward. This lemur is looking for a tail to follow! Bald uakari Cotton-top tamarin 200

A gripping tail Both eyes face Many South American forward to spot safe monkeys have three “arms”— landing places! their tails are prehensile, so they can hold on to things. A Mane spider monkey can hang by its of soft, strong tail, leaving both hands silky hair. free for feeding. All primates, including you, see in color. Narrow chest Monkeys’ legs Monkeys are are shorter than not fussy eaters. their arms. They eat fruit, flowers, lizards, This tamarin weighs only butterflies, and 21 ounces (600 grams), even frogs’ legs! so it is light enough to Bath time scamper across small These Japanese snow monkeys branches without relax and warm up in winter breaking them. by sitting in pools of hot water that bubble up from People have chopped beneath the icy ground. down so many of the trees that golden lion tamarins live in that there are only about 1,000 of these monkeys left in the wild. Golden lion tamarins Hairy are 13–15 inches tail (32–37 centimeters) tall. They live in Brazil.

BATS Bats are furry, flying mammals. Their wings are made of thin, leathery skin, which is The ears of this long-eared stretched across their fingers like material bat are almost as big as its over the spokes of an umbrella. Bats live body. It tucks them under its wings when it sleeps. all over the world, but you will not often see them flying. Most bats hang upside down and sleep during the day. They Bats hear hunt at night. Most small bats eat better than moths and flies. Larger, vegetarian all other mammals. bats, often called flying foxes because they have foxlike faces, feed on bananas and nectar. Acrobatic bats swoop through Mouselike, furry body the sky at up to 40 miles (64 Wrist kilometers) per hour—fast enough to escape from owls. Moth This bat has caught a night-flying moth, which it found by listening for it in the dark. Fruity bat The bat cave Jungles might not Nearly all bats are awake exist without bats! at night—they are nocturnal. Sleepy Fruit-eating bats days are spent inside caves or holes in pollinate plants, and trees. As the sun sets, millions of bats stream out of their caves to go hunting. the seeds they spit out or leave in their droppings can grow into trees. 202

Camping bats Imagine having to build a new house every night— tent bats do! These small, white bats nibble through the middle rib of a palm leaf until it droops down to form a tiny tent. The bats hang underneath, out of the wind and rain. This is a thumb. Bats use their The wing can be The smallest mammal thumbs as combs to groom their fur used as a scoop to The bumblebee bat can fit and as hooks to hold onto things. catch flying insects. in the palm of your hand. Its body is one inch (three cm) long and its wingspan is just 5 inches (13 cm). It weighs less than a grape. Long finger Long-eared bats Fangs for dinner! have a wingspan of Vampire bats love 9–10 inches (22–25 the taste of blood. centimeters). They This one has sliced live in northern Europe. open the foot of a sleeping chicken with its sharp teeth. It will lap up about one tablespoonful of blood. Sounds tasty Many bats can’t see well enough to fly in the dark, so they use their voice and ears instead! American fishing bats make clicking noises as they fly over ponds. When these sounds bounce back off ripples, they know that a fish is near to the surface. The bat hears the tiny echo and swiftly swoops down to grab the fish. 203

SMRAOLDL ENTS These newborn, rubbery, wriggling mice can only squeak, sleep, and suckle. A rodent is an animal that gnaws with sharp, chisel-shaped teeth. Most are mouselike and Moving house vegetarian: they nibble plant stems, seeds, Every three or four years, and roots. Forty percent of all mammals thousands of lemmings run from their overcrowded homes. are rodents. They live all over the world, Many die in the frantic search for new places to live and feed. from African jungles where crested rats clamber up trees, to scorching deserts where jerboas hop across the sand. House mice have even hitched rides on ships to reach huts in Antarctica. Dormouse A plague of rats The greasy fur leaves dirty Every year, millions marks on things it touches. of nibbling rats wreck one fifth of Flat teeth in the the world’s crops! back of a rat’s Many brown rats live mouth grind up in sewers.They use their grass and grains. feet as paddles when they swim and can tread water for three days! Scaly After walking through tail dirt, rats may walk over food and spread diseases. 204

Straw They are 18 days The most nest old and ready common mammal to leave home. House mice are small Their eyes begin to open and fur appears when and cannot defend they are 10 days old. themselves. The species survives by having lots of babies. A female can give birth when she is six weeks old and have 10 litters a year. If all her babies survived, she could have a million descendants when she was one year old! Out on a limb Harvest mice climb up small plants, like monkeys in a tall tree! They hold on tightly with their tails. Harvest mice weigh less Nonstop teeth than a fifth of an ounce Your adult teeth grow in the spaces left (five grams) so they rarely break a “branch.” behind by your baby teeth. When they have filled the gap, they stop growing. Rodents’ front teeth are different—they never stop growing! They get worn down by the tough food that the rodents eat. Rodents even Growing chew soap. tooth Tiny nibblers Indian Fat dormouse Crested gerbil rat Pale Great kangaroo mouse jerboa Sagebrush vole 205

L ARGE RODENTS Most rodents are small and look like Size of a sheep! mice, but some are much bigger. The capybara is the There are two sorts of large largest rodent in the rodents—those that world. It is a relative Chipmunks look like squirrels and of the guinea pig. those, such as porcupines, that look like pigs. The lion lost Rodents’ teeth get worn down by gnawing, and A porcupine will all rodents have front teeth that keep growing throughout their lives. run backward and stick its A porcupine can quills into an hear fruit drop to attacker’s face! the ground several Hollow, yards away. striped quill Porcupines chew The sharp quills only stick up The nest, old bones to keep when the porcupine is attacked. or drey, is about their teeth sharp. the size of a football. Busy nibblers Chinchilla Rock cavy Angry African porcupines stamp their back feet to rattle their quills. European This tells other animals to go away. red squirrel Springhare Woodchuck 206

A squirrel’s Digging “dogs” strong jaws Prairie dogs live in underground towns! These towns usually can crack have a population of about 1,000, but one in Texas had open acorns. more than 400 million prairie dogs in it. Planting trees The “garden” Watch Prairie dogs touch teeth Squirrels bury nuts is weeded. “dog” when they meet. to eat later. Those that they can’t find again may grow into trees. Warm, leafy lining When it sleeps, the Tufted squirrel squirrel wraps its European red squirrels don’t bushy tail around scamper through gardens and itself like a blanket. parks like their gray American cousins. They are shy and hide from people in forests. Grey squirrels race through trees at up to 24 km (15 miles) per hour. A gray squirrel can leap more than six meters (20 feet) from one tree to another. Squirrels can walk up and A hole in the down the sides of trees to roof lets in air. reach their nests. The house, or Timber! The underwater lodge, is the size Beavers are excellent builders. They bite entrance keeps of a large tent. through trees with their teeth and then out enemies. pile up the logs in a river. Behind this Food dam, a pond soon forms where they storage can build their home. Dam

TFHAEMHILOYRSE Almost all the horses in the world are tame. The only wild species left is the Przewalski’s horse. It survives in zoos. The most common Desert “donkeys” wild member of the horse family today is not Wild asses are shy and rare. They live in the dry Przewalski’s a horse, but a zebra. A zebra’s North African deserts. horse Fast, striped zebras mane stands up straight. are herbivores—they chew grass with their flat back teeth. Horses, zebras, and asses walk on the tips of their toes, which are hidden inside hard “shoes,” called hooves. The ears twist around to listen for danger. Plains zebras are up to 5 feet (1.5 meters) tall at the shoulder. They live in Africa. Best friends The hoof is Foals can Zebras and wildebeest just a large walk when like to live together. toenail! they are a few The zebras keep 208 minutes old. watch, while wildebeest sniff the air for lions. Wildebeest eat the short grass left by the zebras.

Quick, run! All four hooves Long legs are best Asses, zebras, and horses leave the ground for taking big steps can run at speeds of up to when it gallops. and running fast. 40 miles (65 kilometers) per hour. Plains zebras are plump. Spot the zebra! Trespassers will be kicked Nobody knows why zebras Mountain zebras don’t live in are striped. Maybe their crazy herds. Each male, or stallion, pattern confuses lions, making it “owns” a patch of land, called hard for them to pick their prey. a territory. He will chase off any male zebra that enters his home. A zebra scratches its back by rolling on the ground. Big thigh The swishing tail swats muscles annoying, buzzing flies. power plains Females, foals, and stallions zebras across live together in the same herd. the African grasslands. Make your mark Born free There is only one toe Your fingerprints are Some of the 75 million tame horses inside this hard hoof. different from everyone have escaped and learned to live in else’s. So are a zebra’s the wild. The ancestors of these stripes—each zebra has a American “wild” horses, called different-patterned coat! mustangs, belonged to cowboys. Some even have thin, white stripes on a black background. 209

HANIPDPOPSE, PCCIGASR,IES Hippo is short for hippopotamus, which means “river horse.” They are called river Very important pig horses because they live in rivers and lakes, Farmyard pigs have all and eat grass. Pigs and peccaries do not been bred from wild boars. live in rivers, but they enjoy wallowing in mud as much as their huge relatives. Although these water-loving mammals are not carnivores, they are all able to protect themselves. Wild pigs can stab and kill tigers with their tusks, peccaries fight jaguars, and a heavy hippo will tussle with a crocodile or smash into a boat! Built-in suntan lotion Hippo skin oozes tiny blobs of pink liquid. This oil stops their skin from drying out and also protects them from sunburn. Open wide The eyes and nostrils are high You yawn when you are tired or bored, up on a hippo’s head.This but male hippos yawn when they are means it can stick just the top angry! Smaller males are frightened of its head out of the water and still see and breathe. off by the big teeth and swim away without starting a fight. Smooth, almost hairless, skin. Hippos are 5 feet (1.5 The 1.5 feet-long meters) tall. They live (half meter) tusks are in Africa. sometimes used to stab crocodiles. This big male hippo weighs as much as 120 eight-year-old children!

Lumbering lawn mowers Every night, hippos leave the water and spend five or six hours grazing. They march back into the water, down well-worn paths, long before the scorching sun rises. Plucky peccary If a mountain lion attacks a group of peccaries, one brave animal may charge the lion with its sharp tusks while the others escape, but it will be lucky to survive. Pigs on parade Bush pig Collared peccary To keep cool and Underwater ballet moist, hippos spend Hippos can hold their breath for more than five 16 hours a day up to minutes. This is plenty of time to dive down and their necks in water. tiptoe gracefully across the bottom of the lake. The hippo shuts its ears and nostrils when it is under water. There are four Hippo toes on each foot. Pygmy hippo Thick skin protects the hippo from snapping crocodiles. Hippos do eat water lilies, but prefer grass.

TFHAEMCILAYMEL The fat inside a camel’s humps Camels and their smaller South is an energy store, American relatives, vicuñas so it can survive and guanacos, are found on sandy a long time deserts, rocky plains, and bare without food. mountains. They survive in some of the harshest places on Earth. Vicuñas can breathe thin mountain air and camels can cope with freezing nights and scorching desert days. People have made good use of these animals’ amazing survival skills—most are domesticated and work for a living. There are few wild members of the camel family left. Domestic dromedary The rumen is the Food is brought Desert people could not large part of the back up from stomach where the rumen to survive without their chewed food be rechewed. one-humped camels. goes first to They are ridden, milked, be partly Second and eaten. Camel skin digested. stomach is made into shoes, hair is woven into clothes, Third and dry droppings are stomach used as fuel! Swallow that! Camels can go for months without water, then drink up to 29 gallons (130 liters) of water in 13 minutes. Twice as tasty To get all the goodness out of grass, some mammals, such as camels, deer, and cattle, have more than one stomach and chew their food twice! 212

The ears and Two rows of eyelashes A camel doesn’t waste water. How many nostrils can be keep out sand and stop Liquid from its runny nose drips humps? pressed flat to their eyes from freezing down the split lip into its mouth! keep out sand. on cold desert nights. Dromedary Bactrian camels are 7 feet (2.2 meters) tall. They live in the Gobi desert in Asia. Camels spit at things that annoy them. Tough lips can grip thorny desert plants. Camels hardly Bactrian camel ever sweat.This saves water. King of the castle While the females graze, the male vicuña stands on a rock. If it spots a mountain lion, it whistles and the fleecy females flee. Guanaco Camels roll Hardworking mammals Vicuña from side to Llamas and alpacas have Alpaca side when they walk been bred by people from because they lift both legs wild guanacos. Llamas are Llama on one side at the same time. milked and used to carry The two toes spread heavy loads. Alpacas are out to stop the kept for their fine wool. camel from sinking into soft sand. 213

CAATNTTLEELAONPEDS Roundup Musk oxen form a ring Cattle, antelopes, and their relatives goats around their babies to and sheep, are all bovids.This means protect them from hungry that they have horns attached to wolves—who can’t get the tops of their heads. Horns have through the circle of horns. a bony core and an outer layer made of the same stuff as your fingernails. All cattle have Gerenuk antelopes eat leaves, but four stomachs! Gerenuk bison prefer to graze on grass. Like (male) all bovids, they make the most of their poor-quality food by coughing up partly digested food and chewing it a second time. This is called chewing the cud. These horns are about half as tall as you! Arabian This rare Arabian oryx oryx antelope chews the cud as it walks across the desert. On the march Like all At the beginning of the dry season, huge herds cattle, bison of wildebeest walk more than 990 miles have split (1,600 km) to wetter, greener pastures. When the wet season begins, they come back. These hooves. long, yearly journeys are called migrations. It sniffs the air for rain and then walks to where the grass is growing. 214

Built-in radiator Heads with horns The Tibetan yak lives African buffalo (male) near the top of the world in the Himalayan A dark coat soaks up the sun’s mountains. It does not heat.This helps to keep the get cold because it has bison warm in cold weather. its own central heating system—the moss being digested in its stomach is hot and keeps it warm. This thick, winter coat falls off in big clumps during the spring. Male bison fight for females by Blackbuck (male) putting their heads together and pushing.The winner is the one who pushes the other backward. Horns are different than antlers.They never form branches or stop growing, and they are not replaced each year. Male bison weigh Wild goat (male) more than a small car! American bison are 6.5 feet (two meters) tall. They live in Canada and the US. Herds of bison spend most Bighorn sheep (male) of the day eating grass and most of the night chewing!

ELEPHANTS Matriarch Elephants have enormous ears, A family of females long noses, tusks—and weigh The leader of a herd of more than six cars. They are the elephants is an old female, biggest land mammals. Herds of called a matriarch. She is elephants shape the land they live followed by all her female in by treading paths that are wide enough relatives and their babies. to stop bush fires, by digging wells in dry riverbeds, by fertilizing the ground with dung, and by trampling grass for zebras to eat. They also open up forests by pushing over trees! Wrinkles trap water to Elephants help to keep them cool. never stop Ivory towers growing. Many elephants are killed for their valuable ivory tusks. People have burned huge piles of old tusks to show that they want this cruelty to stop. It’s all relative Tusks are teeth. The elephant’s closest relative, They grow about the hyrax, looks like a guinea pig! 7 inches (17 Millions of years ago they were centimeters) a huge. All that elephants and year and can be hyraxes have in common now are as long as a car! tusks and nails instead of hooves. Elephants eat grass, bark, and Who’s who? Taller leaves for up to 16 hours a day. There are two sorts of elephants. Humped Smaller Longer Bigger, back ears tusks rounder ears This toenail is bigger than your whole hand! Asian African 216

Young females Males leave their families act as nannies. when they are about fourteen. An African elephant’s ears Stay cool are almost as Elephants have lots of big as sheets for ways of cooling their big a single bed! bodies. They can wallow in mud or throw water and dust over their skin. Sometimes they flap their ears like giant fans! The elephant spreads out its ears to make itself look bigger and more dangerous. Elephants keep in This is one of The sixth, and touch by making the first four teeth. last, set of teeth are deep, rumbling noises bigger than bricks! in their tummies! The bendy trunk is formed from the nose and the upper lip. It is used for breathing, smelling, touching, and picking up things. What’s inside? Elephants may Toe look like they have flat feet, but they Always teething! really walk on Other than tusks, elephants have only four their tiptoes! teeth. These molars are replaced every few years. Bigger teeth appear at the back of the mouth and push out the old, worn The heel rests on teeth—like a conveyor belt of teeth! a fatty cushion. 217

HTHUEMAN BODY Your body is one of the most amazing machines in the world. It is made up of thousands of parts all working together. Each group of parts is called a system. The body is so complicated that it is easier to imagine the different systems separately. But your digestive system, nervous system, skeleton, blood or circulatory system, and muscles all work together.You need all of them to stay alive. When you are born, all you can do is sleep, eat, and cry. It takes time to discover how the parts of your body move and how to get them to work together. As you grow, you learn to do more difficult things, like crawling, walking, and riding a bicycle. Human skull There are over 100 muscles in your face. Digestive system 218

Walking Hopping Skipping (about 15 months) (about (about Crawling 4 years) 5 years) (about 10 months) Riding a two-wheeled bicycle (about 5 years) Nervous Skeleton Circulatory Muscles system system 219

“Canaphone” HEARING A piece of string Hearing is one of your five senses.Your threaded through ears are important and delicate: they pick two empty cans up sounds and send messages to your works kind of like brain. Sounds travel through the air in a telephone. If you waves.Your outer ears, the shell-shaped speak into one can, flaps on the side of your head, catch sound the vibrations waves and funnel them inside. These waves travel along the hit the eardrum and make it vibrate. The string to the other middle ear and the inner ear change the can—allowing vibrations into electrical signals, which are your voice to sorted out and recognized by your brain. be heard. The outer ear collects the sounds and funnels them along the ear canal. Kneel Crash! The loudness of sound is measured in decibels. Quiet whispering is less than 25 decibels, the clash of cymbals about 90, and a jet plane taking off can measure more than 130 decibels. Noises over 120 decibels can cause pain and may damage your ears. Hunger Talking in signs Hope If deaf people have never heard speech, they may not have learned to talk. To help them to communicate, many learn a special language called signing. There are many different forms of sign language used in different countries and regions. Deaf people also learn to spell using their hands, and to read lips by watching the shape of people’s mouths as they speak. 220

Three tiny, connected bones in the Hello . . . hello! middle ear—the hammer, anvil, If you shout in a large, empty space, the sound and stirrup—pass sound vibrations waves from your voice bounce off the nearest from the eardrum to the cochlea. surface, back to your ears. This is called an echo. The farther a sound has to travel before it is The semicircular reflected, the longer you must wait for the echo. canals help you balance. Nerves Nerve cells in the cochlea send messages about sounds to the brain. The inner ear is made up of the cochlea and the semicircular canals. It is filled with liquid. The eardrum is Visible and invisible ears Elephants a thin sheet of skin Not all animals hear the have huge that vibrates when same way you do. Some do ear flaps and sound waves hit not have any ears on the good hearing. it— just like the outside of their body. skin on a drum. Birds and lizards have good hearing but no ear flaps on the sides of their heads. A rabbit can turn its ears to hear sounds all around it. 221

SEEING Sight is perhaps the most important of your five senses. Tear-full Your eyes work together with your brain to help you Tears help to keep your to see. The cornea, at the front of your eye, bends light. eyes moist and clean. This light is then focused by the lens, to form an image When too many are of what you are looking at on the retina at the back of made, they cannot all your eye. But the image is upside down! Nerve cells in drain away down your the retina send messages to your brain, which sorts out nose, so tears come the messages so that you see things the right way. out of your eyes. Tricky eyes Sometimes your eyes play tricks on you, called optical illusions. Try these: Which of these two girls is the taller? Which red circle is Which line is longer? Double vision? bigger: the left one Because they are set apart, or the right one? each of your eyes sees a slightly different picture. Your brain Eye spy puts the two pictures together. You can have your eyes tested by This is called stereoscopic or an optician to make sure they are binocular vision, and it means working properly. Glasses or contact you can judge depth and distances. Try this: close one lenses will help if you cannot see eye, point to something, and clearly.Your eyes are very important, keep your finger still. Now look so have them checked regularly! through the other eye. Are you still pointing to the same place?

Eyebrow hairs stop The retina is at the drops of sweat from back of the eye. Cells getting into your eyes. on the retina, called rods and cones, help The eyelids are lowered like a you to make sense of protective cover if danger approaches light and colors. the eye.They also wash your eyes every time you blink. The conjunctiva The white part of the eye is called is transparent, the sclera. At the front it becomes like a window. transparent and is called the cornea. It protects the The cornea bends the light. front of your eye. The optic nerve Light enters sends messages the eye through from your eye the pupil. to your brain. Iris The lens helps Eyelashes protect your your eye to focus. eyes, and stop dirt and Six muscles control each eye and let you grit from getting in. move your eyes in almost any direction. But both eyes work together. Muscles around Black hole the eye allow you The black part of your eye is a hole, to blink every two to called the pupil. A colored muscle, ten seconds. So even the iris, makes this hole get smaller in when you are awake bright light to let in less light, and bigger you have your eyes in dim light to let in more. shut for at least half an hour each day! 223

BRAIN Brain protection Inside your head, protected by a bony To stop you from injuring skull, is your brain. It looks crinkled your brain, you should like a walnut and is the control center wear a helmet whenever for your entire body.Your heart you take part in a sport pumps oxygen-filled blood into it that might make you hit through a mass of tubes, called arteries. your head. After only four minutes without oxygen, brain cells will die and they cannot be replaced.Your brain is very complex and is divided into many parts that have different functions. The largest and uppermost part in the human brain is called the cerebrum. It has two halves, called hemispheres. The outermost layer of the cerebrum also contains sections known as lobes, which control different activities and make sense of the information from your five senses. The frontal lobe is the part of the brain where you do your big thinking.You use it when you make a decision or solve a problem. It also allows you to communicate with other people and express your own unique personality. Brain control The brain stem Your brain is the most controls many important part of of your automatic actions, such as your body. It is your your heartbeat control center, but and breathing. is only a little bigger than your two fists! Each part of your brain has a different job to do. Some parts send out signals to your body and some parts make sense of signals that come in. 224

Kim’s game Different brains When we are learning, we Animals have brains depend on our memory to of various shapes and sizes, suited help us.Test your memory to the things with this game. Set out they do. a number of objects and look at them for a few Fish moments. Ask a friend to remove an object, then try to tell what is missing. The parietal lobe has many Bird functions, such as processing signals associated with taste and touch. The temporal lobe is connected with your sense of hearing. It helps you to understand sounds, including people talking. Cat The occipital lobe is connected with your sense of sight. It helps control eye movement, makes sense of what you see, and allows you to remember things that you’ve seen before. Human The cerebellum is a Brain relay structure at the base of When you want to touch something, your brain. It controls a signal is passed from your brain many of your voluntary to other parts of your body like muscle movements, such a baton in a relay race. It goes first as balancing, walking, to the spinal nerves then to the motor writing, and speaking. nerves, which tell muscles to move. Brain Spinal Motor nerves nerves 225

NERVES Nerves are like telephone wires carrying information between the brain and all parts Speedy reflex If someone claps their of the body. One set of nerves—the sensory hands by your face, your nerves—carries signals to your brain from brain thinks something your senses, telling your brain what is is flying toward your happening around you. When your brain eyes and they blink. has decided what to do, it sends signals This blink is a reflex along another set of nerves—the motor action to protect them. nerves—to make your muscles work. With your Nerve network What’s on the “feely table?” eyes covered, The sense of touch is very important. can you tell it It is one of your five senses. Receptor is a teddy bear? cells under your skin send messages, through sensory nerves, to your brain about what your fingers are feeling. A bottle feels hard and smooth. Reading by touch Blind people cannot see to read, so they learn a special alphabet of raised dots, called braille. They feel these dots with their fingertips. Get the message? Messages about how objects feel are sent through the sensory nerves and the spinal nerves to the brain to be understood. Sensory nerves Spinal nerves Brain If you touch Ice is cold and some honey, your slippery.When fingers will feel it starts to melt that it is sticky. it feels wet. 226

Blindfold Skin sense The wood Find out which part of your feels hard and rough. skin is most sensitive with this test. Close your eyes and ask a friend to touch different parts of your body with the points of two pencils. Try this test on your fingertips and on your knee to see which parts feel two points and which feel only one. Your fingers can tell if something is soft. It feels good to use towels made of soft material. Hot things are good to feel when you are cold—but if something is too hot your nerves will send messages to make your hand move away quickly. Even when you are blindfolded, you can feel that this smooth, round object is a ball. The bristles on this brush are sharp and prickly. Feathers are very Your eyes tell your brain that something may light and soft.They be heavy.Your muscles are then prepared to can sometimes tickle, especially if lift a heavy weight. If you cannot see the weight, you stroke your face gently with them. you may be surprised when you try to lift it! 227

SKIN New skin grows all the time to replace If you could unwrap your skin, you might be surprised old skin that rubs off. at how much you have—enough to cover a large towel. Most house dust is It goes over all your bumps and curves, and into every really old, dead skin! crease of your body.Your skin grows with you, so that The thinnest when you are an adult it will cover an area of about skin is on 5.6 square feet (1.7 square meters). It is waterproof your eyelids. and protective, and can heal itself if it gets damaged. Personal prints Hairs grow on every part of Fingerprints are patterns of lines and your skin except for your lips, swirls on your fingers. Try printing yours the palms of your hands, using paint or ink! Everyone has different and the soles of fingerprints, so they are used to identify your feet. people. There are three basic patterns. Arch Loop Whorl A fingernail takes about six months to grow from base to tip. It grows about 0.02 inches (half a millimeter) a week. Nails are made of dead cells which contain a protein called keratin. The cuticle is the fold of skin overlapping the nail bed from where the nail grows. The half moon at the base of your nail looks white because this part is not firmly attached to the skin below. 228

Shades All skin contains a coloring substance called melanin. Dark skin contains more melanin than fair skin. As a protection from burning by the sun, the skin produces more melanin, which tans the skin a darker color. The roots of your hair are alive and grow about 0.08 inches (two millimeters) a week.When the hairs reach the surface of your skin they die— so having your hair cut does not hurt! Growing old Your skin is elastic. If you pinch the back of your hand and then release it, the skin goes back to its original place. As people get older their skin becomes less elastic and often gets wrinkled. Some people’s hair turns gray because it stops making melanin. Dead or alive? Hair Your skin has two layers. The dead, A pore is the opening outer layer, called the epidermis, of a sweat gland. protects the living dermis underneath. Hair styles Epidermis How straight or curly a hair is depends upon Dermis Nerve ending the shape of the pocket, Sweat glands or follicle, it grows from. open to let Oil glands The color of your hair moisture out of your stop skin from depends upon the skin to help keep you cool. drying out. amount of black or Hair follicle red melanin there is Blood vessels bring food inside these pockets. and oxygen to the skin. 229

BLOOD Arteriole Artery Aorta (largest artery) Blood is pumped all around your body There . . . Blood vessels that by your heart. It travels in long tubes take blood away called blood vessels. Before it begins this from your heart journey, it is pushed to your lungs to are called arteries. collect oxygen. Then it returns to your heart to be pumped around your body. Blood also carries nutrients from your food to the cells. Power pump Your heart is made of strong muscle. In just one minute, it can pump a drop of blood all the way down to your toes and back to your heart again. The heart is divided into four spaces Aorta Flaps, called called chambers, two at the top and valves, stop blood two at the bottom.There is a wall from flowing the of muscle down the middle. wrong way. It is the Blood enters the top right chamber “lub-dub” sound of through the vena cava. It passes down these doors closing to the bottom right chamber.Then that you hear when it is pushed out to your lungs. your heart beats. Blood, filled with oxygen from the lungs, comes into the top left chamber. It passes down to the bottom left chamber.Then it is pumped around your body. After going around your body, the blood returns to the right side of your heart, to start the journey again. 230

Venule Vein Feeling the pressure You can feel the beat of your Vena cava heart as it pumps blood, at high (largest vein) pressure, through your arteries. This beat is called the pulse. . . . and back Put the fingers of one hand on the inside Those that take blood of your other wrist, in line with your thumb. back to your heart are You can feel your pulse beating there. called veins. You can only hear a heartbeat by using a stethoscope or by putting your ear to a friend’s chest. Heart work Side view of a When you skip, or do any red blood cell kind of exercise, your muscles need extra oxygen and food from your blood. To provide this, your heart has to pump faster. You have nearly one gallon (about four liters) of blood in your body. An adult has more and a baby has less. A drop of blood goes around your body more than a thousand times a day. Every five minutes all your blood passes through your kidneys to be cleaned. Super cells Red cells carry oxygen In one tiny drop of blood around the body.They are there are red cells, white made in the bone marrow. cells, and platelets, all floating in a liquid called plasma. White blood The blood in your arteries is cells defend the carrying more oxygen, which body against germs. makes it a brighter red color than the blood in your veins. If you cut yourself, platelets rush to the broken blood vessel and stick themselves together to plug the cut.

BREATHING You must breathe all the time to stay alive. If you try to hold your breath for more than about a minute, your body will force you to start breathing again. The Lung capacity air that you breathe is made up of many different gases Breathe in deeply. mixed together, but your body only needs one of them, Blow into a balloon oxygen, to keep you alive. If you ran out of oxygen, until you run out of even for a very short time, you would die. The air you breath. Tie a knot breathe goes into two soft, moist sponges, called lungs. in the balloon. Now You have one on each side of your chest. you can see just how Bronchus much air your lungs are able to hold. Right lung Bad breath! Heart The air that you breathe can contain things that are bad for you. This woman is wearing a mask to protect herself from car fumes. Blood vessels surround the alveoli. Alveoli are stretchy, Some air is always so they can blow up left in your lungs like balloons. Gases can pass right through the because they would alveoli’s stretched skin. collapse if they were Oxygen seeps from the alveoli completely empty. into the blood. A waste gas, called 232 carbon dioxide, seeps from the blood back into the alveoli to be breathed out.

You breathe air in Hot air through a tube called The air that you breathe out the windpipe, or trachea. is warm and has water in it. You can see this if you breathe onto a mirror. The water in your breath cools down and forms a mist as it hits the cold mirror. If you touch the mirror you can feel the moisture.You can also see the water misting up when you breathe out on a cold day. Air enters the Breathe in Breathe out lungs through two A powerful muscle When your large tubes called called the diaphragm diaphragm relaxes, the bronchi. Each helps you breathe air it moves back up bronchus divides into into both your lungs. again and squashes smaller and smaller When this muscle is your lungs. There tubes ending in tiny pulled tight, it moves is no longer enough sacs called alveoli. downward, leaving space in your lungs Your ribs form a more space for the for all the air, so cage.They protect lungs. As the lungs it is squeezed up your lungs. spread out to fill your windpipe this larger space, and out of your they suck in air. nose or mouth. Mucus Dirt Sneezing Coughing Laughing Tiny “hairs” A sudden rush of Dust or germs in The diaphragm trap dirt. built-up air blows the tubes of your jerks, forcing air up dust or germs lungs are forced through your voice from your nose. out quickly. box and windpipe. Little “brushes” Special cells help to push dirt Wall of out of your body. the bronchus 233

TASTE AND SMELL Your senses of taste and smell are very closely linked. They depend on each other. Tiny dimples on your tongue, and hairs at the top of the inside of your nose, detect chemicals that cause tastes and smells. Special sensory cells then send messages through to your brain to be recognized.Your sense of smell is twenty thousand times stronger than your sense of taste! Often what you think you are tasting you are really just smelling. When you want to smell The smell of tasty food something, you have to suck automatically makes air right up to the top of you produce saliva. your nose to reach your smell sense cells. Nice and not so nice You are able to distinguish several thousand different smells. The clean smell of the countryside can be lovely, but the smell of milk that has spoiled is horrible. Bad smells can warn you not to drink or eat things that are not fresh. The roof of your mouth, the back of your throat, and your tongue are covered in small dimples called taste buds. As the food is pushed around your mouth by your tongue, your taste buds pick up its taste. Taste buds can only detect the flavors of food that has been dissolved in saliva.

Trick your taste buds When you eat something, your sense of smell helps you to get the flavor. Block your nose and taste carrot and cucumber. It is hard to tell the difference between them. If you hold a piece of onion under someone’s nose and give them mashed apple to eat, they think they are eating onion. This is why you cannot taste your food properly when you have a cold. Coffee grains Still hungry? are bitter. The look of food is important as Lemon well as its taste and is sour. smell—pink sweetcorn Kippers still tastes like sweetcorn, are salty. but would you want to eat it? Honey is sweet. Five tastes Busy buds You have around 20,000 If you look at a tongue through a strong taste buds on your tongue, which pick up magnifying glass you can see lots of bumps. five different types of taste: salty, sweet, Around the base of these bumps there are bitter, sour, and umami (savory). taste buds. Inside them there are special cells that sense taste. 235

TEETH You use your teeth to break food into pieces that are small enough to swallow. Some teeth are shaped for biting and others for chewing.You have two sets of teeth. The first set are called baby teeth, and there are 20 of them. At the age of about six, you start to lose your baby Gappy grin teeth. One by one, the second Children are left with set, the 32 adult teeth, grow gaps where their baby in their place. Teeth are strong teeth have fallen out and keep working for many years. and they are waiting for their adult teeth to come through. Cases for braces Healthy gums are just Sometimes teeth grow crookedly as important as healthy or become overcrowded in teeth—they help to hold the mouth. Often this can be your teeth in place. corrected by wearing braces. Still rooted This skull shows how teeth are rooted firmly in the strong bone of the upper and lower jaws. Complete set Jawbone A full set of adult teeth has eight incisors, four canines, eight premolars, and twelve molars. Four of the molars are called wisdom teeth. Incisors Canine Premolar Molars 236

Inside story Enamel is the hardest Your teeth are alive. substance your body The part that sticks out makes. A thin layer of from your gum is the it covers all your teeth. crown. The part under the gum is the root. Gum Nerve Under the Jawbone Brushing up enamel there The soft, middle part If you don’t keep your teeth clean, is a layer of hard, of the tooth is called bacteria build up to form a layer called bonelike material the pulp. It contains plaque. If plaque builds up on your called dentine. nerves and blood vessels. teeth, it can cause them to decay and Canine teeth are even fall out. Brushing your teeth and sharp and pointed. Your bumpy back teeth gums after meals and before going to They are used for are called molars.They bed helps to remove the sugary tearing food. crush and grind food foods that the bacteria use to grow. when you chew. Sometimes The sharp, chisel-shaped people have teeth at the front of your extra teeth. mouth are incisors. There are They can cut and molars on the bottom, too. bite tough food. At about the age of eighteen, wisdom teeth may come through at the back of your mouth—but they don’t make you wise! Premolars have two edges, or cusps.They tear and grind up your food.

EATING 1. Food starts being Food is the fuel that provides digested in your mouth. energy for your body. The Your spit, or saliva, has energy is measured in units In and out called calories. Before a digestive juice The inside wall of which starts to the small intestine has break down a very bumpy surface. your body can use the the food. food you eat, it has to Your liver is be broken down into tiny bits that are a “chemical small enough to pass into your blood. factory.” It This digestion takes about 24 hours, also stores as the food flows through a long vitamins. tube winding all the way from your mouth to your bottom. Large intestine Windpipe Small intestine 2. The food travels down a food pipe called the gullet. 3. Your stomach is a thick bag. Food is churned up inside it and mixed with strong stomach juices to make a kind of soup. 4. After leaving your stomach, your food flows down your small intestine. Goodness from the food seeps through the thin walls into your blood. Fats Vitamins Get into groups! and minerals Proteins 6. Your bladder stores Foods can be put into groups. Fats 5. Your large intestine takes urine.When it fills up and carbohydrates provide you with back the water from digested you need to go to the energy. Vitamins and minerals keep you food. Later it is passed out of bathroom to empty it. healthy. Proteins build cells and help your body through your anus. your body to grow and repair itself. 238

A lump in the throat You can swallow even if you are standing on your head! This is because your food does not slide down through you—it is squeezed along by muscles in your digestive tube. This is called peristalsis and it happens all the time, without you having to think about it. The muscles of a snake can squeeze an egg through its body in the same way. Walking uses about 240 calories an hour Sleeping uses about Basketball and 65 calories an hour other vigorous sports use about Drawing uses 550 calories an hour about 85 calories Fuel burning an hour If a car travels very fast, it uses up more fuel than if it goes slowly. You have two kidneys. The same is true of your body. Each one is about the When you exercise you use up more size of your clenched fist. calories than when you are asleep. Narrow tubes, called ureters, take urine from the kidneys to the bladder. Carbohydrates How long? Any water your body If you could stretch your does not need is turned whole digestive system into urine by your kidneys. out in a straight line, it would be about 33 feet (10 meters) long! 239

MUSCLES Try to sit as still as you can. Is anything moving? Even when you think you are completely still, many parts of your body are moving. Your heart is beating and your intestines and lungs are working. All these movements are made by muscles.You have more than Your brain sends 600 muscles spread throughout messages to your muscles and makes your body. Every bend, stretch, them move. twist, and turn you make depends on them.You use about 200 muscles each time you take a step, and many more when you jump. Muscle food The largest muscle To keep your muscles working in your body is the gluteus maximus properly you need a diet that muscle in your includes protein. Foods that are full thigh and bottom. of protein include meat, eggs, cheese, If you stand on tiptoe, you can see and dried beans. your calf muscles in the back of your leg. Biceps Arm bend contracts Muscles are attached to bones and Before you begin to make any strenuous make them move. But they can only movements, you pull; they cannot push—which is why should always warm Up they always work in pairs. In your arm, up your muscles by doing the biceps and triceps muscles work gentle warm-up and Triceps together to move it up and down. stretching exercises. relaxes Biceps When the biceps pulls, or contracts, relaxes it gets shorter and fatter and bends the arm. Down As the biceps pulls, the Triceps contracts triceps muscle relaxes. 240

Holding hands Cheeky! The muscles in your hands allow Your tongue is a group of strong you to make delicate, accurate, or muscles which help you powerful movements.Your flexible to eat and speak—and fingers are attached to many small also to lick your lips . . . muscles which are useful for precise or your chin . . . jobs.Your fingers and thumb work together to let you hold things tightly. Your hands are strong enough to support your entire body if you hang from a bar. The longest muscle in your or your nose . . . body is the sartorius muscle or your cheek! in the upper leg. Some of your arm muscles are attached to bones in your back. This strong anchor enables you to pick up heavier things. It takes about 15 muscles to smile! You learned how to control your bladder muscles as you grew older. Tendons are the tough The muscles in cords that join the muscle your intestines are firmly to the bone. You can pushing food along feel one of them, called the all the time. Achilles tendon, in the back of your ankle. 241

SKELETON Yes and no bones Without a frame to support The bones of your spine are your body you would collapse, called vertebrae. The top two lose your shape, and be unable vertebrae, the atlas and axis, to move.Your body’s frame is called a skeleton. It gives your fit together to allow body strength and it protects the your head to nod soft parts inside.Your skeleton and to move from is made up of more than 200 side to side. bones. They are light enough to allow you to move around easily, Atlas and they have joints so that you can bend Axis your body to do many things. Your nose is not You have twelve pairs of ribs.They made of bone but of are all joined to a row of bones in your back called your spine. rubbery material called cartilage. From the side, your spine looks Ulna If you look at curved, like the letter S. It helps a skeleton, you you to stand up straight. will not see a nose bone, only Femur a nose hole. Radius A tall order Your bones keep growing until Fibula you are in your early 20s. Tibia Your ankle is a You cannot change your joint. It is made height—it is decided in up of bones in your genes and passed the foot and the on from your parents. ends of the leg But you are about half bones, the tibia an inch (one centimeter) and fibula. shorter in the evening than you are in the morning! This is because the pads of cartilage in your spine get squashed as you walk around all day. 242

Soft center Inside information Some animals, such as this crab, Your bones are all hidden do not have a skeleton inside inside your body. So if them. Instead, they have a hard doctors want to look at outer covering, called them, they have to take an exoskeleton. special photographs, called X-rays. The X-ray camera can see straight through your skin and show what the bones look like. On this X-ray of a hand, you can see that the bone connected to the little finger is broken. Your hip joint is where the end of the Bones give muscles a place to hang on thigh bone, or femur, fits into a socket to, but without these muscles, the bones in your pelvis.This joint helps you to would not be able to move. Muscle power bend your body almost in half. is transferred to the bones along strong bands called tendons. Your basin-shaped pelvis supports the upper half of your body and also protects soft parts, such as your bladder. Your spine can only curve gently. If it bent any further it would damage your spinal cord—the nerve cable that carries messages to and from your brain. Skull Your arm can The muscles that control the only bend at thumb and fingers begin here. the elbow. They are attached to two arm bones called the radius and the ulna. 243

BONES Your bones are hard and strong. They are not solid though, so they are not as heavy as you would think. In fact, they only make up 14 percent of your total body weight—they are lighter than your muscles. Bones are not dead and dry. They are living, and can repair themselves if they break.Your body is made up of lots of bones all working together and linked by joints. If you had no knee joints, you would have to walk with stiff legs. What’s inside a bone? Crisscross The outer part of all your bones struts is hard and tough, but the inside of many of them is spongy. These lightweight, soft centers are crisscrossed by small struts which make your bones strong, but not too heavy. This idea of strength without weight is copied in buildings such Some bones are Your two feet as the Eiffel Tower. filled with jellylike contain one quarter marrow. Platelets of the bones in your The spongy inner bone and red and white whole body! looks like a honeycomb. blood cells are made in the bone Blood vessels take oxygen marrow. and food to bone cells. Your neck is much shorter than a giraffe’s, but it has the same number of vertebrae! The tiny tailbones at the end of your spine, called the coccyx, help to support your body when you sit down. 244

The bones in your Baby bones hand are all linked Newborn babies have soft bones. Their bones are together by muscles, mostly made of cartilage, a tough, rubbery material tendons, and that gradually becomes hard. In this X-ray ligaments. of a child’s hand, you can see the areas of cartilage where, later, bones will grow. Cartilage There are 27 small bones in your hand. Bones fit together like a jigsaw puzzle. Bone work You have three kinds of bones—long bones such as those in your legs, short bones such as those in Your thumb is special. It has a saddle joint in it which allows your hand and spine, and flat bones such as your you to move your thumb shoulder and skull. Bones are linked by different kinds of joints, which in two directions. allow them to move You have flat in different ways. gliding joints in your foot. Your kneecap, or patella, protects The shoulder has a your knee. ball-and-socket joint. The round end of one bone fits into a cup- shaped hole in the Your knee joint, like your other.Your shoulder elbow, is a hinge joint.The can move in a end of one bone fits into a complete circle. sort of hollow in the other. This kind of joint will only bend in one direction. 245

WHERE DO I COME FROM? You began your life as an egg, which was only about the size of this period. This tiny fertilized egg grew for about nine months inside your mother before you were born. While a baby is growing, it relies on the mother for everything, and although a baby cannot do very much when it is first born, already it is a complete and very special person. The beginning Everyone is made up of billions of living units, called cells. A baby starts when an egg cell from a woman and a sperm cell from a man join together to make one new cell. For the egg and sperm to meet, the man and woman must have sexual intercourse. This is sometimes called making love because the man and woman treat each other lovingly. The man’s penis gets firm and he puts it into the woman’s vagina. The penis releases a mixture called semen, which has sperm in it, to join the egg. Egg tube Bladder Penis Ovary Testes Egg make Uterus sperm Vagina After about eight weeks, the group of The fertilized egg It divides into cells starts to look The fingers, grows and divides four, eight, sixteen, more like a baby. toes, and face into two. and so on . . . are formed. Sperm are like tiny tadpoles with long tails.They swim to the While it is dividing, tube to find the egg. One sperm it is traveling to the may then fertilize the egg. womb, or uterus. After nine days the egg attaches itself to the wall of the uterus.

An ear to touch After 19 weeks the baby, or fetus, is properly formed, but it could not yet live outside the mother’s body. It is growing very fast and is moving around a lot inside the mother. The baby grows After forty weeks the baby is inside a warm, safe ready to be born.When a mother is bag which is full of watery liquid.There having her baby it is called labor because it is very hard work. is not much room so it curls up. The baby usually comes out head first.The Nutrients and oxygen muscles of the uterus travel from the mother help to push it out. to the baby through a mass of blood vessels, called the placenta. A special tube, called the umbilical cord, links the placenta to the baby’s tummy. 247