One Million Things_ 2nd edition-compressed

Herring gull eat northern div pipit
Gr
Meadow
ammer
er Emu

gbirdNightjar

C er thrush
Song
etti’s warbl

8

Chough

Kiwi

9
11

andpiper grouse
Chicken Red
Common s Yellowh
y owl
Rub y-throated hu10mmin

Tawn

Dunno ck

Newly hatched ostrich chick Brushland tinamou

7 CUCKOO 8 KIWI 9 COMMON SANDPIPER 10 HUMMINGBIRD

Cuckoos lay single eggs in the A kiwi is 20 times smaller than an Sandpipers are shorebirds that lay Hummingbirds lay the smallest of all
nests of other birds, and their emu, yet their eggs are almost the their eggs in shallow scrapes on birds’ eggs. The bee hummingbird’s
color varies to match the host same size. This means that the egg is the ground near the water. Their egg is the size of a pea, because
bird’s eggs. When the cuckoo huge compared to the kiwi that lays pointed shape allows them to be the bird itself is no bigger than
hatches, it heaves the other it, at up to a quarter of her weight. pushed together in a tight clutch a large moth. This ruby-throated
eggs out so it can eat all the That’s like a human mother giving to take up less space. The eggs are hummingbird’s egg is bigger but still
food its foster parents collect. birth to a three-year-old child. camouflaged by speckled patterns, tiny compared to the ostrich egg.
and can be hard to see—but if you
do find any birds’ eggs, remember it 11 CHICKEN
is illegal to collect or disturb them.
The egg that everybody recognizes

is laid by the domestic chicken.

We eat 1.1 trillion of these

eggs every year. 49

MOVEMENT 1

The feature that makes animals so different from other living things
is their ability to move. Some do not move much—a sea anemone,
for example, is sedentary (remains in one place) and catches
anything that touches its tentacles. Most animals, however, travel
to look for food, find breeding partners, or escape from their
enemies. They slither, crawl, walk, hop, run, swim, and fly,

sometimes at incredible speed. Some have evolved
other amazing ways of getting around, like the
insects and spiders that walk on water and the
extraordinary sidewinding rattlesnakes.

3
2

1 GIBBON

Although gibbons can walk well,
they usually move through the
forest by using their long, powerful
arms to swing from the trees. They
hurl themselves from branch to
branch with astonishing speed,
agility, and elegance.

2 SNAKE 8
7
A typical snake slips along by
curving its flexible body around
plants and stones and pushing the
curves toward its tail. Sidewinders
like this desert viper have a more
baffling method, looping sideways
over the sand like rolling springs.

3 OCTOPUS

An octopus normally hauls itself
over the seabed using its long,
elastic arms. But it can shoot away
from danger by jet propulsion,
drawing water into its body and
blasting it out at high pressure.
Cuttlefish and squid do the same.

4 PENGUIN 5 FISH 6 STARFISH 7 SNAIL

All penguins are superb swimmers, Most fish have flexible bodies that A starfish can curl its arms, but it The muscles in a snail’s foot
using their wings to “fly” through allow them to move through the actually creeps over the seabed contract and expand to create a
the water, but they walk clumsily. water using their fins for stability using hundreds of tiny “tube feet” rippling movement that pushes
On snowy slopes, they often prefer and to control their direction. on its underside. Each tube foot is the snail forward. Glands in the
to toboggan on their well-padded Some fish, such as tunas, propel pumped full of water and is foot produce a slimy mucus to
bellies, pushing themselves along themselves at high speed using extended and moved by changes make the track slippery. The slime
with their stoutly clawed feet. just their tails. in water pressure. also protects the snail from debris.

50

6

5
4

11
9 10

8 WATER STRIDER 9 CHEETAH 10 BARN OWL 11 KANGAROO

The water molecules at the surface The fastest of all land animals, a Birds are the masters of the air. A leaping kangaroo uses the elastic
of a pool cling together to form an cheetah can run at an astonishing Most, like this barn owl, use their tendons in the backs of its legs like
elastic film, strong enough to 60 mph (95 km/h). It achieves this powerful feathered wings to drive the springs of a pogo stick. Every
support tiny animals like this water by flexing its back to extend its themselves forward. Others can time it lands on its long feet, the
strider. Its special brush-tipped feet stride as it bounds forward on its travel long distances by soaring on tendons stretch like rubber bands
just dimple the surface, so it can long legs, but it can keep this pace rising air currents like gliders, then spring back again to catapult
skate around without sinking. up for only about 40 seconds. without beating their wings at all. the kangaroo forward.

51

LIVING
TOGETHER

Animals and plants often rely on other
living things for survival. Food, shelter, and
pollination are some of the clearest examples
of this. However, some animals and plants
have much closer relationships. They can
be partners, providing things like food or
protection for each other. Some tag along
with others without providing anything in
return. Many do worse, latching on to other
organisms as parasites, which can harm or
even kill their often helpless hosts.

The microscopic algae 1
that live in partnership
with this coral provide

its vivid color

2

huomffitmtfhlfieonTowhgsrwibetshirorleordisdnlao-gbn,piglteluerbbdfieullcltar 3 syeruxfcprhoAyamnhntogstnhepeerfyioordtreeesnwcwtemetheiete,saipnhids 4

This cuckoo chick has
outgrown both the host

bird and its nest, but it
still cries out for food

A strangler vine uses
a tree for support

but eventually kills it
by competing for
food and light

52 5

1 CORAL

Corals trap prey in their stinging
6 tentacles. They pass some of the

nutrients from their victims to tiny algae

living in their tissues. These use the sun’s

energy to make sugar, and they pass

some of this food back to the corals.

An impala 2 HUMMINGBIRD
welcomes
the attention Hummingbirds gather flower nectar,
of a red-billed and in the process they carry pollen
oxpecker from flower to flower. Some plants
searching for have evolved flowers that match the
tasty parasites bills of particular hummingbird species,
to encourage the birds to visit them
A remora clings to and deliver their pollen efficiently.
a shark’s skin using
a special sucker on 3 ANTS AND APHIDS
the back of its head
Aphids are tiny insects that feed on
sugary plant sap. They must eat a lot
of it to get enough protein, and they
excrete the excess sugar as drops of
sweet honeydew. Ants love to drink
this, so they “farm” the aphids,
protecting them from predators,
ensuring a constant supply.

4 CUCKOO

Cuckoos are “brood parasites”—they
lay their eggs in the nests of other
birds. Each young cuckoo hatches
quickly and destroys any other eggs
in the nest, so it can eat all the food
brought by its foster parents. It soon
outgrows its hosts, who often do not
seem to notice its massive size.

5 STRANGLER VINE

Some slender rain forest plants, such
as figs, grow by encircling a tree and
slowly killing it—a process that can
take up to 150 years. They steal the
tree’s nutrients, and eventually the
tree dies and decays, leaving the fig
plant standing alone.

6 OXPECKER

Hoofed grazing animals, such as
impalas, are often plagued by tiny
bloodsuckers, such as ticks, that
they cannot remove by scratching.
In Africa, stout-billed birds called
oxpeckers do the job for them by
picking the parasites off their skin
and eating them.

7 REMORA

Predatory sharks have very sharp
teeth that cut their prey to shreds.
The scraps are eagerly devoured by
fish called remoras, which travel with
the sharks by clinging to their skin.
7 They do their hosts no harm, and the
sharks seem to ignore them.

53

MAMMALS

Mofbaunnaarcirmmmkybimaoloklrsan.ulheSsnasoa)it.mrrielMyt,ewhua, elnanirkyylmieokeuhe-abtnualpglomlloaaoadrntnehetssdea,,rbewclavrehteetbairolttoeeuetborhaerttahspstetleoahrslnsia(dttapsfnfreoaeienmoydddoat.mlnhMseoweoiatrhisttbt.heaarrbeies

ECHIDNA ▶
The echidna and
the equally strange
mapmAlamtbyaapblusystheacarhetildtahnyeaeolginvgelsys.
on milk produced by
mother for up to six
its months. The mother

eats food such as ▲ MOUSE all mammal species are
eadrwitghiswthforohrmmerst,lohwnehggicrshonuoshnuedt.
Nearly half of rats,
rodents—a group that includes mice,
beavers, porcupines, and squirrels. The
house mouse is the only mammal, aside
from humans, to live on every continent.

◀ ELEPHANT

Elephants use their
sensitive trunks to
gather coarse
vegetation, which
they grind to pulp
with their massive
teeth. They are the
biggest land
animals and are
very intelligent.

KANGAROO ▶ ▲ BAT

Marsupials such as Bats are mammals that can fly. Some eat
kangaroos give fruit, but most species, like this long-eared

birth to tiny young bat, catch insects. They are nocturnal
that are only (active at night) and locate prey in the
dark by emitting high-pitched clicks and
half formed. The listening for echoes from their target.
newborn crawls
into a pouch on its
mother’s belly to

drink milk and
grow into a fully
developed baby
kangaroo, or joey.

54

◀ TIGER like the tiger eat other

Powerful hunters
mammals and birds. They have long,
daggerlike canine teeth for killing their
prey and scissorlike cheek teeth for
slicing through hide and meat.

▲ MOLE

Moles are specially adapted to their
underground environment. They have strong
claws for digging and very sensitive whiskers,
which compensate for their poor eyesight.

▲WksmtswiaulhKolirielamvfsIra.leLemcwTmLsehihEeanetanngoRyltdewscb,WodroilemtoifvhaHletepthuhhAitepneoiin-LrtaatsEhphn,ireoeld.ikw-odeceoetrwahfuninsl,

◀OttthhhuGeeartmgOclloioavRrmseieIlslLmsatiL—narAletsahlaapetrliearvaneaitsnpeaefamsotlroeiekrnsetgs

of tropical Africa.

HTmimhnhIaoaePrsssitvPhstiehiovOpreefspPlilyaotaOsnprbgtdouTiemtilAalsattemkMpmewulsaosUa.nulTsltSptohheewe▶anoitdnfesgr

any land mammal.

55

SLEEP Bats sleep while hanging
upside down by their
Animals sleep to save energy, rest their muscles, and allow feet in caves, tunnels,
their brains to process the information that they pick up while cellars, and from trees
awake. Some hunting animals sleep a lot, because they devote
only a few hours each day to looking for food. Animals that are 1
hunted spend much more of their time awake and alert.

3

1 Bats sleep for about 20 hours 11 Sheep are descended from wild Seals sleep for
a day, often in large colonies. animals that needed to stay awake around six hours
to escape predators, so they sleep every day
2 Two-toed sloths are awake for for less than four hours a day.
only four hours a day. Like bats, 6
they can cling to branches with 12 Kinkajous are raccoonlike
their claws while fast asleep. animals that forage for food at
night and sleep all day for about
3 Gorillas like to have about 12 hours.
12 hours of sleep a day.
13 Armadillos sleep for
4 Horses need just three hours 18 hours a day, curled
of sleep a day. up in their burrows. 7

5 Elephants stand up for two of 8
the four hours a day they sleep.
They have to lie down for the 11
dreaming stage, when their
muscles are too relaxed for them
to stay on their feet. Large plant-
eating animals tend to get less
sleep than smaller animals, because
they have to spend so much time
looking for food and eating.

6 Seals often sleep on rocks and 21
beaches, but they can also 14
sleep floating upright at
sea, or even under 23
water, surfacing to
breathe without 24
waking up.
16 Red foxes sleep for about 10
7 Wolves may sleep hours, mostly during the day. Like
for up to 14 hours a many hunters, they are more active
day, especially if they at night when they track their prey
have had a big meal using their sensitive noses and ears.
after a successful hunt.

8 Pigs need eight hours of sleep
a day, just like adult humans.

9 Bears also clock up about 22 15 Echidnas are egg-laying
eight hours of sleep a day. mammals that sleep for about
14 Human babies need 15 hours 14 hours a day. Scientists believe
10 Tigers sleep for up to 16 hours, of sleep a day. We sleep less as we they do not have phases of dream
since they can catch all the food get older, so adults sleep for an sleep like other mammals.
they need within a very short time. average of eight hours, and elderly
people for less than six hours.
56

2

4 5 22 Chinchillas sleep in burrows for
10 about 13 hours a day, high in the
Horses can sleep mountains of South America.
standing up without
toppling over because 23 Rabbits sleep for about eight
their legs lock in place hours, mainly during the day. They
prefer to feed at night when they
9 are not so vulnerable to predators.

24 Chimpanzees normally sleep
for 10 hours a day, but baby

chimps sleep for longer.

25 Baby gorillas need more
sleep than their parents and
may sleep or doze for more
than 15 hours.

26 Hedgehogs usually
sleep for 10 hours during
the day. In winter, they
hibernate (spend the

cold months in
a sleeplike,
inactive state).

Dogs have similar sleep
patterns to humans

12 13 17
15 16 20

19

25 18 26

17 Koalas eat tough eucalyptus 18 Dogs sleep for 10 hours a day. 20 Cats often sleep for 15 hours a 57
leaves that are hard to digest and day. Wild cats are most active
provide little energy, so they spend 19 Red pandas, which are like during the night.
about 15 hours a day sleeping and bamboo-eating raccoons, sleep for
another five hours dozing. about 11 hours a day. 21 Lions sleep for at least 13 hours.
While they sleep, other animals feed
near them without risking attack.

Gharial crocodile

Crocodile teeth are all Gannet
the same shape and can
be replaced by new ones
more than once

CROCODILE ▲ Merganser
ligthhBtewobneiyrigdjha’stwhbsoislrlunpy,port
One of the closest living relatives of
the dinosaurs, crocodiles have long jaws Hamster
studded with many sharp-pointed teeth
for seizing their prey. The fish-eating Badger
gharial of Indian rivers may have
more than 100 teeth.

Tawny owl anbdiBghrsoueagndesisetkiyvueelslehaorus ses Mallard
Blackbird Rabbit
Armadillo
Long bill of a Am Curlew
curlew allows azon parrot

it to probe prsotrtToehcnitngtcherneaonbuirugamihntisojustHedgehog
deeply into
soft mud to
catch worms

PARROT ▶ FROG ▶ Frog

All birds have thin, light skulls, which The skull of a frog is broad,
makes flying easier. Their beaks or
bills are much lighter than toothed providing plenty of room for
jaws. They are not built for chewing,
yet the bills of some parrots are its large eyes and giving it an
strong enough to crack nuts.

extremely wide mouth. This

allows it to swallow its prey

whole, so it does not need a

set of teeth for chewing.

Deep ridge on back ◀ LION Collie dog
of skull anchors
massive muscles Lion Like all cats, the lion is a dedicated
attached to jaw hunter. It has short, powerful jaws with
huge stabbing canine teeth at the front
58 and meat-slicing carnassials at the back.

The big eyes of this
powerful, fast-swimming
predator are contained
in large sockets

Anjtaewatsleoarnnsgdhntaeoovxnettgreleouemnethsgeblayut tall Anteater

▼ ANTELOPE BARRACUDA ▶ Barracuda Massive jaws are armed
with needle-sharp teeth
Some animals, such as antelope and Fish have quite strong for a secure grip on prey
cattle, have massive horns on their skulls, but the various
heads for defense and fighting parts are not fused
rivals. Male deer grow antlers, which together like those of
they use to impress females and mammals. The jaws of
fight each other, but these antlers many fish are separate
fall off at the end of the mating from the brain case but
season. Each male grows attached by bones that
a new pair every year. allow them to be thrust
forward to seize prey.
Strong bony cores ▼ BABOON
are sheathed with Furry skin
tough outer layers (velvet) Close relatives of humans, baboons have similar
of ridged horn skulls but longer jaws and bigger back teeth.
nourishes the This is because they eat large quantities of grass,
Antelope antler as it which requires a lot of chewing. They also have
long, sharp canines, which they use to kill animals
grows and is for food and to fight among themselves.
shed in
Baboon Eye sockets at front
the summer of skull allow the
baboon to see things
Deer in three dimensions

Long snout allows Nasal cavity contains thin
antelope to nibble scroll-like bones, which
grass while keeping support the membranes
watch for danger that detect scent

Sharp, bladelike incisor SKULLS
teeth on lower jaw are
ideal for cropping grass Most vertebrates (animals with backbones) have strong
bony skulls. They are made up of cranial bones that
and gathering leaves protect their brains, jaw bones that support their teeth
or beaks, and face bones that contain their eye sockets
and nasal cavities. The whole structure can be quite
heavy and is supported by strong neck muscles.

59

BLOOD CELLS

Magnified 13,500 times, this
is a false-color SEM (scanning
electron micrograph) of human
blood. Red blood cells (red)
carry oxygen, while white blood
cells (yellow) are involved in the
body’s immune system.

60

Human body

61

CELLS A macrophage
“reaches out” to
The body is constructed capture bacteria
from trillions of tiny living (blue), which it will
units, known as cells. There
are more than 200 different then digest
types of cells—and each has its
own shape, size, and specific job to 2
do. Typically, cells of the same type
work together in units called tissues.
Each individual cell is surrounded by
a thin membrane that regulates the
movement of nutrients and other
substances in and out of the cell. Cells
multiply by continually dividing into
two identical “offspring.” This
division allows the body to grow
and to replace cells that are
damaged or worn out.

1

62

Epithelial cells lock Spiky osteocyte lives in Bone matrix is made 1 NERVE CELLS
together to form the a lacuna, or space, in of hard calcium salts
protective, pitted lining the bone matrix and more flexible Found in the brain, spinal cord, and
of the stomach collagen fibers nerves, nerve cells, or neurons, carry
and process high-speed electrical signals,
3 called nerve impulses. These impulses
coordinate body processes and enable
5 us to feel, think, and move.

2 WHITE BLOOD CELLS

Circulating in blood, and in a clear
fluid known as lymph, white blood
cells help defend the body against
disease. The cells include macrophages
and neutrophils, which eat bacteria
and other germs, and also lymphocytes,
which release germ-disabling antibodies.

3 EPITHELIAL CELLS

Tightly packed together, these cells
provide a barrier to stop harmful
chemicals and germs from reaching body
4 tissues. They cover the body, forming the
outer layer of skin, and line hollow organs
such as the stomach, lungs, and bladder.

4 BONE CELLS

Osteocytes are bone cells that help
keep the bone in good condition.
At first, they lay down bone but
later become stranded within a
bony space. They keep in touch
through tiny threads and pick up
supplies from nearby blood vessels.

5 LIVER CELLS

Also known as hepatocytes, liver cells
enable the liver to perform many
hundreds of roles to control blood
composition and keep the body stable.
These include processing and storing
nutrients (foods) and removing poisons.

6 FAT CELLS

As their name suggests, fat cells

specialize in storing fat. They group

A spherical together to form adipose tissue,
fat cell is filled
6 mostly with which serves as an energy store,
a droplet of cushions organs such as the kidneys,

energy-rich fat and insulates the body under the skin.

63

64 1

SKELETON 1 SKULL

Constructed from 206 bones, the human The bones in the skull protect the
skeleton is a strong, flexible framework that brain, provide a framework for the
supports and shapes the body and produces face, and anchor the muscles that
movement when pulled by muscles. The
skeleton also protects soft, internal organs, such produce facial expressions. The skull
as the brain and lungs. Bones, which make up consists of 22 bones, 21 of which
20 percent of the body’s mass, are connected are locked together by immovable
to each other at joints and are held together
by strong straps of tissue called ligaments. joints called sutures. Only the lower
jaw (mandible) can move.
Shoulder joint
is the most Mandible moves to open
2 CHEST flexible joint the mouth for eating,
breathing, and speaking
The bones of the chest in the body
4 ELBOW
(thorax) consist of the sternum 2
The bones of the upper arm
(breastbone), the ribs, and part and forearm meet at the elbow.
This joint acts like a door hinge
of the backbone. Together, they allowing the arm to bend or
straighten. The forearm bones
form a protective “cage” that Humerus can rotate at the elbow,
enabling the palm of the hand
protects the lungs and the heart.
to face upward or downward.
3 FOREARM
4
The forearm is made up of two
parallel bones—the ulna and Hip joint is
the radius. The ulna curves where the
around the humerus to form ball-shaped
the elbow’s point, while the head of the
radius forms a joint with femur fits into
the carpals (wrist bones). the cup-shaped

Radius is the outer socket in the
bone of the forearm hip bone
Ulna is the inner
bone of the forearm

3

Sacrum
anchors the
backbone to
the pelvic girdle

Femur (thigh 5 6 7
bone) is the
6 PELVIS Phalanges are the
longest bone in 14 slender bones
the body This strong, bowl-shaped that form the
structure consists of the fingers and thumb
5 KNEE two curved hip bones
(pelvic girdle) and the 7 HAND
The knee joint between the femur sacrum. The pelvis supports
(thigh bone) and tibia (shin bone) the abdominal organs and Hinged at the wrist, the hand consists
is the strongest and most complex attaches the thigh bones to of 27 bones and many movable joints
joint in the body. This hinge joint the rest of the skeleton. (knuckles), which enable it to perform
allows the leg to bend or straighten a wide range of tasks. The human
and supports the body’s weight
during activities such as running, thumb is opposable, which means
jumping, or kicking. that it can be rotated to touch the
tips of each of the other fingers.
Tibia (shin bone) forms
joints with the femur Fibula is the
and ankle bones smaller bone of
the lower leg
8 FOOT
Tarsals are the seven
Each foot consists of the ankle, bones that form the
sole, and toe bones, which support ankle, heel, and part
and move the body’s weight. These of the arch of the foot
bones also provide a flexible
platform that pushes the body off Metatarsals are the
the ground during movement and five long bones that
absorbs the shock on landing. connect the toes to the
middle part of the foot
8 9 TOES

Phalanges are the The phalanges of the toes are
14 slender bones much shorter and less flexible
that form the toes than those of the fingers. The
phalanges enable the body to
stay upright and to stand on
tiptoe. They also help to
propel the body forward
during movement.

9

65

MUSCLES Deltoid muscle raises arm
sideways and swings it
Every body movement—whether backward and forward
it’s a leap in the air, a wink of the
eye, a rumbling stomach, or a
rapid heartbeat—is produced
by muscles. Skeletal muscles
are attached to bones of the
skeleton, which they pull to
move us around. Smooth
muscle moves food along the
intestine. Cardiac muscle keeps
the heart pumping. All muscles
are made of cells called fibers
that contract (get shorter) to
produce a pulling force.

1 SKELETAL MUSCLE Rectus abdominis muscle Diaphragm muscle
pulls in the abdominal separates the
Long, cylindrical muscle fibers run wall and bends the
in parallel and can reach up to 1 ft body forward thorax (chest) from
(30 cm) in length. They are bundled Sartorius muscle bends the abdomen and
together to form muscles that are the thigh at the hip aids breathing
attached to bones by strong cords and turns it inward Adductor longus
called tendons. Skeletal muscles muscle pulls and
move the body when instructed Quadriceps femoris is a turns the thigh
by the nervous system. group of four muscles inward
that straightens the
2 SMOOTH MUSCLE leg at the knee

Tightly packed into layered sheets,
smooth muscle fibers are found in
the walls of hollow organs, such as
the small intestine, along which they
push food, and the bladder, from
which they expel urine. Smooth
muscle contracts slowly and
cannot be controlled voluntarily.

3 CARDIAC MUSCLE Tibialis DEEP MUSCLES
anterior
Found solely in the wall of the heart, muscle lifts FRONT MUSCLES
cardiac muscle fibers form a branching the foot
network that contracts automatically, Skeletal muscles are arranged in overlapping
without stopping or tiring, to pump SURFACE MUSCLES layers, with surface muscles covering those
blood around the body. Stimulation deeper down. Muscles at the front of the
by the nervous system increases or body produce facial expressions, move the
decreases heart rate according to head forward and to the side, move the
the body’s demands. arms forward and bend them at the elbow,
bend the body forward and to the side,
66 bend the legs at the hip, straighten the
knees, and lift the feet upward.

1

2 Triceps brachii Intercostal
3 straightens the muscles move
arm at the elbow the ribs during
Gluteus maximus Latissimus dorsi pulls breathing
muscle straightens the arm backward and
thigh at the hip when toward the body
standing or climbing
Gluteus medius
muscle pulls thigh
out to the side

Biceps femoris Tibialis posterior
muscle (one of turns the
the “hamstrings”)
bends the leg at foot inward
the knee

Gastrocnemius muscle DEEP MUSCLES
pulls the Achilles
Peroneus longus
tendon to bend the muscle arches
foot downward foot when
on tiptoe
Achilles tendon is the
thickest and strongest REAR MUSCLES

tendon in the body All muscles are given Latin names that describe

their size, location, shape, action, or other

feature. Working downward from head to feet,

skeletal muscles at the rear of the body keep

the head upright, steady the shoulders, keep the

back upright to maintain posture, pull the arms

SURFACE MUSCLES backward and straighten them, straighten the

thighs at the hip and bend the knees,

and point the toes downward. 67

68 BODY SYSTEMS

The body’s trillions of cells are highly organized. Cells of the same The cerebellum is tucked ◀ BRAIN
type are grouped together in tissues. Two or more types of tissue under the cerebrum and
are used to build organs that perform specific roles. Organs form The brain is the center of
different systems that each carry out an essential job, such as coordinates balance the nervous system, which
digestion. There are 12 body systems that cooperate and interact and movement is responsible for controlling
with each other to form the human body. The organs of six body activities. It is dominated
body systems are shown here. The other six systems are the by the folded cerebrum that
integumental (skin), skeletal (bones), muscular, endocrine enables us to feel, think, and
(hormones), immune (defense), and reproductive systems. remember and instructs the
body to move. Other brain parts
Blood travels to and ◀ HEART are the cerebellum, tucked under
from the heart via the cerebrum, and the brain stem,
arteries and veins The cardiovascular which automatically controls
system moves blood breathing and heart rate and
LUNGS ▼ around the body to links the brain to the spinal cord.
deliver oxygen and
The respiratory system food to all the body’s ◀ SPINAL CORD
consists of the two lungs and cells and to remove
their wastes. Located An extension of the brain that
the air passages that carry between the lungs, runs down the back, the spinal
air from the outside. Each the heart is the center cord relays signals between brain
lung contains a network of of this system—a hollow, and body through the spinal
branching tubes that end in muscular pump that nerves connected to it. It also
millions of tiny air bags. It is contracts without tiring more controls many of the body’s
from these bags that oxygen than 70 times a minute to automatic reflex actions, such
force the blood around the as pulling the hand back if it
in the air passes into the body along blood vessels. touches something sharp.
bloodstream. It is carried to Together the brain, spinal
cord, and nerves form the
all body cells where it is nervous system.
used to release life-giving
◀ SPLEEN
energy from food.
The spleen is part
Air travels Breathing of the lymphatic
from the moves air system, the body’s
nose and in and out drainage network.
mouth of the lungs It contains white
along the blood cells, which
trachea to
the lungs fight infection
by destroying
bacteria, and also
removes worn-out
red blood cells
from the blood.

Liver stores ▲ LIVER ◀ STOMACH
excess glucose
and releases The largest internal organ, the This muscular bag
it when liver controls the composition expands as it receives
the body of the blood, processing and stores food that has
needs it nutrients newly absorbed been chewed and swallowed.
from the small intestine. During storage, the stomach’s
PANCREAS ▶ walls churn food into a
The gall part-digested “soup,”
The pancreas bladder
releases chemicals stores bile, which is released
called enzymes into a fluid that into the small
the small intestine aids fat intestine.
to aid digestion, and digestion
hormones (chemical The large
messengers) into the Each kidney contains a intestine turns
blood to control million tiny filtering waste into
levels of glucose— units that process feces (poop)
the body’s main blood to make urine and pushes
fuel—in the blood. them out of
the body

The small
intestine is a
long tube in
which most
digestion and
absorption occurs

Ureter has muscular Billions of
walls that squeeze harmless bacteria
urine downward digest waste in
to the bladder the large intestine

URINARY Bladder is a DIGESTIVE SYSTEM ▶
SYSTEM ▶ muscular bag that,
when filled, pushes The body needs nutrients for
Consisting of the urine out through energy, growth, and repair. The
kidneys, ureters, the urethra digestive system breaks down food
bladder, and to release these essential nutrients.
urethra, the urinary The system consists of the mouth
system makes urine and teeth, the esophagus (a
and removes it from the muscular tube leading from
body. The kidneys make the mouth to the stomach), the
urine by removing wastes stomach, and the small and large
and excess water and salts intestines. Food is digested using
from the blood, thereby keeping mechanical force, such as chewing,
its composition constant. Urine and through chemical digesters
is stored in the bladder called enzymes. Nutrients are
and expelled through then absorbed into the blood
the urethra at its base. and carried to the body’s cells.

69

70 RESPIRATION

The body’s trillions of cells require an uninterrupted Twelve pairs of ribs
supply of oxygen to release the energy they need to form the rib cage, which
stay alive. They get this by means of a process called protects the lungs and
respiration. Air containing oxygen is breathed into aids breathing
the body by the respiratory system. Oxygen enters Muscles between the
the bloodstream through the lungs and is carried to ribs move the rib cage,
body cells. Waste carbon dioxide is carried by the which helps to pull air
blood to the lungs and breathed out. into the lungs

The trachea carries air
to and from the lungs

1

RESPIRATORY SYSTEM

Located in the head, neck, and chest, the
respiratory system consists of the lungs,
which fill most of the chest, and the air
passages—nasal cavity, throat, larynx,
trachea, and bronchi—that carry air. This
X-ray shows the parts of the respiratory
system located in the chest.

The right bronchus
branches from the trachea

and divides repeatedly
inside the right lung

2

Branches of 3
the smallest
bronchioles

reach the
deepest parts

of the lung

4 The diaphragm is a domed
sheet of muscle that separates
chest from abdomen

1 TRACHEA 2 BRONCHIAL TREE 3 BRONCHIOLES AND ALVEOLI 4 DIAPHRAGM

Also called the windpipe, this flexible tube Once inside a lung, each bronchus divides The narrowest bronchioles end in 300 Situated just below the lungs, the diaphragm
carries air between the larynx (voice box) at into smaller bronchi that then spilt even million air-filled bags called alveoli that fill plays a key role in breathing. When breathing
the base of the throat and the two bronchi further. These, in turn, divide repeatedly to most of the lungs and are surrounded by in, the diaphragm contracts and flattens as
that arise at its lower end. Up to 20 C-shaped form smaller branches called bronchioles. blood capillaries. Oxygen passes through the muscles pull the ribs upward and outward.
rings of cartilage that encircle the trachea This arrangement is often called “the wall of each alveolus into the bloodstream This increases the space in the chest so that air
hold it open during breathing in. Mucus bronchial tree” because its structure looks in exchange for carbon dioxide, which is sucked into the lungs. When breathing out
lining the trachea cleans the incoming air by like an upside-down tree with the trachea moves in the opposite direction. The alveoli the relaxed diaphragm is pushed upward, and
as the trunk, bronchi as branches, and provide a large surface across which this the ribs move downward and inward,
trapping dirt and germs, a process that bronchioles as twigs. exchange can take place efficiently. squeezing air from the lungs.
began in the nasal cavity.
71

BLOOD Circulating around the bpBllloaosoomddaciseal5nls5d. p4e5rcpeenrtcent
average body are 9 1wbcO6olhnonmieotteadidlilbrnciooelsonpl2los5po,d0lf3ac7bmte5elloi,lll0seol,i0todas0n.ndred
Flowing all around your body, blood delivers pints (5 liters) of blood.
food, oxygen, and other essentials to trillions Oxygen-rich blood in
of cells and removes their wastes. Blood also arteries is bright red
distributes heat around your body and defends in color. Oxygen-poor
it against infection. Blood is made up of a yellow blood in veins is dark
liquid called plasma in which blood cells float. purple-red.
Red blood cells pick up oxygen in the lungs
and deliver it to your body’s cells. White blood
cells defend the body against disease-causing
germs. Blood also contains platelets, which
enable it to clot to seal damaged blood vessels.
The heart pumps blood around the body
along three types of blood vessels. Arteries
carry blood away from the heart, while
veins return blood to the heart.
Microscopic capillaries link arteries
and veins and supply blood to cells.

Plasma is 90 percent White blood cells Unraveled and Each as broad as a
water and contains called neutrophils stretched out, one thumb, the largest
more than 100 different and macrophages eat adult’s blood vessels artery and vein (the
dissolved substances, germs. Lymphocyte would encircle Earth aorta and vena cava)
including food, waste, white blood cells twice. Capillaries would are 2,500 times wider
hormones, and salts. disable germs by make up 98 percent of than a capillary, which
releasing chemicals the total length. is just one-tenth the
called antibodies. width of a hair.

72

Oxygen-carrying red During a lifes pan of Packed into every
blood cells make up 99 120 days, a red blood red blood cell are 250
percent of all blood cells. cell travels around the million red-colored
Every second, 2 million body 170,000 times— hemoglobin molecules.
new red blood cells are once each minute. It Each one carries four
made by jellylike red is then dismantled oxygen molecules, so
marrow inside bones. and recycled by the a single red blood cell
spleen and liver. can transport 1 billion
oxygen molecules.

The heart is made The heart beats, on Each person belongs
largely of cardiac average, 70 times a to one of four blood
muscle, which does minute. Heart rate groups—A, B, AB, or
not tire. can double or triple O. Blood groups are
Over a lifetime of 70 during exercise to determined by tiny
years, the heart beats get extra oxygen “markers” carried
2.5 billion times to your muscles. by red blood cells.
without taking a rest.

More than 112.5 million units of blood are donated around 73
the world every year. Blood transfusions replace blood lost
during surgery and are used to treat some medical conditions.

SKIN, HAIR, AND NAILS

Skin is the body’s protective overcoat, forming a The epidermis consists of Flat, scaly cells in the
barrier between vulnerable body tissues and the harsh, cells that migrate upward, upper epidermis are
changing conditions of the outside world. It prevents dying, flattening, and filling constantly worn away
water loss, blocks invasion by germs, repairs itself with keratin as they do so
when damaged, helps us keep warm, and enables as skin flakes
us to sense our surroundings. The uppermost layer
of the skin is made from dead cells filled with a 1
tough, waterproof substance called keratin. Hair
and nails, both derived from skin, are also made
from dead, keratin-filled cells.

1 SKIN CROSS-SECTION The dermis contains Cells in the base of the
living cells and fibers epidermis divide constantly
A section through the skin reveals that that allow skin to to replace those lost
it has two parts. The epidermis is a stretch and recoil from the surface
germproof, waterproof barrier that
protects against harmful rays in sunlight. 2
The thicker dermis contains blood vessels,
sensory receptors, and sweat glands. Surface of
the epidermis
2 SWEAT on the back of
a person’s hand

This salty liquid is produced by sweat

glands in the dermis. In hot conditions,

sweat is released onto the skin’s surface.

It then evaporates, cooling the body Melanin, along
and helping to maintain a constant with blood flowing

body temperature of 98°F (37°C). through the dermis,
gives the skin
its color

3 SKIN COLOR

Special cells in the epidermis 3
produce the brown pigment
melanin, which filters out Skin surface is not Sweat is a watery
harmful ultraviolet smooth but covered solution, filtered from
rays from sunlight with ridges into which blood and containing
before they sweat spreads salts and wastes, that
can damage oozes from small
skin cells. openings called pores

74

Fingernail is formed from
layers of dead, flattened
cells from the epidermis

4

Skin covering
the fingertips is
sensitive because
it contains many
touch receptors

Hair shaft is
made of dead
cells packed with
keratin, pushed up
from the hair bulb

5
6

Hair follicle is 5 HAIR
a hollow space
in the skin Millions of hairs grow from the skin
from which covering most body areas. Scalp hairs
a hair grows protect the skin from sunlight and
reduce heat loss. Finer, shorter body
4 FINGERNAIL hairs sense the presence of insects on
the skin before they can sting or bite us.
Ideal for gripping objects and
scratching itches, fingernails are clear 6 TOUCH RECEPTORS

plates that protect the sensitive The dermis contains a range of
upper parts of the fingertips. receptors that respond to soft touch,
The cells that make nails firmer pressure, and vibrations and
die, flatten, and fill send signals to the brain so we can
with keratin as feel our surroundings. The dermis
they are pushed also has receptors that detect pain,
forward from heat, and cold.
the nail’s root.
75
Sebaceous gland Hair bulb, deep
secretes oily sebum in the dermis,
that keeps hair and contains living,
skin flexible and soft dividing hair cells

76 BRAIN

Safely inside the skull, the brain allows us to sense, think, learn, remember, 1 PREFRONTAL CORTEX
and move. It also automatically regulates vital functions such as breathing.
The cerebrum, the main part of the brain, has two halves, or hemispheres. The most complex part of the cerebrum, the
The left hemisphere controls the right side of the body and is in charge of prefrontal cortex makes us what we are. It
language, math, and problem solving, while the right side controls the determines our personality and intellect and
body’s left side and deals with creativity, music, and art. The cerebrum’s enables us to reason, plan, create, and learn
many tasks are carried out by its outer layer, or cortex. This has distinct complex ideas and have a conscience.
areas that have different roles. Motor areas trigger movement, sensory
areas deal with the senses, while association areas interpret information. 2 BROCA’S AREA

Named after Paul Broca, the 19th-century
doctor who discovered it, Broca’s area is
normally found in the left hemisphere. It
plans what a person wants to say and sends
instructions to muscles in the throat, tongue,
and lips that produce speech.

3 6
5

4

1
2

11 10 8
7
12
9

3 PREMOTOR CORTEX 7 PRIMARY VISUAL CORTEX 10 WERNICKE’S AREA

Learned movement skills, such as playing When light hits the retina at the back of Usually located in the left hemisphere,
tennis, are controlled and coordinated by each eye, its light detectors send signals to Wernicke’s area gives meaning to words that
the premotor cortex. It tells specific muscles the primary visual cortex. Here those signals have been heard or read. Named after the
to contract either through the primary motor are interpreted as basic shapes, colors, and German doctor Karl Wernicke, it has a direct
cortex or, in some cases, directly. movements before being passed on to the link to Broca’s area enabling us to speak the
visual association cortex. words we hear or see.
4 PRIMARY MOTOR CORTEX
8 VISUAL ASSOCIATION CORTEX 11 PRIMARY AUDITORY CORTEX
Most movements we make are controlled
by the primary motor cortex. Guided by This is where information from the primary When sounds are detected by the two ears,
information from the cerebellum and other visual cortex about seen objects is interpreted they send signals to the primary auditory
brain parts, it sends instructions to muscles and compared with previous visual cortex. Here the loudness, pitch (whether high
that move the skeleton instructing them when, experiences. The visual association cortex or low), and rhythm of sounds are identified.
and in what sequence, to contract. identifies what we are looking at and where it That information is passed on to the auditory
is in space, enabling us to “see” it. association area.
5 PRIMARY SENSORY CORTEX
9 CEREBELLUM 12 AUDITORY ASSOCIATION AREA
Receptors in the skin for touch, pressure,
vibration, heat and cold, and pain send signals The cerebellum is responsible for producing Sounds are “heard” in the auditory association
to the primary sensory cortex enabling us to smooth, coordinated movements of the body. area. Using information received from the
feel those sensations. Our lips and fingertips It analyzes incoming information about the primary auditory cortex, it pieces together
have high concentrations of receptors, hence body’s current position and movement then the complete sound and, by comparing it
their sensitivity. interacts with the primary motor cortex to with sounds stored in memory, identifies it
precisely time muscle contractions. as, for example, music, speech, or thunder.
6 SENSORY ASSOCIATION CORTEX

Basic information about touch, pressure, and
other skin sensations is passed on by the primary
sensory cortex to the sensory association cortex.
Here sensations are analyzed, stored, and
compared with previous experiences. It enables
us to identify objects by touch.

77

SENSES 2

Our senses make us aware of the world around us Ear canal leads
and the changes that are happening in it. The eyes to the inner ear
detect light waves, and the ears sound waves, enabling where sounds
us to see and hear. The tongue and nose detect dissolved are detected
chemicals so we can taste, smell, and enjoy flavors. The
skin allows us to feel the texture and warmth of objects. Spiky papilla enables
the tongue to grip
Iris controls the food but does not
amount of light house taste buds
entering the eye

1

Ear flap captures
sound waves and
funnels them into

the ear canal

Ringing the bell
creates sound waves,

which are detected
by the ears

Shapes, color, Hand bell
and movement Smartphone
are all detected

by the sense
of vision

1 VISION 2 HEARING Sweets taste sweet
because they contain
Vision is the most important sense, providing the brain The ears detect waves of pressure, called sound waves, lots of sugar
with an immense amount of information about the body’s that travel through the air. Sound waves are produced
surroundings. Light reflected from, or produced by, outside by objects, such as a ringing cell phone or bell, which
objects is automatically focused onto a layer of light receptors move or vibrate. The waves pass into the inner ear,
that lines the back of the eye. In response, these receptors which is enclosed in bone on the side of the skull.
send signals to areas at the back of the brain. From there, Here, receptors convert pressure waves into signals.
we can determine what we are looking at and where it is, The signals travel to the brain, which identifies the
thus enabling us to “see” moving, 3-D images in color. pitch, volume, and direction of the sound.

78

Taste buds Feathers feel 5
housed in soft and ticklish
mushroom-
shaped
papilla

4

3 Skin ridges in the
fingertips help us
3 TASTE grip the objects
we touch
Small projections on the A cactus spine
tongue, called papillae, puncturing the
house taste receptors skin stimulates
called taste buds. Food a pain receptor
molecules dissolved in
Csaliva are detected by Some
the taste buds. These can cheeses
distinguish between five
basic tastes—sour, sweet, emit a
salty, bitter, and umami strong
(savory and meaty). In
addition to helping us smell
to enjoy food, our sense
of taste enables us to
detect foods that may
be poisonous.

itrus fruits

Fresh flowers

Lemons and most other 4 TOUCH 5 SMELL
citrus fruits taste sour
The skin acts like a sense organ. It contains several The nose can detect more than 10,000 different smells.
different types of receptors that enable us to When air is breathed into the nose, odor molecules dissolve
“feel” our surroundings. Most are touch receptors in watery mucus and are detected by odor receptors high
that send signals to the brain when the skin comes in the roof of the nasal cavity. Together, the senses of smell
into contact with objects. Some detect light touch, and taste enable us to detect flavors. Smell is more important,
some heavier pressure, and some vibrations. however, which explains why food lacks flavor when we
Other receptors in the skin pick up temperature have a blocked nose. Some smells, such as those produced
changes or detect pain. by burning, can warn us of danger.

79

REPRODUCTION

Human beings have a limited life span but are able, Female egg
through reproduction, to produce a new generation is large and
to succeed them. Male and female reproductive systems spherical. It
produce specialized sex cells—called sperm and eggs—that cannot move of
unite during fertilization and combine their genetic instructions its own accord
to make a new, unique human. After fertilization, the embryo— Male sperm
later called a fetus—grows and develops inside its mother’s uterus with beating tail
(womb) for the nine months of pregnancy. penetrates the outer
layer of the egg
FERTILIZATION ▲

Inside a woman’s reproductive system,
sperm swim toward and surround an egg

and attempt to penetrate its outer layer.
Eventually one succeeds, loses its tail, and its

head fuses with the egg’s nucleus, thereby
combining two sets of genetic instructions (DNA).

◀ CELLS MULTIPLY

As the fertilized egg, or pre-embryo, is swept toward
the uterus, it divides repeatedly, producing first two
cells, then four, then eight, and so on. Six days after
fertilization, it embeds itself in the uterus lining.

72 hours after fertilization, The head becomes The liver makes the
the pre-embryo is a more erect and the ears, embryo’s blood cells
ball of 16 cells including the organs of until bone marrow
balance, develop can take over

Dark retina of a
developing eye on the
side of the embryo’s head

▲ FOUR WEEKS ▲ FIVE TO SIX WEEKS ▲ SEVEN WEEKS

This pea-sized, four-week-old The embryo’s brain continues to develop, as do other The bones of the grape-sized
embryo—its head is on the organs, such as the intestines. Its skull and face are taking embryo start to harden, and muscles
left—is growing in its mother’s shape, and limbs, in the form of buds, are starting to grow. develop and get stronger. Wrists
uterus. Its tiny heart is beating, The embryo floats within a sac filled with protective fluid. and ankles are now visible, and fingers
and the nervous system and and toes are just starting to appear.
vital organs are forming. Internally, the kidneys start to
remove waste to make urine.
80

Placenta

▲ TEN WEEKS Eyes have ▲ TWENTY WEEKS
moved from
Now 500 times bigger than the side of Fingers and ears clearly visible, the
a fertilized egg and consisting the head, movements of the fetus can be felt
of billions of cells of different and eyelids by its mother inside her expanding
types, the fetus, as it is now are forming uterus. The fetus blinks and swallows
and follows phases of sleeping and
called, has all its basic organs ▲ TWELVE WEEKS The fetus receives waking. The ridges that produce
in place and is growing rapidly. food and oxygen fingerprints appear on its fingertips.
through the umbilical
Its large head accommodates Since their implantation, the cells cord, which is
connected to the
a fast-expanding brain. Fingers have been growing and specializing, mother via an organ
called the placenta
have formed, and fingernails and the tiny individual they have

are growing. molded is now recognizably human.

It has facial features, and fingers

and toes have separated. The

internal organs are in place,

and the heart is beating.

▲ THIRTY WEEKS NEWBORN

Ultrasound scanning, shown here, As pregnancy comes to an end, the uterus
is a safe method used to monitor the contracts to push the fully grown fetus into the
development of a fetus and can also bright, noisy outside world. The newborn baby
reveal whether it is a girl or boy. At takes its first breath and the umbilical cord is cut.
this stage, the brain is still growing In the next phases of its growth and development,
rapidly. The fetus can hear sounds, the baby is completely dependent on its parents
and its eyes respond to light. Its lungs for food, warmth, and protection.
can now potentially breathe air.

81

GENETICS 1

Though all humans share the same basic body plan,
each of us (aside from identical twins) has a unique
mixture of features. That is because the set
of instructions—called genes—required to
construct a human varies slightly from
person to person. Genetics is the study
of how the genes we inherit from our
parents shape the way we are.

Eye color is controlled by
specific genes, and different
versions of those genes
produce a range
of colors

2

82

3

4

2 CHROMOSOMES

A cell’s DNA molecules are packaged into 23 pairs of
chromosomes, which are found in the nucleus, the

cell’s control center. Normally, they are long and thin,
but when a cell prepares to divide into two new cells,
each chromosome shortens—as its DNA coils up—and

duplicates, taking on the X shape shown here.

3 INHERITANCE

We inherit half of our chromosomes from each of

our parents. A set of 23 chromosomes contains about

25,000 genes. Maternal and paternal chromosomes

carry matching pairs of each gene—such as the gene

that controls eye color—but not necessarily the same

version. If two versions are present, only one—

1 DNA the dominant gene—has an effect.

Long molecules of DNA (deoxyribonucleic acid) are 4 GENETIC SIMILARITY

found in every body cell. When magnified, DNA As brothers and sisters inherit a selection of genes

resembles a twisted ladder with “rungs” made from from the same two people, their parents, they

four types of chemicals called bases (shown in color). are more likely to resemble each other than

The sequence of bases along a section of DNA forms they would a nonrelative. Identical twins

an instruction—a gene—for making one of the share almost identical genes, so they look

proteins that build and run a cell. the same and are of the same sex.

83

84 NUTRITION

Eating a balanced diet is an important part of good health. ◀ SUGARS
The food we eat supplies the nutrients required to build
and repair the body and to provide it with energy. Most of Foods such as sweets, cakes, and cookies
our nutrition consists of three food types—carbohydrates, should be eaten sparingly because they
proteins, and fats—but vitamins and minerals are also contain lots of added sugar. Eating large
needed in tiny amounts. Water and dietary fiber are other
key components. To remain healthy, a person should eat amounts of sugar gives the body
a variety of food in the correct proportion. Carbohydrates, sudden bursts of energy rather than
the body’s main source of energy, come in two forms— the constant stream it obtains from
complex carbohydrates and sweet-tasting sugars.
complex carbohydrates. Sugar that is
FATS AND OILS ▶ excess to requirements is stored as fat,
causing a person to put on weight.
Although fats and oils supply vitamins and
are essential to the functioning of the body, Good-quality chocolate
supplies some useful
they should be consumed in moderation. nutrients but can also
Plant oils, such as olive oil, contain be high in fat and sugar

unsaturated fatty acids (as do oily fish), Walnuts are rich in
which are good for health. However, omega-3 fatty acids,
saturated fatty acids, contained in which are essential
many animal foods and added to
processed foods, can clog arteries. for good health

Olive oil, like all
unsaturated fats,
is liquid at room
temperature

PROTEINS AND DAIRY FOODS ▶

About 15 percent of our diet should include
proteins needed for growth and repair.

Foods rich in proteins include nuts, beans,
eggs, fish, and meat. Red meat is also

rich in saturated fat, harmful to health
if eaten in excess. Dairy foods, such as

milk and cheese, supply the bone-
building mineral calcium and some
protein but can also be high in fats.

FRUIT AND VEGETABLES ▶ Orange, red,
and green,
Fruit is a good source of water, peppers are
fiber, and vitamins and the natural
all excellent
sugars that give us a burst of sources of
energy. Many also supply vitamins

antioxidants, which can reduce A and C
the risk of some diseases.

Vegetables contain vitamins
and minerals and are a good
source of fiber. Nutritionists
recommend that we eat at
least five portions of fruit

and vegetables daily.

Brown rice is
rich in some
B vitamins

Whole-grain bread
supplies some iron,
protein, and fiber

Potatoes are a good
source of both
vitamins C and B6, as
well as some minerals

Bran cereals are rich ▲ COMPLEX CARBOHYDRATES
in fiber, which helps
make digestion Starch is the main complex carbohydrate in our diet.
more efficient Foods rich in starch include pasta, cereals, potatoes,
bread, and rice. During digestion, starch is broken
Pasta is made from down to the sugar glucose, the body’s main source
wheat flour and is of energy. Complex carbohydrates should make
a good source of up about half of our diet.
slow-release energy

85

HEALTH DRUGS Co Blaurbeeesaupcdasoheutdesiesfbivttyhehceebayyatefanarrdelelariegsnaefssoyotodugh syrup

A healthy body is one that is fit, strong, Chemicals that are used to treat and
supple, and working well. Disease and injury prevent disease, by changing some
prevent the normal working of the body. While aspect of the way the body works, are
it is not always possible to avoid illness, the called drugs. Antibiotics, which kill harmful
chances of developing a disease are reduced by bacteria, and analgesics, which reduce pain,
adopting a healthy lifestyle, including getting are both examples of drugs. They may be
regular exercise and eating a good, mixed diet of given to a patient in a number of ways—
fresh foods. If a person does become ill, a doctor
has to figure out exactly what the problem is and by injection, as pills and syrups that are
then decide on a suitable course of treatment. swallowed, or as a vapor that is
This might include drugs, surgery, or other inhaled into the lungs.
means to return the person to full health.
Inhaler is used to Hypodermic syringe is
Laryngeal mirror is introduce drugs, used to inject drugs
placed in the mouth such as those that
to check the larynx treat asthma, into into the bloodstream,
(voice box) the lungs skin, or a muscle

Otoscope has a Pills
lens and a light
Thermometer and is used to
look into a
patient’s ear Stethoscope is FIRST AID
used to listen to
Ophthalmoscope chest sounds The initial treatment to a
enables a doctor to such as breathing person who is sick or injured
examine the inside and heartbeat is called first aid. It is often
carried out by someone who
of a patient’s eye is not medically qualified but
has been trained to use simple
DIAGNOSIS yet effective treatments. In
more serious cases, first aid
If a person is ill, his doctor first needs to may keep a person alive until
determine exactly what is wrong with him. medical help arrives. A first-aid
This is called making a diagnosis. The doctor kit contains essential items such
asks about symptoms—the features of the as disposable gloves, scissors,
disease or injury the patient has noticed—and antiseptic cream and wipes,
considers the patient’s medical history. Next, the
doctor looks for signs to help identify the illness, adhesive bandages,
for example, using a thermometer to check sterile dressings,
body temperature. The patient may require and bandages.
further tests, such as blood tests or X-rays.

86

Running shoes are Dumbbell weight
ideal footwear for Chicken is a meat that
running and other
exercises that is rich in protein but
improve fitness low in harmful fats

PREVENTION Oranges, like all
fruits, contain
Regular exercise, such as running, walking, or playing vitamins that
sports, improves fitness by making the heart and body
muscles more efficient. It is also important to eat a are essential for
balanced diet made up of a wide range of foods— good health
Fish, especially oily fish,
including pasta and rice, fruits and vegetables, lean contain fatty acids that can
meat, and oily fish—and low in salt, sugar, and reduce the risk of heart disease
in the unhealthy fats found in red meat. Not
only does a healthy diet reduce the risk of
becoming overweight, but it can also help
protect against certain diseases.

Elasticated bandages SURGERY
support joints, limit
swelling, and secure Performed by a doctor called a surgeon, surgery
dressings that involves cutting into a patient’s body to repair,
control bleeding remove, or replace tissue damaged by disease or injury.
Surgery takes place in an operating room. To reduce
the risk of infection, staff wear gowns and masks, and Stienr“silttersouusoomrulgpsre”eegnoriucatnassteiltaodornebpstyehraeform
everything is sterile (free of germs). During an
operation, the patient is given an anesthetic—a drug
or gas that stops them from feeling any pain.

Antiseptic cream Sterile dressing Coarse forceps Scalpel is a sharp
Disposable gloves Fine scissorsblade for cutting
through skin and
Coarse scissorsother tissues
ProbesFine forceps are
used to grip and
lift tissues during
an operation

87

MOTHERBOARD

This computer motherboard
is a maze of microchips and other
components linked by copper
wires. It connects all the computer’s
components, passing on instructions
and data with incredible speed.

88

Science and technology

89

The Orion Nebula, a ELEMENTS
vast cloud of gas and dust,
is made mainly of hydrogen Everything in the world is made from
elements—pure substances that cannot
1 be broken down into anything simpler.
Elements can be grouped according to
Magnesium is a silvery the properties they have in common, such
substance that burns with as their appearance, how they conduct
a dazzling white flame electricity, and how they react with other
substances. There are nine main groups
2 and the element hydrogen, which is unique.

Copper is a good
conductor of heat
and electricity

4

Potassium is an Radioactive sign
alkali metal found is used to show
in minerals in elements that
Earth’s crust emit radiation

3 5

1 HYDROGEN 2 ALKALINE-EARTH 3 ALKALI METALS 4 TRANSITION 5 ACTINIDES
METALS METALS
Hydrogen makes up 90 Sodium, contained in salt, The elements in this group
percent of all the matter in Alkaline-earth metals react is an alkali metal. These This group is the largest are radioactive metals
the universe. Pure hydrogen with water and are found elements are characterized and includes iron, silver, mostly created synthetically
is an invisible gas on Earth. in minerals in Earth’s by their vigorous reaction gold, nickel, platinum, and in nuclear reactors or
It is not considered part of crust. In pure form, they with water. On contact, they titanium. Transition metals nuclear explosions. They
any one group. Hydrogen are silvery-white. They are will zoom all over the water’s are considered typical have unstable atoms that
powers the nuclear reactions similar to alkali metals but surface or even explode. Alkali metals—they are hard and break up and give out
inside stars, including our less reactive. Calcium, found metals are not found in a pure shiny, conduct electricity radiation particles. Uranium
sun, and is found on Earth in in chalk, milk, and bones, form in nature because they and heat well, and have and plutonium are examples
the compound H2O, or water. is a member of this group. react so strongly with water. high melting points. of actinides.

90

6 8

Gadolinium, After hydrogen,
like the other helium is the
lanthanides, lightest element
reacts easily and is used to
with air fill balloons
and airships
because it is
lighter than air

The halogen Tin is often made
bromine is a into alloys—mixing
red-brown it with copper makes
liquid at room bronze, while
temperature combining it with
but evaporates lead forms pewter
quickly to form
a choking, 9
poisonous gas
10
7
Silicon is often
used to make
microchips for
electronic devices

6 LANTHANIDES 7 NONMETALS 8 NOBLE GASES 9 POOR METALS 10 SEMIMETALS

These soft, reactive metals Around one-sixth of elements There are seven noble gases— Metals that are fairly soft These elements have some
were known as rare earths, are nonmetals. They are poor also called rare or inert gases and melt easily are known as properties of metals and
because they were wrongly conductors of electricity and because they do not readily poor metals. They are readily some of nonmetals. Arsenic,
believed to occur only melt at low temperatures. react with anything or found as ores (minerals) in for example, is shiny like
scarcely in nature. Silvery- Carbon, nitrogen, and oxygen combine with other elements Earth and can be very useful, a metal but not a good
white in appearance, they are all examples of nonmetals, to make compounds. They are especially when made into conductor. Some semimetals
tarnish easily on contact with as are the halogens, a group of helium, neon, argon, krypton, alloys (two metals mixed are semiconductors, behaving
air. Holmium, the element highly reactive elements that xenon, radon, and oganesson, together to make a harder as conductors or insulators
with the greatest magnetic combine with other elements although the latter may be a metal). Aluminum and lead depending on what other
strength, is in this group. to form salts. solid at room temperature. are both poor metals. substances are added to them.

91

MOLECULES Oxygen atom

An element is a substance made of only one kind of atom. ◀ OXYGEN (O2)
Atoms join, or bond, to other atoms of the same element
or to atoms of other elements. They do this by sharing or Some elements can bond in
exchanging electrons. In many cases, the bonded atoms
form groups called molecules. When atoms of one several ways to form different
element combine with atoms of other elements, substances. Atoms of the element
they form compounds. oxygen (O) bond together in pairs

to form molecules of oxygen gas.

Hydrogen atom High in the atmosphere, however,
oxygen atoms also bond in threes
Oxygen atom to form the gas ozone.

VITAMIN C (C6H8O6) ▶ Hydrogen atom Carbon atom

Like ethanol, vitamin C (ascorbic

acid) contains carbon (C), hydrogen (H),

Carbon and oxygen (O) atoms. However,
atom
because the molecule contains different
quantities of the elements arranged
in a different way, it forms an entirely

different substance—a compound

that is solid at room temperature.

ETHANOL (C2H5OH) ▲ Hydrogen Oxygen atom
atom
Ethanol is a compound with molecules Carbon atom ◀ METHANE (CH4)
containing two carbon (C) atoms, six
hydrogen (H) atoms, and one oxygen Molecules of the gas methane contain
(O) atom. At room temperature, it is a four hydrogen (H) atoms bonded to
colorless liquid used as a disinfectant, a carbon (C) atom. Compounds of
preservative, and the alcohol in drinks. carbon and hydrogen are called
hydrocarbons. They include fuels,
such as methane, oil, and coal, and
artificial materials, such as polystyrene.

Sodium and chlorine Chlorine atom
atoms always join up
in the same way to
form cubic crystals

Sodium atom

◀ SALT (NaCl)

Table salt, or sodium
chloride, is made of equal
numbers of sodium (Na)
and chlorine (Cl) atoms.
Salt does not form as small
individual molecules
containing one atom each
of sodium and chlorine.
Instead, many atoms of the
two elements link to form a
rigid lattice called a crystal.

92

Oxygen atom ◀ WATER (H2O) SULFUR (S8)

When two atoms of the gas Eight atoms of sulfur (S)
hydrogen (H) bond with one atom bond together in a ring
of the gas oxygen (O), they form to form a sulfur molecule.
molecules of liquid water. Water is Most nonmetal elements
the most common compound on are gases at room
Earth and is essential for life. temperature, but sulfur
is a brittle, yellow solid.
Hydrogen atom
◀ DIAMOND (C)
Sulfur atom
A diamond can be thought of as a
Nitrogen atom single giant molecule. It is formed from
atoms of carbon (C) bonded in a strong
Hydrogen atom ▲ AMMONIA (NH3) crystal lattice. However, if carbon atoms
join in flat sheets of hexagonal tiles,
The colorless gas ammonia is they form graphite, a brittle substance
made up of one nitrogen (N) used to make pencil leads.
atom bonded to three hydrogen
(H) atoms. Plants get the
nitrogen they need to grow from
ammonia and other nitrogen
compounds within the soil.

Carbon atom

Sticks are used to Except at the edges,
show the bonds each atom is linked
between atoms firmly to four others

Balls represent
atoms in models
of molecules

93

ACIDS AND BASES ◀ CITRIC ACID

An acid is a substance that produces positively charged The sharp taste in citrus fruit such as
particles of hydrogen, called hydrogen ions, when lemons and grapefruit is due to the
dissolved in water. The more hydrogen ions an acid citric acid they contain. Citric acid is
contains, the stronger the acid is. A base is the chemical often artificially added to manufactured
opposite of an acid. Bases produce negatively charged foods and drinks to give a tangy
particles in water, called hydroxide ions. The sensation that tastes refreshing.
more hydroxide ions a base contains, the
stronger it is. Bases that dissolve in water Vinegar is made when
are called alkalis. bacteria convert the ethanol
in alcohol into acetic acid
INDICATOR PAPER ▼
◀ VINEGAR
When a strip of indicator paper
is dipped into a liquid, the paper The sour taste of vinegar
changes color. The color can be comes from the acetic acid it
compared to a pH scale to find contains. Every step on the
out the acidity of the solution. pH pH scale is 10 times less
stands for “potential of hydrogen” acidic than the previous
and measures how many hydrogen step, so acetic acid with a pH
ions the solution contains. of 4 is 1,000 times less acidic
than hydrochloric acid.

◀ HYDROCHLORIC ACID

The lower the pH value, the
stronger the acid. Hydrochloric
acid, created when hydrogen
chloride gas dissolves in water,
has a pH of about 1. It is highly
corrosive, capable of eating
through metals.

◀ STINGER ◀ CHEMICAL HAZARD

When a bee stings, Strong acids and bases have
it injects a mild acid to be stored in containers
into a person’s flesh, that will not be corroded
which causes a stinging by the chemical within. These
sensation. Washing the
sting with alkaline soap containers are labeled with
may relieve the pain by chemical hazard symbols that
neutralizing the acid. show the potential dangers.

94

All bases tend to feel LIMESTONE ▶
slippery like soap
Calcium carbonate, or
LIQUID SOAP ▶ limestone, is a type of rock
formed from the remains of
Soap is a weak base. It is dead sea creatures over millions
made by combining a of years. It is an important base,
which is quarried and crushed
weak acid with a strong
base, making it only to make fertilizers, paints,
ceramics, and cement.
mildly alkaline with a pH
of about 8. An indicator
paper dipped into liquid
soap turns blue.

CLEANING FLUID ▶

The strongest bases have a pH of

◀ WATER 14 or more. Alkaline solutions with
a high pH are used as cleaning

Pure water is neither acid nor materials as they dissolve fats.

alkali, but neutral, with a pH of 7. Cleaning fluids such as bleach and

Rainwater is slightly acidic, with a pH caustic soda have a pH of around 10.

of 5 to 6, while seawater is slightly

alkaline, with a pH of between 8 and 9.

The pH of tap water is usually
between 6 and 8 depending on
the gases and minerals that
are dissolved in it

HYDRANGEAS ▶

The hydrangea shrub
produces different colored

flowers depending on
the acidity of the soil. On
acid soils, it produces blue
flowers, on alkaline soils, it

produces pink or purple
flowers, and on neutral soils,

it has creamy white blooms.

95

Chalk and vinegar fizz CHEMICAL
vigorously as the acid REACTIONS
breaks down the chalk
The atoms within a molecule are held together with
1 links called chemical bonds. In a chemical reaction,
2 the bonds between a molecule’s atoms break, and
the atoms bond in a different way to form new
molecules. In some reactions, elements combine to 3
create a compound. In others, compounds break
down into elements or simpler compounds. All

the atoms from the original substance exist in the
changed substance but in different places.

Silver metal clings Burning is a nonreversible
6 to the copper coil reaction—the wick cannot be
remade from the ash and smoke

The energy produced The explosion caused by When chemicals in an
when sulfur and iron react igniting thermite produces apple’s cells that contain
causes the mixture to glow a temperature of around substances called phenols
4,350°F (2,400°C) are exposed to the
air, they oxidize and
turn brown

8

7

1 REACTION 2 DISPLACEMENT 3 BURNING 4 REACTION RATES 5 REVERSIBLE

When vinegar (acetic acid) In a displacement reaction, When the wick of a candle The rate of a chemical A few reactions are reversible.
and chalk (calcium carbonate) the metal that forms part of burns, it is reacting with reaction is affected by The molecules created by the
are mixed, a chemical reaction a compound is removed and oxygen in the air to produce factors such as temperature, reaction can be reformed into
takes place. The acidic vinegar replaced by another metal. ash and smoke. The burning pressure, light, surface area, the original materials. The
breaks down the chalk to When a coil of copper is also produces energy in and concentration. It is initial reaction is called
release carbon and oxygen dipped into a clear solution the form of heat and light. possible to change the rate the forward reaction, and
as bubbles of carbon dioxide. of silver nitrate, the copper In all reactions, energy is of a reaction by varying one the reverse is the backward
The starting materials in a displaces the silver from the used up when bonds of these factors. For example, reaction. Dinitrogen tetraoxide
chemical reaction are called solution to form a blue between atoms break, and increasing the concentration breaks down into nitrogen
reactants. The materials that solution of copper nitrate and energy is released as new of dye in a solution will dye dioxide when heated but
exist after are called products. needles of solid metal silver. bonds are made. the material more quickly. reverts when cooled.

96

Concentrated dye At temperatures above At lower temperatures,
contains more dye 284°F (140°C), nitrogen the nitrogen dioxide
particles to collide dioxide exists as a molecules pair up to
with the cloth brown gas make clear dinitrogen
tetraoxide

If heated again,
brown nitrogen
dioxide reforms

5

4

As crystals of potassium When a bread dough
permanganate begin to mixture is left in a
dissolve, purple trails warm place, carbon
spread through the water, dioxide bubbles appear,
until an even purple making the bread rise
solution is formed
9
10

6 APPLYING HEAT 7 EXOTHERMIC 8 OXIDATION 9 SOLUTIONS 10 CATALYST

When a mixture of yellow Thermite is a mixture of Some chemical reactions A solution is a mixture in A catalyst is a molecule that
powder sulfur and silver- aluminum and iron oxide. happen around us naturally. which the molecules are helps bring about and speed
gray iron filings is heated When it is ignited at a high One of the most common mixed so evenly and up a chemical reaction but
to a high temperature, a temperature, there is an reactions is oxidation—when completely that it seems like a does not change itself during
chemical reaction takes explosion, as the chemical substances gain oxygen. single substance. However, in the reaction. Natural catalysts
place, and iron sulfide is reaction produces a sudden Oxidation is happening when a solution, a chemical reaction are called enzymes. Bread
formed. Without heat, the release of energy in the metals rust, when wood has not taken place. Neither dough rises because enzymes
substances would not react form of light, heat, and burns, and when we breathe. the solute (the substance in yeast cause a reaction that
with each other. Heat speeds noise. Reactions that In all these reactions, being dissolved) nor the produces bubbles of carbon
up most reactions, and cold produce heat are known substances are reacting solvent (the substance that it dioxide when it is mixed with
slows reactions down. as exothermic reactions. with oxygen from the air. is dissolved in) have changed. water and sugars.

97

98 STATES OF MATTER

Everything you can smell, touch, or taste is made from
matter, including living things such as yourself and
nonliving things such as this book. Matter is made up
of atoms, and anything that is not made of matter is
energy. Heat, light, and sound are forms of energy.
You cannot smell, touch, or taste energy, and it is
not made from atoms. All matter on Earth exists
in one of three states: solid, liquid, or gas.

1

1 SOLID Unlike most substances, 4 STATE TO STATE
water expands when it
A solid, such as this ice sculpture, freezes (instead of Matter changes from one state to
has a fixed volume and a shape that contracting) because its another when it is heated or cooled.
is not easy to change. Strong links molecules move farther Heating melts solids into liquids and
hold atoms together and do not apart when locked into the boils liquids to form gases. Cooling
allow them to move around, as they rigid structure of a solid condenses gases to form liquids and
can in a liquid and in a gas. The freezes liquids into solids. As matter
atoms in most solids are arranged changes from one state to another, 2
in regular patterns that form the atoms within it remain the same
three-dimensional shapes, such as but become arranged differently.
cubes and prisms, called crystals.
5 CHANGING SHAPE
2 GAS
Solids do not always have a fixed shape.
A gas does not have a fixed Some solids, such as ice or glass, are
shape or a fixed volume. It brittle and will break if you hammer or
expands to fill all the space crush them. Other solids, such as rubber
around it. Atoms in a gas can or metals, are malleable and can be
move freely in every direction. hammered, stretched, or squashed into
They whizz around far too fast different shapes without breaking.
to ever stick together.

Most gases are invisible.
Even steam cannot be
seen until it condenses

5 into a mist of droplets as
it mixes with cooler air

4