Celestial bodies like the Earth, have two types of movement: The planets in the Solar System Orbit6. The Earth isthe only planet with: • an atmosphere containing oxygen • an average temp
Trang 2About this book 3
Learning to learn Getting closer to the stars! 6
1 The Universe 8
2 Planet Earth 18
Learning to learn All creatures great and small 28
3 Living things 30
4 Invertebrates 42
5 Vertebrates 52
6 The plant and fungi kingdoms 62
7 The simplest living things 74
Learning to learn Rock stars and instruments 84
8 The Earth’s atmosphere 86
9 The hydrosphere 96
10 Minerals 106
11 Rocks 116
Learning to learn It’s elementary! 128
12 Matter and its properties 130
13 Everything is matter 140
14 Atoms and elements 150
Vocabulary 160
Key language
PAGE
Trang 3Learning to learn
ABOUT THIS BOOK
• Look at these illustrations
Match them to the units
on the opposite page
Then look at the book,
and check your answers
Unit
L
Unit
Trang 4YOU ALREADY KNOW A LOT!
Work with a partner Try to answer these questions
THE UNIVERSE
How many planets in our galaxy can you name?
THE EARTH
How long does it take the Earth to rotate on its axis?
And how long does it take to orbit the Sun?
INVERTEBRATES
Can you name six invertebrates?
PLANTS
Plants are autotrophic: they make their own food
What is the name of the process by which plants do this?
THE EARTH’S ATMOSPHERE
Can you name three meteorological instruments?
What does each one measure?
THE HYDROSPHERE
Water is present on Earth in gaseous, liquid andsolid form Name four different places where youcan find water in nature
Trang 5The Universe
8
1U N I T
Content objectives
In this unit, you will …
• Learn about the characteristics of the Universe
• Calculate astronomical sizes and distances
• Analyse the components of the Universe
• Compare sizes: the Sun and the planets
• Create a constellation poster
What do you remember?
• What are the points of light in this photo?
• What is the difference between … – a star and a planet?
– a moon and a comet?
Key language
Describing
Planets are spherical bodies which orbit the Sun.
Asteroids are rocky objects which are irregular in shape.
Comparing
Dwarf planets are smaller than planets.
The Earth is larger than Mercury
Giving instructions
Study the constellations.
Research more about them on the Internet.
STUDY A UNIT
Look at page 8, the first page of Unit 1
• What is the title of the unit?
• How many different sections are there on the page?
What are they about?
• What do you think you will learn about in Unit 1?
Now look at the rest of Unit 1
• How many sections are there in this unit?
• What are most of the illustrations about?
• Some words are in bold Why is this?
• How many activities are there in this unit?
• What will you do in the Hands on section, page 15?
• What can you find on page 17?
How is this useful?
Symbols
• The text is recorded on the CD
• The information you need isavailable on the CD
MINERALS
Quartz is a mineral Can you name any other minerals?
Can you say what each is used for?
MATTER AND ITS PROPERTIES
Oil floats on water
Which has the greatest density, oil or water?
THE STATES OF MATTER
Look at these three drawings
They represent a solid, a liquid and a gas.Can you match each drawing to its state?
7
Trang 6Getting closer to the stars!Telescopes are used to see objects that are too far away to be seen with the naked eye They also provide a
closer view of distant things Astronomers use large telescopes to study the planets, stars, and other objects
in space Without telescopes, we wouldn’t know much about celestial bodies!
Some telescopes are small enough to be carried in one hand
Others can be huge, bowl-shaped radio telescopes, more than
300 metres in diameter This is longer than three football pitches!
Lenses or mirrors?
Telescopes with lenses are called refracting telescopes
Lenses bend the light
The largest telescopes use mirrors instead of lenses
Telescopes with mirrors are called reflecting telescopes
Mirrors reflect light
Trang 7Optical telescopes consist of a long tube, with one end narrower than
the other They can “perceive” light, just like eyes
objective lens: the
lens closest to theobject being viewed
How does a telescope work?
Objects reflect light This light enters our eyes, and
we see the object Optical telescopes have anobjective lens: a curved piece of glass at the wideend This lens bends the light from the object sothat it forms an image – a picture of the object –inside the telescope The light from this image thengoes through the eyepiece, at the narrow end of thetelescope The eyepiece bends the light back again,
so the object looks big
The Gran Telescopio Canarias (GTC),
also called GranTeCan, is a 10.4 m reflecting telescope, located on a volcanic peak (2,400 metres) on the island of La Palma, Spain
It took seven years to construct!
Activities
1 Galileo Galilei invented the telescope Why was this such an important
discovery? What did astronomers know about the stars before then?
2 Research Have you heard of the Hubble telescope? When was it built?
Where is it? What pictures does it take?
Trang 8The Universe 1
U N I T
Content objectives
In this unit, you will …
• Learn about the characteristics of the
Universe
• Calculate astronomical sizes and distances
• Analyse the components of the Universe
• Compare sizes: the Sun and the planets
• Create a constellation poster
What do you remember?
• What are the points of light in this photo?
• What is the difference between …
– a star and a planet?
– a moon and a comet?
Dwarf planets are smaller than planets.
The Earth is larger than Mercury.
Giving instructions
Study the constellations.
Research more about them on the Internet.
Trang 91 Find ten words in the word search.
2 Imagine an alien friend from
another galaxy wants to write to you Write your galactic address.
What makes up the Universe?
The Universe is all the matter, energy and space that exists
The Universe is made up of galaxies which contain stars Stars can have planetary systems
made up of planets and satellites Galaxies are separated by vast spaces
Scientists developed two different theories to explain what
the Universe was like
In 1610, Galileo Galilei invented the telescope, and proved the
Heliocentric theory: the planets and stars revolve around the Sun
• Geocentric theory
2ndcentury BC: Ptolomy
proposed that the Earth was
the centre of the Universe
That is, the Sun, Moon and
planets orbited the Earth
• Heliocentric theory
In 1542, NicolasCopernicus proposedthat the Sun was at thecentre of the Universe
Galaxies are a vast collection of stars, dust and gases, held together by the
gravitational attraction between the components They appear in groups called
galaxy clusters Scientists think the vast spaces between the galaxies are empty.
Our galaxy, the Milky Way, belongs to the Local Group galaxy cluster
Stars form when clouds of gases are pulled together by gravitational forces They
are so hot inside that they emit heat and light A galaxy can have up to five hundred
thousand million stars An enormous cloud of gas and dust, a nebula, surrounds
the stars
Planets are bodies which orbit some stars They do not emit light; they receive light
from the star They make up planetary systems Our planetary system is the Solar
System It is made up of eight planets and one star, the Sun, as well as moons,
comets and asteroids The Solar System is located on a spiral arm of the Milky Way
Natural satellites orbit some planets The Earth’s natural satellite is the Moon.
Trang 102 How big is the Universe?
The radius of the Sun is 109 times greater than the radius of the Earth.
Activities
3 Express the distance of Mercury, Mars and Pluto
from the Sun in kilometres.
4 Research the term light-year Why is it used in
The Earth seems huge, but, in reality, it is small
compared to the Sun The Sun is only one
of the millions of stars in the Milky Way
To imagine the size of the Universe,
use these comparisons with everyday objects
• Imagine the Sun is the size of a pea
• The closest star is another pea, five hundred
and forty kilometres away from the first pea
• The Earth is like a particle of dust situated
two metres away from the first pea
• The Milky Way contains one hundred thousand
million peas which form a circle with a radius
of seven million kilometres
What units of measurement
do astronomers use?
• Astronomical unit (AU) This is the distance
from the Earth to the Sun Approximately
150 million kilometres Compare the distance
of these planets from the Sun:
– Mercury: 0.4 AU
– Mars: 1.5 AU
– Pluto: 39.4 AU
• Light-year This is the distance light travels in
one year Light travels 300,000 km
in one second or
9.5 trillion km
in one year
Did you know that ?
Trang 11rotational axis of the Moon rotational axis
terrestrial orbit
ecliptic plane
The Solar System was formed approximately
five thousand million years ago from the gas and
dust of a nebula
Our Solar System is made up of the Sun, eight
planets with their satellites, dwarf planets and
small solar system bodies The Sun is the central
body
• The Sun consists mainly of two gases:
hydrogen and helium It is the closest star
to Earth
• Planets are spherical bodies which revolve
around the Sun They all move in elliptical
orbits, held by the gravitational force of the
Sun Planets are much larger than other
celestial bodies which orbit the Sun
Mercury, Venus, Earth and Mars are made up
mainly of rock Jupiter, Saturn, Uranus and
Neptune are made up mainly of gases.
• Dwarf planets are spherical bodies which orbit
the Sun They are smaller than planets
• Small solar system bodies are other celestial
bodies which orbit the Sun They include
asteroids, comets and satellites Satellites
orbit planets and consist of rock
Activities
5 Which planet …
• takes the longest to orbit the Sun?
• is the fastest to orbit the sun?
• has the longest days?
• has the shortest days?
6 Why is a “day” on Venus longer than its “year”?
Period of revolution
How do the planets move?
Celestial bodies like the Earth, have two types of movement:
The planets in the Solar System
Orbit A curved path which
a celestial body follows in itsrevolution around another celestialbody The orbit of the Earth
around the Sun is an ellipse
Rotation Celestial bodies spin or rotate
on an invisible axis This invisible line is
called the rotational axis.
Revolution Celestial
bodies revolve around
other celestial bodies
Trang 124 Which are the inner planets?
INNER PLANETS Terrestrial or rocky planets: the crust and mantle are
made of rock The core is metallic
the smallest and closest to the Sun
rotates in opposite direction
the only planet with life
very thin atmosphere
In 2004, the robots Spirit and Opportunity landed on Mars They investigated the possible existence of water
The Earth is the only planet that has life on it The other
planets are too hot or too cold.
Mercury Diameter: 4,880 km
Venus Diameter: 12,104 km
Earth Diameter: 12,740 km
Mars Diameter: 6,794 km
The inner planets are the four planets closest to the Sun: Mercury, Venus, the Earth and Mars
Did you know that ?
Pluto, Ceres and Eris are
dwarf planets Pluto used to
Trang 13Jupiter, Saturn, Uranus and Neptune are the four outer planets.
They are called gas giants because they consist mainly of gases
Activities
9 Which planet …
• has the most satellites?
• is closest to the Sun?
10 If you live on Venus, will
the Sun rise in the East and set in the West?
OUTER PLANETS Gas giants: they consist mainly of gases
greatest distance from the Sun
Jupiter Diameter: 142,984 km
Saturn Diameter: 120,536 km
Uranus Diameter: 51,118 km
Neptune Diameter: 49,492 km
Saturn’s rings are made up of small particles, mostly ice.
Trang 146 What are small Solar System bodies?
There are two main types: asteroids and comets They orbit the Sun
• Asteroids are rocky objects which are irregular in shape They can
be several hundred kilometres in diameter, but most are only
a few metres wide Asteroids orbit around the Sun Most of them
are between the orbits of Mars and Jupiter This area is called
the asteroid belt.
• Comets are small bodies that travel around the Sun in highly
elliptical orbits They are irregular in shape The nucleus is made
up of a mass of ice, dust and gas When comets travel close
to the Sun, some of the ice evaporates, creating the long,
bright tails of the comets
Activities
11 Compare the main characteristics of the inner and outer planets.
12 Describe an inner or outer planet Your partner will identify it.
This inner planet This outer planet
is smaller / larger than
is the largest / smallest.
Uranus
Saturn
comet
Earth Mercury
Trang 15Hands on
Prepare a constellation poster
1. Study these constellations Which ones can you
see in the night sky where you live?
2. Choose one of the constellations and make a poster.
a Find more information in encyclopedias or on the Internet.
b Draw the constellation, or cut out a drawing
or a photo of it.
c Write some sentences about the constellation.
Constellations are imaginary patterns of bright stars.
All societies have invented constellations The
Ancient Greeks invented the constellations we call
the twelve signs of the zodiac
There are 88 official constellations However, most
of them do not really look like the mythical figures
they represent
The night sky looks different in the Northern and
Southern Hemispheres The position of the
constellations changes with the seasons because
of the movement of the Earth
b Write the dates associated with this sign.
14 Choose another constellation.
Research more about it on the Internet.
Orion represents the hunter.
The three stars in the middle are his belt
His sword hangs from his belt.
You can see his sword and his bow.
The constellation Orion
Trang 1615 Label each diagram with the name of …
a a theory of the universe
b the person who proposed the theory
16 Make a drawing of the Solar System and label it: the
Sun, the inner planets, the outer planets, Pluto and the asteroid belt
17 Make a timetable of your daily activities on these
planets Give an approximate duration for each.
• Earth Rotation: 24 hours
• Mercury Rotation: 58.65 Earth days
• Jupiter Rotation: 9.841 Earth hours
18 What two types of movement do all planets have?
Describe them.
19 Describe the composition, temperature and
movement of the Sun
20 Make an illustrated list of the planets Write them in
order: start with the closest one to the Sun
21 Talk about astronomical distances with a partner.
How far away is … from …?
It is … km / … light-years away
22 Research the latest astronomic discoveries Report
your findings to the class.
23 This drawing shows the positions of a comet
in orbit
When a comet gets close to the Sun, why does it develop a tail? Why does an asteroid not?
Duration on …
Astronomic distances from the Earth
24 Draw a diagram of the Solar System seen from
above Include the rotation and revolution movements of each planet.
25 Copy and complete to situate the Moon in the
Universe:
The Moon is a satellite of … which belongs to the planetary system called … The star of this planetary systems is … It belongs to a galaxy called … This galaxy is part of the galaxy cluster called …
Trang 17Early concepts
• Geocentric theory: the Earth is the centre of the Universe The Sun, Moon, stars and planets revolve around the Earth.
• Heliocentric theory: the Sun is the centre of the Universe The Earth, planets and stars revolve around the Sun.
Components
• Galaxies are grouped together in galaxy clusters
• Galaxies contain thousands of millions of stars.
• Stars are massive spherical bodies of gases Some stars have planetary systems with planets,
satellites, asteroids and comets
What should you know?
Units of measurement
• Astronomical unit (AU): the distance between the Earth and the Sun, about
150 million kilometres.
• Light-year The distance that light travels in one year: about 9.5 trillion kilometres.
The Solar System
Projects
First, list the factors that make life possible on Earth.
Then, investigate this website: http//solarsystem.nasa.gov/planets/profile.cfm?Object=Mars
The Solar System is the planetary system of our Sun.
It consists of:
• The Sun: a medium-sized star in the Milky Way galaxy.
• Planets:
Inner: Mercury, Venus, Earth and Mars.
All are rocky
Outer: Jupiter, Saturn, Uranus, and Neptune All are gaseous.
• Dwarf planets: Pluto, Ceres, Eris
• Natural satellites: celestial bodies which revolve around planets and dwarf planets.
• Small Solar System bodies Asteroids: small rocky bodies which orbit the Sun Some form belts The asteroid belt: a band of asteroids between the orbits of Mars and Jupiter Comets: masses of ice and rock found beyond the orbit of Pluto.
1
Trang 18Planet Earth 2
U N I T
Content objectives
In this unit you will …
• Learn about the Earth’s characteristics
• Identify lunar phases
• Describe the geosphere
• Learn about the Earth’s “spheres”
• Reproduce conditions of solar and lunar
eclipses
What do you remember?
• In this photo, what does each colour correspond to?
• Is the Earth an outer or an inner planet?
• What is the interior of the Earth like?
• Where does life exist on Earth: in the geosphere or the biosphere?
Key language
Describing
Water exists in three states.
It takes 28 days to orbit the Earth.
Expressing cause and result
This causes the sequence of day and night This makes the seasons occur.
Comparing
The days get shorter.
Ocean trenches are the deepest areas.
Trang 19The Earth is special for many reasons The Earth is
the only planet with:
• an atmosphere containing oxygen
• an average temperature of 15ºC
• a water cycle
• life as we know it
All these characteristics make the Earth a unique
planet in the Solar System
• The atmosphere consists of a mixture of gases.
Nitrogen and oxygen are the most abundant.
Oxygen is essential for plant and animal
respiration There is also carbon dioxide,
essential for photosynthesis
• The average temperature is 15°C on the
Earth’s surface This is possible because of the
distance from the Sun and the composition of
the atmosphere
• Water exists in three states (ice, liquid, water
vapour) due to temperature variations These
variations make the water cycle possible
Activities
1 Draw a diagram of the Earth, as seen from
space Draw two people: one at the North Pole and one at the South Pole
2 Find out the mixture of gases and the average
temperatures of Venus and Mars Why do you think life is only possible on Earth?
• The Earth has a relatively large natural
satellite, the Moon The gravitational attraction
of the Moon causes ocean tides
• The Earth’s magnetic field protects living
beings from dangerous solar radiations
• Conditions exist for life Thousands of millions
of years of evolution have produced the variety
of species there are today This includeshumans
• There is considerable geological activity on the
Earth: earthquakes, volcanoes, mountainbuilding, erosion, etc
Trang 202 How does the Earth move?
The Earth moves in two different ways:
• Rotation: The Earth rotates on a slightly tilted
axis, always in the same direction This
rotation causes the sequence of day and night.
• Revolution: The Earth’s revolution around the
Sun is an ellipse It takes 365 1⁄4days to
complete the revolution This is one year
The rotation of the Earth It is day on the half of the Earth facing the Sun It is night on the half facing away from the Sun.
direction of rotation
North Pole
South Pole
Northern Hemisphere
plane
of the Earth’s orbit
Southern Hemisphere rotational axis
Equator
D y
Night
Spring The days get longer and the nights get shorter until 21 st June - the longest day
Spring equinox
21 st March
Winter The days get longer and the nights get shorter On 21 st March, day and night are the same length.
Winter solstice
21 st December
Summer The days get shorter and the nights get longer On 22 nd September day and night are the same length.
Autumn equinox
22 nd September
Solar rays strike the Earth at a
steeper angle and produce less heat
What causes the seasons on Earth?
Two factors combine to cause the seasons:
• the revolution of the Earth around the Sun
• the Earth’s axis is tilted at an angle of about 23.5ºThe tilt of the axis causes differences in temperatureand in the duration of day and night
The Sun’s rays strike the Earth in different waysdepending on the seasons
The tilt of the axis makes the seasons occur atdifferent times of the year in the Northern andSouthern Hemispheres
Summer
Winter
Solar rays strike perpendicular to the Earth’s
surface and produce more heat.
23.5°
Trang 21The Moon moves in two different ways:
• Rotation The Moon takes 29.5 days to
rotate once on its axis: a “lunar day”.
• Revolution The Moon takes about
twenty-eight days (twenty-seven days
and eight hours) to orbit the Earth once
A “lunar month” is the period of time
between two new moons It is about 29.5 days
A “lunar day” is as long as a “lunar month”
As a result, the same side of the Moon alwaysfaces the Earth
The same side of the Moon always faces the Earth The red dot
indicates the dark or hidden side It is never visible from Earth.
New Moon
The Moon is between the Sun and the
Earth, so the Moon is not visible
The dark side (not illuminated) faces the
Earth The Moon rises and sets with the
Sun, but you cannot see it from Earth.
The phases of the Moon
First Quarter
Half the side is lit by the Sun
The illuminated part slowly increases.
It rises at noon
and sets at midnight.
Last Quarter Half the side is lit by the Sun The illuminated part slowly shrinks It rises
at midnight and sets at noon.
Full Moon When the Earth is between the Moon and the Sun, the entire Moon is visible The illuminated side faces the Earth
It rises and sets with the Sun.
Activities
3 Draw a diagram to show the phase of the
Moon in the Northern Hemisphere today.
4 When is there a New Moon?
5 Draw a diagram of the phases of the
Moon in the Southern Hemisphere.
1
2
3
4 5
6 7
8
Trang 22Hands on
If the Moon passes between the Sun and the Earth, and blocks
off the sunlight, a solar eclipse occurs.
If the Moon passes behind the Earth, so the Earth prevents sunlight
from reaching the Moon, a lunar eclipse occurs.
Reproducing eclipses
1. Reproduce a solar eclipse Position the planets: the Moon should block the Sun’s light
and project a shadow on the Earth.
2. Reproduce a lunar eclipse Position the planets: the Earth should block the Sun’s
light and project a shadow on the Moon Remember: a lunar eclipse can only take place during a full moon.
3. In your notebooks, copy the diagrams for both eclipses.
the Moon the Sun
Trang 23• The geosphere The solid part which includes
the crust, mantle and core The upper 100 km
of the geosphere is called the lithosphere:
it is the most rigid part
• The atmosphere The air: a layer of gases which
envelops the Earth
• The hydrosphere All the water on the Earth.
• The biosphere All the living things which
inhabit the Earth
Activity
8 Show the three layers of the
geosphere in a diagram Label each layer: main components,
temperature and state: solid or liquid.
Label the two types of crust.
continental crust
(thickness varies from 7 to 70 km)
oceanic crust (thickness varies from 7 to 10 km)
The geosphere
The geosphere consists of three concentric layers: the crust,
mantle and core The crust and the upper mantle make up
the lithosphere.
The crust is the outer layer of
rock The most abundant
minerals are silicates
• The continental crust
volcanic rock, is the
most common rock
The Earth is the only known planet which contains water and living things
It is made up of four interrelated parts or “spheres” These are:
The mantle is the middle layer,
below the crust It lies 2,900 km below thesurface It is made up
of mostly solid rockmaterial Thetemperature ishigher here, from1,000ºC to4,000ºC, sosome areas aremelted rock
The core is the
centre of theEarth, below themantle It is made
up mainly of iron.The temperature is
over 4,000°C The outer
core is liquid The inner core is solid.
mantle
outer core (liquid) inner core (solid)
Trang 245 What is the surface of the Earth like?
From outer space, the Earth looks blue because of
the vast expanses of water on its surface
The distribution of materials that make up the
Earth’s crust form the different types of land relief
Continental relief features
• The average altitude is 600 m
• The three main relief features are:
– Mountain ranges Chains of high mountains.
Examples: the Himalayas in Asia or the Andes
in South America
– Great plains Large extensions of flat land.
Examples: the Amazon plain in SouthAmerica or the Sahara desert in Africa
– Continental shelves The areas near the
coastline, under the sea, that are made ofcontinental crust, not oceanic crust Theseareas slope down from the coastline to a fewkilometres out to sea, to a depth of about
200 metres
Ocean floor relief features
• The average depth is 4,500 m
• The main relief features are:
– Oceanic (mid-oceanic) ridges Chains
of submarine mountains with intense volcanic activity Example: the Mid-Atlanticridge
– Oceanic trenches The deepest areas
of the ocean Example: Mariana Trench:11,034 m deep
– Abyssal plains The largest plains on the
planet: 4,000 or 4,500 m deep
– Submarine volcanoes may create volcanic
archipelagos Examples: the Canary Islands,
the islands of Hawaii
Oceanic relief forms can rise up to 2 km from the ocean floor In some places they appear above the water to form islands
Example: Iceland
Cross-section of the Earth’s surface
submarine volcano
mid-oceanic ridge
oceanic trench abyssal plain
abyss continental shelf
Trang 256 What are the other three Earth “spheres”?
Apart from the geosphere, the other three Earth “spheres”
or systems are the atmosphere, the hydrosphere and the
biosphere
The atmosphere
The atmosphere is the layer of air which surrounds the Earth
Air is a mixture of gases The main components are: nitrogen
(78 %) and oxygen (21 %) Oxygen is one of the necessary
conditions for life There are also small quantities of carbon
dioxide (CO2) and other gases
The hydrosphere
The hydrosphere is all the water on, under and above
the Earth
The hydrosphere is made up almost exclusively of liquid
water, but also snow and ice Other materials in the
hydrosphere are the mineral salts in water Sea water is very
rich in mineral salts, but fresh water has few salts.
The biosphere
The biosphere includes all the living things which inhabit
the Earth Living things influence the physical and chemical
changes in the Earth For example:
• In the Earth’s crust: Animals live in the ground and plants
take mineral salts from the soil Plant roots can break up
rocks
• In the atmosphere: Microorganisms which live in the soil
produce nitrogen Oxygen is produced during
photosynthesis by plants, algae and some bacteria Many
living things cause evaporation
• In the hydrosphere: Living things contain water Plants
take water from the ground Many organisms live in aquatic
environments
Activities
9 Say a relief feature Your partner
says if it is continental or ocean floor.
10 Which continental feature is under
the sea?
11 Describe the four different spheres
that make up the Earth List examples of features in each sphere.
Coral produces exoskeletons which accumulate to form a
rocky shelf
This atolon in Tahiti is made up of living
things.
Did you know that ?
The water cycle refers to how water
evaporates, rises, condenses, falls
to the Earth as rain or snow and
moves around
This cycle was described 2,500 years
ago by Thales.
Trang 2612 Draw the Earth Include an arrow pointing in the
direction in which it revolves When does the Sun rise where you live?
13 Draw the Earth and its orbit Show four positions.
a Indicate the solstices and the equinoxes Divide the orbit into four parts: one for each season in the Northern Hemisphere.
b Colour each season a different colour Tip:
summer begins with the summer solstice and ends with the spring equinox.
14 Why is the Sun higher over the horizon at noon
in summer than in winter? Does this occur
at the same time of year in both hemispheres?
15 Think about the seasons Use this information:
Solstices summer / winter Equinox spring / autumn The Sun is above the Equator Day and night are the same length.
a When it is summer in the Southern Hemisphere, what season is it in the Northern Hemisphere?
And when is it spring there?
b What causes this difference in the seasons?
16 Match each picture of the Moon with a number
in the diagram below.
17 The ecliptic is an imaginary plane It passes through
the centre of the Earth and the centre of the Sun.
a Does it go through the centre of the Moon?
b Does it pass through only sometimes?
18 The Moon has a dark side because each time
it completes a turn around the Earth, it rotates
on its own axis This takes 28 days.
With a partner, demonstrate the movement
of the Moon around the Earth.
19 What are the main differences between
the continental crust and the oceanic crust?
20 Match each phrase to: geosphere, hydrosphere,
atmosphere or biosphere
• water in a river
• waves in the sea
• sand on a beach
• fish, birds, plants or other living things
• the air you breathe
• clouds
21 Two friends are collecting rocks Who is right? Why?
Girl: These rocks belong to the geosphere.
Boy: No, they belong to the lithosphere.
22 Think about the Earth’s rotation and answer.
a Why are days longer in the summer?
b Why do days and nights last for six months
3 4 5 6 7 8
Trang 27• It has an intense magnetic field.
• The atmosphere contains mainly nitrogen, oxygen and carbon dioxide.
• The average temperature is 15ºC.
• Water exists on Earth in solid, liquid and gaseous states There is a water cycle.
• The Earth has one large natural satellite, the Moon.
• Life exists on Earth.
• Rotation The Earth rotates on its axis The axis is tilted 23.5º This rotation creates day and night.
• Revolution The Earth revolves around the Sun Its orbit is elliptical
These two movements and the Earth’s tilt cause the seasons Other consequences are the differences in the length of day and night.
What should you know?
The Moon takes almost 28 days to orbit the Earth It takes the same length
of time to rotate once on its axis
Lunar phases: New Moon, First Quarter, Full Moon and Last Quarter
• Solar eclipse: the Moon blocks the light from the Sun.
• Lunar eclipse: the Earth blocks the light from the Sun so it does not reach the Moon.
The gravitational attraction or “pull” of the Moon on the oceans causes the tides.
Geosphere: the solid part of the Earth It consist of the:
• Lithosphere: the crust and the upper mantle
– Continental crust: makes up the continents.
– Oceanic crust: makes up the ocean floor The Earth’s surface is made
up of continental features and ocean floor features.
• Mantle: the middle layer of the Earth, made of rock.
• Core: the centre of the Earth, made up of metals Outer core: liquid Inner core: solid.
Atmosphere: the layer of air which surrounds the Earth It consists of a mixture of gases.
Hydrosphere: all the waters on the Earth.
Biosphere: the part of the Earth where living things exist Living things can
• Shake together a mixture of gravel, cork and water Allow this to settle Observe the separation in layers by density.
• Compare with the diagram of the geosphere on page 23 Identify the crust, mantle and core represented
in your experiment.
2
Trang 28All creatures great and small
The Earth is the only planet we know which is capable of supporting life
1 How many living creatures can you find?
2 Check your answer in the word snake.
3 Now put them into three different groups Explain why you chose them.
Trang 294 Match each task, a-f, to its
corresponding part of the
microscope.
5 Look at the pond water through the microscope What a surprise!
Use the code to write the vowels and discover the names of the microorganisms Code: A E I O U
Look at these drops of water from
the pond Can you see anything in
them? Some living things are so
small they cannot be seen with the
naked eye They can only be seen
through a microscope
iris diaphram
fine focusing knob
cover slip
objective lenses
nosepiece
arm
a This magnifies the specimen
b This increases the amount of
light
c This is where you put the
specimen
d This is where you look through
e This is where you change the
magnification
f This is used for fine focusing
Trang 30Living things 3
U N I T
Content objectives
In this unit, you will …
• Define the characteristics of living things
• Describe cell structure and cell functions
• Classify unicellular and multicellular living things
• Classify living things into five kingdoms
• Make slides to study cells
What do you remember?
• Can you name any of these living things?
• Classify them into groups: plants, animals, vertebrates, invertebrates
• What do all living things do?
• What is the animal kingdom?
• What kingdom do human beings belong to?
Key language
Expressing facts
Living things feed, reproduce and interact.
Making impersonal statements
Cells are organised into levels.
Expressing purpose
Photosynthesis enables plants to obtain energy Water is used to transport substances.
Trang 311 True or false? Biodiversity refers to all living things.
2 Why does biodiversity vary throughout the world?
3 Match each photo with a factor that reduces
biodiversity
a pollution
b destruction of habitats
c uncontrolled hunting
d introduction of exotic species
Biodiversity is the variety of life on Earth in all its
forms Biodiversity is the result of a slow process
called evolution Evolution began with the first
life forms and still continues today Species change,
and adapt to the environment
Scientists believe there may be more than thirty
million species Approximately two million species
have been classified
Biodiversity varies tremendously throughout theworld It is influenced by climate zones andhabitats For example, more than half the world’sspecies live in tropical rain forests and coral reefs.Some countries have many different climate zonesand habitats As a result, they have more biologicaldiversity For example, Spain has more biologicaldiversity than other European countries
Destruction
of habitats caused by deforestation, the construction
of roads, dams, etc.
Introduction of exotic species can destroy local species For example, the river crab.
Uncontrolled hunting and fishing endangers many species:
for example the Iberian lynx
(Lynx pardinus)
is in danger of extinction.
Pollution of water, soil and the atmosphere, caused
by agricultural, industrial and urban development
Did you know that ?
Rain forests
have the
greatest
biodiversity.
What factors can reduce biodiversity?
Whole species of living things become extinct
every day for these four factors:
1
3
4 2
Trang 322 What do all living things have in common?
All living things have a similar chemical
composition
All living things also carry out three functions:
nutrition, interaction with the environment and
reproduction
Nutrition refers to all the processes which enable
living things to obtain the energy and matter they
need to live
Living things can be classified into two groups
depending on how they feed
• Autotrophs produce the organic substances
which they need from inorganic substances
They take substances like water, mineral salts
and carbon dioxide from the soil and the
atmosphere To obtain these substances,
autotrophs need energy They get energy from
sunlight through a process called
photosynthesis Chlorophyl enables them to do
this Plants, algae and some bacteria are
autotrophs
• Heterotrophs feed on organic matter which is
already elaborated: for example, living things or
their remains Animals, fungi, some bacteria and
all protozoa are heterotrophs
Interaction with the environment: all the
processes which enable living things to react to
changes in their environment For example: plants
grow towards the light; animals flee from
predators
Reproduction: refers to all the processes which
enable living things to create new living things
There are two basic types:
• Asexual reproduction involves one living
thing For example: a sponge can produce buds
which give rise to new sponges
• Sexual reproduction involves living things of
different sexes Each one provides a sex cell or
gamete The two sex cells join to form the first
cell of a new living thing, the zygote.
What function is this cheetah carrying out?
Why are all the flowers following the Sun? What function are they carrying out?
Activities
4 Complete:
5 Test your partner Ask questions:
Which processes enable living things to create new living things?
adapt to their environment?
obtain the energy they need?
Heterotrophs feed on Autotrophs obtain Sexual reproduction involves Asexual reproduction involves
Trang 333 What are living things made up of?
Activities
6 Compare organic and
inorganic substances:
7 Ask questions about
organic and inorganic substances For example:
8 Use the pie charts to
calculate, in grams, the approximate value of each group of biomolecules:
a Weigh yourself, then calculate the
biomolecules in your body
For example,
100 kgs = 60 kg water
b a sunflower: 2.250 grams.
All living things are made up of chemical substances Carbon (C), oxygen (O),
hydrogen (H), and nitrogen (N) make up about 95 % of all living matter
Combinations of these elements form molecules of living matter called
biomolecules
Living things are made up of two kinds of substances: inorganic and organic.
Inorganic substances
Inorganic substances do not contain carbon They
are present in living things and non-living things
The principle inorganic substances are:
• Mineral salts have various functions: they make
up different structures, like shells, bones and
teeth They are present in internal fluids, like
tears, sweat and blood
• Water is the most abundant substance in living
things Living things obtain water directly
by drinking it, or indirectly from substances that contain water Plants obtain water from the environment Water is necessary forchemical reactions and to transport all othersubstances
Organic substances
Organic substances are unique to living things Carbon is their
principal element Organic substances present in living things are:
Organic and inorganic substances are present in different amounts in
plants and animals
16 %
mineral salts 3.4 %
Glucides glucose
cellulose
to provide energy
to make structures Lipids fatty acids
cholesterol
to provide energy
to make structures Proteins haemoglobin
antibodies keratin
to transport oxygen
to fight microorganisms that cause disease
to make structures: hair, nails Nucleic
acid
DNA RNA
to control cell function and heredity
Trang 344 What are cells?
Cells are the smallest unit of life They are the structural
and functional units for all living things
• All living things are made up of one or more cells
• Cells carry out the functions of nutrition, interaction
with their environment and reproduction
• Most cells are very small For example, skin cells
are approximately one hundredth of a millimetre
in size
• All cells come from other cells
• Prokaryotic cells have no nucleus They have
no nuclear membrane Genetic material is
dispersed throughout the cytoplasm They are
simpler and smaller than eukaryotic cells
Bacteria are made up of prokaryotic cells
How is a cell organised?
• The cell membrane covers the whole cell.
• Cytoplasm is the inside of the cell It is a jelly-like
substance Many of the chemical reactions of the cell
take place here Organelles are small structures in the
cytoplasm They are responsible for respiration, making
and storing nutrients, etc
• Genetic material controls and regulates how cells
work This DNA contains the hereditary information
that is passed from one cell to the daughter cell DNA
makes up the chromosomes
Prokaryotic cell
organelles cytoplasm
cell membrane genetic
material
Eukaryotic cell
nucleus
organelles cytoplasm
cell membrane
Activity
9 Read the chart, then make sentences
to describe the cells: Eukaryotic cells are
found in animals.
Eukaryotic cells
Prokaryotic cells
What are the two basic types of cells?
Did you know that ?
Robert Hooke was the first person to use
the term cells
In 1665, with this microscope, he observed cavities
in a thin slice of cork, and called
them cells.
• Eukaryotic cells have a nucleus, separated
from the cytoplasm by the nuclear membrane.Algae, protozoa, fungi, animals and plants haveeukaryotic cells
Trang 35Both animals and plants have eukaryotic cells,
but there are some differences
• Plant cells have a rigid cell wall which
surrounds the plasmatic membrane The cell
wall gives the cell its shape and strengthens it
• Plant cells are usually polyhedral, but animal
cells are various shapes: round, square, star-like
• Plant cells have unique organelles called
chloroplasts which are responsible for
photosynthesis
• The nucleus of plant cells is usually found on
one side A vacuole takes up most of the space.
Animal cells also have vacuoles, but they aresmaller
Cell membrane Like a
skin around the cell It
keeps the cell together and controls what passes
in and out.
Nucleus Contains genetic material
Cytoplasm.
Contains the organelles:
mitochondria, vacuoles…
Vacuoles.
Like bags, surrounded
by membranes where substances, mainly water, accumulate.
Mitochondria.
Where energy
is obtained from nutrients.
Chloroplasts These store a green pigment,
chlorophyll, which absorbs the Sun’s energy
to elaborate organic matter during photosynthesis.
10 Make a Venn diagram: show the similarities and differences
between animal and plant cells.
11 Draw and label an animal cell with all its parts.
Trang 3612 Label each plant cell indicating its magnification.
13 Imagine that your hypothesis were incorrect What result would make this obvious?
14 Imagine you have an unidentified sample Hypothesis: If this is a living thing, it will be made up of cells
Is this hypothesis correct? Can you use it to differentiate between living and non-living things?
What would you do to classify the sample as living or non-living?
Hands on
A hypothesis is a proposal It is used as a basis
for reasoning Scientists use experiments and
observation to test the validity of a hypothesis.
Hypotheses show the relationship between two
or more facts For example: we know that cell walls
in plant cells are made of cellulose
Cellulose is a rigid substance that holds the cell parts together in a polyhedral shape.
Resulting hypothesis: If you observe cells through
a microscope that are polyhedral in shape and joined together by thick walls, you know they are plant cells.
1 Take a moss plant specimen and use tweezers to remove
a phyllode.
2 Place the phyllode on a slide Add a drop of water
3 Place the cover slip on the specimen, look through
the microscope and draw the specimen
Use different magnifications.
At higher magnifications you may be able
to see and count the chloroplasts.
Making a specimen of plant cells
1 To obtain cells, rub the inside of your cheek gently with
a clean cotton bud.
2 Spread the cells on a slide and add a drop of water.
3 Stain the cells with methyl green or a similar dye
4 Put the cover slip on, look through the
microscope and draw the specimen.
Making a specimen of animal cells
Notice that the plant cells have a polyhedral shape.
The animal cells are irregular, and they are not joined together.
Check your hypothesis
Making a hypothesis Using a microscope to study cells
Trang 37Living things can be classified into two different
groups: unicellular and multicellular.
• Unicellular living things have only one cell
They sometimes form colonies Unicellular living
things feed, interact with the environment and
reproduce Example: paramecia
• Multicellular living things have many different
cells Example: plants and animals
Multicellular organisation
Cells in multicellular living things are organised
in levels The cells work together to carry out
the vital functions
• Cells are specialised: they have specific
functions Each type has a unique shape and
structure
• Tissues are groups of cells with the same
function Example: muscle cells form muscle
tissue
• Organs are groups of various tissues which act
together Example: a muscle is an organ made
up of muscle tissue, nerve tissue, connective
tissue and blood tissue
• Systems are made up of several organs.
Example: the digestive system includes the
stomach, the intestines, etc
Form and function of cells
Specialised Cells
Sperm cells
have a tail (flagellum)
so they can swim toward the ovum
Red blood cells
consist mainly of haemoglobin to transport oxygen
Neuron or Nerve cells
are like wires with
a lot of extensions
so they can conduct and capture messages
Root hair cells
are long and thin so they can absorb water and mineral salts from the soil
Cells
Tissue
Organ
Muscular system
muscle cell
muscle tissue
muscular system
muscle
Activities
15 Describe one of the specialised cells
Your partner identifies it For example:
A: It has no nucleus B: A red blood cell.
16 What is the difference between tissues, organs
and systems?
Example: are made up of
Trang 387 What are the five kingdoms?
Scientists use criteria for classification to organise living things into groups.
Classification enables them to compare different living things
Scientist classify all living things into five kingdoms by three main criteria:
type of cells, how the cells are grouped, and nutrition
Contains unicellular, prokaryotic
organisms They may be autotrophic or
heterotrophic
Bacteria and cyanobacteria.
Contains unicellular and multicellular living things They are all eukaryotes.
They have no tissues They may be autotrophic or heterotrophic.
Protozoa, algae.
Contains unicellular and multicellular living things They are eukaryotes They have no tissues They are heterotrophic.
Yeasts, moulds, mushrooms.
Contains multicellular eukaryotes They have tissues
They are autotrophic
Mosses, ferns, flowering plants.
Contains multicellular eukaryotes They have tissues They are heterotrophic
Animals: may be invertebrate or vertebrate.
Trang 39Living things can
be differentiated
by the way they feed,
reproduce, interact
with their enviroment,
etc They are classified
into different groups
The main group is the
A species is the first level of classification for living things A species
is a set of living things which are physically similar They reproduce
and usually have fertile descendants.
Animals from the same species have similar appearances
However, there can be differences in structure, size and colouring
between the male and the female This difference is called
donkey
female horse - mare
mule
The lion and lioness are examples
of dimorphism.
A male peacock uses its colourful tail
to attract the female.
Activities
18 Make a list of animals that
show sexual dimorphism
19 Describe the differences
between the male and female of some animals.
Are a heterotroph, cells form tissues
Have a spinal chord
Are a chordate with a backbone
Have warm blood; babies drink mother’s milk
Your thumbs and fingers work together
Walk upright
Talk, have a long childhood
Are intelligent, have little body hair YOU
Trang 4020 Study the illustrations Which represent living
things? Which characteristics support your decision?
21 Classify these living things as autotrophic or
heterotrophic.
22 Copy and complete the chart.
23 Draw an animal cell with the most important
organelles What structures would transform it into
a typical plant cell? Draw them.
Include: mitochondria, cytoplasm, cell membrane
24 Test your classmates Ask questions about the five
kingdoms.
Glucides Lipids Proteins
25 Study the cell diagrams Match each with
a name and description
1 They are long and thin in order to absorb water and mineral salts from the soil.
2 They are shaped like wires with a lot of extensions They conduct messages around the body.
3 They have a tale (flagellum) which enables them
to swim towards the ovum
4 They have no nucleus so they have room to transport oxygen in the haemoglobin.
– Sperm cell – Neuron – Red blood cell – Root hair cell
26 Complete the table on sexual dimorphism
A
D
B E
C F
A B C D
E
F
H G
Which kingdoms
are made up of have