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Vocabulary
asteroids rocky bodies which orbit the stars. astronomical unit the distance from the Earth to the Sun: approximately 150 million kilometres. galaxies a vast collection of stars, dust and gases, held together by gravitational attraction.
geocentric theory proposed that the Earth was the centre of the Universe.
heliocentric theory proposed that the Sun was at the centre of the Universe.
light-year the distance light travels in one year: about 9.5 trillion km.
Milky Way the galaxy where our Solar System is. orbit a curved path which a celestial body follows in its revolution around another celestial body.
atmosphere the layer of gases which envelops the Earth. Nitrogen and oxygen are the most abundant. biosphere the part of the Earth’s surface, sea and air that is inhabited by living things.
core the centre of the Earth, below the mantle. Its temperature is over 4,000°C.
crust the outer layer of the Earth’s surface. It is divided into continental crust and oceanic crust. equinox the time of the year when day and night are exactly the same length.
geosphere the solid part of the Earth which includes the lithosphere, the mantle and the core. hydrosphere all the water on Earth.
lithosphere the upper 100 km of the geosphere. It is is made up of the crust and the upper mantle. lunar eclipse when the Moon passes behind the Earth, so the Earth prevents sunlight from reaching the Moon.
mantle the middle layer of the Earth, below the crust. It is made up of rock. The temperature is from 1,000 to 4,000ºC, so some areas are melted rock. revolution the elliptical path taken by one body around another. The Earth revolves around the Sun. rotation the Earth rotates on its axis. The axis is tilted 23.5 degrees. This rotation creates day and night. solar eclipse when the Moon passes between the Sun and the Earth, and blocks off the sunlight.
water cycle the movement of water around, over, and through the Earth: evaporation, condensation, precipitation, surface runoff and infiltration.
autotrophs living things which produce the organic substances they need from inorganic substances. Plants, algae and some bacteria are autotrophs.
cell membrane the outer covering of a cell. The cell membrane keeps the cell together and controls what passes in and out of it.
chloroplasts organelles with a green pigment, chlorophyll, which absorbs the Sun’s energy to elaborate organic matter during photosynthesis. cytoplasm the inside of a cell where many of the chemical reactions take place.
eukaryotic cells cells which have a nucleus, separated from the cytoplasm by the nuclear membrane.
heterotrophs living things which obtain nutrition from organic matter which is already elaborated. Animals, fungi, and all protozoa are heterotrophs. inorganic substances things which contain no carbon. They are present in living things and non- living things: water and mineral salts.
organelles small structures in the cytoplasm responsible for respiration, making and storing nutrients, etc.
organic substances substances exclusive to living things. Carbon is the principal element. Organic substances include: glucides, lipids, proteins and nucleic acids.
nutrition all the processes which enable living things to obtain the energy and matter they need to live.
photosynthesis the process through which plants obtain nutrition.
prokaryotic cells cells with no nucleus or nuclear membrane. Genetic material is dispersed throughout the cytoplasm. They are simpler than eukaryotic cells.
species the first level of classification for living things. A group of living things which are physically similar. They reproduce and usually have fertile descendants.
Living things
3Planet Earth
2 877310 _ 0132-0136.qxd 4/8/08 15:55 Página 132annelids invertebrates with soft, cylindrical bodies divided into segments, with organs in each segment. Most breathe through gills.
arthropods the largest and most varied group of living things: more than one million species. They live in sea water, fresh water and on land.
cephalopods a group of molluscs. They have tentacles, but no shell. For example: squid, cuttlefish and octopus.
cnidaria jellyfish, corals and sea anemones. They have a soft body, with only one opening and a mouth surrounded by tentacles.
crustaceans a group of arthropods with 10 legs, with usually an aquatic habitat. For example: lobster or crab. echinoderms invertebrate animals which live on the sea bed. For example, sea urchins, starfish and sea cucumbers.
gastropods a group of molluscs. Gastropods have a spiral-shaped shell with a single valve. For example, snails, sea snails and slugs. Slugs have no shell. molluscs a group of invertebrate animals with a soft body divided into head, body mass and foot. For example, squid, mussels, oysters, slugs and snails. myriapods a group of arthropods with worm-like bodies and many legs. They are terrestrial. For example, centipede and scolopendra.
oviparous animals that lay eggs. Eggs are laid by the female and develop outside the body.
platyhelminths invertebrates with long, flat, soft bodies. They have neither legs nor respiratory or digestive systems. Many are parasites.
polyp cnidaria bodies shaped like a tube with the opening at the top. For example, corals and sea anemones. porifera invertebrate animals without organs. Sponges belong to this group.
amphibians vertebrate animals. Their skin is moist and has no covering. They have four legs and are poikilothermal. They undergo metamorphosis. homeotherms warm-blooded animals: capable of keeping their body temperature constant. mammals a group of vertebrate animals. Their bodies are covered with hair or fur. They are homeothermal and have mammary glands.
ovoviviparous animals that are born from an egg. The egg develops inside the female.
poikilotherms cold-blooded animals. They cannot regulate their body temperature, so are warm or cold depending on the environment.
reptiles vertebrate animals with bodies covered with hard scales. They are poikilothermal and most of them are oviparous and carnivorous.
viviparous animals that give birth to live young. Development starts in the mother’s body. The babies feed on the mother’s milk.
angiosperm flowering plants which have seeds inside a real fruit.
dispersal a stage of plant reproduction. The ripe fruit falls off the plant or releases the seeds.
ferns small non-flowering plants. Ferns are vascular. They have roots, stems, and leaves called fronds. fertilisation a stage of plant reproduction. Pollen reaches the stigma, penetrates it, and fertilises the ovules inside the ovary.
fungi have eukaryotic cells and are heterotrophic. Fungi are made up of hyphae, which group together to form the mycelium.
germination the last stage of plant reproduction. Seeds germinate producing a tiny shoot and root. gymnosperm one kind of flowering plant. They have seeds inside a false fruit, like a pinecone. mosses small, non-flowering plants. They are non- vascular. They have no true roots, stems or leaves. pollination the first stage of plant reproduction. Wind and insects transport pollen from one flower to another.
stomata microscopic pores on the underside of a leaf. transpiration process by which excess water is expelled through leaf stomata in the form of water vapour.
vascular plants with conductor vessels to distribute water and nutrients.
yeasts unicellular fungi. Some types are used to make bread, wine, beer, etc.
algae unicellular or multicellular autotrophs. They live in salt and fresh water.
bacteria microscopic, prokaryotic organisms. They belong to the Monera kingdom.
Vertebrates
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Invertebrates
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The plant and fungi
kingdoms
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The simplest living things
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ciliates a group of protozoa with hair-like organs. flagellates one of the groups of protozoa. They move with a flagellum (tail).
protoctist unicellular and multicellular living things. They are eukaryotes and have no tissues. The Protoctist kingdom includes protozoa and algae. protozoa unicellular and heterotrophic living things. Some are parasites, and cause illnesses. rhizopods protozoa with pseudopods (projections of the cell cytoplasm).
saprophytes organisms which live on dead or decomposing matter. They transform organic substances into inorganic substances.
sporozoa a group of protozoa that cannot move. vaccines contain dead or weakened
microorganisms from a specific illness. They teach the body how to fight an illness.
acid rain rain with dissolved pollutants such as sulphur dioxide and nitrogen oxide.
climate describes the characteristic pattern of weather in an area, over a long period of time. global warming in the last century, the atmosphere has warmed between 0.5 and 0.9ºC on average. greenhouse effect a natural phenomenon, essential for keeping the temperatures on Earth suitable for life. CO2in the atmosphere acts like the glass walls of a greenhouse. It traps the heat and prevents it from returning into space.
ionosphere the highest and thickest layer of the atmosphere.
mesosphere a layer of the atmosphere about 40 km thick. It contains clouds of ice and dust. meteorology the study of different atmospheric variables to make weather predictions.
ozone (O3) a gas which exists throughout the
atmosphere, mainly concentrated in the stratosphere. It makes up the ozone layer.
stratosphere a layer of the atmosphere about 30 km thick. There is an increase in temperature from –70ºC at its lower limit, to 0ºC at its higher limit. troposphere a very thin layer which represents 80% of the total mass of the atmosphere. Aeroplanes fly at this level. It is where the greenhouse effect is produced. weather describes the state of atmospheric conditions at a certain place, over a short period of time.
condensation the process in which water vapour changes to liquid.
currents movement of large bodies of water by prevailing winds.
evaporation the process of the water cycle in which liquid water changes to a gas (water vapour). evapotranspiration when water evaporates into the atmosphere from the leaves and stems of plants. groundwater water located beneath the ground. infiltration surface water penetrates into the ground. This occurs more easily if the ground is porous. surface runoff when the movement of surface water across the land forms rivers and streams. tides the rise and fall of water levels due to gravitational attraction of the Moon and the Sun. waves occur on the surface of water, caused by the wind. Wave action causes cliff erosion and creates beaches.
hardness measures how a mineral reacts to being scratched.
impurities small amounts of other substances found in minerals. These can change some mineral properties.
lustre refers to the way minerals reflect light. It can be metallic, or non-metalic.
mixtures are made up of different substances of varying sizes, shapes and colours.
Mohs Scale of Hardness classifies minerals by hardness. One is soft. Ten is the hardest.
non-silicates minerals which contain no silicon: native elements, oxides, sulphides, carbonates and halides. silicates the most abundant minerals on Earth. They are made up of silicon and oxygen. Some common silicates are quartz and feldspar.
streak the colour of the powder left when minerals are scratched.
cementation the process by which sedimentary rock is formed from sediments glued together. compaction the weight of layers of sediments which reduces the spaces between the fragments and squeezes out the water. As a result, salt crystals are formed.
The Earth’s atmosphere
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Minerals
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9Rocks
11 877310 _ 0132-0136.qxd 4/8/08 15:55 Página 134erosion fragments of rocks are picked up and transported by running water, glaciers, or wind. igneous rocks rocks formed from cooled magma. metamorphic rocks rocks formed from other rocks by the effects of heat or pressure.
metamorphism a slow process in which temperature and pressure change parent rock into metamorphic rock.
organic sedimentary rocks made up of organic material, fossils. There are two kinds: oil and coal. plutonic (intrusive) rocks rocks formed as magma cools slowly under the ground over thousands of years.
rock cycle the processes which form, change and recycle rocks over millions of years.
sedimentary rocks rocks formed by the accumulation and compaction of sediment, for example, clay, sand or rock fragments.
volcanic (extrusive) rocks rocks formed as lava cools rapidly on the Earth’s surface.
weathering atmospheric phenomena (changes in temperature, rain, etc.), or the activities of plants and animals which break up rocks.
base units used to measure length, mass, time, etc. capacity the amount of liquid a container can hold when it is full. Capacity is measured in litres (L). degrees Celsius a scale used to measure temperature. 0ºC equals 273.15K or 32ºF.
density the relationship between the mass and the volume of a body. Measured in kg/m3or g/cm3. derived units obtained from a combination of the base units. They are used to measure surface area, volume, speed, density, etc.
International System of Units (SI) a system which defines the base and derived units required to measure the properties of matter.
kelvin one of the scales of the International System of Units that is used to measure temperature. 0 K equals –273.15ºC and –459.67ºF.
mass the amount of matter in a body. Mass is measured in kilograms (kg).
matter all objects that take up space, and have mass. Everything around us is made of matter. surface area the extension of a body in two dimensions, measured in square metres (m2). volume the amount of space matter occupies. Volume is measured in cubic metres (m3).
chemical compound a substance containing two or more elements joined up.
compressibility a property which measures the difficulty of matter to be compressed.
fusion the process by which a solid changes into a liquid.
heterogeneous a mixture of substances where more than one part is distinguishable.
homogeneous a substance which is uniform in structure and composition.
recycle to transform used materials into new materials. regressive sublimation the process by which a gas changes directly into a solid.
solidification the process by which a liquid is cooled and changes to a solid.
solute in a mixture, the dissolved substance. solution any homogeneous mixture.
solvent in a mixture, the part where the substance is dissolved.
sublimation the process by which a solid changes into a gas, without first becoming a liquid.
vaporisation when a liquid evaporates into a gas.
atom the smallest particle of matter which can exist alone. It is made up of a nucleus with protons and neutrons, and electrons.
atomic number the number of protons in the nucleus of an atom. This number is different for each atom. chemical formula symbols which indicate how many atoms make up a molecule.
crystals consist of atoms or molecules arranged in a regular, organised structure.
electrons extremely small particles that orbit the nucleus. They have a negative charge (–) and are
attracted to the positively charged protons in the nucleus. element a substance that contains just one type of atom. It cannot be broken down into anything simpler by chemical reaction.
molecules two or more atoms joined together. neutrons particles in the nucleus which have no charge. periodic table of elements a table in which all elements are grouped with similar elements, with their symbol and atomic number.
protons particles in the atom’s nucleus, which have a positive charge.
Matter and its properties
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Everything is matter
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Atoms and elements
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