Glossary

acid a substance which forms hydrogen ions (H+) when dissolved in water and has a pH of less than 7.

adaptation a species’ genetic adjustment to environmental conditions through the long-term process of natural selection.

air resistance see friction.

algae organisms including seaweeds currently classified as protoctists rather than plants on the basis of their life cycle rather than appearance.

alkali a base that dissolves in water, has a pH of more than 7 and neutralises acids.

allotrope giant structures made of the same element but with different structures and different properties.

amplitude the amount of up and down movement in a wave. The size of the amplitude of a vibration will determine the loudness of the sound produced.

amps a measure of the flow (current) of electricity.

Angiospermophyta phylum of the plant kingdom. Includes flowering plants.

Animalia kingdom. Complex, multicellular, eukaryotic organisms. Cells have no cellulose cell walls, chloroplasts or large, permanent vacuoles. Includes vertebrate and invertebrate groups. Humans are animals.

Annelida phylum of the animal kingdom. Includes true segmented worms such as earthworms, leeches and ragworms.

aphelion the point where a planet is furthest from the Sun.

Arthropoda phylum of the animal kingdom. Includes spiders, centipedes, millipedes, woodlice and butterflies.

asteroids small, rocky objects which orbit the Sun. Sometimes referred to as minor planets.

atom smallest particle of an element consisting of electrons and a nucleus.

atomic mass the sum of the number of protons and neutrons in the nucleus of any element.

atomic number the number of protons in the nucleus of any element.

autotrophs food producers, e.g. green plants, that use the Sun’s energy to make food by photosynthesis.

balanced forces will hold an object still or allow it to continue with a constant velocity.

base a substance that forms hydroxyl ions (OH–) when dissolved in water, has a pH of more than 7 and neutralises acids.

battery a group of cells.

Big Bang an explosion of space and time from which the Universe emerged. This is now thought to have occurred about 14 billion years ago.

black a totally black object will reflect no light.

boiling the rapid change of a chemical from a liquid to a gas that involves the formation of bubbles.

bond energy the energy needed between each atom in a molecule in order to hold the atoms together.

Bryophyta phylum of the plant kingdom. Includes common mosses, liverworts and hornworts.

buoyancy see upthrust.

burning a chemical reaction that involves oxygen and that is exothermic.

carnivore animal (occasionally a plant) that consumes and gains energy from other consumers, i.e. other animals, either herbivore or carnivore.

cell a container of chemicals which react together producing a flow of electrons from one terminal to the other.

cells microscopic building blocks and basic units of life.

chemical formula the symbolic representation of a molecule or compound.

chlorophyll green substance within the chloroplasts of certain plant cells. Absorbs energy in light from the Sun and makes it available to carry out photosynthesis.

Chordata phylum of the animal kingdom. Includes vertebrates and other organisms with a notochord or stiffening rod providing internal support.

chromosome a long thin structure in the nucleus of each cell. Humans have 46 chromosomes, 23 of which are from the father and 23 of which are from the mother. Each chromosome is made from proteins and DNA.

circuit components linked by wires which allow a flow of electricity.

Cnideria phylum of the animal kingdom. Includes jellyfish, corals and sea anemones.

colour filter prevents certain colours of light passing through while allowing through others.

comet chunk of ice and dust in orbit around the Sun.

community a group of plants and animals in a particular habitat.

compound a substance composed of two or more elements in definite proportions by weight.

compression the squeezing together of the molecules when vibrations are set up in a gas.

conceptual understanding an understanding of scientific ideas, e.g. force.

condensation process of changing from a gas to a liquid.

conductor a material which allows electricity to flow through it.

Coniferophyta phylum of the plant kingdom. Includes conifers and firs.

conservation of energy the total energy remains unchanged as it changes from one form to another.

covalent bonding bonding between atoms where electrons are shared.

Darwin the scientist who first described the theory of evolution in his book The Origin of Species.

day and night the day and night cycle is caused by the rotation of the Earth about its axis once every 24 hours.

deceleration the rate of decrease in velocity (some scientists say deceleration is negative acceleration).

decomposers living things that get their energy from dead and decaying matter.

digestion the physical and chemical breakdown of food.

dissolving the process of making a solution where at least one of the chemicals is in a liquid state

DNA a chemical – deoxyribonucleic acid. It forms long double strands wound round each other in the form of a double helix. The strands are joined by chemical bonds.

dominant in each pair of chromosomes there are genes which code for the same characteristic. If the genes programme for different effects, the one which is expressed in the characteristics of the organism, e.g. hair colour, is dominant.

Echinodermata phylum of the animal kingdom. Includes starfish and sea urchins.

eclipse the blocking off of light from one astronomical body by another.

ecology the study of the relationship of living things in their natural environment. The natural environment will include living and non-living things.

ecosystem an integrated unit of a community of living things and the physical environment in a certain area, i.e. a given community and its habitat. Studies of ecosystems will focus on interactions between living and non-living things and on the flow of energy and materials between these parts.

efficiency the proportion of energy which is usefully converted.

elastic energy energy in the change of shape of an object.

electricity a flow of electrons from a negative to a positive terminal.

electromagnetic spectrum a family of wave types which includes light, X-rays, radio waves, etc.

electrons particles which surround the nucleus of an atom and have a negative charge.

element substance consisting of one type of atom only.

endothermic reaction a chemical reaction that takes energy from its surroundings because the total bond energy needed between atoms in the new chemicals is more than the total bond energy in the original reactants.

energy the capacity to do work by moving or heating.

environment the conditions existing in a habitat that will affect a particular organism.

eukaryote eukaryotic organisms are composed of eukaryotic cells that have a well-defined nucleus containing each cell’s genetic material or DNA.

evaporation process in which a liquid changes to a gas.

evolution the process by which organisms have changed over millions of years into different forms. There is a clear sequence, for instance, from dinosaurs to birds.

exothermic reaction a chemical reaction that gives energy to its surroundings because the total bond energy needed between atoms in the new chemicals is less than the total bond energy in the original reactants.

falsification the act of testing out the validity of a theory or hypothesis through searching for negative, falsifying instances.

filament the very fine wire in a light bulb.

Filicinophyta phylum of the plant kingdom. Includes ferns.

fission this occurs when an unstable nucleus splits into two fragments.

food chain the feeding relationship in a given ecosystem which illustrates the flow of energy.

food pyramid a representation of the relative biomass in a food chain and, hence, the relative proportions of energy transfer.

food web a complex interaction of several or many food chains within an ecosystem.

fossil fuel a fuel such as oil, coal or gas, which is stored in rocks. Energy is obtained when these fuels are burnt.

freezing process of changing from a liquid to a solid.

frequency the number of waves passing a given point each second, measured in hertz or megahertz. The frequency of a vibration determines the pitch of the sound produced.

friction (including air or water resistance) the force which occurs between two substances and that tends to reduce movement or prevent potential movement.

fuel a source of heat energy obtained from materials that burn.

Fungi kingdom. Complex, eukaryotic organisms with thread-like hyphae rather than cells. Hyphae may contain one or more nuclei. Chitinous cell walls. No chloroplasts. Includes mushrooms, yeast and moulds.

galaxy an assemblage of stars, nebulae and other interstellar material.

gas a state of matter that completely fills its container and can be compressed.

gene a section of a chromosome which codes for the production of a particular protein.

genetic pertaining to genes or inherited characteristics.

giant structures large numbers of atoms that are bonded together to make a new substance that is very difficult to break apart.

gravitational potential energy energy due to the position of an object above the Earth’s surface.

gravity the force of attraction between all objects with mass.

habitat the natural home of a group of plants and animals that provides all (or nearly all) the needs of the inhabitants.

heat a form of kinetic energy.

herbivore animal that consumes and gains energy from primary producers only, i.e. plants.

heterotrophs organisms not capable of manufacturing their own food. Humans are heterotrophs. They get their food by eating plants and other animals.

heterozygous a person who has two different genes for the same characteristic. One of these genes will be recessive and one will be dominant.

homozygous a person who has two identical genes for the same characteristic.

hydrogen the lightest gas. It is the commonest element in the Universe.

hydroxide a compound which contains a hydroxide ion (OH).

igneous rock rock formed from magma that is solidified.

inherit to have genetic information passed on from a preceding generation.

insulator a material which does not allow electricity to pass through it.

ion an atom that has lost or gained one or more electrons and as a result has a positive or negative charge.

ionic bonding bonding between atoms where electrons are taken or given (transferred).

isotope atoms of the same element which have the same atomic number but different atomic mass because the number of neutrons varies.

key device which can be used to systematically classify or identify living and non-living things. Keys come in different forms.

lichen a symbiotic association between a fungus and an alga. Lichens grow very slowly and are usually found encrusting rocks, gravestones and roofs.

light a form of energy which affects the nerve cells on the retina of the eye. Light travels in straight lines in waves from a source.

lignification process of impregnating and strengthening xylem cells with lignin. In woody plants like trees fully lignified xylem forms woody tissue.

lignin a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae.

liquid a state of matter that takes up the shape of its container and can be compressed a little.

loudness the volume of a sound which is a measure of the energy used to make the sound and is determined by the amplitude of vibrations.

Lycopodophyta phylum of the plant kingdom. Includes club mosses.

mass the amount of matter in a substance – measured in grams or kilograms.

melting process in which a solid changes to a liquid.

Mendel a monk who, in the late nineteenth century, propounded the basics of inheritance through dominant and recessive genes. In 1865 he published an account of breeding peas on which the whole science of genetics is based.

metal an element which can ionise by electron loss.

metamorphic rock igneous and sedimentary rock that has been changed by heat and pressure.

meteoroids particles of dust and rock fragments frequently derived from comets.

mineral a naturally occurring chemical compound, often crystalline in structure.

mixture different elements and compounds mixed together with no chemical reaction between them.

molecule a group of two or more atoms bonded together.

Mollusca phylum of the animal kingdom. Includes slugs and snails, as well as squids and

octopuses.

Monera (prokaryotae) kingdom. Usually simple, unicellular or colonial, prokaryotic organisms. Cells lack a well-defined nucleus. Includes bacteria and blue-green bacteria (formerly blue-green algae).

moons objects which orbit planets. The Earth’s moon is referred to as the Moon.

mutation a sudden alteration in the genetic information which causes a difference in the appearance of the organisms. Changes which occur only in the body cells affect only the individual concerned. If the change happens in the sex cells then the change is passed on to future generations

natural selection the process by which individuals of the same species compete for limited breeding opportunities and food. Those which are less well suited to the environment do not obtain mates or food and so cannot pass on their genes.

nebulae clouds of interstellar gas, ice and dust.

Nematoda phylum of the animal kingdom. Includes free-living or parasitic roundworms.

neutron particle found inside the nucleus of an atom with no charge and an atomic mass of 1.

nuclear energy energy released when a heavy nucleus splits.

omnivore animal that consumes, and gains energy from, primary producers, as well as other consumers.

organ group of tissues that work together to carry out a particular function.

oscilloscope an instrument which converts sound energy into a visual, graphic display on a screen.

oxide a compound that contains oxygen.

oxygen a gas that comprises approximately 21 per cent of the Earth’s atmosphere. It is vital for life.

pH a hydrogen ion index measuring acidity and alkalinity.

parallel circuit an electric circuit which provides two or more pathways for electricity.

parasite an organism that lives in or on another and which feeds on the other without giving anything in return, often at the expense of the host’s welfare.

pathogens disease-causing micro-organisms including bacteria, viruses, fungi and protoctista.

perihelion the point where a planet is nearest to the Sun.

phases of the Moon how the Moon looks as it orbits the Earth. Viewed from the Earth, the Moon appears to change its shape in a cycle of phases which lasts about one month.

photosynthesis the process by which plants manufacture their own food. Plants use carbon dioxide, water and the energy in sunlight to produce simple sugars like glucose which they can then use during cellular respiration and to produce many of the other substances they need.

pitch the highness or lowness of a sound which is determined by the frequency of the vibrations.

planet large spherical object which orbits the Sun.

Plantae kingdom. Complex, multicellular, eukaryotic organisms. Most cells have cellulose cell walls, chloroplasts and a sap-filled vacuole. All green plants are capable of photosynthesis.

Platyhelminthes phylum of the animal kingdom. Includes free-living flatworms and parasitic tapeworms and flukes.

power energy transferred per second.

predator a carnivore, i.e. an animal that gets its energy from consuming other animals.

pressure when a force acts over a given area, the pressure is a measure of the force on each unit area – measured in newtons per square centimetre or pounds per square inch (as in tyre pressure).

prey the animal food source for predators.

primary consumer animal that consumes, and gains energy from, primary producers, i.e. plants.

primary light source has its own supply of energy and can be seen when there is no other source of light.

primary producer food producer, like green plants, that uses the Sun’s energy to make food, by photosynthesis.

process a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge.

procedural understanding an understanding of the ways in which science works, and the processes and methods used in science. This involves bringing together the skills that will be needed to carry out an investigation with an understanding of the procedures, such as designing appropriate investigations, deciding what measurements to take, how to present and interpret data, and whether or not they are valid.

Prokaryote prokaryotic organisms are composed of prokaryotic cells. Prokaryotic cells have no well-defined nucleus. The genetic material or DNA of prokaryotic cells may cluster or appear dispersed throughout each cell.

Protista kingdom. Usually simple, unicellular, eukaryotic organisms. Cells may appear ‘animal-like’ and ‘plant-like’. Includes the amoeba and the paramecium. Euglena and others are capable of photosynthesis. Algae are currently classified as protoctists.

proton particle found inside the nucleus of an atom with a positive charge and an atomic mass of 1.

pupil a protected hole in the eye through which light travels to the retina.

quality of sound describes the effect of a sound’s many component frequencies. This enables us to tell the difference between a note played by one instrument and the same note played on another instrument.

rarefaction the moving apart of the molecules when vibrations are set up in a gas.

reaction force the force created by a surface as the result of another force acting on it.

recessive in each pair of chromosomes there are genes which code for the same characteristic. If the genes programme for different effect, the one which is not expressed in the characteristic of the organism, e.g. eye colour, is recessive.

reflection an image formed in a reflective surface such as a mirror.

renewable energy energy which comes from the Sun or the motion of the Moon such as winds, solar energy and tides.

resistance a measure of the difficulty electricity has in passing through a conductor.

respiration the oxidation of chemicals which supply energy when broken down. This happens in cells.

retina the internal back wall of the eye containing nerve cells which are sensitive to light.

rusting a chemical reaction that involves oxygen and results in the formation of an oxide.

salt a compound in which all or part of its hydrogen has been replaced by a metal.

saturation a liquid is saturated when it cannot dissolve any more solid.

seasons the cycle of seasons is caused by the tilt of the Earth’s axis relative to the plane of its orbit around the Sun. In the UK, this cycle includes spring, summer, autumn and winter.

secondary consumer animal that consumes, and gains energy from, primary consumers, i.e. herbivore animals.

secondary light source reflects or scatters light from a primary source, e.g. the Moon, a sheet of paper or a wall.

sedimentary rock rock formed from deposits of weathered rock and, sometimes, the hard parts of organisms.

series circuit a circuit where all the components are linked so that electricity has only one pathway through all of them.

shadow the total or partial absence of light.