* Why do mammals have two ears? Ask a child to sit blindfolded in the centre of a large circle of pupils. Point to one in the circle who should clap: the child in the middle must then indicate the source of the sound.
Next, use an earplug to plug an ear of the pupil in the middle and repeat the process. Pupils will soon realise that it is easier to track sound with two ears than one.
* Show the children pictures of mammals with their ears pricked up. Can they link the size and position of the ears with the kind of life the animal leads?
* Ask the children to listen to themselves speak when their hands are cupped over their ears. This shows how the ear flap or pinna collects sound.
* Prove that sound waves are vibrations. Flick a ruler against a table; pluck a stretched elastic band; put dried peas on a loudspeaker cone and increase the volume till peas begin to bounce; light a candle in front of a speaker and play loud music with a strong bass that makes the flame flicker; hold a vibrating tuning fork just beneath the surface of water to make the water splash.