Structure and function of living organisms
Life processes in animals
Follow food through the alimentary canal and say what each part does, tell breathing from respiration, and match an animal to the way it takes in oxygen.
Chew a mouthful of plain rice for a full minute and something odd happens: it turns sweet. Nothing sweet was added. The starch in the rice is being taken apart into sugar by a juice in your saliva, and that is digestion beginning in your mouth, several hours before the meal reaches the end of its journey.
The canal, end to end
The alimentary canal runs from mouth to anus. Teeth crush and chew; saliva starts on the starch. The food pipe pushes food down in waves. The stomach churns it with digestive juice, acid and mucus. The small intestine — the longest part — receives bile from the liver and juice from the pancreas, finishes the job, and absorbs the nutrients into the blood. The large intestine takes back water and salts, leaving stool, which the rectum stores until it is expelled.
Have a play
The parts of the human respiratory system, from the nostrils down.
Tap any part of the picture.
Worked example
Two test tubes hold boiled rice. Tube A's rice went straight in; tube B's was chewed for a minute first. Iodine is added to both. A goes blue-black; B barely changes. What happened?
Recall what iodine is testing for. Iodine turns blue-black where there is starch.
So the colour is not about the rice as such — it is a report on whether starch is still there.
Try it together
Work out what happens inside your chest as you take one breath in.
Answer each step in a word or two.
1.As you inhale, the dome-shaped muscle below your lungs moves. Does it move upwards or downwards?
Have a go
Have a go on your own. A bird has no teeth, so its food is ground up in a muscular chamber, often with the help of grit it has swallowed. What is that chamber called?
Ready to practise?
Eight questions on what you have just read. Nothing is timed, and you can play as many times as you like.