Jobs that never stop

The idea

The processes that together perform an organism's maintenance job, which must go on even at rest or asleep, are life processes; they include nutrition, respiration, transport of materials and excretion.

Fast asleep

It is midnight and you are fast asleep. You are not running, writing or chatting.

Which jobs is your body still doing?

• All its maintenance jobs: it keeps working
• None. The body switches off
• Only breathing

Switch off, switch on

Change the state of the body. See which things switch off. Then put it to sleep and tap all four jobs.

Four jobs that go on

The maintenance job of the body must go on even when we are not doing anything, even when we are asleep. The processes that together do this job are life processes: nutrition, respiration, transport of materials and excretion.

Running, writing and chatting are things we do. Life processes are what the body does for itself.

• Life process | What it does
• Nutrition | Takes food, the energy source, from outside to inside
• Respiration | Uses oxygen to break the food down
• Transport | Carries food, oxygen and wastes round the body
• Excretion | Removes harmful wastes

Notes

The processes that together perform an organism's maintenance job, which must go on even at rest or asleep, are life processes; they include nutrition, respiration, transport of materials and excretion.

Check yourself

Raju is asleep. His kidneys are still removing wastes from his blood. Which life process is this?

Life processes go on …

Which of these is not a life process?

Which life process carries food and oxygen from where they enter the body to every part?

• Excretion — correct. Yes! Removing harmful wastes is excretion.
• Respiration. Respiration uses oxygen to break food down. Removing wastes is excretion.
• Nutrition. Nutrition brings food in from outside the body.
• only when we are active. If they stopped when we rested, the body would start to break down.
• even when we sit still or sleep — correct. Yes! The maintenance job cannot stop.
• only in the daytime. They go on day and night.
• Respiration. Respiration is a life process.
• Transport of materials. Transport of materials is a life process.
• Playing football — correct. Yes! It is something we choose to do. Life processes go on without it.
• Transport of materials — correct. Yes! Food and oxygen are taken up in one place, but every part needs them.
• Excretion. Excretion removes harmful wastes.
• Nutrition. Nutrition only brings the food in. Carrying it round is transport.