Chapter 5 · Biology
Life Processes: Chapter Introduction
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Even at rest your body keeps working: repair and maintenance need energy all the time. The four life processes: nutrition, respiration, transportation and excretion.
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Key points
- Even when we rest, maintenance (repair, upkeep) goes on, so the body needs energy all the time.
- Nutrition: taking in food. Green plants make it (photosynthesis: autotrophs); we take it in (heterotrophs).
- Respiration: breaking down food to release energy, mostly with oxygen, in the mitochondria.
- Transportation carries food, oxygen and wastes (blood pumped by the heart); excretion removes harmful wastes (kidneys).
The four life processes
| Process | What it does | Example in humans |
|---|---|---|
| Nutrition | Takes in food (source of energy and materials) | Eating and digestion |
| Respiration | Releases energy from food | Glucose + O₂ → CO₂ + H₂O + energy (in mitochondria) |
| Transportation | Moves materials to every cell | Blood pumped by the heart |
| Excretion | Removes harmful metabolic wastes | Kidneys make urine |
Autotrophs and heterotrophs
- Autotrophs make their own food from simple substances (green plants, by photosynthesis).
- Heterotrophs depend on food made by others (animals, fungi, most bacteria).
Quick quiz
3 questions. Choose an answer for each, then submit to see your score and the explanations.