Respiration and Transport in Living Things: Class 7 Study Guide
Cells release energy from food by respiration. Blood and plant vessels carry materials around the body.
Respiration is how living cells release energy from food. In aerobic respiration, glucose reacts with oxygen to give carbon dioxide, water and energy. Breathing is the way oxygen enters the body and carbon dioxide leaves. At rest, a person breathes about 15 to 18 times a minute, and more during exercise.
Anaerobic respiration happens without oxygen. Yeast makes alcohol and carbon dioxide this way. Our muscles make lactic acid during hard exercise, which can cause cramps.
Blood and circulation
Blood carries oxygen, food and waste. It has plasma, red cells (with haemoglobin, which carries oxygen), white cells (which fight germs) and platelets (which help clotting). The heart pumps it. Arteries carry blood away from the heart and veins bring it back.
| Part | Job |
|---|---|
| Heart | Pumps blood |
| Arteries | Carry blood away from the heart |
| Veins | Carry blood to the heart |
| Red cells | Carry oxygen |
| White cells | Fight germs |
Excretion and plants
Excretion removes waste. The kidneys filter blood and make urine, which contains urea. In plants, roots absorb water, and the xylem carries it up to the leaves. Water evaporates from the leaves by transpiration, which pulls more water up. The phloem carries food made in the leaves to other parts.
Through root hairs.
To the leaves.
Transpiration.
To the whole plant.
Healthy habits
Exercise makes the heart and lungs stronger. Not smoking protects the lungs. Drinking water helps the kidneys. Eating iron-rich food keeps blood healthy.
Worked examples and common mistakes
Example: Which cells carry oxygen? Red blood cells. Example: Which tube carries water in a plant? Xylem. Common mistakes: mixing up breathing and respiration (breathing is bringing air in and out, respiration releases energy in cells), and thinking that all veins carry oxygen-poor blood without exception.
Check your understanding: model answers
1. It carries oxygen in red blood cells. 2. Phloem. 3. Carbon dioxide or water.
✨ Key Takeaways
- Respiration releases energy from food in cells.
- Blood carries oxygen and waste.
- Xylem carries water up in a plant.
- Kidneys remove waste from blood.
💬 Questions for Discussion & Reflection
- What is the job of haemoglobin?
- Which tube carries food in a plant?
- Name one waste product of aerobic respiration.
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