Transport in AnimalsEdexcel GCSE Biology: Revision notes
Section 1
Why Organisms Need Transport
Must transport: oxygen, carbon dioxide, water, dissolved food, mineral ions, urea.
Key termsureaaerobic respiration
Section 2
Exchange Surfaces and Surface Area to Volume Ratio
As organisms grow, surface area to volume ratio decreases, so diffusion alone is too slow — need exchange surfaces + transport system.
Key termssurface area to volume ratioexchange surface
Example
2cm cube: SA=24cm², vol=8cm³, ratio=3:1. 4cm cube: SA=96cm², vol=64cm³, ratio=1.5:1.
Section 3
The Blood
| Component | Function |
|---|---|
| Red blood cells | Carry oxygen (haemoglobin, no nucleus, biconcave) |
| Phagocytes | Engulf pathogens |
| Lymphocytes | Produce antibodies |
| Plasma | Transports dissolved substances/heat |
| Platelets | Blood clotting |
Key termshaemoglobinphagocytelymphocyteplateletplasma
Common mistake
Phagocytes engulf; lymphocytes make antibodies — don't mix up.
Section 4
Blood Vessels
| Vessel | Structure | Function |
|---|---|---|
| Artery | Thick muscular, narrow lumen | High pressure, away from heart |
| Vein | Thin wall, wide lumen, valves | Low pressure, to heart |
| Capillary | One cell thick | Exchange with tissues |
Key termsarteryveincapillaryvalvelumen
Must Know
- Transport substances: O2, CO2, water, food, ions, urea.
- Larger organisms have smaller SA:vol ratio, need transport systems.
- Red blood cells (no nucleus, biconcave), phagocytes, lymphocytes, plasma, platelets.
- Arteries thick/muscular; veins have valves; capillaries one cell thick.
That's the notes covered.
Carry on to the next subtopic.