Organisms exchange substances with their environment — AQA A-Level Biology
In summary: Organisms exchange substances with their environment is a key topic in AQA A-Level Biology. Key exam tip: Use the term 'water potential' correctly when discussing osmosis and tissue fluid formation
Exam Tips for Organisms exchange substances with their environment
- Use the term 'water potential' correctly when discussing osmosis and tissue fluid formation
- When describing gas exchange surfaces, always link the adaptation to Fick's Law (e.g., thin, large surface area, steep concentration gradient)
- Be precise with terminology regarding the cardiac cycle (e.g., distinguish between systole and diastole)
- Ensure diagrams of the heart or gas exchange systems are clearly labelled if requested
- Practice interpreting oxyhaemoglobin dissociation curves and data on cardiac output
Common Mistakes
- Confusing ventilation with gas exchange
- Failing to mention the role of ATP in active transport during absorption
- Incorrectly describing the Bohr effect or the cooperative binding of oxygen to haemoglobin
- Misunderstanding the pressure changes during the cardiac cycle
- Confusing the mechanisms of xylem transport (cohesion-tension) with phloem transport (mass flow)
Marking Points
- Relationship between surface area to volume ratio and metabolic rate
- Adaptations for gas exchange in single-celled organisms, insects, fish, and plants
- Gross structure of the human gas exchange system and ventilation mechanism
- Digestion and absorption of carbohydrates, lipids, and proteins in mammals
- Role of haemoglobin and the oxyhaemoglobin dissociation curve
- Cardiac cycle, pressure/volume changes, and valve movements
- Structure of blood vessels in relation to function
- Formation and return of tissue fluid
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