Biology 9700/05 May June 2002 | Cambridge AS Level Past Papers With Mark Scheme

1. Leaf structure analysis: Plan drawing of K1, focusing on tissue distribution in the lamina; high-power drawing highlighting palisade mesophyll cell features such as chloroplasts.

2. Xerophytic adaptations in K2:
- Thick cuticle for reduced water loss.
- Sunken stomata to trap moist air.
- Rolled leaves reducing exposed surface area.
- Dense spongy mesophyll minimizing transpiration.
- Disadvantage: lower photosynthetic efficiency due to limited gas exchange.

3. Photosynthesis experiment:
- Setup: pondweed in water with a graduated capillary tube for gas collection; light source distance adjusted to vary intensity.
- Usage: measure bubble count or gas volume at fixed intervals for different light distances.
- Control variables: temperature, CO\\(_2\\) concentration, and pondweed type/health.

4. Light intensity relationship:
- Gas production increases with light intensity following the inverse square law.
- Saturation point reached where light is no longer a limiting factor, with other factors (e.g., CO\\(_2\\)) becoming limiting.