Biology 9700/02 May June 2002 | Cambridge AS Level Past Papers With Mark Scheme

1. Seaweed life cycle: DNA replication before mitosis ensures genetic consistency; meiosis generates haploid gametes to maintain chromosome number across generations.

2. Catalase experiment: oxygen volume plateaus when substrate depletes; high-temperature catalase pre-treatment causes denaturation, reducing enzymatic activity.

3. T cell receptors: membrane fluid mosaic structure enabling receptor diversity; protein folding creates specific binding sites for antigens, ensuring specificity.

4. Cardiac cycle: phase depicts ventricular contraction, blood flow regulated by atrioventricular and semilunar valves; arterial pressure maintained by elastic recoil preventing complete pressure drop.

5. Drug effects: tolerance from reduced receptor sensitivity; alcohol misuse leads to liver fibrosis, cirrhosis, and disrupted metabolic functions over time.

6. Nitrogen cycle: nitrification, nitrogen fixation, and ammonification processes support soil fertility; crop rotation with legumes minimizes chemical fertilizer dependency.