IB DP Biology Mock Exam HL Paper 2 Set 4 - 2025 Syllabus
IB DP Biology Mock Exam HL Paper 2 Set 4
Prepare for the IB DP Biology Exam with our comprehensive IB DP Biology Exam Mock Exam HL Paper 2 Set 4. Test your knowledge and understanding of key concepts with challenging questions covering all essential topics. Identify areas for improvement and boost your confidence for the real exam
▶️ Answer/Explanation
(a)
• Upper epidermis: This outer layer is transparent so light can pass through to deeper tissues. It also protects the leaf and, together with the waxy cuticle (not shown), helps limit water loss.
• Palisade mesophyll: These tall, tightly packed cells contain many chloroplasts and are the main site of photosynthesis, capturing light efficiently to produce organic molecules.
(b)
Any two of the following:
1. Spongy mesophyll and air spaces: The loosely arranged cells create large internal air spaces that allow rapid diffusion of gases such as \(\text{CO}_2\) and \(\text{O}_2\) between stomata and photosynthetic cells.
2. Stomata: These small pores, usually located in the lower epidermis, permit gases to move in and out of the leaf.
3. Guard cells: These specialized cells flank each stoma and regulate its opening and closing, balancing gas exchange against water conservation.
(c)
• Xylem: Carries water and dissolved minerals from the roots to the leaf for photosynthesis and transpiration.
• Phloem: Transports sugars produced during photosynthesis to other parts of the plant where they are used or stored.