A cactus plant and a water lily are examples of plants adapted to very different environments. Compare the features of the waxy cuticle and stomata in a xerophyte and a hydrophyte, and explain how each feature is suited to the plant's environment.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Xerophytes such as cacti have a thick waxy cuticle, whereas hydrophytes such as water lilies have a thin or absent cuticle.
The thick cuticle in xerophytes reduces water loss from the leaf surface.
Xerophytes possess fewer stomata, often sunken into the leaf, while hydrophytes have many stomata on the upper leaf surface.
The reduced number and sunken position of stomata in xerophytes minimise water vapour loss; the numerous, exposed stomata in hydrophytes allow water vapour to diffuse out easily, which is acceptable in a water‑rich environment.
The thick cuticle in xerophytes reduces water loss from the leaf surface.
Xerophytes possess fewer stomata, often sunken into the leaf, while hydrophytes have many stomata on the upper leaf surface.
The reduced number and sunken position of stomata in xerophytes minimise water vapour loss; the numerous, exposed stomata in hydrophytes allow water vapour to diffuse out easily, which is acceptable in a water‑rich environment.
Examiner tips
- Use the exact terms ‘thick waxy cuticle’, ‘thin or no cuticle’, ‘fewer/sunken stomata’, ‘many/open stomata’.
- Show the link between each feature and the environment (water loss vs. water‑rich).
- Keep the answer to four clear points to match the 4 marks.
Common mistakes
- Confusing the location of stomata (upper vs. lower surface).
- Over‑generalising the cuticle thickness for all xerophytes.
Mark scheme (4 marks)
- Xerophytes have a thick waxy cuticle whereas hydrophytes have a thin or no waxy cuticle
- The thick waxy cuticle in xerophytes prevents / reduces water loss (from the leaf surface)
- Xerophytes have fewer stomata (which may be sunken) whereas hydrophytes have a large number of stomata positioned on the upper surface of the leaf
- Fewer / sunken stomata in xerophytes reduces water vapour loss; many / open stomata in hydrophytes allows water vapour to diffuse out easily (promoting water loss)
Key terms in this question
xerophyte · hydrophyte · waxy cuticle · stomata
Related
- All Cambridge International IGCSE Biology (0610) revision notes →
- How to answer a "Compare" question →
- Decode the mark scheme abbreviations →
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