# Explain how the adaptations of a named xerophyte allow it to reduce water loss in an arid environment.

> IB DP Biology Standard Level (2023 syllabus) — B4.1 Adaptation to environment · Explain · 4 marks

## Mark scheme (4 marks)

1. Named xerophyte correctly identified (e.g. cactus / Opuntia, marram grass / Ammophila, euphorbia, agave, Welwitschia)
2. Stomata are sunken in pits / rolled leaves (marram grass) or reduced in number, limiting water vapour diffusion out of the leaf by trapping humid air near the stomatal opening
3. Thick waxy cuticle on the epidermis reduces evaporation of water directly through the leaf/stem surface (cuticular transpiration)
4. Leaves are modified into spines (cacti) / leaves are reduced in surface area, so the stem carries out photosynthesis, greatly reducing the total surface area available for transpiration

## Key terms

- [xerophyte](https://www.gradenine.co.uk/glossary/xerophyte)

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-adaptations-of-a-e2891b92) · Published by Druglandscape Ltd.