# Explain how the adaptations of a desert rodent, such as the kangaroo rat (Dipodomys), allow it to maintain water balance without access to liquid water.

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

## Mark scheme (4 marks)

1. Metabolic (oxidative) water produced during aerobic respiration of carbohydrates/fats provides the rodent's primary water source
2. The kidneys produce highly concentrated urine, reducing urinary water loss
3. Dry faeces / minimal water loss in excretion because water is reabsorbed in the large intestine / colon
4. Behavioural/anatomical adaptation reduces evaporative water loss — e.g. nocturnal activity avoids daytime heat, or nasal countercurrent heat exchange condenses water vapour before exhalation

## Related

- [Revision notes for IB DP Biology Higher 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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