DP Biology (first assessment 2025)

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Question 22M.2.SL.TZ2.c

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Date May 2022 Marks available [Maximum mark: 4] Reference code 22M.2.SL.TZ2.c
Level SL Paper 2 Time zone TZ2
Command term Describe Question number c Adapted from N/A
c.
[Maximum mark: 4]
22M.2.SL.TZ2.c

Describe adaptations in mammals living in desert ecosystems to maintain osmolarity in their bodies.

[4]

Markscheme
  1. behavioural adaptations to avoid over-heating / hiding in burrows/out of sun during hot period of day / active at cooler times of the day/nocturnal animals / panting;
  2. adaptations for heat exchange such as large ears;
  3. may have longer loop of Henle (to reabsorb more water);
  4. may produce more ADH (according to osmotic concentrations of the blood) / produce concentrated urine / lower volume of urine;
  5. camel humps that store fat that releases (metabolic) water when broken down;
  6. reduced sweat;
  7. any other valid adaptation; (e.g., light coloured coats)
Examiners report

Long loops of Henle was the most common desert adaptation discussed. There were common misconceptions about camels’ humps being water storage organs rather than the production of metabolic water.

Syllabus sections