Why not? The desert is one of the harshest environments in the world so organisms that survive there are adapted in some extraordinary ways. We could have studied this topic in depth in either of our other field trips as all organisms, from single-celled bacteria to complex human organisms are adapted to environmental conditions.
Learn how organisms attempt to maintain their internal environment when the external environment is at odds with their needs. Place various organisms in different environments and learn what happens when they are placed in environments for which are adapted, and for which they are not adapted.
Learn how plants and animals are adapted to exploit free water, use it efficiently, survive water loss, store water, deal with heat, protect themselves and have developed reproduction strategies; all to improve their chances of survival.