An example of an organism that cannot maintain homeostasis through internal changes is the sea star (or starfish). Sea stars are considered poikilothermic animals, meaning their internal body temperature and physiological processes are heavily influenced by the external environment. They can't regulate their body temperature internally, so their metabolic rate and activities depend largely on the surrounding water temperature.
Instead of internal mechanisms to maintain homeostasis, sea stars rely on behavioral adaptations, such as moving to different depths or locations within the ocean to find suitable temperatures. When the environmental conditions are outside their tolerance range, they may experience stress or lethargy, demonstrating their inability to maintain homeostasis purely through internal physiological changes.