Final answer:
Euglena acquire nutrients through photosynthesis as photoautotrophs and through phagocytosis or nutrient absorption as heterotrophs, making them mixotrophic organisms capable of adapting their feeding methods to environmental conditions.
Step-by-step explanation:
Euglena, unicellular organisms found in freshwater environments like ponds, have two primary methods of obtaining nutrients. First, they can function as photoautotrophs, conducting photosynthesis by harnessing sunlight to create carbohydrates from carbon dioxide, which are used for both energy and as building blocks for other biomolecules. This process is facilitated by the presence of chloroplasts, which Euglena can shrink and cease to function in the absence of light, hence showing a degree of adaptability.
Secondly, Euglena also have the ability to behave as heterotrophs, obtaining food through either phagocytosis, where they engulf organic material, or by absorbing nutrients directly from their aqueous environment. This versatility in nutrient acquisition is what makes Euglena an example of mixotrophic organisms, as they can switch between a photosynthetic mode and a heterotrophic mode, depending on the conditions.