Final answer:
Euglenas are mixotrophic, capable of both photosynthesis and heterotrophic feeding. They ingest or absorb nutrients when light is unavailable, with some species lacking chloroplasts and being entirely heterotrophic.
Step-by-step explanation:
The statement that summarizes the heterotrophic activities of euglenas is that they are capable of acquiring material by ingestion (phagocytosis) or by absorption of solutes from their aquatic environment. Some forms of Euglena lack chloroplasts and are entirely heterotrophic, feeding on other smaller cells. Euglenas are unique in that they can switch between autotrophic and heterotrophic modes of nutrition, depending on the availability of sunlight and nutrients. When there is sufficient sunlight, euglenas can perform photosynthesis using their chloroplasts to produce energy. However, in the absence of light or when organic nutrients are readily available, euglenas become heterotrophs. They then absorb nutrients from the environment or take up organic material directly, exhibiting their mixotrophic nature and contributing to their role as both primary producers and decomposers in their ecosystems.