Final answer:
Euglena's eyespot senses light, directing the organism towards it, which is crucial for photosynthesis in the chloroplasts. The chloroplasts, containing chlorophyll, allow Euglena to produce energy through photosynthesis when light is available, while in darkness, Euglena can absorb nutrients heterotrophically.
Step-by-step explanation:
The eyespot and chloroplasts in Euglena work together in a unique manner to support the survival of these organisms. The eyespot, a primitive ocular organ, helps the Euglena detect light, guiding its movement towards light sources. This is essential for photosynthesis, which occurs within the chloroplasts that contain chlorophyll. The chlorophyll captures light energy and uses it to convert carbon dioxide into carbohydrates through the process of photosynthesis.
During photosynthesis, these carbohydrates serve as an energy source for the Euglena, thereby allowing it to sustain itself when light is available. In the absence of light, however, the chloroplasts shrink and become temporarily non-functional. During these times, Euglena can switch to a heterotrophic mode of nutrition, absorbing organic nutrients from their environment or ingesting them by phagocytosis. This dual capability of acting both as an autotroph and a heterotroph, termed mixotrophy, gives Euglena a significant survival advantage in varying environmental conditions.