Final answer:
Euglenophyta have a pellicle inside the cell membrane, which is a flexible, protein-based structure that supports and gives shape to the cell. The pellicle allows Euglena to maintain its flexibility and is responsible for the characteristic movement seen in these organisms.
Step-by-step explanation:
Euglenophyta, represented by organisms such as Euglena, have a unique structure inside the cell membrane known as a pellicle. The pellicle is a flexible, protein-based structure that provides support and shape, enabling movement and flexibility that is characteristic of Euglena. While the pellicle functions similarly to a cell wall in providing rigidity, it is not considered a traditional cell wall. Its flexibility is distinct from the more rigid cell walls found in other organisms like plants or certain algae.
Apart from the pellicle, Euglena cells also contain other complex structures such as chloroplasts, which are involved in photosynthesis and are inherited from a green alga via secondary endosymbiosis. This is supported by the presence of double membranes around the chloroplast and a remnant of the green algal nucleus. Euglenoids, such as Euglena, showcase diverse feeding strategies, being autotrophic in the light while switching to heterotrophic in the absence of light, showcasing their mixotrophic nature. This adaptability, coupled with the presence of a red 'eyespot' for light detection and flagella for movement, makes Euglena a fascinating subject of study in biology.