Diatoms and euglenoids are described as which of the following?

• A. Multicellular, heterotrophic
• B. Unicellular, photosynthetic autotrophs that reproduce asexually and are found in aquatic environments
• C. Saprotrophic decomposers
• D. Autotrophic but non-photosynthetic

Answer: (B)

The idea being tested is how these protists obtain food, how many cells they’re made of, and where they’re typically found. Diatoms and euglenoids are mainly unicellular organisms that perform photosynthesis to make their own food, so they’re autotrophs. They inhabit aquatic environments where light is available for photosynthesis. They reproduce primarily by asexual cell division, which is common in these groups, though some diatoms can also engage in sexual reproduction to restore cell size. This combination—unicellular structure, photosynthetic nutrition, and presence in water—fits the description as unicellular, photosynthetic autotrophs found in aquatic environments. The other options describe organisms that are multicellular or heterotrophic, saprotrophic decomposers, or autotrophic but non-photosynthetic, which doesn’t align with diatoms and euglenoids.