What do a carnivorous dinoflagellate, a parasitic apicomplexan, and a ciliate have in common?

• A. All three are heterotrophic and autotrophic.
• B. All three form colonies of cells.
• C. All three are parasitic on other species of organisms.
• D. All three are photosynthetic.
• E. All three have sacs known as alveoli just beneath their plasma membranes.

Answer: (E)

Verified step by step guidance

1. Understand the context: The question is asking about the common characteristics of three different types of protists: carnivorous dinoflagellates, parasitic apicomplexans, and ciliates.
2. Identify the key feature: The question provides several options, but the correct answer is that all three have sacs known as alveoli just beneath their plasma membranes.
3. Explain the concept of alveoli: Alveoli in this context are small, membrane-bound cavities found in certain protists, which are part of the group known as Alveolata. These structures are thought to provide structural support and may play a role in osmoregulation.
4. Differentiate from other options: The other options provided (heterotrophic and autotrophic, forming colonies, parasitic, photosynthetic) do not apply to all three groups. For example, not all ciliates are photosynthetic, and not all apicomplexans form colonies.
5. Conclude with the significance: Recognizing the presence of alveoli helps in classifying these organisms within the Alveolata group, highlighting a shared evolutionary trait despite their diverse lifestyles.