Organisms are classified as Excavata based on __________.

• A. the presence of a cell wall made of cellulose
• B. the ability to form spores during reproduction
• C. having chloroplasts with three membranes
• D. the presence of a feeding groove on one side of the cell body

Answer: (D)

Verified step by step guidance

1. Understand the classification of Excavata: Excavata is a major group of protists characterized by unique structural features, particularly related to their feeding mechanisms.
2. Identify the key feature of Excavata: Organisms in this group are distinguished by the presence of a feeding groove on one side of their cell body, which is used for ingesting food particles.
3. Eliminate incorrect options: Review the provided options and rule out features that are not specific to Excavata. For example, a cell wall made of cellulose is characteristic of plants and some algae, not Excavata. The ability to form spores is more common in fungi and some protists, but not a defining feature of Excavata. Chloroplasts with three membranes are found in some photosynthetic protists, but this is not a universal trait of Excavata.
4. Focus on the correct feature: The defining characteristic of Excavata is the feeding groove, which is a structural adaptation for feeding and is unique to this group.
5. Conclude the reasoning: Based on the above analysis, the correct answer is 'the presence of a feeding groove on one side of the cell body,' as this is the key feature that classifies organisms as Excavata.