Autotrophs include all the following EXCEPT

Step 1: Analyze the question We need the one organism that is NOT an autotroph.

Step 2: Concept Autotrophs make their own food from simple inorganic substances.

• Photoautotrophs use light energy (photosynthesis): green plants, algae, diatoms, phytoplankton, cyanobacteria.
• Chemoautotrophs use energy from chemical reactions (chemosynthesis): e.g., nitrifying bacteria, sulfur bacteria.

Heterotrophs cannot make their own food and must feed on other organisms.

Step 3: Check each option

• A. Chemosynthetic bacteria: They make food using energy from inorganic chemical reactions, so they are autotrophs.
• B. Diatoms: These are photosynthetic algae with chlorophyll, so they are autotrophs.
• C. Green plants: They photosynthesize, so they are autotrophs.
• D. Phytoplankton: These are microscopic photosynthetic organisms (the "plant" plankton), so they are autotrophs.
• E. Zooplankton: These are tiny animals (the "animal" plankton) that feed on phytoplankton and other organisms, so they are heterotrophs.

Step 4: Answer Zooplankton is the only heterotroph in the list, so it is the exception.

Tip: Remember the prefixes: phyto = plant (makes food), zoo = animal (eats food). Whenever you see "zoo-" in a question about feeding, think consumer, not producer.