Gambierdiscus toxicus belongs to which group?

• A. Virus
• B. Bacteria
• C. Dinoflagellate algae
• D. Fungi

Answer: (C)

This organism is a dinoflagellate, a photosynthetic protist that is typically grouped with algae. Dinoflagellates are single-celled marine organisms that form part of the phytoplankton and often have two flagella and a theca of plates, enabling them to photosynthesize and inhabit the ocean's upper layers. That combination of being photosynthetic and unicellular places Gambierdiscus toxicus squarely with dinoflagellate algae.

It isn’t a virus, which are acellular particles that need a host to replicate. It isn’t bacteria, which are prokaryotic, non-nucleus-containing cells with different basic cell structure. It isn’t fungi, which are eukaryotic organisms as well but typically non-photosynthetic and have different cell wall composition. The defining feature here is its photosynthetic, dinoflagellate nature, so the best fit is dinoflagellate algae.