Question

A scientist discovers a new species near coral reefs in australia. on basic microscopic examination and after conducting a few simple experiments, he finds that this single-celled species is photosynthetic (using sunlight for energy), has a rigid cell wall structure with no peptidoglycan, uses a flagellum for motion, and contains a variety of internal structures that are bound by plasma membranes. given this information, this new species is most likely a ______ cell in the _____ subcategory.

Answer 1

Only bacterial and plant cells have rigid cell walls.
The lack of peptidoglycan in the cell wall tells us that it's not a bacterial cell, so this organism is most likely a single-celled plant. This is further confirmed by the fact that the organism is capable of doing photosynthesis. 
Since the cell has various internal structures, aka organelles, we can conclude that it is a eukaryotic cell. All the single-celled eukaryotic organisms are classified in the subgroup Protista.
So, this newly found organism is a eukaryotic cell in the Protista subcategory.