Practice question

Despite immense morphological diversity, protists share essential eukaryotic cellular organization: nucleus bounded by double membrane with nuclear pores, mitochondria or reduced mitosomes, 80S ribosomes, and cytoskeletal elements. Molecular phylogeny based on SSU rRNA places them within domain Eukarya alongside plants, fungi, and animals. Former kingdom Protista is now recognized as paraphyletic grades distributed across multiple supergroups SAR, Archaeplastida, Amoebozoa, and Excavata, but domain assignment remains Eukarya. Bacteria and Archaea domains contain only prokaryotes lacking nuclear envelope. Thus ribosomal signatures define protists as eukaryotes, not separate domain named Protista.