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Quizzes > Science

Which Domain Is Unicellular? Extremophile Prokaryotes Quiz

Quick, free quiz on domains with autotrophs and heterotrophs. Instant results.

Editorial: Review CompletedCreated By: Adam Fitzsimmons AcousticUpdated Aug 23, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art showing unicellular organisms autotroph heterotroph icons on coral background for Domains and Kingdoms quiz

This quiz helps you identify which domain is unicellular, place extremophile prokaryotes, and compare autotrophs and heterotrophs across the three domains, with quick questions to prepare for class or review before a test. Build on it with the bacteria and archaea quiz, try the label prokaryotic and eukaryotic cells, and review cell specialization in prokaryotes.

Which domain includes unicellular prokaryotic organisms with cell walls made of peptidoglycan?
Bacteria
Eukarya
Archaea
Protista
Bacteria are unicellular prokaryotes whose cell walls contain peptidoglycan, a polymer not found in Archaea. Archaea have different cell wall compositions, and Eukarya have membrane-bound nuclei and typically lack peptidoglycan entirely. Protista is an outdated grouping of various eukaryotic microorganisms.
Which domain includes organisms that can thrive in extreme environments such as hot springs and salt lakes?
Bacteria
Fungi
Archaea
Eukarya
Archaea include extremophiles that can survive in high temperature, high salinity, and acidic conditions. Bacteria exist in many environments but generally not at extreme extremes where Archaea dominate. Eukarya and Fungi have a membrane-bound nucleus and are not specialized for the most extreme habitats.
Which domain includes unicellular organisms that have membrane-bound nuclei and organelles?
Eukarya
Bacteria
Archaea
Virus
Eukarya consists of organisms whose cells contain a true nucleus and organelles such as mitochondria and chloroplasts. Bacteria and Archaea lack membrane-bound nuclei and are classified as prokaryotes. Viruses are not cells and do not belong to any of the three domains.
Which domain contains multicellular autotrophs such as plants and unicellular algae?
Bacteria
Eukarya
Archaea
Protista
Eukarya includes multicellular autotrophs such as plants, as well as numerous unicellular algae. Bacteria include some autotrophs but lack multicellularity in the plant sense. Archaea are prokaryotic and usually not photosynthetic in the same way. 'Protista' is an informal grouping within Eukarya often used for unicellular eukaryotes.
Which domain includes many autotrophic organisms that perform oxygenic photosynthesis?
Archaea
Fungi
Eukarya
Bacteria
Many bacteria, notably cyanobacteria, carry out oxygenic photosynthesis, producing oxygen as a byproduct. Archaea do not perform oxygenic photosynthesis, though some are phototrophic. Eukarya include plants and algae that do photosynthesize, but the domain most known for unicellular oxygenic phototrophs is Bacteria.
Carl Woese proposed the three-domain system based on differences in which genetic marker?
mRNA
16S rRNA
18S rRNA
tRNA
Woese used comparisons of 16S ribosomal RNA sequences to reveal fundamental differences among Bacteria, Archaea, and Eukarya. The 16S rRNA gene is highly conserved and ideal for assessing evolutionary relationships in prokaryotes. The 18S rRNA is the eukaryotic equivalent.
Which domain includes methanogens that produce methane as a metabolic byproduct?
Bacteria
Archaea
Eukarya
Viruses
Methanogens are a group of Archaea that generate methane during anaerobic metabolism. No bacteria or eukaryotes produce methane as a primary metabolic byproduct under normal conditions. Viruses lack metabolic processes altogether.
According to molecular studies, which domain is the closest relative to Eukarya?
Protista
Viruses
Bacteria
Archaea
Genomic analyses indicate that Eukarya share a more recent common ancestor with Archaea than with Bacteria. Many components of the eukaryotic transcription and translation machinery resemble those of Archaea. Protista is not a domain but an informal grouping within Eukarya.
Which domain's cell membranes contain ether-linked lipids rather than ester-linked lipids?
Archaea
Eukarya
Bacteria
Fungi
Archaeal membranes are unique in having ether linkages between glycerol and hydrophobic chains, which confer stability under extreme conditions. Bacteria and Eukarya have ester-linked lipids in their membranes. Fungi are eukaryotes and follow the standard ester linkage.
Which group of unicellular eukaryotic organisms is considered polyphyletic and falls under the domain Eukarya?
Viruses
Bacteria
Archaea
Protists
Protists comprise a diverse array of unicellular eukaryotes that do not form a single coherent clade, making them polyphyletic. They include algae, protozoa, and slime molds. Bacteria and Archaea are separate prokaryotic domains, and viruses are non-cellular.
Which domain's ribosomal RNA sequences are most distinct from those of Bacteria?
Protista
Archaea
Viruses
Eukarya
Archaeal 16S rRNA sequences differ significantly from bacterial sequences, which is why Woese distinguished Bacteria and Archaea as separate domains. Eukaryotic 18S rRNA is also distinct but the rRNA comparison foundational to the three-domain system focused on prokaryotic lineages.
According to endosymbiotic theory, mitochondria originated from which domain?
Bacteria
Archaea
Eukarya
Viruses
Mitochondria are believed to have originated from an ancestral alpha-proteobacterium through endosymbiosis with an early eukaryotic host. This places the origin of mitochondria within the Bacteria domain. Archaea served as the host lineage.
Which domain's organisms have cell walls composed of pseudomurein instead of peptidoglycan?
Bacteria
Archaea
Fungi
Eukarya
Certain Archaea, such as methanogens, have cell walls made of pseudomurein, a polymer similar to peptidoglycan but with distinct chemical bonds. Peptidoglycan is unique to Bacteria. Eukaryotes and Fungi do not use either polymer for their cell walls.
Which domain's transcription and translation mechanisms are more similar to those of Eukarya?
Viruses
Protista
Archaea
Bacteria
Archaeal RNA polymerases and ribosomal proteins closely resemble those found in Eukarya, and many transcription factors are homologous. Bacterial transcription and translation systems are structurally and mechanistically distinct. Protista refers to eukaryotes and viruses lack independent translation systems.
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Study Outcomes

  1. Identify Domain of Unicellular Organisms -

    Analyze defining traits of each domain to accurately identify which domain includes unicellular organisms.

  2. Determine Nutritional Diversity Across Domains -

    Differentiate autotrophs and heterotrophs to decide which of the domains include both nutritional types.

  3. Apply Model 3 Domains and Kingdoms Answers -

    Use model scenarios to correctly classify organisms within the three domains and their kingdoms.

  4. Reinforce Classification via Quiz -

    Engage with domains and kingdoms quiz questions to solidify your understanding of biological taxonomy.

  5. Interpret Classification Criteria -

    Evaluate key characteristics in domains and kingdoms questions to enhance your taxonomy skills.

Cheat Sheet

  1. Three-Domain System Overview -

    The three-domain system, proposed by Woese et al., splits life into Bacteria, Archaea, and Eukarya based on 16S rRNA differences. This framework directly addresses which domain includes unicellular organisms, grouping Bacteria and Archaea as exclusively single-celled. Try the mnemonic "BAB: Bacteria, Archaea, Bio-world" to lock it in.

  2. Unicellular vs. Multicellular Distribution -

    Both Bacteria and Archaea are inhabited solely by unicellular species like Escherichia coli and Sulfolobus, while Eukarya contains mostly multicellular animals and plants alongside unicellular protists such as Amoeba. Remember that "Eukaryotes Aren't All Uni" (EAUA) to flag that Eukarya is a mix. These distinctions help cement domain features in line with university-level microbiology outlines.

  3. Autotrophs and Heterotrophs Across Domains -

    Learning which of the domains include both autotrophs and heterotrophs is key: Archaea and Bacteria host chemoautotrophs and photoautotrophs as well as heterotrophs, whereas Eukarya splits into photosynthetic plants and heterotrophic animals. This highlights metabolic diversity in all three domains per primary literature from the American Society for Microbiology. Use the comparison chart method to visualize energy pathways across domains and kingdoms.

  4. Model 3 Domains and Kingdoms Answers Mnemonic -

    For model 3 domains and kingdoms answers, a handy trick is the phrase "Big Cats Eat Really Well": Bacteria, C (for Cell-based Archaea), Eukarya, remember "Cells Rule Wisely." This fun mnemonic captures domain names and reminds you to contrast kingdom-level traits like cell walls and membrane lipids. Practice reciting it aloud to boost recall during taxonomy questions.

  5. Effective Domains and Kingdoms Quiz Prep -

    When tackling domains and kingdoms quiz questions, create flashcards focused on characteristic features (e.g., peptidoglycan cell walls in Bacteria). Test yourself on "domains and kingdoms questions" from reputable sources like the Smithsonian or university portfolios to gain confidence. Reviewing past quiz sets reduces anxiety and reinforces domain-level classification skills.

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