Archaea: Different Membranes, Extreme Habitats, Separate Domain · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

The third domain of life

Science · Microbiology · ages 18-19
Name ______________________   Date ____________
  1. Archaeal chains are branched. Bacterial chains are what?

    • Ring sugars
    • Straight fatty acids
    • Short proteins
  2. Which links do archaeal membrane lipids use?

    • Ester links
    • Glycerol free links
    • Ether links
  3. Ribosomal RNA places archaea closer to eukaryotes than to bacteria.

    Circle one:   True   False

  4. Which grouping rests on genetic relatedness, not habitat?

    • Two empires of microbes
    • Three domains of life
    • Five kingdoms of cells
  5. Why do archaeal membranes survive boiling springs?

    • They are twice as thick as ours
    • They contain no lipids at all
    • Ether bonds resist breaking and branched chains pack tight
  6. A new microbe thrives in acid. Can you call it an archaeon?

    • Yes, acid means archaeon
    • Only if it is large
    • No, bacteria live in acid too
  7. Which pair are both archaea?

    • Methanogens and halophiles
    • Soil bacteria and skin bacteria
    • Two kinds of cyanobacteria
  8. Which archaeal machinery is closer to ours than to bacteria?

    • Photosynthesis
    • Transcription and translation
    • Nitrogen fixing
LightMySky · lightmysky.comW1-mt_isKmuoGgAn-s1

Answer key

For grown-ups. Fold this page away before handing over the rest.

The third domain of life W1-mt_isKmuoGgAn-s1

  1. Straight fatty acids · Bacterial lipids use ester links to straight fatty acids.
  2. Ether links · Archaeal lipids use ether links to branched chains.
  3. True · That gene branch is what earned archaea their own domain.
  4. Three domains of life · Bacteria, Archaea, and Eukarya are grouped by genes.
  5. Ether bonds resist breaking and branched chains pack tight · Each chemical difference adds stability under heat, salt, and acid.
  6. No, bacteria live in acid too · Many extremophiles are bacteria, so habitat alone never decides.
  7. Methanogens and halophiles · Methanogens and halophiles are both archaeal groups.
  8. Transcription and translation · Their transcription and translation machinery matches eukaryotes best.
Worksheet · LightMySky