Which of the following groups are currently accepted as belonging on a phylogenetic tree of all known organisms?Blank 1 Question 1[select: , Eukaryotes, Bacteria, and Archaea, Eukaryotes, Prokaryotes, and Archaea, Eukaryotes, Bacteria, and Fungi, Bacteria, Archaea, and Fungi] Based on recent genome sequence analysis, it has been argued that there should only be two groups. What would these groups be?Blank 2 Question 1[select: , Eukaryotes and Archaea, Eukaryotes and Prokaryotes, Bacteria and Archaea, Eukaryotes and Bacteria]Multiple dropdown selections
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Which of the following groups are currently accepted as belonging on a phylogenetic tree of all known organisms?Blank 1 Question 1[select: , Eukaryotes, Bacteria, and Archaea, Eukaryotes, Prokaryotes, and Archaea, Eukaryotes, Bacteria, and Fungi, Bacteria, Archaea, and Fungi] Based on recent genome sequence analysis, it has been argued that there should only be two groups. What would these groups be?Blank 2 Question 1[select: , Eukaryotes and Archaea, Eukaryotes and Prokaryotes, Bacteria and Archaea, Eukaryotes and Bacteria]Multiple dropdown selections

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BlackTom AI · Accepted Answer

The three-domain system recognizes Eukaryotes, Bacteria, and Archaea as the primary lineages of cellular life, so Blank 1 = Eukaryotes, Bacteria, and Archaea. Modern genome analyses arguing for two major groups treat Eukaryotes as emerging from within the Archaea, so Blank 2 = Bacteria and Archaea.

1. Relevant knowledge points
- Domain-level classification groups organisms into monophyletic lineages (descended from a single common ancestor).
- Carl Woese’s rRNA analyses established three domains: Bacteria, Archaea, Eukarya (Eukaryotes).
- Phylogenomics and discovery of Asgard archaea show many eukaryotic signature genes are archaeal in origin; mitochondria derive from a bacterial endosymbiont.

2. Step-by-step reasoning
- Step 1: Early molecular phylogenies (rRNA) showed three deep branches: Bacteria, Archaea, Eukaryotes → that is why current textbooks list three domains.
- Step 2: Whole-genome comparisons reveal eukaryotic informational genes (replication, transcription, translation components) are most closely related to archaeal homologs, while many metabolic genes are bacterial (from the mitochondrial ancestor).
- Step 3: The discovery of Asgard archaea whose genomes contain numerous "eukaryotic-like" genes implies eukaryotes arose from within the archaeal radiation.
- Step 4: If eukaryotes are nested inside Archaea, then the deepest split is between Bacteria and the Archaea (which include eukaryotes), giving a two-domain view: Bacteria vs Archaea.

3. Calculations
- None required.

4. Why the correct answers are correct
- “Eukaryotes, Bacteria, and Archaea” reflects the widely accepted three-domain classification based on rRNA. “Bacteria and Archaea” reflects the genomic evidence that collapses Eukaryotes into Archaea, yielding two primary groups.

5. Why other options are incorrect (brief)
- “Prokaryotes” is paraphyletic (not a single clade). “Fungi” are a subset of Eukaryotes, not a separate primary domain. Pairings that exclude Bacteria or wrongly separate Eukaryotes from their archaeal relatives are inconsistent with phylogenomic data.

Conclusion: Blank 1 = Eukaryotes, Bacteria, and Archaea; Blank 2 = Bacteria and Archaea, matching the provided answers.

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