Question

A phylogenetic tree based on rRNA sequence comparisons show that the three domains of life are:

1) Bacteria, Archaea, and Eucarya
2) Bacteria, Plantae, and Eukarya.
3) Archaea, Eucarya, and Fungi.
4) Archaea, Eukarya, and Cyanobacteria.

Answer 1

The correct answer to the student's question is 1) Bacteria, Archaea, and Eukarya. These three domains constitute the primary branches in the tree of life as defined by rRNA sequence comparisons, with the Eukarya sharing a closer ancestor with Archaea.

Step-by-step explanation:

The three domains of life based on rRNA sequence comparisons are Bacteria, Archaea, and Eukarya. This classification system was proposed by microbiologist Carl Woese, using data obtained from sequencing ribosomal RNA genes. According to this phylogenetic tree, Eukarya share a more recent common ancestor with Archaea than with Bacteria. The domain Eukarya includes organisms like plants, animals, fungi, and protists, which all contain a nucleus within their cells. In contrast, Bacteria and Archaea are classified as prokaryotes, which lack internal cell organelles such as a nucleus.

This more recent form of classification supersedes the older five-kingdom system which divided life into animals, plants, fungi, protists, and prokaryotes. Woese's phylogenetic tree suggests that the vast array of life, from simple bacteria to complex multicellular organisms, all derived from common ancestors and can be organized into these three overarching domains.