An early system grouped microorganisms P, Q, R and S together because they were small and had similar shapes.
Scientists obtain new evidence. Chemical types I and II are two distinct sets of molecular features. Reference samples show that type I identifies Archaea and type II identifies Bacteria.
| Organism | Nucleus | Chemical type |
|---|---|---|
| P | Absent | I |
| Q | Absent | II |
| R | Present | Neither |
| S | Absent | I |
Consider every possible pair of different organisms. Compare grouping by nucleus presence alone with grouping into the three domains.
How many pairs share a group in each system, and which pair remains grouped together in the three-domain system?
Pairs decrease from 3 to 1; P and S remain together.
Pairs decrease from 3 to 2; P and Q remain together.
Pairs decrease from 6 to 1; P and S remain together.
Pairs decrease from 6 to 2; P and Q remain together.
40 exam-style questions on AQA GCSE Biology 6.4 Classification of living organisms, covering 6.4 Classification of living organisms. Each one has a worked solution and a mark scheme showing where the marks go.