Question

in biological taxonomy, the traditional linnaean system organizes living organisms into nested ranks—kingdom, phylum, class, order, family, genus, and species—based largely on shared morphological traits. however, this structure can obscure evolutionary relationships when those traits arise through convergent evolution, in which unrelated species develop similar features due to similar environmental pressures. in response, some taxonomists now advocate for cladistics, a method that classifies organisms strictly according to their most recent common ancestor and shared derived characteristics. unlike linnaean ranks, which are fixed, cladograms—tree - like diagrams used in cladistics—allow for reconfiguration as genetic and molecular data reveal new relationships.
1 ▪ mark for review
what is the main purpose of the text?
a it argues that the linnaean system should be updated to better incorporate data from molecular biology.
b it describes how convergent evolution complicates the process of assigning fixed names to species.
c it claims that cladistics is a more accurate and scientifically valid approach than earlier methods.
d it explains how two classification approaches differ in their treatment of similarity and ancestry.

Explanation:

• Option A: The text does not argue for updating the Linnaean system with molecular biology data; it focuses on comparing Linnaean and cladistics approaches. Eliminate A.
• Option B: The text is not about "assigning fixed names to species" but about classification approaches. Convergent evolution is a reason for a new approach, not the main focus of describing naming issues. Eliminate B.
• Option C: The text does not claim cladistics is "more accurate" in a way that’s the main purpose; it explains the differences between the two methods. Eliminate C.
• Option D: The text first explains the Linnaean system (based on morphological traits, fixed ranks) and then cladistics (based on common ancestors, reconfigurable cladograms), highlighting how they differ in treating similarity (morphological vs. derived characteristics/ancestry). This matches the main purpose.

Answer:

D. It explains how two classification approaches differ in their treatment of similarity and ancestry.