[Campbell Biology P.618] The note in Figure 26.21 defines a 'polytomy' as a branch point lea... | Practice Question

The note in Figure 26.21 defines a 'polytomy' as a branch point leading to multiple lineages, representing an unresolved pattern of divergence. Considering the broader discussion on horizontal gene transfer in the text, how does the concept of polytomy relate to the challenges in reconstructing the tree of life?

  • A: Polytomies indicate that all phylogenetic trees must always be dichotomously branching to be accurate.
  • B: Polytomies represent instances where horizontal gene transfer has definitively occurred, creating new distinct lineages.
  • C: Polytomies highlight areas where gene transfer between unrelated organisms has made it difficult to resolve evolutionary relationships using a simple branching model.
  • D: Polytomies are exclusively found at the common ancestor of all life, reflecting the earliest, most complex gene transfers.

Explanation

The text explains that phylogenetic trees are based on vertical gene transmission, but horizontal gene transfer HGT leads to inconsistent results when different genes are used to build trees. Polytomies represent these unresolved patterns of divergence, indicating where the traditional dichotomous branching model struggles to represent complex evolutionary relationships due to events like HGT.