Phylogeny Practice Test

A word-described phylogeny for four plant species is: (A,B) form a clade; that clade is sister to C; the clade containing A, B, and C is sister to D. No timing information is given. Based on this branching pattern, which statement is best supported?

A biologist compares five vertebrate taxa using shared derived traits relative to a jawless fish outgroup. All five taxa have jaws. Only taxa M, N, and O have a bony skeleton. Only taxa N and O have four limbs. Only taxon O has an amniotic egg. Assume each derived trait evolved once and was not lost. Which pair of taxa shares the most recent common ancestor?