Question

Secondary growth is present in angiosperm eudicots and present in gymnosperms, but secondary growth is absent in angiosperm monocots.

1. Hypothesize: is secondary growth an example of a synapomorphy or convergent evolution?

2. What DNA evidence would support your hypothesis?  Assume you can look at the DNA of a “secondary growth gene” in all three taxa.

Answer 1

A) This is the case of convergent evolution. Because the trait is not found in all three taxa but it is found in two taxa out of three taxa. This suggests the paraphyletic mode of phylogeny. In this case, the trait is found in the gymnosperm and angiosperm's eudicto because cambium is present in them. But monocot don't have cambium.

B) When the DNA of these three taxa are isolated for this secondary growth gene, then it is found that the similarity in the sequence of nucleotides are found to be more in between eudicot and gymnosperm as compared to the monocots.