What is the most likely reason the bones of the reptiles were found on more than one continent

What amino acid is coded for by this sequence after the mutation

Which nucleotide component contains nitrogen

Ivan is looking at a cross section of a stem taken from a vascular plant. he sees two different types of vascular tissue: the xylem, which is closer to the center of the stem, and the phloem, located around the xylem, closer to the outside of the stem. how do these two structures work together in a living plant?