What evidence suggests that the first tetrapods were amphibians?

Which beat describes the brain stem

Do you think the gene eef1 alpha1 supports cell theory? explain your response.

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?