Which neurotransmitter has not been linked to depression? acetylcholine dopamine norepinephrine?

Describe the primary and secondary immune response in terms of speed and number of antibodies produced?

Apart of an ecosystem that can restrict the growth of a population is referred to as

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?