If it has valves then it is a vein.
Superior vena cava- upper body inferior vena cava
lower body- bother drain into the right atrium
A gateway substance is something that may be menial but could lead to something bigger, an example is weed in the drugs world, weed is not hard to get and is usually a gateway drug to stronger types of drugs and potentially more dangerous
An example of decomposers in the desert could be worms, beetles, or bacteria. Decomposers can't always stay alive because of the drought. Good luck!!
