Are Diagrams Important?
 

AOA,

Is drawing diagram, for example in questions like, functions of different areas of the brain necessary? What if I make a water melon and label it to appear like brain? Any experiences?

If it is unavoidable, what to use for the diagram? Pen (or ballpoint) or Pencil?

its not necessary to sketch diagram of every question you are being asked for. however, if you draw it, will give you an above grade than those who could not draw it. for instance, you can draw the diagram of kidney when you are asked to write the functions of kidney. similarly, draw the diagram of brain for functions of brain. yes, you can roughly draw a diagram similar to a balloon and label it correctly. diagrams are inevitable in general ability and pure science subjects that is zoology, by doing so, you would score good
regards