be made up of由…构成、一般是多种构成。如:Water was made up of oxygen and hydrogen.水由氧气和氢构成。
be made of由…制成且材料不发生化学变化、可看出原料的。如Chair is made of wood.椅子是木头做的。
be made up of意思是:由什么组成,比如一个班由50位学生组成
be made of 意思是:由什么制成,比如桌子是用木头制成的
be made of :用…造成(用于原材料显而易见的场合)
而be made up of 就是由...组成