No somethings only have one cell. they are called unicellular organisms.
Fungi lacks the ability to produce their own food because they do not have chloroplast which is needed to obtain energy from the sun and convert it into food. Also fungi lack ability to fix nitrogen which has to be incorporated into their food. They also can not fix carbon and utilize it to produce food. Because of these they have to depend on dead organic matters for food.
first, third, fourth, second
