(a) What are unicellular organisms? Name two unicellular organisms.
(b) What are multicellular organisms? Name two multicellular organisms.

a) When all the vital functions which are necessary for life are performed by a single cell then such organisms with a single cell is called the unicellular organism. Some examples of unicellular organisms are amoeba, paramecium etc.

b) Multicellular organisms are the organisms which are made from a large number of cells or which are made from multiple numbers of cells.
Humans and plants are examples of multicellular organisms.