Answer:
Both Pleurococcus and Chlorella are Unicellular algae i. e. made of one cell. Chlorella is a type of green algae which grows in colonial form. There are thousands of cells present in colonial form, each cell perform a particular function. For example, some cells are responsible for movement, some for reproduction etc. The jobs are distributed between these cells. But in Unicellular, one cell perform all functions of life.