CELL is an well defined basic structural and functional unit of a living thing which can function independently.The term cell is derived from the word CELLULA means " small room." The living part of a cell is PROTOPLASM.

CELL THEORY

German scientist M Schleiden,Theodor Schaann and Rudolf Virchow ,proposed the cell theory.the cell theory states 

1) All organisms are made up of one or more cells.

2)A cell carries out all the life activities of an organism.

3)A new cell arises only from other living cells by the process of cell division.

CELL SHAPE

Cells are of various shapes.Generally,in unicellular organism,have a fixed shape.

1)Ameoba a unicellular organism is irregular in shape.

DIAGRAM OF AMEOBA

2)Paramoecium is slippered shape.

DIAGRAM OF PARAMOECIUM

3)Muscle cell are elongated.they can alter there shape by contracting and relaxing.

DIAGRAM OF MUSCLE CELLS