(i) It is the graphic representation of the total growth against time.
(ii) The period of time in which growth takes place has been called grand period of growthby sachs.
(iii) The rate of growth is not uniform during grand period of growth.
(iv) If total growth is plotted against time a S-shaped or sigmoid curve is obtained. It consists
of four parts, i.e., lag phase, exponential phase (log phase), phase of diminishing growth and stationary phase.