Sample 1Medium
A graph plots the size of a growing organ (y-axis) against time (x-axis). It is an S-shaped curve: growth is slow in an initial phase P, becomes very rapid in phase Q, and levels off in phase R. Which statement about phase Q is correct?
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The answer is D.
An S-shaped (sigmoid) growth curve has a lag phase, a log or exponential phase and a stationary phase. In the exponential phase both daughter cells keep dividing, and growth follows W1 = W0e^(rt).
- A.
The slow initial phase P is the lag phase. Q is the phase of rapid growth.
- B.
The stationary phase is R, where growth levels off as nutrients run short.
- C.
Arithmetic growth gives a straight line. The steep rise in an S-shaped curve is geometric (exponential) growth.
NCERT: Class 11 Biology, Chapter 13